RB1 and neoplasm: In keeping, in vitro under appropriate conditions CCND1 promotes proliferation and migration of BTSC (Figs. 4a–c, 5a and 9a), and is modulated by miR-449a expression, i.e., is higher in Pten/p53 mBTSC (miR-449alow) than in Rb/p53 mBTSC (miR-449ahigh) (Figs. 4c and 5a) and in miR-449ahigh experimental tumours, Ccnd1 is downregulated (Fig. 6t).