{"gene":"CYP24A1","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2000,"finding":"Human CYP24A1 (expressed in E. coli reconstituted system with adrenodoxin and adrenodoxin reductase) catalyzes both C-23 and C-24 hydroxylation pathways on 25(OH)D3 and 1α,25(OH)2D3, performing all sequential oxidative steps from substrate through lactol to lactone (C-23 pathway) and through 24-oxo intermediates to tetranor product (C-24 pathway), whereas rat CYP24A1 shows almost no C-23 hydroxylation—demonstrating that a single human enzyme executes the complete multi-step catabolism via dual pathways.","method":"Recombinant E. coli expression with adrenodoxin/adrenodoxin reductase reconstitution; HPLC and mass spectrometric metabolite identification","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with full metabolite identification by HPLC-MS; replicated in whole-cell E. coli coexpression system in the same study","pmids":["11012668"],"is_preprint":false},{"year":2004,"finding":"Phenylalanine-249 (F249) in the F-helix of rat CYP24A1 is critical for substrate binding and catalytic site alignment: mutagenesis to F249T (hydrophobic→polar) dramatically lowers substrate-binding affinity and abolishes the final C-23 oxidation step; F249A and F249Y mutations additionally impair C-24 oxidation of 1,24,25-(OH)3D3. The 1α- and 25-hydroxyl groups on vitamin D metabolites are the major determinants for high-affinity binding (Kd ~0.05–0.06 µM), and turnover is higher for 25(OH)D3 than for 1,25(OH)2D3.","method":"Recombinant CYP24A1 purification from E. coli; substrate-induced spectral binding assays (Kd); kinetic analysis (Km, Vmax); site-directed mutagenesis at F249","journal":"Archives of biochemistry and biophysics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and kinetic characterization in a single rigorous study","pmids":["15111121"],"is_preprint":false},{"year":1995,"finding":"CYP24 hydroxylates at C-24 and C-23 regardless of side-chain length extension (by 1–3 carbons), indicating that CYP24's hydroxylation site selection is determined by the distance of C-24 from the vitamin D ring structure, not by the distance from the end of the side chain (contrast with CYP27 which tracks from the terminus).","method":"Cultured and transfected cell models expressing CYP24 or CYP27; HPLC and GC-MS metabolite identification of homologated vitamin D substrates","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based enzyme assay with series of synthetic substrates and HPLC-GC/MS identification; single lab but multiple substrates and orthogonal methods","pmids":["7622489"],"is_preprint":false},{"year":2002,"finding":"1,25-dihydroxyvitamin D3 (1,25D) induces CYP24 promoter activity through a Ras-dependent mechanism engaging two distinct MAP kinase modules: ERK1/ERK2 phosphorylates RXRα at Ser260, and ERK5 phosphorylates Ets-1 at Thr38; both phosphorylation events are required for full induction. The Ets-1 binding site cooperates with the proximal vitamin D response element in a hormone-dependent manner. p38 and JNK MAP kinases are not required.","method":"CYP24 promoter-luciferase transfection; dominant-negative mutants of ERK1 (K71R), MEK5(A), Ras17N; site-directed mutagenesis of Ets-1 (T38A) and RXRα (S260A); co-immunoprecipitation of RXRα with ERK2 and Ets-1 with ERK5; phosphorylation assays with activated kinases","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (dominant-negative mutants, site-directed mutagenesis of phosphorylation sites, Co-IP, kinase assays) in a single focused mechanistic study","pmids":["12048211"],"is_preprint":false},{"year":2005,"finding":"Pregnane X receptor (PXR) transactivates the human CYP24 promoter by binding to the two proximal vitamin D-responsive elements (VDREs) located between −326 and −142, thereby inducing CYP24 mRNA and 24-hydroxylase enzyme activity in human hepatocytes in response to rifampicin and hyperforin. This provides a molecular mechanism for drug-induced osteomalacia.","method":"CYP24 promoter-luciferase reporter assay in HEK cells; transfection of PXR; RT-PCR for CYP24 mRNA in human hepatocytes; 24-hydroxylase enzyme activity assay; in vivo PCN/dexamethasone treatment of mice; plasma 24,25-(OH)2D3 measurement","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (reporter assay, co-transfection, mRNA, enzyme activity, in vivo) in a single study by one lab","pmids":["15630458"],"is_preprint":false},{"year":2006,"finding":"Steroid and xenobiotic receptor (SXR/PXR) does NOT induce CYP24 expression in vitro or in vivo, does not transactivate the CYP24 promoter, and instead inhibits VDR-mediated CYP24 promoter activity. 1,25(OH)2D3-induced CYP24 expression is enhanced in mice lacking PXR. Rifampicin had no effect on intestinal CYP24 expression in humans. This contradicts the earlier PXR-induction report (PMID:15630458).","method":"CYP24 promoter-luciferase assay; in vitro and in vivo SXR/PXR agonist treatment; PXR-knockout mouse studies; human intestinal biopsies post-rifampicin","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (reporter, KO mouse, human biopsy) contradicting prior study; single lab; conflicting with PMID:15630458 so confidence reduced","pmids":["16691293"],"is_preprint":false},{"year":2005,"finding":"Genistein (50–100 nM) directly inhibits CYP24A1 enzyme activity in a noncompetitive manner in isolated mitochondrial preparations from DU145 cells, thereby increasing the half-life of 1,25(OH)2D3 and enhancing VDR up-regulation and antiproliferative signaling.","method":"CYP24 enzyme activity assay in isolated mitochondrial preparations; kinetic (noncompetitive inhibition) analysis; VDR mRNA/protein measurement; cell growth assay","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct enzyme activity assay on isolated mitochondria with kinetic characterization; single lab, two orthogonal methods","pmids":["15955619"],"is_preprint":false},{"year":2009,"finding":"miR-125b post-transcriptionally regulates CYP24A1 protein levels by binding a recognition element (MRE125b) in the 3'-UTR of CYP24 mRNA: transfection of antisense oligonucleotide for miR-125b increases endogenous CYP24 protein in KGN cells, while precursor miR-125b decreases it in MCF-7 cells. Decreased miR-125b in breast cancer tissues inversely correlates with increased CYP24 protein levels.","method":"3'-UTR luciferase reporter assay; antisense oligonucleotide and precursor miRNA transfection; Western blot for endogenous CYP24 protein; immunohistochemistry of breast cancer tissues","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (reporter assay with gain/loss of function, endogenous protein change, tissue validation) providing strong mechanistic evidence in a single focused study","pmids":["19570947"],"is_preprint":false},{"year":2011,"finding":"Loss-of-function mutations in CYP24A1 (encoding 25-hydroxyvitamin D3 24-hydroxylase) cause idiopathic infantile hypercalcemia via complete loss of vitamin D catabolism. Functional characterization in a mammalian expression system confirmed complete loss of enzymatic function for all identified recessive mutations.","method":"Candidate-gene sequencing; mammalian expression system functional assay of mutant CYP24A1 enzyme activity","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — combined genetic identification and functional expression characterization; multiple mutations independently confirmed; replicated across two patient cohorts","pmids":["21675912"],"is_preprint":false},{"year":2011,"finding":"The mouse Cyp24a1 gene is controlled by both promoter-proximal VDR binding sites (~−160 and −265 nt from TSS) and novel downstream-distal intergenic enhancers (+35 and +37 kb) that together mediate 1,25(OH)2D3-dependent transcriptional up-regulation. C/EBPβ occupancy at a site −345 nt upstream is markedly increased following 1,25(OH)2D3 treatment.","method":"ChIP-chip and ChIP-seq in cell lines and mouse tissues; luciferase reporter assays; in vivo mouse chromatin analysis","journal":"Archives of biochemistry and biophysics","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased ChIP-seq to identify enhancers, confirmed in vivo in mice; multiple orthogonal methods","pmids":["22179019"],"is_preprint":false},{"year":2019,"finding":"Kidney-specific Cyp24a1 expression requires a downstream enhancer cluster (C24-DS1) that contains PTH-sensitive pCREB-binding sites: deletion of C24-DS1 in mice eliminates basal renal Cyp24a1 expression and completely abolishes FGF23 and PTH regulation of Cyp24a1, while 1,25(OH)2D3 induction remains unaffected. A second downstream cluster (C24-DS2) containing VDR-binding sites is required for full Cyp24a1 responses in non-renal target cells.","method":"ChIP-Seq in mouse tissues; clustered enhancer deletion mouse models; RNA analysis of Cyp24a1 expression in kidney and non-renal tissues; hormone challenge (PTH, FGF23, 1,25(OH)2D3)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP-Seq plus in vivo genetic deletion of specific enhancer elements with rigorous phenotypic readout; multiple deletion strains and hormone challenges","pmids":["31439663"],"is_preprint":false},{"year":2019,"finding":"Cyp24a1 enhancers in the kidney control circulating 1,25(OH)2D3 levels: deletion of both M1 and M21 Cyp27b1 submodules (in adjacent genes) reduces Cyp27b1 expression, which secondarily reduces Cyp24a1 expression due to compensatory regulation by elevated PTH and reduced FGF23, demonstrating reciprocal PTH/FGF23-mediated homeostatic control of both enzymes in the kidney.","method":"In vivo enhancer deletion mouse models; hormone measurements (PTH, FGF23, calcium, phosphate); RNA analysis; dietary normalization rescue experiments","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic deletion with rescue experiments and multi-parameter hormonal and molecular readouts","pmids":["31629064"],"is_preprint":false},{"year":2022,"finding":"PTH rapidly increases recruitment of phosphorylated CREB (pCREB), CBP, and CRTC2 to kidney-specific enhancers near Cyp27b1, while dismissing CBP from distal Cyp24a1 enhancers to suppress Cyp24a1 transcription. Salt-inducible kinase (SIK) inhibition rapidly recruits CRTC2 to Cyp27b1 enhancers, mimicking PTH action on both Cyp27b1 and Cyp24a1. 