CCDC6 (coiled-coil domain containing 6)

2015-06-01   Francesco Morra , Caterina Miro , Virginia Napolitano , Francesco Merolla , Angela Celetti 

Istituto per lEndocrinologia e lOncologia Sperimentale, IEOS, CNR, via Pansini 5, 80131, Naples, Italy.,,,,




CCDC6 gene product is a pro-apoptotic protein substrate of ATM whose loss or inactivation enhances tumor progression. In primary tumors the impaired function of CCDC6 protein has been ascribed to CCDC6 rearrangements, to somatic mutations and to CCDC6 different levels in several neoplasia. The CCDC6 turnover is regulated in a cell cycle dependent manner upon post-translational modification events. The impairment of CCDC6 turnover may affect cells behaviour and drug response.



The CCDC6 gene (Coiled Coil Containing 6) has been identified upon its frequent rearrangement with the RET proto-oncogene in papillary thyroid carcinomas (Fusco et al., 1987; Grieco et al., 1990), and with genes other than RET in solid and not solid tumours (Drechsler et al., 2007). Recently, by using an integrated molecular- and histopathology- based screening, the fusion CCDC6/RET has been also detected in lung adenocarcinoma, even at low frequency (Takeuchi et al., 2012).
The CCDC6 gene is located on the long arm of chromosome 10 (10q21), and contains 9 exons that encode a transcript of 3 Kb showing an open reading frame (ORF) of 475 aa. The CCDC6 gene promoter, localized within 259 bp upstream of the ATG site, drives the gene expression ubiquitously in various human tissue (Tong et al., 1995). In tumors harboring the RET/PTC1 rearrangement, the activation of RET involves chromosomal inversion of the long arm of chromosome 10 that juxtaposes the tyrosine kinase-encoding domain of RET, mapped at 10q11.2, to the promoter and the first exon of the CCDC6 gene, originally named H4(D10S170) (Pierotti et al., 1992).


None reported



474 amino acid coiled coil protein. Its predicted amino-acid (aa) sequence contains a long coiled coil region and a putative binding domain for SH3-proteins, suggesting its possible involvement in protein-protein interactions (Grieco et al., 1994). CCDC6 gene product shows extensive regions of alpha helices which have a high potential to adopt a coiled-coil conformation. Coiled-coils are formed by two or three alpha-helices that are strongly amphipathic and supercoil around each other, crossing at an angle of about 20- (Lupas et al., 1991). It has been demonstrate that such region can be involved in protein dimerization or oligomerization. CCDC6 protein is an ubiquitously expressed 65 KDa nuclear and cytosolic protein phosphorylated by ERK1/2 at serine 244 upon serum induction (Grieco et al., 1994; Celetti et al., 2004). In the last years, several large-scale phosphorylation site-mapping studies have recognized CCDC6 as a phosphoprotein (Beausoleil et al., 2004; Brill et al., 2004) (Figure 1).
CCDC6 has been recognized as a pro-apoptotic protein, while the CCDC6 protein truncated at the carboxyterminus, such as in the fusion with different oncogenes, acts as dominant negative on nuclear localization and apoptosis induced by the wild-type protein (Celetti et al., 2004). CCDC6 is phosphorylated at T434 by the ATM kinase that stabilizes the protein in the nucleus in response to DNA damage. The loss of the CCDC6 region recognised by ATM kinase or the full protein deficiency determines an increase in cell survival, allows for DNA synthesis and permits cell to progress into mitosis, following the exposure to genotoxic stress (Merolla et al., 2007).
CCDC6 gene product undergoes multiple post-translational modifications such as sumoylation (Luise et al., 2012), ubiquitination (Povlsen et al., 2012; Morra et al., 2015), and phosphorylation (Celetti et al., 2004; Beausoleil et al., 2004; Brill et al., 2004; Morra et al., 2015), suggesting that CCDC6 protein activity is highly regulated (Figure 3).
Atlas Image
Fig. 1: Putative phosphorylation sites in CCDC6 protein. The arrows indicate the ERK1/2 and the ATM kinases predicted phosphorylation sites.


