CYP27A1 and infectious otitis media: Furthermore, Cyp27a1−/− mice treated with AOM–DSS displayed more and larger tumours compared with their littermate controls and GW3965 administration in Cyp27a1−/− mice rescued this phenotype (Fig. 4b and Extended Data Fig. 10f), suggesting that LXR activation downstream to CYP27A1 restrains intestinal tumorigenesis.