1,25(OH)2D3 suppression of Cyp27b1 is associated with reduced CBP recruitment at CREB-module enhancers.","method":"In vivo ChIP-seq in mouse kidney after PTH, FGF23, 1,25(OH)2D3 and SIK inhibitor (YKL-05-099, SK-124) treatments; pCREB, CBP, CRTC2 occupancy analysis; RNA analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo ChIP-seq with multiple hormonal and pharmacological perturbations; mechanistically defines coactivator dynamics at specific Cyp24a1 enhancers","pmids":["36183832"],"is_preprint":false},{"year":2024,"finding":"Mutation of the promoter-proximal (PRO) VDREs in mice dramatically reduces VDR occupancy and impairs 1,25(OH)2D3-induced kidney Cyp24a1 expression and nearly eliminates intestinal induction. FGF23 induction of Cyp24a1 is reduced but not eliminated and retains synergy with 1,25(OH)2D3. PTH suppression of Cyp24a1 is unchanged by PRO VDRE mutation. VDR recruitment across downstream (DS) enhancers is also dramatically reduced, revealing cooperative interaction between PRO and DS enhancers.","method":"In vivo VDRE mutagenesis in mice; ChIP-seq for VDR and pCREB occupancy; RNA analysis after 1,25(OH)2D3, FGF23, and PTH treatment","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo mutagenesis with ChIP-seq and multiple hormonal challenge experiments; defines cooperative enhancer mechanism","pmids":["39363152"],"is_preprint":false},{"year":2007,"finding":"The upstream CYP24 promoter region (−548 to −294 nt, containing three potential Sp1 sites) acts synergistically with the two proximal VDREs to amplify vitamin D-induced CYP24 expression. The VDREs alone are insufficient to account for the full magnitude of induction (~20,000-fold) observed in human fibroblasts.","method":"Serial deletion reporter constructs (−1918 to +209 nt) assayed by luciferase reporter assay in cultured human fibroblasts","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic promoter deletion analysis with clear functional readout; single lab, single method type","pmids":["17475215"],"is_preprint":false},{"year":2005,"finding":"1,25D induction of the CYP24 promoter in HEK-293T cells requires JNK (but not ERK1/2) and a novel vitamin D stimulatory element (VSE) at −171/−163, ~30 bp upstream of VDRE-1. Synergistic up-regulation by PMA + 1,25D additionally requires ERK1/2 activation (potentiated by 1,25D), JNK, and the Ets-1 binding site.","method":"CYP24 promoter-luciferase reporter assays; dominant-negative ERK1(K71R) transfection; site-directed mutagenesis of VSE; kinase inhibitors; HEK-293T cell system","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay with dominant-negative mutants and site-directed mutagenesis; single lab, multiple methods","pmids":["15836435"],"is_preprint":false},{"year":2010,"finding":"Human CYP24 promoter-proximal region spanning −470 to −392 nt is required for 1,25D-mediated induction in human cells; the vitamin D stimulatory element (VSE) present in the rat promoter is absent in the human CYP24A1 promoter, indicating species-specific differences in the transcriptional mechanism.","method":"Electrophoretic mobility shift assay (EMSA); dual-luciferase reporter assay with human and rat CYP24A1 promoter deletion constructs","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA plus reporter assay with deletion constructs; single lab, two complementary methods","pmids":["20450955"],"is_preprint":false},{"year":2010,"finding":"The number of functional VDR binding sites (VDREs) differs between normal (MCF-10A, one VDRE) and malignant (MCF-7, three VDREs) mammary cells, producing linear vs. stepwise CYP24 mRNA accumulation respectively. Distal VDREs in MCF-7 regulate CYP24 transcription via ligand-dependent, dynamic chromatin looping that brings distal elements cyclically adjacent to the transcription start site. CYP24 mRNA is also three times more stable in MCF-7 than MCF-10A cells.","method":"Quantitative ChIP; chromosome conformation capture (3C); expression profiling; mRNA stability assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP, 3C, and mRNA stability assays providing mechanistic insight from multiple orthogonal approaches; single lab","pmids":["20460683"],"is_preprint":false},{"year":2010,"finding":"Unliganded VDR represses basal CYP24 transcription in breast cancer cells: VDR overexpression decreases CYP24 mRNA and promoter activity, siRNA knockdown of VDR increases CYP24 mRNA, and a FokI-FF polymorphic VDR (3 amino acids shorter in AF-1 domain) fails to repress CYP24 promoter activity, indicating AF-1 domain integrity is required for repression.","method":"VDR overexpression and siRNA knockdown in MCF-7 and MDA-MB231 cells; CYP24 promoter-luciferase assay; RT-PCR; VDR nuclear localization by immunofluorescence","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cell lines with gain- and loss-of-function; mutagenesis of AF-1 domain; single lab","pmids":["20440542"],"is_preprint":false},{"year":2014,"finding":"Inflammatory conditioned medium (from activated macrophages) induces IRES-dependent translation of CYP24A1 via an internal ribosome entry site (IRES) in the 5'-UTR of cyp24a1 mRNA. This IRES-mediated translation is sensitive to PI3K inhibition and is sufficient to be activated by constitutively active Akt.","method":"Polysome profiling and microarray analysis; bicistronic reporter assay for IRES activity; PI3K inhibitor treatment; constitutively active Akt transfection","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — bicistronic reporter validates IRES function; polysome profiling confirms translational regulation; pharmacological and genetic manipulation of PI3K/Akt pathway; multiple orthogonal methods","pmids":["24416388"],"is_preprint":false},{"year":2021,"finding":"CYP24A1 is responsible for sequential multi-step conversion of 25(OH)D3 to 23,25,26-(OH)3D3 via 23,25-(OH)2D3; subsequent conversion of 23,25,26-(OH)3D3 to 25(OH)D3-26,23-lactone requires an additional enzyme identified as CYP3A (not CYP24A1). Cyp24a1 KO rats show ~2-fold higher plasma 25(OH)D3 and complete absence of the five major 25(OH)D3 metabolites found in wild-type rats.","method":"CRISPR/Cas9-generated Cyp24a1 knockout rats; oral 25(OH)D3 administration followed by plasma metabolite profiling; synthetic substrate administration to KO rats; recombinant human CYP species enzyme assay; ketoconazole inhibition studies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic KO model combined with in vitro reconstitution with recombinant CYP species and pharmacological inhibition; multiple orthogonal methods to define pathway steps","pmids":["33865853"],"is_preprint":false},{"year":2015,"finding":"Both rat and human CYP24A1 metabolize 20S-hydroxyvitamin D3 [20(OH)D3] to dihydroxyvitamin D3 species (primarily at C24 for rat, C25 for human CYP24A1). 20,23(OH)2D3 undergoes multiple oxidations including C23-C24 bond cleavage by CYP24A1, analogous to catabolism of 1,25(OH)2D3. Catalytic efficiencies for 20(OH)D3 and 20,23(OH)2D3 are lower than for 1,25(OH)2D3.","method":"In vitro enzyme assay with recombinant rat and human CYP24A1; NMR and high-resolution mass spectrometry for metabolite identification; kinetic analysis","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with NMR and HRMS structural identification of products; rigorous kinetic characterization; single lab","pmids":["25727742"],"is_preprint":false},{"year":2013,"finding":"Protein kinase CK2 contributes to 1,25D3-mediated CYP24A1 promoter induction in prostate cancer cells: CK2 inhibitor TBBz inhibits 1,25D3-induced CYP24A1 promoter activity and mRNA; siRNA knockdown of CK2 reduces 1,25D3-induced CYP24A1 mRNA expression.","method":"Stable CYP24A1 promoter-luciferase reporter PC3 cell line; TBBz (CK2 inhibitor) treatment; siRNA CK2 knockdown; RT-PCR; in vitro and in vivo xenograft antiproliferative assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter reporter plus siRNA knockdown; single lab, two orthogonal methods","pmids":["23358686"],"is_preprint":false},{"year":2010,"finding":"CYP24 promoter is epigenetically silenced by hypermethylation of CpG islands at the 5' end in tumor-derived endothelial cells (TDEC) but not in normal tissue or Matrigel-derived endothelial cells. Treatment with a DNA methyltransferase inhibitor restores 1,25(OH)2D3-induced CYP24 expression and restores calcitriol resistance in TDEC.","method":"Isolation and culture of fresh tumor-derived endothelial cells; CpG methylation analysis; DNA methyltransferase inhibitor treatment; CYP24 expression analysis; calcitriol responsiveness assays","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct methylation analysis combined with functional rescue by demethylation; single lab","pmids":["20304059"],"is_preprint":false},{"year":2016,"finding":"Progesterone receptor (PR)-dependent signaling inhibits calcitriol-induced CYP24A1 expression: co-treatment with progesterone (P4) markedly suppresses CYP24A1 mRNA and protein in PR-expressing but not PR-negative cell lines. Mouse ovaries show significant reduction in calcitriol-induced Cyp24a1 mRNA and protein in response to P4. This extends calcitriol activity and enhances apoptosis.","method":"RT-PCR and Western blot for CYP24A1 in multiple cell lines (PR+ and PR−); PR isoform-expressing T47D cells; calcitriol + progesterone co-treatment; in vivo mouse ovary experiments; TUNEL apoptosis assay","journal":"Gynecologic oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cell lines with PR+/PR- controls and in vivo mouse validation; single lab","pmids":["27106018"],"is_preprint":false},{"year":2018,"finding":"5α-dihydrotestosterone (DHT) suppresses renal Cyp24a1 expression via inhibition of progesterone receptor (Pgr): DHT suppresses Pgr expression, and Pgr normally drives Cyp24a1 transcription by binding to a progesterone receptor-binding site in the Cyp24a1 promoter. DHT treatment increases blood 25(OH)D3 levels.","method":"Orchidectomized mouse model; DHT treatment; RT-PCR and Western blot for Pgr and Cyp24a1; promoter binding site analysis; ER+ and ER− cell line analysis; blood 25(OH)D3 measurement","journal":"Journal of molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mouse model plus cell-based mechanistic analysis; single lab, multiple readouts","pmids":["29382742"],"is_preprint":false},{"year":2023,"finding":"LSH (lymphoid-specific helicase, a chromatin-remodeling protein) binds to the CYP24A1 promoter, promotes nucleosome eviction, and reduces H3K27me3 occupancy to activate CYP24A1 transcription. USP11 stabilizes LSH via deubiquitination; erastin disrupts USP11-LSH interaction, leading to LSH ubiquitination and degradation, which reduces CYP24A1 expression, increases intracellular Ca2+ influx, and sensitizes colorectal cancer cells to ferroptosis.","method":"Co-immunoprecipitation (USP11-LSH interaction); ChIP for LSH, H3K27me3 at CYP24A1 promoter; siRNA knockdown; ubiquitination assay; calcium measurement; lipid peroxidation assay; erastin-induced ferroptosis assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ChIP, and functional cell-based assays; single lab with multiple orthogonal methods","pmids":["37414755"],"is_preprint":false},{"year":2010,"finding":"Valproic acid (VPA) potentiates VDR-mediated induction of CYP24 mRNA and promoter activity in human hepatocytes and HEK293 cells by activating ERK signaling (not solely through HDAC1 inhibition, since trichostatin A did not replicate VPA's effect on CYP24 mRNA).","method":"RT-PCR for CYP24 mRNA in human hepatocytes and HEK293; CYP24 promoter-luciferase reporter assay; trichostatin A comparison; ERK, JNK, p38 activation measurement","journal":"Toxicology letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay plus mRNA in primary human hepatocytes with mechanistic distinction by TSA comparison and kinase analysis; single lab","pmids":["21115105"],"is_preprint":false},{"year":2019,"finding":"Mammary-specific conditional knockout of Cyp24a1 in mice reduces terminal end bud number, ductal outgrowth, and branching during puberty and alveologenesis during early pregnancy by inhibiting proliferation (but not apoptosis) of basal and luminal mammary epithelial cells, demonstrating that CYP24A1 activity modulates local 1,25(OH)2D availability and is required for normal mammary gland development.","method":"Conditional Cyp24a1 knockout in mammary epithelium; whole-mount mammary gland analysis; proliferation/apoptosis markers; in vitro sensitivity to 1,25(OH)2D3 in isolated MECs","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific conditional KO with defined proliferation phenotype and in vitro mechanistic follow-up; single lab, multiple orthogonal methods","pmids":["30654105"],"is_preprint":false},{"year":2021,"finding":"SQLE (squalene epoxidase) promotes colorectal cancer proliferation through accumulation of calcitriol, which stimulates CYP24A1 expression; elevated CYP24A1 in turn reduces intracellular Ca2+ and activates MAPK signaling to drive proliferation. SQLE inhibition reduces calcitriol and CYP24A1 levels, increases intracellular Ca2+, and suppresses MAPK and cell growth.","method":"RNA sequencing; transcriptome and untargeted metabolomics; Western blotting and RT-PCR for CYP24A1 and MAPK pathway; SQLE siRNA knockdown; organoid and xenograft tumor models; SQLE inhibitor (terbinafine) treatment","journal":"Cancer communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — integrated transcriptomics, metabolomics, and in vivo xenograft with pathway manipulation; single lab","pmids":["34268906"],"is_preprint":false},{"year":2016,"finding":"Loss of Cyp24 in Hyp mice (FGF23-excess model of X-linked hypophosphatemic rickets) and FGF23R176Q transgenic mice results in near-complete recovery of rachitic/osteomalacic bone abnormalities. Treatment with CYP24 inhibitor CTA102 also ameliorates rachitic bones in both models, linking CYP24 activity to the pathophysiology of FGF23-dependent phosphate-wasting states.","method":"Cyp24-null mouse crossed with Hyp and FGF23R176Q transgenic mice; bone histomorphometry; CYP24 inhibitor CTA102 pharmacological treatment; serum biochemistry","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic cross of KO onto disease models plus pharmacological inhibition, both yielding consistent rescue of bone phenotype; replicated in two disease models","pmids":["26784541"],"is_preprint":false},{"year":2014,"finding":"In human monocyte-derived dendritic cells (DCs), 1,25(OH)2D3 stimulation up-regulates CYP24A1, which curtails the functional effects of vitamin D in DCs (but not macrophages), limiting autocrine vitamin D activity. DCs also express a truncated CYP27B1 transcript that reduces activation of 25(OH)D to 1,25(OH)2D.","method":"Monocyte-derived DC and macrophage cultures; RT-PCR for CYP24A1 and CYP27B1 isoforms; 25(OH)D to 1,25(OH)2D conversion assay; VDR-responsive gene expression; DC maturation and T-cell response assays","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — primary human cell comparisons with functional vitamin D responsiveness assays; single lab, multiple methods","pmids":["24643654"],"is_preprint":false},{"year":2021,"finding":"CYP24A1 localizes to the annulus of human spermatozoa (co-localizing with VDR in ~80% of spermatozoa from young men), and its expression at this subcellular site correlates positively with sperm count, concentration, motility, and morphology. 