Inflammation Modulation by Vitamin D and Calcium in the Morphologically Normal Colorectal Mucosa of Patients with Colorectal Adenoma in a Clinical Trial
David C. Gibbs, Veronika Fedirko, John A. Baron, Elizabeth L. Barry, W. Dana Flanders, Marjorie L. McCullough, Rami Yacoub, Tapasya Raavi, Robin E. Rutherford, March E. Seabrook, Roberd M. Bostick
Abstract
Abstract Increased COX-2 and decreased 15-hydroxyprostaglandin dehydrogenase (15-HPGD) expression promote prostaglandin-mediated inflammation and colorectal carcinogenesis. Experimental studies suggest that vitamin D and calcium may inhibit these pathways, but their effects on colorectal tissue COX-2 and 15-HPGD expression in humans are unknown. We tested the effects of supplemental vitamin D (1,000 IU/day) and/or calcium (1,200 mg/day) on COX-2 and 15-HPGD expression in the morphologically normal rectal mucosa from 62 paients with colorectal adenoma in a placebo-controlled chemoprevention trial. We measured biomarker expression using automated IHC and quantitative image analysis at baseline and 1-year follow-up, and assessed treatment effects using mixed linear models. The primary outcome was the COX-2/15-HPGD expression ratio, because these enzymes function as physiologic antagonists. After 1 year of treatment, the mean COX-2/15-HPGD expression ratio in full-length crypts proportionately decreased 47% in the vitamin D group (P = 0.001), 46% in the calcium group (P = 0.002), and 34% in the calcium + vitamin D group (P = 0.03), relative to the placebo group. Among individuals with the functional vitamin D–binding protein isoform DBP2 (GC rs4588*A), the COX-2/15-HPDG ratio decreased 70% (P = 0.0006), 75% (P = 0.0002), and 60% (P = 0.006) in the vitamin D, calcium, and combined supplementation groups, respectively, relative to placebo. These results show that vitamin D and calcium favorably modulate the balance of expression of COX-2 and 15-HPGD—biomarkers of inflammation that are strongly linked to colorectal carcinogenesis—in the normal-appearing colorectal mucosa of patients with colorectal adenoma (perhaps especially those with the DBP2 isoform). Prevention Relevance: Supplemental calcium and vitamin D reduce indicators of cancer-promoting inflammation in normal colorectal tissue in humans, thus furthering our understanding of how they may help prevent colorectal cancer.