CDK4 and lymphoma: Since Δ3C virus-infected lymphomas continue to proliferate (albeit more slowly) in the presence of high-level p16, we also compared expression of specific cellular genes involved in activating cell cycle progression in the Δ3C-induced versus WT-induced tumors, including cyclin E, CDK4, CDK6, cyclins D1, D2, and D3, c-Myc, E2F1, and cyclin A (Fig 9D).