Enhancing the Efficacy of Radiotherapy in Gastric Adenocarcinoma Cells by Gut Microbiota Metabolites: Implications for Urolithin Combination Therapy

Background Gastric adenocarcinoma (GA) ranks as the fourth leading cause of cancer-related mortality. The clinical effectiveness of radiotherapy in GA patients is often limited by the development of radiation resistance. Urolithins, which are metabolites produced by gut microbiota from ellagitannins, possess good bioavailability and exhibit beneficial pharmaceutical properties. The aim of present study was to determine whether urolithins can enhance the effects of ionizing radiation (IR) on GA cells for the first time. Methods Urolithins were synthesized and MKN-45 cells were pretreated with UroA, UroB, and mUroA for 24, 48 and 72 h, followed by 400, 600 and 800 cGy IR exposure. After recovery, the viability of the cells was evaluated by resazurin assay, and the mode of interaction between urolithins and IR was determined. Then, interactome mapping and gene set enrichment analyses were performed. Upon validating CHEK1 expression in GA tissues and MKN-45 cells, molecular docking was conducted to predict the interaction of urolithins with CHK1. Results Pretreatment with urolithins significantly decreased viability upon radiotherapy. The most considerable decrease in the cell viability was observed after 400 cGy IR exposure. In comparison to the control treatments, 24 h pretreatment with UroA and mUroA significantly ( p < .0001) reduced cell viability to 57.4% and 62.8%, respectively. In addition, 48 h pretreatment with UroA and mUroA significantly ( p < .001) reduced viability to 69.7% and 72.7% after exposure to 400 cGy IR, respectively. Upon 72 h pretreatment with urolithins, only mUroA induced synergistic effects with 400 cGy IR. In silico analyses highlighted CHK1 as one of the main proteins involved in the response to IR-induced DNA damage, showing overexpression in GA samples and MKN-45 cells. Additionally, molecular docking revealed favorable interactions between urolithins and CHK1. Conclusion Present study highlights the notable synergistic effects of urolithins in combination with IR, indicating their potential to improve therapeutic outcomes.