{"gene":"NTN4","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2022,"finding":"NTN4 acts as a tumor suppressor by directly binding to Wnt ligands, thereby attenuating the Wnt signaling pathway. Loss of NTN4 in mice leads to earlier tumor onset, progression, and metastasis. The protective T allele of rs11836367 increases GATA3 binding to a distal enhancer and up-regulates NTN4 expression.","method":"Co-binding assay (NTN4 binding to Wnt ligands), endogenous genome editing (enhancer reporter assays, CRISPR), mouse knockout model with tumor phenotype, enhancer-GATA3 binding assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including direct binding assay, genome editing, and in vivo mouse KO with defined phenotype in a single study","pmids":["35687692"],"is_preprint":false},{"year":2024,"finding":"Secreted NTN4 binds to integrin β1 on endometrial cancer cells, triggering the FAK/SRC signaling axis to elevate c-MYC activity, thereby maintaining cancer stem cell self-renewal. EXOSC5 augments NTN4 expression upstream of this pathway.","method":"NTN4 treatment experiments, EXOSC5 knockdown, co-immunoprecipitation/binding of NTN4 with integrin β1, pharmacological inhibition of FAK/SRC, cancer stem cell sphere assays, in vivo tumorigenicity assays","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple functional assays with receptor identification but binding validated by treatment rather than direct structural reconstitution","pmids":["38164180"],"is_preprint":false},{"year":2016,"finding":"NTN4 overexpression in breast cancer cells attenuates cell migration and invasion and suppresses EMT markers N-cadherin and vimentin; NTN4 knockdown increases migration, invasion, and EMT marker expression.","method":"NTN4-pcDNA3.1 overexpression and siRNA knockdown in breast cancer cell lines (MDA-MB-231, Hs578T), migration/invasion assays, Western blot for EMT markers","journal":"Oncology reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — reciprocal gain/loss-of-function with defined cellular phenotype and molecular readout, single lab","pmids":["27840993"],"is_preprint":false},{"year":2020,"finding":"A causal variant (rs61938093) at the NTN4 locus resides within an enhancer element that physically interacts with the NTN4 promoter; the risk allele reduces NTN4 promoter activity. NTN4 knockdown in breast cells increases cell proliferation in vitro and tumor growth in vivo.","method":"Chromatin conformation capture (enhancer-promoter physical interaction), enhancer reporter assay, NTN4 knockdown, in vitro proliferation assay, in vivo xenograft tumor growth","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (chromatin interaction, reporter assay, KD in vitro and in vivo) establishing regulatory mechanism and functional consequence","pmids":["32871102"],"is_preprint":false},{"year":2024,"finding":"CD204+ M2-like tumor-associated macrophages secrete TNF-α, which activates NF-κB/HIF-1α signaling in gastric cancer cells to upregulate miR-210, which in turn directly targets the NTN4 3'UTR to suppress NTN4 expression and promote cancer cell migration.","method":"Co-culture experiments, miRNA microarray, anti-miRNA and miRNA mimic transfection, neutralizing antibodies and pharmacological inhibitors, luciferase 3'UTR reporter assay with mutation of miR-210 binding site","journal":"Cancer immunology, immunotherapy : CII","confidence":"Medium","confidence_rationale":"Tier 2 — luciferase reporter with binding site mutation confirms direct miR-210/NTN4 interaction; pathway dissected with inhibitors; single lab","pmids":["38175202"],"is_preprint":false},{"year":2014,"finding":"miR-20a targets NTN4 and suppresses its expression in ovarian endometriosis; increased miR-20a in advanced endometriosis correlates with decreased NTN4 expression.","method":"Computational prediction of miR-20a target sites in NTN4, qRT-PCR expression analysis in patient tissues","journal":"Molecular biology reports","confidence":"Low","confidence_rationale":"Tier 3-4 — computational prediction with correlative expression data only, no direct reporter or functional rescue experiment