miR‐10b expression in breast cancer stem cells supports self‐renewal through negative PTEN regulation and sustained AKT activation

摘要

Cancer stem cells (CSCs) are linked to metastasis. Moreover, a discrete group of miRNAs (metastamiRs) has been shown to promote metastasis. Accordingly, we propose that miRNAs that function as metastatic promoters may influence the CSC phenotype. To study this issue, we compared the expression of 353 miRNAs in CSCs enriched from breast cancer cell lines using qRT–PCR analysis. One of the most altered miRNAs was miR‐10b, which is a reported promoter of metastasis and migration. Stable overexpression of miR‐10b in MCF‐7 cells (miR‐10b‐OE cells) promoted higher self‐renewal and expression of stemness and epithelial–mesenchymal transition (EMT) markers. In agreement with these results, inhibiting miR‐10b expression using synthetic antisense RNAs resulted in a decrease in CSCs self‐renewal. Bioinformatics analyses identified several potential miR‐10b mRNA targets, including phosphatase and tensin homolog (PTEN), a key regulator of the PI3K/ style="fixed-case">AKT pathway involved in metastasis, cell survival, and self‐renewal. The targeting of style="fixed-case">PTEN by miR‐10b was confirmed using a luciferase reporter, style="fixed-case">qRT– style="fixed-case">PCR, and Western blot analyses. Lower style="fixed-case">PTEN levels were observed in style="fixed-case">CSCs, and miR‐10b depletion not only increased style="fixed-case">PTEN mRNA and protein expression but also decreased the activity of style="fixed-case">AKT, a downstream style="fixed-case">PTEN target kinase. Correspondingly, style="fixed-case">PTEN knockdown increased stem cell markers, whereas style="fixed-case">AKT inhibitors compromised the self‐renewal ability of style="fixed-case">CSCs and breast cancer cell lines overexpressing miR‐10b. In conclusion, miR‐10b regulates the self‐renewal of the breast style="fixed-case">CSC phenotype by inhibiting style="fixed-case">PTEN and maintaining style="fixed-case">AKT pathway activation.