ZMYND8-regulation of MITF as potential therapeutic target in melanoma

Melanoma is a highly aggressive and increasingly common cancer, characterized by activating mutations in specific genes which act to activate pathways responsible for survival leading to tumor progression. Although several inhibitors have successfully entered clinical testing with remarkable effects, patients carrying the aforementioned mutations initially respond to treatment with highly effective melanoma regression, they inevitably relapse after some months. There is currently no treatment for these patients. Although a link to a protein called MITF, which acts as a master regulator of the melanoma cell phenotype has been made, the precise mechanisms underpinning MITF's control remains elusive. Despite the fact that attenuation of MITF is poorly understood, its levels have been linked to drug resistance, with low levels predicting resistance to treatment in patients carrying activating mutations in a protein called BRAF, controlling important cellular functions.

This study will examine the role of a protein called ZMYND8 in affecting or controlling MITF levels in patient derived, drug resistant melanoma cell lines. We discovered that ZMYND8 acts to assemble factors that block the expression of proteins and we further found one of these factors to be directly associated with MITF expression. This project will therefore explore how the melanoma master regulator is in turn regulated, providing information on resistance versus sensitivity in melanomas. We anticipate that this research will offer new possibilities in targeting otherwise drug resistant melanomas.

In this project we will use a combination of recombinant, structural and cell biology techniques together with deep sequencing and expression profiling, aiming to understand the transcriptional control exerted over MITF, the melanoma 'master regulator', by ZMYND8, a recruiter of suppressive transcriptional complexes. The project will first examine how ZMYND8 interacts with chromatin and DNA, where it localizes genome-wide, including understanding the contribution to DNA interaction by its modular domains. We will then explore the transcriptional factors and complexes that ZMYND8 recruits and interrogate their co-localization to ZMYND8 specific loci as well as the fate of ZMYND8 localization in their absence. The attenuation of the expression of MITF and its controlled transcriptional programmes will then be examined, seeking to uncover a link to MAPK inhibitor resistance, as low levels of MITF have been linked to drug resistance in patients carrying activating BRAF mutations. The goal of this project is to describe the molecular mechanisms underpinning the attenuation of the melanoma master regulator, MITF, delineating the key factors controlling its levels and discerning the complexity of transcriptional activation/repression by epigenetic factors in melanomas, offering alternative novel targets for disease treatment in drug resistant, mutated BRAF melanomas.

Although MAPK pathway inhibitors achieve remarkably beneficial initial results in melanoma patients carrying BRAF mutations, the disease relapses after a few months and no alternative treatment is available, though new immune therapies hold promise for some patients. This project will characterize a mechanism leading to MITF regulation that may in part be responsible for the attenuation of the levels of this master factor in melanomas, linking to MAPK drug resistance. This project will increase the collective knowledge in transcriptional regulation by shedding light into the way repressor complexes are assembled and control lineage specific markers.

The unprecedented behavior of the reader modules found on ZMYND8, which do not exhibit specificity towards a certain modification or sets of modifications on histones but tolerate a number of chromatin states and the presence of an atypical point towards a potential link between modular components within a protein that dictate its interaction with DNA and chromatin. This is important, as structural and functional information on the role of multiple reader modules (three or more) is lacking. This project therefore will generate the tools and technologies necessary to study multiple domains in the context of chromatin/DNA interactions.

In addition, apart from being a master regulator of melanocytes and melanoma, MITF is also a key regulator in mast cells and osteoclasts where it is likely to play a similar role to that we have uncovered in pigment cells. It is possible that research outlined in this proposal will lead directly to patentable or otherwise commercially exploitable reagents, and may lead to the development of novel therapies or treatment strategies in the future. It is also likely to be of significant interest to academic researchers working in the fields of cellular aging/senescence and cancer, as well as iPS research.

Staff affiliated with this programme will gain solid multi-disciplinary training and will be exposed to a rich network of national and international collaborators, fostering a strong link to science conducted globally in the field of epigenetics as well as melanoma. Interactions in this multidisciplinary network of people will allow scientists to develop better communication and collaborative skills helping them in the long run to better conduct independent research and participate in the scientific progress in the field.