GNA13 expression promotes drug resistance and tumor-initiating phenotypes in squamous cell cancers

Treatment failure in solid tumors occurs due to the survival of specific subpopulations of cells that possess tumor-initiating (TIC) phenotypes. Studies have implicated G protein-coupled-receptors (GPCRs) in cancer progression and the acquisition of TIC phenotypes. Many of the implicated GPCRs signal through the G protein GNA13. In this study, we demonstrate that GNA13 is upregulated in many solid tumors and impacts survival and metastases in patients. GNA13 levels modulate drug resistance and TIC-like phenotypes in patient-derived head and neck squamous cell carcinoma (HNSCC) cells in vitro and in vivo. Blockade of GNA13 expression, or of select downstream pathways, using small-molecule inhibitors abrogates GNA13-induced TIC phenotypes, rendering cells vulnerable to standard-of-care cytotoxic therapies. Taken together, these data indicate that GNA13 expression is a potential prognostic biomarker for tumor progression, and that interfering with GNA13-induced signaling provides a novel strategy to block TICs and drug resistance in HNSCCs.

Abstract 3887: GNA13 is a theranostic target that drives drug resistance and cancer stem-like phenotypes in solid tumors

Treatment failure in solid tumors occurs due to the survival of specific subpopulations of cells that possess stem cell-like (CSC) phenotypes. Studies have implicated G protein-coupled-receptors (GPCRs) in cancer progression and the acquisition of aggressive phenotypes. Many of the implicated GPCRs signal through the G12 subfamily, comprised of GNA12 and GNA13. In this study, we demonstrate that GNA13 is upregulated in many solid tumors and impacts survival and metastases in these patients. Consistent with this, we show that GNA13 expression modulates drug resistance through its effect on the CSC sub-population in a panel of patient-derived head and neck (HNSCC) and breast cancer cells. These data were validated in vivo, where GNA13 over-expression in patient-derived xenografts increased tumor initiating capacity, tumorigenicity and drug resistance, with no effect on growth or proliferation. Signaling through NFKB and MAPK pathways appear to be critical to the observed phenotype. Importantly, blockade of GNA13 expression, or select downstream pathways using small-molecule inhibitors, abrogates GNA13-induced CSCs, rendering cells vulnerable to standard-of-care cytotoxic therapy for these cancers. Taken together, these data indicate that GNA13 expression is a potential prognostic biomarker, and interfering with GNA13-induced signaling provides a novel strategy to block CSCs and drug resistance in solid tumors.

Citation Format: Suhail Ahmed Kabeer Rasheed, Hui Sun Leong, Manikandan Lakshmanan, Anandhkumar Raju, Dhivya Dadlani, Fui-Teen Chong, Ravisankar Rajarethinam, Thakshayeni Skanthakumar, Ern Yu Tan, Jacqueline Siok Gek Hwang, Kok Hing Lim, Daniel Shao-Weng Tan, Paolo Ceppi, Mei Wang, Vinay Tergaonkar, Patrick J. Casey, N. Gopalakrishna Iyer. GNA13 is a theranostic target that drives drug resistance and cancer stem-like phenotypes in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3887. doi:10.1158/1538-7445.AM2017-3887

G3BP1, G3BP2 and CAPRIN1 are required for translation of interferon stimulated mRNAs and are targeted by a dengue virus non-coding RNA

Viral RNA-host protein interactions are critical for replication of flaviviruses, a genus of positive-strand RNA viruses comprising major vector-borne human pathogens including dengue viruses (DENV). We examined three conserved host RNA-binding proteins (RBPs) G3BP1, G3BP2 and CAPRIN1 in dengue virus (DENV-2) infection and found them to be novel regulators of the interferon (IFN) response against DENV-2. The three RBPs were required for the accumulation of the protein products of several interferon stimulated genes (ISGs), and for efficient translation of PKR and IFITM2 mRNAs. This identifies G3BP1, G3BP2 and CAPRIN1 as novel regulators of the antiviral state. Their antiviral activity was antagonized by the abundant DENV-2 non-coding subgenomic flaviviral RNA (sfRNA), which bound to G3BP1, G3BP2 and CAPRIN1, inhibited their activity and lead to profound inhibition of ISG mRNA translation. This work describes a new and unexpected level of regulation for interferon stimulated gene expression and presents the first mechanism of action for an sfRNA as a molecular sponge of anti-viral effectors in human cells.