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Cancer Control Research

Abstract

DESCRIPTION (provided by applicant): The proposed project makes uses of existing serum samples collected during a 2-year randomized soy trial. Epidemiologic evidence supports a role for soy foods and isoflavones in breast cancer prevention, but the possible mechanisms of action are not well understood. Based on results from animal studies and human interventions, we hypothesize that soy reduces chronic inflammation, a possible risk factor for breast cancer. The original study and other reports indicate that the preventive effects of soy on breast cancer, if they exist, are not mediated by circulating sex hormones. The growing interest in an inflammatory etiology for cancer, as well as findings that link nutritional factors to immune responses, support our hypothesis. The aim of this study is to examine the effects of two daily servings of soy on serum levels of inflammatory markers. In addition, we will explore differences in serum levels of inflammatory markers by ethnicity, body mass index, and lifetime soy intake. During the 2-year nutritional intervention, 220 premenopausal women were randomized and donated multiple blood samples during the luteal phase as determined by an ovulation kit. The intervention group consumed two daily servings of soy foods, predominantly tofu, soy milk, and soy nuts, while the control women maintained their regular diet. According to several measures, compliance with the study regimen was excellent. The number of dropouts did not differ by group: 17 (15.6%) intervention women and 14 (12.6%) controls left the study prematurely. The subjects gave written permission to use their specimens for future analyses. Frozen serum samples stored at -80¿C will be analyzed for six inflammatory markers, adiponectin, leptin, interleukin (IL)-6, C-reactive protein (CRP), tumor necrosis factor (TNF)-a, and IL-1b, using established ELISA assays. For each of the 205 subjects (100 intervention subjects and 105 controls) with serum samples, we will analyze four samples, one each collected at baseline, after 6, 12, and 24 months. The statistical analysis will apply general linear models to compare the levels of inflammatory markers by soy intake, while taking into account the repeated measurement design.