Calcium and colorectal cancer: some questions remain

Single Nucleotide Polymorphisms in 25-Hydroxyvitamin D3 1-Alpha-Hydroxylase (CYP27B1) Gene: The Risk of Malignant Tumors and Other Chronic Diseases

: Vitamin D is widely known for its roles in the promotion of apoptosis and differentiation, with simultaneous inhibition of proliferation, inflammation, angiogenesis, invasion, and metastasis. Modern literature lacks complete information on polymorphisms in CYP27B1, the only enzyme capable of vitamin D activation. This review presents gathered data that relate to genetic variants in CYP27B1 gene in correlation to multiple diseases, mostly concerning colorectal, prostate, breast, lung, and pancreatic cancers, as well as on other pathologies, such as non-Hodgkin's lymphoma, oral lichen planus, or multiple sclerosis.

Inhibitory effects of calcium against intestinal cancer in human colon cancer cells and Apc(Min/+) mice

The aim of the study was to investigate the inhibitory effects of calcium against intestinal cancer in vitro and in vivo. We first investigated the effects of calcium treatment in HCT116 and HT29 human colon cancer cells. At the concentration range of 0.8-2.4 mM, calcium significantly inhibited cell growth (by 9-29%), attachment (by 12-26%), invasion (by 15-31%), and migration (by 19-61%). An immunofluorescence microscope analysis showed that the treatment with calcium (1.6 mM) for 24 h increased plasma membrane β-catenin but decreased nuclear β-catenin levels in HT29 cells. We then investigated the effect of dietary calcium on intestinal tumorigenesis in Apc^Min/+ mice. Mice received dietary treatment starting at 6 weeks of age for the consecutive 8 weeks. The basal control diet contained high-fat (20% mixed lipids by weight) and low-calcium (1.4 mg/g diet) to mimic the average Western diet, while the treatment diet contained an enriched level of calcium (5.2 mg calcium/g diet). The dietary calcium treatment decreased the total number of small intestinal tumors (by 31.4%; P < 0.05). The largest decrease was in tumors which were ≥ 2 mm in diameter, showing a 75.6% inhibition in the small intestinal tumor multiplicity (P < 0.001). Immunohistochemical analysis showed significantly reduced nuclear staining of β-catenin (expressed as nuclear positivity), but increased plasma membrane staining of β-catenin, in the adenomas from the calcium-treated groups in comparison to those from the control group (P < 0.001). These results demonstrate intestinal cancer inhibitory effects of calcium both in human colon cancer cells and Apc^Min/+ mice. The decreased β-catenin nuclear localization caused by the calcium treatment may contribute to the inhibitory action.

Circulating 25-hydroxyvitamin-D and risk of colorectal adenomas and hyperplastic polyps

Colorectal adenomas are clear precursors of cancer; hyperplastic polyps may also have malignant potential. An inverse association between circulating vitamin D metabolites and adenoma risk has been reported, but less is known about vitamin D and hyperplastic polyps. We conducted a case-control study of adenomas and hyperplastic polyps among 459 members of an integrated health plan evaluated via colonoscopy. Questionnaires provided information on colorectal polyp risk factors, and plasma samples were assayed for 25-hydroxyvitamin-D [25(OH)D]. Polytomous regression was used to estimate odds ratios for adenomas (n = 149) and hyperplastic polyps (n = 85) compared to polyp-free controls (n = 225) by tertile of 25(OH)D. An inverse association between 25(OH)D and adenomas was suggested after adjustment for potential confounding factors [comparing upper to lower tertiles, OR (95%CI): 0.71 (0.38-1.30)]. After restriction of the analyses to study participants with no history of polyps, this OR estimate was reduced further [adjusted OR (95%CI): 0.52 (0.23-1.20)]. In comparison, no inverse association between hyperplastic polyps and 25(OH)D was observed among the full study participants [adjusted OR (95%CI): 1.17 (0.55-2.51)] or among those without prior polyps [adjusted OR (95%CI): 1.42 (0.55-3.65)]. Our study suggests that the established inverse association between circulating 25(OH)D and adenoma may not apply to hyperplastic polyps.

Genetic variation in calcium-sensing receptor and risk for colon cancer

BACKGROUND

Experimental and epidemiologic studies have suggested that high calcium intake is associated with decreased colon cancer risk, yet very limited data are available for candidate genes in the calcium-vitamin D pathway and colon cancer risk. To address this, we evaluated whether calcium-sensing receptor (CASR) single-nucleotide polymorphisms are associated with colon cancer risk. We also examined interactions among CASR, calcium, and vitamin D intake and previously genotyped vitamin D-related genes.

METHODS

We conducted a large multicenter population-based case-control study of 1,600 cases and 1,949 controls. Seventeen tagging single-nucleotide polymorphisms for CASR were selected from common single-nucleotide polymorphisms (minor allele frequency, >or=5%) based on resequencing data. Haplotypes were estimated and evaluated using HaploStats.

RESULTS

We did not observe an association between any CASR genotypes or haplotypes and colon cancer risk overall. However, when stratified by anatomic site, statistically significant associations were seen with risk for proximal colon cancer [rs10934578 TT: odds ratio, 1.35; 95% confidence interval (95% CI), 1.01-1.81; rs12485716 AG/AA: odds ratio, 0.84; 95% CI, 0.71-1.00; rs4678174 CT/CC: odds ratio, 0.83; 95% CI, 0.70-0.98; rs2270916 CC: odds ratio, 0.43; 95% CI, 0.19-0.97]. Concordantly, we observed a suggested association for a CASR haplotype (rs4678174, rs2270916) with risk for proximal colon cancer (global P=0.08). We did not observe any meaningful gene-environment (calcium and vitamin D) or gene-gene (CYP24A1, CYP27B1, and VDR) interactions with CASR genotypes and colon cancer risk.

CONCLUSION

Our study does not provide evidence for an overall association between CASR single-nucleotide polymorphisms and colon cancer; however, results suggest a possible role of CASR on proximal colon cancer, and subsite differences are consistent with known calcium biology. Nonetheless, these findings require confirmation.