shown","pmids":["24972566"],"is_preprint":false},{"year":2025,"finding":"Recombinant NTN4 (rh-NTN4) enhances neurite outgrowth in human iPSC-derived sensory neurons and stimulates production of pro-inflammatory cytokines (IL-6, IL-8) and chemokines (CXCL1, CXCL6, CXCL8) in synovial fibroblasts from OA patients.","method":"Recombinant NTN4 treatment of human iPSC-derived sensory neurons (neurite outgrowth assay) and synovial fibroblasts (ELISA for cytokines/chemokines)","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct functional assays with recombinant protein on human cells, but single lab without genetic rescue experiments","pmids":["40136644"],"is_preprint":false},{"year":2025,"finding":"TNF-α induces NTN4 expression in rat tenocytes in a dose-dependent manner, and exogenous NTN4 induces MMP-3 (but not MMP-1, TNF-α, or IL-6) expression and protein secretion in tenocytes, defining a TNF-α/NTN4/MMP-3 axis in tendon ECM degradation.","method":"In vivo rat rotator cuff tear model (qRT-PCR), in vitro recombinant TNF-α stimulation of primary tenocytes (qRT-PCR, ELISA), exogenous recombinant NTN4 stimulation","journal":"Cureus","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo mechanistic experiments with recombinant proteins defining a cytokine-NTN4-MMP axis; single lab","pmids":["40688916"],"is_preprint":false}],"current_model":"NTN4 (Netrin-4) is a secreted glycoprotein that functions as a tumor suppressor by directly binding Wnt ligands to attenuate Wnt signaling, suppressing EMT and cell migration/invasion; it also signals through integrin β1/FAK/SRC to regulate c-MYC and cancer stemness, promotes neurite outgrowth and neuronal sensitization, and modulates inflammatory responses in fibroblasts via IL-6/IL-8/chemokine induction, while its expression is regulated by upstream enhancer elements (controlled by GATA3 and risk-associated SNPs), miRNAs (miR-20a, miR-210), and inflammatory cytokines such as TNF-α."},"narrative":{"teleology":[{"year":2014,"claim":"Computational and correlative evidence first linked miR-20a to post-transcriptional suppression of NTN4 in endometriosis, raising the question of how NTN4 expression is regulated by miRNAs.","evidence":"Computational target prediction and qRT-PCR expression correlation in patient endometriosis tissues","pmids":["24972566"],"confidence":"Low","gaps":["No direct reporter assay or functional rescue to confirm miR-20a binding to NTN4 3′UTR","Mechanism by which NTN4 loss contributes to endometriosis pathology undefined","Not independently replicated"]},{"year":2016,"claim":"Reciprocal gain- and loss-of-function experiments established NTN4 as an inhibitor of EMT, migration, and invasion in breast cancer, defining its cellular anti-metastatic function.","evidence":"Overexpression and siRNA knockdown in MDA-MB-231 and Hs578T cells with migration/invasion assays and Western blot for N-cadherin and vimentin","pmids":["27840993"],"confidence":"Medium","gaps":["Receptor mediating anti-EMT activity not identified","No in vivo validation of EMT suppression","Downstream signaling pathway not mapped"]},{"year":2020,"claim":"Identification of a causal enhancer variant (rs61938093) that physically contacts the NTN4 promoter established the regulatory architecture controlling NTN4 expression and linked reduced NTN4 to increased breast tumor growth in vivo.","evidence":"Chromatin conformation capture, enhancer reporter assay, NTN4 knockdown with in vitro proliferation and xenograft tumor growth assays","pmids":["32871102"],"confidence":"High","gaps":["Transcription factors mediating enhancer activity at this variant not fully characterized","Whether enhancer loss phenocopies NTN4 coding deletion not tested"]},{"year":2022,"claim":"Direct binding of NTN4 to Wnt ligands revealed its molecular mechanism as a Wnt pathway antagonist, while mouse knockout confirmed its in vivo tumor-suppressive role and a second enhancer SNP (rs11836367) was linked to GATA3-dependent NTN4 upregulation.","evidence":"Co-binding assay of NTN4 with Wnt ligands, CRISPR enhancer editing, mouse NTN4 knockout with tumor and metastasis phenotyping, GATA3 