{"gene":"NTN4","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2022,"finding":"NTN4 acts as a tumor suppressor that attenuates the Wnt signaling pathway by directly binding to Wnt ligands. 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, upregulating NTN4 expression.","method":"Endogenous genome editing (CRISPR), enhancer reporter assays, mouse knockout model, direct binding assay (NTN4 binding to Wnt ligands)","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods including genome editing, reporter assays, mouse KO, and direct binding demonstrated in a single rigorous study","pmids":["35687692"],"is_preprint":false},{"year":2024,"finding":"NTN4, when secreted, binds 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 knockdown reduces NTN4 levels, and exogenous NTN4 treatment rescues CSC activity.","method":"EXOSC5 knockdown, NTN4 recombinant protein treatment, co-immunoprecipitation/binding assay (NTN4–integrin β1 interaction), tumor sphere assays, Western blotting for FAK/SRC/c-MYC","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal functional rescue and binding partner identification in a single lab with multiple orthogonal methods, but no structural validation","pmids":["38164180"],"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 (validated by luciferase reporter with mutated binding site) and reduces NTN4 expression, promoting cancer cell migration.","method":"Co-culture assays, miRNA microarray, anti-miRNA/mimic transfection, luciferase reporter assay with 3'UTR and binding-site mutation, neutralizing antibodies and pharmacological inhibitors","journal":"Cancer immunology, immunotherapy : CII","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter with mutation validation and functional rescue in a single lab with multiple orthogonal methods","pmids":["38175202"],"is_preprint":false},{"year":2020,"finding":"The causal variant rs61938093 at the NTN4 locus is located within an enhancer element that physically interacts with the NTN4 promoter; the risk allele reduces NTN4 promoter activity. Knockdown of NTN4 in breast cells increases cell proliferation in vitro and tumor growth in vivo.","method":"Enhancer reporter assays, chromatin interaction assays (enhancer–promoter looping), NTN4 knockdown in breast cell lines, in vivo xenograft tumor growth assay","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (reporter assays, chromatin interaction, KD phenotype in vitro and in vivo) in a single study","pmids":["32871102"],"is_preprint":false},{"year":2016,"finding":"NTN4 overexpression in MDA-MB-231 breast cancer cells attenuates cell migration and invasion and reduces N-cadherin and vimentin expression (EMT markers), while NTN4 siRNA knockdown increases migration, invasion, and upregulates N-cadherin and vimentin.","method":"NTN4 overexpression (pcDNA3.1 plasmid) and siRNA knockdown in breast cancer cell lines; migration and invasion assays; Western blotting for EMT markers","journal":"Oncology reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — gain- and loss-of-function with phenotypic readout but no pathway placement or binding partner identification, single lab single approach","pmids":["27840993"],"is_preprint":false},{"year":2025,"finding":"In a rat rotator cuff tear model, NTN4 expression is induced by TNF-α in tenocytes in a dose-dependent manner in vitro. Exogenous NTN4 stimulation of tenocytes induces MMP-3 expression at both transcript and protein levels, but does not significantly change MMP-1, TNF-α, or IL-6 protein levels, placing NTN4 downstream of TNF-α and upstream of MMP-3-mediated ECM degradation.","method":"Rat tendon tear in vivo model (qRT-PCR at multiple time points), primary rat tenocyte stimulation with recombinant TNF-α and NTN4 (qRT-PCR, ELISA)","journal":"Cureus","confidence":"Low","confidence_rationale":"Tier 3 / Weak — in vitro stimulation assay with defined readout in a single study, no genetic or structural validation","pmids":["40688916"],"is_preprint":false},{"year":2025,"finding":"Recombinant human 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 fibroblast-like cells from osteoarthritis patients.","method":"Recombinant protein treatment of human iPSC-derived sensory neurons (neurite outgrowth assay) and OA patient synovial fibroblasts (cytokine/chemokine ELISA)","journal":"Cells","confidence":"Low","confidence_rationale":"Tier 3 / Weak — recombinant protein stimulation with phenotypic readout in a single study, no receptor identification or signaling pathway delineated","pmids":["40136644"],"is_preprint":false}],"current_model":"NTN4 (Netrin-4) is a secreted laminin-related glycoprotein that functions as a tumor suppressor by directly binding Wnt ligands to attenuate Wnt signaling, and when secreted it can also bind integrin β1 to activate FAK/SRC/c-MYC signaling in cancer stem cells; its expression is regulated by enhancer elements responsive to GATA3 binding at GWAS-identified risk variants, and it is post-transcriptionally repressed by miRNAs (including miR-210) downstream of TNF-α/NF-κB/HIF-1α signaling in tumor-promoting macrophage co-culture contexts."