Study On The Predictive Value Of MiRNA-345/621of Response To Breast Cancer Neoadjuvant Therapy

PART I Identifying microRNA of predicting drug sensitivity by microarray gene expression profiling and bio-statistical methodObjective:The aim of this study was to explore microRNAs of response to breast cancer PCb regimen neoadjuvant chemotherapy by using microarray gene expression profiling and biometric information software.Methods:All patients received preoperative chemotherapy by the regimen of paclitaxel and carboplatin (6pCR patients VS25non-pCR patients). Gene expression profiling of breast cancer were obtained by Human Genome GeneChip Plus U1332.0Array. By using Significance Analysis of Microarrays (SAM), a set of differnet expression genes was identified between pCR patinets and non-pCR patients. Hierachical Clustering Analysis was applied to predict the response of breast cancer PCb neoadjuvant chemotherapy. To validated the accuracy of microarray gene expression profiling by qRT-PCR method in another independent group.To predict miRNAs which regulated the DEGs expression by using CORNA software. Furthermore, we tested the expression levels of miR-345and miR-621in the independent group by using qRT-PCR.Results:6patients as pCR and25patients as non-pCR showed significant different expression levels for231genes by Significance Analysis of Microarrays (SAM). The upregulated differential expression genes in patient with pCR response were tested by CORNA software to know the significant target-association microRNA miR-345/621. Independent validated group showed that overexpression of miR-621and miR-345in breast cancer tissue may leads to be sensitive to PCb regimen neoadjuvant chemotherapy and easily to achieve pCR.Conclusion:These data suggest the possibility that microarray gene expression profiling may be useful in predicting response of locally advanced breast cancer to neoadjuvant chemotherapy and helpful in individualized therapy. miR-621and miR-345may regulate cancer cell sensitivity to chemotherapeutic agents. PART II The study of miR-345/621regulate drug sensitivity and the screening of miR-621target genesObjective:In this study, we investigated the influence of miR-345/621on drug sensitivity regulation of breast cancer PCb regimen neoadjuvant chemotherapy. To predict and verify the target genes of miR-621and to evaluate the potential mechanism of miR-621in drug sensitivity regulation.Methods:Using the breast cancer cell lines MDA-MB-231.MDA-MB-231HM and MCF-7as experimental material, cell culture, cytotoxicity assay,cell plus drug assay, cell transfection were used to analyze the potential influence of miR-345and miR-621on drug sensitivity regulation.. The potential target genes of miR-621were selected by TargetScan and miRanda software. Potential target genes of miR-621were also selected according to microarray analysis. Subsequently, qRT-PCR and western blot assays were used to further verify the candidate targets of miR-621in breast cancer cell lines.Results:Altered miR-621expression was found in breast cancer cell lines which treated with PTX and CBP. Decreased expression level of miR-621may leads to resistant to PTX and CBP in breast cancer cell lines. The overexpression of miR-621and miR-345resulted in a significant sensitivity to PTX and CBP treatment. Moreover, we found that miR-621may regulate the expression of the multidrug resistance1(MDR1) gene, a crucial factor in drug resistance, and this interaction may have an important functional consequence in the regulation of cancer cell sensitivity to chemotherapeutic agents.Conclusion:Collectively, miR-621and miR-345may play important roles in breast cancer drug sensitivity regulation. Furthermore, miR-621may regulate the expression of the multidrug resistance1(MDR1) gene, a crucial factor in drug resistance.