CHEK1 and vulva cancer: For example, targeting CHK1 significantly enhances cell killing effect by chemotherapy or radiation therapy in ovarian, triple negative breast, and brain cancers.9 In vitro targeting of CHK1 by inhibitor or siRNA in vulvar cancer cell lines CAL39 and SW954, both harboring p53 mutations,39 leads to a significant reduction in viability which is in line with observation in other cancer types.