Transcriptional and post-transcriptional drivers of Melanoma

About This Grant

Abstract PAX3 is an indispensable upstream regulator of normal melanocyte survival, population expansion, and migration, and these functions are subverted in melanoma proliferation, resistance to apoptosis, and metastasis. Despite significant advances in treatment, melanoma is still a deadly cancer with considerable mortality rates, and PAX3 contributes to this by supporting cancer aggressiveness, resistance to therapies, and relapse. While PAX3 is expressed in developing melanoblasts and melanocyte stem cells, downregulation of PAX3 during terminal differentiation is required. In melanoma, PAX3 expression is overexpressed, maintained, and essential for cancer progression. Melanoma cells rely on PAX3 function; indeed, a loss of PAX3 expression leads to catastrophic loss of melanoma cell growth, migration, and viability. Due to the significance of PAX3 in melanoma, it is surprising how much is unknown about PAX3 function. Classically defined as a transcription factor, only a handful of PAX3 downstream target genes in melanoma are known. Our lab and others have uncovered select downstream effector genes that can explain some but not all of the wide roles that PAX3 has on melanoma survival and progression. To uncover clues on other functions of PAX3, our laboratory performed an unbiased immunoprecipitation and mass spectroscopy (IP/MS) screen to identify PAX3 binding partners. Unexpectedly, we discovered that PAX3 interacted with several proteins involved with RNA surveillance, decay, and splicing. Further, our preliminary data support that this role in RNA regulation is independent of the transcriptional role of PAX3. The goal of this proposal is to uncover how PAX3 regulates these cell functions through downstream effector genes, by acting directly on genetic regulation or indirectly through other molecular means. To address the significant gaps in knowledge into PAX3 function, the hypothesis guiding this proposal is that PAX3 can dynamically act on downstream genes through canonical and noncanonical transcription factor functions, with outcomes modified by binding partners, tumor stage, and small molecule inhibitors. The major scientific impact of this proposal is to reveal a PAX3 dependent genomic enhancer map in melanoma connected to regulated genes, discover mechanisms for modulating this signature, and exploit these pathways as targets for therapy. The innovation of this proposal lies in a more detailed focus on PAX3, in terms of what genes are controlled and how. We propose the innovative hypothesis that PAX3 is not purely a canonical transcription factor and can function both transcriptionally and post-transcriptionally. This work is significant since the PAX3 transcriptional signature in melanoma is still undiscovered, and it is not clear if it is static or adaptive at different tumor stages or drug treatments. This work will uncover PAX3-dependent pathways driving melanoma progression and reveal potential molecular weak points that can be targeted by therapeutics. Use of mice in this proposal: The rationale for utilizing mouse models is that normal and pathological cells behave differently in vivo due to a complex microenvironment that cannot be replicated in other model systems.