Investigating the biomarker role of piRNAs in the diagnosis of colorectal cancer

‌Background & objectives: Colorectal cancer (CRC) is the most common gastric cancer and third lethal cancer worldwide. Despite development in diagnostic and treatment methods, due to the lack of typical symptoms in the early stages, most patients are diagnosed in the end stages. Therefore, finding simple, inexpensive, highly sensitive and specific diagnostic methods for early detection and prognosis of  colorectal cancer is important. piRNAs are one of the things that can be paid special attention to. In this review article, the function of these biomolecules in tumorigenesis are studied for diagnosis. Materials & Methods: The bibliographic search was performed on PubMed, Scopus, and Web of Science databases. Any language or date restrictions were not applied. Identified studies were screened by title, abstract, and full text. Results: piRNA expression is dysregulated in different tumor tissues such as and colorectal cancer compare with normal tissues. This regulatory RNAs role as oncogene or tumor suppressor in signaling pathways related to survival, proliferation, invasion, and metastasis of cancer cells. Some piRNAs expressions correlate with clinicopathologic features of cancer. Due to their small molecular size piRNAs can pass through cellular membrane and enter the bloodstream. Conclusions: Some piRNAs such as piR-5937, piR-28876, piR-020450 and piR-020619 elevate in serum of CRC patients as compared with healthy people and could be used as early diagnostic biomarkers with higher sensitivity and specificity compared to carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) for colorectal cancer.