Abstract: Objective To look for better and low cost method for extracting microRNAs ( miRNAs)from paraffin-embedded tissue for miRNA diagnosis or other miRNAs assay. Methods The samples were collected from paraffin-embedded human breast cancer tissue stored over two years and MMTV transgenic mouse paraffin-embedded breast tissue over six months. The miRNAs extract paraffin tissue kit served as control. To detect the quality of miRNAs obtained by these two methods,used 2% gel electrophoresis and the OD value to confirm the quality and concentration. Furthermore,verified miRNAs by testing miRNA-375 and miRNA-218 with quantitative PCR. Results ①miRNAs extracted by our method met the experimental requirements( A260/280=1. 86-2. 21OD),and the lowest concentration was 38. 50mg/L.②The quantitative PCR can detect miRNAs and its copies number compared with the control,the difference was no significant(P﹥0. 05).③This method has relatively lower cost,about 1/10 cost of kit method,while the extraction process decreased about 1/3 time. Conclusion The method we optimized for extracted miRNAs from paraffin-embedded tissue is feasible,it provides a convenient experimental method,and a better approach to detect more retrospective specimens of paraffin-embedded tissue samples.

Key words: paraffin-embedded tissue, microRNA, extraction, breast cancer