{"gene":"CCDC6","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":1992,"finding":"CCDC6 (D10S170) is fused to the RET tyrosine kinase domain by a paracentric inversion of chromosome 10q [inv(10)(q11.2q21)], generating the RET/PTC1 oncogene in papillary thyroid carcinomas; cytogenetic and molecular analysis of tumor samples established that the chromosomal inversion breakpoints coincide with RET (10q11.2) and D10S170 (10q21) loci.","method":"Cytogenetic analysis combined with Southern blotting and FISH on papillary thyroid carcinoma samples","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (cytogenetics, Southern blot, molecular cloning) across multiple tumor samples, independently replicated in subsequent studies","pmids":["1542652"],"is_preprint":false},{"year":1994,"finding":"CCDC6 (H4/D10S170) encodes a 585-amino acid protein with no transmembrane domain, extensive alpha-helical coiled-coil regions homologous to cytoskeletal proteins (tropomyosin, vimentin, keratin, myosin heavy chain tail), and a putative SH3-binding site at the C-terminus, suggesting it is a cytoskeletal-associated protein.","method":"cDNA cloning and sequencing from human normal thyroid library; sequence analysis and structural prediction","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — sequence-based structural inference replicated across multiple subsequent studies; no direct biochemical validation of cytoskeletal interaction in this paper","pmids":["8058316"],"is_preprint":false},{"year":1995,"finding":"The N-terminal region of CCDC6 (H4/D10S170) contains a coiled-coil (leucine zipper-like) oligomerization domain; in vitro assays with recombinant proteins demonstrated that this region mediates oligomerization, and the H4 promoter drives ubiquitous expression of PTC1 in diverse human tissues including thyroid.","method":"In vitro oligomerization assay with recombinant proteins; luciferase promoter assay; primer extension mapping of transcriptional start sites","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution of oligomerization with recombinant proteins, functional promoter assay; single lab","pmids":["7753554"],"is_preprint":false},{"year":1997,"finding":"CCDC6 leucine zipper-mediated dimerization is essential for the transforming activity of the PTC1 oncoprotein: the PTC1 oncoprotein forms a dimer in vivo via the H4 leucine zipper, leucine zipper-dependent dimerization is required for tyrosine hyperphosphorylation of PTC1 and for its ability to transform NIH3T3 cells, and a dominant-negative PTC1 mutant introduced into PTC1-transformed cells suppresses transformation by forming inactive heterodimers.","method":"Co-immunoprecipitation in vivo; dominant-negative transfection into NIH3T3 transformants; focus formation assay; immunokinase assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, functional mutagenesis of leucine zipper, dominant-negative rescue experiment, multiple orthogonal readouts in single study","pmids":["9083029"],"is_preprint":false},{"year":2000,"finding":"CCDC6 (H4/D10S170) is fused in-frame to the platelet-derived growth factor receptor beta (PDGFβR) in a t(5;10)(q33;q21.2) translocation in BCR-ABL-negative chronic myeloid leukemia; the H4-PDGFβR chimeric mRNA was detected by RT-PCR and 5'-RACE, establishing CCDC6 as a recurrent fusion partner in myeloid malignancies beyond thyroid cancer.","method":"Southern blotting, FISH, 5'-RACE PCR, RT-PCR, DNA sequencing","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal molecular methods (Southern, FISH, 5'-RACE, RT-PCR, sequencing) independently confirmed fusion","pmids":["10910073"],"is_preprint":false},{"year":2001,"finding":"The H4/CCDC6-PDGFβR fusion protein requires the CCDC6 leucine zipper domain (amino acids 55–93) as well as additional H4 sequences (aa 101–386) for efficient induction of factor-independent growth; retroviral transduction of H4/PDGFβR (but not a kinase-inactive mutant) conferred factor-independent growth to Ba/F3 cells and caused T-cell lymphoblastic lymphoma in a murine bone marrow transplantation model.","method":"Retroviral transduction of Ba/F3 cells; murine bone marrow transplantation assay; mutational analysis of leucine zipper and PDGFβR domains; factor-independent growth assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro and in vivo transformation assays, systematic mutagenesis of CCDC6 dimerization domains, kinase-dead control, multiple orthogonal methods","pmids":["11389034"],"is_preprint":false},{"year":2004,"finding":"CCDC6 (H4/D10S170) protein is a ubiquitously expressed 55 kDa protein found in both the nucleus and cytosol; it is phosphorylated following serum stimulation in an ERK1/2-dependent manner, and this phosphorylation correlates with relocation from nucleus to cytosol. Overexpression of full-length CCDC6 induces apoptosis of thyroid follicular cells, whereas the C-terminally truncated mutant H4(1-101) (the portion retained in RET/PTC1) acts as a dominant negative on both the pro-apoptotic function and nuclear localization of CCDC6; substitution of serine 244 with alanine abrogates the apoptotic function.","method":"Subcellular fractionation and immunofluorescence; serum stimulation with ERK inhibitor treatment; overexpression and dominant-negative transfection assays in thyroid cells; site-directed mutagenesis (S244A); conditional expression system","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (fractionation, imaging, kinase inhibitor, mutagenesis, conditional expression), single lab but comprehensive mechanistic dissection","pmids":["14712216"],"is_preprint":false},{"year":2004,"finding":"RET/PTC1 associates with hsp90 and its co-chaperone p50cdc37; proteomic analysis identified these as novel RET/PTC1-interacting proteins, and hsp90 inhibition with 17-AAG reduces RET/PTC1 protein levels.","method":"Proteomic analysis (Co-immunoprecipitation followed by mass spectrometry); Western blot of 17-AAG-treated cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomic Co-IP identification with functional consequence (protein degradation upon inhibition), single lab","pmids":["15302866"],"is_preprint":false},{"year":2007,"finding":"CCDC6 (H4/D10S170) undergoes ATM-mediated phosphorylation at Thr434 in response to DNA damage (etoposide or ionizing radiation); this phosphorylation stabilizes CCDC6 in the nucleus. In ATM-deficient cells, CCDC6 is excluded from the nucleus and is not phosphorylated after IR. The T434A mutant fails to induce apoptosis and protects cells from genotoxic stress; silencing of CCDC6 after IR increases cell survival, permits DNA synthesis, and allows mitotic entry, demonstrating CCDC6's role in the ATM-dependent DNA damage response.","method":"Co-immunoprecipitation; immunofluorescence in ATM-deficient and proficient cells; site-directed mutagenesis (T434A); clonogenic assay after siRNA knockdown; BrdU incorporation assay; histone H3 phosphorylation assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal approach using ATM-deficient patient cells, site-directed mutagenesis, multiple functional assays (clonogenic, BrdU, mitosis marker), single lab but multiple orthogonal methods","pmids":["17420723"],"is_preprint":false},{"year":2010,"finding":"CCDC6 interacts with CREB1 and represses CREB1 transcriptional activity by recruiting histone deacetylase 1 (HDAC1) and protein phosphatase 1 (PP1) to the CRE site of CREB1 target genes; loss of CCDC6 function (as occurs in RET/PTC1 rearrangement) leads to increased CREB1 phosphorylation and elevated expression of CREB1 target genes AREG and cyclin A in PTCs.","method":"Co-immunoprecipitation (CCDC6-CREB1 interaction); chromatin immunoprecipitation showing HDAC1 and PP1 recruitment to CRE sites; reporter assays for CREB1 transcriptional activity; Western blot of CREB1 phosphorylation; RT-PCR of target gene expression in PTC samples","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP demonstrating complex recruitment to chromatin, functional reporter assays, validated in primary tumor samples; multiple orthogonal methods","pmids":["20498639"],"is_preprint":false},{"year":2012,"finding":"CCDC6 loss accelerates dephosphorylation of γH2AX (pH2AX S139) following genotoxic stress, resulting in defective G2 arrest and premature mitotic entry. CCDC6 physically interacts with the catalytic subunit of protein phosphatase 4 (PP4c), the conserved pH2AX phosphatase, and CCDC6 depletion increases PP4c enzymatic activity; these data suggest CCDC6 negatively modulates PP4c to sustain the DNA damage checkpoint.","method":"High-throughput proteomic screening predicting CCDC6-PP4c interaction; Co-immunoprecipitation confirming CCDC6-PP4c binding; PP4c enzymatic activity assay in CCDC6-depleted cells; γH2AX S139 phosphorylation assay by flow cytometry/Western; cell cycle analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP validated interaction, enzymatic activity assay, cell cycle phenotype; single lab, two orthogonal methods confirming PP4c modulation","pmids":["22655027"],"is_preprint":false},{"year":2012,"finding":"Loss of CCDC6 impairs the intra-S-phase checkpoint: CCDC6-depleted cells show shortened S-phase, fail to