MEASUREMENT OF SPONTANEOUS AND THERAPEUTIC AGENT-INDUCED APOPTOSIS WITH BCL-2 PROTEIN EXPRESSION IN ACUTE MYELOID-LEUKEMIA

We have designed in vitro assays to investigate the possible associati on between apoptosis and chemotherapeutic sensitivity in acute myeloid leukemias (AMLs). Consistent low levels of spontaneous apoptosis were observed in myeloid cells from normal bone marrow samples, while untr eated cells collected from 56 de novo AML patients showed variable apo ptosis. Control myeloid cells showed increased apoptosis after in vitr o treatments with daunomycin (DNR), cytosine arabinoside (ARA-C), or g amma irradiation (RAD). Most AML samples showed less treatment-associa ted apoptosis, suggesting that apoptosis responses to therapeutic agen ts may be frequently attenuated in AML. Certain cytogenetic abnormalit ies common in AML may affect apoptosis, as acute promyelocytic leukemi a (APL) samples with t(15;17) karyotypes showed consistently low level s of spontaneous and treatment-associated apoptosis. Apoptosis assays may provide unique functional subtyping of AMLs, as other common cytog enetic subsets showed variable apoptosis. Altered function of two well -characterized regulators of apoptosis, BCL-2 and p53, was not entirel y responsible for this variability. A genomic p53 mutation was found i n only one AML sample. All samples that demonstrated the highest BCL-2 -positive cell fractions showed low apoptosis, but reduced apoptosis w as seen in both the presence and absence of BCL-2 overexpression. Fina lly, data from matched diagnosis and relapse sample pairs suggest that neither further reduced apoptosis nor additional BCL-2 overexpression is necessarily associated with disease progression. (C) 1997 by The A merican Society of Hematology.