CCND1 and breast cancer: MCL1 has a similar role as a BCL2 family apoptosis inhibitor protein [41], while TGFβ1 is a key cytokine involved in drug-resistance by regulating stemness, epithelial-mesenchymal transition (EMT) angiogenesis, and apoptosis [42,43] The fourth gene, cyclin D1, is one of the cell proliferation cyclins [44] and it has been selected for further analysis because of its prognostic significance in breast cancer patients [45,46].