RB1 and neoplasm: As shown in Figure 2A, we observed that only ∼19% and ∼9% of Brg1-negative tumor cells were also positive for pRb1S780 and/or pRb1T821/826, respectively, by dual IF; in other words, ∼80% and ∼90% of Brg1-negative cells failed to express either pRb1S780 or pRb1T821/826 and also harbor hypophosphorylated or activated Rb1, which should inhibit growth.