Expression of apoptosis-controlling proteins in acute leukemia cells

The expression of Bcl-2 family proteins (Bcl-2, Bcl-X, Bcl-X-L, Bcl-X-s, BA X, BAD, MCL-1) and of Interleukin-1 converting enzyme (ICE)-related protein s (ICE, CPP32, ICH-1) was analyzed in acute leukemia cells by flow cytometr y, Most proteins studied were detectable in cell lines such as KG1a, HL60, K562 (myeloblastic), REH, RAJI and MOLT4 (lymphoblastic) and VAL (B-cell ly mphoma), However, BCL-X-s and BAK were weakly expressed in K562, as were Bc l-X, BAD and BAK in the VAL line. In acute myeloid leukemia (66 cases studi ed), the proteins were expressed in most cases in a high percentage of cell s, especially BAX and CPP32, without correlation with hematological charact eristics. However, Bcl-2 was expressed in a higher percentage of cells in F AB M1 and M5 cases, and in CD34-positive cases, whereas Bcl-X-s was more fr equently expressed in M3 cases. No differences were observed regarding fluo rescence intensity. Higher percentages of Bcl-2-positive cells were associa ted with low remission rate, while expression of Bcl-X-s was predictive of high remission rate. In acute lymphoblastic leukemia (36 cases), all protei ns studied were expressed in a majority of cases. Bcl-X-s was more frequent ly detected in T-cell type, and was also associated with a higher remission rate. These results suggest that apoptosis-controlling proteins may have a role in the pathogenesis and response to therapy of acute leukemia.