Inhibition of NF-κB-Dependent Signaling Enhances Sensitivity and Overcomes Resistance to BET Inhibition in Uveal Melanoma

Bromodomain and extraterminal protein inhibitors (BETi) are epigenetic therapies aimed to target dysregulated gene expression in cancer cells. Despite early successes of BETi in a range of malignancies, the development of drug resistance may limit their clinical application. Here, we evaluated the mechanisms of BETi resistance in uveal melanoma, a disease with little treatment options, using two approaches: a high-throughput combinatorial drug screen with the clinical BET inhibitor PLX51107 and RNA sequencing of BETi-resistant cells. NF-kappa B inhibitors synergistically sensitized uveal melanoma cells to PLX51107 treatment. Furthermore, genes involved in NF-kappa B signaling were upregulated in BETi-resistant cells, and the transcription factor CEBPD contributed to the mechanism of resistance. These findings suggest that inhibitors of NF-kappa B signaling may improve the efficacy of BET inhibition in patients with advanced uveal melanoma. Significance: These findings provide evidence that inhibitors of NF-kappa B signaling synergize with BET inhibition in in vitro and in vivo models, suggesting a clinical utility of these targeted therapies in patients with uveal melanoma.