Folate and one other aspects of 1-carbon metabolism Specific aims: To examine the relationships of circulating levels of folate, homocysteine, vitamin B-6, vitamin B-12, and vitamin B-2, and of selected polymorphisms in 14 key one-carbon metabolism pathway genes, to risk of incident breast cancer in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial. In collaboration with Drs. Chanock and Yeager of the NCI Core Genotyping Facility, polymorphisms in the genes will be selected on the basis of spacing in putative functional regions (exons, 5' upstream regions and conserved non-coding regions), prevalence (> 5%), functionality (demonstrated relationship to enzyme function or chronic disease), and importance for haplotyping (haplotype tag SNP's). Primary hypotheses: 1. Circulating levels of folate, B-6, B-12, and B-2 are inversely associated with risk of breast cancer. 2. Circulating levels of homocysteine are positively associated with risk of breast cancer. 3. Some of the common genetic polymorphisms in key genes in the one-carbon metabolism pathway modulate risk of breast cancer.P Secondary hypotheses: 1. The positive associations between circulating levels of folate, B-6, B-12, and B-2 levels and breast cancer risk and the inverse association between circulating homocysteine and breast cancer risk are significantly modulated by some of genetic polymorphisms in key one-carbon metabolism genes. 2. Circulating levels of folate, B-6, B-12, B-2, and homocysteine are significantly influenced by some of the genetic polymorphisms in key one-carbon metabolism genes. Vitamin D metabolites Primary hypotheses: 1. Lower levels of prospectively measured serum vitamin D metabolites, 25-hydroxyvitamin D (25(OH)D and/or 1,25-dihydroxyvitamin D (1,25(OH)2D) are related to higher breast cancer risk. 2. Specific polymorphisms of one or more genes related to hormonal vitamin D function affect breast cancer risk. In particular, breast cancer risk is higher among subjects with specific genetic polymorphisms of (1) the vitamin D receptor (VDR), the only nuclear protein that binds the active vitamin D metabolite; (2) retinoid X receptor (RXR), which by forming a heterodimeric complex with VDR, initiates active vitamin D signaling; and (3) the enzyme 1-alpha-hydroxylase (CYP27B1), which catalyzes the production of active hormonal vitamin D and/or the enzyme 24-Hydroxylase (CYP24), which generates an inactive form of vitamin D. Secondary hypotheses: 1. Specific vitamin D-associated genetic polymorphisms modify the breast cancer risk associated with serum levels of 25(OH)D and/or 1,25(OH)2D. 2. Estrogens modify the breast cancer risks associated with serum levels of 25(OH)D and/or 1,25(OH)2D. Insulin resistance and chronic inflammation. Specific aims: To examine the relations of plasma levels of C-peptide, glycosylated hemoglobin, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-a ), high-sensitivity C-reactive protein (CRP), and genes encoding inflammatory-related factors to risk of breast cancer in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial. Primary hypotheses: 1. Plasma C-peptide and glycosylated hemoglobin are positively associated with the risk of breast cancer among postmenopausal women. 2. Plasma pro-inflammatory markers (IL-6, TNF-a , high-sensitivity CRP), and sequence variants in certain haplotypes of inflammation-related genes that are associated with an enhanced inflammatory state are positively associated with the risk of breast cancer among postmenopausal women. Secondary hypotheses: 1. The positive associations between indicators of insulin resistance and breast cancer risk are more pronounced among women with increased levels of inflammatory markers. 2. The positive associations between indicators of insulin resistance and breast cancer risk are not modified by endogenous sex hormones (i.e., total estradiol, free estradiol, and non-SHBG-bound estradiol). 3. The positive associations between indicators of the inflammatory state and breast cancer risk are more pronounced among women not using NSAIDs. Plasma antioxidants, MnSOD genotype, and the risk of breast cancer. Specific aims: To examine the relations of plasma antioxidants and MnSOD genotype to breast cancer risk in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial. Primary hypotheses: 1. Low plasma levels of antioxidants, specifically a-carotene, ?-carotene, ?-cryptoxanthin, lycopene, lutein/zeaxanthin, retinol, a-tocopherol, and ?-tocopherol, are related to an increased risk of breast cancer.2. The Val to Ala polymorphism in the manganese superoxide dismutase (MnSOD) gene is related to an increased risk of breast cancer. Secondary hypothesis: 1. The effect of the Ala/Ala MnSOD genotype on breast cancer risk varies by levels of plasma antioxidants.

Stephen Chanock (DCEG)
Elizabeth Khaykin (DCEG)
Roni Falk (DCEG)
Thomas Fears (DCEG)
Michal Freedman (DCEG)
Wen-Yi Huang (DCEG)
Michael Leitzmann (DCEG)
Richard Hayes (New York University)
Ronald Horst (Heartland Assays, Inc.)
Catherine Schairer (DCEG)
Rebecca Troisi (DCEG)
Sholom Wacholder (DCEG)