{"gene":"P4HA1","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2018,"finding":"P4HA1 modulates alpha-ketoglutarate (α-KG) and succinate levels, thereby reducing proline hydroxylation on HIF-1α and enhancing its stability in cancer cells. This P4HA1/HIF-1 axis promotes cancer cell stemness, decreases oxidative phosphorylation and reactive oxygen species (ROS) levels, and drives chemoresistance in triple-negative breast cancer.","method":"shRNA knockdown of P4HA1 in TNBC cells; metabolic profiling of α-KG and succinate; HIF-1α stability assays; xenograft and patient-derived models with docetaxel/doxorubicin treatment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal functional assays (KD + metabolite measurement + HIF-1α stability), multiple orthogonal methods, in vitro and in vivo validation in a single focused study","pmids":["30367042"],"is_preprint":false},{"year":2019,"finding":"Pyruvate uptake by breast cancer cells induces production of α-ketoglutarate, which activates P4HA-mediated collagen hydroxylation in the lung metastatic niche, promoting metastatic growth. Inhibition of pyruvate metabolism impairs collagen hydroxylation and lung metastasis.","method":"Metabolic tracing of pyruvate to α-KG; P4HA activity assays; inhibition of pyruvate metabolism in mouse metastasis models; functional ECM remodeling assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — metabolic tracing, P4HA activity measurement, multiple in vivo mouse models, mechanistic link from nutrient to enzyme activity to ECM remodeling established","pmids":["30814728"],"is_preprint":false},{"year":2014,"finding":"P4HA1 catalyzes the formation of 4-hydroxyproline in procollagen chains essential for their three-dimensional folding. In prostate cancer, P4HA1 overexpression drives tumor progression and invasion via upregulation of MMP1; invasive properties of P4HA1-overexpressing cells are reversed by MMP1 blockade. P4HA1 expression is regulated by miR-124, which is in turn repressed by EZH2 and CtBP1.","method":"shRNA/overexpression of P4HA1 in prostate cancer cells; MMP1 rescue experiment; miR-124 overexpression; EZH2/CtBP1 manipulation; chick CAM assay and mouse xenograft","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined pathway (MMP1 rescue), in vivo validation, miRNA regulatory axis, but single lab","pmids":["25115393"],"is_preprint":false},{"year":2025,"finding":"In clear cell renal cell carcinoma (ccRCC) with pVHL deficiency, P4HA1 (and P4HA2) are required for HIF-1α translation and HIF-2α transcription and translation through a pVHL-independent mechanism that is regulated in part by P4HA1/2-driven collagen production.","method":"P4HA1/2 knockdown in pVHL-deficient ccRCC cells; measurement of HIF-1α/HIF-2α protein and mRNA levels; mechanistic dissection separating pVHL-dependent and -independent pathways","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional KD with defined molecular readouts (HIF-1α/2α translation/transcription), novel pVHL-independent mechanism, but single preprint study, not yet peer-reviewed","pmids":["bio_10.1101_2025.09.14.676157"],"is_preprint":true},{"year":2026,"finding":"In form-deprivation myopia, decreased scleral P4HA1 expression reduces proline hydroxylation and hydroxyproline content, leading to collagen disorganization and axial elongation. AAV8-mediated restoration of P4HA1 expression rescued hydroxyproline levels, increased COL1A1, reduced MMP2, reinstated TIMP2, and improved collagen density and alignment, thereby mitigating axial elongation. Pharmacological inhibition of P4HA (1,4-DPCA) in fibroblasts reduced hydroxyproline and collagen production.","method":"AAV8-P4HA1 overexpression in guinea pig FDM model; metabolomics (targeted/untargeted); pharmacological P4HA inhibition (1,4-DPCA) in primary fibroblasts; collagen ultrastructure assessment","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function rescue experiment in vivo with multiple orthogonal readouts (metabolomics, gene expression, structural), plus pharmacological inhibition in vitro; single lab","pmids":["42165645"],"is_preprint":false},{"year":2017,"finding":"In cardiac fibroblasts deprived of ascorbate, P4HA1 protein levels rise along with intracellular procollagen accumulation. Despite being necessary