The cell cycle inhibitors CDKN1B, cyclin-dependent kinase inhibitor 1B (p27Kip1), and CDKN2A, coding for p16INK4a, an inhibitor of cell cycle, as well as p14arf, the negative regulator of MDM2, were found mutated in CLL [12]. This evidence concerns the gene CDKN1B and B-cell chronic lymphocytic leukemia.