IFNB1 and melanoma: The present study also demonstrated that (i) the methylation level of the 5' IRF6 CGI was completely inversely correlated with the sensitivity to IFN-β of the eight melanoma cell lines examined, and (ii) IFN-β enhanced IRF6 expression in the melanoma cell lines that had a considerable amount of unmethylated 5' IRF6 CGI DNA molecules.