binding assays","pmids":["35687692"],"confidence":"High","gaps":["Specificity for individual Wnt family members not fully delineated","Structural basis of NTN4–Wnt interaction unknown","Whether Wnt sequestration fully accounts for tumor suppression or additional receptors contribute"]},{"year":2024,"claim":"NTN4 was shown to bind integrin β1 and activate FAK/SRC/c-MYC to sustain cancer stemness in endometrial cancer, revealing a pro-tumorigenic receptor-mediated axis distinct from its Wnt-sequestering tumor-suppressive role.","evidence":"Co-immunoprecipitation of NTN4 with integrin β1, FAK/SRC pharmacological inhibition, sphere-forming and in vivo tumorigenicity assays in endometrial cancer cells","pmids":["38164180"],"confidence":"Medium","gaps":["NTN4–integrin β1 binding not validated by structural or biophysical reconstitution","Context determining whether NTN4 acts as tumor suppressor versus stemness promoter not resolved","EXOSC5-dependent NTN4 upregulation mechanism not defined"]},{"year":2024,"claim":"The TNF-α/NF-κB/HIF-1α/miR-210 axis was identified as a direct post-transcriptional silencer of NTN4 in the tumor microenvironment, explaining how macrophage-derived signals suppress NTN4 to promote cancer cell migration.","evidence":"Macrophage–cancer cell co-culture, miR-210 mimic/inhibitor transfection, luciferase 3′UTR reporter with miR-210 binding site mutation, neutralizing antibodies and pharmacological inhibitors in gastric cancer cells","pmids":["38175202"],"confidence":"Medium","gaps":["Whether miR-210-mediated NTN4 suppression is relevant in non-gastric cancer contexts untested","Quantitative contribution of miR-210 versus other NTN4-targeting miRNAs not compared"]},{"year":2025,"claim":"Functional assays with recombinant NTN4 demonstrated its dual role outside cancer: promoting neurite outgrowth in sensory neurons and inducing pro-inflammatory cytokine/chemokine production in synovial fibroblasts and MMP-3 in tenocytes, linking NTN4 to neural development and tissue inflammation/ECM remodeling.","evidence":"Recombinant NTN4 treatment of iPSC-derived sensory neurons (neurite assay), OA synovial fibroblasts (ELISA), and rat tenocytes (qRT-PCR/ELISA) with TNF-α stimulation","pmids":["40136644","40688916"],"confidence":"Medium","gaps":["Receptor(s) mediating NTN4 effects in neurons and fibroblasts not identified","Signaling pathways downstream of NTN4 in non-cancer cell types not mapped","In vivo relevance of NTN4 in joint inflammation and tendon repair not established"]},{"year":null,"claim":"Key unresolved questions include the structural basis of NTN4–Wnt and NTN4–integrin β1 interactions, the determinants of context-dependent tumor-suppressive versus stemness-promoting activity, the receptor(s) mediating NTN4 signaling in neurons and fibroblasts, and the in vivo contribution of NTN4 to inflammatory joint and tendon pathology.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal/cryo-EM structure of NTN4 or its ligand complexes","Tissue-specific receptor utilization logic unknown","No genetic models for NTN4 in inflammatory or neuronal phenotypes beyond cancer"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[1,6,7]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,6,7]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4,6]}],"complexes":[],"partners":["ITGB1","GATA3","MMP3"],"other_free_text":[]},"mechanistic_narrative":"NTN4 (Netrin-4) is a secreted glycoprotein that functions as a ligand-sequestering tumor suppressor and a context-dependent signaling molecule in neural and inflammatory biology. NTN4 directly binds Wnt ligands to attenuate Wnt signaling, and loss of NTN4 in mice accelerates tumor onset, progression, and metastasis; its expression is governed by distal enhancer elements regulated by GATA3 and breast cancer risk-associated SNPs (rs11836367, rs61938093), as well as by miR-210 downstream of TNF-α/NF-κB/HIF-1α signaling [PMID:35687692, PMID:32871102, PMID:38175202]. NTN4 suppresses epithelial-mesenchymal transition markers (N-cadherin, vimentin) and inhibits cell migration and invasion in breast cancer cells, while in endometrial cancer it binds integrin β1 to activate FAK/SRC/c-MYC signaling and maintain cancer stemness [PMID:27840993, PMID:38164180]. Beyond cancer, recombinant NTN4 promotes neurite outgrowth in human sensory neurons, induces pro-inflammatory cytokines (IL-6, IL-8) and chemokines in synovial fibroblasts, and stimulates MMP-3 production in tenocytes as part of a TNF-α/NTN4/MMP-3 axis implicated in extracellular matrix remodeling [PMID:40136644, PMID:40688916]."