LAUSR

DNA-dependent protein kinase (DNA-PK) plays an important role in the repair of DNA double-strand breaks via the non-homologous end joining (NHEJ) pathway. In addition to its role in the NHEJ pathway, DNA-PK is also known to have an emerging role in cell cycle progression and mitosis. Some studies have shown that depletion or inhibition of DNA-PK inhibitors leads to a delay in the transition from metaphase to anaphase. The mitotic MTH1 inhibitor OXC-101(TH1579, karonudib) is a dual inhibitor that both targets MTH1 and disrupts tubulin polymerization in cancer cells, causing DNA damage and mitotic catastrophe in cancer cells. Based on the involvement of DNA-PK in mitosis, we hypothesized that depletion/inhibition of DNA-PK might enhance the DNA damage and mitotic catastrophic effect of OXC-101.To test our hypothesis, we performed an in vitro drug combination experiment using the DNA-PK inhibitor nedisertib with OXC-101 in non-small cell lung carcinoma NSCLC (H460,A549), uveal melanoma (MP -38, MP -41 and MP46), osteosarcoma (U2OS) and) and neuroblastoma (IMR32, Kelly, SKNFI) cancer cell lines and non-cancerous foreskin fibroblasts(VH-10, BjhTERT). We found cancer-specific synergistic drug interactions between nedisertib and OXC-101. Combined treatment of nedisertib and OXC-101 to H460 and MP46 increased expression of s10H3 (mitotic marker) and the apoptosis marker (cPARP) compared with single treatment. However, there was no additional increase in expression of the DNA damage markerγH2AX with combined treatment. We also performed annexin V staining by FACS on MP38 andMP48 cells and observed a significant increase in the apoptotic population with combination treatment compared with single treatment. Imaging live cells, we observed a significant delay or arrest in the mitotic phase followed by death of cancer cells in mitosis in response to combination treatment, whereas cells treated individually with nedisertib or OXC-101 continued to proliferate and progress to the next phase of the cell cycle. These data suggest that the DNA-PK inhibitor may enhance the cytotoxic effect of OXC-101specifically in cancer cells. In addition, we will conduct an in-depth mechanistic study of how depletion/inhibition of DNA-PK enhances the cytotoxicity of OXC-101 and validate the drug combination in an appropriate preclinical mouse model. Citation Format: Akhilesh Nagesh Danda, Helge Gad, Martin Scobie, Laura Martínez-López, Nuria Pastor Carrillo, Manuel Luis Orta, Thomas Helleday, Ulrika warpman berglund, Kumar Sanjiv. DNA-PK inhibition augment the cancer specific cytotoxicity of mitotic MTH1 inhibitor OXC-101 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6204.