ZAP-70 expression and proliferative activity in chronic lymphocytic leukemia

The expression of 70 kDa protein zeta-associated protein (ZAP-70) in chronic lymphocytic leukemia (CLL) has been used to detect those patients with more aggressive disease. The aim of this study was to determine the proliferative activity of ZAP-70(+) leukemic cells by immunocytochemical methods. The study was undertaken on native blood marrow (BM) and peripheral blood (PB) smears from 65 patients with CLL. ZAP-70 was expressed in leukemic cells of 35 patients (54%). We demonstrated that ZAP-70 immunoreactivity correlated with Rai 0-IV (p = 0.002) and Binet A-C stages (p < 0.001), total tumor mass (TTM score) (p < 0.001), β2-microglobulin (p = 0.006), atypical lymphocytes (p < 0.001) and proliferative activity in bone marrow and peripheral blood (p = 0.014, p = 0.002, respectively) using χ(2) test and Mann-Whitney test. ZAP-70 protein expression is in direct correlation with the poorer prognostic parameters, which additionally confirms the successful method of detection of ZAP-70 expression. Higher Ki-67 expression in BM and PB smears of patients with ZAP-70(+) disease indicates higher proliferating compartments, which may contribute to poorer prognosis.