Analysis Of The Role Of MiR-188-5p In Breast Cancer Diagnosis And Its Function

Objective: To exploer the role of circulating mi R-188-5p in the diagnosis of breast cancer and to clarify the regulatory role and molecular mechanism of miR-188-5p in breast cancer.Methods: Serum samples were collected from 50 healthy people,40 breast fibroma patients and 45 breast cancer patients before and after operation.miRNAs were extracted from serum of each group.The expression levels of miR-188-5p in serum of each group was detected by qRT-PCR.The circulating levels of miR-188-5p among healthy controls,breast fibroma patients and breast cancer patients before operation were compared.The relationship of miR-188-5p expression levels in serum from breast cancer before operation with clinicopathological parameter were analyzed.Diagnostic value of serum miR-188-5p in breast cancer were analyzed by ROC curve analysis.The miR-188-5p levels in serum before and after operation were compared to analyze the role of mi R-188-5p in the observation of surgical efficacy.qRT-PCR was used to detect and compare the expression of mi R-188-5p in breast cancer cells MAD-MB-231 and MCF-7.mi RNA mimics and inhibitor were transfected into different breast cancer cells respectively.Transwell migration assay and plate clony formation experiment were used to observe the effects of mi R-188-5p on the proliferation and migration of breast Cancer cells.Meanwhile,the exosome from corresponding cancer cells were determined by qRT-PCR.Target gene prediction and luciferase reporter gene detection were used to determine the target genes of miR-188-5p.The target gene mRNA and protein expression levels tested in breast cancer cells and the immunohistochemical analysis of target gene protein in clinical tissue sections were used to verify the target gene regulated by miR-188-5p.Results: The levels of serum miR-188-5p were significantly gradually increased from the healthy control group,breast fibroma group to breast cancer group.Compared with the levels of miR-188-5p in the pre-operative serum,miR-188-5p levels were significantly reduced in the post-operative serum.The pre-operative serum miR-188-5p levels were related with axillary lymph node metastasis,tumor stage and ki67 expression in breast cancer.The AUC value of ROC curve analysis for the serum miR-188-5p levels in differentiating non-breast cancer(healthy populationand breast fibroma)from breast cancer is 0.894(95%CI:0.840-0.947)and the cut off value was 1.000;In differentiating breast cancer from breast fibroma,the AUC value of ROC curve was 0.814(95% CI: 0.727-0.902)and the Cut off value was 0.995.The expression of miR-188-5p in MDA-MB-231 was significantly lower than that in MCF-7.Overexpression of miR-188-5p in MDA-MB-231 by transfection with miRNA mimics could inhibit the proliferation and migration of breast cancer cells.On the contrary,knock down of miR-188-5p in MCF-7 by transfection with mi R-188-5p inhibitor could promote the proliferation and migration of breast cancer cells.MDA-MB-231 derived exosome was highly enriched in mi R-188-5p when compared with exosome secreted by MCF-7.Target gene prediction and luciferase reporter gene detection confirmed that IL6 ST is the downstream regulatory target gene of miR-188-5p.Overexpression of miR-188-5p decreased the expression levels of IL6 ST mRNA and protein in MDA-MB-231,while miR-188-5p knock down increased the expression levels of IL6 ST m RNA and protein in MCF-7.The expression levels and positive rate of IL6 ST in breast cancer with lymph node metastasis were higher than those in breast fibroadenoma and breast cancer without lymph node metastasis.Conclusions: Circulating miR-188-5p may be a new noninvasive molecular marker for diagnosis of breast cancer.miR-188-5p plays a role as a tumor suppressor gene in breast cancer,and it may regulate the proliferation and migration of breast cancer cells by targeting IL6ST.