MicroRNA is a small, non-coding single-stranded RNA with a length of 21 to 23 nucleotides that are involved in the regulation of post-transcriptional expression of about 60% of human genes. They also regulate processes such as the proliferation, apoptosis, evolution, and differentiation of cancers and increase and decrease gene expression. This means that they can be used as biomarkers in the prognosis and diagnosis of diseases, including cancer, in the blood, urine, and tissue. They are found in plants, animals, and viruses, but they do not exist in bacteria. MicroRNAs can directly regulate oncogenes and tumor suppressor genes, so they can play an oncogenic or tumor suppressor role depending on the function of their target mRNAs. It is hoped that, with further research, a combined panel of miRNAs can be used as a non-invasive method for detecting cancer with higher sensitivity and specificity than the other tests.

In our study a total of 70 urine samples from prostate cancer patients (32 metastatic and 38 non-metastatic) and 30 from healthy subjects with negative biopsy reports were collected. The expression level of miR-21 and miR-214 in the urine were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). miR-21 showed a significant increase in expression (P = 0.003) and miR-214 showed a significant decrease in expression (P = 0.000) compared with the control group. The specificity, sensitivity, and area under the curve (AUC) were 100, 72.14, and 0.721% for combined panels of miR-21 and miR-214 and 63.33, 61.43, and 0.620%, respectively, for PSA. miR-21 and miR-214 showed significant change in expression in patients with prostate cancer compared with healthy subjects.