By contrast SHP-1, a tyrosine phosphatase that participates in signaling pathways regulating proliferation, survival and apoptosis of both hematopoietic and non-hematopoietic cells (18), is expressed in CLL cells at levels comparable to normal B cells (60) but is functionally dysregulated by mechanisms that are mediated by the Src family kinase Lyn (26), making this phosphatase an interesting target for activating-drug discovery. Here, LYN is linked to B-cell chronic lymphocytic leukemia.