MITF and melanoma: Similarly, when the LexOp NrasQ61K/KrasG12V target oncogene is activated by LexPR under the control of the melanocyte-specific mitfa promoter or under the control of the intestine-specific ifabp (fabp2) promoter, double-transgenic zebrafish lines develop, in presence of mifepristone, melanoma or intestinal tumors, respectively [218,219].