One of the methods of cancer treatment is radiotherapy. Although radiation resistance and toxicity in normal cells limit the use of radiotherapy in some specific anatomical situations, however, together with radiotherapy, the use of substances that increase the radiation sensitivity of cancer cells and at the same time toxicity can be useful if they do not have cells on normal cells. The present study aimed to investigate the radiosensitizing effect of tolmetin in radiotherapy treatment on human clonal cancer cells. In this study, human clone HT-29 cancer cells in different groups were exposed to X-rays and tolmetin drug and were compared with each other and with the control group by micronucleus evaluation method and nuclear division index. The effect of cytotoxicity was evaluated with the index of nuclear division and genotoxicity of cells with the method of evaluating the number of micronuclei. Based on the results, the number of micronuclei increased significantly in the radiation-receiving group compared to the control group. In the group receiving tolmetin with 75 and 100 μM concentrations, the number of micronuclei also increased compared to the control group. A significant increase in the number of micronuclei was observed in all groups treated with tolmetin that received radiation, and this increase was more noticeable in concentrations of 100 and 150 μM. Meanwhile, tolmetin did not change the nuclear division index in the studied concentrations. The present study showed that tolmetin has a radiosensitizing effect on HT-29 human colon cancer cells, which is dependent on tolmetin concentration. In addition, tolmetin does not have a cytotoxicity effect on the mentioned cell line.
