CCDC68

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).

1. 2014 Medium

   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

   PMID:25381825

   Open questions at the time

   • No molecular mechanism for the tumor-suppressive activity identified at this stage
   • Subcellular localization and direct partners not defined
   • Single-lab study
2. 2017 High

   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

   PMID:28422092

   Open questions at the time

   • Structural basis of CEP170 binding and CCDC120 competition not resolved
   • Relationship between this centrosomal role and the tumor phenotypes not established
3. 2020 Low

   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

   PMID:33133256

   Open questions at the time

   • Single knockdown approach without rescue or pathway placement
   • No biochemical mechanism for the anti-apoptotic effect
   • Discrepancy with tumor-suppressive role in PDAC unexplained
4. 2021 Medium

   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

   PMID:33968776

   Open questions at the time

   • No direct biochemical reconstitution of the CCDC68–ITCH–CDK4 axis
   • How CCDC68 upregulates ITCH is unknown
5. 2021 Medium

   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

   PMID:33471616

   Open questions at the time

   • Direct biochemical mechanism downstream of IL-6 not defined
   • Link to the centriolar or kinetochore functions unexplored
6. 2024 High

   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

   PMID:39018254

   Open questions at the time

   • Structural basis of CDC20 binding and inhibition not resolved
   • Whether checkpoint dysfunction underlies the cancer phenotypes not tested

• How CCDC68's centriolar appendage role, kinetochore checkpoint role, and opposing context-dependent cancer functions are mechanistically unified remains unresolved.
• 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