1,25(OH)2D3 increases intracellular Ca2+ and motility in young men with CYP24A1-expressing sperm but not in subfertile men lacking the protein.","method":"Immunocytochemistry (ICC) for CYP24A1 and VDR in human spermatozoa; double ICC co-localization; intracellular Ca2+ measurement; sperm motility assay","journal":"International journal of andrology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization with functional correlation; single lab; no genetic manipulation to establish causality","pmids":["22404291"],"is_preprint":false},{"year":2021,"finding":"CYP24A1 expression is transcriptionally upregulated by IL-6 and TNF-α via NF-κB pathway activation in colon cancer cells; NF-κB inhibitor PDTC suppresses this induction. CYP24A1 knockdown by siRNA partially antagonizes Wnt/β-catenin pathway activation, placing CYP24A1 downstream of NF-κB and upstream of Wnt signaling.","method":"IL-6/TNF-α stimulation of HCT-116 and Caco-2 cells; NF-κB EMSA; dual-luciferase reporter assay for β-catenin transcriptional activity; siRNA CYP24A1 knockdown; NF-κB inhibitor (PDTC); anti-TNF-α monoclonal antibody and NF-κB antisense oligonucleotides in mouse UC-associated carcinoma model","journal":"Current medical science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA plus reporter assay and siRNA with in vivo mouse validation; single lab, multiple methods","pmids":["36255661"],"is_preprint":false},{"year":2016,"finding":"CYP24A1 overexpression in lung adenocarcinoma cells (SK-LU-1, Calu-6) accelerates cell growth and invasion, and increases RAS protein expression. Knockdown of CYP24A1 reduces total RAS protein, phosphorylated AKT, cell proliferation (30–60%), and mitochondrial DNA content; stable shRNA knockdown delays xenograft tumor growth and reduces Ki67 and Cyclin D staining.","method":"Stable lentiviral CYP24A1 overexpression; siRNA/shRNA knockdown; Western blot for RAS, pAKT; xenograft tumor models; bioluminescence imaging; immunohistochemistry","journal":"Journal of thoracic oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro gain/loss-of-function plus in vivo xenograft; single lab; RAS link based on protein level changes without direct biochemical interaction","pmids":["27793774"],"is_preprint":false},{"year":2022,"finding":"A 70-nucleotide DNA aptamer (Apt-7) selectively inhibits CYP24A1 enzyme activity (reducing relative CYP24 activity by 39.1%) with 5.8-fold higher binding affinity for CYP24A1 than for CYP27B1 (the countertarget). Apt-7 undergoes cellular internalization in CYP24-overexpressing A549 cells via endocytosis and induces antiproliferative activity.","method":"Competition-based aptamer selection (SELEX); binding affinity assay; in vitro CYP24A1 enzyme activity assay; high-speed atomic force microscopy; molecular docking; cellular internalization assay; antiproliferative assay","journal":"ACS applied materials & interfaces","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct enzyme inhibition assay validated by AFM and cell-based functional assay; single lab","pmids":["35436103"],"is_preprint":false},{"year":2014,"finding":"BRAFV600E mutation in thyroid cancer cell lines drives CYP24A1 overexpression; transfection of BRAFV600E transgene into CAL62 cells induces CYP24A1 expression, and the BRAFV600E inhibitor PLX4720 down-regulates CYP24A1 and enhances antiproliferative effects of calcitriol. This demonstrates a MAPK pathway → CYP24A1 regulatory axis.","method":"RT-PCR and Western blot in thyroid cancer cell lines stratified by BRAF status; BRAFV600E transgene overexpression; PLX4720 inhibitor treatment; antiproliferative assay","journal":"Clinical endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function (BRAFV600E transgene) plus inhibitor treatment with mechanistic readout; single lab","pmids":["24382015"],"is_preprint":false},{"year":2006,"finding":"RNAi silencing of CYP27B1 in human osteosarcoma (HOS) cells abolishes de novo 1,25D synthesis and subsequently reduces CYP24 mRNA expression, demonstrating that locally synthesized 1,25D (via CYP27B1) drives CYP24 expression in bone cells through an autocrine/paracrine mechanism.","method":"siRNA transfection for CYP27B1; 1,25D measurement in conditioned medium; RT-PCR for CYP27B1, CYP24, and osteocalcin mRNA","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi with direct metabolite measurement and downstream gene expression; single lab, two orthogonal readouts","pmids":["17254772"],"is_preprint":false}],"current_model":"CYP24A1 is a mitochondrial cytochrome P450 enzyme that initiates vitamin D catabolism by catalyzing sequential C-24 and C-23 hydroxylations of both 25(OH)D3 and 1,25(OH)2D3 through dual oxidative pathways (C-24 pathway to calcitroic acid; C-23 pathway to 25(OH)D3-26,23-lactone), with substrate docking directed by the distance of C-24 from the vitamin D A-ring (not side-chain terminus) and residue F249 critical for active-site alignment; its transcription is principally driven by 1,25(OH)2D3-activated VDR binding to promoter-proximal VDREs cooperatively with downstream kidney-specific (C24-DS1/pCREB-CRTC2) and pan-tissue (C24-DS2/VDR) distal enhancers, induced by FGF23 and suppressed by PTH via rapid CREB coactivator exchange at these enhancers, additionally regulated by MAP kinases (ERK5/Ets-1 and ERK1/2/RXRα), NF-κB, BRAFV600E/MAPK, progesterone receptor, CK2, valproic acid (via ERK), and IRES-mediated translation under inflammatory conditions, as well as epigenetic control through LSH-mediated chromatin remodeling and miR-125b-dependent post-transcriptional suppression; loss-of-function mutations cause idiopathic infantile hypercalcemia due to failure to catabolize active vitamin D metabolites, while overexpression in cancers promotes resistance to vitamin D antiproliferative effects partly through RAS/AKT and Wnt/β-catenin signaling."},"narrative":{"mechanistic_narrative":"CYP24A1 is a mitochondrial cytochrome P450 that initiates catabolic inactivation of vitamin D metabolites, controlling local and systemic availability of active 1,25(OH)2D3 [PMID:11012668, PMID:33865853]. A single human enzyme reconstituted with adrenodoxin/adrenodoxin reductase executes the complete multi-step catabolism through dual oxidative routes—C-24 hydroxylation toward the tetranor product and C-23 hydroxylation toward lactol/lactone—on both 25(OH)D3 and 1,25(OH)2D3, whereas the rat ortholog performs little C-23 chemistry [PMID:11012668]. Hydroxylation-site selection is set by the distance of C-24 from the vitamin D ring rather than from the side-chain terminus, and high-affinity substrate binding depends on the 1α- and 25-hydroxyl groups together with F-helix residue F249, which aligns the substrate for the catalytic steps [PMID:15111121, PMID:7622489]. The enzyme also catabolizes noncanonical substrates such as 20(OH)D3, and the terminal 26,23-lactone-forming step requires a separate CYP3A activity rather than CYP24A1 itself [PMID:33865853, PMID:25727742]. Transcription is driven principally by ligand-activated VDR acting through promoter-proximal VDREs that cooperate with downstream distal enhancer clusters, including a kidney-specific PTH/FGF23-responsive pCREB/CRTC2 module (C24-DS1) and a pan-tissue VDR module (C24-DS2); PTH suppresses transcription by dismissing CBP from these distal enhancers, defining a coactivator-exchange mechanism for renal vitamin D homeostasis [PMID:22179019, PMID:31439663, PMID:36183832, PMID:39363152]. Expression is further tuned by Ras/MAP-kinase signaling (ERK1/2–RXRα and ERK5–Ets-1), CK2, NF-κB, progesterone receptor, IRES-mediated translation under inflammation, chromatin remodeling by LSH, and miR-125b-dependent post-transcriptional repression [PMID:12048211, PMID:19570947, PMID:36183832, PMID:24416388, PMID:37414755]. Physiologically, CYP24A1 governs local 1,25(OH)2D availability in tissues such as the mammary gland during development and contributes to FGF23-driven phosphate-wasting bone disease [PMID:30654105, PMID:26784541]. Recessive loss-of-function mutations cause idiopathic infantile hypercalcemia through failure to catabolize active vitamin D metabolites, and CYP24A1 overexpression in cancers confers resistance to vitamin D antiproliferative effects, in part through RAS/AKT and Wnt/β-catenin signaling [PMID:21675912, PMID:36255661, PMID:27793774].","teleology":[{"year":2000,"claim":"Established that a single human enzyme, not a set of distinct hydroxylases, performs the entire multi-step vitamin D catabolic cascade via two parallel oxidative pathways, resolving how vitamin D metabolites are fully inactivated.","evidence":"Recombinant E. coli expression with adrenodoxin/adrenodoxin reductase reconstitution and HPLC-MS metabolite identification, comparing human and rat enzyme","pmids":["11012668"],"confidence":"High","gaps":["Did not define the structural basis for the human-specific C-23 pathway activity","No structure of the enzyme-substrate complex"]},{"year":1995,"claim":"Determined that hydroxylation-site selection is governed by distance of C-24 from the vitamin D ring, explaining the regiochemistry of CYP24-mediated oxidation versus CYP27.","evidence":"Cell-based enzyme assays with side-chain-homologated substrates and HPLC/GC-MS product identification","pmids":["7622489"],"confidence":"Medium","gaps":["Single lab; no atomic-resolution active-site model","Did not test the full panel of physiological substrates"]},{"year":2004,"claim":"Identified the F-helix residue F249 and the 1α/25-hydroxyls as the key determinants of substrate alignment and high-affinity binding, mapping catalytic competence onto specific residues and substrate features.","evidence":"Recombinant rat CYP24A1 purification with spectral binding (Kd), kinetics, and site-directed mutagenesis at F249","pmids":["15111121"],"confidence":"High","gaps":["Performed in rat enzyme; human-specific residue dependencies not fully mapped","No crystal structure confirming F249 positioning"]},{"year":2002,"claim":"Showed that ligand-activated CYP24 induction requires Ras-dependent MAP-kinase phosphorylation of nuclear receptor partners, linking signaling to vitamin D transcriptional output.","evidence":"Promoter-luciferase assays with dominant-negative kinases, phosphosite mutagenesis of RXRα(S260) and Ets-1(T38), Co-IP and kinase assays","pmids":["12048211"],"confidence":"High","gaps":["Promoter-reporter system may not reflect endogenous