},"prefetch_data":{"uniprot":{"accession":"Q9HB63","full_name":"Netrin-4","aliases":["Beta-netrin","Hepar-derived netrin-like protein"],"length_aa":628,"mass_kda":70.1,"function":"May play an important role in neural, kidney and vascular development. Promotes neurite elongation from olfactory bulb explants","subcellular_location":"Secreted, extracellular space, extracellular matrix, basement membrane","url":"https://www.uniprot.org/uniprotkb/Q9HB63/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NTN4","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NTN4","total_profiled":1310},"omim":[{"mim_id":"610401","title":"NETRIN 4; NTN4","url":"https://www.omim.org/entry/610401"},{"mim_id":"601614","title":"NETRIN 1; NTN1","url":"https://www.omim.org/entry/601614"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":171.0}],"url":"https://www.proteinatlas.org/search/NTN4"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9HB63","domains":[{"cath_id":"2.60.120.260","chopping":"46-261","consensus_level":"high","plddt":91.8652,"start":46,"end":261},{"cath_id":"2.170.300.10","chopping":"333-392","consensus_level":"medium","plddt":97.0943,"start":333,"end":392},{"cath_id":"2.10.25.10","chopping":"396-464","consensus_level":"medium","plddt":88.1249,"start":396,"end":464},{"cath_id":"2.40.50.120","chopping":"517-627","consensus_level":"high","plddt":82.7138,"start":517,"end":627}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HB63","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HB63-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HB63-F1-predicted_aligned_error_v6.png","plddt_mean":83.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NTN4","jax_strain_url":"https://www.jax.org/strain/search?query=NTN4"},"sequence":{"accession":"Q9HB63","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HB63.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HB63/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HB63"}},"corpus_meta":[{"pmid":"27840993","id":"PMC_27840993","title":"NTN4 is associated with breast cancer metastasis via regulation of EMT-related biomarkers.","date":"2016","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/27840993","citation_count":43,"is_preprint":false},{"pmid":"25042818","id":"PMC_25042818","title":"Genetic association signal near NTN4 in Tourette syndrome.","date":"2014","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/25042818","citation_count":37,"is_preprint":false},{"pmid":"24972566","id":"PMC_24972566","title":"miR-20a contributes to endometriosis by regulating NTN4 expression.","date":"2014","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/24972566","citation_count":36,"is_preprint":false},{"pmid":"32871102","id":"PMC_32871102","title":"eQTL Colocalization Analyses Identify NTN4 as a Candidate Breast Cancer Risk Gene.","date":"2020","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32871102","citation_count":32,"is_preprint":false},{"pmid":"30928649","id":"PMC_30928649","title":"3'UTR variants of TNS3, PHLDB1, NTN4, and GNG2 genes are associated with IgA nephropathy risk in Chinese Han population.","date":"2019","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30928649","citation_count":16,"is_preprint":false},{"pmid":"38164180","id":"PMC_38164180","title":"EXOSC5 maintains cancer stem cell activity in endometrial cancer by regulating the NTN4/integrin β1 signalling axis.","date":"2024","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38164180","citation_count":10,"is_preprint":false},{"pmid":"38175202","id":"PMC_38175202","title":"CD204-positive M2-like tumor-associated macrophages increase migration of