MITF and melanoma: Investigating mRNA expression levels, as determined by microarray or RNA-Seq gene expression analysis, several different groups in the late 2000s identified sets of genes in melanoma cell populations exhibiting changes in their gene expression patterns, either positively or negatively in concert with changes in MITF levels, and categorized those gene sets as “invasive” and “non-invasive” [33] and “proliferative” and “invasive” [34].