for triple-helical procollagen formation, elevated P4HA1 (and P4HA2) levels were NOT responsible for the early increased procollagen secretion upon ascorbate re-addition.","method":"Cardiac fibroblast culture ± ascorbate; Western blotting for P4HA1, P4HA2, procollagen; P4HA2 overexpression; pulse-chase secretion assays","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein quantification, overexpression experiments, and negative finding robustly established across mouse and rat fibroblasts; single lab","pmids":["28923350"],"is_preprint":false},{"year":1997,"finding":"The human P4HA gene was mapped to chromosome 10q by FISH, determined to be telomeric to COL13A1 with a tail-to-tail transcriptional orientation and ~550 kb separating the two genes.","method":"High-resolution fluorescence in situ hybridization (FISH) on mechanically stretched chromosomes, interphase nuclei, and fiber FISH","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct chromosomal mapping by multiple FISH approaches, single lab but orthogonal resolution methods","pmids":["9417920"],"is_preprint":false},{"year":2025,"finding":"CHDH-mediated changes in histone H3 trimethylation upregulate P4HA1 (along with P4HA2/3) expression, which stabilizes collagen I and increases IL17RB expression, promoting downstream c-Jun activation and colorectal cancer metastasis. P4HA inhibitors abolished CHDH-mediated CRC cell metastasis in vitro and in vivo.","method":"CHDH knockdown/overexpression; P4HA inhibitor treatment; xenograft mouse model; histone methylation analysis; collagen I and IL17RB/c-Jun pathway assays","journal":"MedComm","confidence":"Low","confidence_rationale":"Tier 3 / Weak — P4HA1 is one of three family members studied together without isoform-specific mechanistic dissection; pathway placement relies on co-manipulation rather than P4HA1-specific rescue","pmids":["39764560"],"is_preprint":false},{"year":2024,"finding":"P4HA1 knockout in mouse mammary glands disrupts a unique subcluster of basal epithelial cells that exhibits concurrent activation of stem cell development and inflammatory response pathways, indicating P4HA1 regulates the interplay between stemness and inflammation in mammary tissue.","method":"P4HA1 knockout mice; single-cell RNA sequencing; SCENIC gene regulatory network inference; experimental validation of network predictions","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single-cell transcriptomic network inference with experimental validation stated but not detailed in abstract; preprint, single lab","pmids":["bio_10.1101_2024.11.05.622022"],"is_preprint":true}],"current_model":"P4HA1 is the catalytic α1 subunit of collagen prolyl-4-hydroxylase that hydroxylates proline residues in procollagen to enable triple-helical folding; beyond collagen biosynthesis, P4HA1 competitively consumes α-ketoglutarate and elevates succinate, thereby inhibiting HIF prolyl hydroxylases and stabilizing HIF-1α in a pVHL-dependent manner, and in pVHL-deficient ccRCC additionally controls HIF-1α/2α at the level of translation/transcription independently of pVHL, collectively promoting cancer cell stemness, chemoresistance, invasion (partly via MMP1 upregulation), and metastatic niche remodeling."},"narrative":{"mechanistic_narrative":"P4HA1 is the catalytic subunit of collagen prolyl-4-hydroxylase that converts proline to 4-hydroxyproline in procollagen chains, an α-ketoglutarate-dependent reaction essential for triple-helical collagen folding and extracellular matrix integrity [PMID:25115393, PMID:42165645]. Loss of scleral P4HA1 reduces hydroxyproline content and collagen organization, while AAV8-mediated restoration rescues hydroxyproline levels, increases COL1A1, normalizes MMP2/TIMP2 balance, and restores collagen density, demonstrating a direct causal role in collagen maturation [PMID:42165645]. Through its consumption of α-ketoglutarate and accumulation of succinate, P4HA1 reduces prolyl hydroxylation of HIF-1α and stabilizes it, linking the enzyme to a metabolic program that promotes cancer cell stemness, suppresses oxidative phosphorylation and ROS, and drives chemoresistance [PMID:30367042]. Tumor cell nutrient uptake feeds this axis: pyruvate-derived α-ketoglutarate activates P4HA-mediated collagen hydroxylation in the