Correlation between ZAP-70, phospho-ZAP-70, and phospho-Syk expression in leukemic cells from patients with CLL.

For patients with chronic lymphocytic leukemia (CLL), expression of ZAP-70 in the leukemic cells is an indicator of poor prognosis. However, the mechanism that accounts for this effect is not known. ZAP-70 expression has previously been associated with increased B cell antigen receptor signaling upon surface immunoglobulin ligation in vitro as shown by ZAP-70 and Syk phosphorylation.