The necessity of APEX1 for cellular survival and its frequent overexpression in tumor cells strongly suggest a fundamental role of this protein in preventing cell death and in controlling cellular proliferation [48], probably through its regulatory role in the expression of cyclin-dependent kinase inhibitor p21 (CDKN1A) [44] and in the DNA binding activity of the p53 protein [7]. The gene discussed is TP53; the disease is neoplasm.