accumulate in S-phase upon etoposide treatment, accumulate DNA damage (elevated pH2AX Ser139), downregulate 14-3-3σ, and fail to sequester CDC25C phosphatase to the cytoplasm upon genotoxic stress — indicating CCDC6 is required for proper S-phase checkpoint control.","method":"Lentiviral shRNA knockdown of CCDC6 in multiple cell lines; cell cycle analysis by flow cytometry; Western blot for 14-3-3σ, CDC25C, pH2AX; immunofluorescence for CDC25C localization","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean shRNA KD with defined molecular phenotypes; multiple cell lines; single lab, several orthogonal readouts","pmids":["22363533"],"is_preprint":false},{"year":2012,"finding":"FBXW7 E3 ubiquitin ligase interacts with CCDC6 and targets it for ubiquitin-mediated proteasomal degradation; ATM-mediated phosphorylation of CCDC6 at Thr434 during DNA damage response prevents the FBXW7-CCDC6 interaction and thereby stabilizes CCDC6, linking DNA damage signaling to CCDC6 protein stability.","method":"Co-immunoprecipitation of FBXW7 with CCDC6; ubiquitination assay; proteasome inhibitor treatment; site-directed mutagenesis (T434A/T434E) blocking/mimicking ATM phosphorylation; Western blot","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, in-cell ubiquitination assay, phosphomimetic mutagenesis, and functional rescue; multiple orthogonal methods establishing E3 ligase–substrate relationship","pmids":["23108047"],"is_preprint":false},{"year":2012,"finding":"CCDC6 contains three sumoylation sites (K74, K266, K424) conserved in vertebrates; SUMO2 modification at these sites sequesters CCDC6 in the cytosol and reduces its ability to repress CREB1 transcriptional activity. Mutation of all three sumoylation sites abolishes this cytosolic sequestration and restores CCDC6 repressive function on CREB1. In thyroid cells, SUMO2-mediated modification is induced by Forskolin/cAMP signaling.","method":"Site-directed mutagenesis of sumoylation sites (K74R, K266R, K424R); immunofluorescence for subcellular localization of SUMO2-modified CCDC6; CREB1 reporter assay; Forskolin treatment of thyroid cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis of all three sites, functional reporter assay, imaging of localization; single lab","pmids":["23145146"],"is_preprint":false},{"year":2015,"finding":"CCDC6 protein levels oscillate during the cell cycle, peaking at G2 and decreasing in mitosis; mitotic kinases promote CCDC6 degradation via phospho-degron motifs that recruit the FBXW7 E3 ubiquitin ligase, while the deubiquitinase USP7 counteracts this to stabilize CCDC6. Both FBXW7 and USP7 affect CCDC6 protein levels and, consequently, cell drug response in NSCLC cells.","method":"Cell cycle synchronization followed by Western blot and phosphorylation assays; Co-immunoprecipitation of CCDC6 with FBXW7 and USP7; USP7 inhibitor treatment; cycloheximide chase assay","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell cycle synchronization, Co-IP, enzymatic inhibition, cycloheximide chase — multiple orthogonal methods establishing cell-cycle-dependent turnover mechanism","pmids":["25885523"],"is_preprint":false},{"year":2015,"finding":"Mice carrying a Ccdc6 exon-2 deletion knock-in (which specifically impairs CCDC6-mediated CREB1 repression) develop thyroid hyperplasia with enhanced CREB1 activity and increased expression of CREB1-regulated target genes, demonstrating that CCDC6 repression of CREB1 is functionally required to prevent thyroid hyperplasia in vivo.","method":"Knock-in mouse model with Ccdc6 exon-2 deletion; immunohistochemistry of thyroid; luciferase reporter assay comparing wild-type vs. mutant Ccdc6 repression of CREB1; RT-PCR of CREB1 target genes","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knock-in model with defined molecular mechanism (CREB1 repression), corroborated by reporter assay; strong because genetic model validates the CCDC6-CREB1 pathway in vivo","pmids":["25970781"],"is_preprint":false},{"year":2016,"finding":"USP7 deubiquitinase is responsible for fine-tuning CCDC6 protein stability; inhibition of USP7 with P5091 accelerates CCDC6 degradation in cycloheximide chase assays and sensitizes lung neuroendocrine cancer cells to PARP inhibitors, establishing a USP7→CCDC6→PARP-inhibitor sensitivity axis.","method":"Cycloheximide chase assay with USP7 inhibitor P5091 in L-NET cells; cell viability assays with PARP inhibitor alone and in combination with cisplatinum; immunostaining correlation of CCDC6 and USP7 in TMA","journal":"Lung cancer (Amsterdam, Netherlands)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cycloheximide chase with pharmacological inhibitor, functional cell viability assay; single lab, two methods","pmids":["27372520"],"is_preprint":false},{"year":2016,"finding":"The FGFR2-CCDC6 fusion protein in intrahepatic cholangiocarcinoma acts as a constitutively active oncogenic kinase; in a patient-derived xenograft model endogenously expressing FGFR2-CCDC6, FGFR inhibitors (ponatinib, dovitinib, BGJ398) modulate FGFR signaling, inhibit cell proliferation and induce apoptosis, with BGJ398 showing superior potency.","method":"Patient-derived xenograft (PDX) model; Western blot for FGFR signaling (pFGFR, downstream targets); cell proliferation assay; apoptosis assay; comparison of three FGFR inhibitors in vivo","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo PDX model with signaling readouts; single study, confirms FGFR2-CCDC6 as druggable kinase fusion","pmids":["27216979"],"is_preprint":false},{"year":2018,"finding":"miR-146b-5p directly targets CCDC6 mRNA, reducing CCDC6 protein levels and thereby promoting PTC cell proliferation, migration, invasion, and cell cycle progression; overexpression of CCDC6 reverses these effects both in vitro and in a subcutaneous mouse model, identifying CCDC6 as a functional tumor suppressor target of miR-146b-5p in papillary thyroid cancer.","method":"Luciferase reporter assay with CCDC6 3'UTR confirming direct miR-146b-5p targeting; gain- and loss-of-function studies (miR-146b-5p overexpression and CCDC6 overexpression/knockdown) with cell proliferation, migration, invasion, and cell cycle assays; subcutaneous mouse tumor model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct target validation by luciferase assay, functional rescue by CCDC6 overexpression, in vivo model; single lab","pmids":["30503553"],"is_preprint":false},{"year":2019,"finding":"CCDC6 physically interacts with BAP1 (BRCA1-associated protein-1) in malignant pleural mesothelioma cells; depletion of CCDC6 impairs homologous recombination-mediated DSB repair and sensitizes MPM cells to PARP inhibitors, and combined loss of CCDC6 and expression of mutant BAP1 (Δ221-238) further enhances HR-repair defects and PARP inhibitor sensitivity.","method":"Co-immunoprecipitation of CCDC6 with BAP1 in MPM cells; HR reporter assay; cell viability assay with PARP inhibitors; co-transfection of CCDC6 siRNA and BAP1 mutant construct","journal":"Lung cancer (Amsterdam, Netherlands)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional HR assay and drug sensitivity; single lab","pmids":["31447003"],"is_preprint":false},{"year":2024,"finding":"CCDC6-RET fusion protein undergoes liquid-liquid phase separation (LLPS) dependent on both its kinase domain and the CCDC6 fusion partner; this LLPS promotes autophosphorylation and enhances kinase activity of the RET fusion. Within the resulting condensate, a ternary signal niche comprising CCDC6-RET, adaptor GRB2, and effector SHC1 is assembled, amplifying Ras/MAPK signaling efficiency in a tyrosine kinase-dependent manner.","method":"In vitro and cellular LLPS assays; autophosphorylation kinase assays; Co-immunoprecipitation of the CCDC6-RET/GRB2/SHC1 ternary complex; domain deletion mutants to define LLPS requirements; biochemical signaling assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstitution of LLPS, kinase activity assay, Co-IP of ternary complex, systematic mutagenesis to define requirements; multiple orthogonal methods in a single rigorous study","pmids":["38805286"],"is_preprint":false},{"year":2014,"finding":"CCDC6-deficient NSCLC cells show defective homologous recombination (reduced Rad51 foci), impaired DNA damage response, resistance to cisplatin, and sensitization to PARP1/2 inhibitor olaparib with a synthetic lethal effect; combining olaparib and cisplatin in CCDC6-deficient cells produces combination index <1 (synergy).","method":"Characterization of NSCLC cell lines by Western blot for CCDC6; Rad51 foci assay; HR reporter assay; clonogenic/viability assays with cisplatin, olaparib, and combination; combination index calculation","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — HR reporter assay, Rad51 foci, drug combination assays; multiple readouts of DNA repair defect; single lab","pmids":["25302833"],"is_preprint":false},{"year":2013,"finding":"CCDC6 loss in germ cell-derived GC1 cells attenuates apoptotic signaling (decreased cytochrome c oxidation, reduced Bad, PARP-1, and caspase-3) and impairs γH2AX activation upon H₂O₂ oxidative damage, while reducing reactive oxygen species release and protecting cell