A Cross-Sectional Study Comparing Mir-503-5p Expression in Gastric Cancer Patients Before and After Chemotherapy

Background: Gastric cancer is the third most fatal cancer among all cancer types. Early diagnosis of thiscancer dramatically increases the five-year survival rate of patients. MicroRNAs (miRNAs) play a significantrole in tumorigenesis, angiogenesis, invasion, metastasis, and drug resistance in gastric cancer, similar to othercancers. The expression levels of miRNAs can influence tumor progression or suppression. This study aimedto investigate the expression levels of miR-503-5p in the serum of gastric cancer patients both before and afterchemotherapy.Methods: This observational study was conducted from 2022 to 2024 at Namazi and Shahid Faghihi Hospitals.Thirty patients with gastric cancer with a definitive diagnosis by gastroenterologists and pathologists and hadnot received any prior treatment, were included in the study. A blood sample of 5 ml was drawn from each patientand sent to the laboratory for analysis. After the completion of thechemotherapy, blood samples were collectedagain. The expression level of miR-503-5p was measured using real-time PCR. Data analysis was performedusing SPSS version 24, and differences in miR-503-5p expression and clinicopathological characteristics wereassessed using ANCOVA and paired ttests.Results: Comparing serum levels of miR-503-5p in gastric cancer patients before and after chemotherapyrevealed a 2.12-fold increase in miR-503-5p expression post-treatment (P=0.001). Furthermore, expressionlevels of miR-503-5p in the serum of patients with metastasis were significantly lower than patients withoutmetastasis (P<0.05).Conclusion: Considering the increased expression of miR-503-5p following treatment in gastric cancer patients,these findings suggest a suppressive role for miR-503-5p in gastric cancer. miR-503-5p may potentially serve asa biomarker for evaluating gastric cancer treatment.