Prevalence and Clinical Significance of miR-155-5p and miR-221-3p in Colorectal and Thyroid Cancer: A Study in Sulaymaniyah Province

Background: MicroRNAs (miRNAs) such as miR-155-5p and miR-221-3p are key regulators of gene expression in cancer. Although both have been implicated in colorectal cancer (CRC) and papillary thyroid carcinoma (PTC), data on their regional expression profiles and clinical associations remain scarce, particularly in the Middle East. This study assessed the expression patterns and clinical relevance of miR-155-5p and miR-221-3p in CRC and PTC patients from Sulaymaniyah Province, Iraq. Methods: Formalin-fixed, paraffin-embedded (FFPE) tumor and adjacent normal tissue samples were collected from 60 CRC patients and 50 PTC patients. miRNA expression levels were quantified using real-time quantitative PCR (RT-qPCR) and analyzed by the ΔΔCt method, adjusted for tumor cellularity. Statistical analyses were conducted to evaluate associations between miRNA expression and clinicopathological parameters. Results: miR-155-5p and miR-221-3p were frequently overexpressed in both CRC (65%) and PTC (72% and 68%, respectively). In CRC, miR-155-5p expression correlated significantly with histological grade, tumor location, and TNM stage (p < 0.05), while miR-221-3p did not show significant associations with clinicopathological features. In PTC, miR-155-5p exhibited a trend toward association with TNM stage (p = 0.02). No significant differences in expression levels of these miRNAs were observed between CRC and PTC samples. Conclusions: Overall, miR-155-5p and miR-221-3p are consistently overexpressed in CRC and PTC, indicating their potential as diagnostic biomarkers. miR-155-5p, in particular, shows promise as a marker of disease progression in CRC. These findings underscore the importance of region-specific studies in advancing our understanding of the molecular landscape of cancer.