{"gene":"NECTIN4","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2001,"finding":"Nectin-4 was identified as a new member of the nectin family that binds afadin via its C-terminal cytoplasmic sequence and co-localizes with afadin at cadherin-based adherens junctions in MDCKII epithelial cells. Nectin-4 trans-interacts heterophilically with nectin-1 (but not nectin-2, nectin-3, or PVR/CD155) through its V (membrane-distal immunoglobulin-like) domain, and also exhibits homophilic binding.","method":"Soluble chimeric Fc-fusion pulldown assays, reciprocal co-immunoprecipitation in COS cells, in vitro protein-protein interaction assays, co-localization by immunofluorescence microscopy, domain-deletion constructs","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (reciprocal Co-IP, Fc-fusion pulldown, in vitro binding, co-localization) in a single rigorous study; interaction specificity confirmed by negative controls with nectin-2, -3, PVR","pmids":["11544254"],"is_preprint":false},{"year":2009,"finding":"Exogenous expression of Nectin-4 in mammalian cells increased lamellipodia formation and invasive ability through activation of the small GTPase Rac1.","method":"siRNA knockdown, exogenous overexpression, cell invasion assays, Rac1 activation assay","journal":"Cancer Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function in cell lines with specific GTPase readout, single lab, two orthogonal approaches","pmids":["19679554"],"is_preprint":false},{"year":2010,"finding":"Homozygous loss-of-function mutations in PVRL4/nectin-4 cause ectodermal dysplasia-syndactyly syndrome (EDSS). In patient keratinocytes, mutated nectin-4 lost its ability to bind nectin-1, and adherens junction complexes (nectin-afadin and cadherin-catenin) showed altered membrane localization accompanied by actin cytoskeleton reorganization in hair follicle structures.","method":"Homozygosity mapping, candidate gene sequencing, co-immunoprecipitation/binding assay in patient keratinocytes, immunofluorescence of adherens junction components, actin cytoskeleton staining","journal":"American Journal of Human Genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetics (multiple families, two independent mutations) combined with functional cell biology (loss of nectin-1 binding, disrupted junctional complexes) in disease-relevant cells","pmids":["20691405"],"is_preprint":false},{"year":2011,"finding":"Nectin-4 (PVRL4), an adherens junction protein of the immunoglobulin superfamily, functions as the epithelial exit receptor for measles virus. Its membrane-distal (V) domain interacts with the viral attachment (H) protein with high affinity. Nectin-4 supports MV entry and non-cytopathic lateral spread in well-differentiated primary human airway epithelial sheets infected basolaterally; MV infection downregulates nectin-4 surface expression.","method":"Functional surface protein screen, siRNA knockdown, antibody blocking, flow cytometry, confocal microscopy, surface biotinylation, virus binding assay in primary airway epithelial cells and cancer cell lines","journal":"Nature / PLoS Pathogens","confidence":"High","confidence_rationale":"Tier 1 / Strong — independently replicated in two concurrent papers (PMID 22048310 and 21901103) using multiple orthogonal methods including receptor knockdown, antibody block, binding assays, and primary tissue infection","pmids":["22048310","21901103"],"is_preprint":false},{"year":2012,"finding":"Wild-type canine distemper virus (CDV) uses nectin-4 as an epithelial cell receptor; infection is blocked by anti-nectin-4 antibody, and CDV antigen co-localises with nectin-4-positive neurons and epithelial cells in vivo, implicating nectin-4 in CDV neurovirulence.","method":"Infection of Vero cells expressing dog nectin-4, antibody blocking assay, immunohistochemistry of infected dog tissues","journal":"Journal of Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based infection assay with antibody block plus in vivo IHC correlation, single lab","pmids":["22761370"],"is_preprint":false},{"year":2013,"finding":"PVRL4/Nectin-4 promotes anchorage-independent growth by driving cell-to-cell attachment and activating a matrix-independent integrin β4/SHP-2/c-Src signaling axis, which is required for breast cancer cell transformation. Blocking PVRL4-driven cell-to-cell attachment with monoclonal antibodies inhibited orthotopic tumor growth in vivo.","method":"Gain-of-function screen for anchorage independence, epistasis with integrin β4/SHP-2/c-Src pathway components (knockdown/inhibition), in vivo xenograft with anti-PVRL4 antibody treatment","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional screen identifying PVRL4, pathway epistasis (multiple components), and in vivo validation with antibody blockade; multiple orthogonal approaches in a single rigorous study","pmids":["23682311"],"is_preprint":false},{"year":2014,"finding":"The V domain of PVRL4/nectin-4 is critical for canine distemper virus (CDV) entry and cell-to-cell spread. Four specific amino acid residues in the V domain of dog PVRL4 and two in the CDV hemagglutinin were essential for receptor-mediated virus entry.","method":"Domain-deletion and site-directed mutagenesis constructs, virus entry and cell-to-cell spread assays","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis defining essential residues, single lab","pmids":["24725937"],"is_preprint":false},{"year":2015,"finding":"PVRL4 (nectin-4) transcriptional expression is not directly regulated by p63 (unlike nectin-1), but is controlled by the transcription factor IRF6: IRF6 depletion in keratinocytes reduced Pvrl4 expression, and Pvrl4 was downregulated in AEC syndrome keratinocytes in parallel with decreased IRF6.","method":"p63 knockout mouse skin analysis, siRNA depletion of p63 and IRF6 in primary keratinocytes, chromatin immunoprecipitation (p63 binds Pvrl1 but not Pvrl4), RT-qPCR in patient-derived AEC keratinocytes and conditional mouse model","journal":"Experimental Dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP for negative result (p63 does not bind Pvrl4), IRF6 loss-of-function with gene expression readout, multiple experimental models in one study","pmids":["25387952"],"is_preprint":false},{"year":2017,"finding":"Measles virus enters PVRL4-positive breast cancer and colon cancer cells via a PVRL4-mediated macropinocytosis pathway that is dynamin-independent but requires actin polymerization, Rac1, and PAK1 (in MCF7 cells); MV entry induced membrane ruffles and elevated fluid uptake.","method":"Pharmacological inhibitors of endocytic pathways (EIPA, dynasore, actin inhibitors), siRNA knockdown of PAK1 and Rac1, phalloidin staining, fluid-phase uptake assay, recombinant fluorescent MeV reporters","journal":"Journal of Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple inhibitors and siRNA knockdowns with defined pathway readouts, single lab","pmids":["28250131"],"is_preprint":false},{"year":2017,"finding":"Nectin-4 is a marker for breast cancer stem cells and activates WNT/β-catenin signaling via the PI3K/Akt axis to support BCSC self-renewal. Nectin-4 depletion inhibited EMT, metastasis, invasion, and the WNT/β-catenin pathway; overexpression in null cells induced WNT/β-catenin signaling via PI3K/Akt.","method":"siRNA knockdown, stable overexpression in nectin-4-null cells, in vitro invasion/EMT assays, in vivo mouse models, ex vivo patient samples, Western blot for pathway components","journal":"The International Journal of Biochemistry & Cell Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional gain/loss-of-function with defined pathway readouts, single lab, in vitro and in vivo","pmids":["28600142"],"is_preprint":false},{"year":2018,"finding":"PVRL4/Nectin-4 mediates spontaneous cell clustering of matrix-detached epithelial and carcinoma cells. This clustering activates a PVRL4/α6β4 integrin/Src signaling axis that sustains GPX4 expression and protects against lipid peroxidation/ferroptosis. In the absence of α6β4, PVRL4-mediated clustering paradoxically increased lipid peroxidation and triggered ferroptosis; inhibiting clustering shifted cell death from ferroptosis to apoptosis.","method":"Antibody blocking and siRNA knockdown of PVRL4, α6β4 integrin knockout/knockdown, lipid peroxidation assays, GPX4 expression analysis, ferroptosis/apoptosis assays under matrix-detached conditions","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic and pharmacological perturbations (PVRL4 KD, α6β4 KO, antibody blocking) with mechanistic pathway dissection and cell-death mode switching, single rigorous study with multiple orthogonal