CDK4 and mantle cell lymphoma: In MCL and MM with the translocation the control of G1-S transition is further impaired by the increased activity of the CDK2-cyclin E complex related to the CDK4-cyclin D1 dependent sequestration of its inhibitor p27kip and by the frequent presence of CDK4 amplification and p16INK4 inactivation [4, 8, 36].