lung metastatic niche to support metastatic outgrowth [PMID:30814728]. In prostate cancer, P4HA1 overexpression drives invasion through MMP1 upregulation and is controlled by a miR-124/EZH2/CtBP1 regulatory axis [PMID:25115393]. Beyond [PMID:30367042], [PMID:30814728], [PMID:25115393] and [PMID:42165645], isoform-specific mechanisms in pVHL-independent HIF control and mammary stemness remain incompletely characterized in the available corpus.","teleology":[{"year":1997,"claim":"Establishing the genomic position of the human P4HA gene anchored it physically in the genome and to a neighboring collagen gene, providing a foundation for its locus-level study.","evidence":"high-resolution FISH on stretched chromosomes, interphase nuclei, and fiber FISH","pmids":["9417920"],"confidence":"Medium","gaps":["Does not address enzymatic function or regulation","No link to disease or expression control"]},{"year":2014,"claim":"Confirming P4HA1's hydroxylation of procollagen proline and linking its overexpression to MMP1-driven invasion connected the enzyme's biochemical role to a tumor-progression phenotype and an upstream miRNA regulatory circuit.","evidence":"shRNA/overexpression in prostate cancer cells with MMP1 rescue, miR-124/EZH2/CtBP1 manipulation, chick CAM and mouse xenograft","pmids":["25115393"],"confidence":"Medium","gaps":["Single lab","MMP1 mechanism downstream of P4HA1 not fully dissected","Restricted to prostate cancer context"]},{"year":2017,"claim":"Testing whether elevated P4HA1 governs procollagen secretion clarified that, while required for triple-helical formation, P4HA1 levels do not drive early secretion kinetics after ascorbate restoration.","evidence":"cardiac fibroblast culture ± ascorbate with Western blotting, P4HA2 overexpression, and pulse-chase secretion assays","pmids":["28923350"],"confidence":"Medium","gaps":["Negative finding limited to early secretion window","Does not resolve what does control the secretion rate"]},{"year":2018,"claim":"Demonstrating that P4HA1 shifts α-KG/succinate balance to stabilize HIF-1α reframed the enzyme as a metabolic regulator of cancer stemness and chemoresistance beyond collagen synthesis.","evidence":"shRNA knockdown in TNBC cells with metabolite profiling, HIF-1α stability assays, and xenograft/PDX chemotherapy models","pmids":["30367042"],"confidence":"High","gaps":["Direct measurement of HIF prolyl hydroxylase inhibition by succinate not isolated","Generalizability beyond TNBC unestablished"]},{"year":2019,"claim":"Tracing nutrient flux to enzyme activity showed pyruvate-derived α-KG fuels P4HA-mediated collagen hydroxylation in the metastatic niche, establishing a nutrient-to-ECM remodeling axis.","evidence":"metabolic tracing of pyruvate to α-KG, P4HA activity assays, pyruvate metabolism inhibition in mouse metastasis models","pmids":["30814728"],"confidence":"High","gaps":["P4HA1-specific versus P4HA2 contribution not separated","Mechanism of niche collagen remodeling on metastatic cells incompletely defined"]},{"year":2026,"claim":"Gain-of-function rescue in a myopia model causally tied P4HA1-dependent proline hydroxylation to scleral collagen organization and ocular axial length.","evidence":"AAV8-P4HA1 overexpression in guinea pig form-deprivation myopia model, metabolomics, gene expression, and collagen ultrastructure, plus 1,4-DPCA inhibition in fibroblasts","pmids":["42165645"],"confidence":"Medium","gaps":["Single lab","Mechanism linking P4HA1 to MMP2/TIMP2 regulation not resolved","Pharmacological inhibitor not P4HA1-selective"]},{"year":2025,"claim":"Probing pVHL-deficient ccRCC indicated P4HA1/2 control HIF-1α/2α at translation and transcription independently of pVHL, extending its HIF regulation to a degradation-independent layer.","evidence":"P4HA1/2 knockdown in pVHL-deficient ccRCC cells with HIF-1α/2α protein and mRNA measurement (preprint)","pmids":["bio_10.1101_2025.09.14.676157"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","P4HA1 versus P4HA2 contributions not separated","Mechanism connecting collagen production to HIF translation/transcription undefined"]},{"year":null,"claim":"How P4HA1-specific (versus P4HA2/3) catalytic activity is mechanistically coupled to transcriptional/translational HIF control and to tissue stemness