{"gene":"CLCA4","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2024,"finding":"CLCA4 is a self-cleaving metalloprotease whose secreted N-terminal portion (N-CLCA4) potentiates Ca2+-dependent Cl- current (ICaCC) carried by TMEM16B (not TMEM16A) in HEK293T cells. The von Willebrand factor type A (VWA) domain in N-CLCA4 is sufficient for this potentiation, and the metal ion-dependent adhesion site (MIDAS) motif within the VWA domain is required, indicating specificity in CLCA4/TMEM16B pairing distinct from the CLCA1/TMEM16A pairing.","method":"Electrophysiology (ICaCC measurement in HEK293T cells), domain deletion constructs, MIDAS motif mutagenesis, cell-surface engagement assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro functional assay with mutagenesis (MIDAS motif) and domain truncation, multiple orthogonal methods in a single rigorous study","pmids":["38825009"],"is_preprint":false},{"year":2013,"finding":"Knockdown of CLCA4 by shRNA in immortalized mammary epithelial cells caused downregulation of epithelial marker E-cadherin and CLCA2, and upregulation of mesenchymal markers N-cadherin, vimentin, and fibronectin, demonstrating that CLCA4 is required to maintain epithelial identity and suppress EMT. Double knockdown of CLCA2 and CLCA4 enhanced the mesenchymal profile, indicating complementary but distinct roles.","method":"shRNA knockdown, transcriptional profiling, marker protein expression analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function with defined molecular phenotype (EMT marker changes), but single lab and no pathway placement beyond EMT","pmids":["24386311"],"is_preprint":false},{"year":2017,"finding":"Overexpression of CLCA4 in bladder cancer cells attenuated proliferation, migration, and invasion, while CLCA4 knockdown had the opposite effect. Mechanistically, CLCA4 suppresses the PI3K/AKT signaling pathway and its downstream molecules, and regulates EMT markers, placing CLCA4 upstream of PI3K/AKT in this cancer context.","method":"Overexpression and siRNA knockdown, cell proliferation assays, migration/invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function with defined molecular readouts (PI3K/AKT phosphorylation, EMT markers), single lab","pmids":["29190973"],"is_preprint":false},{"year":2018,"finding":"CLCA4 knockdown in hepatocellular carcinoma cells increased migration and invasion, upregulated mesenchymal EMT markers, and increased PI3K/AKT phosphorylation; CLCA4 overexpression reversed these effects. This places CLCA4 as a suppressor of EMT acting upstream of PI3K/AKT in HCC cells.","method":"siRNA knockdown, overexpression, Western blot for PI3K/AKT phosphorylation and EMT markers, migration/invasion assays","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain- and loss-of-function with molecular pathway readouts, single lab","pmids":["30312171"],"is_preprint":false},{"year":2019,"finding":"Overexpression of CLCA4 in colorectal cancer cells (SW620, LoVo) inhibited migration and invasion by suppressing EMT via PI3K/AKT signaling, with corresponding changes in EMT marker expression.","method":"Gain-of-function cell models, wound healing assay, Transwell assay, Western blot for PI3K/AKT and EMT markers","journal":"Medical science monitor : international medical journal of experimental and clinical research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single gain-of-function approach with molecular readouts, single lab, single set of methods","pmids":["31164625"],"is_preprint":false},{"year":2012,"finding":"Genetic association analysis in cystic fibrosis patients identified that CLCA4 promoter-region variants (markers rs11807298-rs6684219) are associated with the manifestation of residual Ca2+-mediated chloride secretion in colonic tissue, supporting a role for CLCA4 in signal transduction modulating chloride transport in intestinal epithelial cells.","method":"Association study with fine-mapping of 17 markers in 171 CF patients, stratified by residual chloride conductance phenotype","journal":"European journal of human genetics : EJHG","confidence":"Low","confidence_rationale":"Tier 4 / Weak — genetic association only, no direct functional experiment on the protein; pathway placement is inferred","pmids":["23073314"],"is_preprint":false},{"year":2020,"finding":"CLCA4 