Francesco Morra1, Francesco Merolla2, Debora D'Abbiero1, Gennaro Ilardi3, Severo Campione4, Roberto Monaco4, Gianluca Guggino5, Francesca Ambrosio6, Stefania Staibano3, Aniello Cerrato1, Roberta Visconti1, Angela Celetti7. 1. Institute for the Experimental Endocrinology and Oncology, National Research Council, Naples, Italy. 2. Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy; Department of Advanced Biomedical Sciences, University "Federico II", Naples, Italy. 3. Department of Advanced Biomedical Sciences, University "Federico II", Naples, Italy. 4. Pathology Unit, A. Cardarelli Hospital, Naples, Italy. 5. Thoracic Surgery Unit, A. Cardarelli Hospital, Naples, Italy. 6. Oncology Unit, A. Cardarelli Hospital, Naples, Italy. 7. Institute for the Experimental Endocrinology and Oncology, National Research Council, Naples, Italy. Electronic address: celetti@unina.it.
Abstract
OBJECTIVES: CCDC6 (coiled-coil domain containing 6) is a player of the HR response to DNA damage and has been predicted to interact with BAP1, another HR-DNA repair gene highly mutated in Malignant Pleural Mesothelioma (MPM), an aggressive cancer with poor prognosis. CCDC6 levels are modulated by the deubiquitinase USP7, and CCDC6 defects have been reported in several tumors determining PARP-inhibitors sensitivity. Our aim was to investigate the functional role of CCDC6 in MPM carcinogenesis and response to PARP-inhibitors. MATERIALS AND METHODS: The interaction between CCDC6 and BAP1 was confirmed in MPM cells, by co-immunoprecipitation. Upon USP7 inhibition, that induces CCDC6 degradation, the ability to repair the DSBs and the sensitivity to PARP inhibitors, was explored by HR reporter and by cells viability assays, respectively. A TMA including 34 MPM cores was immunostained for CCDC6, USP7 and BAP1 and the results correlated by statistical analysis. RESULTS: MPM cells depleted of CCDC6 showed defects in DSBs repair and sensitivity to PARP inhibitors. The silencing of CCDC6 when combined with the overexpression of BAP1-mutant (Δ221-238) enhanced the HR-DNA repair defects and the PARP inhibitors sensitivity. In the TMA of MPM primary samples, the staining of CCDC6 and of its de-ubiquitinase USP7 showed a significant correlation in the tested primary samples (p = 0.01). CCDC6 was barely detected in 30% of the tumors that also carried BAP1 defects. CONCLUSION: The combination of CCDC6 and BAP1 staining may indicate therapeutic options for DDR targeting, acting in synergism with cisplatinum.
OBJECTIVES:CCDC6 (coiled-coil domain containing 6) is a player of the HR response to DNA damage and has been predicted to interact with BAP1, another HR-DNA repair gene highly mutated in Malignant Pleural Mesothelioma (MPM), an aggressive cancer with poor prognosis. CCDC6 levels are modulated by the deubiquitinase USP7, and CCDC6 defects have been reported in several tumors determining PARP-inhibitors sensitivity. Our aim was to investigate the functional role of CCDC6 in MPM carcinogenesis and response to PARP-inhibitors. MATERIALS AND METHODS: The interaction between CCDC6 and BAP1 was confirmed in MPM cells, by co-immunoprecipitation. Upon USP7 inhibition, that induces CCDC6 degradation, the ability to repair the DSBs and the sensitivity to PARP inhibitors, was explored by HR reporter and by cells viability assays, respectively. A TMA including 34 MPM cores was immunostained for CCDC6, USP7 and BAP1 and the results correlated by statistical analysis. RESULTS: MPM cells depleted of CCDC6 showed defects in DSBs repair and sensitivity to PARP inhibitors. The silencing of CCDC6 when combined with the overexpression of BAP1-mutant (Δ221-238) enhanced the HR-DNA repair defects and the PARP inhibitors sensitivity. In the TMA of MPM primary samples, the staining of CCDC6 and of its de-ubiquitinase USP7 showed a significant correlation in the tested primary samples (p = 0.01). CCDC6 was barely detected in 30% of the tumors that also carried BAP1 defects. CONCLUSION: The combination of CCDC6 and BAP1 staining may indicate therapeutic options for DDR targeting, acting in synergism with cisplatinum.
Authors: Francesco Morra; Francesco Merolla; Giovanna Damia; Francesca Ricci; Silvia Varricchio; Gennaro Ilardi; Laura Arenare; Daniela Califano; Virginia Napolitano; Robert Fruscio; Rosa Marina Melillo; Luca Palazzo; Angela Celetti Journal: J Exp Clin Cancer Res Date: 2022-08-13