MicroRNA-7 agomir is a potential bioactive material for breast cancer therapy by inhibiting breast cancer stem cell tumorigenicity

Abstract

Breast cancer stem cells (BCSCs) have been proven to be the root of development, metastasis and recurrence of breast cancer. It is crucial to explore the underlying paths of regulating BCSCs for breast cancer treatment. Many bioactive materials have been developed to modify therapeutic drugs or as drug delivery vehicles for tumor treatment. In this study, we aimed to probe the effect of microRNA-7 (miR-7) agomir, a potential bioactive material, in breast cancer treatment by reducing tumorigenicity of BCSCs. Magnetic activated cell sorting was used to isolate the BCSCs from the MDA-MB-231 and LD cells. Protein array was performed to screen differentially expressed proteins. The expression levels for miR-7 and CD44 in human breast cancer cell lines were detected by Quantitative real-time PCR (q-PCR), Western blot (WB) and Flow cytometry (FCM) assays. Lentiviral recombinants were constructed to infect the primary human breast cancer cells to obtain the cells stably overexpressing miR-7. BCSCs xenograft model was established in NOD/SCID mice and the tumor tissues were analyzed by hematoxylin-eosin staining (HE) and immunohistochemistry (IHC). We found that miR-7 agomir can inhibit the tumor growth in mice and the expression of CD44 in the tumor tissues treated with miR-7 agomir was 2.4 times lower than that of control treatment from the protein array results. Among the MDA-MB- 231, MCF-7, SK-BR-3 and LD human breast cancer cell lines, the expression of CD44 was downregulated in the MCF-7 cells with relatively high miR-7 expression. Overexpression of miR-7 effectively reduced the CD44 expression in LD cells. Furthermore, compared with control and chemotherapy treatments, the mouse tumor growth was significantly inhibited in the mice infected with Lenti-miR-7-BCSCs, concomitantly decreasing the CD44 expression in tumor tissues. These findings suggest that miR-7 agomir can be used as a potential bioactive material to inhibit tumor growth in BCSCs xenograft mouse model by downregulating the CD44 expression and reducing BCSCs tumorigenicity.