Selective induction of apoptosis by the pyrrolo-1,5-benzoxazepine 7-[[dimethylcarbamoyl]oxy]-6-(2-naphthyl)pyrrolo-[2,1-d] (1,5)-benzoxazepine (PBOX-6) in Leukemia cells occurs via the c-Jun NH2-terminal kinase-dependent phosphorylation and inactivation of Bcl-2 and Bcl-XL.
Overexpression of the Bcl-2 proto-oncogene in tumor cells confers resistance against chemotherapeutic drugs. In this study, we describe how the novel pyrrolo-1,5-benzoxazepine compound 7-[[dimethylcarbamoyl]oxy]-6-(2-naphthyl)pyrrolo-[2,1-d] (1,5)-benzoxazepine (PBOX-6) selectively induces apoptosis in Bcl-2-overexpressing cancer cells, whereas it shows no cytotoxic effect on normal peripheral blood mononuclear cells. PBOX-6 overcomes Bcl-2-mediated resistance to apoptosis in chronic myelogenous leukemia (CML) K562 cells by the time- and dose-dependent phosphorylation and inactivation of antiapoptotic Bcl-2 family members Bcl-2 and Bcl-XL. PBOX-6 also induces Bcl-2 phosphorylation and apoptosis in wild-type T leukemia CEM cells and cells overexpressing Bcl-2. This is in contrast to chemotherapeutic agents such as etoposide, actinomycin D, and ultraviolet irradiation, whereby overexpression of Bcl-2 confers resistance against apoptosis. In addition, PBOX-6 induces Bcl-2 phosphorylation and apoptosis in wild-type Jurkat acute lymphoblastic leukemia cells and cells overexpressing Bcl-2. However, Jurkat cells containing a Bcl-2 triple mutant, whereby the principal Bcl-2 phosphorylation sites are mutated to alanine, demonstrate resistance against Bcl-2 phosphorylation and apoptosis. PBOX-6 also induces the early and transient activation of c-Jun NH2-terminal kinase (JNK) in CEM cells. Inhibition of JNK activity prevents Bcl-2 phosphorylation and apoptosis, implicating JNK in the upstream signaling pathway leading to Bcl-2 phosphorylation. Collectively, these findings identify Bcl-2 phosphorylation and inactivation as a critical step in the apoptotic pathway induced by PBOX-6 and highlight its potential as an effective antileukemic agent.
Mc Gee
Margaret M
MM
Department of Biochemistry, Trinity College, Dublin 2, Ireland.
Greene
Lisa M
LM
Ledwidge
Susan
S
Campiani
Giuseppe
G
Nacci
Vito
V
Lawler
Mark
M
Williams
D Clive
DC
Zisterer
Daniela M
DM
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002227:Carbazoles / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D020014:K562 Cells; D007938:Leukemia / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010077:Oxazepines / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology*; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; C469298:CEP-11004; D002227:Carbazoles; D007211:Indoles; C000715470:MAS1 protein, human; D010077:Oxazepines; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011758:Pyrroles; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D003609:Dactinomycin; D005047:Etoposide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C418868:PBOX-6