Prostate cancer is the most common cancer in men and usually occurs in men over 50 years of age (1). Men have a 10% risk of developing this cancer, of which about 3% of cases are fatal (2). The primary symptoms are frequent urination, intermittent and poor urine flow, urinary incontinence, blood in the urine, semen excretion with pain, persistent pain in the lower back and impotence (3). Digital rectal examination (DRE) and biopsy are more common than laboratory tests for measuring prostate specific antigen (PSA) in the blood.
PSA is a glycoprotein produced both in cancerous and healthy epithelial cells that helps break down collagen in the semen and make it clot. In the case of prostate disease, over 4 ng/ml (recognized as normal) leaks into the bloodstream. PSA testing for diagnosis of prostate cancer has shown low sensitivity and specificity. For prostatitis and benign prostatic hyperplasia (BPH), the level of PSA may increase but, even with prostate cancer, it may be normal (1, 4).
A DRE shows changes in the shape and size of the prostate, but is not sensitive (5). If the results of PSA and DRE are not normal, prostate cancer is generally confirmed by biopsy. It is the gold standard for detection of prostate cancer, but is highly invasive, costly and painful (6, 7). One of the most effective factors in increasing patient longevity to improve treatment and reduce the financial and mental costs to the patient is the quick and early diagnosis of cancer. Researchers continue to search for such a method and have identified numerous biomarkers for the detection and tracking of cancer. One of the most important is microRNA.
MicroRNA is small, non-coding single-stranded RNA with a length of 21-23 nucleotides that is 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 (8). They are found in plants, animals, and viruses, but they do not exist in bacteria (9). MicroRNA can directly regulate oncogenes and tumor osteoporosis can play an oncogenic or tumor-assisted role, depending on the type of mRNA function they perform (10).
Early evidence of the association between microRNA and cancer was presented by Calin in 2002. He showed that, in many patients with chronic lymphocytic leukemia, a piece of the genome had been removed, including the miR-15a and miR-16 gene cluster (11). The profile of the expression of the microRNA involved in prostate cancer was published in 2007 (12).
One type of microRNA that plays a role in prostate cancer is miR-21. This microRNA can inhibit expression of tumors by PTEN gene suppressor and increases the aggressive proliferation of cancer cells (13). This microRNA is classified as an incomer. The most important target mRNAs are PDCD4, TPM1, TIMP3, MARCK and PTEN (14, 15). It plays an important role in bone metastasis in the advanced stages of prostate cancer (16) and is located on chromosome 17 (17). The miR-214 plays a role in prostate cancer, and the most important target mRNAs are EZH2 and CTNNB1 (14). It is located on chromosome 1 (17).
The aim of the present study was to determine changes in the expression of miR-21 and miR-214 in urine samples of patients with prostate cancer (metastatic and non-metastatic) compared to healthy control subjects, to carry out ROC curve analysis for each microRNA and compare them with the results of the PSA test, to investigate a non-invasive method for diagnosing prostate cancer.