{"gene":"CCDC68","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2017,"finding":"CCDC68 is a novel subdistal appendage (SDA) component of the centriole in human cells. It is a CEP170-interacting protein that competes with CCDC120 in recruiting CEP170 to SDAs. CCDC68 is required for centrosome microtubule anchoring in interphase cells.","method":"Co-immunoprecipitation, immunofluorescence localization, RNAi knockdown with microtubule anchoring readout, competition assays between CCDC68 and CCDC120 for CEP170 recruitment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, direct localization experiments, RNAi loss-of-function with defined cellular phenotype (microtubule anchoring), multiple orthogonal methods in single focused study","pmids":["28422092"],"is_preprint":false},{"year":2024,"finding":"CCDC68 is an outer kinetochore protein that preferentially localizes to unattached kinetochores. It interacts with the SAC factor CDC20 to inhibit CDC20 autoubiquitination and MCC (mitotic checkpoint complex) disassembly, thereby restraining APC/C activation and maintaining a robust spindle assembly checkpoint (SAC) to ensure chromosomal stability.","method":"Co-immunoprecipitation (CCDC68–CDC20 interaction), kinetochore localization by immunofluorescence, loss-of-function assays measuring SAC activation and chromosome alignment, ubiquitination assays","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, direct localization to kinetochores, loss-of-function with defined mitotic checkpoint phenotype, ubiquitination assay; multiple orthogonal methods in single focused study","pmids":["39018254"],"is_preprint":false},{"year":2014,"finding":"Overexpression of full-length CCDC68 in PDAC cell lines decreased proliferation and tumorigenicity in vivo, while knockdown increased tumor growth, establishing a tumor-suppressive function. A SNP variant (rs1344011) causes exon skipping producing an unstable isoform (CCDC68Δ69-114) that lacks this tumor-suppressive activity.","method":"Overexpression in PANC-1 and Hs.766T PDAC cells (proliferation assay, xenograft in SCID mice), shRNA knockdown in MIAPaca-2 cells, SNP genotyping, protein isoform characterization","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo xenograft + in vitro KD/OE with defined proliferation phenotype, isoform functional comparison; single lab, two orthogonal approaches","pmids":["25381825"],"is_preprint":false},{"year":2021,"finding":"CCDC68 promotes CDK4 stabilization in colorectal cancer cells by inhibiting ITCH-mediated CDK4 ubiquitin-dependent degradation. Ectopic CCDC68 expression upregulates ITCH (E3 ubiquitin ligase) and downregulates CDK4 protein levels, causing G0/G1 cell cycle arrest and suppressing tumor growth.","method":"Ectopic CCDC68 overexpression and knockdown in CRC cell lines, Western blot for CDK4 and ITCH, cell cycle analysis, xenograft tumor assay","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss- and gain-of-function with defined cell cycle and molecular phenotype, single lab, pathway placement via CDK4/ITCH axis but without direct biochemical reconstitution of the interaction","pmids":["33968776"],"is_preprint":false},{"year":2021,"finding":"IL-6 stimulation upregulates CCDC68 expression in endometrial carcinoma cells. CCDC68 knockdown inhibits IL-6-associated cancer cell proliferation, migration, and invasion, placing CCDC68 downstream of IL-6 signaling as a pro-tumorigenic factor in this context.","method":"qPCR and Western blot for CCDC68 after IL-6 stimulation, stable shRNA knockdown in Ishikawa and RL-95 cells, proliferation/migration/invasion assays","journal":"Journal of interferon & cytokine research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — stable KD with defined cellular phenotype and upstream signaling context (IL-6 pathway), single lab, multiple functional readouts but no direct biochemical mechanism","pmids":["33471616"],"is_preprint":false},{"year":2020,"finding":"CCDC68 knockdown in NSCLC cell lines (A549 and H1299) decreased cell proliferation and increased apoptotic rates, indicating a pro-proliferative/anti-apoptotic role for CCDC68 in lung cancer cells.","method":"shRNA knockdown of CCDC68, cell proliferation assay, viability assay, apoptosis assay in lung cancer cell lines","journal":"Oncology letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single KD approach, phenotypic readout without pathway placement or biochemical mechanism","pmids":["33133256"],"is_preprint":false}],"current_model":"CCDC68 is a multifunctional coiled-coil domain protein with at least two distinct mechanistic roles: (1) as a subdistal appendage component of centrioles, it interacts with CEP170 and competes with CCDC120 to regulate hierarchical SDA assembly and microtubule anchoring at the centrosome; and (2) as an outer kinetochore protein at unattached kinetochores, it binds CDC20 to inhibit its autoubiquitination and stabilize the mitotic checkpoint complex (MCC), thereby restraining APC/C and maintaining spindle assembly checkpoint integrity. In cancer contexts, CCDC68 acts as a tumor suppressor in PDAC and colorectal cancer (promoting ITCH-mediated CDK4 degradation and G1 arrest), while paradoxically functioning as a pro-tumorigenic factor downstream of IL-6 in endometrial carcinoma."