viability; CCDC6 expression is present in Sertoli cells and spermatogonial cells of the testis but is lost in testicular germ cell tumors.","method":"shRNA silencing of CCDC6 in GC1 cells; H₂O₂ treatment; Western blot for apoptosis markers (cytochrome c, Bad, PARP-1, caspase-3); γH2AX immunofluorescence; ROS assay; immunohistochemistry of mouse and human testis sections","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA KD with multiple apoptosis and DNA damage readouts; single lab","pmids":["24059746"],"is_preprint":false},{"year":2022,"finding":"In CCDC6-RET-rearranged thyroid cancer, adaptive resistance to RET inhibitors is mediated by rapid reactivation of ERK signaling via FGFR pathway activation within hours of drug exposure; combined FGFR and RET inhibition prevents adaptive ERK reactivation, reduces cell viability, and decreases tumor growth in cellular and animal models.","method":"Drug screening on CCDC6-RET patient-derived models; proteomic and biochemical profiling (phosphoproteomics, Western blot); combined RET+FGFR inhibitor treatment in vitro and in vivo xenograft","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient-derived model, phosphoproteomic profiling, in vivo validation; single lab, multiple methods","pmids":["35510953"],"is_preprint":false}],"current_model":"CCDC6 is a ubiquitously expressed, predominantly nuclear phosphoprotein that functions as a tumor suppressor by: (1) repressing CREB1 transcriptional activity through recruitment of HDAC1 and PP1 to CRE-containing promoters; (2) sustaining the ATM-dependent DNA damage response via ATM-mediated phosphorylation at Thr434 (which stabilizes nuclear CCDC6 and inhibits PP4c-mediated γH2AX dephosphorylation to enforce G2/S checkpoints); (3) promoting apoptosis in a serine-244-dependent manner; and (4) undergoing cell-cycle-regulated proteolysis controlled by FBXW7-mediated ubiquitination (opposed by USP7 deubiquitination) and SUMO2 modification (which redistributes CCDC6 to the cytoplasm and reduces CREB1 repression); when CCDC6 is fused to RET kinase (RET/PTC1), the retained N-terminal coiled-coil domain drives constitutive leucine-zipper-mediated dimerization and LLPS-enhanced autophosphorylation that assembles a GRB2-SHC1-containing Ras/MAPK signal niche, while loss of CCDC6 function impairs homologous recombination and confers synthetic lethality with PARP inhibitors."},"narrative":{"mechanistic_narrative":"CCDC6 is a ubiquitously expressed, predominantly nuclear coiled-coil phosphoprotein that functions as a tumor suppressor coordinating transcriptional repression, the DNA damage response, and apoptosis [PMID:14712216, PMID:20498639, PMID:17420723]. It directly binds CREB1 and represses CREB1-dependent transcription by recruiting HDAC1 and PP1 to CRE-containing promoters; loss of this function elevates CREB1 phosphorylation and target genes such as AREG and cyclin A, and a knock-in mouse lacking CCDC6 CREB1-repressor activity develops thyroid hyperplasia, establishing the pathway as physiologically protective [PMID:20498639, PMID:25970781]. In the DNA damage response, CCDC6 is phosphorylated by ATM at Thr434, which stabilizes the nuclear protein and is required to enforce S-phase and G2 checkpoints; mechanistically CCDC6 restrains the γH2AX phosphatase PP4c to sustain damage signaling, and its depletion accelerates γH2AX dephosphorylation, shortens S-phase, and permits premature mitotic entry [PMID:17420723, PMID:22655027, PMID:22363533]. CCDC6 also supports homologous-recombination repair—its loss reduces Rad51 foci and confers synthetic lethality with PARP inhibitors—and physically interacts with BAP1 in this context [PMID:25302833, PMID:31447003]. CCDC6 abundance is cell-cycle-regulated, peaking at G2 and degraded in mitosis through phospho-degron–directed FBXW7 ubiquitination opposed by USP7 deubiquitination, while SUMO2 modification redistributes CCDC6 to the cytoplasm and relieves CREB1 repression [PMID:25885523, PMID:23108047, PMID:23145146]. CCDC6 is recurrently disrupted by chromosomal rearrangements that fuse its N-terminal coiled-coil to receptor tyrosine kinases—RET (RET/PTC1) in papillary thyroid carcinoma, PDGFβR in chronic myeloid leukemia, and FGFR2 in cholangiocarcinoma—where the leucine-zipper drives constitutive dimerization required for kinase activation and transformation [PMID:1542652, PMID:10910073, PMID:27216979, PMID:9083029]. For the CCDC6-RET oncoprotein, the fusion-driven liquid-liquid phase separation enhances autophosphorylation and assembles a GRB2-SHC1 signaling niche that amplifies Ras/MAPK output [PMID:38805286].","teleology":[{"year":1992,"claim":"Established CCDC6 as a recurrent cancer gene by identifying its fusion to the RET kinase, defining the RET/PTC1 oncogene of papillary thyroid carcinoma.","evidence":"Cytogenetics, Southern blot, and FISH on papillary thyroid carcinoma samples","pmids":["1542652"],"confidence":"High","gaps":["Did not define the normal cellular function of CCDC6","Mechanism of oncogenic activation by fusion unaddressed"]},{"year":1994,"claim":"Cloning revealed CCDC6 as a 585-residue coiled-coil protein, providing the structural basis for later dimerization and fusion studies.","evidence":"cDNA cloning/sequencing and structural prediction from human thyroid library","pmids":["8058316"],"confidence":"Medium","gaps":["Cytoskeletal association inferred from sequence, not biochemically validated","No functional assay"]},{"year":1997,"claim":"Showed that the CCDC6 leucine zipper is the molecular driver of fusion oncogenicity, mediating dimerization needed for RET/PTC1 kinase activation and transformation.","evidence":"In vivo Co-IP, leucine-zipper mutagenesis, dominant-negative rescue, and focus formation in NIH3T3 cells","pmids":["9083029"],"confidence":"High","gaps":["Did not address wild-type CCDC6 function","Biophysical basis of dimerization-driven activation unresolved until LLPS work"]},{"year":2000,"claim":"Extended CCDC6's fusion repertoire beyond thyroid cancer by identifying the CCDC6-PDGFβR fusion in BCR-ABL-negative CML, with the leucine zipper required for transformation.","evidence":"Southern blot, FISH, 5'-RACE, RT-PCR in CML; Ba/F3 transduction and murine bone marrow transplant","pmids":["10910073","11389034"],"confidence":"High","gaps":["Did not test whether wild-type CCDC6 loss contributes to leukemogenesis"]},{"year":2004,"claim":"Defined wild-type CCDC6 as a ubiquitous nuclear/cytosolic phosphoprotein that is pro-apoptotic, with ERK-driven phosphorylation controlling nuclear-cytosolic shuttling and serine-244 required for apoptosis.","evidence":"Subcellular fractionation, immunofluorescence, ERK inhibitor, S244A mutagenesis, conditional expression in thyroid cells","pmids":["14712216"],"confidence":"High","gaps":["Apoptotic effector pathway downstream of S244 not defined","Direct kinase acting on S244 not identified"]},{"year":2007,"claim":"Connected CCDC6 to the ATM-dependent DNA damage response, showing ATM phosphorylates Thr434 to stabilize nuclear CCDC6 and enforce cell-cycle arrest after damage.","evidence":"Co-IP, immunofluorescence in ATM-deficient/proficient cells, T434A mutagenesis, clonogenic and BrdU assays","pmids":["17420723"],"confidence":"High","gaps":["Downstream effectors of nuclear CCDC6 in checkpoint enforcement not yet identified","Direct ATM-CCDC6 phosphorylation not shown in vitro"]},{"year":2010,"claim":"Identified the transcriptional repressor mechanism: CCDC6 binds CREB1 and recruits HDAC1 and PP1 to CRE sites, explaining how CCDC6 loss drives CREB1 target overexpression in thyroid cancer.","evidence":"Co-IP, ChIP for HDAC1/PP1 at CRE sites, CREB1 reporter assays, target gene RT-PCR in PTC samples","pmids":["20498639"],"confidence":"High","gaps":["Stoichiometry/order of HDAC1 and PP1 recruitment unresolved","Genome-wide CREB1 targets controlled by CCDC6 not mapped"]},{"year":2012,"claim":"Resolved how CCDC6 sustains the damage checkpoint mechanistically—by restraining the γH2AX phosphatase PP4c and supporting intra-S-phase checkpoint components—linking its loss to genomic instability.","evidence":"Proteomic screen, Co-IP of CCDC6-PP4c, PP4c activity and γH2AX assays, shRNA knockdown with cell-cycle/CDC25C analyses","pmids":["22655027","22363533"],"confidence":"Medium","gaps":["Whether CCDC6 inhibits PP4c directly or via an adaptor unresolved","Structural basis of PP4c modulation unknown"]},{"year":2012,"claim":"Established the degradation control of CCDC6 by FBXW7 and its coupling to damage signaling, showing ATM phosphorylation at Thr434 blocks FBXW7 binding to stabilize CCDC6, plus SUMO2-driven cytoplasmic sequestration that relieves CREB1 repression.","evidence":"Co-IP, in-cell ubiquitination, phosphomimetic mutagenesis (FBXW7); sumoylation-site mutagenesis with localization imaging and reporter assays","pmids":["23108047","23145146"],"confidence":"Medium","gaps":["SUMO E3 ligase for CCDC6 not identified","Crosstalk between SUMOylation and FBXW7 turnover not tested"]},{"year":2014,"claim":"Demonstrated CCDC6's role in homologous recombination, showing its loss reduces Rad51 foci, impairs HR, and confers synthetic lethality with