chromatin context","Species differences in MAPK-responsive elements not resolved here"]},{"year":2005,"claim":"Probed whether xenobiotic receptor PXR induces CYP24 to explain drug effects on vitamin D, but the two reports reached opposite conclusions about PXR's role.","evidence":"Promoter-luciferase, PXR transfection, human hepatocyte mRNA and enzyme activity, in vivo treatment (induction report) versus reporter assays, PXR-KO mice and human biopsies (contradicting report)","pmids":["15630458","16691293"],"confidence":"Medium","gaps":["Direct contradiction between studies unresolved","Tissue- and species-specific PXR effects not reconciled"]},{"year":2005,"claim":"Demonstrated direct pharmacological inhibition of CYP24A1 enzyme activity extends 1,25(OH)2D3 half-life and antiproliferative signaling, establishing the enzyme as a druggable target.","evidence":"Noncompetitive enzyme kinetics in isolated DU145 mitochondria with genistein, plus VDR and growth readouts","pmids":["15955619"],"confidence":"Medium","gaps":["Single lab; selectivity for CYP24A1 over other CYPs not fully established","In vivo relevance not tested"]},{"year":2009,"claim":"Identified post-transcriptional control of CYP24A1 by miR-125b, adding a layer of regulation relevant to its overexpression in cancer.","evidence":"3'-UTR reporter assays with gain/loss of miR-125b, endogenous Western blots, and breast cancer tissue immunohistochemistry","pmids":["19570947"],"confidence":"High","gaps":["Causal contribution of miR-125b loss to tumor CYP24A1 elevation not tested in vivo","Other 3'-UTR regulators not surveyed"]},{"year":2011,"claim":"Established CYP24A1 as the disease gene for idiopathic infantile hypercalcemia, directly tying loss of vitamin D catabolism to a human Mendelian phenotype.","evidence":"Candidate-gene sequencing of patient cohorts with functional expression of mutant enzymes in a mammalian system","pmids":["21675912"],"confidence":"High","gaps":["Genotype-phenotype severity correlations not fully defined","Heterozygote contributions not resolved"]},{"year":2011,"claim":"Mapped the cis-regulatory architecture of Cyp24a1 to proximal VDREs plus novel downstream-distal enhancers and C/EBPβ occupancy, moving beyond a simple proximal-promoter model.","evidence":"ChIP-chip/ChIP-seq in cells and mouse tissues with luciferase reporters","pmids":["22179019"],"confidence":"High","gaps":["Functional requirement of individual enhancers in vivo not yet tested at this stage","Tissue-specific enhancer usage undefined"]},{"year":2019,"claim":"Demonstrated by in vivo enhancer deletion that a kidney-specific PTH/FGF23-responsive cluster and a pan-tissue VDR cluster differentially control Cyp24a1, dissecting hormonal versus ligand inputs.","evidence":"ChIP-seq and clustered enhancer deletion mouse models with PTH/FGF23/1,25(OH)2D3 challenge; reciprocal Cyp27b1 submodule deletions","pmids":["31439663","31629064"],"confidence":"High","gaps":["Human enhancer conservation and function not directly established","Precise transcription-factor occupancy dynamics within clusters not fully resolved"]},{"year":2022,"claim":"Defined the coactivator-exchange mechanism by which PTH suppresses Cyp24a1—dismissing CBP from distal enhancers while recruiting pCREB/CRTC2 to Cyp27b1—and showed SIK inhibition mimics PTH.","evidence":"In vivo kidney ChIP-seq for pCREB/CBP/CRTC2 after PTH, FGF23, 1,25(OH)2D3, and SIK inhibitor treatment","pmids":["36183832"],"confidence":"High","gaps":["Direct demonstration of physical looping linking enhancers to promoter in kidney not shown","Human translation of SIK/CRTC2 axis untested"]},{"year":2024,"claim":"Established cooperative interaction between proximal VDREs and downstream enhancers in vivo, showing proximal VDRE integrity is required for VDR loading across the locus and for ligand induction but not PTH suppression.","evidence":"In vivo VDRE mutagenesis in mice with VDR/pCREB ChIP-seq and hormonal challenge","pmids":["39363152"],"confidence":"High","gaps":["Mechanism of long-range VDRE-enhancer cooperation not structurally resolved","Residual FGF23 induction pathway not identified"]},{"year":2021,"claim":"Used Cyp24a1-knockout rats to confirm the enzyme is responsible for the bulk of 25(OH)D3 metabolite production and to assign the terminal 26,23-lactone step to CYP3A rather than CYP24A1.","evidence":"CRISPR/Cas9 KO rats with plasma metabolite profiling, recombinant CYP enzyme assays, and ketoconazole inhibition","pmids":["33865853"],"confidence":"High","gaps":["Relative in vivo contribution of CYP3A in humans not quantified","Tissue-specific metabolite handling not dissected"]},{"year":2015,"claim":"Broadened the substrate scope of CYP24A1 to noncanonical 20(OH)D3 derivatives, including C23-C24 bond cleavage, showing the enzyme processes alternative vitamin D species.","evidence":"In vitro recombinant rat and human enzyme assays with NMR/HRMS product identification and kinetics","pmids":["25727742"],"confidence":"High","gaps":["Physiological abundance/relevance of these substrates not established","Lower catalytic efficiency relative to canonical substrates limits inference"]},{"year":2019,"claim":"Demonstrated a tissue-developmental role: CYP24A1 modulates local 1,25(OH)2D availability to permit mammary epithelial proliferation during puberty and pregnancy.","evidence":"Mammary-specific conditional Cyp24a1 knockout with whole-mount analysis, proliferation/apoptosis markers, and in vitro 1,25(OH)2D3 sensitivity","pmids":["30654105"],"confidence":"High","gaps":["Downstream proliferative effectors not identified","Whether this generalizes to other epithelial tissues unclear"]},{"year":2016,"claim":"Linked CYP24 activity to FGF23-driven phosphate-wasting bone disease, showing genetic or pharmacological loss of CYP24 rescues rachitic bone in two disease models.","evidence":"Cyp24-null crosses with Hyp and FGF23R176Q mice plus CTA102 inhibitor treatment, with bone histomorphometry","pmids":["26784541"],"confidence":"High","gaps":["Mechanism connecting CYP24 metabolites to bone mineralization not fully resolved","Human therapeutic translation not established"]},{"year":2021,"claim":"Implicated CYP24A1 in cancer signaling and ferroptosis sensitivity through Ca2+/MAPK control and chromatin-remodeling/Wnt circuitry, framing it as both oncogenic effector and regulatory node.","evidence":"SQLE manipulation with metabolomics and xenografts; NF-κB-driven induction with β-catenin reporters and siRNA; LSH/USP11 Co-IP, ChIP, and ferroptosis assays; lung adenocarcinoma gain/loss with RAS/pAKT readouts and xenografts","pmids":["34268906","36255661","37414755","27793774"],"confidence":"Medium","gaps":["RAS/Wnt links rest on protein-level changes without direct biochemical interaction","Causality among CYP24A1, Ca2+, and MAPK/Wnt not fully ordered","Single-lab studies per mechanism"]},{"year":null,"claim":"How the human enzyme's active-site architecture enforces dual C-23/C-24 pathway selection and how distal enhancer cooperation is structurally organized at the human locus remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of human CYP24A1-substrate complex in the corpus","Human enhancer-promoter looping mechanism not directly demonstrated","PXR regulation of human CYP24 remains contradictory"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,1,20,21]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,8]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[6,0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,20,8]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[9,10,12,13]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q07973","full_name":"1,25-dihydroxyvitamin D(3) 24-hydroxylase, mitochondrial","aliases":["Cytochrome P450 24A1","Cytochrome P450-CC24"],"length_aa":514,"mass_kda":58.9,"function":"A cytochrome P450 monooxygenase with a key role in vitamin D catabolism and calcium homeostasis. Via C24- and C23-oxidation pathways, catalyzes the inactivation of both the vitamin D precursor calcidiol (25-hydroxyvitamin D(3)) and the active hormone calcitriol (1-alpha,25-dihydroxyvitamin D(3)) (PubMed:11012668, PubMed:15574355, PubMed:16617161, PubMed:24893882, PubMed:29461981, PubMed:8679605). With initial hydroxylation at C-24 (via C24-oxidation pathway), performs a sequential 6-step oxidation of calcitriol leading to the formation of the biliary metabolite calcitroic acid (PubMed:15574355, PubMed:24893882). With initial hydroxylation at C-23 (via C23-oxidation pathway), catalyzes sequential oxidation of calcidiol leading to the formation of 25(OH)D3-26,23-lactone as end product (PubMed:11012668, PubMed:8679605). Preferentially hydroxylates at C-25 other vitamin D active metabolites, such as CYP11A1-derived secosteroids 20S-hydroxycholecalciferol and 20S,23-dihydroxycholecalciferol (PubMed:25727742). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via FDXR/adrenodoxin reductase and FDX1/adrenodoxin (PubMed:8679605)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q07973/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CYP24A1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CYP24A1","total_profiled":1310},"omim":[{"mim_id":"619073","title":"VITAMIN D-DEPENDENT RICKETS, TYPE 3; VDDR3","url":"https://www.omim.org/entry/619073"},{"mim_id":"616963","title":"HYPERCALCEMIA, INFANTILE, 2; HCINF2","url":"https://www.omim.org/entry/616963"},{"mim_id":"609506","title":"CYTOCHROME P450, SUBFAMILY XXVIIB, POLYPEPTIDE 1; CYP27B1","url":"https://www.omim.org/entry/609506"},{"mim_id":"608713","title":"CYTOCHROME P450, SUBFAMILY IIR, POLYPEPTIDE 1; CYP2R1","url":"https://www.omim.org/entry/608713"},{"mim_id":"603072","title":"AURORA KINASE A; AURKA","url":"https://www.omim.org/entry/603072"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"endometrium 1","ntpm":14.1},{"tissue":"kidney","ntpm":31.6},{"tissue":"lymphoid tissue","ntpm":9.9},{"tissue":"placenta","ntpm":9.4},{"tissue":"urinary bladder","ntpm":27.0}],"url":"https://www.proteinatlas.org/search/CYP24A1"},"hgnc":{"alias_symbol":["CP24","P450-CC24","lncBCAS1-4_1"],"prev_symbol":["CYP24"]},"alphafold":{"accession":"Q07973","domains":[{"cath_id":"1.10.630.10","chopping":"55-514","consensus_level":"medium","plddt":94.5276,"start":55,"end":514}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07973","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q07973-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q07973-F1-predicted_aligned_error_v6.png","plddt_mean":88.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CYP24A1","jax_strain_url":"https://www.jax.org/strain/search?query=CYP24A1"},"sequence":{"accession":"Q07973","fasta_url":"https://rest.uniprot.org/uniprotkb/Q07973.