Impact of Histone Deacetylase Inhibitors SAHA and MS-275 on IL-8 Synthesis in Human Melanoma Cells

Background: Elevated interleukin-8 (IL-8) levels have been observed in patients with metastatic melanoma, and histone deacetylases inhibitors (HDACis) have been shown to influence melanoma progression. In most instances, HDAC inhibitors were positively acting in cooperation with inducers of IL-8, whereas in other cases IL-8 expression was down-regulated by HDACis. This study aims at investigating whether the HDACis SAHA and MS-275 affect IL-8 expression in melanoma cells. Methods: Cutaneous and uveal melanoma cell lines were treated with HDACis and IL-8 mRNA and protein were determined by real time-PCR and enzyme-linked immunosorbent assay. The protein content of the main transcription factors involved in IL-8 gene regulation and their binding to IL-8 promoter were evaluated by western blot and chromatin immunoprecipitation assay. Cell proliferation and apoptosis rates were also investigated. Results: HDACis strengthened IL-8 mRNA and protein expression. In parallel, increased cell proliferation and reduced rate of apoptosis were observed. The observed activation of IL-8 by HDACis correlated with increased protein levels of c-Jun. On the contrary, CHOP, Rel-A and C/EBPβ synthesis was not affected. Interestingly, SAHA and MS-275 induced c-Jun binding to the IL-8 promoter as well as c-Jun transcription by favoring the recruitment of the preinitiation complex (RNA polymerase II and TFIIB) to the c-Jun promoter. Conclusions: Data reported here indicate that the inhibition of class I HDAC activity is a requisite to activate IL-8 expression in cutaneous as well as uveal melanoma. The increase of IL-8 was mediated by c-Jun promoter activation and was accompanied by enhanced cell proliferation and reduced apoptosis.