Pegylated IFN-α sensitizes melanoma cells to chemotherapy and causes premature senescence in endothelial cells by IRF-1-mediated signaling

Pegylated interferon-alpha 2b (pIFN-alpha) is an integral part of the drug regimen currently employed against melanoma. Interferon regulatory factor-1 (IRF-1) has an important role in the transcriptional regulation of the IFN response, cell cycle and apoptosis. We have studied pIFN-alpha-induced responses when combined with the chemotherapy agent, vinblastine (VBL), in tumor and endothelial cell lines and the connection to IRF-1 signaling. Levels of IRF-1/IRF-2 protein expression were found to be decreased in tumor versus normal tissues. pIFN-alpha induced IRF-1 signaling in human melanoma (M14) and endothelial (EA.hy926) cells and enhanced cell death when combined with VBL. Upon combined IFN-alpha and VBL treatment, p21 expression, poly (ADP-ribose) polymerase cleavage and activated Bak levels were increased in M14 cells. An increase in p21 and cyclin D1 expression occurred in EA.hy926 cells after 6 h of treatment with pIFN-alpha, which dissipated by 24 h. This biphasic response, characteristic of cellular senescence, was more pronounced upon combined treatment. Exposure of the EA.hy926 cells to pIFN-alpha was associated with an enlarged, multinucleated, beta-galactosidase-positive senescent phenotype. The overall therapeutic mechanism of IFN-alpha combined with chemotherapy may be due to both direct tumor cell death via IRF-1 signaling and by premature senescence of endothelial cells and subsequent effects on angiogenesis in the tumor microenvironment. Cell Death and Disease (2010) 1, e67; doi: 10.1038/cddis.2010.43; published online 26 August 2010