EXPRESSION OF BCL-2 PROTOONCOGENE IN ADULT ACUTE LYMPHOBLASTIC-LEUKEMIA

The products of the BCL-2 gene prolong survival of lymphohematopoietic cells by inhibition of programmed cell death. We studied bcl-2 protei n expression in a series of 43 adult acute lymphoblastic leukemia (ALL ) at diagnosis, using a specific monoclonal antibody and flow cytometr y. All samples expressed bcl-2 with a mean percentage of positive cell s of 77.9. The level of bcl-2 in positive cells expressed as mean equi valent of soluble fluorescence (MESF) was highly variable ranging from 5 x 10(3) to 552 x 10(3) (mean +/- s.d.: 96.5 +/- 109 x 10(3)). Neith er the percentage of positive cells nor bcl-2 MESF levels were correla ted with initial characteristics including blood counts, immunological phenotype, or cytogenetics. The survival of leukemic cells maintained in cytokine-free liquid culture was not correlated with bcl-2 express ion. However, cells from ALL with higher white blood cell (WBC) counts , with t(9;22) translocation, or expressing myeloid surface antigens e xhibited significantly longer survival in this culture system. The out come after intensive chemotherapy did not differ according to bcl-2 ex pression. Factors associated with poor outcome included WBC counts, pr esence of t(9;22) translocation, presence of myeloid antigens and prol onged survival of cultured cells. These results indicate that high lev els of bcl-2 are not associated with distinct clinical or biological c haracteristics in ALL.