Alexander Warthen

Targeting nucleotide exchange to inhibit constitutively active G-protein alpha subunits in cancer

Uveal Melanoma (UM) is the most common and devastating form of intraocular cancer. There are no effective therapies for metastatic disease. When patients are diagnosed with UM, 50% have a post-diagnosis life expectancy of less than 10 months. The current standard-of-care treatment involves resection of the orbit and soft tissues around the eye, and there are no targeted pharmaceutical therapies for the disease. Approximatively 80% of UM patients express frequent somatic mutations in the heterotrimeric G protein alpha subunit, GNAQ. GNAQ encodes heterotrimeric G protein alpha subunits of the q class (ɑ, β, ɣ). These subunits are 90% identical to each other at the amino acid level and play redundant roles. The function of Gαq is to hydrolyze GDP into GTP, effectively linking various G protein-coupled receptors (GPCR) to downstream signaling effectors inside cells. Gαq mutations, particularly GNAQ Q209L, lead to a constitutively activated Gαq protein that effectively converts the Gαq protein into an activated oncogene product. This study applied high throughput screening (HTS) of a kinase drug library to identify drugs that target UM by modulating the activity of GNAQQ209L. Isogenic HEK293 cell lines that express the Q209L mutation were generated. Parental and mutated HEK293 cells were used to test a kinase drug library of 155 compounds to identify drugs capable of modulating two major pathways downstream of Gαq: the PI3K/Inositol-1-Phosphate (IP1) pathway and the PKC/MAP Kinase pathway. Cell viability and IP1 assays identified eight compounds that produced statistically significant differences in pathway activity between the parental and mutated cell lines, suggesting that these drugs may have a selective effect on the GNAQ Q209L mutant. Further confirmation of these results will be conducted using an uveal melanoma cell line expressing the Q209L mutation. Additionally, 2D and 3D models will be used to validate future findings.