CGP57148B (STI-571) induces differentiation and apoptosis and sensitizes Bcr-Abl-positive human leukemia cells to apoptosis due to antileukemic drugs.
The differentiation and apoptosis-sensitizing effects of the Bcr-Abl-specific tyrosine kinase inhibitor CGP57148B, also known as STI-571, were determined in human Bcr-Abl-positive HL-60/Bcr-Abl and K562 cells. First, the results demonstrate that the ectopic expression of the p185 Bcr-Abl fusion protein induced hemoglobin in the acute myeloid leukemia (AML) HL-60 cells. Exposure to low-dose cytosine arabinoside (Ara-C; 10 nmol/L) increased hemoglobin levels in HL-60/Bcr-Abl and in the chronic myeloid leukemia (CML) blast crisis K562 cells, which express the p210 Bcr-Abl protein. As compared with HL-60/neo, HL-60/Bcr-Abl and K562 cells were resistant to apoptosis induced by Ara-C, doxorubicin, or tumor necrosis factor-alpha (TNF-alpha), which was associated with reduced processing of caspase-8 and Bid protein and decreased cytosolic accumulation of cytochrome c (cyt c). Exposure to CGP57148B alone increased hemoglobin levels and CD11b expression and induced apoptosis of HL-60/Bcr-Abl and K562 cells. CGP57148B treatment down-regulated antiapoptotic XIAP, cIAP1, and Bcl-x(L), without affecting Bcl-2, Bax, Apaf-1, Fas (CD95), Fas ligand, Abl, and Bcr-Abl levels. CGP57148B also inhibited constitutively active Akt kinase and NFkappaB in Bcr-Abl-positive cells. Attenuation of NFkappaB activity by ectopic expression of transdominant repressor of IkappaB sensitized HL-60/Bcr-Abl and K562 cells to TNF-alpha but not to apoptosis induced by Ara-C or doxorubicin. Importantly, cotreatment with CGP57148B significantly increased Ara-C- or doxorubicin-induced apoptosis of HL-60/Bcr-Abl and K562 cells. This was associated with greater cytosolic accumulation of cyt c and PARP cleavage activity of caspase-3. These in vitro data indicate that combinations of CGP57148B and antileukemic drugs such as Ara-C may have improved in vivo efficacy against Bcr-Abl-positive acute leukemia.
Fang
G
G
H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, FL, USA.
Kim
C N
CN
Perkins
C L
CL
Ramadevi
N
N
Winton
E
E
Wittmann
S
S
Bhalla
K N
KN
D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides; D002454:Cell Differentiation / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D016044:Fusion Proteins, bcr-abl; D018922:HL-60 Cells; D006801:Humans; D000068877:Imatinib Mesylate; D020014:K562 Cells; D007938:Leukemia / Q000188:drug therapy / Q000473:pathology*; D010879:Piperazines / Q000494:pharmacology* / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology* / Q000627:therapeutic use
D000970:Antineoplastic Agents; D001549:Benzamides; D004791:Enzyme Inhibitors; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl