CDKN1A and neoplasm: Caspase-2 is required for DNA damage-induced expression of the cyclin-dependent kinase inhibitor 1 (CDK) inhibitor p21 (WAF1/CIP1) which acts as an inhibitor of apoptosis in a number of systems to mediate tumor-suppressive functions [237,238], whereas PIDDosome independent and dependent caspase-2 activation was found to be important for DNA-damage-induced apoptosis [24,79,80].