Gene therapy in pancreatic cancer

Figure 1 Cell cycle checkpoints. Mitogenic signals activate cyclin D-dependent kinases, which phosphorylate RB and RB family proteins (p107 and p130) to facilitate entry into S phase. The p16INK4a protein inhibits cyclin D/Cdk4, 6 to activate RB and prevent entry into S phase. The p14ARF protein inhibits Mdm2 to induce p53, leading either to p53-dependent apoptosis or to induction of the Cdk2 inhibitor p21Cip1. The p21Cip1 protein inhibits cyclin E/Cdk2 and induces RB-dependent cell cycle arrest.