is a direct target of miR-19a in colorectal cancer cells: luciferase reporter assay confirmed miR-19a binds CLCA4 mRNA; miR-19a inhibition increased CLCA4 expression; knockdown of CLCA4 reversed the anti-proliferative/anti-invasive effects of miR-19a inhibition; and the miR-19a/CLCA4 axis modulates PI3K/AKT phospho-activation.","method":"Luciferase reporter assay, miRNA mimic/inhibitor transfection, CLCA4 siRNA knockdown rescue experiment, Western blot for PI3K/AKT","journal":"European journal of histochemistry : EJH","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase validation of direct miRNA-target interaction plus epistasis (knockdown rescue), single lab","pmids":["35266369"],"is_preprint":false},{"year":2020,"finding":"CLCA4 is a direct target of miR-501-5p in head and neck squamous cell carcinoma: luciferase assay confirmed the interaction; co-transfection of miR-501-5p with CLCA4 showed the miR-501-5p/CLCA4 axis regulates HNSCC cell proliferation and metastasis.","method":"Luciferase reporter assay, co-transfection, cell proliferation and invasion assays","journal":"Molecular biology reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, luciferase validation present but limited functional follow-up","pmids":["32072405"],"is_preprint":false},{"year":2021,"finding":"Overexpression of CLCA4 in esophageal carcinoma cells inhibited proliferation, migration, invasion, and EMT progression in vitro, and suppressed tumor growth in vivo in animal experiments.","method":"CCK-8 proliferation assay, Transwell migration/invasion assay, Western blot for EMT markers, xenograft tumor model","journal":"Journal of oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — gain-of-function with multiple cellular assays and in vivo model, but no pathway mechanism beyond EMT description, single lab","pmids":["34194494"],"is_preprint":false}],"current_model":"CLCA4 is a self-cleaving metalloprotease whose secreted N-terminal VWA domain potentiates TMEM16B-mediated Ca2+-activated Cl- currents via its MIDAS motif; in epithelial and cancer cell contexts, CLCA4 suppresses epithelial-to-mesenchymal transition and cell invasion by inhibiting PI3K/AKT signaling, and its expression is post-transcriptionally repressed by miRNAs (miR-19a, miR-501-5p) that target its mRNA 3'UTR."},"narrative":{"mechanistic_narrative":"CLCA4 is a self-cleaving metalloprotease that operates both as a modulator of epithelial chloride transport and as a suppressor of epithelial-to-mesenchymal transition (EMT) [PMID:38825009, PMID:24386311]. Its secreted N-terminal fragment (N-CLCA4) potentiates Ca2+-activated Cl- currents carried specifically by TMEM16B; this activity maps to the von Willebrand factor type A (VWA) domain and depends on the metal ion-dependent adhesion site (MIDAS) motif within it, defining a CLCA4/TMEM16B pairing distinct from the CLCA1/TMEM16A pairing [PMID:38825009]. In epithelial and multiple cancer contexts, CLCA4 maintains epithelial identity: its loss downregulates E-cadherin and upregulates mesenchymal markers, and reciprocal gain/loss-of-function across bladder, hepatocellular, and colorectal cancer cells shows that CLCA4 inhibits proliferation, migration, and invasion by suppressing PI3K/AKT signaling and the associated EMT program [PMID:24386311, PMID:29190973, PMID:30312171, PMID:31164625]. CLCA4 expression is post-transcriptionally repressed through direct targeting of its mRNA by miR-19a in colorectal cancer, with the miR-19a/CLCA4 axis modulating PI3K/AKT activation [PMID:35266369].","teleology":[{"year":2012,"claim":"Whether CLCA4 contributes to epithelial chloride handling was unresolved; a genetic association in cystic fibrosis patients linked CLCA4 promoter variants to residual Ca2+-mediated colonic chloride secretion, providing the first human evidence tying CLCA4 to chloride transport modulation.","evidence":"Association study with fine-mapping in 171 CF patients stratified by residual chloride conductance","pmids":["23073314"],"confidence":"Low","gaps":["Genetic association only, with no direct functional experiment on the protein","Causal mechanism linking the variant to chloride secretion not established","No molecular partner identified"]},{"year":2013,"claim":"The cellular role of CLCA4 was undefined; shRNA knockdown in mammary epithelial