The Tissue Expression Of MiR-155 And MiR-21 In Breast Cancer

Background: MicroRNAs (miRNAs) are an abundant class of 20～22 nucleotide small noncoding, evolutionary conserved RNA molecules that negatively regulate gene expression through sequence-specific translational repression and/or degradation of cognate mRNA. MicroRNAs have been implicated in control of many fundamental cellular and physiological processes. Mounting evidence indicates that their aberrant expression might be involved in human cancers, and they might be useful for diagnosis and therapeutics in cancer. To understand the roles of miRNAs and their potential therapeutic use in breast cancer, in this study, we analyzed the expression of miR-155 and miR-21 in 38 breast cancer samples. The analysis may find miRNAs as new cancer biomarkers that could be useful for diagnosis and therapeutics in breast cancer.Methods: To investigate the expression deregulation of miR-155 and miR-21 in breast cancer, we collected 38 sets of breast cancer samples at Zhongshan Hospital, including tumor tissue, adjacent tumor tissue and normal breast tissue. The clinical information of patients was also recorded. We grouped patients by biopathologic features. Total RNA isolation was done with TRIzol according to the instructions of manufacturer. RT-PCR and TaqMan quantitative real-time PCR were used to quantify the expression levels of miR-155 and miR-21. Statistical comparisons were done by SPSS11.5 software to evaluate whether differentially expression of miR-155 and miR-21 in various biopathologic features associated with tumor specimens.Results: We found that the expression of miR-155 and miR-21 in tumor tissue was significant different from that in normal breast tissue. The expression level of miR-155 increased gradually from normal tissue to adjacent tumor tissue and to tumor tissue. Moreover, the expression level of miR-155 in tumor and adjacent tumor tissue in CerbB-2 positive group was higher than that in CerbB-2 negative group. Whereas, the tumor size, pathologic type and differentiation, tumor stage, lymph nodes metastasis, estrogen receptor, progesterone receptor or p53 did not contribute to any significant difference in miR-155 and miR-21 expression levels. In addition, we found miR-155 and miR-21 levels were lower in the patients who received neoadjuvant chemotherapy, but it showed non statistical distinction since we only collected small number of samples with neoadjuvant chemotherapy in our researches.