The Screening Of Invasion-related MiRNAs In Breast Cancer Cell And The Preliminary Study On Biological Function Of Hsa-miR-339-5p

Background MicroRNAs (miRNAs) are non-protein coding single-stranded small molecule RNAs, they are widely in eukaryotes and they regulate gene expression by inhibiting or cutting degradation. MiRNAs play diversitive and key biological function in the of the body, not only involved in embryonic development, fat metabolism, cell proliferation, differentiation ,apoptosis and other processes, but also related to the occurrence and development of a variety of tumors.The existing research suggests that the abnormal expression of some miRNAs with unfavorable prognosis in breast cancer. Thus, the biological function of miRNAs may be have great significance to the diagnosis and treatment of breast cancer.Objective To detect the expression profiles of miRNAs in different invasive breast cancer cell lines, and filter out the miRNAs relative to invasiveness; To detect the expression of miR-339-5p in different invasive breast cancer cell lines, and the relationship between the expression of miR-339-5p and the invasiveness of breast cancer cells was confirmed in vitro experiment; Forecast their possible target genes by application of bioinformatics methods. Methods Weakly invasive breast cancer cell line (MCF-7) and highly invasive breast cancer cell lines (MDA-MB-468 ) were cultured and then the total RNA was extracted from the three cell lines. The expression profiles covering 847 miRNAs in these cell lines were detected with miRNA microarray chips, and the standard was differential expression of miRNAs between different invasive breast cancer cell > 2 folds, then filter out the miRNAs relative to invasiveness; Pick out the significantly down-regulated miR-339-5p and qRT-PCR experiments were used to verify the expression levels of miR-339-5p in MCF-7, MDA-MB-468 and MDA-MB-231 breast cancer cell lines; CCK-8 experiments and transwell invasion assay were used to detect the changes of cell proliferation within 96 hours and the cell invasive ability after transfeting miR-339-5p inhibitors; Forecast the possible target genes of miRNAs relative to the invasiveness of breast cancer cell by application of bioinformatics methods. Results (1) Eighty one miRNAs of differential expression were obtained from MDA-MB-468 comparing to MCF-7, including eighteen up-regulated miRNAs and twelve down- regulated miRNAs. miR-29a, miR-29c, and miR-125b were significantly up-regulated, miR-339-5p and miRNA-365 were significantly up-regulated; (2) Compared with MCF-7, qRT-PCR results showed that the expression levels of miR-339-5p in MDA-MB-468 and MDA-MB-231 were 0.28 and 0.23 repectively. (3) Compared with the control group, the changes of breast cancer cell proliferation activity after transfecting miR-339-5p inhibitors were no significant within 96 hours (P>0.05). (4) Comparing to transfecting negative flourescency miRNA inhibitor and the blank group, the invasiveness of MCF-7 cell was apparently enforced by transfeting miR-339-5p inhibitors(P<0.01); (5) MiR-339-5p has multiple target genes, miR-339-5p may be involved in regulating cell growth, proliferation, differentiation, apoptosis, transcription, signal transduction and other processes. Conclusion (1) MiRNAs expression profiles relative to invasiveness was obtained, and miR-339-5p have much more expression level in low invasive breast cancer cell line than in high invasive breast cancer cell line; (2) MiR-339-5p had no effect on breast cancer cell proliferation activity; (3) MiR-339-5p can inhibit the invasion of breast cancer cells;...