CDKN1B and B-cell chronic lymphocytic leukemia: Our previous data [22] indicated that expression of the CTLA-4 molecule in CLL cells correlated with the expression of the G0/G1 phase regulators cyclins D2 and D3, and p27KIP1, suggesting the impact of CTLA-4 on prolonging the G1 phase in leukaemic lymphocytes.