},"narrative":{"mechanistic_narrative":"CCDC68 is a coiled-coil domain protein that operates at two distinct microtubule-organizing structures to safeguard genomic and centrosomal integrity, and is recurrently implicated as a context-dependent regulator of tumor cell proliferation [PMID:28422092, PMID:39018254, PMID:25381825]. At the centriole it functions as a subdistal appendage component, binding CEP170 and competing with CCDC120 for CEP170 recruitment to govern appendage assembly and microtubule anchoring at the centrosome in interphase cells [PMID:28422092]. During mitosis it localizes preferentially to unattached kinetochores, where it binds CDC20 to block CDC20 autoubiquitination and prevent disassembly of the mitotic checkpoint complex, thereby restraining APC/C activation and sustaining a robust spindle assembly checkpoint to ensure correct chromosome alignment [PMID:39018254]. In cancer, CCDC68 acts as a tumor suppressor in pancreatic ductal adenocarcinoma, where a SNP-driven exon-skipping isoform abolishes its growth-inhibitory activity [PMID:25381825], and in colorectal cancer it enforces G0/G1 arrest by upregulating the E3 ligase ITCH to promote ubiquitin-dependent CDK4 degradation [PMID:33968776]. In endometrial carcinoma it instead acts downstream of IL-6 signaling as a pro-tumorigenic factor driving proliferation, migration, and invasion [PMID:33471616].","teleology":[{"year":2014,"claim":"Established the first functional role for CCDC68 by showing it restrains tumor cell growth, and that a common SNP generates an inactive isoform — linking the gene to PDAC biology.","evidence":"Overexpression/knockdown in PDAC cell lines with xenografts and SNP isoform characterization","pmids":["25381825"],"confidence":"Medium","gaps":["No molecular mechanism for the tumor-suppressive activity identified at this stage","Subcellular localization and direct partners not defined","Single-lab study"]},{"year":2017,"claim":"Defined a concrete molecular function by placing CCDC68 at centriolar subdistal appendages, where it competes with CCDC120 to recruit CEP170 and enables microtubule anchoring.","evidence":"Reciprocal Co-IP, immunofluorescence localization, RNAi loss-of-function with microtubule anchoring readout, and competition assays in human cells","pmids":["28422092"],"confidence":"High","gaps":["Structural basis of CEP170 binding and CCDC120 competition not resolved","Relationship between this centrosomal role and the tumor phenotypes not established"]},{"year":2020,"claim":"Reported a context-opposite, pro-proliferative role in lung cancer, indicating CCDC68 function is cell-type dependent.","evidence":"shRNA knockdown with proliferation, viability and apoptosis assays in NSCLC lines","pmids":["33133256"],"confidence":"Low","gaps":["Single knockdown approach without rescue or pathway placement","No biochemical mechanism for the anti-apoptotic effect","Discrepancy with tumor-suppressive role in PDAC unexplained"]},{"year":2021,"claim":"Provided mechanism for tumor suppression in colorectal cancer by linking CCDC68 to ITCH-mediated CDK4 degradation and G1 arrest.","evidence":"Gain/loss-of-function in CRC lines, Western blot for CDK4 and ITCH, cell cycle analysis and xenografts","pmids":["33968776"],"confidence":"Medium","gaps":["No direct biochemical reconstitution of the CCDC68–ITCH–CDK4 axis","How CCDC68 upregulates ITCH is unknown"]},{"year":2021,"claim":"Showed CCDC68 can act downstream of IL-6 as a pro-tumorigenic factor in endometrial carcinoma, reinforcing context-dependent dual function.","evidence":"IL-6 stimulation with qPCR/Western blot and stable shRNA knockdown with proliferation/migration/invasion assays in endometrial lines","pmids":["33471616"],"confidence":"Medium","gaps":["Direct biochemical mechanism downstream of IL-6 not defined","Link to the centriolar or kinetochore functions unexplored"]},{"year":2024,"claim":"Revealed a mitotic checkpoint function by showing CCDC68 stabilizes the MCC at