gastric cancer cells by upregulating miR-210 to reduce NTN4 expression.","date":"2024","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/38175202","citation_count":7,"is_preprint":false},{"pmid":"35687692","id":"PMC_35687692","title":"The risk variant rs11836367 contributes to breast cancer onset and metastasis by attenuating Wnt signaling via regulating NTN4 expression.","date":"2022","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/35687692","citation_count":6,"is_preprint":false},{"pmid":"27920664","id":"PMC_27920664","title":"Investigation of SNP rs2060546 Immediately Upstream to NTN4 in a Danish Gilles de la Tourette Syndrome Cohort.","date":"2016","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/27920664","citation_count":5,"is_preprint":false},{"pmid":"35232666","id":"PMC_35232666","title":"The Interaction of NTN4 and miR-17-92 Polymorphisms on Breast Cancer Susceptibility in a Chinese Population.","date":"2021","source":"Clinical breast cancer","url":"https://pubmed.ncbi.nlm.nih.gov/35232666","citation_count":4,"is_preprint":false},{"pmid":"40136644","id":"PMC_40136644","title":"Association Between Synovial NTN4 Expression and Pain Scores, and Its Effects on Fibroblasts and Sensory Neurons in End-Stage Knee Osteoarthritis.","date":"2025","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/40136644","citation_count":4,"is_preprint":false},{"pmid":"38156865","id":"PMC_38156865","title":"Hepatic Expression of NTN4 and Its Receptors in Patients with Hepatocellular Carcinoma.","date":"2023","source":"Asian Pacific journal of cancer prevention : APJCP","url":"https://pubmed.ncbi.nlm.nih.gov/38156865","citation_count":3,"is_preprint":false},{"pmid":"40688916","id":"PMC_40688916","title":"Elevation of NTN4 Expression and Its Possible Regulation by Tumor Necrosis Factor-Alpha (TNF-α) in a Rat Model of Rotator Cuff Tear.","date":"2025","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/40688916","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.30.25321017","title":"Genome-wide association study of Idiopathic Pulmonary Fibrosis susceptibility using clinically-curated European-ancestry datasets","date":"2025-02-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.30.25321017","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.18.24313937","title":"Rare Variant Association Analysis Uncovers Involvement of<i>VNN2</i>in Stroke Outcome","date":"2024-09-19","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.18.24313937","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.08.24310079","title":"Overlap between COPD genetic association results and transcriptional quantitative trait loci","date":"2024-07-08","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.08.24310079","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10447,"output_tokens":2101,"usd":0.031428},"stage2":{"model":"claude-opus-4-6","input_tokens":5415,"output_tokens":2401,"usd":0.13065},"total_usd":0.162078,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"NTN4 acts as a tumor suppressor by directly binding to Wnt ligands, thereby attenuating the Wnt signaling pathway. Loss of NTN4 in mice leads to earlier tumor onset, progression, and metastasis. The protective T allele of rs11836367 increases GATA3 binding to a distal enhancer and up-regulates NTN4 expression.\",\n      \"method\": \"Co-binding assay (NTN4 binding to Wnt ligands), endogenous genome editing (enhancer reporter assays, CRISPR), mouse knockout model with tumor phenotype, enhancer-GATA3 binding assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including direct binding assay, genome editing, and in vivo mouse KO with defined phenotype in a single study\",\n      \"pmids\": [\"35687692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Secreted NTN4 binds to integrin β1 on endometrial cancer cells, triggering the FAK/SRC signaling axis to elevate c-MYC activity, thereby maintaining cancer stem cell self-renewal. EXOSC5 augments NTN4 expression upstream of this pathway.