},"narrative":{"mechanistic_narrative":"NTN4 (Netrin-4) is a secreted glycoprotein that functions predominantly as a tumor suppressor through direct attenuation of Wnt signaling: it binds Wnt ligands directly, and loss of NTN4 in mice accelerates tumor onset, progression, and metastasis [PMID:35687692]. Its expression is governed by distal enhancer elements that loop to the NTN4 promoter, and GWAS-identified risk variants modulate this regulation—the protective allele of rs11836367 increases GATA3 binding to enhance NTN4 expression [PMID:35687692], while the risk allele of rs61938093 reduces promoter activity, and NTN4 knockdown increases proliferation and tumor growth in breast cells [PMID:32871102]. In a context-dependent reversal of this suppressive role, secreted NTN4 binds integrin β1 on endometrial cancer cells to activate FAK/SRC signaling and elevate c-MYC, sustaining cancer stem cell self-renewal [PMID:38164180]. NTN4 is also under post-transcriptional control in the tumor microenvironment, where macrophage-derived TNF-α drives NF-κB/HIF-1α-dependent miR-210 expression that directly targets the NTN4 3'UTR to repress its expression and promote migration [PMID:38175202]. Beyond oncology, recombinant NTN4 acts downstream of TNF-α to induce MMP-3 in tenocytes [PMID:40688916] and stimulates neurite outgrowth and inflammatory cytokine production in sensory neurons and synovial fibroblasts [PMID:40136644], though receptors for these activities are not defined in the available corpus.","teleology":[{"year":2020,"claim":"Established that NTN4 expression is controlled by a long-range enhancer and that reducing NTN4 is pro-tumorigenic, linking a GWAS locus to a functional cancer phenotype.","evidence":"Enhancer reporter and chromatin interaction assays plus NTN4 knockdown with in vitro and xenograft readouts in breast cells","pmids":["32871102"],"confidence":"Medium","gaps":["Did not identify the downstream signaling pathway through which NTN4 loss promotes proliferation","Transcription factor mediating the enhancer-promoter effect not defined"]},{"year":2022,"claim":"Defined the core tumor-suppressor mechanism by showing NTN4 directly binds Wnt ligands to attenuate Wnt signaling, and connected the protective risk allele to GATA3-driven enhancer activation.","evidence":"CRISPR genome editing, enhancer reporter assays, mouse knockout, and direct NTN4–Wnt binding assays","pmids":["35687692"],"confidence":"High","gaps":["No structural detail of the NTN4–Wnt interaction","Which specific Wnt ligands and downstream branches are affected not fully delineated"]},{"year":2024,"claim":"Revealed a context-dependent oncogenic activity in which secreted NTN4 binds integrin β1 to drive FAK/SRC/c-MYC signaling and maintain cancer stem cells, contrasting with its tumor-suppressive Wnt-binding role.","evidence":"EXOSC5 knockdown, recombinant NTN4 rescue, NTN4–integrin β1 binding assays, tumor sphere assays, and Western blotting in endometrial cancer cells","pmids":["38164180"],"confidence":"Medium","gaps":["No structural validation of the NTN4–integrin β1 interaction","Reconciliation of suppressive vs. oncogenic roles across tumor types unresolved"]},{"year":2024,"claim":"Placed NTN4 under post-transcriptional control of the tumor microenvironment by showing macrophage TNF-α induces miR-210 that directly targets the NTN4 3'UTR to promote migration.","evidence":"Co-culture, miRNA microarray, luciferase reporter with 3'UTR binding-site mutation, and functional rescue in gastric cancer cells","pmids":["38175202"],"confidence":"Medium","gaps":["Downstream effectors of reduced NTN4 driving migration not mapped","Single-lab validation"]},{"year":2025,"claim":"Extended NTN4 function beyond cancer, positioning it downstream of TNF-α and upstream of MMP-3-mediated ECM degradation in tendon, and as a pro-inflammatory and neurotrophic factor in joint tissues.","evidence":"Recombinant NTN4 stimulation of rat tenocytes (qRT-PCR, ELISA), human iPSC-derived sensory neurons (neurite outgrowth), and OA synovial fibroblasts (cytokine ELISA)","pmids":["40688916","40136644"],"confidence":"Low","gaps":["No receptor or signaling pathway identified for the neurotrophic and inflammatory effects","Stimulation-only assays without genetic loss-of-function","Single studies, not independently confirmed"]},{"year":null,"claim":"How NTN4 switches between Wnt-binding tumor suppression and integrin-β1-mediated oncogenic signaling, and which receptors mediate its non-cancer neurotrophic and inflammatory activities, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of NTN4 with any binding partner","Determinants of context-dependent suppressive vs. oncogenic output unknown","Receptors for tenocyte, neuron, and fibroblast responses unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,3]}],"complexes":[],"partners":["WNT","ITGB1"],"other_free_text":[]}},"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":44,"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":11,"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":"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":"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":"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_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},{"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}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11166,"output_tokens":1954,"usd":0.031404,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8878,"output_tokens":2373,"usd":0.051858,"stage2_stop_reason":"end_turn"},"total_usd":0.083262,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"NTN4 acts as a tumor suppressor that attenuates the Wnt signaling pathway by directly binding to Wnt ligands. 