1,25‐Dihydroxy vitamin D prevents tumorigenesis by inhibiting oxidative stress and inducing tumor cellular senescence in mice

Human epidemiological studies suggest that 1,25(OH) 2 D 3 deficiency might increase cancer incidence, but no spontaneous tumors have been reported in mice lacking 1,25(OH) 2 D 3 or deficient in its receptor. In our study, we detected, for the first time, diverse types of spontaneous tumors in l,25(OH) 2 D 3 deficient mice more than 1 year of age. This was associated with increased oxidative stress, cellular senescence and senescence‐associated secretory phenotype molecules, such as hepatocyte growth factor, mediated via its receptor c‐Met. Furthermore, 1,25(OH) 2 D 3 prevented spontaneous tumor development. We also demonstrated that l,25(OH) 2 D 3 deficiency accelerates allograft tumor initiation and growth by increasing oxidative stress and DNA damage, activating oncogenes, inactivating tumor suppressor genes, stimulating malignant cell proliferation and inhibiting their senescence; in contrast, supplementation with exogenous l,25(OH) 2 D 3 or antioxidant, or knock‐down of the Bmi1 or c‐Met oncogene, largely rescued the phenotypes of allograft tumors. Results from our study suggest that 1,25(OH) 2 D 3 deficiency enhances tumorigenesis by increasing malignant cell oxidative stress and DNA damage, stimulating microenvironmental cell senescence and a senescence‐associated secretory phenotype, and activating oncogenes and inactivating tumor suppressor genes, thus increasing malignant cell proliferation. Our study provides direct evidence supporting the role of vitamin D deficiency in increasing cancer incidence. Conversely, 1,25(OH) 2 D 3 prevented spontaneous tumor development, suggesting that this inhibitory effect prevents the initiation and progression of tumorigenesis, thus provides a mechanistic basis for 1,25(OH) 2 D 3 to prevent tumorigenesis in an aging organism.