Considering the possible contribution of oxidative stress to colorectal cancer in humans, as mentioned above, clarification of the effects of inactivation of NRF2 on lesions is important for assessment of the risk of colorectal cancer in individuals with SNPs in NRF2. To this end, long‐term exposure of Nrf2−/− mice to KBrO3 was performed after Mutyh−/− or Msh2−/− mouse model. The gene discussed is MSH2; the disease is colorectal cancer.