(-)-Epigallocatechin-3-gallate (EGCG) sensitizes melanoma cells to interferon induced growth inhibition in a mouse model of human melanoma

Melanoma incidence has increased over the last few decades and metastatic melanoma is one of the hardest malignancies to treat. Thus, novel approaches are needed for an effective management of melanoma. Interferon-alpha 2b (IFN), an immunomodulatory cytokine commonly used in melanoma treatment, has shown marginal efficacy and often results in discontinuation of therapy due to toxicity. We earlier demonstrated that epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent of green tea, caused cell cycle arrest and apoptosis of human melanoma cells via modulation in cki-cyclin-cdk machinery and Bcl-2 family proteins. This study was undertaken to determine if EGCG could enhance the anti-proliferative effects of IFN. In this study, we demonstrated that EGCG and/or IFN treatments to melanoma cells resulted in a marked (1) decrease in cell proliferation and colony formation ability, and (2) induction of apoptosis. Interestingly, the combination was found to be more effective than either of the agents alone. Further, the anti-proliferative effects of EGCG and/or IFN were accompanied with an increase in Fas protein levels and a decrease in nuclear factor NF kappa B/p65 in the nucleus as well as NF kappa B promoter activity. EGCG and/or IFN also resulted in an increase in Fas-L mediated apoptosis. Further, EGCG and/or IFN treatments resulted in a decrease in melanoma tumor growth and protein levels of proliferation marker PCNA, in athymic nude mice implanted with melanoma tumors. The combination of the two modalities demonstrated a better response than either of them alone. Our data suggest that EGCG could impart therapeutic advantage if used in conjunction with IFN.