programs remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No isoform-specific rescue separating P4HA1 from family members","No structural model of the catalytic mechanism in the corpus","Causal link between collagen output and HIF regulation undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[2,4]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[2,4]}],"localization":[],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[1,2,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1]}],"complexes":["collagen prolyl-4-hydroxylase"],"partners":["P4HA2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P13674","full_name":"Prolyl 4-hydroxylase subunit alpha-1","aliases":["Procollagen-proline,2-oxoglutarate-4-dioxygenase subunit alpha-1"],"length_aa":534,"mass_kda":61.0,"function":"Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins","subcellular_location":"Endoplasmic reticulum lumen","url":"https://www.uniprot.org/uniprotkb/P13674/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/P4HA1","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SF3B4","stoichiometry":4.0},{"gene":"COPA","stoichiometry":0.2},{"gene":"COPE","stoichiometry":0.2},{"gene":"CPSF6","stoichiometry":0.2},{"gene":"DNAJC8","stoichiometry":0.2},{"gene":"MED9","stoichiometry":0.2},{"gene":"NCKAP1","stoichiometry":0.2},{"gene":"RBM12","stoichiometry":0.2},{"gene":"RBM14","stoichiometry":0.2},{"gene":"RBM39","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/P4HA1","total_profiled":1310},"omim":[{"mim_id":"614584","title":"PROLYL 4-HYDROXYLASE, TRANSMEMBRANE; P4HTM","url":"https://www.omim.org/entry/614584"},{"mim_id":"609976","title":"HYPOXIA-INDUCIBLE FACTOR 3, ALPHA SUBUNIT; HIF3A","url":"https://www.omim.org/entry/609976"},{"mim_id":"608987","title":"PROCOLLAGEN-PROLINE, 2-OXOGLUTARATE-4-DIOXYGENASE, ALPHA SUBUNIT, ISOFORM 3; P4HA3","url":"https://www.omim.org/entry/608987"},{"mim_id":"606229","title":"ARGONAUTE RISC COMPONENT 2; AGO2","url":"https://www.omim.org/entry/606229"},{"mim_id":"600608","title":"PROCOLLAGEN-PROLINE, 2-OXOGLUTARATE-4-DIOXYGENASE, ALPHA SUBUNIT, ISOFORM 2; P4HA2","url":"https://www.omim.org/entry/600608"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"},{"location":"Mitochondria","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/P4HA1"},"hgnc":{"alias_symbol":["C-P4Halpha(I)"],"prev_symbol":["P4HA"]},"alphafold":{"accession":"P13674","domains":[{"cath_id":"1.25.40.10","chopping":"123-258","consensus_level":"high","plddt":95.6708,"start":123,"end":258},{"cath_id":"2.60.120.620","chopping":"298-517","consensus_level":"high","plddt":93.316,"start":298,"end":517},{"cath_id":"1.10.287","chopping":"20-118","consensus_level":"high","plddt":93.5958,"start":20,"end":118}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P13674","model_url":"https://alphafold.ebi.ac.uk/files/AF-P13674-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P13674-F1-predicted_aligned_error_v6.png","plddt_mean":89.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=P4HA1","jax_strain_url":"https://www.jax.org/strain/search?query=P4HA1"},"sequence":{"accession":"P13674","fasta_url":"https://rest.uniprot.org/uniprotkb/P13674.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P13674/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P13674"}},"corpus_meta":[{"pmid":"24383403","id":"PMC_24383403","title":"Prolyl-4-hydroxylase 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This P4HA1/HIF-1 axis promotes cancer cell stemness, decreases oxidative phosphorylation and reactive oxygen species (ROS) levels, and drives chemoresistance in triple-negative breast cancer.\",\n      \"method\": \"shRNA knockdown of P4HA1 in TNBC cells; metabolic profiling of α-KG and succinate; HIF-1α stability assays; xenograft and patient-derived models with docetaxel/doxorubicin treatment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal functional assays (KD + metabolite measurement + HIF-1α stability), multiple orthogonal methods, in vitro and in vivo validation in a single focused study\",\n      \"pmids\": [\"30367042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Pyruvate uptake by breast cancer cells induces production of α-ketoglutarate, which activates P4HA-mediated collagen hydroxylation in the lung metastatic niche, promoting metastatic growth. Inhibition of pyruvate metabolism impairs collagen hydroxylation and lung metastasis.