PARP inhibitors, defining a therapeutic vulnerability.","evidence":"Rad51 foci and HR reporter assays, clonogenic/viability assays with cisplatin and olaparib, combination index in NSCLC cells","pmids":["25302833"],"confidence":"Medium","gaps":["Direct role of CCDC6 protein at HR sites not biochemically defined","Mechanism linking CCDC6 loss to reduced Rad51 loading unknown"]},{"year":2015,"claim":"Provided in vivo genetic proof that CCDC6-mediated CREB1 repression is tumor-suppressive, and refined cell-cycle-coupled turnover via FBXW7-USP7 antagonism affecting drug response.","evidence":"Ccdc6 exon-2 deletion knock-in mouse with thyroid IHC and reporter assays; cell-cycle synchronization, Co-IP, USP7 inhibitor and cycloheximide chase","pmids":["25970781","25885523"],"confidence":"High","gaps":["Mitotic kinases generating the phospho-degron not fully enumerated","Whether CREB1 repression and checkpoint roles are genetically separable in vivo untested"]},{"year":2016,"claim":"Extended the turnover axis therapeutically, showing USP7 fine-tunes CCDC6 stability and its inhibition sensitizes neuroendocrine lung cancer to PARP inhibitors.","evidence":"Cycloheximide chase with USP7 inhibitor P5091, viability assays, CCDC6/USP7 TMA correlation in L-NET cells","pmids":["27372520"],"confidence":"Medium","gaps":["USP7 may target other substrates contributing to sensitivity","Direct USP7-CCDC6 catalytic relationship not structurally defined"]},{"year":2019,"claim":"Linked CCDC6 to BAP1 in HR repair, showing physical interaction and additive HR defects and PARP-inhibitor sensitivity in mesothelioma.","evidence":"Co-IP of CCDC6-BAP1, HR reporter, viability assays, co-transfection with mutant BAP1 in MPM cells","pmids":["31447003"],"confidence":"Medium","gaps":["Functional consequence of CCDC6-BAP1 binding at chromatin not defined","Single Co-IP context; reciprocal validation limited"]},{"year":2024,"claim":"Revealed the biophysical mechanism of CCDC6-RET fusion oncogenicity: LLPS driven by the CCDC6 partner enhances autophosphorylation and assembles a GRB2-SHC1 signaling niche to amplify Ras/MAPK signaling.","evidence":"In vitro/cellular LLPS assays, autophosphorylation kinase assays, Co-IP of the ternary complex, domain-deletion mutagenesis","pmids":["38805286"],"confidence":"High","gaps":["Whether wild-type CCDC6 undergoes physiological LLPS untested","Therapeutic targetability of the condensate not established"]},{"year":null,"claim":"How CCDC6's distinct functions—CREB1 repression, PP4c restraint, HR support, and apoptosis—are mechanistically integrated and differentially deployed across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of CCDC6 in any of its complexes","Direct biochemical role of CCDC6 at HR/repair sites undefined","Tissue-specific determinants of which CCDC6 function dominates unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[9,15]},{"term_id":"GO:0098772","term_label":"molecular function regulator 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oncogene in papillary thyroid carcinoma by siRNA-squalene nanoparticles with and without fusogenic companion GALA-cholesterol.","date":"2014","source":"Thyroid : official journal of the American Thyroid Association","url":"https://pubmed.ncbi.nlm.nih.gov/23885719","citation_count":26,"is_preprint":false},{"pmid":"9067436","id":"PMC_9067436","title":"A novel multicolor hybridization scheme applied to localization of a transcribed sequence (D10S170/H4) and deletion mapping in the thyroid cancer cell line TPC-1.","date":"1996","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9067436","citation_count":25,"is_preprint":false},{"pmid":"8934550","id":"PMC_8934550","title":"Development of mammary and cutaneous gland tumors in transgenic mice carrying the RET/PTC1 oncogene.","date":"1996","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/8934550","citation_count":25,"is_preprint":false},{"pmid":"18660545","id":"PMC_18660545","title":"PARP-1 cooperates with Ptc1 to suppress medulloblastoma and basal cell carcinoma.","date":"2008","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/18660545","citation_count":24,"is_preprint":false},{"pmid":"29455670","id":"PMC_29455670","title":"The rationale for druggability of CCDC6-tyrosine kinase fusions in lung cancer.","date":"2018","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/29455670","citation_count":23,"is_preprint":false},{"pmid":"15876154","id":"PMC_15876154","title":"Low prevalence of RET rearrangements (RET/PTC1, RET/PTC2, RET/PTC3, and ELKS-RET) in sporadic papillary thyroid carcinomas in Taiwan Chinese.","date":"2005","source":"Thyroid : official journal of the American Thyroid Association","url":"https://pubmed.ncbi.nlm.nih.gov/15876154","citation_count":23,"is_preprint":false},{"pmid":"15925443","id":"PMC_15925443","title":"Ptc1 heterozygous knockout mice as a model of multi-organ tumorigenesis.","date":"2005","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/15925443","citation_count":22,"is_preprint":false},{"pmid":"25970781","id":"PMC_25970781","title":"Ccdc6 knock-in mice develop thyroid hyperplasia associated to an enhanced CREB1 activity.","date":"2015","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/25970781","citation_count":22,"is_preprint":false},{"pmid":"24059746","id":"PMC_24059746","title":"Critical role of CCDC6 in the neoplastic growth of testicular germ cell tumors.","date":"2013","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/24059746","citation_count":22,"is_preprint":false},{"pmid":"26960768","id":"PMC_26960768","title":"miRNA profiling, detection of BRAF V600E mutation and RET-PTC1 translocation in patients from Novosibirsk oblast (Russia) with different types of thyroid tumors.","date":"2016","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26960768","citation_count":22,"is_preprint":false},{"pmid":"9121114","id":"PMC_9121114","title":"Thyroid-stimulating hormone promotes growth of thyroid carcinomas in transgenic mice with targeted expression of the ret/PTC1 oncogene.","date":"1997","source":"Laboratory investigation; a journal of technical methods and pathology","url":"https://pubmed.ncbi.nlm.nih.gov/9121114","citation_count":22,"is_preprint":false},{"pmid":"9510121","id":"PMC_9510121","title":"The ret/PTC1 rearrangement is a common feature of Chernobyl-associated papillary thyroid carcinomas from Belarus.","date":"1998","source":"Thyroid : official journal of the American Thyroid Association","url":"https://pubmed.ncbi.nlm.nih.gov/9510121","citation_count":21,"is_preprint":false},{"pmid":"17709622","id":"PMC_17709622","title":"Differential responses of human papillary thyroid cancer cell lines carrying the RET/PTC1 rearrangement or a BRAF mutation to MEK1/2 inhibitors.","date":"2007","source":"Archives of otolaryngology--head & neck surgery","url":"https://pubmed.ncbi.nlm.nih.gov/17709622","citation_count":19,"is_preprint":false},{"pmid":"22641469","id":"PMC_22641469","title":"Upregulation of Shh and Ptc1 in hyperoxia‑induced acute lung injury in neonatal rats.","date":"2012","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/22641469","citation_count":18,"is_preprint":false},{"pmid":"22363533","id":"PMC_22363533","title":"Loss of CCDC6 affects cell cycle through impaired intra-S-phase checkpoint control.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22363533","citation_count":17,"is_preprint":false},{"pmid":"23145146","id":"PMC_23145146","title":"Identification of sumoylation sites in CCDC6, the first identified RET partner gene in papillary thyroid carcinoma, uncovers a mode of regulating CCDC6 function on CREB1 transcriptional activity.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23145146","citation_count":17,"is_preprint":false},{"pmid":"34552818","id":"PMC_34552818","title":"Circular RNA circDNA2 upregulates CCDC6 expression to promote the progression of gastric cancer via miR-149-5p suppression.","date":"2021","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/34552818","citation_count":16,"is_preprint":false},{"pmid":"35510953","id":"PMC_35510953","title":"Inhibition of FGF receptor blocks adaptive resistance to RET inhibition in CCDC6-RET-rearranged thyroid cancer.","date":"2022","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35510953","citation_count":16,"is_preprint":false},{"pmid":"31447003","id":"PMC_31447003","title":"Analysis of CCDC6 as a novel biomarker for the clinical use of PARP1 inhibitors in malignant pleural mesothelioma.","date":"2019","source":"Lung cancer (Amsterdam, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/31447003","citation_count":16,"is_preprint":false},{"pmid":"30733375","id":"PMC_30733375","title":"Establishment and Characterization of Four Novel Thyroid Cancer Cell Lines and PDX Models Expressing the RET/PTC1 Rearrangement, BRAFV600E, or RASQ61R as Drivers.","date":"2019","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/30733375","citation_count":15,"is_preprint":false},{"pmid":"17109907","id":"PMC_17109907","title":"The expression of Hedgehog genes (Ihh, Dhh) and Hedgehog target genes (Ptc1, Gli1, Coup-TfII) is affected by estrogenic stimuli in the uterus of immature female rats.","date":"2006","source":"Toxicology and applied pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/17109907","citation_count":15,"is_preprint":false},{"pmid":"29244790","id":"PMC_29244790","title":"Lentivirus-mediated silencing of the PTC1 and PTC2 genes promotes recovery from spinal cord injury by activating the Hedgehog signaling pathway in a rat model.","date":"2017","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/29244790","citation_count":15,"is_preprint":false},{"pmid":"38805286","id":"PMC_38805286","title":"CCDC6-RET fusion protein regulates Ras/MAPK signaling through the fusion- GRB2-SHC1 signal niche.