Circular RNAs (circRNAs), a novel type of noncoding RNAs (ncRNAs), have been shown to be implicated in biological processes including cancer as gene expression regulators. However, the roles of circRNAs in cancer stem cells (CSCs) have been unexplored. In the present study, we screened the circRNA profile in breast cancer stem cells (BCSCs) using RNA-Sequencing. Here, 27 circRNAs were found to be aberrantly expressed. Of these, 19 circRNAs were downregulated and 8 were upregulated and some of these circRNAs were validated by Q-PCR. Furthermore, we constructed the circRNA/miRNA network by bioinformatics approaches and hypothesized that circRNAs might be involved in stemness of BCSCs via serving as miRNA sponges. Importantly, we found that circular RNA VRK1 (circVRK1) could suppress BCSC's expansion and self-renewal capacity. Collectively, the present work provides the first reported evidence of the circRNA profile and circRNA/miRNA interplay in BCSCs. In addition, these findings lay foundation to explore the functions of circRNAs in CSCs and indicate that circVRK1 might be a promising target for BCSCs.
Keywords: RNA-sequencing; breast cancer stem cells; circVRK1; circular RNA.