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BPTF transduces MITF-driven prosurvival signals in melanoma cells.

ABSTRACT: Microphthalmia-associated transcription factor (MITF) plays a critical and complex role in melanocyte transformation. Although several downstream targets of MITF action have been identified, the precise mechanisms by which MITF promotes melanocytic tumor progression are incompletely understood. Recent studies identified an oncogenic role for the bromodomain plant homeodomain finger transcription factor (BPTF) gene in melanoma progression, in part through activation of BCL2, a canonical target of MITF signaling. Analysis of the BPTF promoter identified a putative MITF-binding site, suggesting that MITF may regulate BPTF expression. Overexpression of MITF resulted in up-regulation of BPTF in a panel of melanoma and melanocyte cell lines. shRNA-mediated down-regulation of MITF in melanoma cells was accompanied by down-regulation of BPTF and BPTF-regulated genes (including BCL2) and resulted in reduced proliferative capacity of melanoma cells. The suppression of cell growth mediated by MITF silencing was rescued by overexpression of BPTF cDNA. Binding of MITF to the BPTF promoter was demonstrated using ChIP analysis. MITF overexpression resulted in direct transcriptional activation of BPTF, as evidenced by increased luciferase activity driven by the BPTF promoter. These results indicate that BPTF transduces key prosurvival signals driven by MITF, further supporting its important role in promoting melanoma cell survival and progression.

SUBMITTER: Dar AA

PROVIDER: S-EPMC4896689 | biostudies-other | 2016 May

REPOSITORIES: biostudies-other

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MITF deficiency accelerates GNAQ-driven uveal melanoma

2023-03-11 | PXD030527 | Pride

MITF deficiency accelerates GNAQ-driven uveal melanoma

Project description:Cutaneous melanoma (CM) and uveal melanoma (UM) both originate from the melanocytic lineage but are primarily driven by distinct oncogenic drivers, BRAF/NRAS or GNAQ/GNA11 respectively. The melanocytic master transcriptional regulator, MITF, is essential for both CM development and maintenance, but its role in UM is largely unexplored. Here, we use zebrafish models to dissect the key UM oncogenic signaling events, and establish the role of MITF in UM tumors. Using a melanocytic lineage expression system, we showed that patient-derived mutations of GNAQ (GNAQQ209L) or its upstream CYSLTR2 receptor (CYSLTR2L129Q) both drive UM when combined with a cooperating mutation, tp53M214K/M214K. The tumor-initiating potential of the major GNAQ/11 effector pathways, YAP and PLCβ-ERK, was also investigated in this system, and thus showed that while activated YAP (YAPAA) induced UM with high potency, the patient-derived PLC4 mutation (PLCB4D630Y) very rarely yielded UM tumors in the tp53M214K/M214K context. Remarkably, mitfa deficiency was profoundly UM promoting, dramatically accelerating the onset and progression of tumors induced by Tg(GNAQQ209L);tp53M214K/M214K or Tg(CYSLTR2L129Q);tp53M214K/M214K. Moreover, mitfa loss was sufficient to cooperate with GNAQQ209L to drive tp53-wildtype UM development, and allowed Tg(PLCB4D630Y);tp53M214K/M214K melanocyte lineage cells to readily form tumors. Notably, all of the mitfa-/- UM tumors, including those arising in Tg(mitfa:PLCB4D630Y);tp53M214K/M214K;mitfa-/- fish, displayed nuclear YAP while lacking hyperactive ERK indicative of PLCβ signaling. Collectively, these data show that YAP signaling is the major mediator of UM, and that MITF acts as bona fide tumor suppressor in UM, in direct opposition to its essential role in CM.

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