The in vitro examinations showed that (i) some melanoma cell lines with high methylation levels of the 5' IRF6 CGI exhibited suppression of the gene, (ii) other melanoma cell lines with low methylation levels of this CGI exhibited expression of the gene, and (iii) treatment with a demethylating agent restored IRF6 gene expression in the melanoma cell lines that had high methylation levels and suppression of IRF6 before the treatment. Here, IRF6 is linked to melanoma.