methods","pmids":["29934307"],"is_preprint":false},{"year":2018,"finding":"Following hypoxia-induced ADAM-17 upregulation in metastatic breast cancer stem cells, ADAM-17 sheds the ecto-domain of nectin-4. The soluble nectin-4 ecto-domain physically interacts with integrin-β4 on endothelial cells and promotes angiogenesis via the Src/PI3K/AKT/iNOS pathway (not via Phospho-ERK or NF-κB).","method":"Co-immunoprecipitation of soluble nectin-4 ecto-domain with integrin-β4, pathway inhibitor experiments (Src, PI3K, AKT, iNOS, ERK, NF-κB), in vitro tube formation, in ovo CAM assay, in vivo angiogenesis model, siRNA knockdown of nectin-4 and ADAM-17","journal":"The International Journal of Biochemistry & Cell Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP of soluble ecto-domain with integrin-β4, multiple pathway inhibitors, in vitro and in vivo models, single lab","pmids":["30056265"],"is_preprint":false},{"year":2019,"finding":"Nectin-4 physically cis-interacts with ErbB2 (HER2) through its third immunoglobulin-like (C2) domain binding to domain IV of ErbB2, enhancing ErbB2 dimerization and activation and downstream PI3K/AKT signaling for DNA synthesis. Nectin-4 also cis-interacts with trastuzumab-resistant ErbB2 splice variants (p95-ErbB2 and ErbB2ΔEx16) and enhances their activation, additionally activating JAK-STAT3 signaling for the p95-ErbB2 variant.","method":"Co-immunoprecipitation in breast cancer cell lines (T47D, SUM190-PT), domain-deletion constructs mapping the interaction surfaces, DNA synthesis assay (BrdU), Western blot for pathway activation","journal":"Scientific Reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with domain-deletion mapping, multiple receptor variants tested, functional downstream assays, mechanistically rigorous single study","pmids":["31831814"],"is_preprint":false},{"year":2019,"finding":"NECTIN4 promotes papillary thyroid cancer cell proliferation, migration, invasion, and EMT via the PI3K/AKT pathway; AKT phosphorylation activator SC79 reversed si-NECTIN4 knockdown effects, and AKT inhibitor LY294002 phenocopied siRNA knockdown.","method":"siRNA knockdown, colony formation assay, proliferation assay, migration/invasion assay, Western blot for EMT markers and PI3K/AKT pathway, SC79 rescue and LY294002 pharmacological inhibitor","journal":"Cancer Management and Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function plus pharmacological rescue/phenocopy for pathway placement, single lab","pmids":["31114323"],"is_preprint":false},{"year":2019,"finding":"PPRV (peste des petits ruminants virus) induces an early wave of autophagy upon infection via binding of viral H protein to NECTIN4 receptor, inactivating the AKT-mTOR pathway. This NECTIN4-mediated AKT-mTOR-dependent autophagic wave is a critical early step for control of infection.","method":"Co-immunoprecipitation of viral H protein with NECTIN4, siRNA knockdown of NECTIN4, autophagosome/LC3-II quantification, phospho-AKT/mTOR Western blot, pharmacological mTOR inhibition","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating H-NECTIN4 binding, NECTIN4 siRNA with autophagic pathway readout, single lab","pmids":["31318632"],"is_preprint":false},{"year":2020,"finding":"Nectin-4 is a novel ligand of the immune checkpoint receptor TIGIT; the TIGIT-Nectin-4 interaction inhibits natural killer cell cytotoxicity. Unlike other known TIGIT ligands that also bind additional receptors, Nectin-4 interacts only with TIGIT. Blocking Nectin-4 with antibodies enhanced tumor cell killing in vitro and in vivo.","method":"NK cell staining with Fc-fusion proteins of tumor markers, TIGIT receptor-ligand binding assays, NK cell killing assays (in vitro), in vivo tumor models with blocking antibody","journal":"Journal for Immunotherapy of Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — binding identified by fusion-protein staining, functional NK killing assays in vitro and in vivo, receptor specificity panel; single lab","pmids":["32503945"],"is_preprint":false},{"year":2020,"finding":"Nectin-4 knockdown cells did not form tightly compacted ovarian cancer spheroids, while control cells formed compact spheroids within 24 h. Synthetic peptides derived from nectin-4 (N4-P10) disrupted spheroid formation in a concentration-dependent manner without cytotoxicity, implicating nectin-4-mediated homophilic adhesion in spheroid compaction.","method":"siRNA knockdown of nectin-4, real-time digital photography of spheroid formation, peptide inhibition assays (concentration-response), scrambled peptide control","journal":"International Journal of Molecular Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function plus peptide competition with defined structural readout, single lab, two orthogonal approaches","pmids":["32629816"],"is_preprint":false},{"year":2020,"finding":"ERRα (estrogen-related receptor-α) directly binds the NECTIN4 promoter and enhances its transcription, as shown by chromatin immunoprecipitation and dual-luciferase reporter assays. ERRα-induced Nectin-4 upregulation activates the PI3K/AKT pathway, and Nectin-4 depletion blocks ERRα-induced PI3K/AKT activation and gallbladder cancer cell proliferation/invasion.","method":"ChIP assay, dual-luciferase reporter assay, siRNA knockdown of ERRα and Nectin-4, Western blot for PI3K/AKT pathway, proliferation and invasion assays, in vivo xenograft","journal":"Cancer Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — ChIP and luciferase reporter directly demonstrate ERRα binding the NECTIN4 promoter; epistasis experiment (Nectin-4 KD rescues ERRα OE phenotype) places Nectin-4 downstream of ERRα","pmids":["32030850"],"is_preprint":false},{"year":2021,"finding":"NECTIN4 expression is both necessary and sufficient for sensitivity to the ADC enfortumab vedotin (EV) in luminal and basal subtypes of urothelial bladder cancer cells; stable knockdown of NECTIN4 conferred EV resistance, and overexpression of NECTIN4 in low-expressing cells conferred EV sensitivity.","method":"Stable overexpression and knockdown of NECTIN4 in bladder cancer cell lines, EV drug sensitivity assays (cell proliferation and clonogenic assays)","journal":"Clinical Cancer Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional gain/loss-of-function with drug sensitivity readout, single lab, two cell-biology assays","pmids":["34108177"],"is_preprint":false},{"year":2021,"finding":"NECTIN4 knockdown in A431 cutaneous SCC cells prevented cell-cell attachment, increased cell migration, downregulated ERK signaling, decreased cyclin D1 expression, and inhibited cell proliferation, demonstrating roles for NECTIN4 in cell-cell interactions, migration, and proliferation in SCC.","method":"siRNA knockdown, cell-cell attachment assay, migration assay, Western blot for ERK signaling and cyclin D1, proliferation assay","journal":"Biomedicines","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple downstream pathway readouts, single lab","pmids":["33808400"],"is_preprint":false},{"year":2021,"finding":"Nectin-4 promotes lymphangiogenesis and lymphatic metastasis in breast cancer by stimulating CXCR4 and CXCL12 expression under hypoxia in lymph-node-derived primary cells and modulating the CXCR4/CXCL12-LYVE-1 axis; depletion of Nectin-4 or VEGF-C attenuated LYVE-1 expression, tube formation, and migration.","method":"siRNA knockdown of Nectin-4 and VEGF-C, LYVE-1 lymphatic vessel density quantification, tube formation assay, migration assay, Western blot for CXCR4/CXCL12 and lymphangiogenic markers","journal":"Vascular Pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — loss-of-function with lymphangiogenic readouts but limited direct mechanistic validation of pathway ordering; single lab","pmids":["33945869"],"is_preprint":false},{"year":2023,"finding":"TIGIT recognizes the membrane-distal ectodomain of nectin-4; the TIGIT-nectin-4 interaction is weaker than the characterized TIGIT-nectin-2 interaction. Structure-guided mutagenesis mapped the nectin-4 binding interface on TIGIT.","method":"Surface plasmon resonance (biophysical binding assay), structure-guided mutagenesis of TIGIT","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — quantitative SPR with mutagenesis, single lab, no full structural determination reported","pmids":["37542773"],"is_preprint":false},{"year":2023,"finding":"Nectin-4 regulates senescence-associated cell size enlargement: overexpression of Nectin-4 induced enlarged cell morphology resembling senescent cells, and knockdown of Nectin-4 suppressed the cell size increase during DNA damage-induced senescence without altering senescence induction per