\",\n      \"method\": \"NTN4 treatment experiments, EXOSC5 knockdown, co-immunoprecipitation/binding of NTN4 with integrin β1, pharmacological inhibition of FAK/SRC, cancer stem cell sphere assays, in vivo tumorigenicity assays\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple functional assays with receptor identification but binding validated by treatment rather than direct structural reconstitution\",\n      \"pmids\": [\"38164180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NTN4 overexpression in breast cancer cells attenuates cell migration and invasion and suppresses EMT markers N-cadherin and vimentin; NTN4 knockdown increases migration, invasion, and EMT marker expression.\",\n      \"method\": \"NTN4-pcDNA3.1 overexpression and siRNA knockdown in breast cancer cell lines (MDA-MB-231, Hs578T), migration/invasion assays, Western blot for EMT markers\",\n      \"journal\": \"Oncology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — reciprocal gain/loss-of-function with defined cellular phenotype and molecular readout, single lab\",\n      \"pmids\": [\"27840993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A causal variant (rs61938093) at the NTN4 locus resides within an enhancer element that physically interacts with the NTN4 promoter; the risk allele reduces NTN4 promoter activity. NTN4 knockdown in breast cells increases cell proliferation in vitro and tumor growth in vivo.\",\n      \"method\": \"Chromatin conformation capture (enhancer-promoter physical interaction), enhancer reporter assay, NTN4 knockdown, in vitro proliferation assay, in vivo xenograft tumor growth\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (chromatin interaction, reporter assay, KD in vitro and in vivo) establishing regulatory mechanism and functional consequence\",\n      \"pmids\": [\"32871102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD204+ M2-like tumor-associated macrophages secrete TNF-α, which activates NF-κB/HIF-1α signaling in gastric cancer cells to upregulate miR-210, which in turn directly targets the NTN4 3'UTR to suppress NTN4 expression and promote cancer cell migration.\",\n      \"method\": \"Co-culture experiments, miRNA microarray, anti-miRNA and miRNA mimic transfection, neutralizing antibodies and pharmacological inhibitors, luciferase 3'UTR reporter assay with mutation of miR-210 binding site\",\n      \"journal\": \"Cancer immunology, immunotherapy : CII\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — luciferase reporter with binding site mutation confirms direct miR-210/NTN4 interaction; pathway dissected with inhibitors; single lab\",\n      \"pmids\": [\"38175202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"miR-20a targets NTN4 and suppresses its expression in ovarian endometriosis; increased miR-20a in advanced endometriosis correlates with decreased NTN4 expression.\",\n      \"method\": \"Computational prediction of miR-20a target sites in NTN4, qRT-PCR expression analysis in patient tissues\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3-4 — computational prediction with correlative expression data only, no direct reporter or functional rescue experiment shown\",\n      \"pmids\": [\"24972566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Recombinant NTN4 (rh-NTN4) enhances neurite outgrowth in human iPSC-derived sensory neurons and stimulates production of pro-inflammatory cytokines (IL-6, IL-8) and chemokines (CXCL1, CXCL6, CXCL8) in synovial fibroblasts from OA patients.\",\n      \"method\": \"Recombinant NTN4 treatment of human iPSC-derived sensory neurons (neurite outgrowth assay) and synovial fibroblasts (ELISA for cytokines/chemokines)\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct functional assays with recombinant protein on human cells, but single lab without genetic rescue experiments\",\n      \"pmids\": [\"40136644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TNF-α induces NTN4 expression in rat tenocytes in a dose-dependent manner, and exogenous NTN4 induces MMP-3 (but not MMP-1, TNF-α, or IL-6) expression and protein secretion in tenocytes, defining a TNF-α/NTN4/MMP-3 axis in tendon ECM degradation.