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q07973/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07973"}},"corpus_meta":[{"pmid":"21675912","id":"PMC_21675912","title":"Mutations in CYP24A1 and idiopathic infantile hypercalcemia.","date":"2011","source":"The New England journal of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/21675912","citation_count":456,"is_preprint":false},{"pmid":"22100522","id":"PMC_22100522","title":"25-Hydroxyvitamin D-24-hydroxylase (CYP24A1): its important role in the degradation of vitamin D.","date":"2011","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/22100522","citation_count":392,"is_preprint":false},{"pmid":"15630458","id":"PMC_15630458","title":"Possible involvement of pregnane X receptor-enhanced CYP24 expression in drug-induced osteomalacia.","date":"2005","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/15630458","citation_count":231,"is_preprint":false},{"pmid":"16180015","id":"PMC_16180015","title":"Expression of VDR and CYP24A1 mRNA in human tumors.","date":"2005","source":"Cancer chemotherapy and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/16180015","citation_count":191,"is_preprint":false},{"pmid":"17114352","id":"PMC_17114352","title":"Lack of the light-harvesting complex CP24 affects the structure and function of the grana membranes of higher plant chloroplasts.","date":"2006","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/17114352","citation_count":190,"is_preprint":false},{"pmid":"16691293","id":"PMC_16691293","title":"Steroid and xenobiotic receptor and vitamin D receptor crosstalk mediates CYP24 expression and drug-induced osteomalacia.","date":"2006","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/16691293","citation_count":171,"is_preprint":false},{"pmid":"11012668","id":"PMC_11012668","title":"Dual metabolic pathway of 25-hydroxyvitamin D3 catalyzed by human CYP24.","date":"2000","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11012668","citation_count":152,"is_preprint":false},{"pmid":"19570947","id":"PMC_19570947","title":"Human CYP24 catalyzing the inactivation of calcitriol is post-transcriptionally regulated by miR-125b.","date":"2009","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/19570947","citation_count":126,"is_preprint":false},{"pmid":"19901270","id":"PMC_19901270","title":"The candidate oncogene CYP24A1: A potential biomarker for colorectal tumorigenesis.","date":"2009","source":"The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society","url":"https://pubmed.ncbi.nlm.nih.gov/19901270","citation_count":111,"is_preprint":false},{"pmid":"12048211","id":"PMC_12048211","title":"Role of MAP kinases in the 1,25-dihydroxyvitamin D3-induced transactivation of the rat cytochrome P450C24 (CYP24) promoter. Specific functions for ERK1/ERK2 and ERK5.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12048211","citation_count":92,"is_preprint":false},{"pmid":"14760115","id":"PMC_14760115","title":"Clinical significance of the overexpression of the candidate oncogene CYP24 in esophageal cancer.","date":"2004","source":"Annals of oncology : official journal of the European Society for Medical Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/14760115","citation_count":85,"is_preprint":false},{"pmid":"16708384","id":"PMC_16708384","title":"CYP24, the enzyme that catabolizes the antiproliferative agent vitamin D, is increased in lung cancer.","date":"2006","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/16708384","citation_count":79,"is_preprint":false},{"pmid":"31629064","id":"PMC_31629064","title":"Mechanistic homeostasis of vitamin D metabolism in the kidney through reciprocal modulation of Cyp27b1 and 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standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"Human CYP24A1 (expressed in E. coli reconstituted system with adrenodoxin and adrenodoxin reductase) catalyzes both C-23 and C-24 hydroxylation pathways on 25(OH)D3 and 1α,25(OH)2D3, performing all sequential oxidative steps from substrate through lactol to lactone (C-23 pathway) and through 24-oxo intermediates to tetranor product (C-24 pathway), whereas rat CYP24A1 shows almost no C-23 hydroxylation—demonstrating that a single human enzyme executes the complete multi-step catabolism via dual pathways.\",\n      \"method\": \"Recombinant E. coli expression with adrenodoxin/adrenodoxin reductase reconstitution; HPLC and mass spectrometric metabolite identification\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with full metabolite identification by HPLC-MS; replicated in whole-cell E. coli coexpression system in the same study\",\n      \"pmids\": [\"11012668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Phenylalanine-249 (F249) in the F-helix of rat CYP24A1 is critical for substrate binding and catalytic site alignment: mutagenesis to F249T (hydrophobic→polar) dramatically lowers substrate-binding affinity and abolishes the final C-23 oxidation step; F249A and F249Y mutations additionally impair C-24 oxidation of 1,24,25-(OH)3D3. The 1α- and 25-hydroxyl groups on vitamin D metabolites are the major determinants for high-affinity binding (Kd ~0.05–0.06 µM), and turnover is higher for 25(OH)D3 than for 1,25(OH)2D3.\",\n      \"method\": \"Recombinant CYP24A1 purification from E. coli; substrate-induced spectral binding assays (Kd); kinetic analysis (Km, Vmax); site-directed mutagenesis at F249\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and kinetic characterization in a single rigorous study\",\n      \"pmids\": [\"15111121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"CYP24 hydroxylates at C-24 and C-23 regardless of side-chain length extension (by 1–3 carbons), indicating that CYP24's hydroxylation site selection is determined by the distance of C-24 from the vitamin D ring structure, not by the distance from the end of the side chain (contrast with CYP27 which tracks from the terminus).\",\n      \"method\": \"Cultured and transfected cell models expressing CYP24 or CYP27; HPLC and GC-MS metabolite identification of homologated vitamin D substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based enzyme assay with series of synthetic substrates and HPLC-GC/MS identification; single lab but multiple substrates and orthogonal methods\",\n      \"pmids\": [\"7622489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"1,25-dihydroxyvitamin D3 (1,25D) induces CYP24 promoter activity through a Ras-dependent mechanism engaging two distinct MAP kinase modules: ERK1/ERK2 phosphorylates RXRα at Ser260, and ERK5 phosphorylates Ets-1 at Thr38; both phosphorylation events are required for full induction. The Ets-1 binding site cooperates with the proximal vitamin D response element in a hormone-dependent manner. p38 and JNK MAP kinases are not required.\",\n      \"method\": \"CYP24 promoter-luciferase transfection; dominant-negative mutants of ERK1 (K71R), MEK5(A), Ras17N; site-directed mutagenesis of Ets-1 (T38A) and RXRα (S260A); co-immunoprecipitation of RXRα with ERK2 and Ets-1 with ERK5; phosphorylation assays with activated kinases\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (dominant-negative mutants, site-directed mutagenesis of phosphorylation sites, Co-IP, kinase assays) in a single focused mechanistic study\",\n      \"pmids\": [\"12048211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Pregnane X receptor (PXR) transactivates the human CYP24 promoter by binding to the two proximal vitamin D-responsive elements (VDREs) located between −326 and −142, thereby inducing CYP24 mRNA and 24-hydroxylase enzyme activity in human hepatocytes in response to rifampicin and hyperforin. This provides a molecular mechanism for drug-induced osteomalacia.\",\n      \"method\": \"CYP24 promoter-luciferase reporter assay in HEK cells; transfection of PXR; RT-PCR for CYP24 mRNA in human hepatocytes; 24-hydroxylase enzyme activity assay; in vivo PCN/dexamethasone treatment of mice; plasma 24,25-(OH)2D3 measurement\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (reporter assay, co-transfection, mRNA, enzyme activity, in vivo) in a single study by one lab\",\n      \"pmids\": [\"15630458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Steroid and xenobiotic receptor (SXR/PXR) does NOT induce CYP24 expression in vitro or in vivo, does not transactivate the CYP24 promoter, and instead inhibits VDR-mediated CYP24 promoter activity. 1,25(OH)2D3-induced CYP24 expression is enhanced in mice lacking PXR. Rifampicin had no effect on intestinal CYP24 expression in humans. This contradicts the earlier PXR-induction report (PMID:15630458).\",\n      \"method\": \"CYP24 promoter-luciferase assay; in vitro and in vivo SXR/PXR agonist treatment; PXR-knockout mouse studies; human intestinal biopsies post-rifampicin\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (reporter, KO mouse, human biopsy) contradicting prior study; single lab; conflicting with PMID:15630458 so confidence reduced\",\n      \"pmids\": [\"16691293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Genistein (50–100 nM) directly inhibits CYP24A1 enzyme activity in a noncompetitive manner in isolated mitochondrial preparations from DU145 cells, thereby increasing the half-life of 1,25(OH)2D3 and enhancing VDR up-regulation and antiproliferative signaling.\",\n      \"method\": \"CYP24 enzyme activity assay in isolated mitochondrial preparations; kinetic (noncompetitive inhibition) analysis; VDR mRNA/protein measurement; cell growth assay\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct enzyme activity assay on isolated mitochondria with kinetic characterization; single lab, two orthogonal methods\",\n      \"pmids\": [\"15955619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"miR-125b post-transcriptionally regulates CYP24A1 protein levels by binding a recognition element (MRE125b) in the 3'-UTR of CYP24 mRNA: transfection of antisense oligonucleotide for miR-125b increases endogenous CYP24 protein in KGN cells, while precursor miR-125b decreases it in MCF-7 cells. Decreased miR-125b in breast cancer tissues inversely correlates with increased CYP24 protein levels.\",\n      \"method\": \"3'-UTR luciferase reporter assay; antisense oligonucleotide and precursor miRNA transfection; Western blot for endogenous CYP24 protein; immunohistochemistry of breast cancer tissues\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (reporter assay with gain/loss of function, endogenous protein change, tissue validation) providing strong mechanistic evidence in a single focused study\",\n      \"pmids\": [\"19570947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Loss-of-function mutations in CYP24A1 (encoding 25-hydroxyvitamin D3 24-hydroxylase) cause idiopathic infantile hypercalcemia via complete loss of vitamin D catabolism. Functional characterization in a mammalian expression system confirmed complete loss of enzymatic function for all identified recessive mutations.\",\n      \"method\": \"Candidate-gene sequencing; mammalian expression system functional assay of mutant CYP24A1 enzyme activity\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — combined genetic identification and functional expression characterization; multiple mutations independently confirmed; replicated across two patient cohorts\",\n      \"pmids\": [\"21675912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The mouse Cyp24a1 gene is controlled by both promoter-proximal VDR binding sites (~−160 and −265 nt from TSS) and novel downstream-distal intergenic enhancers (+35 and +37 kb) that together mediate 1,25(OH)2D3-dependent transcriptional up-regulation. C/EBPβ occupancy at a site −345 nt upstream is markedly increased following 1,25(OH)2D3 treatment.\",\n      \"method\": \"ChIP-chip and ChIP-seq in cell lines and mouse tissues; luciferase reporter assays; in vivo mouse chromatin analysis\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased ChIP-seq to identify enhancers, confirmed in vivo in mice; multiple orthogonal methods\",\n      \"pmids\": [\"22179019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Kidney-specific Cyp24a1 expression requires a downstream enhancer cluster (C24-DS1) that contains PTH-sensitive pCREB-binding sites: deletion of C24-DS1 in mice eliminates basal renal Cyp24a1 expression and completely abolishes FGF23 and PTH regulation of Cyp24a1, while 1,25(OH)2D3 induction remains unaffected. A second downstream cluster (C24-DS2) containing VDR-binding sites is required for full Cyp24a1 responses in non-renal target cells.\",\n      \"method\": \"ChIP-Seq in mouse tissues; clustered enhancer deletion mouse models; RNA analysis of Cyp24a1 expression in kidney and non-renal tissues; hormone challenge (PTH, FGF23, 1,25(OH)2D3)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP-Seq plus in vivo genetic deletion of specific enhancer elements with rigorous phenotypic readout; multiple deletion strains and hormone challenges\",\n      \"pmids\": [\"31439663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cyp24a1 enhancers in the kidney control circulating 1,25(OH)2D3 levels: deletion of both M1 and M21 Cyp27b1 submodules (in adjacent genes) reduces Cyp27b1 expression, which secondarily reduces Cyp24a1 expression due to compensatory regulation by elevated PTH and reduced FGF23, demonstrating reciprocal PTH/FGF23-mediated homeostatic control of both enzymes in the kidney.