LCK and B-cell chronic lymphocytic leukemia: LCK was overexpressed and constitutively activated in the anergic CLL cells from TCL1 Nfat2+/+ mice, while leukaemic cells from TCL1 Nfat2−/− mice showed no evidence of LCK activation upon αIgM treatment as assessed by the absence of the activating phosphorylation at Tyr-394.