{"gene":"DKK4","run_date":"2026-04-28T17:46:02","timeline":{"discoveries":[{"year":2018,"finding":"Dkk4 consists of two independent folded cysteine-rich domains (CRD1 and CRD2) joined by a highly flexible linker. CRD1 has significant structural homology to CRD2, pointing to gene duplication events. CRD2 mediates high-affinity binding to LRP6 E1E2 region and Kremen1 (Krm1) extracellular domain, while the N-terminal region alone binds LRP6 E1E2 with only moderate affinity via a conserved NXI(R/K) motif but does not interact with Krm proteins. Dkk and Krm family proteins function synergistically to inhibit Wnt signaling.","method":"NMR structure determination, biophysical binding assays, mutagenesis, functional Wnt signaling assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — atomic-resolution structure plus binding assays plus functional validation in a single rigorous study","pmids":["29925589"],"is_preprint":false},{"year":2016,"finding":"Dkk4 selectively inhibits a subset of Wnts and is itself inactivated by proteolytic cleavage. Intact Dkk4 inhibits meibomian gland (MG) extension, but the cleaved form progressively accumulates during MG development coinciding with increased Wnt activity. Elevation of Lrp6 eliminates Dkk4-mediated inhibition, and both Dkk4 and Lrp6 are direct Eda targets during MG induction.","method":"Transgenic mouse overexpression, organotypic culture, Lrp6 overexpression rescue experiments, biochemical detection of cleaved vs. intact Dkk4","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal in vivo and in vitro methods with functional consequences; proteolytic cleavage as a novel regulatory mechanism","pmids":["27864382"],"is_preprint":false},{"year":2008,"finding":"Dkk4 is a direct transcriptional target of the Eda-A1/Edar signaling pathway and is the most highly induced gene in microarray profiling of Edar-activated embryonic skin. Dkk4 and Lrp4 co-localize with Edar in ectodermal placodes; their residual expression in eda−/− placodes is dependent on prior Wnt activity. Eda-A1 thus unexpectedly induces Wnt antagonists (Dkk4, Lrp4) as part of fine-tuning placode signaling.","method":"Microarray profiling of eda−/− embryonic skin explants treated with recombinant Eda-A1, in situ hybridization, NF-κB pathway genetic analysis","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — microarray with multiple validation methods; replicated in genetic mutant context","pmids":["18508042"],"is_preprint":false},{"year":2010,"finding":"Dkk4, a Wnt antagonist, regulates an Eda-independent pathway for secondary hair follicle development in mice. A Dkk4 transgene malforms secondary hairs without affecting primary hairs, and when introduced into Tabby (Eda−/y) mice blocks secondary follicle induction entirely. The Dkk4-regulated secondary hair pathway, like the Eda-dependent primary hair pathway, involves selective activation of Shh.","method":"Transgenic mouse overexpression of Dkk4 in wild-type and Tabby backgrounds, histological and molecular analysis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in multiple mouse backgrounds with clear subtype-specific phenotypic readout","pmids":["20386733"],"is_preprint":false},{"year":2012,"finding":"TFAP2E directly regulates DKK4 expression; hypermethylation of TFAP2E silences TFAP2E, leading to elevated DKK4. Colorectal cancer cell lines overexpressing DKK4 show increased chemoresistance specifically to fluorouracil but not irinotecan or oxaliplatin, demonstrating that TFAP2E-dependent resistance is mechanistically mediated through DKK4.","method":"Methylation-specific analysis, gene overexpression in cell lines, cell viability assays, multiple clinical patient cohorts","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 2 — functional overexpression assays combined with epigenetic mechanism and large clinical validation; replicated across cohorts","pmids":["22216841"],"is_preprint":false},{"year":2012,"finding":"DKK4 acts as a negative regulator of the Wnt/β-catenin pathway in hepatocellular carcinoma. Ectopic DKK4 expression attenuates β-catenin–responsive luciferase activity, decreases β-catenin and cyclin D1 protein levels, inhibits cell proliferation and migration, and reduces tumor xenograft growth. Proteasome inhibition masks the β-catenin–reducing effect of DKK4, indicating DKK4 promotes proteasomal degradation of β-catenin.","method":"Luciferase reporter assay, stable overexpression cell lines, xenograft mouse model, proteasome inhibitor experiments, immunohistochemistry","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal functional assays plus in vivo model; proteasome rescue experiment defines mechanism","pmids":["22249261"],"is_preprint":false},{"year":2012,"finding":"Restoration of full-length APC in SW480 colon cancer cells induces secretion of DKK4 via exosomes. APC restoration reduces DKK4 promoter methylation and downregulates DNMT-3a, establishing a mechanism by which APC controls extracellular Wnt antagonism through epigenetic regulation of DKK4 and exosomal secretion.","method":"Comparative proteomics of exosomes, RT-PCR, immunoblotting, immunogold electron microscopy, methylation-specific PCR","journal":"Electrophoresis","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods in a single lab; exosomal secretion mechanism is novel but not independently replicated","pmids":["22740476"],"is_preprint":false},{"year":2016,"finding":"In hepatocellular carcinoma, high glucose conditions suppress DKK4 expression, leading to loss of Wnt/β-catenin pathway inhibition, enhanced β-catenin accumulation, and increased cell proliferation at G0/G1/S transition. Exogenous recombinant DKK4 protein rescues the proliferative effect caused by DKK4 shRNA knockdown under normoglycemia.","method":"shRNA knockdown, recombinant protein rescue, cell cycle analysis, xenograft mouse model under high-glucose conditions","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — recombinant