Pyrrolo-1,5-benzoxazepines induce apoptosis in chronic myelogenous leukemia (CML) cells by bypassing the apoptotic suppressor bcr-abl.
Expression of the transforming oncogene bcr-abl in chronic myelogenous leukemia (CML) cells is reported to confer resistance against apoptosis induced by many chemotherapeutic agents such as etoposide, ara-C, and staurosporine. In the present study some members of a series of novel pyrrolo-1,5-benzoxazepines potently induce apoptosis, as shown by cell shrinkage, chromatin condensation, DNA fragmentation, and poly(ADP-ribose) polymerase (PARP) cleavage, in three CML cell lines, K562, KYO.1, and LAMA 84. Induction of apoptosis by a representative member of this series, PBOX-6, was not accompanied by either the down-regulation of Bcr-Abl or by the attenuation of its protein tyrosine kinase activity up to 24 h after treatment, when approximately 50% of the cells had undergone apoptosis. These results suggest that down-regulation of Bcr-Abl is not part of the upstream apoptotic death program activated by PBOX-6. By characterizing the mechanism in which this novel agent executes apoptosis, this study has revealed that PBOX-6 caused activation of caspase 3-like proteases in only two of the three CML cell lines. In addition, inhibition of caspase 3-like protease activity using the inhibitor z-DEVD-fmk blocked caspase 3-like protease activity but did not prevent the induction of apoptosis, suggesting that caspase 3-like proteases are not essential in the mechanism by which PBOX-6 induces apoptosis in CML cells. In conclusion, this study demonstrates that PBOX-6 can bypass Bcr-Abl-mediated suppression of apoptosis, suggesting an important potential use of these compounds in the treatment of CML.
Mc Gee
M M
MM
Department of Biochemistry, Trinity College, Dublin, Ireland.
Campiani
G
G
Ramunno
A
A
Fattorusso
C
C
Nacci
V
V
Lawler
M
M
Williams
D C
DC
Zisterer
D M
DM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D016044:Fusion Proteins, bcr-abl; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000502:physiology*; D010077:Oxazepines / Q000494:pharmacology*; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D015514:Oncogene Proteins, Fusion; D010077:Oxazepines; D011758:Pyrroles; D017382:Reactive Oxygen Species; C406060:abl-bcr fusion protein, human; D011065:Poly(ADP-ribose) Polymerases; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C418868:PBOX-6