Liposomal Bcl-2 antisense oligonucleotides enhance proliferation, sensitize acute myeloid leukemia to cytosine-arabinoside, and induce apoptosis independent of other antiapoptotic proteins.
The antiapoptotic proteins, Bcl-2 and Bcl-X(L), are expressed in most cases of acute myeloid leukemia (AML) and may contribute to drug resistance in AML. We tested the hypothesis that down-regulation of Bcl-2 alone by antisense oligodeoxynucleotides (Bcl-2-AS) induces apoptosis, even in the presence of other antiapoptotic genes. We tested Bcl-2-AS in myeloid leukemic HL-60 cells, in Bcl-2 and Bcl-X(L) overexpressing HL-60-DOX cells, and in primary AML samples. Down-regulation of Bcl-2 by Bcl-2-AS reduced the viability of HL-60 cells and, less effectively, HL-60-DOX cells and increased ara-C cytotoxicity in both cell lines. Incubation of primary AML blasts with Bcl-2-AS decreased Bcl-2 expression in CD34(+) blast cells after induction of apoptosis and enhancement of ara-C cytotoxicity in 11 of 19 primary AML samples. In 8 samples in which Bcl-2-AS did not induce apoptosis, baseline Bcl-2 levels were found to be strikingly high. The expression of other antiapoptotic proteins (Bcl-X(L), Bag-1, A1, and Mcl-1) did not prevent Bcl-2-AS-induced apoptosis. Bcl-2-AS also inhibited colony formation of AML progenitor cells. Low concentrations of Bcl-2-AS induced significant increases in S-phase cells (P =.04). Results establish Bcl-2 as a critical target for AS strategies in AML in which the baseline levels predict response to Bcl-2-AS. Bcl-2 exerts both antiapoptotic and antiproliferative functions in AML. Because early normal hematopoietic stem cells do not express Bcl-2, Bcl-2-AS therapy should be highly selective for AML cells. (Blood. 2000;95:3929-3938)
Konopleva
M
M
The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Tari
A M
AM
Estrov
Z
Z
Harris
D
D
Xie
Z
Z
Zhao
S
S
López-Berestein
G
G
Andreeff
M
M
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003561:Cytarabine / Q000633:toxicity*; D005260:Female; D019254:Genes, bcl-2; D018922:HL-60 Cells; D006801:Humans; D007951:Leukemia, Myeloid; D008081:Liposomes; D008297:Male; D008875:Middle Aged; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014407:Tumor Cells, Cultured
D008081:Liposomes; D020319:Oligodeoxyribonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D003561:Cytarabine