The results of this study suggested that the antioxidant defense capacity of the SW480 and SW1116 cancer cells was exceeded by the combined effects of ROS overproduction and TrxR1 inhibition caused by the nontoxic alkannin, while the NCM460 colon epithelial cells was able to tolerate the effects due to normal basal ROS output. This evidence concerns the gene TXNRD1 and cancer.