Abstract 1466: Interferon-induced microRNA turnover leading to epithelial-to-mesenchymal transition (EMT) in cancer

Introduction: Interferon-γ (IFN-γ) is a cytokine that has been shown to be associated with antitumor mechanisms during tumor immune surveillance. However, a steady flow of reports suggests that it has pro-tumorigenic effects. In this study, we have investigated the role of IFN-γ in cancer progression and its mechanism of action in regulating microRNA turnover. Methods: Three cell lines from different cancer types (prostate PC-3, renal 786-0 and hepatoma, HepG2) were employed. Luciferase reporter gene assay and real-time RT-PCR were used for examining the IFN-γ-induced gene transcription. Site-directed mutagenesis, in vitro transcription, RNA pull down, and in vitro RNA degradation assays were used for determining miRNA biogenesis. Western blot assay was used to determine EMT marker expression. Transwell assay was used for determining cell migration and invasion. Results: In the presence of IFN-γ, both the migration and invasion of PC-3 increased, which was accompanied with elevated EMT marker (such as Vimentin) as well as factors (such as Slug and ZEB1). IFN-γ is known to induce transcriptional activation of IFN-stimulated genes (ISGs) via JAK-STAT signaling pathway. Subsequently, we identified that IFN-γ could induce interferon-induced tetratricopeptide repeat 5 (IFIT 5) mRNA and protein levels in these cell lines. IFIT5 is first identified as viral RNA binding protein and we recently demonstrate its new function as a post-transcriptional machinery for miRNAs turnover. We therefore screened the potential IFIT5-regulated miRNAs based on microRNA microarray screening and identified several candidates such as miR-101, miR-335, miR-203, miR-128, miR-363, miR-153, miR-146a, miR-125b and miR-200a. We further examine the functional roles of these miRNAs contributing to cancer metastasis. We demonstrated that miR-363 could target Slug to suppress EMT as well as cell migration and invasion. Also, the seed regions of miR-101, miR-335, miR-203 and miR-128 have sequence-matched target sites at the 3’UTR of ZEB1, and Slug mRNA, and we further showed that they could indeed suppress the expression of these EMT factors. Clinically, IFIT5 mRNA level is elevated in higher-grade prostate cancer (PCa), and positively correlated with ZEB1, ZEB2 and Slug in PCa. By knocking down IFIT5, we observed suppression of both ZEB1 and Slug, along with decreased migration motility in these cells. Taken together, our data demonstrate the pro-progression role of IFN-γ in different cancer types. Conclusion: IFN-γ can potentiate cancer progression by inducing EMT, which is mediated through IFIT5-mediated miRNA turnover. IFIT5 complex represents unique machinery for the turnover of a specific population of tumor suppressor miRNAs. Citation Format: U-Ging Lo, Rey-Chen Pong, Jer-Tsong Hsieh, Leah Gandee. Interferon-induced microRNA turnover leading to epithelial-to-mesenchymal transition (EMT) in cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1466.