se. Nectin-4-dependent cell size increase is mediated by the Src family kinase/PI3K/Rac1 pathway. Nectin-4 knockdown in senescent cells induced apoptosis, with cell size positively correlated with survival.","method":"Overexpression and siRNA knockdown, DNA damage-induced senescence model, single-cell tracking (live imaging), pathway inhibitors (Src/PI3K/Rac1), cell size quantification","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional gain/loss-of-function with cell size and survival readouts plus pharmacological pathway dissection, single lab","pmids":["38062106"],"is_preprint":false},{"year":2020,"finding":"The endo-domain of NECTIN-4 (lacking the extracellular region) translocates to the nucleus by physically interacting with IMPORTIN-α2, where it activates DNA repair and enhances cell growth. The ecto-domain (lacking the signal peptide and cytoplasmic region) localizes to the cytoplasm and specifically activates angiogenesis.","method":"Domain-specific overexpression constructs, co-immunoprecipitation (NECTIN-4 endo-domain with IMPORTIN-α2), subcellular fractionation/immunofluorescence, comet and γ-H2AX assays for DNA repair, in vitro tube formation, in ovo CAM assay","journal":"European Journal of Pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — domain constructs with Co-IP identifying IMPORTIN-α2 interaction, functional assays for each domain; single lab, non-canonical nuclear domain localization requires further validation","pmids":["32603697"],"is_preprint":false}],"current_model":"NECTIN4 is a type I transmembrane immunoglobulin-superfamily cell adhesion molecule that localizes to cadherin-based adherens junctions via its C-terminal interaction with afadin; it mediates homophilic and heterophilic (nectin-1) trans-adhesion through its membrane-distal V domain, activates integrin β4/SHP-2/c-Src and PI3K/AKT/Rac1 signaling to promote anchorage-independent survival, lamellipodia formation, and cell-size regulation, cis-interacts with ErbB2 to enhance its dimerization and downstream PI3K/AKT signaling, functions as the epithelial entry/exit receptor for morbilliviruses (measles, CDV, PPRV) via its V domain, acts as a TIGIT ligand to inhibit NK-cell cytotoxicity, and is transcriptionally regulated by IRF6 in keratinocytes and by ERRα in cancer cells through direct promoter binding."},"narrative":{"mechanistic_narrative":"NECTIN4 is a type I transmembrane immunoglobulin-superfamily cell adhesion molecule that organizes epithelial adherens junctions and, when dysregulated, drives oncogenic adhesion and survival signaling [PMID:11544254, PMID:23682311]. It binds afadin through its C-terminal cytoplasmic tail and co-localizes with afadin at cadherin-based adherens junctions, mediating homophilic trans-adhesion and heterophilic trans-adhesion with nectin-1 specifically through its membrane-distal V (immunoglobulin-like) domain [PMID:11544254]. Homozygous loss-of-function mutations cause ectodermal dysplasia-syndactyly syndrome, with mutant nectin-4 losing nectin-1 binding and disrupting junctional complex localization and actin organization in keratinocytes [PMID:20691405]. NECTIN4-driven cell-to-cell attachment activates a matrix-independent integrin β4/SHP-2/c-Src axis that supports anchorage-independent growth and tumor formation [PMID:23682311], and the same PVRL4/α6β4/Src clustering signal sustains GPX4 expression to protect matrix-detached cells from ferroptosis [PMID:29934307]. Downstream, it engages PI3K/AKT/Rac1 signaling to promote lamellipodia and invasion [PMID:19679554], WNT/β-catenin-dependent stem-cell self-renewal and EMT [PMID:28600142], and a Src-family-kinase/PI3K/Rac1 program controlling senescence-associated cell-size enlargement and survival [PMID:38062106]. NECTIN4 cis-interacts with ErbB2 (HER2) via its C2 domain binding ErbB2 domain IV, enhancing ErbB2 dimerization, activation, and downstream PI3K/AKT signaling, including for trastuzumab-resistant variants [PMID:31831814]. Its expression is driven transcriptionally by IRF6 in keratinocytes [PMID:25387952] and by ERRα binding the NECTIN4 promoter in cancer cells, placing it downstream of ERRα-induced PI3K/AKT activation [PMID:32030850]. Independently, its V domain serves as the high-affinity epithelial entry/exit receptor for morbilliviruses—measles virus, canine distemper virus, and PPRV—through interaction with the viral attachment (H) protein [PMID:22048310, PMID:21901103, PMID:22761370, PMID:24725937, PMID:31318632], and it acts as a TIGIT ligand whose engagement inhibits NK-cell cytotoxicity [PMID:32503945, PMID:37542773]. NECTIN4 expression is necessary and sufficient for sensitivity to the antibody-drug conjugate enfortumab vedotin in urothelial cancer cells [PMID:34108177].","teleology":[{"year":2001,"claim":"Establishing NECTIN4's molecular identity answered whether it is an adhesion molecule and defined its binding partners, anchoring it within the nectin/afadin junctional system.","evidence":"Fc-fusion pulldown, reciprocal Co-IP, in vitro binding, and immunofluorescence co-localization in MDCKII and COS cells with domain-deletion constructs","pmids":["11544254"],"confidence":"High","gaps":["Functional consequence of nectin-1 vs homophilic engagement not resolved","No structural model of the V-domain adhesive interface"]},{"year":2009,"claim":"Linking NECTIN4 expression to Rac1 activation showed it does more than adhere—it transmits signals promoting motility and invasion.","evidence":"siRNA knockdown, overexpression, invasion assays, and Rac1 activation assay in mammalian cells","pmids":["19679554"],"confidence":"Medium","gaps":["Mechanism coupling adhesion to Rac1 not defined","Single lab, cell-line based"]},{"year":2010,"claim":"Human genetics established NECTIN4 as causative for an inherited disease and tied loss of nectin-1 binding directly to junctional and cytoskeletal disruption.","evidence":"Homozygosity mapping, candidate gene sequencing, binding assays and junctional/actin immunofluorescence in patient keratinocytes","pmids":["20691405"],"confidence":"High","gaps":["Tissue-specific basis of ectodermal phenotype incompletely explained","Does not address signaling roles"]},{"year":2011,"claim":"Identification of NECTIN4 as the epithelial measles virus receptor answered how the virus exits the host and defined the V domain as the H-protein binding surface.","evidence":"Surface protein screen, siRNA knockdown, antibody block, binding assays, and basolateral infection of primary airway epithelial sheets (two concurrent papers)","pmids":["22048310","21901103"],"confidence":"High","gaps":["Entry route into the cell not yet defined at this stage","Downregulation mechanism during infection unresolved"]},{"year":2012,"claim":"Extending receptor function to canine distemper virus showed NECTIN4 is a conserved morbillivirus epithelial receptor with implications for neurovirulence.","evidence":"Infection of nectin-4-expressing Vero cells, antibody blocking, and IHC of infected dog tissues","pmids":["22761370"],"confidence":"Medium","gaps":["In vivo causality vs correlation in neurons not fully separated","Single lab"]},{"year":2013,"claim":"A gain-of-function screen revealed how NECTIN4-driven cell-to-cell attachment promotes transformation, defining a matrix-independent integrin β4/SHP-2/c-Src survival axis.","evidence":"Anchorage-independence screen, pathway epistasis with integrin β4/SHP-2/c-Src, and antibody-blockade xenograft","pmids":["23682311"],"confidence":"High","gaps":["How clustering activates integrin β4 in trans not mechanistically resolved","Generality across tumor types untested here"]},{"year":2014,"claim":"Mutagenesis defined the specific V-domain residues required for morbillivirus entry, mapping the receptor-virus interface at amino-acid resolution.","evidence":"Domain-deletion and site-directed mutagenesis with virus entry and cell-to-cell spread assays for CDV","pmids":["24725937"],"confidence":"Medium","gaps":["No co-crystal structure of the complex","Single lab"]},{"year":2017,"claim":"Defining the measles entry route showed NECTIN4 drives a dynamin-independent, actin/Rac1/PAK1-dependent macropinocytosis, connecting its signaling outputs to viral uptake.","evidence":"Endocytic inhibitors, siRNA of PAK1/Rac1, phalloidin staining, fluid-uptake assay, and fluorescent MeV reporters","pmids":["28250131"],"confidence":"Medium","gaps":["Direct link between receptor engagement and Rac1/PAK1 activation not shown","Cell-line specific"]},{"year":2017,"claim":"Placing NECTIN4 upstream of WNT/β-catenin via PI3K/Akt connected it to cancer stem-cell self-renewal, EMT, and