protein rescue plus in vivo model, single lab","pmids":["27272409"],"is_preprint":false},{"year":2019,"finding":"DLX3 promotes osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing DKK4 expression through increasing histone H3 lysine 27 trimethylation (H3K27me3) at the DKK4 promoter, thereby activating Wnt/β-catenin signaling.","method":"ChIP-qPCR, lentiviral overexpression/knockdown, RT-qPCR, Western blotting, alkaline phosphatase assay, alizarin red staining","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP directly links H3K27me3 at DKK4 promoter to DLX3 activity, single lab with multiple methods","pmids":["31202458"],"is_preprint":false},{"year":2022,"finding":"DKK4 inhibits colorectal cancer metastasis through a negative feedback mechanism: Wnt3a/LiCl induces DKK4 expression, and DKK4 in turn represses Wnt/β-catenin signaling by suppressing FZD6 and AKT2/s552-β-catenin phosphorylation, forming a Wnt3a/DKK4/AKT/s552-β-catenin regulatory axis.","method":"RNA-seq after DKK4 knockdown, luciferase reporter assays, Transwell assays, subcutaneous and metastatic mouse models, quantitative PCR","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — RNA-seq plus functional assays plus in vivo models in single lab; pathway mechanism defined by multiple approaches","pmids":["36181792"],"is_preprint":false},{"year":2024,"finding":"DKK4 secreted from colorectal cancer cells inactivates β-catenin in stromal fibroblasts, inducing formation of stress fibre-containing fibroblasts and myofibroblasts, which restricts primary tumour expansion but enhances CRC metastasis. Chemical inhibition of β-catenin (MSAB) phenocopies this pro-metastatic effect, placing DKK4-mediated paracrine Wnt inhibition as the mechanism driving fibroblast reprogramming and metastasis.","method":"Cell co-culture, mouse CRC xenograft models, β-catenin chemical inhibitor (MSAB), fibroblast transformation assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo paracrine mechanism established; single lab with multiple approaches","pmids":["38519641"],"is_preprint":false},{"year":2017,"finding":"DKK4 knockdown in docetaxel-resistant NSCLC (A549/DTX) cells promotes inhibition of cell growth, reduces colony formation and invasion, and enhances docetaxel-induced apoptosis (caspase 3 activation, BCL-2 inhibition), possibly through activation of JNK-related signaling. DKK4 overexpression in parental A549 cells increases docetaxel resistance.","method":"shRNA knockdown, overexpression, MTT assay, flow cytometry for apoptosis, Transwell invasion assay, Western blotting for caspase-3/BCL-2/JNK","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 3 — functional assays with pathway marker readout, single lab","pmids":["28981599"],"is_preprint":false},{"year":2023,"finding":"LARP1 stabilizes DKK4 mRNA by competitively interacting with PABPC1 to prevent DKK4 mRNA from BTG2-dependent deadenylation and degradation, leading to increased DKK4 protein, enhanced β-catenin nuclear import, and hepatoblastoma progression. O-GlcNAcylation of LARP1 at Ser672 strengthens its binding to circCLNS1A and protects LARP1 from ubiquitination, upstream of this mechanism.","method":"Co-immunoprecipitation, RNA immunoprecipitation, RNA pulldown, mRNA stability assays, poly(A)-tail length assays, RNA-seq","journal":"Clinical and translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal biochemical assays establishing DKK4 mRNA stabilization mechanism, single lab","pmids":["37070251"],"is_preprint":false},{"year":2025,"finding":"METTL14 promotes m6A methylation of DKK4 mRNA, upregulating DKK4 expression in docetaxel-resistant lung cancer cells. Elevated DKK4 enhances docetaxel resistance and promotes M2 macrophage polarization, while METTL14 knockdown reduces DKK4 expression and reverses these effects.","method":"MeRIP assay, RT-qPCR, Western blotting, MTT assay, flow cytometry, EdU, mouse xenograft model","journal":"Journal of biochemical and molecular toxicology","confidence":"Medium","confidence_rationale":"Tier 2 — MeRIP directly demonstrates m6A on DKK4 mRNA; functional rescue experiments; single lab","pmids":["41208390"],"is_preprint":false},{"year":2017,"finding":"Knockdown of lncRNA-H19 in osteoblasts leads to upregulation of Dkk4, inhibition of Wnt signaling, and reduced osteogenic function; knocking down Dkk4 greatly reverses these effects, placing Dkk4 downstream of H19 in Wnt-dependent osteogenesis.","method":"RNA sequencing, bioinformatic pathway analysis, siRNA knockdown of H19 and Dkk4 in UMR106 cells, RT-qPCR, Western blotting","journal":"Orthopaedic surgery","confidence":"Low","confidence_rationale":"Tier 3 — epistasis by sequential knockdown in cell line, single lab, limited mechanistic detail on direct H19-DKK4 interaction","pmids":["28447380"],"is_preprint":false}],"current_model":"DKK4 is a secreted, two-CRD Wnt antagonist whose CRD2 binds LRP6 and Kremen1 with high affinity to inhibit canonical Wnt/β-catenin signaling; it is transcriptionally regulated by TFAP2E, Eda/Edar, and DLX3 (via H3K27me3), post-transcriptionally stabilized by LARP1 and m6A methylation (METTL14), and inactivated by proteolytic cleavage, with its secretion (including via exosomes downstream of APC) enabling paracrine reprogramming of stromal fibroblasts to promote cancer metastasis, while also playing critical roles in ectodermal appendage patterning and chemoresistance."