Abstract 2426: GNG4 is a candidate G-proteinγ-subunit downstream of the Cxcl10/Cxcr3 axis that mediates cell migration in breast cancer
Authors: Bagchi Sukriti , Kim Suwon 
Published: June 2022

Abstract
Introduction: Cxcl10 chemokine signaling has been implicated in cancer cell invasion and metastasis, but the mechanism is not well understood. Our prior studies have shown that deletion of the ING4 tumor suppressor in breast cancer cells enabled migration in response to Cxcl10. Further, migration was blocked by small molecule inhibition of either the Cxcl10 receptor Cxcr3, or Gβγ, but not Gαi, indicating that Gβγ was a key component downstream of Cxcl10/Cxcr3 signaling. There are 5 GNB genes encoding Gβ and 14 GNG genes encoding Gγ subunits in the human genome, however the precise subunits downstream of Cxcl10/Cxcr3 in breast cancer are unknown.
Methods: RNA sequencing was used to identify differentially expressed genes in response to Cxcl10 treatment in ING4-deleted MDAmb-231 breast cancer cells, with a focus on GNB or GNG genes. Clinical and gene expression data of primary tumors obtained from NCBI GEO dataset GDS806 were used to evaluate correlation between GNG4 expression and patient survival. A CRISPR/Cas9 system was used to delete GNG4 in MDAmb231 cells and Western blot was used to confirm the gene deletion. We evaluated Cxcl10-induced migration of GNG4-deleted cells using transwell assays.
Results: RNA sequencing showed that expression of GNG4 and GNG14 among the GNG genes was increased by 9 fold and 8 fold, respectively, in ING4-deleted MDAmb231 cells treated with Cxcl10, suggesting that these may encode effector(s) downstream of Cxc10/Cxcr3. GNG4 expression alone did not correlate with disease free survival (DFS) in breast cancer patients. However, a trend towards improved DFS was observed in patients with tumors expressing high ING4 and low GNG4 levels compared to those with low ING4 and high GNG4 expressing tumors (HR=0.32, 95% CI 0.10-1.03, p=0.051), suggesting high GNG4 expression in the absence of ING4 may contribute to aggressive breast cancer. Effects of GNG4 deletion in Cxcl10-induced migration are currently being evaluated.
Conclusions: GNG4, encoding G-protein subunit γ-4, was induced following Cxcl10 treatment specifically in ING4-deleted breast cancer cells, suggesting that ING4 may repress GNG4 expression. Low ING4 and high GNG4 expression in breast tumors correlated with poor patient survival, implicating GNG4 as a candidate Gγ subunit in the Cxcl10/Cxcr3/ING4 axis. The function of GNG4 and GNG14 (Gγ-14) in Cxcl10-mediated breast cancer cell migration will be determined in the near future. These results may provide evidence that Gγ subunits, in particular, Gγ-4 or Gγ-14, play a role in Cxcl10/Cxcr3 signaling that mediates cancer cell migration. These results present Gβγ subunits as potential therapeutic targets for treatment of ING4-deficient breast cancer.
Citation Format: Sukriti Bagchi, Suwon Kim. GNG4 is a candidate G-proteinγ-subunit downstream of the Cxcl10/Cxcr3 axis that mediates cell migration in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2426.