metastasis.","evidence":"Bidirectional knockdown/overexpression, invasion/EMT assays, in vivo models, and patient samples with pathway Western blots","pmids":["28600142"],"confidence":"Medium","gaps":["Direct molecular link between NECTIN4 and PI3K not defined","Single lab"]},{"year":2018,"claim":"Demonstrating that NECTIN4 clustering sustains GPX4 to suppress ferroptosis revealed a context-dependent role in matrix-detached cell survival.","evidence":"PVRL4 knockdown/antibody block, α6β4 integrin KO, lipid peroxidation and ferroptosis/apoptosis assays under detachment","pmids":["29934307"],"confidence":"High","gaps":["Molecular link from clustering to GPX4 regulation unresolved","Switch logic between death modes incompletely defined"]},{"year":2018,"claim":"Identifying ADAM-17 shedding of the NECTIN4 ectodomain and its integrin-β4-driven pro-angiogenic action established a paracrine, cleavage-generated function.","evidence":"Co-IP of soluble ectodomain with integrin-β4, pathway inhibitors, tube formation, CAM and in vivo angiogenesis assays under hypoxia","pmids":["30056265"],"confidence":"Medium","gaps":["Cleavage site and physiological shedding regulation not fully defined","Single lab"]},{"year":2019,"claim":"Mapping the NECTIN4 C2-domain/ErbB2 domain IV cis-interaction showed it functions as a co-receptor amplifying HER2 signaling, including for trastuzumab-resistant variants.","evidence":"Reciprocal Co-IP with domain-deletion mapping in breast cancer lines, BrdU DNA synthesis, and pathway Western blots","pmids":["31831814"],"confidence":"High","gaps":["Structural basis of cis-dimer enhancement not resolved","In vivo relevance to HER2 therapy resistance untested here"]},{"year":2019,"claim":"Pharmacological epistasis placed NECTIN4-driven proliferation, migration and EMT in papillary thyroid cancer squarely on the PI3K/AKT axis.","evidence":"siRNA knockdown with SC79 rescue and LY294002 phenocopy plus EMT/pathway Western blots","pmids":["31114323"],"confidence":"Medium","gaps":["Upstream link from NECTIN4 to PI3K not defined","Single tumor type, single lab"]},{"year":2019,"claim":"Showing PPRV H-protein binding to NECTIN4 triggers an AKT-mTOR-inactivating autophagic wave extended its morbillivirus-receptor role to early infection control.","evidence":"Co-IP of viral H with NECTIN4, siRNA knockdown, LC3-II quantification, phospho-AKT/mTOR blots, and mTOR inhibition","pmids":["31318632"],"confidence":"Medium","gaps":["Mechanism coupling receptor engagement to AKT-mTOR not defined","Single lab"]},{"year":2020,"claim":"Identifying NECTIN4 as a TIGIT ligand that inhibits NK cytotoxicity defined an immune-evasion function distinct from other TIGIT ligands.","evidence":"Fc-fusion staining, TIGIT binding assays, NK killing assays, and in vivo tumor models with blocking antibody","pmids":["32503945"],"confidence":"Medium","gaps":["Affinity and structural interface defined only later","Single lab"]},{"year":2020,"claim":"ChIP and reporter assays established ERRα as a direct transcriptional driver of NECTIN4, placing NECTIN4 downstream of ERRα-induced PI3K/AKT signaling.","evidence":"ChIP, dual-luciferase reporter, siRNA epistasis, pathway Western blots, and xenograft in gallbladder cancer","pmids":["32030850"],"confidence":"High","gaps":["Other transcriptional regulators across tissues not addressed","Direct NECTIN4-to-PI3K coupling not shown"]},{"year":2020,"claim":"Loss-of-function and peptide competition implicated NECTIN4 homophilic adhesion in compact ovarian cancer spheroid formation.","evidence":"siRNA knockdown, real-time spheroid imaging, and concentration-dependent N4-derived peptide inhibition with scrambled control","pmids":["32629816"],"confidence":"Medium","gaps":["Signaling consequences of spheroid compaction not addressed","Single lab"]},{"year":2020,"claim":"A domain-dissection study proposed cleaved NECTIN4 fragments have separable nuclear (DNA repair, via IMPORTIN-α2) and cytoplasmic (angiogenesis) functions.","evidence":"Domain-specific constructs, Co-IP with IMPORTIN-α2, fractionation/IF, comet/γ-H2AX, tube formation, and CAM assays","pmids":["32603697"],"confidence":"Low","gaps":["Non-canonical nuclear localization requires independent validation","Physiological generation of these fragments not established","Single lab"]},{"year":2021,"claim":"Establishing that NECTIN4 expression is necessary and sufficient for enfortumab vedotin sensitivity provided the mechanistic rationale for the ADC in urothelial cancer.","evidence":"Stable overexpression and knockdown in bladder cancer lines with drug-sensitivity and clonogenic assays","pmids":["34108177"],"confidence":"Medium","gaps":["Quantitative expression threshold for response not defined","Resistance mechanisms beyond expression loss untested"]},{"year":2021,"claim":"Knockdown in cutaneous SCC linked NECTIN4 to ERK signaling and cyclin D1-dependent proliferation alongside its adhesion role.","evidence":"siRNA knockdown, attachment/migration assays, ERK and cyclin D1 Western blots, proliferation assay in A431 cells","pmids":["33808400"],"confidence":"Medium","gaps":["Direct coupling of NECTIN4 to ERK not shown","Single cell line"]},{"year":2021,"claim":"NECTIN4 was associated with hypoxia-driven lymphangiogenesis and lymphatic metastasis via CXCR4/CXCL12-LYVE-1 modulation in breast cancer.","evidence":"siRNA knockdown of Nectin-4 and VEGF-C, LYVE-1 density, tube formation, migration, and pathway Western blots","pmids":["33945869"],"confidence":"Low","gaps":["Pathway ordering not directly validated","Single lab, limited mechanistic depth"]},{"year":2023,"claim":"Biophysical mapping quantified the TIGIT-nectin-4 interaction and located its interface, refining the immune-checkpoint ligand model.","evidence":"Surface plasmon resonance and structure-guided mutagenesis of TIGIT","pmids":["37542773"],"confidence":"Medium","gaps":["No full co-crystal structure","Weaker affinity than TIGIT-nectin-2; functional significance of the differential not resolved"]},{"year":2023,"claim":"Linking NECTIN4 to Src-family-kinase/PI3K/Rac1-mediated senescence-associated cell-size enlargement and survival expanded its signaling role beyond proliferation and adhesion.","evidence":"Bidirectional overexpression/knockdown in a DNA-damage senescence model, single-cell live imaging, and Src/PI3K/Rac1 inhibitors","pmids":["38062106"],"confidence":"Medium","gaps":["Mechanism linking cell size to survival not fully resolved","Single lab"]},{"year":null,"claim":"How NECTIN4 adhesion and clustering are physically coupled to its diverse intracellular signaling outputs (integrin β4/Src, PI3K/AKT, Rac1, WNT) and a unifying structural basis for its adhesive, viral-receptor, and HER2 co-receptor interfaces remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No 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NECTIN-4 and predictive biomarkers in sarcomatoid and rhabdoid bladder urothelial carcinoma.","date":"2024","source":"Pathologica","url":"https://pubmed.ncbi.nlm.nih.gov/38482675","citation_count":13,"is_preprint":false},{"pmid":"30767361","id":"PMC_30767361","title":"Nectin-4 and p63 immunohistochemical expression in canine prostate tumourigenesis.","date":"2019","source":"Veterinary and comparative oncology","url":"https://pubmed.ncbi.nlm.nih.gov/30767361","citation_count":13,"is_preprint":false},{"pmid":"36497350","id":"PMC_36497350","title":"Nectin-4 as Blood-Based Biomarker Enables Detection of Early Ovarian Cancer Stages.","date":"2022","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/36497350","citation_count":13,"is_preprint":false},{"pmid":"38059449","id":"PMC_38059449","title":"Nectin-4 has emerged as a compelling target for breast cancer.","date":"2023","source":"European journal of 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Nectin-4 trans-interacts heterophilically with nectin-1 (but not nectin-2, nectin-3, or PVR/CD155) through its V (membrane-distal immunoglobulin-like) domain, and also exhibits homophilic binding.\",\n      \"method\": \"Soluble chimeric Fc-fusion pulldown assays, reciprocal co-immunoprecipitation in COS cells, in vitro protein-protein interaction assays, co-localization by immunofluorescence microscopy, domain-deletion constructs\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (reciprocal Co-IP, Fc-fusion pulldown, in vitro binding, co-localization) in a single rigorous study; interaction specificity confirmed by negative controls with nectin-2, -3, PVR\",\n      \"pmids\": [\"11544254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Exogenous expression of Nectin-4 in mammalian cells increased lamellipodia formation and invasive ability through activation of the small GTPase Rac1.