cells showed it is required to maintain epithelial identity and suppress EMT, establishing CLCA4 as a guardian of the epithelial state.","evidence":"shRNA knockdown with EMT marker profiling in immortalized mammary epithelial cells; double knockdown with CLCA2","pmids":["24386311"],"confidence":"Medium","gaps":["No signaling pathway placed downstream of CLCA4","Distinction between CLCA2 and CLCA4 roles not mechanistically resolved","Single lab, single cell context"]},{"year":2017,"claim":"The signaling axis through which CLCA4 suppresses invasion was unknown; reciprocal gain/loss-of-function in bladder cancer placed CLCA4 upstream of PI3K/AKT, connecting its EMT-suppressing role to a defined oncogenic pathway.","evidence":"Overexpression and siRNA knockdown with proliferation/migration/invasion assays and Western blot for PI3K/AKT phosphorylation and EMT markers","pmids":["29190973"],"confidence":"Medium","gaps":["Mechanism by which CLCA4 inhibits PI3K/AKT not defined","No direct molecular interaction demonstrated","Single cancer type, single lab"]},{"year":2018,"claim":"Whether the PI3K/AKT-suppressing role generalized beyond bladder cancer was open; hepatocellular carcinoma experiments confirmed CLCA4 suppresses EMT and PI3K/AKT phosphorylation across a second tumor context.","evidence":"siRNA knockdown and overexpression with migration/invasion assays and Western blot for PI3K/AKT and EMT markers in HCC cells","pmids":["30312171"],"confidence":"Medium","gaps":["Direct biochemical link between CLCA4 and PI3K/AKT remains unestablished","No structural or domain mapping of the suppressive activity"]},{"year":2019,"claim":"The generality of CLCA4's tumor-suppressive function was further tested in colorectal cancer, where overexpression inhibited migration and invasion via PI3K/AKT-dependent EMT suppression, reinforcing a conserved mechanism.","evidence":"Gain-of-function colorectal cancer models with wound healing, Transwell, and Western blot for PI3K/AKT and EMT markers","pmids":["31164625"],"confidence":"Medium","gaps":["Loss-of-function not paired in this study","No in vivo validation in this context","Single lab"]},{"year":2020,"claim":"How CLCA4 expression is controlled in cancer was unknown; luciferase and rescue experiments identified CLCA4 as a direct target of miR-19a (colorectal) and miR-501-5p (HNSCC), establishing post-transcriptional repression as a route to CLCA4 loss and PI3K/AKT activation in tumors.","evidence":"Luciferase reporter assays, miRNA mimic/inhibitor transfection, CLCA4 knockdown rescue, Western blot for PI3K/AKT","pmids":["35266369","32072405"],"confidence":"Medium","gaps":["miR-501-5p axis has limited functional follow-up and is Low-confidence","Whether these miRNAs regulate CLCA4 in normal epithelium not tested","Upstream control of the miRNAs themselves not addressed"]},{"year":2021,"claim":"Whether CLCA4 suppresses tumor growth in vivo was untested; esophageal carcinoma xenografts showed CLCA4 overexpression inhibits proliferation, invasion, EMT, and tumor growth, extending the in vitro tumor-suppressor role to an animal model.","evidence":"CCK-8, Transwell, Western blot for EMT markers, and xenograft tumor model in esophageal carcinoma cells","pmids":["34194494"],"confidence":"Low","gaps":["No pathway mechanism beyond EMT description in this study","Single lab, single tumor type"]},{"year":2024,"claim":"The biochemical activity of CLCA4 itself was undefined; electrophysiology with domain truncation and MIDAS mutagenesis showed CLCA4 is a self-cleaving metalloprotease whose secreted VWA-domain-bearing N-fragment potentiates TMEM16B (not TMEM16A) currents through the MIDAS motif, defining its molecular mechanism and ion-channel partner specificity.","evidence":"ICaCC electrophysiology in HEK293T cells with domain deletion constructs, MIDAS mutagenesis, and cell-surface engagement assays","pmids":["38825009"],"confidence":"High","gaps":["Link between TMEM16B potentiation and the PI3K/AKT/EMT tumor-suppressor role not established","Endogenous physiological tissue context of CLCA4/TMEM16B pairing not defined","No structural model of the N-CLCA4/TMEM16B interaction"]},{"year":null,"claim":"It remains unknown how CLCA4's metalloprotease/TMEM16B-potentiating activity mechanistically connects to its PI3K/AKT-dependent suppression of EMT, and whether the secreted N-CLCA4 fragment mediates the tumor-suppressive phenotype.