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Title: Overexpression of Bcl-2 induces STAT-3 activation via an increase in mitochondrial superoxide
Authors: Kang, J 
Fei Chong, S.J 
Qi Ooi, V.Z
Vali, S
Kumar, A
Kapoor, S
Abbasi, T
Hirpara, J.L 
Loh, T 
Goh, B.C 
Pervaiz, S 
Keywords: complementary DNA
protein bcl 2
Rac1 protein
reduced nicotinamide adenine dinucleotide phosphate oxidase
small interfering RNA
STAT3 protein
protein bcl 2
Rac1 protein
STAT3 protein
STAT3 protein, human
B cell lymphoma
cancer cell
cancer tissue
cell fractionation
cell survival
computer simulation
controlled study
disease severity
follicular lymphoma
genetic transfection
HeLa cell line
Hodgkin disease
human cell
human tissue
large cell lymphoma
molecular interaction
oxidation reduction reaction
polyacrylamide gel electrophoresis
protein expression
protein phosphorylation
Western blotting
wild type
flow cytometry
gene silencing
Blotting, Western
Computer Simulation
Flow Cytometry
Gene Knockdown Techniques
Lymphoma, B-Cell
Proto-Oncogene Proteins c-bcl-2
rac1 GTP-Binding Protein
STAT3 Transcription Factor
Issue Date: 2015
Publisher: Impact Journals LLC
Citation: Kang, J, Fei Chong, S.J, Qi Ooi, V.Z, Vali, S, Kumar, A, Kapoor, S, Abbasi, T, Hirpara, J.L, Loh, T, Goh, B.C, Pervaiz, S (2015). Overexpression of Bcl-2 induces STAT-3 activation via an increase in mitochondrial superoxide. Oncotarget 6 (33) : 34191-34205. ScholarBank@NUS Repository.
Abstract: We recently reported a novel interaction between Bcl-2 and Rac1 and linked that to the ability of Bcl-2 to induce a pro-oxidant state in cancer cells. To gain further insight into the functional relevance of this interaction, we utilized computer simulation based on the protein pathway dynamic network created by Cellworks Group Inc. STAT3 was identified among targets that positively correlated with Rac1 and/or Bcl-2 expression levels. Validating this, the activation level of STAT3, as marked by p-Tyr705, particularly in the mitochondria, was significantly higher in Bcl- 2-overexpressing cancer cells. Bcl-2-induced STAT3 activation was a function of GTPloaded Rac1 and NADPH oxidase (Nox)-dependent increase in intracellular superoxide (O2•-). Furthermore, ABT199, a BH-3 specific inhibitor of Bcl-2, as well as silencing of Bcl-2 blocked STAT3 phosphorylation. Interestingly, while inhibiting intracellular O2•- blocked STAT3 phosphorylation, transient overexpression of wild type STAT3 resulted in a significant increase in mitochondrial O2•- production, which was rescued by the functional mutants of STAT3 (Y705F). Notably, a strong correlation between the expression and/or phosphorylation of STAT3 and Bcl-2 was observed in primary tissues derived from patients with different sub-sets of B cell lymphoma. These data demonstrate the presence of a functional crosstalk between Bcl-2, Rac1 and activated STAT3 in promoting a permissive redox milieu for cell survival. Results also highlight the potential utility of a signature involving Bcl-2 overexpression, Rac1 activation and STAT3 phosphorylation for stratifying clinical lymphomas based on disease severity and chemoresistance.
Source Title: Oncotarget
ISSN: 19492553
DOI: 10.18632/oncotarget.5763
Appears in Collections:Staff Publications

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