The validity of this hypothesis remains unclear, because although both CHK2 siRNA knock-down experiments and CHK2 inhibition by the small molecule inhibitor PV1019 showed potentiation of the cytotoxicity of topotecan and campothecan in ovarian cancer cell lines [17], no such effects have been observed with the inhibitors VRX0466617 (2) [22] and CCT241533 (3) [23], [26] (Figure 1) in combination with genotoxic agents. The gene discussed is CHEK2; the disease is ovarian cancer.