\",\n      \"method\": \"siRNA knockdown, exogenous overexpression, cell invasion assays, Rac1 activation assay\",\n      \"journal\": \"Cancer Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function in cell lines with specific GTPase readout, single lab, two orthogonal approaches\",\n      \"pmids\": [\"19679554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Homozygous loss-of-function mutations in PVRL4/nectin-4 cause ectodermal dysplasia-syndactyly syndrome (EDSS). In patient keratinocytes, mutated nectin-4 lost its ability to bind nectin-1, and adherens junction complexes (nectin-afadin and cadherin-catenin) showed altered membrane localization accompanied by actin cytoskeleton reorganization in hair follicle structures.\",\n      \"method\": \"Homozygosity mapping, candidate gene sequencing, co-immunoprecipitation/binding assay in patient keratinocytes, immunofluorescence of adherens junction components, actin cytoskeleton staining\",\n      \"journal\": \"American Journal of Human Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetics (multiple families, two independent mutations) combined with functional cell biology (loss of nectin-1 binding, disrupted junctional complexes) in disease-relevant cells\",\n      \"pmids\": [\"20691405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Nectin-4 (PVRL4), an adherens junction protein of the immunoglobulin superfamily, functions as the epithelial exit receptor for measles virus. Its membrane-distal (V) domain interacts with the viral attachment (H) protein with high affinity. Nectin-4 supports MV entry and non-cytopathic lateral spread in well-differentiated primary human airway epithelial sheets infected basolaterally; MV infection downregulates nectin-4 surface expression.\",\n      \"method\": \"Functional surface protein screen, siRNA knockdown, antibody blocking, flow cytometry, confocal microscopy, surface biotinylation, virus binding assay in primary airway epithelial cells and cancer cell lines\",\n      \"journal\": \"Nature / PLoS Pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — independently replicated in two concurrent papers (PMID 22048310 and 21901103) using multiple orthogonal methods including receptor knockdown, antibody block, binding assays, and primary tissue infection\",\n      \"pmids\": [\"22048310\", \"21901103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Wild-type canine distemper virus (CDV) uses nectin-4 as an epithelial cell receptor; infection is blocked by anti-nectin-4 antibody, and CDV antigen co-localises with nectin-4-positive neurons and epithelial cells in vivo, implicating nectin-4 in CDV neurovirulence.\",\n      \"method\": \"Infection of Vero cells expressing dog nectin-4, antibody blocking assay, immunohistochemistry of infected dog tissues\",\n      \"journal\": \"Journal of Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based infection assay with antibody block plus in vivo IHC correlation, single lab\",\n      \"pmids\": [\"22761370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PVRL4/Nectin-4 promotes anchorage-independent growth by driving cell-to-cell attachment and activating a matrix-independent integrin β4/SHP-2/c-Src signaling axis, which is required for breast cancer cell transformation. Blocking PVRL4-driven cell-to-cell attachment with monoclonal antibodies inhibited orthotopic tumor growth in vivo.\",\n      \"method\": \"Gain-of-function screen for anchorage independence, epistasis with integrin β4/SHP-2/c-Src pathway components (knockdown/inhibition), in vivo xenograft with anti-PVRL4 antibody treatment\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional screen identifying PVRL4, pathway epistasis (multiple components), and in vivo validation with antibody blockade; multiple orthogonal approaches in a single rigorous study\",\n      \"pmids\": [\"23682311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The V domain of PVRL4/nectin-4 is critical for canine distemper virus (CDV) entry and cell-to-cell spread. Four specific amino acid residues in the V domain of dog PVRL4 and two in the CDV hemagglutinin were essential for receptor-mediated virus entry.\",\n      \"method\": \"Domain-deletion and site-directed mutagenesis constructs, virus entry and cell-to-cell spread assays\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis defining essential residues, single lab\",\n      \"pmids\": [\"24725937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PVRL4 (nectin-4) transcriptional expression is not directly regulated by p63 (unlike nectin-1), but is controlled by the transcription factor IRF6: IRF6 depletion in keratinocytes reduced Pvrl4 expression, and Pvrl4 was downregulated in AEC syndrome keratinocytes in parallel with decreased IRF6.\",\n      \"method\": \"p63 knockout mouse skin analysis, siRNA depletion of p63 and IRF6 in primary keratinocytes, chromatin immunoprecipitation (p63 binds Pvrl1 but not Pvrl4), RT-qPCR in patient-derived AEC keratinocytes and conditional mouse model\",\n      \"journal\": \"Experimental Dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP for negative result (p63 does not bind Pvrl4), IRF6 loss-of-function with gene expression readout, multiple experimental models in one study\",\n      \"pmids\": [\"25387952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Measles virus enters PVRL4-positive breast cancer and colon cancer cells via a PVRL4-mediated macropinocytosis pathway that is dynamin-independent but requires actin polymerization, Rac1, and PAK1 (in MCF7 cells); MV entry induced membrane ruffles and elevated fluid uptake.\",\n      \"method\": \"Pharmacological inhibitors of endocytic pathways (EIPA, dynasore, actin inhibitors), siRNA knockdown of PAK1 and Rac1, phalloidin staining, fluid-phase uptake assay, recombinant fluorescent MeV reporters\",\n      \"journal\": \"Journal of Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple inhibitors and siRNA knockdowns with defined pathway readouts, single lab\",\n      \"pmids\": [\"28250131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Nectin-4 is a marker for breast cancer stem cells and activates WNT/β-catenin signaling via the PI3K/Akt axis to support BCSC self-renewal. Nectin-4 depletion inhibited EMT, metastasis, invasion, and the WNT/β-catenin pathway; overexpression in null cells induced WNT/β-catenin signaling via PI3K/Akt.\",\n      \"method\": \"siRNA knockdown, stable overexpression in nectin-4-null cells, in vitro invasion/EMT assays, in vivo mouse models, ex vivo patient samples, Western blot for pathway components\",\n      \"journal\": \"The International Journal of Biochemistry & Cell Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional gain/loss-of-function with defined pathway readouts, single lab, in vitro and in vivo\",\n      \"pmids\": [\"28600142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PVRL4/Nectin-4 mediates spontaneous cell clustering of matrix-detached epithelial and carcinoma cells. This clustering activates a PVRL4/α6β4 integrin/Src signaling axis that sustains GPX4 expression and protects against lipid peroxidation/ferroptosis. In the absence of α6β4, PVRL4-mediated clustering paradoxically increased lipid peroxidation and triggered ferroptosis; inhibiting clustering shifted cell death from ferroptosis to apoptosis.\",\n      \"method\": \"Antibody blocking and siRNA knockdown of PVRL4, α6β4 integrin knockout/knockdown, lipid peroxidation assays, GPX4 expression analysis, ferroptosis/apoptosis assays under matrix-detached conditions\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic and pharmacological perturbations (PVRL4 KD, α6β4 KO, antibody blocking) with mechanistic pathway dissection and cell-death mode switching, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"29934307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Following hypoxia-induced ADAM-17 upregulation in metastatic breast cancer stem cells, ADAM-17 sheds the ecto-domain of nectin-4. The soluble nectin-4 ecto-domain physically interacts with integrin-β4 on endothelial cells and promotes angiogenesis via the Src/PI3K/AKT/iNOS pathway (not via Phospho-ERK or NF-κB).