KIT Induces SRC-Mediated Tyrosine Phosphorylation of MITF and Altered Transcription Program in Melanoma.

The oncogenic D816V mutation of the KIT receptor is well characterized in systemic mastocytosis and acute myeloid leukemia. Although KIT has been found in melanoma, its function and involvement in this malignancy is not understood. Here we show that KIT induces tyrosine phosphorylation of MITF through a triple protein complex formation between KIT, MITF, and SRC family kinases. In turn, phosphorylated MITF activates target genes that are involved in melanoma proliferation, cell-cycle progression, suppression of senescence, survival, and invasion. By blocking the triple protein complex formation, thus preventing MITF phosphorylation, the cells became hypersensitive to SRC inhibitors. We have therefore delineated a mechanism behind the oncogenic effects of KIT in melanoma and provided a rationale for the heightened SRC inhibitor sensitivity in KIT transformed cells. This study demonstrates that an oncogenic tyrosine kinase mutant, KIT, can alter the transcriptional program of the transcription factor MITF in melanoma .