BTK and B-cell chronic lymphocytic leukemia: Moreover, inhibition of heterotrimeric G-protein-mediated signaling by PTx also resulted in BTK blockade, whereas JAK2 activation was unaffected (Figure 6A, 6B and 6D), suggesting that, as in normal cells, also in CLL B-lymphocytes CXCR4 signaling manifests concurrency between JAK2- and heterotrimeric G-proteins, both converging on BTK activation.