Abstract P1-05-04: miR551b-3p promotes Oncostatin M signaling in breast cancer

An increased expression of oncogenic microRNA miR551b-3p (also known as miR551b) occurs in a subset of breast cancer due to genomic amplification of 3q26.2 locus. Using in silico and clinical sample analysis of breast cancer patient datasets, we identified that those breast cancer samples that encompass miR551b amplification express high levels of STAT3 mRNA and Oncostatin (OSM) family genes in triple-negative breast cancer (TNBC). Furthermore, high expression of Oncostatin family genes associates with poor outcome in estrogen receptor- negative breast cancer patients. In this study, we identified a previously unexplored mechanism that miR551b-3p promotes breast cancer progression and tumor growth by direct interaction of miR551b-3p with STAT3 promoter thereby activating STAT3 transcription. As a consequence, STAT3 upregulates a cytokine Oncostatin and its receptor Oncostatin M receptor (OSMR) and their interaction further induces STAT3 phosphorylation and an autocrine self-reinforcing loop in TNBC cells. In this study, we demonstrate that overexpression of miR551b-3p promoted proliferation, invasion and migration, epithelial to mesenchymal transition (EMT) and spheroid formation of breast cancer cells and its inhibition decreased the expression of miR551b-3p by inhibiting OSM, OSMR, IL6ST, IL31RA, phosphorylated and total STAT3 in breast cancer cells and reduced tumor cell growth. Overall, our results provide the first evidence that miR551b regulates OSM family gene expression by activating STAT3 and thereby promoting tumor cell growth and metastasis in breast cancer cells. Therefore, targeting miR-551b-3p-STAT3-OSMR axis and inhibiting their levels will provide an unprecedented therapeutic opportunity in breast cancer. Citation Format: Anjali Geethadevi, Deepak Parashar, Miriam Ragle Aure, Jasmine George, Changliang Chen, Jyotsna Mishra, Andliena Tahiri, Bindu Nair, Amadou Camara, Vessela N Kristensen, Sunila Pradeep, Pradeep Chaluvally Raghavan. miR551b-3p promotes Oncostatin M signaling in breast cancer [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 P1-05-04.