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/38805286","citation_count":14,"is_preprint":false},{"pmid":"33338804","id":"PMC_33338804","title":"Suppression of CCDC6 sensitizes tumor to oncolytic virus M1.","date":"2020","source":"Neoplasia (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/33338804","citation_count":14,"is_preprint":false},{"pmid":"16330160","id":"PMC_16330160","title":"Transcriptional control of Shh/Ptc1 signaling in embryonic development.","date":"2005","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/16330160","citation_count":14,"is_preprint":false},{"pmid":"20214787","id":"PMC_20214787","title":"Developmental and oncogenic effects of insulin-like growth factor-I in Ptc1+/- mouse cerebellum.","date":"2010","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/20214787","citation_count":14,"is_preprint":false},{"pmid":"15579773","id":"PMC_15579773","title":"Forskolin, 8-Br-3',5'-cyclic adenosine 5'-monophosphate, and catalytic protein kinase A expression in the nucleus increase radioiodide uptake and sodium/iodide symporter protein levels in RET/PTC1-expressing cells.","date":"2004","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/15579773","citation_count":14,"is_preprint":false},{"pmid":"21219595","id":"PMC_21219595","title":"Assessment of RET/PTC1 and RET/PTC3 rearrangements in fine-needle aspiration biopsy specimens collected from patients with Hashimoto's thyroiditis.","date":"2011","source":"Thyroid research","url":"https://pubmed.ncbi.nlm.nih.gov/21219595","citation_count":14,"is_preprint":false},{"pmid":"11598435","id":"PMC_11598435","title":"Chemoprevention of basal cell carcinomas in the ptc1+/- mouse--green and black tea.","date":"2001","source":"Skin pharmacology and applied skin physiology","url":"https://pubmed.ncbi.nlm.nih.gov/11598435","citation_count":14,"is_preprint":false},{"pmid":"17195013","id":"PMC_17195013","title":"Matrix metalloproteinase-19 expression in keratinocytes is repressed by transcription factors Tst-1 and Skn-1a: implications for keratinocyte differentiation.","date":"2006","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/17195013","citation_count":14,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51222,"output_tokens":7797,"usd":0.135311,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16461,"output_tokens":4937,"usd":0.102865,"stage2_stop_reason":"end_turn"},"total_usd":0.238176,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at the corpus, I need to identify papers about the canonical CCDC6 protein (also known as D10S170, H4, PTC1 in the context of the RET/PTC1 fusion partner — NOT the Patched1/PTCH1 gene which is also sometimes called Ptc1, NOR the yeast PP2C phosphatase Ptc1, NOR the POU domain factor Tst-1/Oct-6).\n\nThe query gene CCDC6 (D10S170, H4) is the fusion partner gene in RET/PTC1 rearrangements. Let me carefully distinguish papers about CCDC6 the protein from:\n- PTCH1/Patched1 (Hedgehog receptor, also called Ptc1 in mice) — papers [1,2,4,6,10,14,24,28,52,54,74,77,84,92,95,96,99] → EXCLUDE\n- Yeast Ptc1 (PP2C phosphatase) — papers [8,9,17,26,27,29,34,38,39,58,60,61,70] → EXCLUDE\n- Tst-1/Oct-6 (POU domain factor) — papers [11,15,63,100] → EXCLUDE\n- NPC1 Patched-like domains [7] → EXCLUDE\n- C. elegans ptc-1 [19] → EXCLUDE\n- S. pombe ptc1 [29] → EXCLUDE\n- Candida albicans ptc1 [34] → EXCLUDE\n- Plant TST1/2 [36] → EXCLUDE\n- circRNA studies [87] → EXCLUDE (non-protein product)\n\nPapers about canonical CCDC6 protein: [5,12,13,20,21,22,23,30,31,32,33,42,43,44,45,47,48,50,53,55,56,59,62,64,65,68,72,75,78,79,85,86,88,89,93,94] and several RET/PTC1 biology papers where CCDC6 function is mechanistically described.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1992,\n      \"finding\": \"CCDC6 (D10S170) is fused to the RET tyrosine kinase domain by a paracentric inversion of chromosome 10q [inv(10)(q11.2q21)], generating the RET/PTC1 oncogene in papillary thyroid carcinomas; cytogenetic and molecular analysis of tumor samples established that the chromosomal inversion breakpoints coincide with RET (10q11.2) and D10S170 (10q21) loci.\",\n      \"method\": \"Cytogenetic analysis combined with Southern blotting and FISH on papillary thyroid carcinoma samples\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (cytogenetics, Southern blot, molecular cloning) across multiple tumor samples, independently replicated in subsequent studies\",\n      \"pmids\": [\"1542652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"CCDC6 (H4/D10S170) encodes a 585-amino acid protein with no transmembrane domain, extensive alpha-helical coiled-coil regions homologous to cytoskeletal proteins (tropomyosin, vimentin, keratin, myosin heavy chain tail), and a putative SH3-binding site at the C-terminus, suggesting it is a cytoskeletal-associated protein.\",\n      \"method\": \"cDNA cloning and sequencing from human normal thyroid library; sequence analysis and structural prediction\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — sequence-based structural inference replicated across multiple subsequent studies; no direct biochemical validation of cytoskeletal interaction in this paper\",\n      \"pmids\": [\"8058316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The N-terminal region of CCDC6 (H4/D10S170) contains a coiled-coil (leucine zipper-like) oligomerization domain; in vitro assays with recombinant proteins demonstrated that this region mediates oligomerization, and the H4 promoter drives ubiquitous expression of PTC1 in diverse human tissues including thyroid.\",\n      \"method\": \"In vitro oligomerization assay with recombinant proteins; luciferase promoter assay; primer extension mapping of transcriptional start sites\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution of oligomerization with recombinant proteins, functional promoter assay; single lab\",\n      \"pmids\": [\"7753554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"CCDC6 leucine zipper-mediated dimerization is essential for the transforming activity of the PTC1 oncoprotein: the PTC1 oncoprotein forms a dimer in vivo via the H4 leucine zipper, leucine zipper-dependent dimerization is required for tyrosine hyperphosphorylation of PTC1 and for its ability to transform NIH3T3 cells, and a dominant-negative PTC1 mutant introduced into PTC1-transformed cells suppresses transformation by forming inactive heterodimers.\",\n      \"method\": \"Co-immunoprecipitation in vivo; dominant-negative transfection into NIH3T3 transformants; focus formation assay; immunokinase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, functional mutagenesis of leucine zipper, dominant-negative rescue experiment, multiple orthogonal readouts in single study\",\n      \"pmids\": [\"9083029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CCDC6 (H4/D10S170) is fused in-frame to the platelet-derived growth factor receptor beta (PDGFβR) in a t(5;10)(q33;q21.2) translocation in BCR-ABL-negative chronic myeloid leukemia; the H4-PDGFβR chimeric mRNA was detected by RT-PCR and 5'-RACE, establishing CCDC6 as a recurrent fusion partner in myeloid malignancies beyond thyroid cancer.\",\n      \"method\": \"Southern blotting, FISH, 5'-RACE PCR, RT-PCR, DNA sequencing\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal molecular methods (Southern, FISH, 5'-RACE, RT-PCR, sequencing) independently confirmed fusion\",\n      \"pmids\": [\"10910073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The H4/CCDC6-PDGFβR fusion protein requires the CCDC6 leucine zipper domain (amino acids 55–93) as well as additional H4 sequences (aa 101–386) for efficient induction of factor-independent growth; retroviral transduction of H4/PDGFβR (but not a kinase-inactive mutant) conferred factor-independent growth to Ba/F3 cells and caused T-cell lymphoblastic lymphoma in a murine bone marrow transplantation model.\",\n      \"method\": \"Retroviral transduction of Ba/F3 cells; murine bone marrow transplantation assay; mutational analysis of leucine zipper and PDGFβR domains; factor-independent growth assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro and in vivo transformation assays, systematic mutagenesis of CCDC6 dimerization domains, kinase-dead control, multiple orthogonal methods\",\n      \"pmids\": [\"11389034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CCDC6 (H4/D10S170) protein is a ubiquitously expressed 55 kDa protein found in both the nucleus and cytosol; it is phosphorylated following serum stimulation in an ERK1/2-dependent manner, and this phosphorylation correlates with relocation from nucleus to cytosol. Overexpression of full-length CCDC6 induces apoptosis of thyroid follicular cells, whereas the C-terminally truncated mutant H4(1-101) (the portion retained in RET/PTC1) acts as a dominant negative on both the pro-apoptotic function and nuclear localization of CCDC6; substitution of serine 244 with alanine abrogates the apoptotic function.