BCR and B-cell chronic lymphocytic leukemia: BTK is required for B-cell receptor (BCR) signaling and implicated in the development of the B-cell malignancies including chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL) and acute lymphocytic leukemia (ALL)[3,4].