Effect Of MiR-155 Inhibition Prevented On Breast Cancer Stem Cell-like Properties

Breast cancer is the most common malignant tumor of women worldwide,and its occurrence and development are regulated by many factors.At present,the characteristics of cancer stem cells(CSCs)play an important role in tumor recurrence,metastasis and drug resistance.MicroRNAs,a type of small non-coding RNA molecules,play different roles in the whole process of the occurrence and development of tumor,they can be used as a tumor suppressor gene or an oncogene,while miRNAs themseleves can also mutate or be deleted,thereby affecting the expression of genes related to the abnormal occurrence.MiR-155 was first detected in B lymphocytes and increased in many tumor cells and serum/plasma,such as breast cancer,lung cancer and other solid tumors.Although miR-155 expression level has been found being highly expressed in breast cancer tissues and serum,the function and applied value of miR-155 are not well understood.In recent years,it has been proved that cancer stem cells are closely related to tumor occurrence,development,metastasis,recurrence and drug resistance.Some studies have found that some miRNAs play an essential role in breast cancer stem cells,such as miR-142 through Wnt signaling pathway to promote the formation of breast cancer stem cells.MiR-205 mediated downregulation of ErbB receptor in breast cancer stem cells,leading to cancer stem cells resistance to chemotherapy.E12/E47 can upregulate the expression of miR-495 in breast cancer and promote the development of tumor and hypoxia tolerance.Since little related,evidence has been reported,we don't know whether miR-155 plays a crucial role in breast cancer stem cells.Therefore,it is of great importance to study the role of miR-155 in the occurrence and development of breast cancer.Objective To investigate the effect of miR-155 on the characteristics of breast cancer stem cells,and to explore whether miR-155 can serve as a molecular target for the treatment of breast cancer.At the same time,to detect the expression of miR-155 in the tissues and serum of breast cancer and its relationship with clinicopathology,and explored the possibility of miR-155 as a biomarker for the diagnosis,curative effect monitoring and prognosis evaluation of breast cancer.Method Using serum-free culture technique,detected the expression level of miR-155 in MDA-MB-231 adherent cells and tumor sphere,respectively;After transfection with Hsa-miR-155-inhibitor in the MDA-MB-231 cell line,the colony formation and tumor-sphere formation capacity of MDA-MB-231 was examined by soft agar colony formation assay and tumor-sphere forming experiment,respectively;Stem cell specific genes of ABCG2?CD44?CD90 and CD24 expression were examined by FQ-PCR assay in tumor-spheres and monolayer cells.Breast cancer cell(MDA-MB-231)proliferation changing to DOX resistance was determined by MTT method after tansfected Hsa-miR-155 inhibitor;Detected the tumor size by nude mice into tumor experiment;The miR-155 and miR-205 expression levels in breast cancer tissue and serum were detected by FQ-PCR assay,and analyzed the relationship between its expression and clinical pathological data;the diagnosis value of miR-155 and miR-205 in the breast cancer were analyzed by ROC curveResults miR-155 expression significantly enhanced in MDA-MB-231 tumor-sphere(p<0.05);Tumor cell clones significantly decreased after transfected Hsa-miR-155 inhibitor(p<0.01,p<0.05);ABCG2,CD44,CD90 gene mRNA expression were significantly decreased(p<0.01),but CD24 expression decreased(p<0.01);The cells proliferation were inhibited by co-culture with DOX,its inhibition rate increased from 20.23%to 68.72%(p<0.001).MDA ?MB-231 cells after transfected Hsa-miR-155 inhibitor in nude mice subcutaneous tumors grew in 12,15,18 and 21 days were much smaller than control group cells growth of tumors(p<0.05).In breast cancer patients,she expression of miR-155 was up-regulated while miR-205 was down-regulated in breast cancer tissue and serum(p<0.01,p<0.05).Moreover,the comparison with the clinicopathologic data of the breast cancer patients showed that increased levels of miR-155 was significantly associated with tumor size,lymph node metastasis and the expression status of Her2,ER/PR(p<0.05),while the expression of breast cancer and of miR-205 have no significant correlation with the pathological grading of breast cancer;ROC curve analysis showed that the diagnostic efficiency of miR-155 and miR-205 are:miR-155>miR-155>tissue plasma plasma miR-205>miR-205.Conclusion:miR-155 plays an important role in the formation of breast cancer stem cells.The expression of miR-155 is positi-vely correlated with the formation of breast cancer stem cells.miR-155 may be a new molecular target for the treatment of breast cancer.miR-155 is a promising biomarker in breast cancer diagnosis,efficacy monitoring and prognostic evaluation.