\",\n      \"method\": \"Subcellular fractionation and immunofluorescence; serum stimulation with ERK inhibitor treatment; overexpression and dominant-negative transfection assays in thyroid cells; site-directed mutagenesis (S244A); conditional expression system\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (fractionation, imaging, kinase inhibitor, mutagenesis, conditional expression), single lab but comprehensive mechanistic dissection\",\n      \"pmids\": [\"14712216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RET/PTC1 associates with hsp90 and its co-chaperone p50cdc37; proteomic analysis identified these as novel RET/PTC1-interacting proteins, and hsp90 inhibition with 17-AAG reduces RET/PTC1 protein levels.\",\n      \"method\": \"Proteomic analysis (Co-immunoprecipitation followed by mass spectrometry); Western blot of 17-AAG-treated cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomic Co-IP identification with functional consequence (protein degradation upon inhibition), single lab\",\n      \"pmids\": [\"15302866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CCDC6 (H4/D10S170) undergoes ATM-mediated phosphorylation at Thr434 in response to DNA damage (etoposide or ionizing radiation); this phosphorylation stabilizes CCDC6 in the nucleus. In ATM-deficient cells, CCDC6 is excluded from the nucleus and is not phosphorylated after IR. The T434A mutant fails to induce apoptosis and protects cells from genotoxic stress; silencing of CCDC6 after IR increases cell survival, permits DNA synthesis, and allows mitotic entry, demonstrating CCDC6's role in the ATM-dependent DNA damage response.\",\n      \"method\": \"Co-immunoprecipitation; immunofluorescence in ATM-deficient and proficient cells; site-directed mutagenesis (T434A); clonogenic assay after siRNA knockdown; BrdU incorporation assay; histone H3 phosphorylation assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal approach using ATM-deficient patient cells, site-directed mutagenesis, multiple functional assays (clonogenic, BrdU, mitosis marker), single lab but multiple orthogonal methods\",\n      \"pmids\": [\"17420723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CCDC6 interacts with CREB1 and represses CREB1 transcriptional activity by recruiting histone deacetylase 1 (HDAC1) and protein phosphatase 1 (PP1) to the CRE site of CREB1 target genes; loss of CCDC6 function (as occurs in RET/PTC1 rearrangement) leads to increased CREB1 phosphorylation and elevated expression of CREB1 target genes AREG and cyclin A in PTCs.\",\n      \"method\": \"Co-immunoprecipitation (CCDC6-CREB1 interaction); chromatin immunoprecipitation showing HDAC1 and PP1 recruitment to CRE sites; reporter assays for CREB1 transcriptional activity; Western blot of CREB1 phosphorylation; RT-PCR of target gene expression in PTC samples\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP demonstrating complex recruitment to chromatin, functional reporter assays, validated in primary tumor samples; multiple orthogonal methods\",\n      \"pmids\": [\"20498639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CCDC6 loss accelerates dephosphorylation of γH2AX (pH2AX S139) following genotoxic stress, resulting in defective G2 arrest and premature mitotic entry. CCDC6 physically interacts with the catalytic subunit of protein phosphatase 4 (PP4c), the conserved pH2AX phosphatase, and CCDC6 depletion increases PP4c enzymatic activity; these data suggest CCDC6 negatively modulates PP4c to sustain the DNA damage checkpoint.\",\n      \"method\": \"High-throughput proteomic screening predicting CCDC6-PP4c interaction; Co-immunoprecipitation confirming CCDC6-PP4c binding; PP4c enzymatic activity assay in CCDC6-depleted cells; γH2AX S139 phosphorylation assay by flow cytometry/Western; cell cycle analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP validated interaction, enzymatic activity assay, cell cycle phenotype; single lab, two orthogonal methods confirming PP4c modulation\",\n      \"pmids\": [\"22655027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Loss of CCDC6 impairs the intra-S-phase checkpoint: CCDC6-depleted cells show shortened S-phase, fail to accumulate in S-phase upon etoposide treatment, accumulate DNA damage (elevated pH2AX Ser139), downregulate 14-3-3σ, and fail to sequester CDC25C phosphatase to the cytoplasm upon genotoxic stress — indicating CCDC6 is required for proper S-phase checkpoint control.\",\n      \"method\": \"Lentiviral shRNA knockdown of CCDC6 in multiple cell lines; cell cycle analysis by flow cytometry; Western blot for 14-3-3σ, CDC25C, pH2AX; immunofluorescence for CDC25C localization\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean shRNA KD with defined molecular phenotypes; multiple cell lines; single lab, several orthogonal readouts\",\n      \"pmids\": [\"22363533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FBXW7 E3 ubiquitin ligase interacts with CCDC6 and targets it for ubiquitin-mediated proteasomal degradation; ATM-mediated phosphorylation of CCDC6 at Thr434 during DNA damage response prevents the FBXW7-CCDC6 interaction and thereby stabilizes CCDC6, linking DNA damage signaling to CCDC6 protein stability.\",\n      \"method\": \"Co-immunoprecipitation of FBXW7 with CCDC6; ubiquitination assay; proteasome inhibitor treatment; site-directed mutagenesis (T434A/T434E) blocking/mimicking ATM phosphorylation; Western blot\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, in-cell ubiquitination assay, phosphomimetic mutagenesis, and functional rescue; multiple orthogonal methods establishing E3 ligase–substrate relationship\",\n      \"pmids\": [\"23108047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CCDC6 contains three sumoylation sites (K74, K266, K424) conserved in vertebrates; SUMO2 modification at these sites sequesters CCDC6 in the cytosol and reduces its ability to repress CREB1 transcriptional activity. Mutation of all three sumoylation sites abolishes this cytosolic sequestration and restores CCDC6 repressive function on CREB1. In thyroid cells, SUMO2-mediated modification is induced by Forskolin/cAMP signaling.\",\n      \"method\": \"Site-directed mutagenesis of sumoylation sites (K74R, K266R, K424R); immunofluorescence for subcellular localization of SUMO2-modified CCDC6; CREB1 reporter assay; Forskolin treatment of thyroid cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis of all three sites, functional reporter assay, imaging of localization; single lab\",\n      \"pmids\": [\"23145146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CCDC6 protein levels oscillate during the cell cycle, peaking at G2 and decreasing in mitosis; mitotic kinases promote CCDC6 degradation via phospho-degron motifs that recruit the FBXW7 E3 ubiquitin ligase, while the deubiquitinase USP7 counteracts this to stabilize CCDC6. Both FBXW7 and USP7 affect CCDC6 protein levels and, consequently, cell drug response in NSCLC cells.\",\n      \"method\": \"Cell cycle synchronization followed by Western blot and phosphorylation assays; Co-immunoprecipitation of CCDC6 with FBXW7 and USP7; USP7 inhibitor treatment; cycloheximide chase assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell cycle synchronization, Co-IP, enzymatic inhibition, cycloheximide chase — multiple orthogonal methods establishing cell-cycle-dependent turnover mechanism\",\n      \"pmids\": [\"25885523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mice carrying a Ccdc6 exon-2 deletion knock-in (which specifically impairs CCDC6-mediated CREB1 repression) develop thyroid hyperplasia with enhanced CREB1 activity and increased expression of CREB1-regulated target genes, demonstrating that CCDC6 repression of CREB1 is functionally required to prevent thyroid hyperplasia in vivo.\",\n      \"method\": \"Knock-in mouse model with Ccdc6 exon-2 deletion; immunohistochemistry of thyroid; luciferase reporter assay comparing wild-type vs. mutant Ccdc6 repression of CREB1; RT-PCR of CREB1 target genes\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knock-in model with defined molecular mechanism (CREB1 repression), corroborated by reporter assay; strong because genetic model validates the CCDC6-CREB1 pathway in vivo\",\n      \"pmids\": [\"25970781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP7 deubiquitinase is responsible for fine-tuning CCDC6 protein stability; inhibition of USP7 with P5091 accelerates CCDC6 degradation in cycloheximide chase assays and sensitizes lung neuroendocrine cancer cells to PARP inhibitors, establishing a USP7→CCDC6→PARP-inhibitor sensitivity axis.