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experiment links the channel-modulating activity to PI3K/AKT signaling","Direct binding partners in the EMT pathway unidentified","Whether protease activity is required for tumor suppression untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]},{"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]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,3,4]}],"complexes":[],"partners":["TMEM16B","CLCA2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14CN2","full_name":"Calcium-activated chloride channel regulator 4","aliases":["Calcium-activated chloride channel family member 4","hCLCA4","Calcium-activated chloride channel protein 2","CaCC-2","hCaCC-2","Chloride channel accessory 4"],"length_aa":919,"mass_kda":101.3,"function":"May be involved in mediating calcium-activated chloride conductance","subcellular_location":"Cell membrane; Apical cell membrane; Secreted","url":"https://www.uniprot.org/uniprotkb/Q14CN2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CLCA4","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CLCA4","total_profiled":1310},"omim":[{"mim_id":"616857","title":"CHLORIDE CHANNEL ACCESSORY 4; CLCA4","url":"https://www.omim.org/entry/616857"},{"mim_id":"604003","title":"CHLORIDE CHANNEL ACCESSORY 2; CLCA2","url":"https://www.omim.org/entry/604003"},{"mim_id":"603906","title":"CHLORIDE CHANNEL ACCESSORY 1; CLCA1","url":"https://www.omim.org/entry/603906"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Aggresome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"esophagus","ntpm":352.4},{"tissue":"intestine","ntpm":241.9}],"url":"https://www.proteinatlas.org/search/CLCA4"},"hgnc":{"alias_symbol":["CaCC2"],"prev_symbol":[]},"alphafold":{"accession":"Q14CN2","domains":[{"cath_id":"-","chopping":"26-168_276-302","consensus_level":"medium","plddt":95.0981,"start":26,"end":302},{"cath_id":"3.40.50.410","chopping":"306-474","consensus_level":"medium","plddt":94.095,"start":306,"end":474},{"cath_id":"2.60.40.10","chopping":"763-865","consensus_level":"high","plddt":90.1643,"start":763,"end":865}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CN2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CN2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CN2-F1-predicted_aligned_error_v6.png","plddt_mean":89.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CLCA4","jax_strain_url":"https://www.jax.org/strain/search?query=CLCA4"},"sequence":{"accession":"Q14CN2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14CN2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14CN2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CN2"}},"corpus_meta":[{"pmid":"24386311","id":"PMC_24386311","title":"Loss of CLCA4 promotes epithelial-to-mesenchymal transition in breast cancer cells.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24386311","citation_count":54,"is_preprint":false},{"pmid":"31164625","id":"PMC_31164625","title":"Calcium-Activated Chloride Channel A4 (CLCA4) Plays Inhibitory Roles in Invasion and Migration Through Suppressing Epithelial-Mesenchymal Transition via PI3K/AKT Signaling in Colorectal Cancer.","date":"2019","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/31164625","citation_count":35,"is_preprint":false},{"pmid":"29190973","id":"PMC_29190973","title":"CLCA4 inhibits bladder cancer cell proliferation, migration, and invasion by suppressing the PI3K/AKT pathway.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29190973","citation_count":34,"is_preprint":false},{"pmid":"30312171","id":"PMC_30312171","title":"CLCA4 inhibits cell proliferation and invasion of hepatocellular carcinoma by suppressing epithelial-mesenchymal transition via PI3K/AKT signaling.","date":"2018","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/30312171","citation_count":30,"is_preprint":false},{"pmid":"32565987","id":"PMC_32565987","title":"Downregulation of CLCA4 expression is associated with the development and progression of colorectal cancer.