Newly-identified Pathways Relating Vitamin D to Carcinogenesis: A Review.

Bilani, Nadeem; Elson, Leah; Szuchan, Charles; Elimimian, Elizabeth; Saleh, Mustafa; Nahleh, Zeina

BACKGROUND The epidemiological relationship between vitamin D levels and cancer has been thoroughly investigated. Published data from large studies appear to corroborate a significant relationship between higher serum vitamin D concentrations and improved survival. Mechanistic reviews on commonly-studied cancers - including breast cancer, colon cancer and melanoma - focus predominantly on data from older studies. In outlining avenues for future research, we believe there is utility in summarizing novel findings introduced to the literature. MATERIALS AND METHODS In this narrative review, we used MEDLINE, PUBMED and Cochrane databases to identify mechanistic studies published from January 1, 2015 onwards exploring this topic. RESULTS Twenty-five mechanistic studies were included in this review. It was found that vitamin D plays a critical role in both direct (i.e. tumor gene expression, proliferation, invasiveness, sensitivity to chemotherapy etc.) and indirect (i.e. effects on the tumor microenvironment and immunomodulation) tumor suppression mechanisms. CONCLUSION These newly-identified pathways warrant further research, with the hopes that we may understand how and when vitamin D supplementation can be integrated into precision medicine therapeutics for cancers of the breast, colon and skin. Cancer care providers should consider recommendations to screen for vitamin D deficiency in this population.