\",\n      \"method\": \"In vivo rat rotator cuff tear model (qRT-PCR), in vitro recombinant TNF-α stimulation of primary tenocytes (qRT-PCR, ELISA), exogenous recombinant NTN4 stimulation\",\n      \"journal\": \"Cureus\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo mechanistic experiments with recombinant proteins defining a cytokine-NTN4-MMP axis; single lab\",\n      \"pmids\": [\"40688916\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NTN4 (Netrin-4) is a secreted glycoprotein that functions as a tumor suppressor by directly binding Wnt ligands to attenuate Wnt signaling, suppressing EMT and cell migration/invasion; it also signals through integrin β1/FAK/SRC to regulate c-MYC and cancer stemness, promotes neurite outgrowth and neuronal sensitization, and modulates inflammatory responses in fibroblasts via IL-6/IL-8/chemokine induction, while its expression is regulated by upstream enhancer elements (controlled by GATA3 and risk-associated SNPs), miRNAs (miR-20a, miR-210), and inflammatory cytokines such as TNF-α.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NTN4 (Netrin-4) is a secreted glycoprotein that functions as a ligand-sequestering tumor suppressor and a context-dependent signaling molecule in neural and inflammatory biology. NTN4 directly binds Wnt ligands to attenuate Wnt signaling, and loss of NTN4 in mice accelerates tumor onset, progression, and metastasis; its expression is governed by distal enhancer elements regulated by GATA3 and breast cancer risk-associated SNPs (rs11836367, rs61938093), as well as by miR-210 downstream of TNF-α/NF-κB/HIF-1α signaling [PMID:35687692, PMID:32871102, PMID:38175202]. NTN4 suppresses epithelial-mesenchymal transition markers (N-cadherin, vimentin) and inhibits cell migration and invasion in breast cancer cells, while in endometrial cancer it binds integrin β1 to activate FAK/SRC/c-MYC signaling and maintain cancer stemness [PMID:27840993, PMID:38164180]. Beyond cancer, recombinant NTN4 promotes neurite outgrowth in human sensory neurons, induces pro-inflammatory cytokines (IL-6, IL-8) and chemokines in synovial fibroblasts, and stimulates MMP-3 production in tenocytes as part of a TNF-α/NTN4/MMP-3 axis implicated in extracellular matrix remodeling [PMID:40136644, PMID:40688916].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Computational and correlative evidence first linked miR-20a to post-transcriptional suppression of NTN4 in endometriosis, raising the question of how NTN4 expression is regulated by miRNAs.\",\n      \"evidence\": \"Computational target prediction and qRT-PCR expression correlation in patient endometriosis tissues\",\n      \"pmids\": [\"24972566\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct reporter assay or functional rescue to confirm miR-20a binding to NTN4 3′UTR\", \"Mechanism by which NTN4 loss contributes to endometriosis pathology undefined\", \"Not independently replicated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Reciprocal gain- and loss-of-function experiments established NTN4 as an inhibitor of EMT, migration, and invasion in breast cancer, defining its cellular anti-metastatic function.\",\n      \"evidence\": \"Overexpression and siRNA knockdown in MDA-MB-231 and Hs578T cells with migration/invasion assays and Western blot for N-cadherin and vimentin\",\n      \"pmids\": [\"27840993\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating anti-EMT activity not identified\", \"No in vivo validation of EMT suppression\", \"Downstream signaling pathway not mapped\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of a causal enhancer variant (rs61938093) that physically contacts the NTN4 promoter established the regulatory architecture controlling NTN4 expression and linked reduced NTN4 to increased breast tumor growth in vivo.