\",\n      \"method\": \"Co-immunoprecipitation of soluble nectin-4 ecto-domain with integrin-β4, pathway inhibitor experiments (Src, PI3K, AKT, iNOS, ERK, NF-κB), in vitro tube formation, in ovo CAM assay, in vivo angiogenesis model, siRNA knockdown of nectin-4 and ADAM-17\",\n      \"journal\": \"The International Journal of Biochemistry & Cell Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP of soluble ecto-domain with integrin-β4, multiple pathway inhibitors, in vitro and in vivo models, single lab\",\n      \"pmids\": [\"30056265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Nectin-4 physically cis-interacts with ErbB2 (HER2) through its third immunoglobulin-like (C2) domain binding to domain IV of ErbB2, enhancing ErbB2 dimerization and activation and downstream PI3K/AKT signaling for DNA synthesis. Nectin-4 also cis-interacts with trastuzumab-resistant ErbB2 splice variants (p95-ErbB2 and ErbB2ΔEx16) and enhances their activation, additionally activating JAK-STAT3 signaling for the p95-ErbB2 variant.\",\n      \"method\": \"Co-immunoprecipitation in breast cancer cell lines (T47D, SUM190-PT), domain-deletion constructs mapping the interaction surfaces, DNA synthesis assay (BrdU), Western blot for pathway activation\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with domain-deletion mapping, multiple receptor variants tested, functional downstream assays, mechanistically rigorous single study\",\n      \"pmids\": [\"31831814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NECTIN4 promotes papillary thyroid cancer cell proliferation, migration, invasion, and EMT via the PI3K/AKT pathway; AKT phosphorylation activator SC79 reversed si-NECTIN4 knockdown effects, and AKT inhibitor LY294002 phenocopied siRNA knockdown.\",\n      \"method\": \"siRNA knockdown, colony formation assay, proliferation assay, migration/invasion assay, Western blot for EMT markers and PI3K/AKT pathway, SC79 rescue and LY294002 pharmacological inhibitor\",\n      \"journal\": \"Cancer Management and Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function plus pharmacological rescue/phenocopy for pathway placement, single lab\",\n      \"pmids\": [\"31114323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PPRV (peste des petits ruminants virus) induces an early wave of autophagy upon infection via binding of viral H protein to NECTIN4 receptor, inactivating the AKT-mTOR pathway. This NECTIN4-mediated AKT-mTOR-dependent autophagic wave is a critical early step for control of infection.\",\n      \"method\": \"Co-immunoprecipitation of viral H protein with NECTIN4, siRNA knockdown of NECTIN4, autophagosome/LC3-II quantification, phospho-AKT/mTOR Western blot, pharmacological mTOR inhibition\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating H-NECTIN4 binding, NECTIN4 siRNA with autophagic pathway readout, single lab\",\n      \"pmids\": [\"31318632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Nectin-4 is a novel ligand of the immune checkpoint receptor TIGIT; the TIGIT-Nectin-4 interaction inhibits natural killer cell cytotoxicity. Unlike other known TIGIT ligands that also bind additional receptors, Nectin-4 interacts only with TIGIT. Blocking Nectin-4 with antibodies enhanced tumor cell killing in vitro and in vivo.\",\n      \"method\": \"NK cell staining with Fc-fusion proteins of tumor markers, TIGIT receptor-ligand binding assays, NK cell killing assays (in vitro), in vivo tumor models with blocking antibody\",\n      \"journal\": \"Journal for Immunotherapy of Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — binding identified by fusion-protein staining, functional NK killing assays in vitro and in vivo, receptor specificity panel; single lab\",\n      \"pmids\": [\"32503945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Nectin-4 knockdown cells did not form tightly compacted ovarian cancer spheroids, while control cells formed compact spheroids within 24 h. Synthetic peptides derived from nectin-4 (N4-P10) disrupted spheroid formation in a concentration-dependent manner without cytotoxicity, implicating nectin-4-mediated homophilic adhesion in spheroid compaction.\",\n      \"method\": \"siRNA knockdown of nectin-4, real-time digital photography of spheroid formation, peptide inhibition assays (concentration-response), scrambled peptide control\",\n      \"journal\": \"International Journal of Molecular Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function plus peptide competition with defined structural readout, single lab, two orthogonal approaches\",\n      \"pmids\": [\"32629816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ERRα (estrogen-related receptor-α) directly binds the NECTIN4 promoter and enhances its transcription, as shown by chromatin immunoprecipitation and dual-luciferase reporter assays. ERRα-induced Nectin-4 upregulation activates the PI3K/AKT pathway, and Nectin-4 depletion blocks ERRα-induced PI3K/AKT activation and gallbladder cancer cell proliferation/invasion.\",\n      \"method\": \"ChIP assay, dual-luciferase reporter assay, siRNA knockdown of ERRα and Nectin-4, Western blot for PI3K/AKT pathway, proliferation and invasion assays, in vivo xenograft\",\n      \"journal\": \"Cancer Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — ChIP and luciferase reporter directly demonstrate ERRα binding the NECTIN4 promoter; epistasis experiment (Nectin-4 KD rescues ERRα OE phenotype) places Nectin-4 downstream of ERRα\",\n      \"pmids\": [\"32030850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NECTIN4 expression is both necessary and sufficient for sensitivity to the ADC enfortumab vedotin (EV) in luminal and basal subtypes of urothelial bladder cancer cells; stable knockdown of NECTIN4 conferred EV resistance, and overexpression of NECTIN4 in low-expressing cells conferred EV sensitivity.\",\n      \"method\": \"Stable overexpression and knockdown of NECTIN4 in bladder cancer cell lines, EV drug sensitivity assays (cell proliferation and clonogenic assays)\",\n      \"journal\": \"Clinical Cancer Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional gain/loss-of-function with drug sensitivity readout, single lab, two cell-biology assays\",\n      \"pmids\": [\"34108177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NECTIN4 knockdown in A431 cutaneous SCC cells prevented cell-cell attachment, increased cell migration, downregulated ERK signaling, decreased cyclin D1 expression, and inhibited cell proliferation, demonstrating roles for NECTIN4 in cell-cell interactions, migration, and proliferation in SCC.\",\n      \"method\": \"siRNA knockdown, cell-cell attachment assay, migration assay, Western blot for ERK signaling and cyclin D1, proliferation assay\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple downstream pathway readouts, single lab\",\n      \"pmids\": [\"33808400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Nectin-4 promotes lymphangiogenesis and lymphatic metastasis in breast cancer by stimulating CXCR4 and CXCL12 expression under hypoxia in lymph-node-derived primary cells and modulating the CXCR4/CXCL12-LYVE-1 axis; depletion of Nectin-4 or VEGF-C attenuated LYVE-1 expression, tube formation, and migration.\",\n      \"method\": \"siRNA knockdown of Nectin-4 and VEGF-C, LYVE-1 lymphatic vessel density quantification, tube formation assay, migration assay, Western blot for CXCR4/CXCL12 and lymphangiogenic markers\",\n      \"journal\": \"Vascular Pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — loss-of-function with lymphangiogenic readouts but limited direct mechanistic validation of pathway ordering; single lab\",\n      \"pmids\": [\"33945869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TIGIT recognizes the membrane-distal ectodomain of nectin-4; the TIGIT-nectin-4 interaction is weaker than the characterized TIGIT-nectin-2 interaction. Structure-guided mutagenesis mapped the nectin-4 binding interface on TIGIT.\",\n      \"method\": \"Surface plasmon resonance (biophysical binding assay), structure-guided mutagenesis of TIGIT\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — quantitative SPR with mutagenesis, single lab, no full structural determination reported\",\n      \"pmids\": [\"37542773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Nectin-4 regulates senescence-associated cell size enlargement: overexpression of Nectin-4 induced enlarged cell morphology resembling senescent cells, and knockdown of Nectin-4 suppressed the cell size increase during DNA damage-induced senescence without altering senescence induction per se. Nectin-4-dependent cell size increase is mediated by the Src family kinase/PI3K/Rac1 pathway. Nectin-4 knockdown in senescent cells induced apoptosis, with cell size positively correlated with survival.