PMAIP1 and neoplasm: Interestingly, while the tumor suppressive role of p53 remains a cornerstone, a series of studies using models defective for the activation of cell cycle inhibitors and proapoptotic mediators p21, PUMA and Noxa [19,20] demonstrated that the ability of p53 to act as a tumor suppressor does not rely on its ability to induce cell cycle arrest, senescence and/or apoptosis.