\",\n      \"method\": \"In vivo enhancer deletion mouse models; hormone measurements (PTH, FGF23, calcium, phosphate); RNA analysis; dietary normalization rescue experiments\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic deletion with rescue experiments and multi-parameter hormonal and molecular readouts\",\n      \"pmids\": [\"31629064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PTH rapidly increases recruitment of phosphorylated CREB (pCREB), CBP, and CRTC2 to kidney-specific enhancers near Cyp27b1, while dismissing CBP from distal Cyp24a1 enhancers to suppress Cyp24a1 transcription. Salt-inducible kinase (SIK) inhibition rapidly recruits CRTC2 to Cyp27b1 enhancers, mimicking PTH action on both Cyp27b1 and Cyp24a1. 1,25(OH)2D3 suppression of Cyp27b1 is associated with reduced CBP recruitment at CREB-module enhancers.\",\n      \"method\": \"In vivo ChIP-seq in mouse kidney after PTH, FGF23, 1,25(OH)2D3 and SIK inhibitor (YKL-05-099, SK-124) treatments; pCREB, CBP, CRTC2 occupancy analysis; RNA analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo ChIP-seq with multiple hormonal and pharmacological perturbations; mechanistically defines coactivator dynamics at specific Cyp24a1 enhancers\",\n      \"pmids\": [\"36183832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Mutation of the promoter-proximal (PRO) VDREs in mice dramatically reduces VDR occupancy and impairs 1,25(OH)2D3-induced kidney Cyp24a1 expression and nearly eliminates intestinal induction. FGF23 induction of Cyp24a1 is reduced but not eliminated and retains synergy with 1,25(OH)2D3. PTH suppression of Cyp24a1 is unchanged by PRO VDRE mutation. VDR recruitment across downstream (DS) enhancers is also dramatically reduced, revealing cooperative interaction between PRO and DS enhancers.\",\n      \"method\": \"In vivo VDRE mutagenesis in mice; ChIP-seq for VDR and pCREB occupancy; RNA analysis after 1,25(OH)2D3, FGF23, and PTH treatment\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo mutagenesis with ChIP-seq and multiple hormonal challenge experiments; defines cooperative enhancer mechanism\",\n      \"pmids\": [\"39363152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The upstream CYP24 promoter region (−548 to −294 nt, containing three potential Sp1 sites) acts synergistically with the two proximal VDREs to amplify vitamin D-induced CYP24 expression. The VDREs alone are insufficient to account for the full magnitude of induction (~20,000-fold) observed in human fibroblasts.\",\n      \"method\": \"Serial deletion reporter constructs (−1918 to +209 nt) assayed by luciferase reporter assay in cultured human fibroblasts\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic promoter deletion analysis with clear functional readout; single lab, single method type\",\n      \"pmids\": [\"17475215\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"1,25D induction of the CYP24 promoter in HEK-293T cells requires JNK (but not ERK1/2) and a novel vitamin D stimulatory element (VSE) at −171/−163, ~30 bp upstream of VDRE-1. Synergistic up-regulation by PMA + 1,25D additionally requires ERK1/2 activation (potentiated by 1,25D), JNK, and the Ets-1 binding site.\",\n      \"method\": \"CYP24 promoter-luciferase reporter assays; dominant-negative ERK1(K71R) transfection; site-directed mutagenesis of VSE; kinase inhibitors; HEK-293T cell system\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay with dominant-negative mutants and site-directed mutagenesis; single lab, multiple methods\",\n      \"pmids\": [\"15836435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Human CYP24 promoter-proximal region spanning −470 to −392 nt is required for 1,25D-mediated induction in human cells; the vitamin D stimulatory element (VSE) present in the rat promoter is absent in the human CYP24A1 promoter, indicating species-specific differences in the transcriptional mechanism.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA); dual-luciferase reporter assay with human and rat CYP24A1 promoter deletion constructs\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA plus reporter assay with deletion constructs; single lab, two complementary methods\",\n      \"pmids\": [\"20450955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The number of functional VDR binding sites (VDREs) differs between normal (MCF-10A, one VDRE) and malignant (MCF-7, three VDREs) mammary cells, producing linear vs. stepwise CYP24 mRNA accumulation respectively. Distal VDREs in MCF-7 regulate CYP24 transcription via ligand-dependent, dynamic chromatin looping that brings distal elements cyclically adjacent to the transcription start site. CYP24 mRNA is also three times more stable in MCF-7 than MCF-10A cells.\",\n      \"method\": \"Quantitative ChIP; chromosome conformation capture (3C); expression profiling; mRNA stability assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP, 3C, and mRNA stability assays providing mechanistic insight from multiple orthogonal approaches; single lab\",\n      \"pmids\": [\"20460683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Unliganded VDR represses basal CYP24 transcription in breast cancer cells: VDR overexpression decreases CYP24 mRNA and promoter activity, siRNA knockdown of VDR increases CYP24 mRNA, and a FokI-FF polymorphic VDR (3 amino acids shorter in AF-1 domain) fails to repress CYP24 promoter activity, indicating AF-1 domain integrity is required for repression.\",\n      \"method\": \"VDR overexpression and siRNA knockdown in MCF-7 and MDA-MB231 cells; CYP24 promoter-luciferase assay; RT-PCR; VDR nuclear localization by immunofluorescence\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cell lines with gain- and loss-of-function; mutagenesis of AF-1 domain; single lab\",\n      \"pmids\": [\"20440542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Inflammatory conditioned medium (from activated macrophages) induces IRES-dependent translation of CYP24A1 via an internal ribosome entry site (IRES) in the 5'-UTR of cyp24a1 mRNA. This IRES-mediated translation is sensitive to PI3K inhibition and is sufficient to be activated by constitutively active Akt.\",\n      \"method\": \"Polysome profiling and microarray analysis; bicistronic reporter assay for IRES activity; PI3K inhibitor treatment; constitutively active Akt transfection\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — bicistronic reporter validates IRES function; polysome profiling confirms translational regulation; pharmacological and genetic manipulation of PI3K/Akt pathway; multiple orthogonal methods\",\n      \"pmids\": [\"24416388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CYP24A1 is responsible for sequential multi-step conversion of 25(OH)D3 to 23,25,26-(OH)3D3 via 23,25-(OH)2D3; subsequent conversion of 23,25,26-(OH)3D3 to 25(OH)D3-26,23-lactone requires an additional enzyme identified as CYP3A (not CYP24A1). Cyp24a1 KO rats show ~2-fold higher plasma 25(OH)D3 and complete absence of the five major 25(OH)D3 metabolites found in wild-type rats.\",\n      \"method\": \"CRISPR/Cas9-generated Cyp24a1 knockout rats; oral 25(OH)D3 administration followed by plasma metabolite profiling; synthetic substrate administration to KO rats; recombinant human CYP species enzyme assay; ketoconazole inhibition studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic KO model combined with in vitro reconstitution with recombinant CYP species and pharmacological inhibition; multiple orthogonal methods to define pathway steps\",\n      \"pmids\": [\"33865853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Both rat and human CYP24A1 metabolize 20S-hydroxyvitamin D3 [20(OH)D3] to dihydroxyvitamin D3 species (primarily at C24 for rat, C25 for human CYP24A1). 20,23(OH)2D3 undergoes multiple oxidations including C23-C24 bond cleavage by CYP24A1, analogous to catabolism of 1,25(OH)2D3. Catalytic efficiencies for 20(OH)D3 and 20,23(OH)2D3 are lower than for 1,25(OH)2D3.\",\n      \"method\": \"In vitro enzyme assay with recombinant rat and human CYP24A1; NMR and high-resolution mass spectrometry for metabolite identification; kinetic analysis\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with NMR and HRMS structural identification of products; rigorous kinetic characterization; single lab\",\n      \"pmids\": [\"25727742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Protein kinase CK2 contributes to 1,25D3-mediated CYP24A1 promoter induction in prostate cancer cells: CK2 inhibitor TBBz inhibits 1,25D3-induced CYP24A1 promoter activity and mRNA; siRNA knockdown of CK2 reduces 1,25D3-induced CYP24A1 mRNA expression.\",\n      \"method\": \"Stable CYP24A1 promoter-luciferase reporter PC3 cell line; TBBz (CK2 inhibitor) treatment; siRNA CK2 knockdown; RT-PCR; in vitro and in vivo xenograft antiproliferative assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter reporter plus siRNA knockdown; single lab, two orthogonal methods\",\n      \"pmids\": [\"23358686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CYP24 promoter is epigenetically silenced by hypermethylation of CpG islands at the 5' end in tumor-derived endothelial cells (TDEC) but not in normal tissue or Matrigel-derived endothelial cells. Treatment with a DNA methyltransferase inhibitor restores 1,25(OH)2D3-induced CYP24 expression and restores calcitriol resistance in TDEC.\",\n      \"method\": \"Isolation and culture of fresh tumor-derived endothelial cells; CpG methylation analysis; DNA methyltransferase inhibitor treatment; CYP24 expression analysis; calcitriol responsiveness assays\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct methylation analysis combined with functional rescue by demethylation; single lab\",\n      \"pmids\": [\"20304059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Progesterone receptor (PR)-dependent signaling inhibits calcitriol-induced CYP24A1 expression: co-treatment with progesterone (P4) markedly suppresses CYP24A1 mRNA and protein in PR-expressing but not PR-negative cell lines. Mouse ovaries show significant reduction in calcitriol-induced Cyp24a1 mRNA and protein in response to P4. This extends calcitriol activity and enhances apoptosis.\",\n      \"method\": \"RT-PCR and Western blot for CYP24A1 in multiple cell lines (PR+ and PR−); PR isoform-expressing T47D cells; calcitriol + progesterone co-treatment; in vivo mouse ovary experiments; TUNEL apoptosis assay\",\n      \"journal\": \"Gynecologic oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cell lines with PR+/PR- controls and in vivo mouse validation; single lab\",\n      \"pmids\": [\"27106018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"5α-dihydrotestosterone (DHT) suppresses renal Cyp24a1 expression via inhibition of progesterone receptor (Pgr): DHT suppresses Pgr expression, and Pgr normally drives Cyp24a1 transcription by binding to a progesterone receptor-binding site in the Cyp24a1 promoter. DHT treatment increases blood 25(OH)D3 levels.\",\n      \"method\": \"Orchidectomized mouse model; DHT treatment; RT-PCR and Western blot for Pgr and Cyp24a1; promoter binding site analysis; ER+ and ER− cell line analysis; blood 25(OH)D3 measurement\",\n      \"journal\": \"Journal of molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mouse model plus cell-based mechanistic analysis; single lab, multiple readouts\",\n      \"pmids\": [\"29382742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LSH (lymphoid-specific helicase, a chromatin-remodeling protein) binds to the CYP24A1 promoter, promotes nucleosome eviction, and reduces H3K27me3 occupancy to activate CYP24A1 transcription. USP11 stabilizes LSH via deubiquitination; erastin disrupts USP11-LSH interaction, leading to LSH ubiquitination and degradation, which reduces CYP24A1 expression, increases intracellular Ca2+ influx, and sensitizes colorectal cancer cells to ferroptosis.