Dietary Calcium and Magnesium, Genetics, and Colorectal Adenoma

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DESCRIPTION (provided by applicant): Project Summary: Results have been inconsistent on the protective effect of calcium and magensium intake on colorectal cancer and adenoma. We found very recently in the Tennessee Colorectal Polyp Study (TCPS; P50CA95103) that the associations between intake of calcium or magnesium and risk of colorectal adenoma and hyperplastic polyps may differ by the common Thr1482Ile polymorphism of the TRPM7 gene, a gene involved in calcium and magnesium re(absorption) and homeostasis. Our finding may partially explain the inconsistency in previous studies on calcium and magnesium. In addition, we found that the ratio of calcium to magnesium intake significantly interacted with the Thr1482Ile polymorphism in relation to both adenomatous and hyperplastic polyps. In response to PAR-07-377, we propose a clinical epidemiologic study, based on our promising data, to test several novel hypotheses regarding gene-nutrition interactions using data and biological samples collected as part of the TCPS, a large on-going molecular epidemiologic case-control study of colorectal adenoma. Specifically, we will 1) confirm our pilot finding in an independent set; and 2) conduct a two-phase study to evaluate the relationships between other polymorphisms in 14 candidate genes involved in magnesium and calcium (re)absorption, regulation and balance and risk of colorectal adenoma; and investigate whether the associations between intake of calcium and magnesium or the ratio of calcium to magnesium intake and risk of colorectal adenoma differs by the genotypes or haplotypes in the 14 genes. The first phase of the study will include 1200 cases and 2400 controls to comprehensively investigate promising polymorphisms and their interactions with nutrients. All promising variants will be re-evaluated in an independent set of 800 cases and 1600 controls to validate the identified associations or nutrient-gene interactions. The proposed two-phase study design will allow us to effectively address potential false positive findings (Type I error), one of the most serious concerns regarding association studies of low-penetrance genetic factors and will allow us to enhance the statistical power for evaluation of gene-gene and gene-nutrition interactions. The results from our study will help to identify people at a high risk of colorectal adenoma and to develop personalized strategies of dietary changes or nutritional fortication to prevent occurrence of colorectal adenoma, and, thus, colorectal cancer. In the general US population, 1 in 18 individuals will develop colorectal cancer over their lifetime and forty percent will die within five years of diagnosis, mainly due to diagnosis at a late stage. Therefore, development of primary preventive strategies for colorectal cancer is very critical. The results from our study will help to identify people at a high risk of colorectal adenoma and to develop personalized strategies to prevent occurrence of colorectal adenoma, and, thus, colorectal cancer through dietary changes or nutritional fortification.