Downregulation of Bcl-2 sensitises interferon-resistant renal cancer cells to Fas.
Academic Article
Overview
abstract
Interferon alpha (IFNalpha) is used to treat patients with advanced renal cell carcinoma (RCC) despite limited clinical benefit. IFNalpha can induce Fas receptor-mediated apoptosis by direct activation of pro-caspase-8 followed by activation of caspase-3. Alternative, indirect activation of caspase-3 via mitochondrial release of cytochrome c can occur and may explain the rescue from Fas-activated cell death by the antiapoptotic members of the Bcl-2 family. In this study, we examined G3139, a novel antisense compound targeting Bcl-2, in combination with IFNalpha. Human RCC lines (SK-RC-44 and SK-RC-07) were treated with IFNalpha, G3139 or a combination of the two. Fas-mediated cytotoxicity was induced by anti-Fas mAb, CH11. An analysis of Bcl-2, Fas and the cleavage of PARP was performed. IFNalpha induced Fas and Bcl-2 in SK-RC-44 and SK-RC-07. IFNalpha sensitised SK-RC-44 to anti-Fas and induced PARP cleavage confirming that IFNalpha has a cytotoxic effect on RCC lines by induction of the Fas antigen. Cytotoxicity was not evident in SK-RC-07 cells treated with IFNalpha. G3139 induced a specific downregulation of Bcl-2 in SK-RC-07 cells, which were then sensitised to anti-Fas after treatment with IFNalpha. Taken together, these results suggest that Fas-dependent pathways as well as alternative pathways, which can be inhibited by Bcl-2, exist in renal cell carcinoma. G3139 in combination with IFNalpha is a potential therapy in patients with metastatic renal cell carcinoma.