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, upregulating NTN4 expression.\",\n      \"method\": \"Endogenous genome editing (CRISPR), enhancer reporter assays, mouse knockout model, direct binding assay (NTN4 binding to Wnt ligands)\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods including genome editing, reporter assays, mouse KO, and direct binding demonstrated in a single rigorous study\",\n      \"pmids\": [\"35687692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NTN4, when secreted, binds 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 knockdown reduces NTN4 levels, and exogenous NTN4 treatment rescues CSC activity.\",\n      \"method\": \"EXOSC5 knockdown, NTN4 recombinant protein treatment, co-immunoprecipitation/binding assay (NTN4–integrin β1 interaction), tumor sphere assays, Western blotting for FAK/SRC/c-MYC\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal functional rescue and binding partner identification in a single lab with multiple orthogonal methods, but no structural validation\",\n      \"pmids\": [\"38164180\"],\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 (validated by luciferase reporter with mutated binding site) and reduces NTN4 expression, promoting cancer cell migration.\",\n      \"method\": \"Co-culture assays, miRNA microarray, anti-miRNA/mimic transfection, luciferase reporter assay with 3'UTR and binding-site mutation, neutralizing antibodies and pharmacological inhibitors\",\n      \"journal\": \"Cancer immunology, immunotherapy : CII\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter with mutation validation and functional rescue in a single lab with multiple orthogonal methods\",\n      \"pmids\": [\"38175202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The causal variant rs61938093 at the NTN4 locus is located within an enhancer element that physically interacts with the NTN4 promoter; the risk allele reduces NTN4 promoter activity. Knockdown of NTN4 in breast cells increases cell proliferation in vitro and tumor growth in vivo.\",\n      \"method\": \"Enhancer reporter assays, chromatin interaction assays (enhancer–promoter looping), NTN4 knockdown in breast cell lines, in vivo xenograft tumor growth assay\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (reporter assays, chromatin interaction, KD phenotype in vitro and in vivo) in a single study\",\n      \"pmids\": [\"32871102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NTN4 overexpression in MDA-MB-231 breast cancer cells attenuates cell migration and invasion and reduces N-cadherin and vimentin expression (EMT markers), while NTN4 siRNA knockdown increases migration, invasion, and upregulates N-cadherin and vimentin.\",\n      \"method\": \"NTN4 overexpression (pcDNA3.1 plasmid) and siRNA knockdown in breast cancer cell lines; migration and invasion assays; Western blotting for EMT markers\",\n      \"journal\": \"Oncology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — gain- and loss-of-function with phenotypic readout but no pathway placement or binding partner identification, single lab single approach\",\n      \"pmids\": [\"27840993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a rat rotator cuff tear model, NTN4 expression is induced by TNF-α in tenocytes in a dose-dependent manner in vitro. Exogenous NTN4 stimulation of tenocytes induces MMP-3 expression at both transcript and protein levels, but does not significantly change MMP-1, TNF-α, or IL-6 protein levels, placing NTN4 downstream of TNF-α and upstream of MMP-3-mediated ECM degradation.\",\n      \"method\": \"Rat tendon tear in vivo model (qRT-PCR at multiple time points), primary rat tenocyte stimulation with recombinant TNF-α and NTN4 (qRT-PCR, ELISA)\",\n      \"journal\": \"Cureus\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — in vitro stimulation assay with defined readout in a single study, no genetic or structural validation\",\n      \"pmids\": [\"40688916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Recombinant human 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 fibroblast-like cells from osteoarthritis patients.\",\n      \"method\": \"Recombinant protein treatment of human iPSC-derived sensory neurons (neurite outgrowth assay) and OA patient synovial fibroblasts (cytokine/chemokine ELISA)\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — recombinant protein stimulation with phenotypic readout in a single study, no receptor identification or signaling pathway delineated\",\n      \"pmids\": [\"40136644\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NTN4 (Netrin-4) is a secreted laminin-related glycoprotein that functions as a tumor suppressor by directly binding Wnt ligands to attenuate Wnt signaling, and when secreted it can also bind integrin β1 to activate FAK/SRC/c-MYC signaling in cancer stem cells; its expression is regulated by enhancer elements responsive to GATA3 binding at GWAS-identified risk variants, and it is post-transcriptionally repressed by miRNAs (including miR-210) downstream of