TP53 and breast cancer: The important protein defects that have been reported include breast cancer gene (BRCA1/2) dysfunction [6], tumor protein 53 (TP53) inactivation [7,8], malfunction of the ataxia telangiectasia mutated (ATM) protein [9,10], or constitutive activity of the mitogen-activated protein kinase (MAPK) pathways [11,12].