Abstract 2580: Nuclear receptor coactivator 3 (NCOA3) fuels oncogenic pathways in uveal melanoma
Authors: Rusin Aleksandra , Echartea Maria E. Ruiz , Skapura Darlene G. , deRuiz Karen Berman , Davis Christel M. , Ehli Eric A. , Grimm Sandra L. , Coarfa Christian , Kaochar Salma 
Published: April 2023

Background: Uveal melanoma (UM) originates from melanocytes residing in the uveal tract of an eye. Despite effective local control, approximately half of patients develop metastatic disease resistant to systemic chemotherapy and presenting poor response to immunotherapy or targeted therapy. UM patients have a median overall survival of 6 to 12 months. The basis of the pathogenesis of UM are mutations in GNAQ and GNA11 genes resulting in constitutive activation of PKC/MAPK signaling. Here, we analyzed the role of NCOA3, a transcription factor coactivator that was previously shown to be modified by PKC in multiple cancer, as a factor potentiating oncogenic outcome of multiple oncogenic pathways activated in UM downstream of GNAQ or GNA11.

Methods: We examined the impact of altered NCOA3 mRNA in UM, using publicly available TCGA dataset. Next, we used CRISPR/Cas9 technology to delete NCOA3 protein in MP41 UM cell line. We evaluated proliferation of MP41/NCOA3 KO cell subline and its parental counterpart in vitro by a colony formation assay. Next, we analyzed growth of xenografts of MP41/NCOA3 KO and parental cells in SCID/beige mice. To understand the molecular consequences of NCOA3 activity in UM, we performed a genome wide comparison of gene expression in MP41/NCOA3 KO and parental cells. Functional enrichment analysis was used to identify classes of genes associated with NCOA3 activity and determine similarities with datasets obtained by targeting proteins of GNAQ/GNA11 pathways and inhibiting activity of NCOA3 using a tool small molecule inhibitor SI-2 in UM cell lines.

Results: We found that NCOA3 overexpression negatively correlated with UM patients’ progression free and overall survival. Knockout of NCOA3 gene in MP41 UM cells substantially reduced their proliferation in vitro and xenograft growth in mice. Global gene expression analysis revealed that NCOA3 activity is linked with transcriptional signatures associated with cell mitotic activity (cell cycle and DNA replication) and transcriptional machinery binding (especially affecting E2F and myc regulated programs). The MP41 NCOA3 KO normalized enrichment scores (NES) show high concordance with NES obtained after silencing GNAQ or GNA11 in UM cell lines and pharmacological targeting PKC or NCOA3.

Conclusions: Inhibition of NCOA3 activity inhibits several oncogenic pathways in a concerted manner, limiting UM cell survival and tumor growth. Our results deliver proof of concept that NCOA3 is a master transcriptional co-regulator of oncogenic signaling in uveal melanoma and a potential therapeutic target.

Citation Format: Aleksandra Rusin, Maria E. Ruiz Echartea, Darlene G. Skapura, Karen Berman deRuiz, Christel M. Davis, Eric A. Ehli, Sandra L. Grimm, Christian Coarfa, Salma Kaochar. Nuclear receptor coactivator 3 (NCOA3) fuels oncogenic pathways in uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2580.