Activation of the Fas-FasL signaling pathway by MDA-7/IL-24 kills human ovarian cancer cells.
The tumor-suppressive activity of melanoma differentiation-associated gene-7 (mda-7), also known as interleukin 24 (IL-24), has been shown in a spectrum of human cancer cells in vitro and in vivo. However, mechanisms responsible for antitumor activity of mda-7 in human ovarian cancer cells have not been identified. We investigated the therapeutic activity and underlying mechanisms of adenovirus-mediated mda-7 gene (Ad-mda7) transfer in human ovarian cancer cells. Ad-mda7 treatment resulted in overexpression of MDA-7/IL-24 protein in both ovarian cancer and normal ovarian epithelial cells. However, Ad-mda7 significantly (P = 0.001) inhibited cell proliferation and induced apoptosis only in tumor cells and not in normal cells. Studies addressing the mechanism of action of Ad-mda7-induced tumor cell apoptosis revealed early activation of the transcription factors c-Jun and activating transcription factor 2, which in turn stimulated the transcription of an immediate downstream target, the death-inducer Fas ligand (FasL), and its cognate receptor Fas. Associated with the activation of Fas-FasL was the activation of nuclear factor kappaB and induction of Fas-associated factor 1, Fas-associated death domain, and caspase-8. Promoter-based reporter gene analyses showed that Ad-mda7 specifically activated the Fas promoter. Inhibition of Fas using small interfering RNA resulted in a significant decrease in Ad-mda7-mediated tumor cell death. Additionally, blocking of FasL with NOK-1 antibody abrogated Ad-mda7-mediated apoptosis. Collectively, these results show that Ad-mda7-mediated killing of human ovarian cancer cells involves activation of the Fas-FasL signaling pathway, a heretofore unrecognized mediator of MDA-7 apoptosis induction.
Gopalan
Began
B
Department of Thoracic and Cardiovascular Surgery, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA. rramesh@mdanderson.org
Litvak
Anya
A
Sharma
Sikha
S
Mhashilkar
Abner M
AM
Chada
Sunil
S
Ramesh
Rajagopal
R
D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D053222:Fas Ligand Protein; D005260:Female; D018014:Gene Transfer Techniques; D016147:Genes, Tumor Suppressor; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D007378:Interleukins / Q000096:biosynthesis / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D019014:fas Receptor / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000099180:Interleukin-24
D053222:Fas Ligand Protein; D007378:Interleukins; D008562:Membrane Glycoproteins; D019014:fas Receptor; D000099180:Interleukin-24; C505661:FASLG protein, human