BARF1 gene silencing triggers caspase-dependent mitochondrial apoptosis in Epstein-Barr virus-positive malignant cells.
Epstein-Barr virus (EBV)-encoded BARF1 (BamH1-A Rightward Frame-1) is expressed in EBV-positive malignancies such as nasopharyngeal carcinoma, EBV-associated gastric cancer, B-cell lymphoma and nasal NK/T-cell lymphoma, and has been shown to have an important role in oncogenesis. However, the mechanism by which BARF1 elicits its biological effects is unclear. We investigated the effects of BARF1 silencing on cell proliferation and apoptosis in EBV-positive malignant cells. We observed that BARF1 silencing significantly inhibits cell proliferation and induces apoptosis-mediated cell death by collapsing the mitochondrial membrane potential in AG876 and Hone-Akata cells. BARF1 knockdown up-regulates the expression of pro-apoptotic proteins and downregulates the expression of anti-apoptotic proteins. In BARF1-down-regulated cells, the Bcl-2/BAX ratio is decreased. The caspase inhibitor z-VAD-fmk was found to rescue siBARF1-induced apoptosis in these cells. Immunoblot analysis showed significant increased levels of cleaved caspase 3 and caspase 9. We observed a significant increase in cytochrome c level as well as the formation of apoptosome complex in BARF1-silenced cells. In conclusion, siRNA-mediated BARF1 down-regulation induces caspase-dependent apoptosis via the mitochondrial pathway through modulation of Bcl-2/BAX ratio in AG876 and Hone-Akata cells. Targeting BARF1 using siRNA has the potential to be developed as a novel therapeutic strategy in the treatment of EBV-associated malignancies.
Institute of Biological Sciences (Genetics and Molecular Biology), Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
Taznim Begam Mohd
TB
Mohidin
Ching Ching
CC
Ng
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000378:metabolism*; D053478:Apoptosomes / Q000096:biosynthesis; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D045304:Cytochromes c / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000235:genetics* / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000821:virology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D034622:RNA Interference; D034741:RNA, Small Interfering; D014764:Viral Proteins / Q000235:genetics*; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis
D000590:Amino Acid Chloromethyl Ketones; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes; C086495:BARF1 protein, Human herpesvirus 4; D061945:Caspase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D014764:Viral Proteins; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D045304:Cytochromes c; D053148:Caspase 3; D053453:Caspase 9