RB1 and breast cancer: As shown in Figure 7A and 7B, E2F8 levels in 10 freshly collected breast cancer samples were significantly positively correlated with levels of cyclin E1 (r = 0.723, P = 0.018), cyclin E2 (r = 0.803, P = 0.005), and phosphorylation level of Rb (r = 0.639, P = 0.047).