Abstract P5-05-11: Novel small molecule STAT3 inhibitors induce apoptosis and suppress cell migration and tumor growth in triple-negative breast cancer cells

Persistent STAT3 signaling is frequently detected in many cancer types and thus could potentially serve as a viable therapeutic target. In this study, we tested two novel small STAT3 inhibitors, LLY17 and LLL12B in triple-negative breast cancer cells, which frequently express persistent STAT3 phosphorylation. LLY17 and LLL12B selectively inhibited IL-6-mediated induction of STAT3 phosphorylation but no effect on IFN-γ mediated induction of STAT1 phosphorylation. LLY17 and LLL12B induced apoptosis in triple-negative breast cancer cells but exhibited minimal toxicity toward normal mammary epithelial cells. RNAi attenuation experiments confirmed the requirement of STAT3 for LLY17 and LLL12B-mediated inhibition of cell viability in triple-negative breast cancer cells. LLY17 and LLL12B inhibited STAT3 phosphorylation in human and murine triple-negative breast cancer cells. In addition, LLY17 and LLL12B inhibited cell migration of human and murine triple-negative breast cancer cells. Furthermore, LLY17 and LLL12B suppressed tumor growth and STAT3 phosphorylation of triple-negative breast cancer cells in vivo in a mammary fat pad murine syngeneic mouse model. Together, our findings suggest that targeting persistent STAT3 signaling pathway by novel oral bioavailable small molecules LLY17 and LLL12B may be a potential approach for the therapy of triple-negative breast cancer. Citation Format: Li Pan, Xiang Chen, Shengling Fu, Chenglong Li, Hui-Wen Lo, Jiayuh Lin. Novel small molecule STAT3 inhibitors induce apoptosis and suppress cell migration and tumor growth in triple-negative breast cancer cells [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-05-11.