\",\n      \"method\": \"Cycloheximide chase assay with USP7 inhibitor P5091 in L-NET cells; cell viability assays with PARP inhibitor alone and in combination with cisplatinum; immunostaining correlation of CCDC6 and USP7 in TMA\",\n      \"journal\": \"Lung cancer (Amsterdam, Netherlands)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cycloheximide chase with pharmacological inhibitor, functional cell viability assay; single lab, two methods\",\n      \"pmids\": [\"27372520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The FGFR2-CCDC6 fusion protein in intrahepatic cholangiocarcinoma acts as a constitutively active oncogenic kinase; in a patient-derived xenograft model endogenously expressing FGFR2-CCDC6, FGFR inhibitors (ponatinib, dovitinib, BGJ398) modulate FGFR signaling, inhibit cell proliferation and induce apoptosis, with BGJ398 showing superior potency.\",\n      \"method\": \"Patient-derived xenograft (PDX) model; Western blot for FGFR signaling (pFGFR, downstream targets); cell proliferation assay; apoptosis assay; comparison of three FGFR inhibitors in vivo\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo PDX model with signaling readouts; single study, confirms FGFR2-CCDC6 as druggable kinase fusion\",\n      \"pmids\": [\"27216979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-146b-5p directly targets CCDC6 mRNA, reducing CCDC6 protein levels and thereby promoting PTC cell proliferation, migration, invasion, and cell cycle progression; overexpression of CCDC6 reverses these effects both in vitro and in a subcutaneous mouse model, identifying CCDC6 as a functional tumor suppressor target of miR-146b-5p in papillary thyroid cancer.\",\n      \"method\": \"Luciferase reporter assay with CCDC6 3'UTR confirming direct miR-146b-5p targeting; gain- and loss-of-function studies (miR-146b-5p overexpression and CCDC6 overexpression/knockdown) with cell proliferation, migration, invasion, and cell cycle assays; subcutaneous mouse tumor model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct target validation by luciferase assay, functional rescue by CCDC6 overexpression, in vivo model; single lab\",\n      \"pmids\": [\"30503553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CCDC6 physically interacts with BAP1 (BRCA1-associated protein-1) in malignant pleural mesothelioma cells; depletion of CCDC6 impairs homologous recombination-mediated DSB repair and sensitizes MPM cells to PARP inhibitors, and combined loss of CCDC6 and expression of mutant BAP1 (Δ221-238) further enhances HR-repair defects and PARP inhibitor sensitivity.\",\n      \"method\": \"Co-immunoprecipitation of CCDC6 with BAP1 in MPM cells; HR reporter assay; cell viability assay with PARP inhibitors; co-transfection of CCDC6 siRNA and BAP1 mutant construct\",\n      \"journal\": \"Lung cancer (Amsterdam, Netherlands)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional HR assay and drug sensitivity; single lab\",\n      \"pmids\": [\"31447003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CCDC6-RET fusion protein undergoes liquid-liquid phase separation (LLPS) dependent on both its kinase domain and the CCDC6 fusion partner; this LLPS promotes autophosphorylation and enhances kinase activity of the RET fusion. Within the resulting condensate, a ternary signal niche comprising CCDC6-RET, adaptor GRB2, and effector SHC1 is assembled, amplifying Ras/MAPK signaling efficiency in a tyrosine kinase-dependent manner.\",\n      \"method\": \"In vitro and cellular LLPS assays; autophosphorylation kinase assays; Co-immunoprecipitation of the CCDC6-RET/GRB2/SHC1 ternary complex; domain deletion mutants to define LLPS requirements; biochemical signaling assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstitution of LLPS, kinase activity assay, Co-IP of ternary complex, systematic mutagenesis to define requirements; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"38805286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CCDC6-deficient NSCLC cells show defective homologous recombination (reduced Rad51 foci), impaired DNA damage response, resistance to cisplatin, and sensitization to PARP1/2 inhibitor olaparib with a synthetic lethal effect; combining olaparib and cisplatin in CCDC6-deficient cells produces combination index <1 (synergy).\",\n      \"method\": \"Characterization of NSCLC cell lines by Western blot for CCDC6; Rad51 foci assay; HR reporter assay; clonogenic/viability assays with cisplatin, olaparib, and combination; combination index calculation\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — HR reporter assay, Rad51 foci, drug combination assays; multiple readouts of DNA repair defect; single lab\",\n      \"pmids\": [\"25302833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CCDC6 loss in germ cell-derived GC1 cells attenuates apoptotic signaling (decreased cytochrome c oxidation, reduced Bad, PARP-1, and caspase-3) and impairs γH2AX activation upon H₂O₂ oxidative damage, while reducing reactive oxygen species release and protecting cell viability; CCDC6 expression is present in Sertoli cells and spermatogonial cells of the testis but is lost in testicular germ cell tumors.\",\n      \"method\": \"shRNA silencing of CCDC6 in GC1 cells; H₂O₂ treatment; Western blot for apoptosis markers (cytochrome c, Bad, PARP-1, caspase-3); γH2AX immunofluorescence; ROS assay; immunohistochemistry of mouse and human testis sections\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA KD with multiple apoptosis and DNA damage readouts; single lab\",\n      \"pmids\": [\"24059746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In CCDC6-RET-rearranged thyroid cancer, adaptive resistance to RET inhibitors is mediated by rapid reactivation of ERK signaling via FGFR pathway activation within hours of drug exposure; combined FGFR and RET inhibition prevents adaptive ERK reactivation, reduces cell viability, and decreases tumor growth in cellular and animal models.\",\n      \"method\": \"Drug screening on CCDC6-RET patient-derived models; proteomic and biochemical profiling (phosphoproteomics, Western blot); combined RET+FGFR inhibitor treatment in vitro and in vivo xenograft\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived model, phosphoproteomic profiling, in vivo validation; single lab, multiple methods\",\n      \"pmids\": [\"35510953\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CCDC6 is a ubiquitously expressed, predominantly nuclear phosphoprotein that functions as a tumor suppressor by: (1) repressing CREB1 transcriptional activity through recruitment of HDAC1 and PP1 to CRE-containing promoters; (2) sustaining the ATM-dependent DNA damage response via ATM-mediated phosphorylation at Thr434 (which stabilizes nuclear CCDC6 and inhibits PP4c-mediated γH2AX dephosphorylation to enforce G2/S checkpoints); (3) promoting apoptosis in a serine-244-dependent manner; and (4) undergoing cell-cycle-regulated proteolysis controlled by FBXW7-mediated ubiquitination (opposed by USP7 deubiquitination) and SUMO2 modification (which redistributes CCDC6 to the cytoplasm and reduces CREB1 repression); when CCDC6 is fused to RET kinase (RET/PTC1), the retained N-terminal coiled-coil domain drives constitutive leucine-zipper-mediated dimerization and LLPS-enhanced autophosphorylation that assembles a GRB2-SHC1-containing Ras/MAPK signal niche, while loss of CCDC6 function impairs homologous recombination and confers synthetic lethality with PARP inhibitors.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CCDC6 is a ubiquitously expressed, predominantly nuclear coiled-coil phosphoprotein that functions as a tumor suppressor coordinating transcriptional repression, the DNA damage response, and apoptosis [#6, #9, #8]. It directly binds CREB1 and represses CREB1-dependent transcription by recruiting HDAC1 and PP1 to CRE-containing promoters; loss of this function elevates CREB1 phosphorylation and target genes such as AREG and cyclin A, and a knock-in mouse lacking CCDC6 CREB1-repressor activity develops thyroid hyperplasia, establishing the pathway as physiologically protective [#9, #15]. In the DNA damage response, CCDC6 is phosphorylated by ATM at Thr434, which stabilizes the nuclear protein and is required to enforce S-phase and G2 checkpoints; mechanistically CCDC6 restrains the γH2AX phosphatase PP4c to sustain damage signaling, and its depletion accelerates γH2AX dephosphorylation, shortens S-phase, and permits premature mitotic entry [#8, #10, #11]. CCDC6 also supports homologous-recombination repair—its loss reduces Rad51 foci and confers synthetic lethality with PARP inhibitors—and physically interacts with BAP1 in this context [#21, #19]. CCDC6 abundance is cell-cycle-regulated, peaking at G2 and degraded in mitosis through phospho-degron–directed FBXW7 ubiquitination opposed by USP7 deubiquitination, while SUMO2 modification redistributes CCDC6 to the cytoplasm and relieves CREB1 repression [#14, #12, #13]. CCDC6 is recurrently disrupted by chromosomal rearrangements that fuse its N-terminal coiled-coil to receptor tyrosine kinases—RET (RET/PTC1) in papillary thyroid carcinoma, PDGFβR in chronic myeloid leukemia, and FGFR2 in cholangiocarcinoma—where the leucine-zipper drives constitutive dimerization required for kinase activation and transformation [#0, #4, #17, #3]. For the CCDC6-RET oncoprotein, the fusion-driven liquid-liquid phase separation enhances autophosphorylation and assembles a GRB2-SHC1 signaling niche that amplifies Ras/MAPK output [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established CCDC6 as a recurrent cancer gene by identifying its fusion to the RET kinase, defining the RET/PTC1 oncogene of papillary thyroid carcinoma.