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/32565987","citation_count":14,"is_preprint":false},{"pmid":"32797167","id":"PMC_32797167","title":"CLCA4 and MS4A12 as the significant gene biomarkers of primary colorectal cancer.","date":"2020","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/32797167","citation_count":12,"is_preprint":false},{"pmid":"23073314","id":"PMC_23073314","title":"CLCA4 variants determine the manifestation of the cystic fibrosis basic defect in the intestine.","date":"2012","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/23073314","citation_count":11,"is_preprint":false},{"pmid":"32072405","id":"PMC_32072405","title":"MiR-501-5p acts as an energetic regulator in head and neck squamous cell carcinoma cells growth and aggressiveness via reducing CLCA4.","date":"2020","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/32072405","citation_count":9,"is_preprint":false},{"pmid":"35266369","id":"PMC_35266369","title":"<em>miR-19a</em> targeting <em>CLCA4</em> to regulate the proliferation, migration, and invasion of colorectal cancer cells.","date":"2022","source":"European journal of histochemistry : EJH","url":"https://pubmed.ncbi.nlm.nih.gov/35266369","citation_count":9,"is_preprint":false},{"pmid":"32773719","id":"PMC_32773719","title":"Frameshift Mutations and Loss of Expression of CLCA4 Gene are Frequent in Colorectal Cancers With Microsatellite Instability.","date":"2020","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/32773719","citation_count":6,"is_preprint":false},{"pmid":"34194494","id":"PMC_34194494","title":"Expression of the CLCA4 Gene in Esophageal Carcinoma and Its Impact on the Biologic Function of Esophageal Carcinoma Cells.","date":"2021","source":"Journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34194494","citation_count":5,"is_preprint":false},{"pmid":"38825009","id":"PMC_38825009","title":"Modulation of TMEM16B channel activity by the calcium-activated chloride channel regulator 4 (CLCA4) in human cells.","date":"2024","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38825009","citation_count":3,"is_preprint":false},{"pmid":"30887952","id":"PMC_30887952","title":"Chloride Channel Accessory 4 (CLCA4) Gene Polymorphisms and Non-Obstructive Azoospermia: A Case-Control Study.","date":"2019","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/30887952","citation_count":2,"is_preprint":false},{"pmid":"30847028","id":"PMC_30847028","title":"Correction: CLCA4 inhibits bladder cancer cell proliferation, migration, and invasion by suppressing the PI3K/AKT pathway.","date":"2019","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/30847028","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.28.25323104","title":"Intragenic deletions from whole genome sequencing of 1054 suicide deaths","date":"2025-03-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.28.25323104","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8958,"output_tokens":2314,"usd":0.030792,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9350,"output_tokens":3283,"usd":0.064412,"stage2_stop_reason":"end_turn"},"total_usd":0.095204,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2024,\n      \"finding\": \"CLCA4 is a self-cleaving metalloprotease whose secreted N-terminal portion (N-CLCA4) potentiates Ca2+-dependent Cl- current (ICaCC) carried by TMEM16B (not TMEM16A) in HEK293T cells. The von Willebrand factor type A (VWA) domain in N-CLCA4 is sufficient for this potentiation, and the metal ion-dependent adhesion site (MIDAS) motif within the VWA domain is required, indicating specificity in CLCA4/TMEM16B pairing distinct from the CLCA1/TMEM16A pairing.\",\n      \"method\": \"Electrophysiology (ICaCC measurement in HEK293T cells), domain deletion constructs, MIDAS motif mutagenesis, cell-surface engagement assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro functional assay with mutagenesis (MIDAS motif) and domain truncation, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"38825009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Knockdown of CLCA4 by shRNA in immortalized mammary epithelial cells caused downregulation of epithelial marker E-cadherin and CLCA2, and upregulation of mesenchymal markers N-cadherin, vimentin, and fibronectin, demonstrating that CLCA4 is required to maintain epithelial identity and suppress EMT. Double knockdown of CLCA2 and CLCA4 enhanced the mesenchymal profile, indicating complementary but distinct roles.