Furthermore, tumors from both genotypes displayed high but comparable rates of mitosis and similar rates of tumor growth (Fig. 2c and data not shown), demonstrating that the rate of proliferation was similar for Wap-p53R172H; Rb1+/+ and Wap-p53R172H; Rb1ΔL/ΔL tumors. This evidence concerns the gene RB1 and neoplasm.