Vitamin D deficiency in the ApcPirc/+ rat does not exacerbate colonic tumorigenesis, while low dietary calcium might be protective

Vitamin D and cancer

The role of vitamin D in the prevention of chronic diseases including cancer, has received a great deal of attention during the past few decades. The term "Cancer" represents multiple disease states with varying biological complexities. The strongest link between vitamin D and cancer is provided by ecological and studies like observational, in preclinical models. It is apparent that vitamin D exerts diverse biological responses in a tissue specific manner. Moreover, several human factors could affect bioactivity of vitamin D. The mechanism(s) underlying vitamin D initiated anti-carcinogenic effects are diverse and includes changes at the muti-system levels. The oncogenic environment could easily corrupt the traditional role of vitamin D or could ensure resistance to vitamin D mediated responses. Several researchers have identified gaps in our knowledge pertaining to the role of vitamin D in cancer. Further areas are identified to solidify the role of vitamin D in cancer control strategies.

First person – Amy Irving

First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Amy Irving is first author on ‘ Vitamin D receptor absence does not enhance intestinal tumorigenesis in Apc^Pirc/+ rats’, published in BiO. Amy is a research scientist in the lab of Hector DeLuca at the University of Wisconsin-Madison, USA, investigating the individual contributions of sunlight, vitamin D, calcium, and other pathway players on diseases with a location association paradigm, specifically colon cancer and multiple sclerosis.

Vitamin D receptor absence does not enhance intestinal tumorigenesis in ApcPirc/+ rats

Epidemiological observations have prompted some to posit that elevated circulating vitamin D is responsible for reduced colon cancer in individuals residing near the equator. We have previously demonstrated that vitamin D has no effect on colon cancer in two rodent models of intestinal tumorigenesis. We have now extended this line of inquiry to ask whether ablation of vitamin D receptor (VDR) affects tumorigenesis. A VDR null rat was developed using Cas9-CRISPR technology, which allowed us to investigate whether 1,25(OH)D₃ signaling through its receptor plays a role in intestinal tumorigenesis. Loss of VDR expression alone did not induce tumorigenesis, even in animals exposed to the inflammatory agent dextran sodium sulfate. These VDR^−/− rats were then crossed with Apc^Pirc/+ rats, which are predisposed to the development of intestinal neoplasms. In combination with the Pirc/+ mutation, VDR loss did not enhance tumor multiplicity, growth, or progression in the colon or small intestine. This study demonstrates that the vitamin D receptor does not impact tumor development, and strongly supports previous findings that vitamin D itself does not play a role in colon cancer development or progression. Alternative explanations are needed for the original latitude hypothesis, as well as observational data in humans.

This article has an associated First Person interview with the first author of the paper.

Summary: Loss of vitamin D receptor, alone or in combination with either an inflammatory agent or the Apc^Pirc/+ rat intestinal tumor model, did not enhance tumor occurrence, growth, or progression.

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

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.

Optimization of Erlotinib Plus Sulindac Dosing Regimens for Intestinal Cancer Prevention in an Apc-Mutant Model of Familial Adenomatous Polyposis (FAP)

A clinical trial in patients with familial adenomatous polyposis (FAP) demonstrated that sulindac plus erlotinib (SUL+ERL) had good efficacy in the duodenum and colon, but toxicity issues raised concerns for long-term prevention. We performed a biomarker study in the polyposis in rat colon (Pirc) model, observing phosphorylated Erk inhibition in colon polyps for up to 10 days after discontinuing ERL+SUL administration. In a follow-up study lasting 16 weeks, significant reduction of colon and small intestine (SI) tumor burden was detected, especially in rats given 250 ppm SUL in the diet plus once-a-week intragastric dosing of ERL at 21 or 42 mg/kg body weight (BW). A long-term study further demonstrated antitumor efficacy in the colon and SI at 52 weeks, when 250 ppm SUL was combined with once-a-week intragastric administration of ERL at 10, 21, or 42 mg/kg BW. Tumor-associated matrix metalloproteinase-7 (Mmp7), tumor necrosis factor (Tnf), and early growth response 1 (Egr1) were decreased at 16 weeks by ERL+SUL, and this was sustained in the long-term study for Mmp7 and Tnf. Based on the collective results, the optimal dose combination of ERL 10 mg/kg BW plus 250 ppm SUL lacked toxicity, inhibited molecular biomarkers, and exhibited effective antitumor activity. We conclude that switching from continuous to once-per-week ERL, given at one-quarter of the current therapeutic dose, will exert good efficacy with standard-of-care SUL against adenomatous polyps in the colon and SI, with clinical relevance for patients with FAP before or after colectomy. PREVENTION RELEVANCE: This investigation concludes that switching from continuous to once-per-week erlotinib, given at one-quarter of the current therapeutic dose, will exert good efficacy with standard-of-care sulindac against adenomatous polyps in the colon and small intestine, with clinical relevance for patients with FAP before or after colectomy.

Effect of Chronic Vitamin D Deficiency on the Development and Severity of DSS-Induced Colon Cancer in Smad3-/- Mice

Both human epidemiologic data and animal studies suggest that low serum vitamin D increases the risk of inflammatory bowel disease (IBD) and consequently IBD-associated colorectal cancer. We tested the hypothesis that vitamin D deficiency increases the risk for colitis-associated colon cancer (CAC) by using an established CAC mouse model, 129-Smad3tm1Par/J (Smad3-/-) mice, which have defective transforming growth factor β-signaling and develop colitis and CAC after the administration of dextran sodium sulfate (DSS). After determining a dietary regimen that induced chronic vitamin D deficiency in Smad3-/- mice, we assessed the effects of vitamin D deficiency on CAC. Decreasing dietary vitamin D from 1 IU/g diet (control diet) to 0.2 IU /g diet did not decrease serum 25-hydroxyvitamin D (25(OH)D) levels in Smad3-/- mice. A diet devoid of vitamin D (< 0.02 IU/g diet [no added vitamin D]; vitamin D-null) significantly decreased serum 25(OH)D levels in mice after 2 wk (null compared with control diet: 8.4 mg/mL compared with 12.2 ng/mL) and further decreased serum levels to below the detection limit after 9 wk but did not affect weight gain, serum calcium levels, bone histology, or bone mineral density. In light of these results, Smad3-/- mice were fed a vitamin D-null diet and given DSS to induce colitis. Unexpectedly, DSS-treated Smad3-/- mice fed a vitamin D-null diet had improved survival, decreased colon tumor incidence (8% compared with 36%), and reduced the incidence and severity of colonic dysplasia compared with mice fed the control diet. These effects correlated with increased epithelial cell proliferation and repair early in the disease, perhaps reducing the likelihood of developing chronic colitis and progression to cancer. Our results indicate that vitamin D deficiency is beneficial in some cases of CAC, possibly by promoting intestinal healing.

Vitamin D is not required for adaptive immunity to listeria

Although ex vivo research suggests that vitamin D may play a role in innate and adaptive immunity, clear in vivo evidence is lacking. We have tested whether severe vitamin D deficiency alters the ability of mice to resist infection by Listeria. Our results show that vitamin D deficiency does not affect the LD50 of naïve mice in response to Listeria. To study the adaptive immune response, the LD50 for Listeria-immunized mice was determined for vitamin D-deficient and vitamin D-sufficient mice. Although the LD50 clearly increased by immunization with inactivated Listeria, there was no effect of vitamin D deficiency on survival of mice infected with wild-type Listeria. Thus, in this model of adaptive immunity, we could find no evidence of a role for vitamin D.