unattached kinetochores through CDC20 binding, connecting it to chromosomal stability.","evidence":"Reciprocal Co-IP, kinetochore immunofluorescence, loss-of-function SAC and chromosome alignment assays, and ubiquitination assays","pmids":["39018254"],"confidence":"High","gaps":["Structural basis of CDC20 binding and inhibition not resolved","Whether checkpoint dysfunction underlies the cancer phenotypes not tested"]},{"year":null,"claim":"How CCDC68's centriolar appendage role, kinetochore checkpoint role, and opposing context-dependent cancer functions are mechanistically unified remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No model reconciling tumor-suppressive (PDAC, CRC) versus pro-tumorigenic (endometrial, NSCLC) roles","No structural data for any CCDC68 interaction","Regulation of CCDC68 expression and isoform switching across tissues unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1]}],"complexes":["subdistal appendage","mitotic checkpoint complex (MCC)","kinetochore"],"partners":["CEP170","CCDC120","CDC20","ITCH"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H2F9","full_name":"Coiled-coil domain-containing protein 68","aliases":["Cutaneous T-cell lymphoma-associated antigen se57-1","CTCL-associated antigen se57-1"],"length_aa":335,"mass_kda":38.9,"function":"Centriolar protein required for centriole subdistal appendage assembly and microtubule anchoring in interphase cells (PubMed:28422092). Together with CCDC120, cooperate with subdistal appendage components ODF2, NIN and CEP170 for hierarchical subdistal appendage assembly (PubMed:28422092)","subcellular_location":"Cytoplasm, cytoskeleton, microtubule organizing center, centrosome, centriole","url":"https://www.uniprot.org/uniprotkb/Q9H2F9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CCDC68","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CCDC68","total_profiled":1310},"omim":[{"mim_id":"616909","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 68; CCDC68","url":"https://www.omim.org/entry/616909"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"intestine","ntpm":23.3},{"tissue":"placenta","ntpm":30.5}],"url":"https://www.proteinatlas.org/search/CCDC68"},"hgnc":{"alias_symbol":["SE57-1"],"prev_symbol":[]},"alphafold":{"accession":"Q9H2F9","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2F9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2F9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2F9-F1-predicted_aligned_error_v6.png","plddt_mean":80.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CCDC68","jax_strain_url":"https://www.jax.org/strain/search?query=CCDC68"},"sequence":{"accession":"Q9H2F9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H2F9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H2F9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2F9"}},"corpus_meta":[{"pmid":"19359472","id":"PMC_19359472","title":"Association of survival and disease progression with chromosomal instability: a genomic exploration of colorectal cancer.","date":"2009","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/19359472","citation_count":321,"is_preprint":false},{"pmid":"21791550","id":"PMC_21791550","title":"Common variants at VRK2 and TCF4 conferring risk of schizophrenia.","date":"2011","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21791550","citation_count":165,"is_preprint":false},{"pmid":"32172300","id":"PMC_32172300","title":"A genomics approach to females with infertility and recurrent pregnancy loss.","date":"2020","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32172300","citation_count":68,"is_preprint":false},{"pmid":"28422092","id":"PMC_28422092","title":"Hierarchical assembly of centriole subdistal appendages via centrosome binding proteins CCDC120 and CCDC68.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28422092","citation_count":67,"is_preprint":false},{"pmid":"24160291","id":"PMC_24160291","title":"The impact of the genome-wide supported variant in the cyclin M2 gene on gray matter morphology in schizophrenia.","date":"2013","source":"Behavioral and brain functions : BBF","url":"https://pubmed.ncbi.nlm.nih.gov/24160291","citation_count":36,"is_preprint":false},{"pmid":"27481827","id":"PMC_27481827","title":"Testing the Validity of Taxonic Schizotypy Using Genetic and Environmental Risk Variables.","date":"2017","source":"Schizophrenia bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/27481827","citation_count":29,"is_preprint":false},{"pmid":"25381825","id":"PMC_25381825","title":"Coiled-coil domain containing 68 (CCDC68) demonstrates a tumor-suppressive role in pancreatic ductal adenocarcinoma.","date":"2014","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/25381825","citation_count":26,"is_preprint":false},{"pmid":"15142679","id":"PMC_15142679","title":"Tissue expression and sero-reactivity of tumor-specific antigens in colorectal cancer.","date":"2004","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/15142679","citation_count":25,"is_preprint":false},{"pmid":"33968776","id":"PMC_33968776","title":"Coiled-Coil Domain-Containing 68 Downregulation Promotes Colorectal Cancer Cell Growth by Inhibiting ITCH-Mediated CDK4 Degradation.