Our studies show that CHEK2 is a critical SF3B1 target, as ectopic expression of CHEK2 demonstrates high synergy of SF3B1 inhibitors with CHEK2 inhibitors as well as chemotherapeutic drugs, and propose that the SF3B1 inhibitor E7107 is a lead compound that sensitizes cancer cells to chemotherapy. Here, CHEK2 is linked to cancer.