\",\n      \"method\": \"Metabolic tracing of pyruvate to α-KG; P4HA activity assays; inhibition of pyruvate metabolism in mouse metastasis models; functional ECM remodeling assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — metabolic tracing, P4HA activity measurement, multiple in vivo mouse models, mechanistic link from nutrient to enzyme activity to ECM remodeling established\",\n      \"pmids\": [\"30814728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"P4HA1 catalyzes the formation of 4-hydroxyproline in procollagen chains essential for their three-dimensional folding. In prostate cancer, P4HA1 overexpression drives tumor progression and invasion via upregulation of MMP1; invasive properties of P4HA1-overexpressing cells are reversed by MMP1 blockade. P4HA1 expression is regulated by miR-124, which is in turn repressed by EZH2 and CtBP1.\",\n      \"method\": \"shRNA/overexpression of P4HA1 in prostate cancer cells; MMP1 rescue experiment; miR-124 overexpression; EZH2/CtBP1 manipulation; chick CAM assay and mouse xenograft\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined pathway (MMP1 rescue), in vivo validation, miRNA regulatory axis, but single lab\",\n      \"pmids\": [\"25115393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In clear cell renal cell carcinoma (ccRCC) with pVHL deficiency, P4HA1 (and P4HA2) are required for HIF-1α translation and HIF-2α transcription and translation through a pVHL-independent mechanism that is regulated in part by P4HA1/2-driven collagen production.\",\n      \"method\": \"P4HA1/2 knockdown in pVHL-deficient ccRCC cells; measurement of HIF-1α/HIF-2α protein and mRNA levels; mechanistic dissection separating pVHL-dependent and -independent pathways\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional KD with defined molecular readouts (HIF-1α/2α translation/transcription), novel pVHL-independent mechanism, but single preprint study, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.09.14.676157\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In form-deprivation myopia, decreased scleral P4HA1 expression reduces proline hydroxylation and hydroxyproline content, leading to collagen disorganization and axial elongation. AAV8-mediated restoration of P4HA1 expression rescued hydroxyproline levels, increased COL1A1, reduced MMP2, reinstated TIMP2, and improved collagen density and alignment, thereby mitigating axial elongation. Pharmacological inhibition of P4HA (1,4-DPCA) in fibroblasts reduced hydroxyproline and collagen production.\",\n      \"method\": \"AAV8-P4HA1 overexpression in guinea pig FDM model; metabolomics (targeted/untargeted); pharmacological P4HA inhibition (1,4-DPCA) in primary fibroblasts; collagen ultrastructure assessment\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function rescue experiment in vivo with multiple orthogonal readouts (metabolomics, gene expression, structural), plus pharmacological inhibition in vitro; single lab\",\n      \"pmids\": [\"42165645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In cardiac fibroblasts deprived of ascorbate, P4HA1 protein levels rise along with intracellular procollagen accumulation. Despite being necessary for triple-helical procollagen formation, elevated P4HA1 (and P4HA2) levels were NOT responsible for the early increased procollagen secretion upon ascorbate re-addition.\",\n      \"method\": \"Cardiac fibroblast culture ± ascorbate; Western blotting for P4HA1, P4HA2, procollagen; P4HA2 overexpression; pulse-chase secretion assays\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein quantification, overexpression experiments, and negative finding robustly established across mouse and rat fibroblasts; single lab\",\n      \"pmids\": [\"28923350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The human P4HA gene was mapped to chromosome 10q by FISH, determined to be telomeric to COL13A1 with a tail-to-tail transcriptional orientation and ~550 kb separating the two genes.