},"narrative":{"teleology":[{"year":2008,"claim":"Identification of DKK4 as a direct Eda/Edar transcriptional target established how Wnt antagonism is embedded within ectodermal placode signaling, resolving the paradox that a Wnt-dependent pathway simultaneously induces its own inhibitor.","evidence":"Microarray profiling of eda−/− embryonic skin explants treated with recombinant Eda-A1 plus in situ hybridization","pmids":["18508042"],"confidence":"High","gaps":["Direct promoter binding by Eda-activated transcription factors not shown for DKK4","Whether NF-κB directly drives DKK4 transcription or acts through intermediaries is unresolved"]},{"year":2010,"claim":"Demonstrating that DKK4 overexpression selectively blocks secondary but not primary hair follicle induction revealed a Wnt-dependent, Eda-independent pathway for hair subtype specification mediated by DKK4.","evidence":"Transgenic Dkk4 overexpression in wild-type and Tabby (Eda−/y) mouse backgrounds with histological analysis","pmids":["20386733"],"confidence":"High","gaps":["Endogenous Dkk4 loss-of-function phenotype in hair follicle patterning not tested","Downstream effectors beyond Shh not characterized"]},{"year":2012,"claim":"Multiple studies converged to define DKK4 as a functional Wnt/β-catenin pathway inhibitor: DKK4 promotes proteasomal β-catenin degradation in hepatocellular carcinoma, confers fluorouracil chemoresistance through TFAP2E-dependent epigenetic regulation in colorectal cancer, and is secreted via exosomes upon APC restoration.","evidence":"Luciferase reporters, xenograft models, proteasome inhibitor rescue (HCC); TFAP2E methylation analysis and cell viability assays (CRC); exosome proteomics and methylation-specific PCR (APC/SW480)","pmids":["22249261","22216841","22740476"],"confidence":"High","gaps":["Identity of the protease(s) responsible for β-catenin degradation downstream of DKK4 not defined","Exosomal DKK4 secretion mechanism not independently replicated","Whether TFAP2E directly represses DKK4 transcription or acts indirectly was not resolved at this stage"]},{"year":2016,"claim":"Discovery that DKK4 is inactivated by proteolytic cleavage during meibomian gland development introduced post-translational regulation as a mechanism controlling DKK4 activity in vivo, explaining how Wnt signaling is progressively de-repressed.","evidence":"Transgenic mouse overexpression, organotypic culture, biochemical detection of cleaved vs. intact DKK4, Lrp6 overexpression rescue","pmids":["27864382"],"confidence":"High","gaps":["Protease responsible for DKK4 cleavage not identified","Whether proteolytic inactivation operates in non-ectodermal tissues is unknown"]},{"year":2018,"claim":"Atomic-resolution NMR structure of DKK4 revealed the two-CRD architecture, assigned LRP6 and Kremen1 binding to CRD2, and identified the NXI(R/K) motif in the N-terminal region as a secondary LRP6-binding element, providing the structural basis for synergistic Wnt inhibition.","evidence":"NMR structure determination, biophysical binding assays, mutagenesis, functional Wnt signaling assays","pmids":["29925589"],"confidence":"High","gaps":["No co-crystal structure of DKK4 in complex with LRP6 or Kremen","Structural basis for selective inhibition of specific Wnt ligands not resolved"]},{"year":2019,"claim":"Demonstrating that DLX3 suppresses DKK4 via H3K27me3 deposition at the DKK4 promoter linked chromatin-level regulation to DKK4 expression control in osteogenic differentiation.","evidence":"ChIP-qPCR for H3K27me3 at DKK4 promoter, lentiviral overexpression/knockdown of DLX3, osteogenic differentiation assays in bone marrow mesenchymal stem cells","pmids":["31202458"],"confidence":"Medium","gaps":["Whether DLX3 directly recruits a H3K27 methyltransferase (e.g. EZH2) to DKK4 is not shown","Single lab finding without independent replication"]},{"year":2022,"claim":"Identification of a Wnt3a/DKK4/AKT/s552-β-catenin negative feedback axis revealed that DKK4 inhibits colorectal cancer metastasis by suppressing FZD6 and AKT2-mediated β-catenin phosphorylation, extending the mechanism beyond canonical LRP6 antagonism.","evidence":"RNA-seq after DKK4 knockdown, luciferase reporters, Transwell assays, subcutaneous and metastatic mouse models","pmids":["36181792"],"confidence":"Medium","gaps":["Whether DKK4 directly interacts with FZD6 or acts indirectly through LRP6 is unclear","AKT2/β-catenin mechanism not validated with kinase-dead mutants"]},{"year":2023,"claim":"Revealing that LARP1 stabilizes DKK4 mRNA by blocking BTG2-dependent deadenylation established a post-transcriptional control layer for DKK4 expression in hepatoblastoma, linking O-GlcNAcylation of LARP1 to DKK4 protein output.","evidence":"RNA immunoprecipitation, RNA pulldown, poly(A)-tail length assays, mRNA stability assays in hepatoblastoma cell lines","pmids":["37070251"],"confidence":"Medium","gaps":["Direct binding site of LARP1 on DKK4 mRNA not mapped","Whether LARP1-DKK4 mRNA stabilization occurs in non-hepatoblastoma contexts is unknown"]},{"year":2024,"claim":"Demonstration that tumor-secreted DKK4 reprograms stromal fibroblasts into pro-metastatic myofibroblasts by paracrine β-catenin inactivation resolved the apparent paradox of a tumor suppressor gene promoting metastasis through non-cell-autonomous effects.","evidence":"CRC-fibroblast co-culture, mouse xenograft models, β-catenin chemical inhibitor (MSAB) phenocopy experiments","pmids":["38519641"],"confidence":"Medium","gaps":["Fibroblast subtypes most responsive to DKK4 not defined","Whether DKK4-driven fibroblast reprogramming operates at the metastatic niche or only in primary tumors is not established"]},{"year":2025,"claim":"Identification of METTL14-mediated m6A methylation of DKK4 mRNA as a driver of docetaxel resistance and M2 macrophage polarization added epitranscriptomic regulation as a further post-transcriptional control of DKK4 levels.","evidence":"MeRIP assay demonstrating m6A on DKK4 mRNA, METTL14 knockdown/rescue, mouse xenograft model in lung cancer","pmids":["41208390"],"confidence":"Medium","gaps":["Specific m6A reader protein mediating DKK4 mRNA stabilization/translation not identified","Whether m6A regulation of DKK4 operates outside chemoresistant lung cancer is unknown"]},{"year":null,"claim":"Key unresolved questions include the identity of the protease(s) that cleave and inactivate DKK4, the structural basis of DKK4's selective inhibition of specific Wnt ligands, and whether the