<div>Abstract<p>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-κB inhibitors synergistically sensitized uveal melanoma cells to PLX51107 treatment. Furthermore, genes involved in NF-κB 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-κB signaling may improve the efficacy of BET inhibition in patients with advanced uveal melanoma.</p>Significance:<p>These findings provide evidence that inhibitors of NF-κB signaling synergize with BET inhibition in <i>in vitro</i> and <i>in vivo</i> models, suggesting a clinical utility of these targeted therapies in patients with uveal melanoma.</p></div>
<p>Supplemental Figure 1: HGF inhibits trametinib-induced apoptosis in UM cells; Supplemental Figure 2: Bim-EL or Bmf expression renders UM cells susceptible to apoptosis; Supplemental Figure 3: Human hepatic stellate cell (HHSteC) conditioned medium activates HGF-cMET signaling; Supplemental Figure 4: Human hepatic stellate cell (HHSteC) conditioned medium effects on migration and invasion of UM cells; Supplemental Figure 5: Isoform specific PI3K inhibitors differentially block HGF-mediated activation of AKT in UM001 cells.</p>
<p>Supplemental Table 1. RNA Seq z-score values for genes significantly up- or downregulated in MEKi-R or CDK4/6i-T groups compared to controls, corresponding to figure 3A. Data are indexed to show which genes are significant for each comparison (BHFDR < 0.05 and absolute log2(FC) > 1).</p>
The mechanisms driving late relapse in uveal melanoma (UM) patients remains a medical mystery and major challenge. Clinically it is inferred that UM disseminated cancer cells (DCCs) persist asymptomatic for years-to-decades mainly in the liver before they manifest as symptomatic metastasis. Here we reveal using Gαq/11
Abstract Despite the clinical success of targeted inhibitors, tumor responses to these agents are transient, and drug-tolerant residual cells seed resistance. Understanding the role of tumor-intrinsic mechanisms and effects of the tumor microenvironment in mediating drug tolerance will guide and optimize targeted therapies. Given similarities between drug tolerance and cellular dormancy, we studied the role of nuclear receptor subfamily 2 group F member 1 (NR2F1) in response to targeted therapy. We used BRAF-mutant cutaneous melanoma models treated with BRAF and MEK inhibitors (BRAFi + MEKi) since patients treated with this combination typically develop resistance. The aged tumor microenvironment has been shown to increase therapy resistance, and we find that melanoma cells in aged mice express higher levels of NR2F1 than when the same cells are injected into young animals. Transcriptomic analysis of melanoma patient samples treated with BRAFi + MEKi showed increased expression of NR2F1 post-treatment. Similarly, NR2F1 was highly expressed in minimal residual disease collected on BRAFi + MEKi treatment in patient- and xenograft-derived tumors. High expression of NR2F1 promotes tumor survival and invasion in the presence of BRAFi + MEKi in vitro leading to tolerance to BRAFi + MEKi efficacy in vivo. Depletion of NR2F1 in YUMM1.7 allografts grown in aged mice improved response to the combination therapy. Altogether, our findings suggest that NR2F1 promotes drug tolerance leading to minimal residual disease in melanoma and that NR2F1-high cells may be targeted with CDK4/6 inhibitors to improve targeted therapy outcomes in melanoma patients. Citation Format: Manoela Tiago, Timothy J. Purwin, Mitchell E. Fane, Yash Chhabra, Jessica L. F. Teh, Rama Kadamb, Weijia Cai, Inna Chervoneva, Sheera Rosenbaum, Vivian Chua, Nir Hacohen, Michael A. Davies, Jessie Villanieva, Ashani T. Weeraratna, Claudia Capparelli, Julio A. Aguirre-Ghiso, Andrew E. Aplin. The aged tumor microenvironment influences tolerance to targeted therapy via NR2F1 overexpression in BRAF-mutant melanoma [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr A005.
