BTK and B-cell chronic lymphocytic leukemia: A greater BCR-signaling capacity was further demonstrated in circulating B-CLL cells from UGT2B17HI patients using pBTK-Y223 protein as a biomarker, showing a greater pBTK/BTK signal (by 1.5-fold; p = 0.037) compared to UGT2B17LOW patients (Figure 1D).