Importantly, all these cell lines carry defective INK4-RB pathway (undetectable p16 in T47D, MCF7, MDA-MB231, BT20, SUM149, and undetectable RB in HCC1937) [62–64], which are similar with our p18−/−, p18−/−;Brca1MGKO, and p16−/−;Brca1MGKO mouse tumor cell system. Here, RB1 is linked to neoplasm.