MicroRNA-3941 targets IGF-1 to regulate cell proliferation and migration of breast cancer cells

Abstract

We aimed to investigate the effects and regulatory mechanism of microRNA-3941 (miR-3941) in the progression of breast cancer. The expression of miR-3941 and insulin-like growth factor 1 (IGF-1) was determined in breast cancer tissues and cell lines. A miR-3941 mimics, inhibitor, and scramble RNA were individually transfected into the cancer cells. Then, the effects of overexpression and suppression of miR-3941 on cell viability, migration, and invasion, as well as on the expression of epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, N-cadherin, and vimentin) were further investigated. In addition, luciferase reporter analysis was performed to confirm whether IGF-1 was the potential target of miR-3941. Small interfering RNA targeting IGF-1 was transfected into the cells to further investigate whether miR-3941 regulated the breast cancer cell migration and invasion by targeting IGF-1. The inverse expression of miR-3941 (downregulated) and IGF-1 (upregulated) was observed in the breast cancer tissues and cells. The overexpression of miR-3941 significantly inhibited the breast cancer cell viability and suppressed cell migration and invasion. In addition, IGF-1 was confirmed as the target of miR-3941, and IGF-1 expression was negatively regulated by miR-3941. The knockdown of IGF-1 significantly reversed the inhibitory effects of miR-3941 overexpression on cell migration, invasion, and the EMT-related proteins. Our results indicate that miR-3941 is downregulated in breast cancer cells, and the downregulation of miR-3941 may promote breast cancer cell proliferation, migration, and invasion through not targeting IGF-1 expression. miR-3941 and IGF-1 may serve as diagnostic markers or potential targets for breast cancer treatment.

Keywords: Breast cancer; cell invasion; cell migration; cell proliferation; insulin-like growth factor 1; microRNA-3941.

Figure 1

The inverse expression of miR-3941 and IGF1 in breast cancer tissues and cells. A: The expression of miR-3941 in breast cancer tissues and their adjacent normal tissues. B: The expression of miR-3941 in breast cancer MDA-MB-231 cells and normal breast MCF-10 cells. C: The expression of IGF1 in breast cancer tissues and their adjacent normal tissues. D: The expression of IGF1 in breast cancer MDA-MB-231 cells and normal breast MCF-10 cells. Error bars indicate means ± SD. *, P < 0.05 and **, P < 0.01.

Figure 2

The effects of miR-935 on cell proliferation. A: The expression of miR-3941 in different transfection groups. B: MTT assay showing the cell viability of different transfection groups. C and D: Colony assay showing the number of the colony of different transfection groups. Error bars indicate means ± SD. *, P < 0.05 and **, P < 0.01 (compared with control group).

Figure 3

The effects of miR-935 on cell migration and invasion. A and B: Transwell assay showing the number of migrated cells in different transfection groups. C and D: Transwell assay showing the number of invaded cells in different transfection groups. E and F: The expression levels of E-cadherin, N-cadherin, and vimentin in different groups determined by qRT-PCR and western blot. Error bars indicate means ± SD. *, P < 0.05 and **, P < 0.01 (compared with control group).

Figure 4

IGF1 was a direct target of miR-3941. A: The results predicted by TargetScan (http://www.targetscan.org/). B: Luciferase report assay showing that miR-3941 can directly target the 3’UTR of IGF1. C: The expression of IGF1 in different transfection groups as determined by qRT-PCR. D: The expression of IGF1 in different transfection groups as determined by western blot. Error bars indicate means ± SD. *, P < 0.05 and **, P < 0.01 (compared with the control group).

Figure 5

The effects of IGF1 on the migration and invasion of breast cancer cells. A and B: The expression of IGF1 after si-IGF1 treatment. C and D: Transwell assay showing the number of migrated cells in different groups. E and F: Transwell assay showing the number of invaded cells in different groups. G and H: The expression levels of E-cadherin, N-cadherin, and vimentin in different groups. Error bars indicate means ± SD. *, P < 0.05 and **, P < 0.01 compared with the control group. #: P < 0.05 compared with Inhibitor group.