Vitamin D regulates microbiome-dependent cancer immunity

The gut microbiome has been shown to modulate the response of cancer patients to therapy, but precisely how microbiota affect anticancer immunity is still being elucidated. Giampazolias et al. report that vitamin D bioavailability in mice influences the composition of the gut microbiome. After dietary manipulation, vitamin D levels were observed to affect gut bacteria, which in turn improved cancer immunotherapy and antitumor immunity. In humans, low vitamin D levels were correlated with tumor development, and gene signatures of vitamin D activity were associated with improved patient responses to immunotherapy. These findings highlight the connection between vitamin D and the immune system through gut bacteria and may have applications for improving cancer therapies.

A role for vitamin D in immune modulation and in cancer has been suggested. In this work, we report that mice with increased availability of vitamin D display greater immune-dependent resistance to transplantable cancers and augmented responses to checkpoint blockade immunotherapies. Similarly, in humans, vitamin D–induced genes correlate with improved responses to immune checkpoint inhibitor treatment as well as with immunity to cancer and increased overall survival. In mice, resistance is attributable to the activity of vitamin D on intestinal epithelial cells, which alters microbiome composition in favor of Bacteroides fragilis, which positively regulates cancer immunity. Our findings indicate a previously unappreciated connection between vitamin D, microbial commensal communities, and immune responses to cancer. Collectively, they highlight vitamin D levels as a potential determinant of cancer immunity and immunotherapy success.