RB1 and breast cancer: Interestingly, the basal-like/mesenchymal molecular features of MCF-7/PRLRKO tumors are also reminiscent of mammary tumors generated by the loss of function of several tumor suppressors such as BRCA1 gene44,45, BRCA1 and TP53 (refs. 46–48), and TP53 and RB1 (ref. 49).