Epigenetic roles of PIWI proteins and piRNAs in colorectal cancer
Epigenetic roles of PIWI proteins and piRNAs in colorectal cancer
Fatemeh Sadoughi,1,*Seyyed Mehdi Mirhashemi,2Zatollah Asemi,3
1. Research Center for Biochemistry and Nutrition in Metabolic Diseases, Kashan University of Medical Sciences, Kashan, I.R. Iran 2. Metabolic Diseases Research Center, Research Institute for Prevention of Non-Communicable Diseases, Qazvin University of Medical Sciences, Qazvin, Iran 3. Research Center for Biochemistry and Nutrition in Metabolic Diseases, Kashan University of Medical Sciences, Kashan, I.R. Iran
Introduction: For years, it was believed that 98% of DNA was “junk” because of the non-coding parts; today, lines of researches have proven that these parts of DNA have some essential functions, as well. According to evidence, more than 70% of our genome is actively transcribed but protein-coding genes contain about 1–2% of the genome, and the major group of transcripts is noncoding RNAs (ncRNAs). NcRNAs are categorized by their function regulatory ncRNAs are one of the subclasses of them. Regulatory ncRNAs are also divided into two subtypes: small non-coding and long non-coding RNAs. P-Element induced wimpy testis (PIWI)—interacting RNA (piRNA) is one of the members of small non-coding group of RNAs and takes part in silencing transposons, epigenetic regulation, and reorganization of the genome. Some of these properties can provide an idea that piRNAs are associated with some cancer hallmarks containing cellular proliferation, apoptosis, metastasis, and invasion. Colorectal cancer (CRC) is a major cause of morbidity and mortality in both men and women around the world. This cancer is listed as the third common cancer after lung and breast cancer; Thus, finding novel methods for treating this cancer can be a help to many people around the globe.
Methods: We have tried to collect the evidence available on the application of PIWI proteins and their related RNAs in colorectal cancer. We have used diverse search engines for this purpose including Pubmed, Google Scholar, and Scopus.
Results: Dysregulation of some piRNAs can be observed in CRC cells; for instance, up-regulated PiR-54265 is related to the activation of STAT3 signaling pathway, up-regulated PiR-823 is associated with the expression of HSP family, and down-regulated PiR-1245 is associated with metastatic stages of colorectal cancer. Furthermore, the levels of PIWI proteins are also observed to be altered in CRC cells. The up-regulation of HIWI, PIWIL2, and PIWIL1 is confirmed by some research in CRC.
Conclusion: Accumulative evidence expresses that PIWI proteins and their related RNAs (piRNAs) can be used only for diagnostic or prognostic purposes in CRC and till now, no therapeutic effects are discovered for these RNAs. However, further investigations might enhance our knowledge on whether they can be used for therapeutic purposes or not.