Abstract 5682: Synergism of PARP inhibitor and MET inhibitor in multiple cancer types with intrinsic and acquired PARP inhibitor resistances
Authors: Chen Mei-Kuang , Xia Weiya , Dong Qiongzhu , Du Yi , Wang Hung-Ling , Tapia Coya , Wei Yongkun , Han Ye , Chu Yu-Yi , Yam Clinton , Gao Yuan , Wang Yu-Han , Meric-Bernstam Funda , Liu Jinsong , Wang Shao-Chun , Yu Dihua , Hung Mien-Chie 
Published: September 2020

Abstract
Leveraging compromised DNA damage repair (DDR) pathways commonly found in tumor cells, a classic strategy in cancer therapy is inducing excessive DNA damage to cause cancer cell death. Small molecule poly(ADP-ribose) polymerase (PARP) inhibitors (PARP-is) have been approved for clinical use in treating breast cancer and ovarian cancer patients bearing DDR-deficient tumors with mutations in breast cancer susceptibility proteins (BRCAm). However, accumulating evidences show that both intrinsic and acquired resistances to PARP-is exist in clinic and pre-clinical animal models. Therefore, we developed panels of cells with acquired PARP-is resistance from PARP-is-sensitive triple negative breast cancer (TNBC) and estrogen receptor positive breast cancer cell lines, and used these cells to screen for common traits that can be targeted with feasible therapeutic agent combinations to overcome PARP-is resistance. Since TNBC lacks of effective targeted therapy so far, we focused on using the panel of PARP-is-resistant TNBC cells in this study. Among the molecular mechanisms known contribute to PARP-is resistance, oncogenic kinase activations, including several hyper-activated receptor tyrosine kinases (RTKs), are involved in enhancing DNA damage repair and decreasing affinity of PARP-is to PARP1. In this study, we systematically screened for activated RTKs in the PARP-is-resistant cells we developed by antibody arrays. We then identified that activations of MET, Axl and EphA2 were common traits in TNBC cells with acquired PARP-is resistance, but not in estrogen receptor positive cells. Among the three RTKs, MET has more small molecules inhibitors that can target it, and thus, we made it a priority in investigating synergism between MET inhibitor and PARP inhibitor in multiple cancer types including TNBC with intrinsic and acquired PARP-is-resistance, high-grade serous ovarian cancer (HGSOC) and liver cancer cells. Here, we demonstrated that combinations of PARP-is and MET inhibitors (MET-is) possess moderate to strong synergism in the different cancer types we studied. As we previously reported that MET translocates into cell nucleus and phosphorylates PARP1 at tyrosine (Y) 907 residue in TNBC with intrinsic PARP-is resistance, we found that this MET-mediated PARP1-Y907 phosphorylation also exist in and can serve as marker to indicate PARP-is resistance among the HGSOC, liver cancer cells and the TNBC cells with acquired PARP-is resistance. We further found that MET phosphorylation is high (immunohistological staining H-score greater than 200) in breast cancer (23 out of 31, 70%) and ovarian cancer (8 out of 23, 35%) patient-derived xenograft mouse model tissue microarrays, suggesting that the combination of MET-is and PARP-is is likely to benefit a huge population of cancer patient in multiple cancer types.
Citation Format: Mei-Kuang Chen, Weiya Xia, Qiongzhu Dong, Yi Du, Hung-Ling Wang, Coya Tapia, Yongkun Wei, Ye Han, Yu-Yi Chu, Clinton Yam, Yuan Gao, Yu-Han Wang, Funda Meric-Bernstam, Jinsong Liu, Shao-Chun Wang, Dihua Yu, Mien-Chie Hung. Synergism of PARP inhibitor and MET inhibitor in multiple cancer types with intrinsic and acquired PARP inhibitor resistances [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5682.