Evaluation of Apaf-1 and procaspases-2, -3, -7, -8, and -9 as potential prognostic markers in acute leukemia

Recent studies have suggested that variations in levels of caspases, a family of intracellular cysteine proteases, can profoundly affect the ability of cells to undergo apoptosis. In this study, immunoblotting was used to examine levels of apoptotic protease activating factor-1 (Apaf-1) and procaspases-2, -3, -7, -8, and -9 in bone marrow samples (at least 80% leukemia) harvested before chemotherapy from adults with newly diagnosed acute myelogenous leukemia (AML, 42 patients) and acute lymphocytic leukemia (ALL, 18 patients). Levels of each of these polypeptides varied over a more than 10-fold range between specimens. In AML samples, expression of procaspase-2 correlated with levels of Apaf-1 (Rs = 0.52, P < .02), procaspase-3 (Rs = 0.56,P < .006) and procaspase-8 (Rs = 0.64, P < .002). In ALL samples, expression of procaspases-7 and -9 was highly correlated (Rs = 0.90,P < .003). Levels of these polypeptides did not correlate with prognostic factors or response to induction chemotherapy. In further studies, 16 paired samples (13 AML, 3 ALL), the first harvested before induction therapy and the second harvested at the time of leukemia regrowth, were also examined. There were no systematic alterations in levels of Apaf-1 or procaspases at relapse compared with diagnosis. These results indicate that levels of initiator caspases vary widely among different leukemia specimens but cast doubt on the hypothesis that this variation is a major determinant of drug sensitivity for acute leukemia in the clinical setting.