We cultured cells derived from three individual p18−/−; Brca1MGKO tumors and found that E2 treatment in both type 1 and type 2 tumor cells enhanced the number of cells (Fig. 6b, Additional file 8: Figure S8C), promoted phosphorylation of RB (Fig. 4c), and stimulated incorporation of BrdU in cells (Fig. 4d). This evidence concerns the gene RB1 and neoplasm.