Expression of bcl-2 by human bone marrow mast cells and its overexpressionin mast cell leukemia

Bcl-2 protein plays a major role in the prevention of programmed cell death of differentiating cells. In the present study, the expression of cytoplas mic bcl-2 by human Bone Marrow Mast Cells (BMMC) from both normal and patho logical bone marrow samples was examined. A total of 35 subjects correspond ing to 9 healthy volunteers, 8 cases of adult indolent systemic mast cell d isease (SMCD), 4 cases of pediatric mastocytosis (PM), 11 cases of hematolo gical malignancies (HM), 2 cases of reactive bone marrow, and 1 case of mas t cell leukemia (MCL) were analyzed. The expression of bcl-2 was studied us ing quantitative three-color flow cytometry, We also studied the molecular configuration of the bcl-2 gene and other relatives by Southern blot and po lymerase chain reaction (PCR) in the MCL case. Bcl-2 expression was detecte d in BMMC from all samples analyzed. No significant differences on the expr ession of bcl-2 were detected between BMMC from healthy subjects and patien ts with SMCD, PM, HM, and reactive bone marrow. By contrast, bcl-2 protein was overexpressed in BMMC from MCL patient without gene rearrangement. Our results show that bcl-2 protein was constitutively expressed by BMMC, BMMC from MCL display overexpression of bcl-2, which could not be related to mol ecular rearrangements involving the bcl-2 gene. The expression of this prot ein by mature MC may play a role in the prevention of MC apoptosis and thus help to explain the long survival of these cells. The overexpression of bc l-2 by BMMC in MCL may help to explain their resistance to chemotherapy-ind uced apoptosis. Am. J, Hematol. 60:191-195, 1999, (C) 1999 Wiley-Liss, Inc.