CASP3 and cancer: Another explanation for the different effects in cancer and non-cancer cells could be the localization of p21: it is well-known that cytoplasmic localization of p21 leads to an inhibition of Caspase 3 activation and thus to reduced apoptosis induction, and that p21 has a dual role as oncogene or tumor suppressor gene dependent on its localization [37, 39, 40].