Comparison of Bcl-2, CD38 and ZAP-70 Expression in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) was previously considered a uniform disease characterized by autonomous over-expression of bcl-2. Recently the pathogenic role of bcl-2 has been questioned and attention has turned to prognostic subtypes of CLL differing in CD38 and ZAP-70 expression. However, the relationship between bcl-2 and CD38 or ZAP-70 expression remains uncertain and was investigated using flow cytometric immunophenotyping of 50 CLL specimens. CLL cells were consistently bcl-2 positive but varied in expression level: mean fluorescence intensity (MFI) 45-152. Although there was no significant difference in bcl-2 expression between CD38 or ZAP-70 positive and negative specimens, an inverse correlation was identified between percentage of CD38 positive B-cells and bcl-2 MFI when all (p<0.03, r²=0.10) and peripheral blood (p<0.004, r²=0.27) samples were analyzed. While bcl-2 levels do not appear to be a major discriminator between indolent and more aggressive subtypes of CLL, CD38 and bcl-2 expression appear to be interrelated.