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33968776","citation_count":19,"is_preprint":false},{"pmid":"33471616","id":"PMC_33471616","title":"CCDC68 Upregulation by IL-6 Promotes Endometrial Carcinoma Progression.","date":"2021","source":"Journal of interferon & cytokine research : the official journal of the International Society for Interferon and Cytokine Research","url":"https://pubmed.ncbi.nlm.nih.gov/33471616","citation_count":13,"is_preprint":false},{"pmid":"33192958","id":"PMC_33192958","title":"DNA Methylation Patterns of Chronic Explosive Breaching in U.S. Military Warfighters.","date":"2020","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/33192958","citation_count":8,"is_preprint":false},{"pmid":"33133256","id":"PMC_33133256","title":"Coiled-coil domain-containing 68 promotes non-small cell lung cancer cell proliferation in vitro.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/33133256","citation_count":7,"is_preprint":false},{"pmid":"23439384","id":"PMC_23439384","title":"Expression and differential response to haloperidol treatment of Cyclon/CCDC86 mRNA in schizophrenia patients.","date":"2013","source":"Neurochemistry international","url":"https://pubmed.ncbi.nlm.nih.gov/23439384","citation_count":5,"is_preprint":false},{"pmid":"39018254","id":"PMC_39018254","title":"CCDC68 Maintains Mitotic Checkpoint Activation by Promoting CDC20 Integration into the MCC.","date":"2024","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/39018254","citation_count":4,"is_preprint":false},{"pmid":"40462294","id":"PMC_40462294","title":"Spatial Transcriptomics Shows a Distinctive Tumour Microenvironment in the Invasive Versus Premalignant Portion of Early Cutaneous Squamous Cell Carcinoma.","date":"2025","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/40462294","citation_count":2,"is_preprint":false},{"pmid":"41474729","id":"PMC_41474729","title":"Exploring the molecular link between obstructive sleep apnea and interstitial cystitis/bladder pain syndrome: A bioinformatics and machine learning study.","date":"2025","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/41474729","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9663,"output_tokens":1769,"usd":0.027762,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8639,"output_tokens":2457,"usd":0.05231,"stage2_stop_reason":"end_turn"},"total_usd":0.080072,"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\": 2017,\n      \"finding\": \"CCDC68 is a novel subdistal appendage (SDA) component of the centriole in human cells. It is a CEP170-interacting protein that competes with CCDC120 in recruiting CEP170 to SDAs. CCDC68 is required for centrosome microtubule anchoring in interphase cells.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence localization, RNAi knockdown with microtubule anchoring readout, competition assays between CCDC68 and CCDC120 for CEP170 recruitment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, direct localization experiments, RNAi loss-of-function with defined cellular phenotype (microtubule anchoring), multiple orthogonal methods in single focused study\",\n      \"pmids\": [\"28422092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CCDC68 is an outer kinetochore protein that preferentially localizes to unattached kinetochores. It interacts with the SAC factor CDC20 to inhibit CDC20 autoubiquitination and MCC (mitotic checkpoint complex) disassembly, thereby restraining APC/C activation and maintaining a robust spindle assembly checkpoint (SAC) to ensure chromosomal stability.\",\n      \"method\": \"Co-immunoprecipitation (CCDC68–CDC20 interaction), kinetochore localization by immunofluorescence, loss-of-function assays measuring SAC activation and chromosome alignment, ubiquitination assays\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, direct localization to kinetochores, loss-of-function with defined mitotic checkpoint phenotype, ubiquitination assay; multiple orthogonal methods in single focused study\",\n      \"pmids\": [\"39018254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Overexpression of full-length CCDC68 in PDAC cell lines decreased proliferation and tumorigenicity in vivo, while knockdown increased tumor growth, establishing a tumor-suppressive function. A SNP variant (rs1344011) causes exon skipping producing an unstable isoform (CCDC68Δ69-114) that lacks this tumor-suppressive activity.