\",\n      \"method\": \"shRNA knockdown, transcriptional profiling, marker protein expression analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function with defined molecular phenotype (EMT marker changes), but single lab and no pathway placement beyond EMT\",\n      \"pmids\": [\"24386311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Overexpression of CLCA4 in bladder cancer cells attenuated proliferation, migration, and invasion, while CLCA4 knockdown had the opposite effect. Mechanistically, CLCA4 suppresses the PI3K/AKT signaling pathway and its downstream molecules, and regulates EMT markers, placing CLCA4 upstream of PI3K/AKT in this cancer context.\",\n      \"method\": \"Overexpression and siRNA knockdown, cell proliferation assays, migration/invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function with defined molecular readouts (PI3K/AKT phosphorylation, EMT markers), single lab\",\n      \"pmids\": [\"29190973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CLCA4 knockdown in hepatocellular carcinoma cells increased migration and invasion, upregulated mesenchymal EMT markers, and increased PI3K/AKT phosphorylation; CLCA4 overexpression reversed these effects. This places CLCA4 as a suppressor of EMT acting upstream of PI3K/AKT in HCC cells.\",\n      \"method\": \"siRNA knockdown, overexpression, Western blot for PI3K/AKT phosphorylation and EMT markers, migration/invasion assays\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain- and loss-of-function with molecular pathway readouts, single lab\",\n      \"pmids\": [\"30312171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Overexpression of CLCA4 in colorectal cancer cells (SW620, LoVo) inhibited migration and invasion by suppressing EMT via PI3K/AKT signaling, with corresponding changes in EMT marker expression.\",\n      \"method\": \"Gain-of-function cell models, wound healing assay, Transwell assay, Western blot for PI3K/AKT and EMT markers\",\n      \"journal\": \"Medical science monitor : international medical journal of experimental and clinical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single gain-of-function approach with molecular readouts, single lab, single set of methods\",\n      \"pmids\": [\"31164625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Genetic association analysis in cystic fibrosis patients identified that CLCA4 promoter-region variants (markers rs11807298-rs6684219) are associated with the manifestation of residual Ca2+-mediated chloride secretion in colonic tissue, supporting a role for CLCA4 in signal transduction modulating chloride transport in intestinal epithelial cells.\",\n      \"method\": \"Association study with fine-mapping of 17 markers in 171 CF patients, stratified by residual chloride conductance phenotype\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — genetic association only, no direct functional experiment on the protein; pathway placement is inferred\",\n      \"pmids\": [\"23073314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CLCA4 is a direct target of miR-19a in colorectal cancer cells: luciferase reporter assay confirmed miR-19a binds CLCA4 mRNA; miR-19a inhibition increased CLCA4 expression; knockdown of CLCA4 reversed the anti-proliferative/anti-invasive effects of miR-19a inhibition; and the miR-19a/CLCA4 axis modulates PI3K/AKT phospho-activation.\",\n      \"method\": \"Luciferase reporter assay, miRNA mimic/inhibitor transfection, CLCA4 siRNA knockdown rescue experiment, Western blot for PI3K/AKT\",\n      \"journal\": \"European journal of histochemistry : EJH\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase validation of direct miRNA-target interaction plus epistasis (knockdown rescue), single lab\",\n      \"pmids\": [\"35266369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CLCA4 is a direct target of miR-501-5p in head and neck squamous cell carcinoma: luciferase assay confirmed the interaction; co-transfection of miR-501-5p with CLCA4 showed the miR-501-5p/CLCA4 axis regulates HNSCC cell proliferation and metastasis.