Despite appearing to be major contributors to the induction of senescence, p53, p21Cip1 and p16INK4 are not absolutely required for doxorubicin-induced senescence [37], which has been reported in a wide variety of tumor cell lines (reviewed in [32] and [134]), of which we provide a few examples (Table 1). This evidence concerns the gene CDKN1A and neoplasm.