ZAP70 and B-cell chronic lymphocytic leukemia: ZAP-70+ CLL cells tend to localize to the nodes and this is associated with more aggressive disease.3 One of the most important signals from the microenvironment for cell survival is BCR activation.5,23,24 Upon activation of the BCR, the tyrosine kinase Lyn phosphorylates and activates Syk, leading to activation of downstream signaling pathways such as Akt, MAPK, and NF-κB, upregulation of anti-apoptotic proteins such as Mcl-1, and inactivation of pro-apoptotic protein BIM.