Optimization of extraction and amplification of microRNAs (mir-21, mir-141 and mir-205) in urine samples of patients with bladder cancer

The current methods for bladder cancer diagnosis suffer from low sensitivity and specificity. Therefore, finding a novel tumor markers with high specificity and sensitivity is of great interest. MicroRNAs (miRNA, miR) are small endogenously-produced, non-coding RNAs with an important role in regulating gene expression. Recent studies show that miRNAs expression profiles represent significant tumor-specific changes that are unique for most cancers. The aim of this study was to optimize miRNA containing total RNA extraction from urine and use it as a reliable and repeatable technique for miRNA detection in urine of patients with bladder cancer.

Total RNA was extracted from the urine of patients with bladder cancer and normal individuals using RNX and Trizol solutions with and without modifications of original protocols. Real-time quantitative RT-PCR was then used to detect miRNAs with a potential link to bladder tumorigenesis.

RNX and the modified Trizol are practical methods for RNA extraction from urine samples. The mir-21 amplification of the extracted RNAs using modified Trizol method was more efficient than that of RNX method. It is noteworthy that, the levels of miRNAs expression were much higher in the frozen urines compared to the fresh ones.

We have succeeded to set-up a protocol to easily amplify miRNAs in urine samples. Based on the data, microRNAs seem to be good biomarkers for early detection and screening of bladder cancer.