Widely expressed, cell cycle regulated, post translational modified


Proapoptotic and cell cycle regulated protein, involved in DNA damage and repair.
Further supporting a role of CCDC6 in control of cell proliferation, it has been reported that CCDC6 interacts with CREB1 and inhibits its cAMP-dependent transcriptional activity (Leone et al., 2010) in a SUMO-dependent manner (Luise et al., 2012). Interestingly, CCDC6 knock-in mice develop thyroid hyperplasia associated to an enhanced CREB1 activity (Leone V et al., 2015), supporting a likely role of the haploinsufficiency of CCDC6 expression in the development of thyroid papillary carcinomas carrying the RET/PTC1 rearrangements.
High-throughput proteomic screening predicted the interaction between CCDC6 and the catalytic subunit of Protein Phosphatase 4 (PP4c) (Ewing et al., 2007) that has been confirmed in vitro and in vivo (Merolla et al., 2012). Moreover, it has been demonstrate that cells depleted of CCDC6 have an enhanced phosphatase activity directed toward the phosphorylation of the H2AX protein in response to ionizing radiation (IR). Loss of CCDC6 also affects the DNA damage induced G2 arrest, promoting the overcome of G2/M checkpoint. Furthermore, loss of CCDC6 affects the DNA repair mechanisms in G2 and increases the levels of the error prone mechanism of repair, Non Homologous End Joining, (NHEJ ) (Merolla et al., 2012). In recent studies it has been reported that the E3 ubiquitin ligase FBXW7 specifically interacts with CCDC6 driving its degradation in a proteasomal dependent manner (Zhao et al., 2012). Moreover, CCDC6 degradation is impaired in response to DNA damage. The post translational events that regulate the phosphorylation status and the abundance of CCDC6 during the cell cycle have been also investigated (Morra et al., 2015a).
In human cancers, it has been recently reported that the loss of CCDC6 in the Testicular Germ Cell Tumors (TGCTs) might aid the spermatogonial cells to benefit from a pro-survival pathway in order to evade the toxic effects of endogenous oxidants and then promote testicular neoplastic growth (Staibano et al., 2013). Furthermore, in NSCLC, TMA immunostaining for CCDC6 revealed low CCDC6 expression in about 30% of the NSCLC analyzed (45 out of 138), besides the low penetrance of reported CCDC6 mutations or CCDC6/RET rearrangements. The defective expression of CCDC6 in NSCLC has been negatively correlated to DFS and OS (Morra et al., 2015b). Moreover, the defective expression of CCDC6 causes an impairment of DNA repair by homologous recombination (HR) in NSCLC cells, making these cells sensitive to PARP inhibitors. Finally, it has been reported that beside the CCDC6 sporadic mutations, molecular alterations in CCDC6 modifiers, such as Fbxw7 E3 ubiquitin ligase or USP7 de-ubiquitinating enzyme, may also account for the impairment of the CCDC6 turnover and may be critical in optimizing personalized therapy. About 20% of primary NSCLC exhibit reduced USP7 expression and also show barely detectable levels of CCDC6 that may increase their sensitivity to PARP inhibitors (Morra et al., 2015a). Therefore, the indication of CCDC6 as a novel USP7 substrate provides the rational for novel personalized therapy in NSCLC patients carrying USP7 deficiency.
Therefore, as the loss of CCDC6 causes an impairment of DNA repair by homologous recombination, in tumors that harbor low levels of USP7, the detection of low levels of its substrate CCDC6 should provide the indications for the PARP inhibitors treatment (Morra et al., 2015b).
Atlas Image
Fig. 2: CCDC6 interactors and modifiers.


Sequencing analysis of CCDC6 cDNA shows that CCDC6 has not significant homology to know genes. Weak but significant homology to the myosin superfamily.


Atlas Image
Fig. 3 : CCDC6 rearrangements. The red arrow shows the RET/PTC1 and the black one shows the CCDC6/PDGFRB breakpoint.