\",\n      \"method\": \"Overexpression in PANC-1 and Hs.766T PDAC cells (proliferation assay, xenograft in SCID mice), shRNA knockdown in MIAPaca-2 cells, SNP genotyping, protein isoform characterization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo xenograft + in vitro KD/OE with defined proliferation phenotype, isoform functional comparison; single lab, two orthogonal approaches\",\n      \"pmids\": [\"25381825\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CCDC68 promotes CDK4 stabilization in colorectal cancer cells by inhibiting ITCH-mediated CDK4 ubiquitin-dependent degradation. Ectopic CCDC68 expression upregulates ITCH (E3 ubiquitin ligase) and downregulates CDK4 protein levels, causing G0/G1 cell cycle arrest and suppressing tumor growth.\",\n      \"method\": \"Ectopic CCDC68 overexpression and knockdown in CRC cell lines, Western blot for CDK4 and ITCH, cell cycle analysis, xenograft tumor assay\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss- and gain-of-function with defined cell cycle and molecular phenotype, single lab, pathway placement via CDK4/ITCH axis but without direct biochemical reconstitution of the interaction\",\n      \"pmids\": [\"33968776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IL-6 stimulation upregulates CCDC68 expression in endometrial carcinoma cells. CCDC68 knockdown inhibits IL-6-associated cancer cell proliferation, migration, and invasion, placing CCDC68 downstream of IL-6 signaling as a pro-tumorigenic factor in this context.\",\n      \"method\": \"qPCR and Western blot for CCDC68 after IL-6 stimulation, stable shRNA knockdown in Ishikawa and RL-95 cells, proliferation/migration/invasion assays\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — stable KD with defined cellular phenotype and upstream signaling context (IL-6 pathway), single lab, multiple functional readouts but no direct biochemical mechanism\",\n      \"pmids\": [\"33471616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CCDC68 knockdown in NSCLC cell lines (A549 and H1299) decreased cell proliferation and increased apoptotic rates, indicating a pro-proliferative/anti-apoptotic role for CCDC68 in lung cancer cells.\",\n      \"method\": \"shRNA knockdown of CCDC68, cell proliferation assay, viability assay, apoptosis assay in lung cancer cell lines\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single KD approach, phenotypic readout without pathway placement or biochemical mechanism\",\n      \"pmids\": [\"33133256\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CCDC68 is a multifunctional coiled-coil domain protein with at least two distinct mechanistic roles: (1) as a subdistal appendage component of centrioles, it interacts with CEP170 and competes with CCDC120 to regulate hierarchical SDA assembly and microtubule anchoring at the centrosome; and (2) as an outer kinetochore protein at unattached kinetochores, it binds CDC20 to inhibit its autoubiquitination and stabilize the mitotic checkpoint complex (MCC), thereby restraining APC/C and maintaining spindle assembly checkpoint integrity. In cancer contexts, CCDC68 acts as a tumor suppressor in PDAC and colorectal cancer (promoting ITCH-mediated CDK4 degradation and G1 arrest), while paradoxically functioning as a pro-tumorigenic factor downstream of IL-6 in endometrial carcinoma.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CCDC68 is a coiled-coil domain protein that operates at two distinct microtubule-organizing structures to safeguard genomic and centrosomal integrity, and is recurrently implicated as a context-dependent regulator of tumor cell proliferation [#0, #1, #2]. At the centriole it functions as a subdistal appendage component, binding CEP170 and competing with CCDC120 for CEP170 recruitment to govern appendage assembly and microtubule anchoring at the centrosome in interphase cells [#0]. During mitosis it localizes preferentially to unattached kinetochores, where it binds CDC20 to block CDC20 autoubiquitination and prevent disassembly of the mitotic checkpoint complex, thereby restraining APC/C activation and sustaining a robust spindle assembly checkpoint to ensure correct chromosome alignment [#1]. In cancer, CCDC68 acts as a tumor suppressor in pancreatic ductal adenocarcinoma, where a SNP-driven exon-skipping isoform abolishes its growth-inhibitory activity [#2], and in colorectal cancer it enforces G0/G1 arrest by upregulating the E3 ligase ITCH to promote ubiquitin-dependent CDK4 degradation [#3]. In endometrial carcinoma it instead acts downstream of IL-6 signaling as a pro-tumorigenic factor driving proliferation, migration, and invasion [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established the first functional role for CCDC68 by showing it restrains tumor cell growth, and that a common SNP generates an inactive isoform — linking the gene to PDAC biology.