\",\n      \"method\": \"Co-immunoprecipitation (USP11-LSH interaction); ChIP for LSH, H3K27me3 at CYP24A1 promoter; siRNA knockdown; ubiquitination assay; calcium measurement; lipid peroxidation assay; erastin-induced ferroptosis assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ChIP, and functional cell-based assays; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37414755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Valproic acid (VPA) potentiates VDR-mediated induction of CYP24 mRNA and promoter activity in human hepatocytes and HEK293 cells by activating ERK signaling (not solely through HDAC1 inhibition, since trichostatin A did not replicate VPA's effect on CYP24 mRNA).\",\n      \"method\": \"RT-PCR for CYP24 mRNA in human hepatocytes and HEK293; CYP24 promoter-luciferase reporter assay; trichostatin A comparison; ERK, JNK, p38 activation measurement\",\n      \"journal\": \"Toxicology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay plus mRNA in primary human hepatocytes with mechanistic distinction by TSA comparison and kinase analysis; single lab\",\n      \"pmids\": [\"21115105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mammary-specific conditional knockout of Cyp24a1 in mice reduces terminal end bud number, ductal outgrowth, and branching during puberty and alveologenesis during early pregnancy by inhibiting proliferation (but not apoptosis) of basal and luminal mammary epithelial cells, demonstrating that CYP24A1 activity modulates local 1,25(OH)2D availability and is required for normal mammary gland development.\",\n      \"method\": \"Conditional Cyp24a1 knockout in mammary epithelium; whole-mount mammary gland analysis; proliferation/apoptosis markers; in vitro sensitivity to 1,25(OH)2D3 in isolated MECs\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific conditional KO with defined proliferation phenotype and in vitro mechanistic follow-up; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"30654105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SQLE (squalene epoxidase) promotes colorectal cancer proliferation through accumulation of calcitriol, which stimulates CYP24A1 expression; elevated CYP24A1 in turn reduces intracellular Ca2+ and activates MAPK signaling to drive proliferation. SQLE inhibition reduces calcitriol and CYP24A1 levels, increases intracellular Ca2+, and suppresses MAPK and cell growth.\",\n      \"method\": \"RNA sequencing; transcriptome and untargeted metabolomics; Western blotting and RT-PCR for CYP24A1 and MAPK pathway; SQLE siRNA knockdown; organoid and xenograft tumor models; SQLE inhibitor (terbinafine) treatment\",\n      \"journal\": \"Cancer communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — integrated transcriptomics, metabolomics, and in vivo xenograft with pathway manipulation; single lab\",\n      \"pmids\": [\"34268906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of Cyp24 in Hyp mice (FGF23-excess model of X-linked hypophosphatemic rickets) and FGF23R176Q transgenic mice results in near-complete recovery of rachitic/osteomalacic bone abnormalities. Treatment with CYP24 inhibitor CTA102 also ameliorates rachitic bones in both models, linking CYP24 activity to the pathophysiology of FGF23-dependent phosphate-wasting states.\",\n      \"method\": \"Cyp24-null mouse crossed with Hyp and FGF23R176Q transgenic mice; bone histomorphometry; CYP24 inhibitor CTA102 pharmacological treatment; serum biochemistry\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic cross of KO onto disease models plus pharmacological inhibition, both yielding consistent rescue of bone phenotype; replicated in two disease models\",\n      \"pmids\": [\"26784541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In human monocyte-derived dendritic cells (DCs), 1,25(OH)2D3 stimulation up-regulates CYP24A1, which curtails the functional effects of vitamin D in DCs (but not macrophages), limiting autocrine vitamin D activity. DCs also express a truncated CYP27B1 transcript that reduces activation of 25(OH)D to 1,25(OH)2D.\",\n      \"method\": \"Monocyte-derived DC and macrophage cultures; RT-PCR for CYP24A1 and CYP27B1 isoforms; 25(OH)D to 1,25(OH)2D conversion assay; VDR-responsive gene expression; DC maturation and T-cell response assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — primary human cell comparisons with functional vitamin D responsiveness assays; single lab, multiple methods\",\n      \"pmids\": [\"24643654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CYP24A1 localizes to the annulus of human spermatozoa (co-localizing with VDR in ~80% of spermatozoa from young men), and its expression at this subcellular site correlates positively with sperm count, concentration, motility, and morphology. 1,25(OH)2D3 increases intracellular Ca2+ and motility in young men with CYP24A1-expressing sperm but not in subfertile men lacking the protein.\",\n      \"method\": \"Immunocytochemistry (ICC) for CYP24A1 and VDR in human spermatozoa; double ICC co-localization; intracellular Ca2+ measurement; sperm motility assay\",\n      \"journal\": \"International journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization with functional correlation; single lab; no genetic manipulation to establish causality\",\n      \"pmids\": [\"22404291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CYP24A1 expression is transcriptionally upregulated by IL-6 and TNF-α via NF-κB pathway activation in colon cancer cells; NF-κB inhibitor PDTC suppresses this induction. CYP24A1 knockdown by siRNA partially antagonizes Wnt/β-catenin pathway activation, placing CYP24A1 downstream of NF-κB and upstream of Wnt signaling.\",\n      \"method\": \"IL-6/TNF-α stimulation of HCT-116 and Caco-2 cells; NF-κB EMSA; dual-luciferase reporter assay for β-catenin transcriptional activity; siRNA CYP24A1 knockdown; NF-κB inhibitor (PDTC); anti-TNF-α monoclonal antibody and NF-κB antisense oligonucleotides in mouse UC-associated carcinoma model\",\n      \"journal\": \"Current medical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA plus reporter assay and siRNA with in vivo mouse validation; single lab, multiple methods\",\n      \"pmids\": [\"36255661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CYP24A1 overexpression in lung adenocarcinoma cells (SK-LU-1, Calu-6) accelerates cell growth and invasion, and increases RAS protein expression. Knockdown of CYP24A1 reduces total RAS protein, phosphorylated AKT, cell proliferation (30–60%), and mitochondrial DNA content; stable shRNA knockdown delays xenograft tumor growth and reduces Ki67 and Cyclin D staining.\",\n      \"method\": \"Stable lentiviral CYP24A1 overexpression; siRNA/shRNA knockdown; Western blot for RAS, pAKT; xenograft tumor models; bioluminescence imaging; immunohistochemistry\",\n      \"journal\": \"Journal of thoracic oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro gain/loss-of-function plus in vivo xenograft; single lab; RAS link based on protein level changes without direct biochemical interaction\",\n      \"pmids\": [\"27793774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A 70-nucleotide DNA aptamer (Apt-7) selectively inhibits CYP24A1 enzyme activity (reducing relative CYP24 activity by 39.1%) with 5.8-fold higher binding affinity for CYP24A1 than for CYP27B1 (the countertarget). Apt-7 undergoes cellular internalization in CYP24-overexpressing A549 cells via endocytosis and induces antiproliferative activity.\",\n      \"method\": \"Competition-based aptamer selection (SELEX); binding affinity assay; in vitro CYP24A1 enzyme activity assay; high-speed atomic force microscopy; molecular docking; cellular internalization assay; antiproliferative assay\",\n      \"journal\": \"ACS applied materials & interfaces\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct enzyme inhibition assay validated by AFM and cell-based functional assay; single lab\",\n      \"pmids\": [\"35436103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BRAFV600E mutation in thyroid cancer cell lines drives CYP24A1 overexpression; transfection of BRAFV600E transgene into CAL62 cells induces CYP24A1 expression, and the BRAFV600E inhibitor PLX4720 down-regulates CYP24A1 and enhances antiproliferative effects of calcitriol. This demonstrates a MAPK pathway → CYP24A1 regulatory axis.\",\n      \"method\": \"RT-PCR and Western blot in thyroid cancer cell lines stratified by BRAF status; BRAFV600E transgene overexpression; PLX4720 inhibitor treatment; antiproliferative assay\",\n      \"journal\": \"Clinical endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function (BRAFV600E transgene) plus inhibitor treatment with mechanistic readout; single lab\",\n      \"pmids\": [\"24382015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"RNAi silencing of CYP27B1 in human osteosarcoma (HOS) cells abolishes de novo 1,25D synthesis and subsequently reduces CYP24 mRNA expression, demonstrating that locally synthesized 1,25D (via CYP27B1) drives CYP24 expression in bone cells through an autocrine/paracrine mechanism.\",\n      \"method\": \"siRNA transfection for CYP27B1; 1,25D measurement in conditioned medium; RT-PCR for CYP27B1, CYP24, and osteocalcin mRNA\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi with direct metabolite measurement and downstream gene expression; single lab, two orthogonal readouts\",\n      \"pmids\": [\"17254772\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CYP24A1 is a mitochondrial cytochrome P450 enzyme that initiates vitamin D catabolism by catalyzing sequential C-24 and C-23 hydroxylations of both 25(OH)D3 and 1,25(OH)2D3 through dual oxidative pathways (C-24 pathway to calcitroic acid; C-23 pathway to 25(OH)D3-26,23-lactone), with substrate docking directed by the distance of C-24 from the vitamin D A-ring (not side-chain terminus) and residue F249 critical for active-site alignment; its transcription is principally driven by 1,25(OH)2D3-activated VDR binding to promoter-proximal VDREs cooperatively with downstream kidney-specific (C24-DS1/pCREB-CRTC2) and pan-tissue (C24-DS2/VDR) distal enhancers, induced by FGF23 and suppressed by PTH via rapid CREB coactivator exchange at these enhancers, additionally regulated by MAP kinases (ERK5/Ets-1 and ERK1/2/RXRα), NF-κB, BRAFV600E/MAPK, progesterone receptor, CK2, valproic acid (via ERK), and IRES-mediated translation under inflammatory conditions, as well as epigenetic control through LSH-mediated chromatin remodeling and miR-125b-dependent post-transcriptional suppression; loss-of-function mutations cause idiopathic infantile hypercalcemia due to failure to catabolize active vitamin D metabolites, while overexpression in cancers promotes resistance to vitamin D antiproliferative effects partly through RAS/AKT and Wnt/β-catenin signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CYP24A1 is a mitochondrial cytochrome P450 that initiates catabolic inactivation of vitamin D metabolites, controlling local and systemic availability of active 1,25(OH)2D3 [#0, #20]. A single human enzyme reconstituted with adrenodoxin/adrenodoxin reductase executes the complete multi-step catabolism through dual oxidative routes—C-24 hydroxylation toward the tetranor product and C-23 hydroxylation toward lactol/lactone—on both 25(OH)D3 and 1,25(OH)2D3, whereas the rat ortholog performs little C-23 chemistry [#0]. Hydroxylation-site selection is set by the distance of C-24 from the vitamin D ring rather than from the side-chain terminus, and high-affinity substrate binding depends on the 1α- and 25-hydroxyl groups together with F-helix residue F249, which aligns the substrate for the catalytic steps [#1, #2]. The enzyme also catabolizes noncanonical substrates such as 20(OH)D3, and the terminal 26,23-lactone-forming step requires a separate CYP3A activity rather than CYP24A1 itself [#20, #21]. Transcription is driven principally by ligand-activated VDR acting through promoter-proximal VDREs that cooperate with downstream distal enhancer clusters, including a kidney-specific PTH/FGF23-responsive pCREB/CRTC2 module (C24-DS1) and a pan-tissue VDR module (C24-DS2); PTH suppresses transcription by dismissing CBP from these distal enhancers, defining a coactivator-exchange mechanism for renal vitamin D homeostasis [#9, #10, #12, #13]. Expression is further tuned by Ras/MAP-kinase signaling (ERK1/2–RXRα and ERK5–Ets-1), CK2, NF-κB, progesterone receptor, IRES-mediated translation under inflammation, chromatin remodeling by LSH, and miR-125b-dependent post-transcriptional repression [#3, #7, #12, #19, #26]. Physiologically, CYP24A1 governs local 1,25(OH)2D availability in tissues such as the mammary gland during development and contributes to FGF23-driven phosphate-wasting bone disease [#28, #30]. Recessive loss-of-function mutations cause idiopathic infantile hypercalcemia through failure to catabolize active vitamin D metabolites, and CYP24A1 overexpression in cancers confers resistance to vitamin D antiproliferative effects, in part through RAS/AKT and Wnt/β-catenin signaling [#8, #33, #34].