\",\n      \"method\": \"Overexpression and siRNA knockdown, DNA damage-induced senescence model, single-cell tracking (live imaging), pathway inhibitors (Src/PI3K/Rac1), cell size quantification\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional gain/loss-of-function with cell size and survival readouts plus pharmacological pathway dissection, single lab\",\n      \"pmids\": [\"38062106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The endo-domain of NECTIN-4 (lacking the extracellular region) translocates to the nucleus by physically interacting with IMPORTIN-α2, where it activates DNA repair and enhances cell growth. The ecto-domain (lacking the signal peptide and cytoplasmic region) localizes to the cytoplasm and specifically activates angiogenesis.\",\n      \"method\": \"Domain-specific overexpression constructs, co-immunoprecipitation (NECTIN-4 endo-domain with IMPORTIN-α2), subcellular fractionation/immunofluorescence, comet and γ-H2AX assays for DNA repair, in vitro tube formation, in ovo CAM assay\",\n      \"journal\": \"European Journal of Pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — domain constructs with Co-IP identifying IMPORTIN-α2 interaction, functional assays for each domain; single lab, non-canonical nuclear domain localization requires further validation\",\n      \"pmids\": [\"32603697\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NECTIN4 is a type I transmembrane immunoglobulin-superfamily cell adhesion molecule that localizes to cadherin-based adherens junctions via its C-terminal interaction with afadin; it mediates homophilic and heterophilic (nectin-1) trans-adhesion through its membrane-distal V domain, activates integrin β4/SHP-2/c-Src and PI3K/AKT/Rac1 signaling to promote anchorage-independent survival, lamellipodia formation, and cell-size regulation, cis-interacts with ErbB2 to enhance its dimerization and downstream PI3K/AKT signaling, functions as the epithelial entry/exit receptor for morbilliviruses (measles, CDV, PPRV) via its V domain, acts as a TIGIT ligand to inhibit NK-cell cytotoxicity, and is transcriptionally regulated by IRF6 in keratinocytes and by ERRα in cancer cells through direct promoter binding.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NECTIN4 is a type I transmembrane immunoglobulin-superfamily cell adhesion molecule that organizes epithelial adherens junctions and, when dysregulated, drives oncogenic adhesion and survival signaling [#0, #5]. It binds afadin through its C-terminal cytoplasmic tail and co-localizes with afadin at cadherin-based adherens junctions, mediating homophilic trans-adhesion and heterophilic trans-adhesion with nectin-1 specifically through its membrane-distal V (immunoglobulin-like) domain [#0]. Homozygous loss-of-function mutations cause ectodermal dysplasia-syndactyly syndrome, with mutant nectin-4 losing nectin-1 binding and disrupting junctional complex localization and actin organization in keratinocytes [#2]. NECTIN4-driven cell-to-cell attachment activates a matrix-independent integrin \\u03b24/SHP-2/c-Src axis that supports anchorage-independent growth and tumor formation [#5], and the same PVRL4/\\u03b16\\u03b24/Src clustering signal sustains GPX4 expression to protect matrix-detached cells from ferroptosis [#10]. Downstream, it engages PI3K/AKT/Rac1 signaling to promote lamellipodia and invasion [#1], WNT/\\u03b2-catenin-dependent stem-cell self-renewal and EMT [#9], and a Src-family-kinase/PI3K/Rac1 program controlling senescence-associated cell-size enlargement and survival [#22]. NECTIN4 cis-interacts with ErbB2 (HER2) via its C2 domain binding ErbB2 domain IV, enhancing ErbB2 dimerization, activation, and downstream PI3K/AKT signaling, including for trastuzumab-resistant variants [#12]. Its expression is driven transcriptionally by IRF6 in keratinocytes [#7] and by ERR\\u03b1 binding the NECTIN4 promoter in cancer cells, placing it downstream of ERR\\u03b1-induced PI3K/AKT activation [#17]. Independently, its V domain serves as the high-affinity epithelial entry/exit receptor for morbilliviruses\\u2014measles virus, canine distemper virus, and PPRV\\u2014through interaction with the viral attachment (H) protein [#3, #4, #6, #14], and it acts as a TIGIT ligand whose engagement inhibits NK-cell cytotoxicity [#15, #21]. NECTIN4 expression is necessary and sufficient for sensitivity to the antibody-drug conjugate enfortumab vedotin in urothelial cancer cells [#18].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing NECTIN4's molecular identity answered whether it is an adhesion molecule and defined its binding partners, anchoring it within the nectin/afadin junctional system.\",\n      \"evidence\": \"Fc-fusion pulldown, reciprocal Co-IP, in vitro binding, and immunofluorescence co-localization in MDCKII and COS cells with domain-deletion constructs\",\n      \"pmids\": [\"11544254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of nectin-1 vs homophilic engagement not resolved\", \"No structural model of the V-domain adhesive interface\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linking NECTIN4 expression to Rac1 activation showed it does more than adhere\\u2014it transmits signals promoting motility and invasion.\",\n      \"evidence\": \"siRNA knockdown, overexpression, invasion assays, and Rac1 activation assay in mammalian cells\",\n      \"pmids\": [\"19679554\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism coupling adhesion to Rac1 not defined\", \"Single lab, cell-line based\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Human genetics established NECTIN4 as causative for an inherited disease and tied loss of nectin-1 binding directly to junctional and cytoskeletal disruption.\",\n      \"evidence\": \"Homozygosity mapping, candidate gene sequencing, binding assays and junctional/actin immunofluorescence in patient keratinocytes\",\n      \"pmids\": [\"20691405\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific basis of ectodermal phenotype incompletely explained\", \"Does not address signaling roles\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of NECTIN4 as the epithelial measles virus receptor answered how the virus exits the host and defined the V domain as the H-protein binding surface.\",\n      \"evidence\": \"Surface protein screen, siRNA knockdown, antibody block, binding assays, and basolateral infection of primary airway epithelial sheets (two concurrent papers)\",\n      \"pmids\": [\"22048310\", \"21901103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Entry route into the cell not yet defined at this stage\", \"Downregulation mechanism during infection unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extending receptor function to canine distemper virus showed NECTIN4 is a conserved morbillivirus epithelial receptor with implications for neurovirulence.\",\n      \"evidence\": \"Infection of nectin-4-expressing Vero cells, antibody blocking, and IHC of infected dog tissues\",\n      \"pmids\": [\"22761370\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo causality vs correlation in neurons not fully separated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A gain-of-function screen revealed how NECTIN4-driven cell-to-cell attachment promotes transformation, defining a matrix-independent integrin \\u03b24/SHP-2/c-Src survival axis.\",\n      \"evidence\": \"Anchorage-independence screen, pathway epistasis with integrin \\u03b24/SHP-2/c-Src, and antibody-blockade xenograft\",\n      \"pmids\": [\"23682311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How clustering activates integrin \\u03b24 in trans not mechanistically resolved\", \"Generality across tumor types untested here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Mutagenesis defined the specific V-domain residues required for morbillivirus entry, mapping the receptor-virus interface at amino-acid resolution.\",\n      \"evidence\": \"Domain-deletion and site-directed mutagenesis with virus entry and cell-to-cell spread assays for CDV\",\n      \"pmids\": [\"24725937\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No co-crystal structure of the complex\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defining the measles entry route showed NECTIN4 drives a dynamin-independent, actin/Rac1/PAK1-dependent macropinocytosis, connecting its signaling outputs to viral uptake.\",\n      \"evidence\": \"Endocytic inhibitors, siRNA of PAK1/Rac1, phalloidin staining, fluid-uptake assay, and fluorescent MeV reporters\",\n      \"pmids\": [\"28250131\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between receptor engagement and Rac1/PAK1 activation not shown\", \"Cell-line specific\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placing NECTIN4 upstream of WNT/\\u03b2-catenin via PI3K/Akt connected it to cancer stem-cell self-renewal, EMT, and metastasis.