paracrine fibroblast-reprogramming mechanism operates across cancer types or at metastatic sites.","evidence":"","pmids":[],"confidence":"High","gaps":["Protease identity for DKK4 cleavage unknown","No co-crystal structure of DKK4-LRP6 or DKK4-Kremen complex","In vivo loss-of-function models (full knockout) in cancer context not reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,5,9]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,5,10]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,6,10]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,5,7,9,10]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,2,3]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,11,13]}],"complexes":[],"partners":["LRP6","KRM1","LARP1","METTL14","PABPC1","BTG2"],"other_free_text":[]},"mechanistic_narrative":"DKK4 is a secreted Wnt antagonist that inhibits canonical Wnt/β-catenin signaling through high-affinity binding of its CRD2 domain to LRP6 and Kremen1, promoting proteasomal degradation of β-catenin and suppressing downstream targets including cyclin D1 and FZD6 [PMID:29925589, PMID:22249261, PMID:36181792]. DKK4 is transcriptionally induced by Eda/Edar signaling in ectodermal placodes and repressed by DLX3-mediated H3K27me3 deposition at its promoter, while its mRNA is post-transcriptionally stabilized by LARP1-dependent deadenylation protection and METTL14-mediated m6A methylation [PMID:18508042, PMID:31202458, PMID:37070251, PMID:41208390]. DKK4 activity is terminated by proteolytic cleavage during meibomian gland development, and its biological output is context-dependent: in colorectal cancer, tumor-secreted DKK4 inactivates β-catenin in stromal fibroblasts, reprogramming them into myofibroblasts that restrict primary tumor growth but enhance metastasis [PMID:27864382, PMID:38519641]. Elevated DKK4 confers chemoresistance to fluorouracil in colorectal cancer and to docetaxel in non-small cell lung cancer [PMID:22216841, PMID:28981599]."},"prefetch_data":{"uniprot":{"accession":"Q9UBT3","full_name":"Dickkopf-related protein 4","aliases":[],"length_aa":224,"mass_kda":24.9,"function":"Antagonizes canonical Wnt signaling by inhibiting LRP5/6 interaction with Wnt and by forming a ternary complex with the transmembrane protein KREMEN that promotes internalization of LRP5/6. DKKs play an important role in vertebrate development, where they locally inhibit Wnt regulated processes such as antero-posterior axial patterning, limb development, somitogenesis and eye formation. In the adult, Dkks are implicated in bone formation and bone disease, cancer and Alzheimer disease (By similarity)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9UBT3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DKK4","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DKK4","total_profiled":1310},"omim":[{"mim_id":"613303","title":"AlkB HOMOLOG 5, RNA DEMETHYLASE; ALKBH5","url":"https://www.omim.org/entry/613303"},{"mim_id":"605417","title":"DICKKOPF WNT SIGNALING PATHWAY INHIBITOR 4; DKK4","url":"https://www.omim.org/entry/605417"},{"mim_id":"605416","title":"DICKKOPF WNT SIGNALING PATHWAY INHIBITOR 3; DKK3","url":"https://www.omim.org/entry/605416"},{"mim_id":"605415","title":"DICKKOPF WNT SIGNALING PATHWAY INHIBITOR 2; DKK2","url":"https://www.omim.org/entry/605415"},{"mim_id":"605189","title":"DICKKOPF WNT SIGNALING PATHWAY INHIBITOR 1; DKK1","url":"https://www.omim.org/entry/605189"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"esophagus","ntpm":4.6},{"tissue":"intestine","ntpm":2.3}],"url":"https://www.proteinatlas.org/search/DKK4"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9UBT3","domains":[{"cath_id":"2.10.80.10","chopping":"144-180_189-207_215-221","consensus_level":"high","plddt":90.6417,"start":144,"end":221}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBT3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBT3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBT3-F1-predicted_aligned_error_v6.png","plddt_mean":73.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DKK4","jax_strain_url":"https://www.jax.org/strain/search?query=DKK4"},"sequence":{"accession":"Q9UBT3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UBT3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UBT3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBT3"}},"corpus_meta":[{"pmid":"22216841","id":"PMC_22216841","title":"TFAP2E-DKK4 and chemoresistance in colorectal cancer.","date":"2012","source":"The New England journal of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/22216841","citation_count":138,"is_preprint":false},{"pmid":"18508042","id":"PMC_18508042","title":"Identification of dkk4 as a target of Eda-A1/Edar pathway reveals an unexpected role of ectodysplasin as inhibitor of Wnt signalling in ectodermal placodes.","date":"2008","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/18508042","citation_count":97,"is_preprint":false},{"pmid":"22249261","id":"PMC_22249261","title":"Dickkopf 4 (DKK4) acts on Wnt/β-catenin pathway by influencing β-catenin in hepatocellular carcinoma.","date":"2012","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/22249261","citation_count":46,"is_preprint":false},{"pmid":"28447380","id":"PMC_28447380","title":"LncRNA-H19 Modulates Wnt/β-catenin Signaling by Targeting Dkk4 in Hindlimb Unloaded Rat.","date":"2017","source":"Orthopaedic 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DKK-4.","date":"2012","source":"Electrophoresis","url":"https://pubmed.ncbi.nlm.nih.gov/22740476","citation_count":35,"is_preprint":false},{"pmid":"20386733","id":"PMC_20386733","title":"Dkk4 and Eda regulate distinctive developmental mechanisms for subtypes of mouse hair.