MicroRNA sequencing detects miR-424-5p up-regulation in ovarian cancer stem cells

Cancer stem cells (CSCs) are cancer cells that possess the ability to undergo continuous proliferation and self-renewal. It has been postulated that CSCs are responsible for tumor growth, heterogeneity, invasion, metastasis, and recurrence. MicroRNAs (miRNAs), small non-coding RNAs of approximately 22 nucleotides, are known to be involved in the maintenance of CSCs. To gain insight into the role of miRNAs in CSCs, we investigated the differential expression of miRNAs in ovarian CSCs compared to non-CSCs. Ovarian CSCs were isolated from the human ovarian cancer cell line SK-OV-3 using two ovarian CSC-specific surface markers, CD44 and CD117. The expression levels of miRNAs in CSCs and non-CSCs were estimated by miRNA sequencing. We detected four up-regulated miRNAs (miR-29a-5p, miR-34c-5p, miR-106a-5p, and miR-424-5p) in ovarian CSCs, and miR-424-5p was validated by real-time qPCR. MiR-424-5p target genes were predicted using several validated target databases and computational algorithms. Pathway analysis indicated that most miR-424-5p target genes are involved in cancer-related biological pathways. Overall, these results suggest that miR-424-5p is a potential regulator of CSCs that endows human ovarian tissue with tumorigenic potential and thus represents a potential therapeutic target for human ovarian cancer.