\",\n      \"method\": \"High-resolution fluorescence in situ hybridization (FISH) on mechanically stretched chromosomes, interphase nuclei, and fiber FISH\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct chromosomal mapping by multiple FISH approaches, single lab but orthogonal resolution methods\",\n      \"pmids\": [\"9417920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CHDH-mediated changes in histone H3 trimethylation upregulate P4HA1 (along with P4HA2/3) expression, which stabilizes collagen I and increases IL17RB expression, promoting downstream c-Jun activation and colorectal cancer metastasis. P4HA inhibitors abolished CHDH-mediated CRC cell metastasis in vitro and in vivo.\",\n      \"method\": \"CHDH knockdown/overexpression; P4HA inhibitor treatment; xenograft mouse model; histone methylation analysis; collagen I and IL17RB/c-Jun pathway assays\",\n      \"journal\": \"MedComm\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — P4HA1 is one of three family members studied together without isoform-specific mechanistic dissection; pathway placement relies on co-manipulation rather than P4HA1-specific rescue\",\n      \"pmids\": [\"39764560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"P4HA1 knockout in mouse mammary glands disrupts a unique subcluster of basal epithelial cells that exhibits concurrent activation of stem cell development and inflammatory response pathways, indicating P4HA1 regulates the interplay between stemness and inflammation in mammary tissue.\",\n      \"method\": \"P4HA1 knockout mice; single-cell RNA sequencing; SCENIC gene regulatory network inference; experimental validation of network predictions\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single-cell transcriptomic network inference with experimental validation stated but not detailed in abstract; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2024.11.05.622022\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"P4HA1 is the catalytic α1 subunit of collagen prolyl-4-hydroxylase that hydroxylates proline residues in procollagen to enable triple-helical folding; beyond collagen biosynthesis, P4HA1 competitively consumes α-ketoglutarate and elevates succinate, thereby inhibiting HIF prolyl hydroxylases and stabilizing HIF-1α in a pVHL-dependent manner, and in pVHL-deficient ccRCC additionally controls HIF-1α/2α at the level of translation/transcription independently of pVHL, collectively promoting cancer cell stemness, chemoresistance, invasion (partly via MMP1 upregulation), and metastatic niche remodeling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"P4HA1 is the catalytic subunit of collagen prolyl-4-hydroxylase that converts proline to 4-hydroxyproline in procollagen chains, an α-ketoglutarate-dependent reaction essential for triple-helical collagen folding and extracellular matrix integrity [#2, #4]. Loss of scleral P4HA1 reduces hydroxyproline content and collagen organization, while AAV8-mediated restoration rescues hydroxyproline levels, increases COL1A1, normalizes MMP2/TIMP2 balance, and restores collagen density, demonstrating a direct causal role in collagen maturation [#4]. Through its consumption of α-ketoglutarate and accumulation of succinate, P4HA1 reduces prolyl hydroxylation of HIF-1α and stabilizes it, linking the enzyme to a metabolic program that promotes cancer cell stemness, suppresses oxidative phosphorylation and ROS, and drives chemoresistance [#0]. Tumor cell nutrient uptake feeds this axis: pyruvate-derived α-ketoglutarate activates P4HA-mediated collagen hydroxylation in the lung metastatic niche to support metastatic outgrowth [#1]. In prostate cancer, P4HA1 overexpression drives invasion through MMP1 upregulation and is controlled by a miR-124/EZH2/CtBP1 regulatory axis [#2]. Beyond [#0], [#1], [#2] and [#4], isoform-specific mechanisms in pVHL-independent HIF control and mammary stemness remain incompletely characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing the genomic position of the human P4HA gene anchored it physically in the genome and to a neighboring collagen gene, providing a foundation for its locus-level study.\",\n      \"evidence\": \"high-resolution FISH on stretched chromosomes, interphase nuclei, and fiber FISH\",\n      \"pmids\": [\"9417920\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address enzymatic function or regulation\", \"No link to disease or expression control\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Confirming P4HA1's hydroxylation of procollagen proline and linking its overexpression to MMP1-driven invasion connected the enzyme's biochemical role to a tumor-progression phenotype and an upstream miRNA regulatory circuit.