TNF-α/NF-κB/HIF-1α signaling in tumor-promoting macrophage co-culture contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NTN4 (Netrin-4) is a secreted glycoprotein that functions predominantly as a tumor suppressor through direct attenuation of Wnt signaling: it binds Wnt ligands directly, and loss of NTN4 in mice accelerates tumor onset, progression, and metastasis [#0]. Its expression is governed by distal enhancer elements that loop to the NTN4 promoter, and GWAS-identified risk variants modulate this regulation—the protective allele of rs11836367 increases GATA3 binding to enhance NTN4 expression [#0], while the risk allele of rs61938093 reduces promoter activity, and NTN4 knockdown increases proliferation and tumor growth in breast cells [#3]. In a context-dependent reversal of this suppressive role, secreted NTN4 binds integrin \\u03b21 on endometrial cancer cells to activate FAK/SRC signaling and elevate c-MYC, sustaining cancer stem cell self-renewal [#1]. NTN4 is also under post-transcriptional control in the tumor microenvironment, where macrophage-derived TNF-\\u03b1 drives NF-\\u03baB/HIF-1\\u03b1-dependent miR-210 expression that directly targets the NTN4 3'UTR to repress its expression and promote migration [#2]. Beyond oncology, recombinant NTN4 acts downstream of TNF-\\u03b1 to induce MMP-3 in tenocytes [#5] and stimulates neurite outgrowth and inflammatory cytokine production in sensory neurons and synovial fibroblasts [#6], though receptors for these activities are not defined in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2020,\n      \"claim\": \"Established that NTN4 expression is controlled by a long-range enhancer and that reducing NTN4 is pro-tumorigenic, linking a GWAS locus to a functional cancer phenotype.\",\n      \"evidence\": \"Enhancer reporter and chromatin interaction assays plus NTN4 knockdown with in vitro and xenograft readouts in breast cells\",\n      \"pmids\": [\"32871102\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not identify the downstream signaling pathway through which NTN4 loss promotes proliferation\", \"Transcription factor mediating the enhancer-promoter effect not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the core tumor-suppressor mechanism by showing NTN4 directly binds Wnt ligands to attenuate Wnt signaling, and connected the protective risk allele to GATA3-driven enhancer activation.\",\n      \"evidence\": \"CRISPR genome editing, enhancer reporter assays, mouse knockout, and direct NTN4\\u2013Wnt binding assays\",\n      \"pmids\": [\"35687692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural detail of the NTN4\\u2013Wnt interaction\", \"Which specific Wnt ligands and downstream branches are affected not fully delineated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a context-dependent oncogenic activity in which secreted NTN4 binds integrin \\u03b21 to drive FAK/SRC/c-MYC signaling and maintain cancer stem cells, contrasting with its tumor-suppressive Wnt-binding role.\",\n      \"evidence\": \"EXOSC5 knockdown, recombinant NTN4 rescue, NTN4\\u2013integrin \\u03b21 binding assays, tumor sphere assays, and Western blotting in endometrial cancer cells\",\n      \"pmids\": [\"38164180\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural validation of the NTN4\\u2013integrin \\u03b21 interaction\", \"Reconciliation of suppressive vs. oncogenic roles across tumor types unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed NTN4 under post-transcriptional control of the tumor microenvironment by showing macrophage TNF-\\u03b1 induces miR-210 that directly targets the NTN4 3'UTR to promote migration.\",\n      \"evidence\": \"Co-culture, miRNA microarray, luciferase reporter with 3'UTR binding-site mutation, and functional rescue in gastric cancer cells\",\n      \"pmids\": [\"38175202\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effectors of reduced NTN4 driving migration not mapped\", \"Single-lab validation\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended NTN4 function beyond cancer, positioning it downstream of TNF-\\u03b1 and upstream of MMP-3-mediated ECM degradation in tendon, and as a pro-inflammatory and neurotrophic factor in joint tissues.\",\n      \"evidence\": \"Recombinant NTN4 stimulation of rat tenocytes (qRT-PCR, ELISA), human iPSC-derived sensory neurons (neurite outgrowth), and OA synovial fibroblasts (cytokine ELISA)\",\n      \"pmids\": [\"40688916\", \"40136644\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No receptor or signaling pathway identified for the neurotrophic and inflammatory effects\", \"Stimulation-only assays without genetic loss-of-function\", \"Single studies, not independently confirmed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NTN4 switches between Wnt-binding tumor suppression and integrin-\\u03b21-mediated oncogenic signaling, and which receptors mediate its non-cancer neurotrophic and inflammatory activities, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of NTN4 with any binding partner\", \"Determinants of context-dependent suppressive vs. oncogenic output unknown\", \"Receptors for tenocyte, neuron, and fibroblast responses unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"WNT\", \"ITGB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}