en پزشکی مولکولی Molecular Medicine تحقيقي Original Paper <strong>Background and objectives:</strong> Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality in the world. MicroRNAs (miRNAs) have potential as diagnostic biomarkers for various diseases including cancer. This study was undertaken to investigate expression of miR-21 before and after surgery in patients with hereditary CRC.<br> <strong>Methods: </strong>After collecting blood samples from 39 patients and 39 healthy controls, total RNA was extracted by the TRIzol method. Following cDNA synthesis, expression of <em>miR-21 </em>in serum of subjects was evaluated using real-time PCR, along with two reference genes, <em>let-7d</em> and <em>let-7g</em>. The real-time expression results and Ct values were collected and analyzed based on the 2-∆∆ct method.<br> <strong>Results:</strong> In spite of tumor removal, serum miR-21 expression levels was significantly higher in hereditary CRC patients compared with controls (P=0.022).<br> <strong>Conclusion:</strong> Our results confirmed that samples from hereditary cases of CRC must not be included in experiments on the diagnostic potential of miRNAs. Colorectal Neoplasms,Gene Expression,Real-Time Polymerase Chain Reaction, 1 4 http://mlj.goums.ac.ir/browse.php?a_code=A-10-854-1&slc_lang=en&sid=1 Mohammad Arefi arefim1368@yahoo.com 100319475328460019021 100319475328460019021 No Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Golestan University of Medical Sciences, Gorgan, Iran Abbas Abdollahi aabdollahi@gmail.com 100319475328460019022 100319475328460019022 No Department of General Surgery, School of Medicine, Surgical Oncology Research Center, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran Ayyoob Khosravi khosraviaa@yahoo.com 100319475328460019023 100319475328460019023 No Department of Molecular Medicine, School of Advanced Technologies in Medicine, Golestan University of Medical Sciences, Gorgan, Iran Abdolavahab Moradi abdolvahabm@yahoo.com 100319475328460019024 100319475328460019024 No Department of Microbiology, School of Medicine, Research Center of Gastroenterology and Hepatology, Golestan University of Medical Sciences, Gorgan, Iran Seyed Hamid Aghaee-Bakhtiari haghaeei3@gmail.com 100319475328460019025 100319475328460019025 No Department of Medical Biotechnology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Naimeh Javid njavid62@yahoo.com 100319475328460019026 100319475328460019026 No Department of Microbiology, School of Medicine, Research Center of Gastroenterology and Hepatology, Golestan University of Medical Sciences, Gorgan, Iran Mehdi Evazalipour mavaz1362@gmail.com 100319475328460019027 100319475328460019027 No Department of Pharmaceutical Biotechnology, School of Pharmacy, Guilan University of Medical Sciences, Rasht, Iran Anvarsadat Kianmehr kiabiotpro@yahoo.com 100319475328460019028 100319475328460019028 Yes Medical Cellular and Molecular Research Center, Golestan University of Medical Sciences, Gorgan, Iran