Uveal melanoma (UM) is a currently untreatable form of melanoma with a 50% mortality rate. Characterization of the essential signaling pathways driving this cancer is critical to develop target therapies. Activating mutations in the Gαq signaling pathway at the level of GNAQ, GNA11 or rarely CYSLTR2 or PLCβ4 are considered alterations driving proliferation in UM and several other neoplastic disorders. Here, we systematically examined the oncogenic signaling output of various mutations recurrently identified in human tumors. We demonstrate that CYSLTR2->GNAQ/11->PLCβ act in a linear signaling cascade that, via protein kinase C (PKC), activates in parallel the MAP-kinase and FAK/YAP pathways. Using genetic ablation and pharmacological inhibition, we show that the PKC/RasGRP3/MAPK signaling branch is the essential component that drives the proliferation of UM. Only inhibition of the MAPK branch but not the FAK branch synergizes with inhibition of the proximal cascade, providing a blueprint for combination therapy. All oncogenic signaling could be extinguished by the novel GNAQ/11 inhibitor YM-254890, in all UM cells with driver mutation in the Gαq subunit or the upstream receptor. Our findings highlight the GNAQ/11->PLCβ->PKC->MAPK pathway as the central signaling axis to be suppressed pharmacologically to treat for neoplastic disorders with Gαq pathway mutations.
Uveal Melanoma (UM) is a highly lethal cancer with 50% of patients developing lethal metastatic disease, primarily the liver, with currently no effective treatment options. UM is driven by mutations constitutively activating the Gαq pathway, about 90% affecting the heterotrimeric G-protein alpha subunits GNAQ or GNA11 and less commonly (<10%) CYSLTR2 (a GNAQ/11 coupled receptor) or PLCB4 (a direct effector of Gαq). Directly targeting GNAQ/11 therefore could be of therapeutic relevance for the majority of UMs. Here we found that YM-254890, a cyclic depsipeptide, inhibited downstream signaling induced by GNAQQ209L and GNA11Q209L, but not GNA14Q205L, GNA15Q212L and GNASQ227L in 293T cells, confirming that it is a GNAQ/11-specific inhibitor. We systematically examined its activity against other recurring mutations in the Gαq pathway (GNAQ: Q209P, G48V, T175R, R183Q, F228L; GNA11:E191G, R183C, E234K; CYSLTR2: L129Q; PLCB4: D630Y). In 293T cells GNAQQ209P, GNAQR183Q, CYSLTR2L129Q and PLCB4D630Y activated downstream signaling whereas other Gαq mutants did not. YM-254890 inhibited the downstream signaling induced by GNAQQ209P, GNAQR183Q and CYSLTR2L129Q whereas it remained expectedly ineffective against PLCB4D630Y. Furthermore, we found that YM-254890 selectively inhibited Gαq signaling and cell proliferation in a panel of UM cell lines with GNAQ/11 mutations but had no effect on Gαq wild type melanoma cells. In vivo, YM-254890 slowed the growth of liver metastases in a xenograft model of GNAQ mutant UM cells but did not induce tumor shrinkage. Analysis of the tumor lysates revealed that inhibition of Gαq pathway signaling was incomplete. RNAseq analysis of 10 UM cell lines with various GNAQ/11 mutations exposed to YM-254890 revealed that GNAQ/11 inhibition led to significant upregulation of endothelin ET(B) receptor (EDNRB) compared to control treatment. EDNRB is a GNAQ/11 coupled receptor, and western blot confirmed that EDNRB protein level was significantly upregulated when mutant GNAQ/11 was inhibited with either YM-254890 or siRNA. The critical role of endothelin signaling in mediating adaptive resistance to Gαq inhibition was confirmed by demonstrating (1) expression of the EDNRB ligand endothelin 1 in liver metastases of the xenograft model; (2) pharmacological or genetic inhibition of EDNRB was able to break resistance. We also found that the therapeutic efficacy of YM-254890 can be subverted by acquiring additional mutations in the pathway. Upon chronic growth suppression of a GNA11Q209L mutant UM cell line a resistant clone emerged that was demonstrated to harbor a novel GNA11F75Y mutation, affecting the YM-254890 binding site. Concordantly, an engineered GNA11 with the two mutations in cis was resistant to the compound. Our data suggest that targeting mutant GNAQ/11 is promising but will require combinatorial targeting of EDNR signaling and possibly other pathways to reach maximal clinical efficacy. Citation Format: Jiafang Ma, Boris C. Bastian, Xu Chen. Adaptive and acquired resistance to GNAQ/11 inhibition in uveal melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1812.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.