Oncogenic MITF dysregulation in clear cell sarcoma: Defining the MiT family of human cancers

Clear cell sarcoma (CCS) harbors a pathognomonic chromosomal translocation fusing the Ewing's sarcoma gene (EWS) to the CREB family transcription factor ATF1 and exhibits melanocytic features. We show that EWS-ATF1 occupies the MITF promoter, mimicking melanocyte-stimulating hormone (MSH) signaling to induce expression of MITF, the melanocytic master transcription factor and an amplified oncogene in melanoma. Knockdown/rescue studies revealed that MITF mediates the requirement of EWS-ATF1 for CCS survival in vitro and in vivo as well as for melanocytic differentiation. Moreover, MITF and TFE3 reciprocally rescue one another in lines derived from CCS or pediatric renal carcinoma. Seemingly unrelated tumors thus employ distinct strategies to oncogenically dysregulate the MiT family, collectively broadening the definition of MiT-associated human cancers.