BCL-2 IMMUNOHISTOCHEMICAL EVALUATION IN B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA AND HAIRY-CELL LEUKEMIA BEFORE TREATMENT WITH FLUDARABINE AND 2-CHLORO-DEOXY-ADENOSINE

Bcl-2 overexpression has been shown to be associated with several mali gnancies, including B-cell chronic lymphocytic leukemia (CLL) and non- Hodgkin's lymphomas (NHL), mainly low-grade and follicular in type. It has as yet not been described in hairy cell leukemia (HCL). In 30 pat ients with CLL and 14 with HCL who were consecutively selected for tre atment with purine analogues (Fludarabine in CLL and 2-chloro-deoxy-ad enosine in HCL), we evaluated bcl-2 oncoprotein expression in leukemic cells on marrow sections that were taken before treatment and stained immunohistochemically with a monoclonal antibody (Dakopatts 124 clone ), by the avidin-biotin-peroxidase method. All samples were found to b e bcl-2 positive, with a staining intensity that was moderate to stron g in CLL and weak to moderate in HCL. 83% of CLL and 100% of HCL patie nts were responsive to purine analogues. These findings show that bcl- 2 is overexpressed in almost all cases CLL and HCL and that bcl-2 over expression does not predict a poor response to purine analogues, which are believed to induce apoptosis.