Targeting the PREX2/RAC1/PI3Kβ Signaling Axis Confers Sensitivity to Clinically Relevant Therapeutic Approaches in Melanoma.

Metastatic melanoma remains a major clinical challenge. Large-scale genomic sequencing of melanoma has identified bona fide activating mutations in RAC1, which are associated with resistance to BRAF-targeting therapies. Targeting the RAC1-GTPase pathway, including the upstream activator PREX2 and the downstream effector PI3Kβ, could be a potential strategy for overcoming therapeutic resistance, limiting melanoma recurrence, and suppressing metastatic progression.

[Epigenetic regulation of gene expression in malignant melanoma].

Malignant melanoma is a highly aggressive cancer with a propensity for early metastasis. Melanocyte transformation results predominantly from oncogenic mutations in BRAF, NRAS or NF1 leading to constitutive activation of the MAP kinase pathway driving cell proliferation and second site mutations such as loss of CDKN1A, or PTEN or activating mutations in the beta-catenin pathway that allow escape from oncogene induced senescence. Nevertheless, irrespective of the nature of the driver mutations, melanoma cell physiology is strongly regulated by transcription factors and epigenetic mechanisms.

Chromatin-Remodelling Complex NURF Is Essential for Differentiation of Adult Melanocyte Stem Cells.

MIcrophthalmia-associated Transcription Factor (MITF) regulates melanocyte and melanoma physiology. We show that MITF associates the NURF chromatin-remodelling factor in melanoma cells. ShRNA-mediated silencing of the NURF subunit BPTF revealed its essential role in several melanoma cell lines and in untransformed melanocytes in vitro.

Transcription factor MITF and remodeller BRG1 define chromatin organisation at regulatory elements in melanoma cells.

Microphthalmia-associated transcription factor (MITF) is the master regulator of the melanocyte lineage. To understand how MITF regulates transcription, we used tandem affinity purification and mass spectrometry to define a comprehensive MITF interactome identifying novel cofactors involved in transcription, DNA replication and repair, and chromatin organisation. We show that MITF interacts with a PBAF chromatin remodelling complex comprising BRG1 and CHD7.

Identification of a ZEB2-MITF-ZEB1 transcriptional network that controls melanogenesis and melanoma progression.

Deregulation of signaling pathways that control differentiation, expansion and migration of neural crest-derived melanoblasts during normal development contributes also to melanoma progression and metastasis. Although several epithelial-to-mesenchymal (EMT) transcription factors, such as zinc finger E-box binding protein 1 (ZEB1) and ZEB2, have been implicated in neural crest cell biology, little is known about their role in melanocyte homeostasis and melanoma. Here we show that mice lacking Zeb2 in the melanocyte lineage exhibit a melanoblast migration defect and, unexpectedly, a severe melanocyte differentiation defect.