\",\n      \"method\": \"Luciferase reporter assay, co-transfection, cell proliferation and invasion assays\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, luciferase validation present but limited functional follow-up\",\n      \"pmids\": [\"32072405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Overexpression of CLCA4 in esophageal carcinoma cells inhibited proliferation, migration, invasion, and EMT progression in vitro, and suppressed tumor growth in vivo in animal experiments.\",\n      \"method\": \"CCK-8 proliferation assay, Transwell migration/invasion assay, Western blot for EMT markers, xenograft tumor model\",\n      \"journal\": \"Journal of oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — gain-of-function with multiple cellular assays and in vivo model, but no pathway mechanism beyond EMT description, single lab\",\n      \"pmids\": [\"34194494\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CLCA4 is a self-cleaving metalloprotease whose secreted N-terminal VWA domain potentiates TMEM16B-mediated Ca2+-activated Cl- currents via its MIDAS motif; in epithelial and cancer cell contexts, CLCA4 suppresses epithelial-to-mesenchymal transition and cell invasion by inhibiting PI3K/AKT signaling, and its expression is post-transcriptionally repressed by miRNAs (miR-19a, miR-501-5p) that target its mRNA 3'UTR.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CLCA4 is a self-cleaving metalloprotease that operates both as a modulator of epithelial chloride transport and as a suppressor of epithelial-to-mesenchymal transition (EMT) [#0, #1]. Its secreted N-terminal fragment (N-CLCA4) potentiates Ca2+-activated Cl- currents carried specifically by TMEM16B; this activity maps to the von Willebrand factor type A (VWA) domain and depends on the metal ion-dependent adhesion site (MIDAS) motif within it, defining a CLCA4/TMEM16B pairing distinct from the CLCA1/TMEM16A pairing [#0]. In epithelial and multiple cancer contexts, CLCA4 maintains epithelial identity: its loss downregulates E-cadherin and upregulates mesenchymal markers, and reciprocal gain/loss-of-function across bladder, hepatocellular, and colorectal cancer cells shows that CLCA4 inhibits proliferation, migration, and invasion by suppressing PI3K/AKT signaling and the associated EMT program [#1, #2, #3, #4]. CLCA4 expression is post-transcriptionally repressed through direct targeting of its mRNA by miR-19a in colorectal cancer, with the miR-19a/CLCA4 axis modulating PI3K/AKT activation [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Whether CLCA4 contributes to epithelial chloride handling was unresolved; a genetic association in cystic fibrosis patients linked CLCA4 promoter variants to residual Ca2+-mediated colonic chloride secretion, providing the first human evidence tying CLCA4 to chloride transport modulation.\",\n      \"evidence\": \"Association study with fine-mapping in 171 CF patients stratified by residual chloride conductance\",\n      \"pmids\": [\"23073314\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Genetic association only, with no direct functional experiment on the protein\",\n        \"Causal mechanism linking the variant to chloride secretion not established\",\n        \"No molecular partner identified\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The cellular role of CLCA4 was undefined; shRNA knockdown in mammary epithelial cells showed it is required to maintain epithelial identity and suppress EMT, establishing CLCA4 as a guardian of the epithelial state.\",\n      \"evidence\": \"shRNA knockdown with EMT marker profiling in immortalized mammary epithelial cells; double knockdown with CLCA2\",\n      \"pmids\": [\"24386311\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No signaling pathway placed downstream of CLCA4\",\n        \"Distinction between CLCA2 and CLCA4 roles not mechanistically resolved\",\n        \"Single lab, single cell context\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The signaling axis through which CLCA4 suppresses invasion was unknown; reciprocal gain/loss-of-function in bladder cancer placed CLCA4 upstream of PI3K/AKT, connecting its EMT-suppressing role to a defined oncogenic pathway.