MDM2 and neoplasm: p16INK4A and p15INK4B bind to CDK4/6 to induce cell cycle arrest via retinoblastoma protein, whereas p14ARF/19ARF arrests the cell cycle by stabilizing p53, trapping MDM2, and increasing expression of p21WAF1, an important cell cycle inhibitor and tumor suppressor for many cancers including those of the colon.