Epigenetic up-regulation of C-C chemokine receptor 7 and C-X-C chemokine receptor 4 expression in melanoma cells

Histone deacetylation and DNA methylation establish epigenetic modifications, which through chromatin remodeling may result in gene silencing. We hypothesized that chemokine receptors C-C chemokine receptor 7 (CCR7) and C-X-C chemokine receptor 4 (CXCR4) on melanoma cells undergo epigenetic regulation. We investigated whether a histone deacetylase inhibitor and a demethylating agent influence CCR7 and CXCR4 expression on melanoma cells. Initially, microarray analysis was done to screen changes in chemokine receptor expression on melanoma cells after treatment with trichostatin A (TSA) and 5-Aza-2-deoxycytidine (5-Aza). CCR7 and CXCR4 mRNA expression were uniformly altered and selected for further investigation. Quantitative real-time reverse transcription-PCR assay, immunohistochemistry, and Western blot analysis were used to assess changes in mRNA and protein expression induced by TSA and 5-Aza in melanoma lines. Cell migration assays were conducted to assess the effects of altered CCR7 and CXCR4 expression on cell function. Treatment with TSA or 5-Aza increased gene expression of both CCR7 and CXCR4 in melanoma lines. TSA was the strongest enhancer. With combined treatment, CCR7 and CXCR4 mRNA expression was also up-regulated. Immunohistochemistry after combined treatment showed enhanced staining of both CCR7 and CXCR4 compared with control cells. Melanoma cell migration in TSA and 5-Aza-treated cells was 7-and 2-fold higher than control cells for CCR7 and CXCR4, respectively. In summary, a histone deacetylase inhibitor and a demethylating agent up-regulated CCR7 and CXCR4 expression on melanoma cells. This increase in chemokine receptor expression correlated with functional activity. Most importantly, we have identified an epigenetic mechanism that may endogenously regulate chemokine receptor expression on melanoma cells.