Point mutations: TCGAcbioPortal& Cosmic -CCDC6 - dist

Implicated in

Entity name
Papillary thyroid carcinoma
inv(10)(q11.2q21) or t(10;10)(q11;q21) CCDC6/RET
t(8;10)(q22;q21) VPS13B/CCDC6
Hybrid gene
Fusion protein
The fusion protein CCDC6/RET contains the first 101 aminoacids including part of CCDC6 coiled coil domain and the entire tyrosine kinase domain of RET. The fusion is a constitutively active tyrosine kinase.
In transgenic mice the fusion CCDC6/RET gave rise to mammary adenocarcinomas and, less frequently, hyperplasia of sebaceous glands and rare benign skin tumors. CCDC6 knock in mice develop thyroid hyperplasia associated with an enhanced CREB1 activity.
The simultaneous occurrence of CCDC6/PTEN, RET/PTC and BRAF mutations have been reported in papillary thyroid carcinomas.
Entity name
negative chronic myeloid leukaemia / chronic myelomonocytic leukemia
atypical chronic myeloid leukemia
Too few cases reported but likely to be similar to CML
Hybrid gene
CCDC6/PDGFRB. In a single case analyzed the translocation was found to be complex at the molecular level.
Fusion protein
Contains the first 368 amminoacids including part of CCDC6 coiled coil domain of CCDC6 and the leucine zipper of H4 and the entire tyrosine kinase domain and transmembrane domain of PDGFRB
Entity name
Non-small-cell lung cancer (NSCLC)
Adenocarcinoma (NSCLC)
inv(10)(q11.2q21) or t(10;10)(q11;q21) CCDC6/RET
t(10;10)(q21;q21) CCDC6/CTNNA3
t(10;21)(q21;q11) CCDC6/LIPI
Hybrid gene
Fusion protein
Contains the first 101 amino acids including part of CCDC6 coiled coil domain of CCDC6
Entity name
Breast cancer
t(10;10)(q21;q26) FGFR2/CCDC6
t(10;10)(q21;q21) CCDC6/UBE2D1
Hybrid gene
Entity name
Ovarian epithelial tumor
t(10;10)(q21;q21) CCDC6/ANK3
Hybrid gene