\",\n      \"evidence\": \"Overexpression and siRNA knockdown with proliferation/migration/invasion assays and Western blot for PI3K/AKT phosphorylation and EMT markers\",\n      \"pmids\": [\"29190973\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which CLCA4 inhibits PI3K/AKT not defined\",\n        \"No direct molecular interaction demonstrated\",\n        \"Single cancer type, single lab\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Whether the PI3K/AKT-suppressing role generalized beyond bladder cancer was open; hepatocellular carcinoma experiments confirmed CLCA4 suppresses EMT and PI3K/AKT phosphorylation across a second tumor context.\",\n      \"evidence\": \"siRNA knockdown and overexpression with migration/invasion assays and Western blot for PI3K/AKT and EMT markers in HCC cells\",\n      \"pmids\": [\"30312171\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical link between CLCA4 and PI3K/AKT remains unestablished\",\n        \"No structural or domain mapping of the suppressive activity\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The generality of CLCA4's tumor-suppressive function was further tested in colorectal cancer, where overexpression inhibited migration and invasion via PI3K/AKT-dependent EMT suppression, reinforcing a conserved mechanism.\",\n      \"evidence\": \"Gain-of-function colorectal cancer models with wound healing, Transwell, and Western blot for PI3K/AKT and EMT markers\",\n      \"pmids\": [\"31164625\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Loss-of-function not paired in this study\",\n        \"No in vivo validation in this context\",\n        \"Single lab\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"How CLCA4 expression is controlled in cancer was unknown; luciferase and rescue experiments identified CLCA4 as a direct target of miR-19a (colorectal) and miR-501-5p (HNSCC), establishing post-transcriptional repression as a route to CLCA4 loss and PI3K/AKT activation in tumors.\",\n      \"evidence\": \"Luciferase reporter assays, miRNA mimic/inhibitor transfection, CLCA4 knockdown rescue, Western blot for PI3K/AKT\",\n      \"pmids\": [\"35266369\", \"32072405\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"miR-501-5p axis has limited functional follow-up and is Low-confidence\",\n        \"Whether these miRNAs regulate CLCA4 in normal epithelium not tested\",\n        \"Upstream control of the miRNAs themselves not addressed\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether CLCA4 suppresses tumor growth in vivo was untested; esophageal carcinoma xenografts showed CLCA4 overexpression inhibits proliferation, invasion, EMT, and tumor growth, extending the in vitro tumor-suppressor role to an animal model.\",\n      \"evidence\": \"CCK-8, Transwell, Western blot for EMT markers, and xenograft tumor model in esophageal carcinoma cells\",\n      \"pmids\": [\"34194494\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No pathway mechanism beyond EMT description in this study\",\n        \"Single lab, single tumor type\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The biochemical activity of CLCA4 itself was undefined; electrophysiology with domain truncation and MIDAS mutagenesis showed CLCA4 is a self-cleaving metalloprotease whose secreted VWA-domain-bearing N-fragment potentiates TMEM16B (not TMEM16A) currents through the MIDAS motif, defining its molecular mechanism and ion-channel partner specificity.\",\n      \"evidence\": \"ICaCC electrophysiology in HEK293T cells with domain deletion constructs, MIDAS mutagenesis, and cell-surface engagement assays\",\n      \"pmids\": [\"38825009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Link between TMEM16B potentiation and the PI3K/AKT/EMT tumor-suppressor role not established\",\n        \"Endogenous physiological tissue context of CLCA4/TMEM16B pairing not defined\",\n        \"No structural model of the N-CLCA4/TMEM16B interaction\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how CLCA4's metalloprotease/TMEM16B-potentiating activity mechanistically connects to its PI3K/AKT-dependent suppression of EMT, and whether the secreted N-CLCA4 fragment mediates the tumor-suppressive phenotype.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No experiment links the channel-modulating activity to PI3K/AKT signaling\",\n        \"Direct binding partners in the EMT pathway unidentified\",\n        \"Whether protease activity is required for tumor suppression untested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TMEM16B\",\n      \"CLCA2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}