UV exposure inhibits intestinal tumor growth and progression to malignancy in intestine-specific Apc mutant mice kept on low vitamin D diet

Menée sur des modèles murins de cancer intestinal, cette étude met en évidence une inhibition de la croissance et de la progression de la tumeur chez les souris recevant un régime alimentaire pauvre en vitamine D et une dose modérée de rayons ultraviolets

Résumé en anglais

Mortality from colorectal cancer increases with latitude and decreases with ambient UV radiation. We investigated whether moderate UV dosages could inhibit intestinal tumor development and whether this corresponded with UV-induced vitamin D. FabplCre;Apc15lox/+ mice, which develop intestinal tumors, and their parents were put on a vitamin D-deficient diet. Next to a control group, one group was vitamin D supplemented and another one group was daily UV irradiated from 6 weeks of age. Vitamin D statuses after 6 weeks of treatment were markedly increased: mean ± SD from 7.7 ± 1.9 in controls to 75 ± 15 nmol/l with vitamin D supplementation (no gender difference), and to 31 ± 13 nmol/l in males and 85 ± 17 nmol/l in females upon UV irradiation. The tumor load (area covered by tumors) at 7.5 months of age was significantly reduced in both the vitamin D-supplemented group (130 ± 25 mm2, p = 0.018) and the UV-exposed group (88 ± 9 mm2, p < 0.0005; no gender differences) compared to the control group (202 ± 23 mm2). No reductions in tumor numbers were found. Only UV exposure appeared to reduce progression to malignancy (p = 0.014). Our experiments clearly demonstrate for the first time an inhibitory effect of moderate UV exposure on outgrowth and malignant progression of primary intestinal tumors, which at least in part can be attributed to vitamin D.