\",\n      \"evidence\": \"Bidirectional knockdown/overexpression, invasion/EMT assays, in vivo models, and patient samples with pathway Western blots\",\n      \"pmids\": [\"28600142\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link between NECTIN4 and PI3K not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that NECTIN4 clustering sustains GPX4 to suppress ferroptosis revealed a context-dependent role in matrix-detached cell survival.\",\n      \"evidence\": \"PVRL4 knockdown/antibody block, \\u03b16\\u03b24 integrin KO, lipid peroxidation and ferroptosis/apoptosis assays under detachment\",\n      \"pmids\": [\"29934307\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from clustering to GPX4 regulation unresolved\", \"Switch logic between death modes incompletely defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identifying ADAM-17 shedding of the NECTIN4 ectodomain and its integrin-\\u03b24-driven pro-angiogenic action established a paracrine, cleavage-generated function.\",\n      \"evidence\": \"Co-IP of soluble ectodomain with integrin-\\u03b24, pathway inhibitors, tube formation, CAM and in vivo angiogenesis assays under hypoxia\",\n      \"pmids\": [\"30056265\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cleavage site and physiological shedding regulation not fully defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mapping the NECTIN4 C2-domain/ErbB2 domain IV cis-interaction showed it functions as a co-receptor amplifying HER2 signaling, including for trastuzumab-resistant variants.\",\n      \"evidence\": \"Reciprocal Co-IP with domain-deletion mapping in breast cancer lines, BrdU DNA synthesis, and pathway Western blots\",\n      \"pmids\": [\"31831814\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of cis-dimer enhancement not resolved\", \"In vivo relevance to HER2 therapy resistance untested here\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Pharmacological epistasis placed NECTIN4-driven proliferation, migration and EMT in papillary thyroid cancer squarely on the PI3K/AKT axis.\",\n      \"evidence\": \"siRNA knockdown with SC79 rescue and LY294002 phenocopy plus EMT/pathway Western blots\",\n      \"pmids\": [\"31114323\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream link from NECTIN4 to PI3K not defined\", \"Single tumor type, single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showing PPRV H-protein binding to NECTIN4 triggers an AKT-mTOR-inactivating autophagic wave extended its morbillivirus-receptor role to early infection control.\",\n      \"evidence\": \"Co-IP of viral H with NECTIN4, siRNA knockdown, LC3-II quantification, phospho-AKT/mTOR blots, and mTOR inhibition\",\n      \"pmids\": [\"31318632\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism coupling receptor engagement to AKT-mTOR not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying NECTIN4 as a TIGIT ligand that inhibits NK cytotoxicity defined an immune-evasion function distinct from other TIGIT ligands.\",\n      \"evidence\": \"Fc-fusion staining, TIGIT binding assays, NK killing assays, and in vivo tumor models with blocking antibody\",\n      \"pmids\": [\"32503945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Affinity and structural interface defined only later\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"ChIP and reporter assays established ERR\\u03b1 as a direct transcriptional driver of NECTIN4, placing NECTIN4 downstream of ERR\\u03b1-induced PI3K/AKT signaling.\",\n      \"evidence\": \"ChIP, dual-luciferase reporter, siRNA epistasis, pathway Western blots, and xenograft in gallbladder cancer\",\n      \"pmids\": [\"32030850\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other transcriptional regulators across tissues not addressed\", \"Direct NECTIN4-to-PI3K coupling not shown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Loss-of-function and peptide competition implicated NECTIN4 homophilic adhesion in compact ovarian cancer spheroid formation.\",\n      \"evidence\": \"siRNA knockdown, real-time spheroid imaging, and concentration-dependent N4-derived peptide inhibition with scrambled control\",\n      \"pmids\": [\"32629816\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling consequences of spheroid compaction not addressed\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A domain-dissection study proposed cleaved NECTIN4 fragments have separable nuclear (DNA repair, via IMPORTIN-\\u03b12) and cytoplasmic (angiogenesis) functions.\",\n      \"evidence\": \"Domain-specific constructs, Co-IP with IMPORTIN-\\u03b12, fractionation/IF, comet/\\u03b3-H2AX, tube formation, and CAM assays\",\n      \"pmids\": [\"32603697\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Non-canonical nuclear localization requires independent validation\", \"Physiological generation of these fragments not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Establishing that NECTIN4 expression is necessary and sufficient for enfortumab vedotin sensitivity provided the mechanistic rationale for the ADC in urothelial cancer.\",\n      \"evidence\": \"Stable overexpression and knockdown in bladder cancer lines with drug-sensitivity and clonogenic assays\",\n      \"pmids\": [\"34108177\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative expression threshold for response not defined\", \"Resistance mechanisms beyond expression loss untested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Knockdown in cutaneous SCC linked NECTIN4 to ERK signaling and cyclin D1-dependent proliferation alongside its adhesion role.\",\n      \"evidence\": \"siRNA knockdown, attachment/migration assays, ERK and cyclin D1 Western blots, proliferation assay in A431 cells\",\n      \"pmids\": [\"33808400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct coupling of NECTIN4 to ERK not shown\", \"Single cell line\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"NECTIN4 was associated with hypoxia-driven lymphangiogenesis and lymphatic metastasis via CXCR4/CXCL12-LYVE-1 modulation in breast cancer.\",\n      \"evidence\": \"siRNA knockdown of Nectin-4 and VEGF-C, LYVE-1 density, tube formation, migration, and pathway Western blots\",\n      \"pmids\": [\"33945869\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway ordering not directly validated\", \"Single lab, limited mechanistic depth\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Biophysical mapping quantified the TIGIT-nectin-4 interaction and located its interface, refining the immune-checkpoint ligand model.\",\n      \"evidence\": \"Surface plasmon resonance and structure-guided mutagenesis of TIGIT\",\n      \"pmids\": [\"37542773\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full co-crystal structure\", \"Weaker affinity than TIGIT-nectin-2; functional significance of the differential not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linking NECTIN4 to Src-family-kinase/PI3K/Rac1-mediated senescence-associated cell-size enlargement and survival expanded its signaling role beyond proliferation and adhesion.\",\n      \"evidence\": \"Bidirectional overexpression/knockdown in a DNA-damage senescence model, single-cell live imaging, and Src/PI3K/Rac1 inhibitors\",\n      \"pmids\": [\"38062106\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking cell size to survival not fully resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NECTIN4 adhesion and clustering are physically coupled to its diverse intracellular signaling outputs (integrin \\u03b24/Src, PI3K/AKT, Rac1, WNT) and a unifying structural basis for its adhesive, viral-receptor, and HER2 co-receptor interfaces remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model integrating the V/C2 domain functions\", \"Direct biochemical link from receptor engagement to PI3K/Rac1 not established\", \"In vivo relevance of cleaved fragment functions unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 2, 16]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [3, 4, 14]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [15, 21]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [5, 12]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 12, 17]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [\"nectin-afadin adherens junction complex\"],\n    \"partners\": [\"AFDN\", \"PVRL1\", \"ITGB4\", \"ERBB2\", \"TIGIT\", \"KPNA2\", \"ADAM17\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":9,"faith_pct":88.88888888888889}}