Abstract 3355: Identification of a novel network of miRNAs that regulate stemness in colorectal cancer

Background and Aims: Accumulating evidence suggests that a subset of cancer cells also known as the “cancer stem cells” (CSCs) influence various clinical outcomes in cancer, including tumor recurrence, metastasis and resistance to chemotherapy. Recently stemness has been recognized as a dynamic state governed by epigenetic modifiers including miRNAs. Despite identification of several self-renewal associated miRNAs, miRNA profile of CSCs remains unclear. Herein, we characterized miRNA expression of CSCs with high vs. low CD44v6 expression through RNA-Seq. Subsequently, we investigated the clinical significance of a novel miRNA identified from this systematic discovery approach. Methods: Colorectal CSCs from HCT116 and HT29 cells were grown as spheroid-derived cancer stem cells (SDCSCs). CD44v6+ and CD44v6- CSCs were subdivided by FACS and characterized by small RNA-Seq. Differentially expressed miRNAs were subsequently confirmed in CD44v6+ CSCs and chemoresistant cells. The expression of one such candidate, miR-1246, was assessed in a clinical cohort (n = 144) by qRT-PCR. Results: MiRNA profiling identified a unique overall pattern of CD44v6+ SDCSCs indicative of high self-renewal capacity. We noted that a panel of established self-renewal suppressive-miRNAs were downregulated (including miR-34a, 101 and 200 family) in CD44v6+ CSCs, and discovered upregulation of previously unreported miRNAs (miR-1246, 3605, 3182 and 4284). KEGG pathway analysis indicated that these miRNAs regulate Akt-MAPK and Wnt signaling pathways. Subsequently, we selected miR-1246 and validated its expression in CD44v6+ SDCSCs and chemoresistant cells. Clinically, the expression of miR-1246 was significantly elevated in CRC tissues compared to corresponding normal mucosa, and this occurred in a stage-dependent manner in primary CRCs. Furthermore, the expression of CD44v6 positively correlated with miR-1246 in CRC tissues. High miR-1246 expression resulted in poor disease free and overall survival. Conclusion: Using a systematic and comprehensive approach, we have identified a unique network of dysregulated miRNAs in CD44v6 CSCs indicative of high degree of stemness features in cancer. In particular, we identified miR-1246 to be frequently overexpressed in CSCs as well as chemoresistant cells and its expression was associated with poor prognosis in CRC patients. Collectively, we have identified a unique group of previously unreported miRNAs which appear to have important mechanistic roles in CSCs and could serve as a promising predictive biomarkers for recurrence and prognosis in patients with CRC. Citation Format: Shusuke Toden, Takatoshi Matsuyama, Elizabeth Hutchins, Kendall Jensen, Ajay Goel. Identification of a novel network of miRNAs that regulate stemness in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3355. doi:10.1158/1538-7445.AM2017-3355