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

## TL;DR

This study identifies new resistance pathways in uveal melanoma and suggests combination therapies to improve treatment outcomes.

## Contribution

The study reveals novel compensatory pathways contributing to resistance in uveal melanoma and proposes targeted combination therapies.

## Key findings

- JAK/STAT, BCL2/BCL-XL, PI3K/mTOR, and Hippo pathways contribute to resistance in uveal melanoma.
- High expression of MTOR, BCL2L1, and TEAD4 correlates with poor survival in uveal melanoma patients.
- Aberrant AKT and YAP activation promotes resistance to FAK and MEK inhibitors.

## Abstract

Uveal melanoma is an aggressive ocular malignancy with high mortality rates. Although localized interventions such as surgical resection or radiotherapy effectively control the primary tumor, many patients ultimately develop metastatic disease. Current therapies targeting principal oncogenic drivers often fail to provide durable responses, underscoring the need to elucidate alternative survival pathways that confer resistance. In this study, we systematically evaluated gene function in laboratory models of uveal melanoma, identifying critical contributions from signaling pathways including JAK/STAT, BCL2/BCL-XL, PI3K/mTOR, and Hippo. These results highlight novel molecular mechanisms underpinning therapeutic resistance and support the development of combinatorial treatment strategies. Such approaches may offer improved clinical outcomes for patients with advanced uveal melanoma by effectively targeting both primary oncogenic drivers and resistance mechanisms.

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.