Antimelanoma Effects of Concomitant Inhibition of SIRT1 and SIRT3 in Braf/Pten Mice.

Novel therapeutic strategies are required for the effective and lasting treatment of metastatic melanoma, one of the deadliest skin malignancies. In this study, we determined the antimelanoma efficacy of 4'-bromo-resveratrol (4'-BR), which is a small-molecule dual inhibitor of SIRT1 and SIRT3, in a Braf/Pten mouse model that recapitulates human disease, including metastases. Tumors were induced by topical application of 4-hydroxy-tamoxifen on shaved backs of mice aged 10 weeks, and the effects of 4'-BR (5‒30 mg/kg of body weight, intraperitoneally, 3 days per week for 5 weeks) were assessed on melanoma development and progression. We found that 4'-BR at a dose of 30 mg/kg significantly reduced the size and volume of primary melanoma tumors as well as lung metastasis with no adverse effects. Furthermore, mechanistic studies on tumors showed significant modulation in the markers of proliferation, survival, and melanoma progression. Because SIRT1 and SIRT3 are linked to immunomodulation, we performed differential gene expression analysis using a PanCancer Immune Profiling Panel (770 genes). Our data showed that 4'-BR significantly downregulated the genes related to metastasis promotion, chemokine/cytokine regulation, and innate/adaptive immune functions. Overall, inhibition of SIRT1 and SIRT3 by 4'-BR is a promising antimelanoma therapy with antimetastatic and immunomodulatory activities warranting further detailed studies, including clinical investigations.