Abstract 1457: Decoding the molecular mechanisms related to mutations in the GNAQ/11 and BAP1 genes in ocular melanoma

Abstract Uveal melanoma (UM) is the most frequent intraocular cancer in adults and 50% of patients develop liver metastases for which no treatment is effective. According to The Cancer Genome Atlas, 92% of cases are characterized by early mutations in two genes coding for alpha subunits of G protein coupled receptors (GPCR): G protein subunit alpha q (GNAQ) or 11 (GNA11). These mutations are mostly found in the codon Q209 causing a constitutive activation of different signaling pathways linked to cellular proliferation such as MAPK and PKC. Furthermore, a bi-allelic inactivation of the BRCA1 associated protein-1 (BAP1) is found in 83% of metastatic UM and causes a loss of function of this protein. Our hypothesis is that the inactivation of compensatory pathways in the absence of these proteins and the understanding of pathways essential only to mutated cells will pave the way for the identification of better therapeutic candidates specific to UM cancer cells (UMCCs) to prevent metastatic progression and improve treatment options. The research objectives include the identification of compensatory signaling pathways in the absence of GNAQ/11 and BAP1 using classical CRISPR/Cas9, the discovery of essential molecular mechanisms for the survival of mutated UMCCs using Prime Editing, and the identification and characterization of novel therapeutic targets using 3D in vitro and in vivo models. First, the electroporation optimization using an eGFP plasmid demonstrated an efficiency of 40-50% for normal choroidal melanocytes (NCM) and 60-80% for UMCCs Mel285. Subsequent transfection with CRISPR complexes resulted in an average editing efficiency of approximately 20% for GNAQ/11 and 60% for BAP1. Currently, we have successfully established a GNAQ knockout (GNAQ-KO) Mel285 cell line. The characterization and validation of this cell line were performed through sequencing and Western blotting, confirming the creation of stop codons and the absence of GNAQ expression. We observed an overactivation of the ERK1/2 pathway and an upregulation of beta-catenin in the Mel285 GNAQ-KO line. Additionally, we noted a decrease in proliferation, adhesion, and migration on collagen I. For Prime editing, we constructed three plasmids with desired mutations. Preliminary tests in HEK293T cells showed an insertion efficiency of 4%, 20%, and 10% for GNAQ, GNA11, and BAP1, respectively, following a single treatment. Finally, in vitro testing has been started for inhibitors targeting compensatory pathways involving beta-catenin (WIKI4) and ERK1/2 (ASN007), in combination with the GNAQ/11 inhibitor (FR900359). These tests are being conducted on various mutant UMCCs for GNAQ/11.A better understanding of the altered pathways in our GNAQ/11 or BAP1 mutant isogenic cell lines will help to identify new drugs targeting specifically UM cells. Citation Format: Aurelie Fuentes-Rodriguez, Andrew Mitchell, Joël Rousseau, Jacques P. Tremblay, Solange Landreville. Decoding the molecular mechanisms related to mutations in the GNAQ/11 and BAP1 genes in ocular melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1457.