CASP3 and leukemia: Although tubulin inhibitors and Top2 inhibitors are widely used in combination in the clinic and some combinations have been shown to mutually potentiate the activities in leukemia and solid tumor cells [40], VP-16 was reported to decrease the activation of caspase-3 and the induction of apoptotic cell death by colchicine (a tubulin inhibitor though not used as an anticancer drug in the clinic) in HEp-2 cells [11, 12].