MicroRNA-134 targets KRAS to suppress breast cancer cell proliferation, migration and invasion

Abstract

The expression patterns and functions of microRNA-134 (miR-134) have been previously studied in numerous types of cancer. To the best of our knowledge, this is the first study of miR-134 in human breast cancer. In the present study, the expression patterns, biological functions and underlying molecular mechanisms of miR-134 in human breast cancer were investigated. Reverse transcription-quantitative polymerase chain reaction evaluated the expression of miR-134 in human breast cancer tissues, matched normal adjacent tissues, breast cancer cell lines and a normal mammary epithelial cell line. Following transfection with miR-134, an MTT assay, cell migration assay, cell invasion assay, western blot analysis and a luciferase assay were performed on the MCF-7 and MDA-MB-231 human breast cancer cell lines. The findings revealed that miR-134 expression levels were significantly downregulated in breast cancer cells. Statistical analysis demonstrated that low expression of miR-134 was significantly associated with lymph node metastasis, TNM stage and reduced cell differentiation. It was observed that miR-134 inhibited the growth, migration and invasion of breast cancer cells. Additionally, the present study indicated that miR-134 may directly target the Kirsten rat sarcoma viral oncogene homolog in breast cancer tissues. These results suggest that miR-134 may be used as a potential therapeutic biomarker in breast cancers.

Keywords: Kirsten rat sarcoma viral oncogene homolog; breast cancer; microRNA-134; therapy.

Figure 1.

miR-134 expression in breast cancer tissue samples and cell lines. (A) miR-134 expression levels were significantly downregulated in breast cancer tissue samples compared with NATs. (B) miR-134 was significantly downregulated in MCF-7 and MDA-MB-231 breast cancer cell lines compared with the MCF-10A immortalized control cells. miR-134, microRNA-134; NAT, normal adjacent tissue.

Figure 2.

(A) Transfection of miR-134 mimics into MCF-7 and MDA-MB-231 cells significantly increased the expression levels of miR-134. (B) The MTT assay revealed that the upregulation of miR-134 significantly suppressed cell proliferation in MCF-7 and MDA-MB-231 cells. miR-134, microRNA-134; NC, negative control. *P<0.05.

Figure 3.

miR-134 suppressed the migration and invasion of MCF-7 and MDA-MB-231 cells. The migration and invasion assays were performed using transwell chambers. Ectopic miR-134 inhibited the migration and invasion of MCF-7 and MDA-MB-231 cells. miR-134, microRNA-134; NC, negative control.

Figure 4.

KRAS is directly targeted by miR-134. (A) TargetScan determined that KRAS mRNA contained an miR-134 seed match at position 3521–3527 of the KRAS 3′-UTR. (B) The western blot assay revealed that KRAS expression levels were significantly downregulated in MCF-7 and MDA-MB-231 cells following transfection with miR-134. (C) miR-134 significantly inhibited the KRAS Wt, but not the KRAS Mut, luciferase activity in MCF-7 and MDA-MB-231 cells. Wt, wild type; Mut, mutant, KRAS, Kirsten rat sarcoma viral oncogene homolog; miR-134, microRNA-134; UTR, untranslated region; MCF-7 cells, Michigan cancer foundation-7 cells; NC, negative control.