NSCLC Mutated Isoforms of CCDC6 Affect the Intracellular Distribution of the Wild Type Protein Promoting Cisplatinum Resistance and PARP Inhibitors Sensitivity in Lung Cancer Cells

CCDC6 is implicated in cell cycle checkpoints and DNA damage repair by homologous recombination (HR). In NSCLC, CCDC6 is barely expressed in about 30% of patients and CCDC6 gene rearrangements with RET and ROS kinases are detected in about 1% of patients. Recently, CCDC6 point-mutations naming E227K, S351Y, N394Y, and T462A have been identified in primary NSCLC. In this work, we analyze the effects exerted by the CCDC6 mutated isoforms on lung cancer cells. By pull-down experiments and immunofluorescence, we evaluated the biochemical and morphological effects of CCDC6 lung-mutants on the CCDC6 wild type protein. By using two HR-reporter assays, we analyzed the effect of CCDC6 lung-mutants in perturbing CCDC6 physiology in the HR process. Finally, by cell-titer assay, we evaluated the response to the treatment with different drugs in lung cancer cells expressing CCDC6 mutants. This work shows that the CCDC6 mutated and truncated isoforms, identified so far in NSCLC, affected the intracellular distribution of the wild type protein and impaired the CCDC6 function in the HR process, ultimately inducing cisplatinum resistance and PARP-inhibitors sensitivity in lung cancer cells. The identification of selected molecular alterations involving CCDC6 gene product might define predictive biomarkers for personalized treatment in NSCLC.