\",\n      \"evidence\": \"Chromatin conformation capture, enhancer reporter assay, NTN4 knockdown with in vitro proliferation and xenograft tumor growth assays\",\n      \"pmids\": [\"32871102\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Transcription factors mediating enhancer activity at this variant not fully characterized\", \"Whether enhancer loss phenocopies NTN4 coding deletion not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Direct binding of NTN4 to Wnt ligands revealed its molecular mechanism as a Wnt pathway antagonist, while mouse knockout confirmed its in vivo tumor-suppressive role and a second enhancer SNP (rs11836367) was linked to GATA3-dependent NTN4 upregulation.\",\n      \"evidence\": \"Co-binding assay of NTN4 with Wnt ligands, CRISPR enhancer editing, mouse NTN4 knockout with tumor and metastasis phenotyping, GATA3 binding assays\",\n      \"pmids\": [\"35687692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specificity for individual Wnt family members not fully delineated\", \"Structural basis of NTN4–Wnt interaction unknown\", \"Whether Wnt sequestration fully accounts for tumor suppression or additional receptors contribute\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"NTN4 was shown to bind integrin β1 and activate FAK/SRC/c-MYC to sustain cancer stemness in endometrial cancer, revealing a pro-tumorigenic receptor-mediated axis distinct from its Wnt-sequestering tumor-suppressive role.\",\n      \"evidence\": \"Co-immunoprecipitation of NTN4 with integrin β1, FAK/SRC pharmacological inhibition, sphere-forming and in vivo tumorigenicity assays in endometrial cancer cells\",\n      \"pmids\": [\"38164180\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NTN4–integrin β1 binding not validated by structural or biophysical reconstitution\", \"Context determining whether NTN4 acts as tumor suppressor versus stemness promoter not resolved\", \"EXOSC5-dependent NTN4 upregulation mechanism not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The TNF-α/NF-κB/HIF-1α/miR-210 axis was identified as a direct post-transcriptional silencer of NTN4 in the tumor microenvironment, explaining how macrophage-derived signals suppress NTN4 to promote cancer cell migration.\",\n      \"evidence\": \"Macrophage–cancer cell co-culture, miR-210 mimic/inhibitor transfection, luciferase 3′UTR reporter with miR-210 binding site mutation, neutralizing antibodies and pharmacological inhibitors in gastric cancer cells\",\n      \"pmids\": [\"38175202\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-210-mediated NTN4 suppression is relevant in non-gastric cancer contexts untested\", \"Quantitative contribution of miR-210 versus other NTN4-targeting miRNAs not compared\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Functional assays with recombinant NTN4 demonstrated its dual role outside cancer: promoting neurite outgrowth in sensory neurons and inducing pro-inflammatory cytokine/chemokine production in synovial fibroblasts and MMP-3 in tenocytes, linking NTN4 to neural development and tissue inflammation/ECM remodeling.\",\n      \"evidence\": \"Recombinant NTN4 treatment of iPSC-derived sensory neurons (neurite assay), OA synovial fibroblasts (ELISA), and rat tenocytes (qRT-PCR/ELISA) with TNF-α stimulation\",\n      \"pmids\": [\"40136644\", \"40688916\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor(s) mediating NTN4 effects in neurons and fibroblasts not identified\", \"Signaling pathways downstream of NTN4 in non-cancer cell types not mapped\", \"In vivo relevance of NTN4 in joint inflammation and tendon repair not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of NTN4–Wnt and NTN4–integrin β1 interactions, the determinants of context-dependent tumor-suppressive versus stemness-promoting activity, the receptor(s) mediating NTN4 signaling in neurons and fibroblasts, and the in vivo contribution of NTN4 to inflammatory joint and tendon pathology.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal/cryo-EM structure of NTN4 or its ligand complexes\", \"Tissue-specific receptor utilization logic unknown\", \"No genetic models for NTN4 in inflammatory or neuronal phenotypes beyond cancer\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [1, 6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 6, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ITGB1\",\n      \"GATA3\",\n      \"MMP3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}