BTK and B-cell chronic lymphocytic leukemia: Using a variety of techniques, several other groups have demonstrated that UM-CLL has higher BCR activity than M-CLL in vitro [24–27] that are consistent with our findings showing phosphorylation levels of BTK, PLCγ2, AKT and ERK are uniformly higher in UM-CLL than M-CLL (Figures 5 and 6).