\",\n      \"evidence\": \"Overexpression/knockdown in PDAC cell lines with xenografts and SNP isoform characterization\",\n      \"pmids\": [\"25381825\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No molecular mechanism for the tumor-suppressive activity identified at this stage\",\n        \"Subcellular localization and direct partners not defined\",\n        \"Single-lab study\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined a concrete molecular function by placing CCDC68 at centriolar subdistal appendages, where it competes with CCDC120 to recruit CEP170 and enables microtubule anchoring.\",\n      \"evidence\": \"Reciprocal Co-IP, immunofluorescence localization, RNAi loss-of-function with microtubule anchoring readout, and competition assays in human cells\",\n      \"pmids\": [\"28422092\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of CEP170 binding and CCDC120 competition not resolved\",\n        \"Relationship between this centrosomal role and the tumor phenotypes not established\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Reported a context-opposite, pro-proliferative role in lung cancer, indicating CCDC68 function is cell-type dependent.\",\n      \"evidence\": \"shRNA knockdown with proliferation, viability and apoptosis assays in NSCLC lines\",\n      \"pmids\": [\"33133256\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single knockdown approach without rescue or pathway placement\",\n        \"No biochemical mechanism for the anti-apoptotic effect\",\n        \"Discrepancy with tumor-suppressive role in PDAC unexplained\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided mechanism for tumor suppression in colorectal cancer by linking CCDC68 to ITCH-mediated CDK4 degradation and G1 arrest.\",\n      \"evidence\": \"Gain/loss-of-function in CRC lines, Western blot for CDK4 and ITCH, cell cycle analysis and xenografts\",\n      \"pmids\": [\"33968776\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No direct biochemical reconstitution of the CCDC68–ITCH–CDK4 axis\",\n        \"How CCDC68 upregulates ITCH is unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed CCDC68 can act downstream of IL-6 as a pro-tumorigenic factor in endometrial carcinoma, reinforcing context-dependent dual function.\",\n      \"evidence\": \"IL-6 stimulation with qPCR/Western blot and stable shRNA knockdown with proliferation/migration/invasion assays in endometrial lines\",\n      \"pmids\": [\"33471616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical mechanism downstream of IL-6 not defined\",\n        \"Link to the centriolar or kinetochore functions unexplored\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a mitotic checkpoint function by showing CCDC68 stabilizes the MCC at unattached kinetochores through CDC20 binding, connecting it to chromosomal stability.\",\n      \"evidence\": \"Reciprocal Co-IP, kinetochore immunofluorescence, loss-of-function SAC and chromosome alignment assays, and ubiquitination assays\",\n      \"pmids\": [\"39018254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of CDC20 binding and inhibition not resolved\",\n        \"Whether checkpoint dysfunction underlies the cancer phenotypes not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CCDC68's centriolar appendage role, kinetochore checkpoint role, and opposing context-dependent cancer functions are mechanistically unified remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No model reconciling tumor-suppressive (PDAC, CRC) versus pro-tumorigenic (endometrial, NSCLC) roles\",\n        \"No structural data for any CCDC68 interaction\",\n        \"Regulation of CCDC68 expression and isoform switching across tissues unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [\n      \"subdistal appendage\",\n      \"mitotic checkpoint complex (MCC)\",\n      \"kinetochore\"\n    ],\n    \"partners\": [\n      \"CEP170\",\n      \"CCDC120\",\n      \"CDC20\",\n      \"ITCH\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}