Vitamin D has a role in immune modulation and in shaping commensal microbial communities. Reis e Sousa and colleagues show that mice lacking Gc globulin (Gc^−/− mice), which regulates vitamin D availability, display enhanced tumour resistance. Intriguingly, co-housed wild-type mice, as well as mice that receive a faecal transfer from Gc^−/− mice, also exhibit enhanced tumour immunity. The authors found that vitamin D alters gene expression in intestinal epithelial cells in such a way that they promote the expansion of Bacteroides fragilis at the expense of Prevotella species (both are part of the normal gut microbiota). In wild-type mice, supplementation with vitamin D, or oral gavage with B. fragilis, enhanced tumour immunity. A connection between vitamin D and tumour immunity was also found in humans, as analysis of a Danish database of 1.5 million individuals showed that low vitamin D levels correlated with increased cancer incidence. In patients with cancer, a gene signature indicative of vitamin D receptor activation correlated with increased survival and improved responses to immunotherapy. Overall, these results reveal a new angle of the relationship between vitamin D, cancer and the microbiome, and highlight vitamin D as a potential determinant in antitumour immunity.

维生素 D 在免疫调节和塑造共生微生物群落中发挥作用。 Reis e Sousa 及其同事表明，缺乏调节维生素 D 可用性的 Gc 球蛋白（Gc ^−/−小鼠）的小鼠表现出增强的肿瘤抵抗力。有趣的是，共同饲养的野生型小鼠以及接受Gc ^−/−小鼠粪便移植的小鼠也表现出增强的肿瘤免疫力。作者发现，维生素 D 会改变肠上皮细胞中的基因表达，从而促进脆弱拟杆菌的扩张，但会损害普氏菌属物种（两者都是正常肠道微生物群的一部分）。在野生型小鼠中，补充维生素 D 或口服脆弱拟杆菌可增强肿瘤免疫力。在人类中也发现了维生素 D 与肿瘤免疫力之间的联系，对丹麦 150 万人数据库的分析表明，维生素 D 水平低与癌症发病率增加相关。在癌症患者中，表明维生素 D 受体激活的基因特征与生存率的提高和免疫治疗反应的改善相关。总体而言，这些结果揭示了维生素 D、癌症和微生物组之间关系的新角度，并强调维生素 D 作为抗肿瘤免疫的潜在决定因素。