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20386733","citation_count":35,"is_preprint":false},{"pmid":"16077958","id":"PMC_16077958","title":"Comparative genomics on DKK2 and DKK4 orthologs.","date":"2005","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/16077958","citation_count":31,"is_preprint":false},{"pmid":"29925589","id":"PMC_29925589","title":"Structural and functional analysis of Dickkopf 4 (Dkk4): New insights into Dkk evolution and regulation of Wnt signaling by Dkk and Kremen proteins.","date":"2018","source":"The Journal of biological 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biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36181792","citation_count":10,"is_preprint":false},{"pmid":"28981599","id":"PMC_28981599","title":"DKK4-knockdown enhances chemosensitivity of A549/DTX cells to docetaxel.","date":"2017","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/28981599","citation_count":9,"is_preprint":false},{"pmid":"33346226","id":"PMC_33346226","title":"Methylation Assessment of Two DKK2 and DKK4 Genes in Oral Squamous Cell Carcinoma Patients.","date":"2020","source":"Iranian journal of public health","url":"https://pubmed.ncbi.nlm.nih.gov/33346226","citation_count":4,"is_preprint":false},{"pmid":"21341386","id":"PMC_21341386","title":"[Association of the schizophrenia susceptible gene DKK4 with brain volume in Chinese populations].","date":"2011","source":"Dong wu xue yan jiu = Zoological research","url":"https://pubmed.ncbi.nlm.nih.gov/21341386","citation_count":3,"is_preprint":false},{"pmid":"38519641","id":"PMC_38519641","title":"Colorectal cancer cells secreting DKK4 transform fibroblasts to promote tumour metastasis.","date":"2024","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/38519641","citation_count":1,"is_preprint":false},{"pmid":"37435631","id":"PMC_37435631","title":"Generation and characterization of a Dkk4-Cre knock-in mouse line.","date":"2023","source":"Genesis (New York, N.Y. : 2000)","url":"https://pubmed.ncbi.nlm.nih.gov/37435631","citation_count":0,"is_preprint":false},{"pmid":"23479175","id":"PMC_23479175","title":"Novel SNPs in the exon region of bovine DKK4 gene and their association with body measurement traits in Qinchuan cattle.","date":"2013","source":"Genetics and molecular research : GMR","url":"https://pubmed.ncbi.nlm.nih.gov/23479175","citation_count":0,"is_preprint":false},{"pmid":"41208390","id":"PMC_41208390","title":"METTL14 Mediates Malignant Progression and Docetaxel Resistance of Lung Cancer by Regulating DKK4 Expression Through m6A Methylation Modification.","date":"2025","source":"Journal of biochemical and molecular toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/41208390","citation_count":0,"is_preprint":false},{"pmid":"39506574","id":"PMC_39506574","title":"Correlation and Prediction of IL-10Ra and DKK-4 Plasma Levels in Patients with Calcium Oxalate Urolithiasis.","date":"2024","source":"Clinical laboratory","url":"https://pubmed.ncbi.nlm.nih.gov/39506574","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15520,"output_tokens":4032,"usd":0.05352},"stage2":{"model":"claude-opus-4-6","input_tokens":7519,"output_tokens":3082,"usd":0.171967},"total_usd":0.225487,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"Dkk4 consists of two independent folded cysteine-rich domains (CRD1 and CRD2) joined by a highly flexible linker. CRD1 has significant structural homology to CRD2, pointing to gene duplication events. CRD2 mediates high-affinity binding to LRP6 E1E2 region and Kremen1 (Krm1) extracellular domain, while the N-terminal region alone binds LRP6 E1E2 with only moderate affinity via a conserved NXI(R/K) motif but does not interact with Krm proteins. Dkk and Krm family proteins function synergistically to inhibit Wnt signaling.\",\n      \"method\": \"NMR structure determination, biophysical binding assays, mutagenesis, functional Wnt signaling assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — atomic-resolution structure plus binding assays plus functional validation in a single rigorous study\",\n      \"pmids\": [\"29925589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Dkk4 selectively inhibits a subset of Wnts and is itself inactivated by proteolytic cleavage. Intact Dkk4 inhibits meibomian gland (MG) extension, but the cleaved form progressively accumulates during MG development coinciding with increased Wnt activity. Elevation of Lrp6 eliminates Dkk4-mediated inhibition, and both Dkk4 and Lrp6 are direct Eda targets during MG induction.\",\n      \"method\": \"Transgenic mouse overexpression, organotypic culture, Lrp6 overexpression rescue experiments, biochemical detection of cleaved vs. intact Dkk4\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal in vivo and in vitro methods with functional consequences; proteolytic cleavage as a novel regulatory mechanism\",\n      \"pmids\": [\"27864382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Dkk4 is a direct transcriptional target of the Eda-A1/Edar signaling pathway and is the most highly induced gene in microarray profiling of Edar-activated embryonic skin. Dkk4 and Lrp4 co-localize with Edar in ectodermal placodes; their residual expression in eda−/− placodes is dependent on prior Wnt activity. Eda-A1 thus unexpectedly induces Wnt antagonists (Dkk4, Lrp4) as part of fine-tuning placode signaling.\",\n      \"method\": \"Microarray profiling of eda−/− embryonic skin explants treated with recombinant Eda-A1, in situ hybridization, NF-κB pathway genetic analysis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — microarray with multiple validation methods; replicated in genetic mutant context\",\n      \"pmids\": [\"18508042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Dkk4, a Wnt antagonist, regulates an Eda-independent pathway for secondary hair follicle development in mice. A Dkk4 transgene malforms secondary hairs without affecting primary hairs, and when introduced into Tabby (Eda−/y) mice blocks secondary follicle induction entirely. The Dkk4-regulated secondary hair pathway, like the Eda-dependent primary hair pathway, involves selective activation of Shh.