Evaluation of Radiosensitive Effect of Tolmetin in Radiotherapy on Human Colonic Carcinoma Cell Line HT-29

Background: Radiotherapy is one of the cancer treatment methods. Although radioresistance and normal tissue toxicity limit the radiation therapy in certain anatomical locations, using some substances can be useful to increase radiosensitivity on cancer cells without cytotoxicity effect on normal cells. Objective: This study aimed to evaluate the radiosensitizing effect of tolmetin in radiotherapy treatment on human colon cancer cell line HT-29. Methods In this study, human colon cancer cells HT-29 in different groups were irradiated with 4 Gy x-ray, and tolmetin was administered in different concentrations (75, 100, and 150 μM). Then, the groups were compared with each other and with the control group by Micronucleus Assay (MN) and Nuclear Division Index (NDI). NDI investigated the cytotoxicity, and MN indicated the genotoxicity. Results: In the group receiving radiation, micronuclei increased significantly compared to the control group. In the group receiving tolmetin with a concentration of 75 and 100 μM, the number of micronuclei also increased compared to the control group. In all groups treated with tolmetin that also received radiation, a significant increase in micronuclei was observed, which was more noticeable at concentrations of 100 and 150 μM. At the same time, tolmetin at the studied concentrations did not change the NDI index. Conclusion: The present study demonstrates that tolmetin has a radiosensitizing effect on HT-29 colon cancer cells, which depends on the tolmetin concentration. In addition, tolmetin has no cytotoxic effect on this cell line.