We have previously demonstrated that an oncogenic microRNA miR551b-3p (also known as miR551b) regulates STAT3 transcription thereby enhancing tumor growth and metastasis in ovarian cancer. Herein, we have identified that Oncostatin M (OSM) is upregulated through STAT3-driven transcription, which plays an important role in promoting migration and invasion of breast cancer cells. The purpose of this study was to evaluate the role of miR551b mediated STAT3 activation and the precise mechanism that regulates OSM-Receptor (OSMR) signaling for breast cancer growth and metastasis. MDA-MB231 cells were either overexpressed or silenced with miR551b and anti-miR551b respectively and the effects on proliferation, migration/invasion (Matrigel transwell assay), wound healing and expression of OSMR and its downstream targets (Western blotting, Quantitative RT-PCR) were assessed. Our data demonstrate that miR551b promoted survival, proliferation, invasion and migration and epithelial to mesenchymal transition (EMT) and spheroid formation of breast cancer cells. Our results also show that miR551b-mediated STAT3 activation upregulated the components of OSMR signaling through elevated expression of OSMR, Interleukin 31 receptor-alpha (IL31RA) and their ligands Oncostatin (OSM) and IL31 thereby inducing phosphorylation of STAT3 for tumor cell proliferation, migration and invasion. Conversely, anti-miR551b reduced the expression of OSMR, IL31R and their ligands OSM and IL31 as well as the phosphorylation of STAT3. Briefly, our results provide the first report indicating that miR551b regulates OSMR expression by activating STAT3 and thereby promoting tumor cell growth and metastasis in breast cancer cells through autocrine feed-forward signaling loop.

A.G, D.P., contributed equally.

Citation Format: Anjali Geethadevi, Deepak Parashar, Miriam Ragle-Aure, Bindu Nair, Yiling Lu, Vessela N. Kristensen, Ming You, Anil K. Sood, Gordon B. Mills, Sunila Pradeep, Pradeep Chaluvally Raghavan. MiR551b-mediated Oncostatin M signaling in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4423.