Interferon consensus sequence binding protein (ICSBP) is a transcription factor induced by interferon gamma (IFN-γ) and a member of the interferon regulatory factor (IRF) family. ICSBP is predominantly expressed in hematopoietic cells and regulates the immune response and cell growth and differentiation. However, little is known about its function in non-hematopoietic cells. Here we show a novel function for ICSBP in epithelial to mesenchymal transition (EMT)-like phenomena (ELP), cell motility, and invasion in human osteosarcoma cell lines, including U2OS cells. IFN-γ treatment induced ICSBP expression and EMT-like morphological change in U2OS cells, which were suppressed by ICSBP knock-down. To further investigate the role of ICSBP in ELP, we established a stable U2OS cell line that overexpresses ICSBP. ICSBP expression caused U2OS cells to have a more elongated shape and an increased vimentin and fibronectin expression. ICSBP expression also promoted adhesiveness, motility, and invasiveness of U2OS cells. ICSBP up-regulated transforming growth factor (TGF)-β receptors and activated TGF-β signaling cascades, which were responsible for ELP as well as increased cell motility and invasion. In addition, ICSBP-induced TGF-β receptor activation resulted in the up-regulation of Snail. Knock-down of Snail attenuated the ICSBP-induced augmentation of cell motility and invasion. Up-regulation of Snail, ELP, and increased invasion by ICSBP expression were also observed in other osteosarcoma cell lines, such as Saos-2 and 143B. Furthermore, ICSBP and TGF- β receptor I were expressed in 45/54 (84%) and 47/54 (87%) of human osteosarcoma tissues, respectively, and showed significant correlation (r= 0.47, p= 0.0007) with respect to their expression levels. Taken altogether, these data demonstrate a novel function for ICSBP in ELP, cell motility, and invasion through the TGF-β and Snail signaling pathways

Citation Format: Jee Young Sung, Seog-Yun Park, June Hyuk Kim, Hyun Guy Kang, Jong Hyung Yoon, Yoon Sook Na, Yong-Nyun Kim, Byung-Kiu Park. Interferon consensus sequence binding protein (ICSBP) promotes epithelial to mesenchymal transition (EMT)-like phenomena, cell motility, and invasion via TGF-β signaling in U2OS cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4996. doi:10.1158/1538-7445.AM2014-4996