Klin Onkol 2016; 29(6): 428-438. DOI: 10.14735/amko2016428.
Background: In the past few years, a number of studies have suggested that small non-coding RNAs could be promising diagnostic, prognostic and predictive biomarkers in oncology. Recently, small RNAs interacting with PIWI proteins (piRNAs) have been described. These small RNAs regulate gene expression at transcriptional and post-transcriptional levels; however, they appear to be specifically involved in silencing the transposable elements LINE and SINE and are thus considered to contribute to genomic stability. Furthermore, piRNAs participate also in other important biological processes, such as gametogenesis, chromosome segregation, and stem cell self-renewal. Although their expression was first noted in germ line cells, they are now known to be present in all tissue types and their expression is highly tissue-specific. In addition, piRNA expression is dysregulated in tumor tissues. Nevertheless, the exact function of these molecules in cancerogenesis is not known. Recently, free circulating piRNAs were reported to be stably present in body fluids, suggesting that they could serve as promising noninvasive biomarkers to enable early diagnosis, therapy response prediction, and accurate prognosis prediction of cancer patients. Aim: The aim of this review is to summarize current knowledge about piRNA biogenesis and their functions in the regulation of gene expression and transposons silencing. In addition, the review focuses on piRNAs that show dysregulated expression in different types of cancers and that could serve as potential diagnostic biomarkers and/or therapeutic targets.
