A. NTC and BRCA1-kd SKOV-3 cells were treated with various concentrations of olaparib, triapine, or both agents in combination at a constant ratio (olaparib: triapine=13:1). Clonogenic survival and CI values were determined. B. SKOV-3, C. BG-1, and D. PEO4 cells were treated with various concentrations of olaparib in combination with fixed concentrations of triapine as indicated. Clonogenic survival of cells treated with triapine alone is shown in bar graphs (right). Data are means ± SD. *, CI<1.