\",\n      \"method\": \"Transgenic mouse overexpression of Dkk4 in wild-type and Tabby backgrounds, histological and molecular analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in multiple mouse backgrounds with clear subtype-specific phenotypic readout\",\n      \"pmids\": [\"20386733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TFAP2E directly regulates DKK4 expression; hypermethylation of TFAP2E silences TFAP2E, leading to elevated DKK4. Colorectal cancer cell lines overexpressing DKK4 show increased chemoresistance specifically to fluorouracil but not irinotecan or oxaliplatin, demonstrating that TFAP2E-dependent resistance is mechanistically mediated through DKK4.\",\n      \"method\": \"Methylation-specific analysis, gene overexpression in cell lines, cell viability assays, multiple clinical patient cohorts\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional overexpression assays combined with epigenetic mechanism and large clinical validation; replicated across cohorts\",\n      \"pmids\": [\"22216841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DKK4 acts as a negative regulator of the Wnt/β-catenin pathway in hepatocellular carcinoma. Ectopic DKK4 expression attenuates β-catenin–responsive luciferase activity, decreases β-catenin and cyclin D1 protein levels, inhibits cell proliferation and migration, and reduces tumor xenograft growth. Proteasome inhibition masks the β-catenin–reducing effect of DKK4, indicating DKK4 promotes proteasomal degradation of β-catenin.\",\n      \"method\": \"Luciferase reporter assay, stable overexpression cell lines, xenograft mouse model, proteasome inhibitor experiments, immunohistochemistry\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal functional assays plus in vivo model; proteasome rescue experiment defines mechanism\",\n      \"pmids\": [\"22249261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Restoration of full-length APC in SW480 colon cancer cells induces secretion of DKK4 via exosomes. APC restoration reduces DKK4 promoter methylation and downregulates DNMT-3a, establishing a mechanism by which APC controls extracellular Wnt antagonism through epigenetic regulation of DKK4 and exosomal secretion.\",\n      \"method\": \"Comparative proteomics of exosomes, RT-PCR, immunoblotting, immunogold electron microscopy, methylation-specific PCR\",\n      \"journal\": \"Electrophoresis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in a single lab; exosomal secretion mechanism is novel but not independently replicated\",\n      \"pmids\": [\"22740476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In hepatocellular carcinoma, high glucose conditions suppress DKK4 expression, leading to loss of Wnt/β-catenin pathway inhibition, enhanced β-catenin accumulation, and increased cell proliferation at G0/G1/S transition. Exogenous recombinant DKK4 protein rescues the proliferative effect caused by DKK4 shRNA knockdown under normoglycemia.\",\n      \"method\": \"shRNA knockdown, recombinant protein rescue, cell cycle analysis, xenograft mouse model under high-glucose conditions\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — recombinant protein rescue plus in vivo model, single lab\",\n      \"pmids\": [\"27272409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DLX3 promotes osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing DKK4 expression through increasing histone H3 lysine 27 trimethylation (H3K27me3) at the DKK4 promoter, thereby activating Wnt/β-catenin signaling.\",\n      \"method\": \"ChIP-qPCR, lentiviral overexpression/knockdown, RT-qPCR, Western blotting, alkaline phosphatase assay, alizarin red staining\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP directly links H3K27me3 at DKK4 promoter to DLX3 activity, single lab with multiple methods\",\n      \"pmids\": [\"31202458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DKK4 inhibits colorectal cancer metastasis through a negative feedback mechanism: Wnt3a/LiCl induces DKK4 expression, and DKK4 in turn represses Wnt/β-catenin signaling by suppressing FZD6 and AKT2/s552-β-catenin phosphorylation, forming a Wnt3a/DKK4/AKT/s552-β-catenin regulatory axis.\",\n      \"method\": \"RNA-seq after DKK4 knockdown, luciferase reporter assays, Transwell assays, subcutaneous and metastatic mouse models, quantitative PCR\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RNA-seq plus functional assays plus in vivo models in single lab; pathway mechanism defined by multiple approaches\",\n      \"pmids\": [\"36181792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DKK4 secreted from colorectal cancer cells inactivates β-catenin in stromal fibroblasts, inducing formation of stress fibre-containing fibroblasts and myofibroblasts, which restricts primary tumour expansion but enhances CRC metastasis. Chemical inhibition of β-catenin (MSAB) phenocopies this pro-metastatic effect, placing DKK4-mediated paracrine Wnt inhibition as the mechanism driving fibroblast reprogramming and metastasis.\",\n      \"method\": \"Cell co-culture, mouse CRC xenograft models, β-catenin chemical inhibitor (MSAB), fibroblast transformation assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo paracrine mechanism established; single lab with multiple approaches\",\n      \"pmids\": [\"38519641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"DKK4 knockdown in docetaxel-resistant NSCLC (A549/DTX) cells promotes inhibition of cell growth, reduces colony formation and invasion, and enhances docetaxel-induced apoptosis (caspase 3 activation, BCL-2 inhibition), possibly through activation of JNK-related signaling. DKK4 overexpression in parental A549 cells increases docetaxel resistance.