Pleiotropic Anti-Cancer Effects Of Sting In Estrogen Receptor Positive Breast Cancer Cells.

Abstract Purpose: Stimulator of interferon genes (STING) is an upstream regulator of interferon and NF-κB, the key mediators of immune and inflammatory responses associated with cancer, triggered by cytosolic DNA. Downregulation of STING in breast tumor tissues has been reported. STING elicits caspase-8-dependent cell apoptosis via NF-κB in breast cancer cells. STING agonists are considered as potent anti-cancer agents. The current study aims to assess the biological functions of STING in breast cancer progression. Experimental design: Data of mRNA expression levels and recurrence-free survival in patients with breast cancer from The Cancer Genome Atlas and Kaplan Meier-plotter databases were analyzed. Transwell assays were used to evaluate cell migrated and invaded abilities. Sphere formation was performed in stem cell-selective medium and ultra-low attachment plates. Two STING agonists, ADU-S100 and diABZI STING agonist-1 trihydrochloride, were used for in vitro studies. The molecular events were examined by Western blot analysis. Results: Data from public database showed that lower transcripts levels of STING in Her2 and luminal B breast cancer tissues than normal breast tissues. Luminal-type breast cancer cell lines harbored low STING transcripts compared with other subtypes. Importantly, breast cancer patients with low expression levels of STING was associated with worse recurrence-free survival. Results of immunoblotting indicated that breast cancer cell lines have lower STING protein expressions than normal MCF10A cells. Knockdown of STING led to aggressive phenotypes of MCF10A and BT474 cells. In contrast, overexpression of STING suppressed the abilities of migration, invasion and sphere formation of MCF7 and BT474 cells. The markers of epithelial were increased while the markers of mesenchymal and stemness were decreased by STING overexpression. STING agonist slightly suppressed cell viability of breast cancer cells but not MCF10A cells. Treatment of STING agonists reduced cell migrated ability with upregulation of E-cadherin and γ-catenin. Conclusion: These findings suggest that STING serves tumor-suppressive effects in breast cancer. Citation Format: Chun-Yu Liu, Ji-Lin Chen, Chun-Teng Huang, Pei-Yi Chu, Mei-Fang Tseng, Yu-Hsuan Lee, Wan-Lun Wang, Ling-Ming Tseng. Pleiotropic anti-cancer effects of STING in estrogen receptor positive breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2486.