RT Journal Article SR Electronic T1 DNA-PK and ATM promote cell survival in response to NK314, a topoisomerase IIα inhibitor JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP mol.109.057125 DO 10.1124/mol.109.057125 A1 Lei Guo A1 Xiaojun Liu A1 Yingjun Jiang A1 Kiyohiro Nishikawa A1 William Plunkett YR 2011 UL http://molpharm.aspetjournals.org/content/early/2011/05/05/mol.109.057125.abstract AB NK314 is a benzo[c]phenanthridine alkaloid that inhibits topoisomerase IIα, leading to the generation of DNA double-strand breaks (DSBs) and activating the G2 checkpoint pathway. The purpose of the present studies was to investigate the DNA intercalating properties of NK314, to evaluate the DNA repair mechanisms activated in cells that may lead to resistance to NK314, and to develop mechanism-based combination strategies to maximize the antitumor effect of the compound. A DNA unwinding assay indicated that NK314 intercalates in DNA a property that likely cooperates with its ability to trap topoisomerase IIα in its cleavage complex form. The consequence of this is the formation of DNA DSBs, as demonstrated by pulsed-field gel electrophoresis and H2AX phosphorylation. Clonogenic assays demonstrated a significant sensitization in NK314-treated cells deficient in DNA-PKcs, Ku80, ATM, BRCA2, or XRCC3, compared with wild-type cells, indicating that both non-homologous end-joining (NHEJ) and homologous recombination (HR) DNA repair pathways contribute to cell survival. Furthermore, both the DNA-PK inhibitor, NU7441 and the ATM inhibitor, KU55933 significantly sensitized cells to NK314. We conclude that DNA-PK and ATM contribute to cell survival in response to NK314, and could be potential targets for abrogating resistance and maximizing the anti-tumor effect of NK314.