\",\n      \"method\": \"shRNA knockdown, overexpression, MTT assay, flow cytometry for apoptosis, Transwell invasion assay, Western blotting for caspase-3/BCL-2/JNK\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional assays with pathway marker readout, single lab\",\n      \"pmids\": [\"28981599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LARP1 stabilizes DKK4 mRNA by competitively interacting with PABPC1 to prevent DKK4 mRNA from BTG2-dependent deadenylation and degradation, leading to increased DKK4 protein, enhanced β-catenin nuclear import, and hepatoblastoma progression. O-GlcNAcylation of LARP1 at Ser672 strengthens its binding to circCLNS1A and protects LARP1 from ubiquitination, upstream of this mechanism.\",\n      \"method\": \"Co-immunoprecipitation, RNA immunoprecipitation, RNA pulldown, mRNA stability assays, poly(A)-tail length assays, RNA-seq\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical assays establishing DKK4 mRNA stabilization mechanism, single lab\",\n      \"pmids\": [\"37070251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL14 promotes m6A methylation of DKK4 mRNA, upregulating DKK4 expression in docetaxel-resistant lung cancer cells. Elevated DKK4 enhances docetaxel resistance and promotes M2 macrophage polarization, while METTL14 knockdown reduces DKK4 expression and reverses these effects.\",\n      \"method\": \"MeRIP assay, RT-qPCR, Western blotting, MTT assay, flow cytometry, EdU, mouse xenograft model\",\n      \"journal\": \"Journal of biochemical and molecular toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MeRIP directly demonstrates m6A on DKK4 mRNA; functional rescue experiments; single lab\",\n      \"pmids\": [\"41208390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Knockdown of lncRNA-H19 in osteoblasts leads to upregulation of Dkk4, inhibition of Wnt signaling, and reduced osteogenic function; knocking down Dkk4 greatly reverses these effects, placing Dkk4 downstream of H19 in Wnt-dependent osteogenesis.\",\n      \"method\": \"RNA sequencing, bioinformatic pathway analysis, siRNA knockdown of H19 and Dkk4 in UMR106 cells, RT-qPCR, Western blotting\",\n      \"journal\": \"Orthopaedic surgery\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — epistasis by sequential knockdown in cell line, single lab, limited mechanistic detail on direct H19-DKK4 interaction\",\n      \"pmids\": [\"28447380\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DKK4 is a secreted, two-CRD Wnt antagonist whose CRD2 binds LRP6 and Kremen1 with high affinity to inhibit canonical Wnt/β-catenin signaling; it is transcriptionally regulated by TFAP2E, Eda/Edar, and DLX3 (via H3K27me3), post-transcriptionally stabilized by LARP1 and m6A methylation (METTL14), and inactivated by proteolytic cleavage, with its secretion (including via exosomes downstream of APC) enabling paracrine reprogramming of stromal fibroblasts to promote cancer metastasis, while also playing critical roles in ectodermal appendage patterning and chemoresistance.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"DKK4 is a secreted Wnt antagonist that inhibits canonical Wnt/β-catenin signaling through high-affinity binding of its CRD2 domain to LRP6 and Kremen1, promoting proteasomal degradation of β-catenin and suppressing downstream targets including cyclin D1 and FZD6 [PMID:29925589, PMID:22249261, PMID:36181792]. DKK4 is transcriptionally induced by Eda/Edar signaling in ectodermal placodes and repressed by DLX3-mediated H3K27me3 deposition at its promoter, while its mRNA is post-transcriptionally stabilized by LARP1-dependent deadenylation protection and METTL14-mediated m6A methylation [PMID:18508042, PMID:31202458, PMID:37070251, PMID:41208390]. DKK4 activity is terminated by proteolytic cleavage during meibomian gland development, and its biological output is context-dependent: in colorectal cancer, tumor-secreted DKK4 inactivates β-catenin in stromal fibroblasts, reprogramming them into myofibroblasts that restrict primary tumor growth but enhance metastasis [PMID:27864382, PMID:38519641]. Elevated DKK4 confers chemoresistance to fluorouracil in colorectal cancer and to docetaxel in non-small cell lung cancer [PMID:22216841, PMID:28981599].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Identification of DKK4 as a direct Eda/Edar transcriptional target established how Wnt antagonism is embedded within ectodermal placode signaling, resolving the paradox that a Wnt-dependent pathway simultaneously induces its own inhibitor.\",\n      \"evidence\": \"Microarray profiling of eda−/− embryonic skin explants treated with recombinant Eda-A1 plus in situ hybridization\",\n      \"pmids\": [\"18508042\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct promoter binding by Eda-activated transcription factors not shown for DKK4\", \"Whether NF-κB directly drives DKK4 transcription or acts through intermediaries is unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrating that DKK4 overexpression selectively blocks secondary but not primary hair follicle induction revealed a Wnt-dependent, Eda-independent pathway for hair subtype specification mediated by DKK4.\",\n      \"evidence\": \"Transgenic Dkk4 overexpression in wild-type and Tabby (Eda−/y) mouse backgrounds with histological analysis\",\n      \"pmids\": [\"20386733\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous Dkk4 loss-of-function phenotype in hair follicle patterning not tested\", \"Downstream effectors beyond Shh not characterized\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Multiple studies converged to define DKK4 as a functional Wnt/β-catenin pathway inhibitor: DKK4 promotes proteasomal β-catenin degradation in hepatocellular carcinoma, confers fluorouracil chemoresistance through TFAP2E-dependent epigenetic regulation in colorectal cancer, and is secreted via exosomes upon APC restoration.