We thus investigated whether PD-0332991 also inhibits E2F1 expression in BT-549 breast cancer cells, which has high expression of endogenous HOXB9 and E2F1, compare to the control (MCF7 cells), (Figure 5 A,B) and whether this treatment would affect HOXB9 expression. Here, E2F1 is linked to breast carcinoma.