MAPK7 and neoplasm: To further investigate whether ERK5 promotes migration and invasion in other types of tumor cells, we employed a constitutively active mutant of an upstream kinase of ERK5 named MEK5 (MEK5D), and we expressed it with ERK5 to study functional responses to ERK5 activation in two murine melanoma cell lines (B16F10 and B16F1) with the same origin and genetic background but with different metastatic potency.