Since p18−/− luminal tumor cells proliferate very slowly in vitro and weakly generate luminal tumors when transplanted in vivo [32], we utilized a few Gata3+/+;Brca1+/+ luminal tumor cell lines isolated from MMTV-PyMT mammary tumors (Fig. 3e) (this study and reference [31]). Here, BRCA1 is linked to neoplasm.