Atlas Image


Pubmed IDLast YearTitleAuthors
153029352004Large-scale characterization of HeLa cell nuclear phosphoproteins.Beausoleil SA et al
151441862004Robust phosphoproteomic profiling of tyrosine phosphorylation sites from human T cells using immobilized metal affinity chromatography and tandem mass spectrometry.Brill LM et al
147122162004H4(D10S170), a gene frequently rearranged with RET in papillary thyroid carcinomas: functional characterization.Celetti A et al
172115202007Fusion of H4/D10S170 to PDGFRbeta in a patient with chronic myelomonocytic leukemia and long-term responsiveness to imatinib.Drechsler M et al
173539312007Large-scale mapping of human protein-protein interactions by mass spectrometry.Ewing RM et al
36007951987A new oncogene in human thyroid papillary carcinomas and their lymph-nodal metastases.Fusco A et al
80583161994Cloning and characterization of H4 (D10S170), a gene involved in RET rearrangements in vivo.Grieco M et al
24060251990PTC is a novel rearranged form of the ret proto-oncogene and is frequently detected in vivo in human thyroid papillary carcinomas.Grieco M et al
111147392000The RET proto-oncogene in human cancers.Jhiang SM et al
109100732000Fusion of H4/D10S170 to the platelet-derived growth factor receptor beta in BCR-ABL-negative myeloproliferative disorders with a t(5;10)(q33;q21).Kulkarni S et al
259707812015Ccdc6 knock-in mice develop thyroid hyperplasia associated to an enhanced CREB1 activity.Leone V et al
204986392010CCDC6 represses CREB1 activity by recruiting histone deacetylase 1 and protein phosphatase 1.Leone V et al
231451462012Identification 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.Luise C et al
20311851991Predicting coiled coils from protein sequences.Lupas A et al
226550272012Loss of CCDC6, the first identified RET partner gene, affects pH2AX S139 levels and accelerates mitotic entry upon DNA damage.Merolla F et al
174207232007Involvement of H4(D10S170) protein in ATM-dependent response to DNA damage.Merolla F et al
258855232015FBXW7 and USP7 regulate CCDC6 turnover during the cell cycle and affect cancer drugs susceptibility in NSCLC.Morra F et al
15426521992Characterization of an inversion on the long arm of chromosome 10 juxtaposing D10S170 and RET and creating the oncogenic sequence RET/PTC.Pierotti MA et al
89345501996Development of mammary and cutaneous gland tumors in transgenic mice carrying the RET/PTC1 oncogene.Portella G et al
230009652012Systems-wide analysis of ubiquitylation dynamics reveals a key role for PAF15 ubiquitylation in DNA-damage bypass.Povlsen LK et al
159471062005RET/PTC-induced gene expression in thyroid PCCL3 cells reveals early activation of genes involved in regulation of the immune response.Puxeddu E et al
113890342001H4(D10S170), a gene frequently rearranged in papillary thyroid carcinoma, is fused to the platelet-derived growth factor receptor beta gene in atypical chronic myeloid leukemia with t(5;10)(q33;q22).Schwaller J et al
240597462013Critical role of CCDC6 in the neoplastic growth of testicular germ cell tumors.Staibano S et al
77535541995Characterization of the promoter region and oligomerization domain of H4 (D10S170), a gene frequently rearranged with the ret proto-oncogene.Tong Q et al
90830291997Leucine zipper-mediated dimerization is essential for the PTC1 oncogenic activity.Tong Q et al
231080419905HT2 receptor changes in major depression.Yates M et al

Other Information

Locus ID:

NCBI: 8030
MIM: 601985
HGNC: 18782
Ensembl: ENSG00000108091


dbSNP: 8030
ClinVar: 8030
TCGA: ENSG00000108091


Gene IDTranscript IDUniprot

Expression (GTEx)



PathwaySourceExternal ID
Thyroid cancerKEGGko05216
Pathways in cancerKEGGhsa05200
Thyroid cancerKEGGhsa05216

Protein levels (Protein atlas)

Not detected


Pubmed IDYearTitleCitations
223276232012RET, ROS1 and ALK fusions in lung cancer.387
184748712008Common SNP in pre-miR-146a decreases mature miR expression and predisposes to papillary thyroid carcinoma.281
163854512006A scan of chromosome 10 identifies a novel locus showing strong association with late-onset Alzheimer disease.69
203796142010Personalized smoking cessation: interactions between nicotine dose, dependence and quit-success genotype score.62
197306832009The variant rs1867277 in FOXE1 gene confers thyroid cancer susceptibility through the recruitment of USF1/USF2 transcription factors.59
231545602012Identification of CCDC6-RET fusion in the human lung adenocarcinoma cell line, LC-2/ad.34
235781752013Identification of a lung adenocarcinoma cell line with CCDC6-RET fusion gene and the effect of RET inhibitors in vitro and in vivo.22
272169792016Antitumor effect of FGFR inhibitors on a novel cholangiocarcinoma patient derived xenograft mouse model endogenously expressing an FGFR2-CCDC6 fusion protein.20
174207232007Involvement of H4(D10S170) protein in ATM-dependent response to DNA damage.18
253028332015New therapeutic perspectives in CCDC6 deficient lung cancer cells.18


Francesco Morra ; Caterina Miro ; Virginia Napolitano ; Francesco Merolla ; Angela Celetti

CCDC6 (coiled-coil domain containing 6)

Atlas Genet Cytogenet Oncol Haematol. 2015-06-01

Online version:

Historical Card

2001-06-01 CCDC6 (coiled-coil domain containing 6) by  Nick.C P Cross 

Wessex Regional Genetics Laboratory Salisbury District Hospital Salisbury, SP2 8BJ, UK