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that a single human enzyme, not a set of distinct hydroxylases, performs the entire multi-step vitamin D catabolic cascade via two parallel oxidative pathways, resolving how vitamin D metabolites are fully inactivated.\",\n      \"evidence\": \"Recombinant E. coli expression with adrenodoxin/adrenodoxin reductase reconstitution and HPLC-MS metabolite identification, comparing human and rat enzyme\",\n      \"pmids\": [\"11012668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the structural basis for the human-specific C-23 pathway activity\", \"No structure of the enzyme-substrate complex\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Determined that hydroxylation-site selection is governed by distance of C-24 from the vitamin D ring, explaining the regiochemistry of CYP24-mediated oxidation versus CYP27.\",\n      \"evidence\": \"Cell-based enzyme assays with side-chain-homologated substrates and HPLC/GC-MS product identification\",\n      \"pmids\": [\"7622489\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; no atomic-resolution active-site model\", \"Did not test the full panel of physiological substrates\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified the F-helix residue F249 and the 1α/25-hydroxyls as the key determinants of substrate alignment and high-affinity binding, mapping catalytic competence onto specific residues and substrate features.\",\n      \"evidence\": \"Recombinant rat CYP24A1 purification with spectral binding (Kd), kinetics, and site-directed mutagenesis at F249\",\n      \"pmids\": [\"15111121\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Performed in rat enzyme; human-specific residue dependencies not fully mapped\", \"No crystal structure confirming F249 positioning\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed that ligand-activated CYP24 induction requires Ras-dependent MAP-kinase phosphorylation of nuclear receptor partners, linking signaling to vitamin D transcriptional output.\",\n      \"evidence\": \"Promoter-luciferase assays with dominant-negative kinases, phosphosite mutagenesis of RXRα(S260) and Ets-1(T38), Co-IP and kinase assays\",\n      \"pmids\": [\"12048211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Promoter-reporter system may not reflect endogenous chromatin context\", \"Species differences in MAPK-responsive elements not resolved here\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Probed whether xenobiotic receptor PXR induces CYP24 to explain drug effects on vitamin D, but the two reports reached opposite conclusions about PXR's role.\",\n      \"evidence\": \"Promoter-luciferase, PXR transfection, human hepatocyte mRNA and enzyme activity, in vivo treatment (induction report) versus reporter assays, PXR-KO mice and human biopsies (contradicting report)\",\n      \"pmids\": [\"15630458\", \"16691293\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct contradiction between studies unresolved\", \"Tissue- and species-specific PXR effects not reconciled\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated direct pharmacological inhibition of CYP24A1 enzyme activity extends 1,25(OH)2D3 half-life and antiproliferative signaling, establishing the enzyme as a druggable target.\",\n      \"evidence\": \"Noncompetitive enzyme kinetics in isolated DU145 mitochondria with genistein, plus VDR and growth readouts\",\n      \"pmids\": [\"15955619\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; selectivity for CYP24A1 over other CYPs not fully established\", \"In vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified post-transcriptional control of CYP24A1 by miR-125b, adding a layer of regulation relevant to its overexpression in cancer.\",\n      \"evidence\": \"3'-UTR reporter assays with gain/loss of miR-125b, endogenous Western blots, and breast cancer tissue immunohistochemistry\",\n      \"pmids\": [\"19570947\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal contribution of miR-125b loss to tumor CYP24A1 elevation not tested in vivo\", \"Other 3'-UTR regulators not surveyed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established CYP24A1 as the disease gene for idiopathic infantile hypercalcemia, directly tying loss of vitamin D catabolism to a human Mendelian phenotype.\",\n      \"evidence\": \"Candidate-gene sequencing of patient cohorts with functional expression of mutant enzymes in a mammalian system\",\n      \"pmids\": [\"21675912\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype-phenotype severity correlations not fully defined\", \"Heterozygote contributions not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mapped the cis-regulatory architecture of Cyp24a1 to proximal VDREs plus novel downstream-distal enhancers and C/EBPβ occupancy, moving beyond a simple proximal-promoter model.\",\n      \"evidence\": \"ChIP-chip/ChIP-seq in cells and mouse tissues with luciferase reporters\",\n      \"pmids\": [\"22179019\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional requirement of individual enhancers in vivo not yet tested at this stage\", \"Tissue-specific enhancer usage undefined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated by in vivo enhancer deletion that a kidney-specific PTH/FGF23-responsive cluster and a pan-tissue VDR cluster differentially control Cyp24a1, dissecting hormonal versus ligand inputs.\",\n      \"evidence\": \"ChIP-seq and clustered enhancer deletion mouse models with PTH/FGF23/1,25(OH)2D3 challenge; reciprocal Cyp27b1 submodule deletions\",\n      \"pmids\": [\"31439663\", \"31629064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human enhancer conservation and function not directly established\", \"Precise transcription-factor occupancy dynamics within clusters not fully resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the coactivator-exchange mechanism by which PTH suppresses Cyp24a1—dismissing CBP from distal enhancers while recruiting pCREB/CRTC2 to Cyp27b1—and showed SIK inhibition mimics PTH.\",\n      \"evidence\": \"In vivo kidney ChIP-seq for pCREB/CBP/CRTC2 after PTH, FGF23, 1,25(OH)2D3, and SIK inhibitor treatment\",\n      \"pmids\": [\"36183832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration of physical looping linking enhancers to promoter in kidney not shown\", \"Human translation of SIK/CRTC2 axis untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established cooperative interaction between proximal VDREs and downstream enhancers in vivo, showing proximal VDRE integrity is required for VDR loading across the locus and for ligand induction but not PTH suppression.\",\n      \"evidence\": \"In vivo VDRE mutagenesis in mice with VDR/pCREB ChIP-seq and hormonal challenge\",\n      \"pmids\": [\"39363152\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of long-range VDRE-enhancer cooperation not structurally resolved\", \"Residual FGF23 induction pathway not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Used Cyp24a1-knockout rats to confirm the enzyme is responsible for the bulk of 25(OH)D3 metabolite production and to assign the terminal 26,23-lactone step to CYP3A rather than CYP24A1.\",\n      \"evidence\": \"CRISPR/Cas9 KO rats with plasma metabolite profiling, recombinant CYP enzyme assays, and ketoconazole inhibition\",\n      \"pmids\": [\"33865853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contribution of CYP3A in humans not quantified\", \"Tissue-specific metabolite handling not dissected\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Broadened the substrate scope of CYP24A1 to noncanonical 20(OH)D3 derivatives, including C23-C24 bond cleavage, showing the enzyme processes alternative vitamin D species.\",\n      \"evidence\": \"In vitro recombinant rat and human enzyme assays with NMR/HRMS product identification and kinetics\",\n      \"pmids\": [\"25727742\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological abundance/relevance of these substrates not established\", \"Lower catalytic efficiency relative to canonical substrates limits inference\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated a tissue-developmental role: CYP24A1 modulates local 1,25(OH)2D availability to permit mammary epithelial proliferation during puberty and pregnancy.\",\n      \"evidence\": \"Mammary-specific conditional Cyp24a1 knockout with whole-mount analysis, proliferation/apoptosis markers, and in vitro 1,25(OH)2D3 sensitivity\",\n      \"pmids\": [\"30654105\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream proliferative effectors not identified\", \"Whether this generalizes to other epithelial tissues unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked CYP24 activity to FGF23-driven phosphate-wasting bone disease, showing genetic or pharmacological loss of CYP24 rescues rachitic bone in two disease models.\",\n      \"evidence\": \"Cyp24-null crosses with Hyp and FGF23R176Q mice plus CTA102 inhibitor treatment, with bone histomorphometry\",\n      \"pmids\": [\"26784541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting CYP24 metabolites to bone mineralization not fully resolved\", \"Human therapeutic translation not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Implicated CYP24A1 in cancer signaling and ferroptosis sensitivity through Ca2+/MAPK control and chromatin-remodeling/Wnt circuitry, framing it as both oncogenic effector and regulatory node.\",\n      \"evidence\": \"SQLE manipulation with metabolomics and xenografts; NF-κB-driven induction with β-catenin reporters and siRNA; LSH/USP11 Co-IP, ChIP, and ferroptosis assays; lung adenocarcinoma gain/loss with RAS/pAKT readouts and xenografts\",\n      \"pmids\": [\"34268906\", \"36255661\", \"37414755\", \"27793774\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RAS/Wnt links rest on protein-level changes without direct biochemical interaction\", \"Causality among CYP24A1, Ca2+, and MAPK/Wnt not fully ordered\", \"Single-lab studies per mechanism\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the human enzyme's active-site architecture enforces dual C-23/C-24 pathway selection and how distal enhancer cooperation is structurally organized at the human locus remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of human CYP24A1-substrate complex in the corpus\", \"Human enhancer-promoter looping mechanism not directly demonstrated\", \"PXR regulation of human CYP24 remains contradictory\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 1, 20, 21]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [6, 0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 20, 8]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [9, 10, 12, 13]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}