PROJECT SUMMARY Uveal melanoma (UVM) is the most common intraocular malignancy, which represents about 5% of all melanoma cases per year in the United States. Half of all patients eventually develop metastatic disease, resulting in an average survival rate of six months and a five year survival rate of ~15%. Recent studies have revealed the underlying genetic landscape of uveal melanoma but have not resulted in any therapeutic options to effectively treat UVM. UVMs harbor mutually exclusive activating mutations in GPCR signaling: ~90% in G- protein alpha q (Gq) subunits GNAQ/GNA11, ~5% in the GPCR CYSLTR2, and ~4% in a downstream effector PLCB4. These mutations aberrantly activate canonical PLCβ signaling: cleavage of PIP2 into DAG and IP3 both of which lead to PKC activation. In addition to uveal melanoma, recent studies have shown this exact pathway to be activated in a subset of cutaneous and mucosal melanomas as well as other diseases like blue nevi, leptomeningeal melanocytic neoplasms (LMNs), and Sturge-Weber syndrome. My project focuses on understanding how Gq signals in UVM tumorigenesis and if Gq inhibition has therapeutic potential in UVM by addressing the following aims: 1) Using a highly specific Gq inhibitor, I will ask how Gq inhibition effects different activating mutations in UVM using representative in vitro models. I have generated melanocytes dependent on different mutations in the PLCβ pathway to study pathway inhibition and therapeutic efficacy. Based on my preliminary data I will also interrogate the mechanistic basis for Gq inhibition sensitivity in GNAQ mutant driven melanocytes. 2) Determine clinical potential of this drug by testing its pharmacological properties in vivo. Using the melanocytes I have generated along with UVM cell lines and our GEMM we will be able to throughouly test the drugs efficacy in mice and ability to inhibit tumor growth in a variety of xenograft experiments. 3) Taking advantage of the ability to inhibit active Gq, I will aim to identify other pathways activated downstream of Gq using proteomic and transcriptomic approaches. This may provide alternative therapeutic strategies to target this recalcitrant disease. The outcome of this research will indicate the effectiveness of Gq inhibition in UVM as well as elucidate currently unknown signaling pathways essential for UVM tumorigenesis. The Chen and Chi labs provide a diverse set of resources and experiences that will greatly benefit my development into an independent researcher. The GSK program provides a solid foundation for scientific achievement with a core course covering vast topics with leaders in the field, graduate seminar series, topical journal clubs, and access to Tri-institutional resources. MSKCC exemplifies a translational science environment by bringing together physicians and scientists who collaborate on cutting edge research to advance treatments for cancer patients.