miRNA Signature and its Clinicopathological Association in Colorectal Cancer: A Cross-sectional Study

Introduction: Colorectal Cancer (CRC) is a significant health problem worldwide, with more than 70,000 new cancer cases recorded in India in 2020. A better understanding of CRC prognosis is needed. The substantial intratumoural heterogeneity among tumours of different stages has entailed the research for new biomarkers to more clearly identify tumour biology and behaviour. Micro Ribonucleic Acids (miRNAs) are non coding RNAs comprised of approximately 20-25 nucleotides and play an important role in epigenetic regulations. Studies have demonstrated that miRNAs play a critical role in tumourigenesis, metastasis, and tumour response to treatment. Comprehensive knowledge of miRNAs as potential markers of colon cancer diagnosis, prognosis, and predictive factors is crucial. Aim: To assess the miRNA signature (miR21, miR31, and miR34a) in colon cancer tumour samples and to evaluate the association of the miRNA signature with the clinicopathological profile and Pathological Tumour/Node/Metastasis (pTNM) stage of CRC patients. Materials and Methods: This cross-sectional and prospective study was conducted at the Departments of Pathology, Molecular Research and Diagnostics and Surgical Oncology of Sri Shankara Cancer Hospital, Bengaluru, Karnataka, India and was comprised of a total of 69 CRC patients who underwent surgery with a curative intent. The study was conducted over an 18 -month period from January 2020 to June 2021. miRNA was extracted from Formalin-fixed Paraffin -embedded (FFPE) samples, and quantitative Polymerase Chain Reaction (qPCR) was done to get corresponding A CT (Threshold Cycles) values. The expression of miR21, miR31, and miR34a was evaluated, and their association with different clinicopathological parameters like age, sex, tumour stage, grade, Carcinoembryonic Antigen (CEA) levels, Perineural Invasion (PNI), and Lymphovascular Invasion (LVI) status was studied. The expression of the mentioned miRNAs was assigned low and high values on the basis of median values. Spearman's correlation was done to check for any significant associations. Results: All three miRNAs (miR21, miR31, miR34a) were found to have lower values in the >60 years age group compared to the <60 years age group. Higher values of miRNA were found male patients than in females, with a p -value of 0.022 for miR21. However, miRNA expression (miR21, miR31, miR34a) did not show any statistically significant correlation with tumour location (p -values 0.543, 0.255, 0.255), lymph node status (p -values 0.676, 0.153, 0.930), TNM stage (p -values 0.273, 0.509, 0.898), LVI (p -values 0.233, 0.233, 0.733), PNI (p -values 0.686, 0.263, 0.756), and serum CEA level (p -values 0.543, 0.255, 0.255). Conclusion: The present study showed the possible tumoursuppressive role of miR34a in CRC. Although miR21 acts as an oncogenic miRNA in many cancers, in CRC, its expression differs between males and females, with most tumours in males exhibiting high expression.