Paradoxically, there is now evidence that cell cycle re-entry (reversal of the proliferation arrested state of senescent cancer cells) can be accelerated by ectopic expression of caspase 3 or treatment with apoptosis-triggering anticancer drugs such as camptothecin and the BCL2 inhibitor ABT-737, and that this re-entry produces aggressive variants [65]. Here, CASP3 is linked to cancer.