Vitamin D3 is beneficial in ameliorating or preventing inflammation and carcinogenesis. Here, we evaluated if vitamin D3 has a preventive effect on colitis-associated carcinogenesis. Administration of azoxymethane (AOM), followed with dextran sulfate sodium (DSS), was used to simulate colitis-associated colon cancer in mice. The supplement of vitamin D3 at different dosages (15, 30, 60 IU·g·w), started before AOM or immediately after DSS treatment (post 60), was sustained to the end of the experiment. Dietary vitamin D3 significantly reduced the number of tumors and tumor burden in a dose-dependent manner. Of note, vitamin D3 in high doses showed significant preventive effects on carcinogenesis regardless of administration before or after AOM-DSS treatment. Cell proliferation decreased in vitamin D3 groups compared with the control group after inhibition of expression of β-catenin and its downstream target gene cyclin D1 in the colon. In vitro, vitamin D3 reduced the transcriptional activity and nuclear level of β-catenin, and it also increased E-cadherin expression and its binding affinity for β-catenin. Moreover, repression of E-cadherin was rescued by supplemental vitamin D3 in mouse colons. Taken together, our results indicate that vitamin D3 effectively suppressed colonic carcinogenesis in the AOM-DSS mouse model. Our findings further suggest that upregulation of E-cadherin contributes to the preventive effect of vitamin D3 on β-catenin activity.

It is well accepted that inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is one of high risk factors for colorectal cancer (CRC). This supports the notion that inflammation plays a key role in cancer development. Epidemiologic studies have shown that vitamin D (Vit D) deficiency is associated with IBD and various types of cancer including colorectal cancer. Clinical trials and mouse models have shown that Vit D is beneficial in preventing or ameliorating inflammation and carcinogenesis. Mechanism studies show that Vit D played wide-spectrum roles in anti-inflammation, immunoregulation, and anti-cancer activities. In this review, we summarized and updated the findings on Vit D, IBD and colitis-associated colorectal cancer (CAC) with the emphasis on the effects of Vit D on anti-inflammation, EMT and cancer stem cells (CSC).