The frequency of PD-L1-positive cells increased by AOM/DSS treatment in the tumor area tended to decrease by E2 treatment in the Nrf2 KO male mice than in the WT males, but did not show significance due to the low ‘N’ number of AOM/DSS + E2 group in Nrf2 KO (Figure 5E). This evidence concerns the gene CD274 and infectious otitis media.