MITF in melanoma progression, pathology and survival in vivo
MITF is the master melanocyte transcription factor and has a complex role in melanoma. Both gain- and loss-of function mutations in MITF have been identified in melanoma, although its’ role in melanoma development and the effects of targeting MITF are unknown. Using a temperature-sensitive mitf zebrafish mutant I show that low levels of MITF are oncogenic with BRAFV600E in melanoma progression. By pathology and MITF target gene expression, BRAFV600Emitfavc7 tumours are distinct from BRAFV600Ep53M214K tumours, and represent two melanoma subtypes. Melanomagenesis can also be driven independently of BRAFV600E, in a transgenic zebrafish with mutations in mitf and p53, representing a new melanoma model. Abrogating MITF activity in BRAFV600Emitfavc7 melanoma leads to regression of the tumour, characterised by macrophage infiltration and increased apoptosis. This result confirms the dependence on MITF activity in BRAFV600Emitfavc7 melanomas and highlights the role of MITF as a therapeutic target for melanoma. Exome and transcriptome sequencing has been carried out to gain insight into the expression and genomic mutational landscape that is driven by these melanoma transgenic models and results in these genotype-phenotype specific subtypes observed.