Unraveling Resistance Mechanisms to Gαq Pathway Inhibition in Uveal Melanoma: Insights from Signaling-Activation Library Screening.

BACKGROUND/OBJECTIVES: Uveal melanoma (UVM), the leading primary intraocular cancer in adults, is driven by GNAQ/GNA11 mutations, encoding the active forms of Gαq proteins. While local treatments like surgery or radiation can control primary tumors, nearly half of patients die from metastasis. Our aim was identifying potential pathways involved in resistance to targeted therapy in UVM. METHODS: Here, we screened 100 pathway-activating mutant complementary DNAs by lentiviral overexpression to identify those that enhance the survival of cancer cells in the presence of clinically relevant targeted therapies, using BAP1 wild-type UVM cells and validated the most significant results in BAP1-mutant cells. RESULTS: This revealed JAK/STAT activation, overexpression of anti-apoptotic BCL2/BCL-XL, and dysregulated PI3K/mTOR or Hippo pathways as escape routes under MEK-ERK or FAK inhibition. Bioinformatic analysis of UVM transcriptome in TCGA further showed that high expression of the hallmark PI3K/AKT/mTOR pathway and IL6/JAK/STAT signaling correlates with poor prognosis. A similar correlation was shown by YAP and anti-apoptotic signatures. The analysis of individual representative genes from these signatures revealed that MTOR, BCL2L1 (BCL-XL), and TEAD4 gene expression are linked to poorer survival, underscoring the potential clinical impact of these adaptive pathways. Proliferation and apoptosis assay demonstrated that aberrant activation of AKT and YAP promotes resistance to FAK and MEK inhibitors. CONCLUSIONS: These findings support the adaptability of UVM lesions and suggest rational combination therapies targeting both primary GNAQ/GNA11-driven oncogenic signals and their compensatory networks as a more effective, personalized treatment approach for advanced UVM.