SMAD4 and breast cancer: Heavily implicated genes include KRAS (v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog ) [2], [3], TP53 (tumor protein p53) [4], [5], SMAD4/DPC4 (SMAD family member 4/deletion target in pancreatic carcinoma 4 homolog) [6], [7], CDKN2A (cyclin-dependent kinase inhibitor 2A; p16) [8], [9], [10], and BRCA2 (breast cancer 2, early onset) [11], [12].