\",\n      \"evidence\": \"Luciferase reporters, xenograft models, proteasome inhibitor rescue (HCC); TFAP2E methylation analysis and cell viability assays (CRC); exosome proteomics and methylation-specific PCR (APC/SW480)\",\n      \"pmids\": [\"22249261\", \"22216841\", \"22740476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the protease(s) responsible for β-catenin degradation downstream of DKK4 not defined\", \"Exosomal DKK4 secretion mechanism not independently replicated\", \"Whether TFAP2E directly represses DKK4 transcription or acts indirectly was not resolved at this stage\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery that DKK4 is inactivated by proteolytic cleavage during meibomian gland development introduced post-translational regulation as a mechanism controlling DKK4 activity in vivo, explaining how Wnt signaling is progressively de-repressed.\",\n      \"evidence\": \"Transgenic mouse overexpression, organotypic culture, biochemical detection of cleaved vs. intact DKK4, Lrp6 overexpression rescue\",\n      \"pmids\": [\"27864382\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease responsible for DKK4 cleavage not identified\", \"Whether proteolytic inactivation operates in non-ectodermal tissues is unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Atomic-resolution NMR structure of DKK4 revealed the two-CRD architecture, assigned LRP6 and Kremen1 binding to CRD2, and identified the NXI(R/K) motif in the N-terminal region as a secondary LRP6-binding element, providing the structural basis for synergistic Wnt inhibition.\",\n      \"evidence\": \"NMR structure determination, biophysical binding assays, mutagenesis, functional Wnt signaling assays\",\n      \"pmids\": [\"29925589\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-crystal structure of DKK4 in complex with LRP6 or Kremen\", \"Structural basis for selective inhibition of specific Wnt ligands not resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrating that DLX3 suppresses DKK4 via H3K27me3 deposition at the DKK4 promoter linked chromatin-level regulation to DKK4 expression control in osteogenic differentiation.\",\n      \"evidence\": \"ChIP-qPCR for H3K27me3 at DKK4 promoter, lentiviral overexpression/knockdown of DLX3, osteogenic differentiation assays in bone marrow mesenchymal stem cells\",\n      \"pmids\": [\"31202458\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DLX3 directly recruits a H3K27 methyltransferase (e.g. EZH2) to DKK4 is not shown\", \"Single lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identification of a Wnt3a/DKK4/AKT/s552-β-catenin negative feedback axis revealed that DKK4 inhibits colorectal cancer metastasis by suppressing FZD6 and AKT2-mediated β-catenin phosphorylation, extending the mechanism beyond canonical LRP6 antagonism.\",\n      \"evidence\": \"RNA-seq after DKK4 knockdown, luciferase reporters, Transwell assays, subcutaneous and metastatic mouse models\",\n      \"pmids\": [\"36181792\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DKK4 directly interacts with FZD6 or acts indirectly through LRP6 is unclear\", \"AKT2/β-catenin mechanism not validated with kinase-dead mutants\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealing that LARP1 stabilizes DKK4 mRNA by blocking BTG2-dependent deadenylation established a post-transcriptional control layer for DKK4 expression in hepatoblastoma, linking O-GlcNAcylation of LARP1 to DKK4 protein output.\",\n      \"evidence\": \"RNA immunoprecipitation, RNA pulldown, poly(A)-tail length assays, mRNA stability assays in hepatoblastoma cell lines\",\n      \"pmids\": [\"37070251\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding site of LARP1 on DKK4 mRNA not mapped\", \"Whether LARP1-DKK4 mRNA stabilization occurs in non-hepatoblastoma contexts is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstration that tumor-secreted DKK4 reprograms stromal fibroblasts into pro-metastatic myofibroblasts by paracrine β-catenin inactivation resolved the apparent paradox of a tumor suppressor gene promoting metastasis through non-cell-autonomous effects.\",\n      \"evidence\": \"CRC-fibroblast co-culture, mouse xenograft models, β-catenin chemical inhibitor (MSAB) phenocopy experiments\",\n      \"pmids\": [\"38519641\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Fibroblast subtypes most responsive to DKK4 not defined\", \"Whether DKK4-driven fibroblast reprogramming operates at the metastatic niche or only in primary tumors is not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of METTL14-mediated m6A methylation of DKK4 mRNA as a driver of docetaxel resistance and M2 macrophage polarization added epitranscriptomic regulation as a further post-transcriptional control of DKK4 levels.\",\n      \"evidence\": \"MeRIP assay demonstrating m6A on DKK4 mRNA, METTL14 knockdown/rescue, mouse xenograft model in lung cancer\",\n      \"pmids\": [\"41208390\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific m6A reader protein mediating DKK4 mRNA stabilization/translation not identified\", \"Whether m6A regulation of DKK4 operates outside chemoresistant lung cancer is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the protease(s) that cleave and inactivate DKK4, the structural basis of DKK4's selective inhibition of specific Wnt ligands, and whether the paracrine fibroblast-reprogramming mechanism operates across cancer types or at metastatic sites.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease identity for DKK4 cleavage unknown\", \"No co-crystal structure of DKK4-LRP6 or DKK4-Kremen complex\", \"In vivo loss-of-function models (full knockout) in cancer context not reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 5, 9]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 6, 10]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016055\", \"supporting_discovery_ids\": [0, 5, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 5, 7, 9, 10]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 11, 13]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"LRP6\",\n      \"KRM1\",\n      \"LARP1\",\n      \"METTL14\",\n      \"PABPC1\",\n      \"BTG2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}