TP53 and cancer: We then examined the effect of conventional cancer treatment genotoxic agents, etoposide (topoisomerase II inhibitor) or 5FU (5′ fluorouracil; irreversible inhibitor of thymidylate synthase), which would inhibit the DNA chain elongation process, for cell death-inducing effect of Cdc7 siRNA or a Cdc7 inhibitor in p53-positive and -negative HCT116 cells.