\",\n      \"evidence\": \"Cytogenetics, Southern blot, and FISH on papillary thyroid carcinoma samples\",\n      \"pmids\": [\"1542652\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the normal cellular function of CCDC6\", \"Mechanism of oncogenic activation by fusion unaddressed\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Cloning revealed CCDC6 as a 585-residue coiled-coil protein, providing the structural basis for later dimerization and fusion studies.\",\n      \"evidence\": \"cDNA cloning/sequencing and structural prediction from human thyroid library\",\n      \"pmids\": [\"8058316\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cytoskeletal association inferred from sequence, not biochemically validated\", \"No functional assay\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed that the CCDC6 leucine zipper is the molecular driver of fusion oncogenicity, mediating dimerization needed for RET/PTC1 kinase activation and transformation.\",\n      \"evidence\": \"In vivo Co-IP, leucine-zipper mutagenesis, dominant-negative rescue, and focus formation in NIH3T3 cells\",\n      \"pmids\": [\"9083029\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address wild-type CCDC6 function\", \"Biophysical basis of dimerization-driven activation unresolved until LLPS work\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Extended CCDC6's fusion repertoire beyond thyroid cancer by identifying the CCDC6-PDGFβR fusion in BCR-ABL-negative CML, with the leucine zipper required for transformation.\",\n      \"evidence\": \"Southern blot, FISH, 5'-RACE, RT-PCR in CML; Ba/F3 transduction and murine bone marrow transplant\",\n      \"pmids\": [\"10910073\", \"11389034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not test whether wild-type CCDC6 loss contributes to leukemogenesis\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined wild-type CCDC6 as a ubiquitous nuclear/cytosolic phosphoprotein that is pro-apoptotic, with ERK-driven phosphorylation controlling nuclear-cytosolic shuttling and serine-244 required for apoptosis.\",\n      \"evidence\": \"Subcellular fractionation, immunofluorescence, ERK inhibitor, S244A mutagenesis, conditional expression in thyroid cells\",\n      \"pmids\": [\"14712216\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Apoptotic effector pathway downstream of S244 not defined\", \"Direct kinase acting on S244 not identified\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected CCDC6 to the ATM-dependent DNA damage response, showing ATM phosphorylates Thr434 to stabilize nuclear CCDC6 and enforce cell-cycle arrest after damage.\",\n      \"evidence\": \"Co-IP, immunofluorescence in ATM-deficient/proficient cells, T434A mutagenesis, clonogenic and BrdU assays\",\n      \"pmids\": [\"17420723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors of nuclear CCDC6 in checkpoint enforcement not yet identified\", \"Direct ATM-CCDC6 phosphorylation not shown in vitro\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified the transcriptional repressor mechanism: CCDC6 binds CREB1 and recruits HDAC1 and PP1 to CRE sites, explaining how CCDC6 loss drives CREB1 target overexpression in thyroid cancer.\",\n      \"evidence\": \"Co-IP, ChIP for HDAC1/PP1 at CRE sites, CREB1 reporter assays, target gene RT-PCR in PTC samples\",\n      \"pmids\": [\"20498639\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry/order of HDAC1 and PP1 recruitment unresolved\", \"Genome-wide CREB1 targets controlled by CCDC6 not mapped\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved how CCDC6 sustains the damage checkpoint mechanistically—by restraining the γH2AX phosphatase PP4c and supporting intra-S-phase checkpoint components—linking its loss to genomic instability.\",\n      \"evidence\": \"Proteomic screen, Co-IP of CCDC6-PP4c, PP4c activity and γH2AX assays, shRNA knockdown with cell-cycle/CDC25C analyses\",\n      \"pmids\": [\"22655027\", \"22363533\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CCDC6 inhibits PP4c directly or via an adaptor unresolved\", \"Structural basis of PP4c modulation unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established the degradation control of CCDC6 by FBXW7 and its coupling to damage signaling, showing ATM phosphorylation at Thr434 blocks FBXW7 binding to stabilize CCDC6, plus SUMO2-driven cytoplasmic sequestration that relieves CREB1 repression.\",\n      \"evidence\": \"Co-IP, in-cell ubiquitination, phosphomimetic mutagenesis (FBXW7); sumoylation-site mutagenesis with localization imaging and reporter assays\",\n      \"pmids\": [\"23108047\", \"23145146\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"SUMO E3 ligase for CCDC6 not identified\", \"Crosstalk between SUMOylation and FBXW7 turnover not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated CCDC6's role in homologous recombination, showing its loss reduces Rad51 foci, impairs HR, and confers synthetic lethality with PARP inhibitors, defining a therapeutic vulnerability.\",\n      \"evidence\": \"Rad51 foci and HR reporter assays, clonogenic/viability assays with cisplatin and olaparib, combination index in NSCLC cells\",\n      \"pmids\": [\"25302833\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct role of CCDC6 protein at HR sites not biochemically defined\", \"Mechanism linking CCDC6 loss to reduced Rad51 loading unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided in vivo genetic proof that CCDC6-mediated CREB1 repression is tumor-suppressive, and refined cell-cycle-coupled turnover via FBXW7-USP7 antagonism affecting drug response.\",\n      \"evidence\": \"Ccdc6 exon-2 deletion knock-in mouse with thyroid IHC and reporter assays; cell-cycle synchronization, Co-IP, USP7 inhibitor and cycloheximide chase\",\n      \"pmids\": [\"25970781\", \"25885523\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mitotic kinases generating the phospho-degron not fully enumerated\", \"Whether CREB1 repression and checkpoint roles are genetically separable in vivo untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended the turnover axis therapeutically, showing USP7 fine-tunes CCDC6 stability and its inhibition sensitizes neuroendocrine lung cancer to PARP inhibitors.\",\n      \"evidence\": \"Cycloheximide chase with USP7 inhibitor P5091, viability assays, CCDC6/USP7 TMA correlation in L-NET cells\",\n      \"pmids\": [\"27372520\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"USP7 may target other substrates contributing to sensitivity\", \"Direct USP7-CCDC6 catalytic relationship not structurally defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked CCDC6 to BAP1 in HR repair, showing physical interaction and additive HR defects and PARP-inhibitor sensitivity in mesothelioma.\",\n      \"evidence\": \"Co-IP of CCDC6-BAP1, HR reporter, viability assays, co-transfection with mutant BAP1 in MPM cells\",\n      \"pmids\": [\"31447003\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of CCDC6-BAP1 binding at chromatin not defined\", \"Single Co-IP context; reciprocal validation limited\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed the biophysical mechanism of CCDC6-RET fusion oncogenicity: LLPS driven by the CCDC6 partner enhances autophosphorylation and assembles a GRB2-SHC1 signaling niche to amplify Ras/MAPK signaling.\",\n      \"evidence\": \"In vitro/cellular LLPS assays, autophosphorylation kinase assays, Co-IP of the ternary complex, domain-deletion mutagenesis\",\n      \"pmids\": [\"38805286\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether wild-type CCDC6 undergoes physiological LLPS untested\", \"Therapeutic targetability of the condensate not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CCDC6's distinct functions—CREB1 repression, PP4c restraint, HR support, and apoptosis—are mechanistically integrated and differentially deployed across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of CCDC6 in any of its complexes\", \"Direct biochemical role of CCDC6 at HR/repair sites undefined\", \"Tissue-specific determinants of which CCDC6 function dominates unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [9, 15]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [8, 10, 21]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [9, 15]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [11, 14]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [20]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6, 22]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CREB1\", \"HDAC1\", \"PP1\", \"PP4c\", \"FBXW7\", \"USP7\", \"BAP1\", \"RET\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}