\",\n      \"evidence\": \"shRNA/overexpression in prostate cancer cells with MMP1 rescue, miR-124/EZH2/CtBP1 manipulation, chick CAM and mouse xenograft\",\n      \"pmids\": [\"25115393\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"MMP1 mechanism downstream of P4HA1 not fully dissected\", \"Restricted to prostate cancer context\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Testing whether elevated P4HA1 governs procollagen secretion clarified that, while required for triple-helical formation, P4HA1 levels do not drive early secretion kinetics after ascorbate restoration.\",\n      \"evidence\": \"cardiac fibroblast culture ± ascorbate with Western blotting, P4HA2 overexpression, and pulse-chase secretion assays\",\n      \"pmids\": [\"28923350\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative finding limited to early secretion window\", \"Does not resolve what does control the secretion rate\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that P4HA1 shifts α-KG/succinate balance to stabilize HIF-1α reframed the enzyme as a metabolic regulator of cancer stemness and chemoresistance beyond collagen synthesis.\",\n      \"evidence\": \"shRNA knockdown in TNBC cells with metabolite profiling, HIF-1α stability assays, and xenograft/PDX chemotherapy models\",\n      \"pmids\": [\"30367042\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct measurement of HIF prolyl hydroxylase inhibition by succinate not isolated\", \"Generalizability beyond TNBC unestablished\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Tracing nutrient flux to enzyme activity showed pyruvate-derived α-KG fuels P4HA-mediated collagen hydroxylation in the metastatic niche, establishing a nutrient-to-ECM remodeling axis.\",\n      \"evidence\": \"metabolic tracing of pyruvate to α-KG, P4HA activity assays, pyruvate metabolism inhibition in mouse metastasis models\",\n      \"pmids\": [\"30814728\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"P4HA1-specific versus P4HA2 contribution not separated\", \"Mechanism of niche collagen remodeling on metastatic cells incompletely defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Gain-of-function rescue in a myopia model causally tied P4HA1-dependent proline hydroxylation to scleral collagen organization and ocular axial length.\",\n      \"evidence\": \"AAV8-P4HA1 overexpression in guinea pig form-deprivation myopia model, metabolomics, gene expression, and collagen ultrastructure, plus 1,4-DPCA inhibition in fibroblasts\",\n      \"pmids\": [\"42165645\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Mechanism linking P4HA1 to MMP2/TIMP2 regulation not resolved\", \"Pharmacological inhibitor not P4HA1-selective\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Probing pVHL-deficient ccRCC indicated P4HA1/2 control HIF-1α/2α at translation and transcription independently of pVHL, extending its HIF regulation to a degradation-independent layer.\",\n      \"evidence\": \"P4HA1/2 knockdown in pVHL-deficient ccRCC cells with HIF-1α/2α protein and mRNA measurement (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.09.14.676157\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"P4HA1 versus P4HA2 contributions not separated\", \"Mechanism connecting collagen production to HIF translation/transcription undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How P4HA1-specific (versus P4HA2/3) catalytic activity is mechanistically coupled to transcriptional/translational HIF control and to tissue stemness programs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No isoform-specific rescue separating P4HA1 from family members\", \"No structural model of the catalytic mechanism in the corpus\", \"Causal link between collagen output and HIF regulation undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [1, 2, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\"collagen prolyl-4-hydroxylase\"],\n    \"partners\": [\"P4HA2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}