RB1 and cancer: Figure 2a shows a schematic representation of the main effects of E6 and E7 on cell cycle control proteins in HPV-transformed cells. Both HPV16 oncoproteins E6 and E7 were detected (Figure 2b), as well as the expected effects on the analyzed downstream proteins, namely p53 for E6 and p16 for E7 and p21 as an element of both p53 and pRb signaling cascades. All of the proteins tested for show expression levels as observed and expected in HPV-positive cancer cells, which are downregulation of p53, upregulation of p16, and downregulation of p21 (Figure 2c).