Excess adiposity and hormone replacement therapy (HRT) are important contributors to postmenopausal breast cancer risk. HRT has been shown to modify the association between body weight and breast cancer risk, although few studies are sufficiently large to examine the risk of breast cancer associated with body mass index (BMI) and weight gain separately among current HRT users and nonusers. This study includes 1,934 incident breast cancer cases occurring among 62,756 postmenopausal women in the Cancer Prevention Study-II Nutrition Cohort. Age-adjusted incidence rates were calculated, and Cox proportional hazards models were used to examine the association of BMI and adult weight gain (since age 18 years) with breast cancer risk stratified by HRT use. Total adult weight gain strongly predicted breast cancer risk among former and never HRT users (P for trend < 0.0001). Weight gain of 21-30 pounds was associated with a rate ratio of 1.4 (95% confidence interval 1.1-1.8); rates doubled among women gaining >70 pounds compared with women who maintained their weight within 5 pounds of their weight at age 18. After accounting for weight gain, neither recent BMI nor BMI at age 18 were independent predictors of risk. Among current HRT users, no association was seen between breast cancer and either BMI or weight gain. Adult weight gain is strongly associated with postmenopausal breast cancer only among non-HRT users in this study. These data illustrate the importance of examining breast cancer risk factors separately by HRT use; the effects of other risk factors may be attenuated or obscured among women taking HRT.
Background: Chemotherapy and radiation therapy result in increased free radical formation and depletion of tissue antioxidants. It is not known whether parenteral nutrition (PN) administered during bone marrow transplantation (BMT) supports systemic antioxidant status. Objective: The aims of the study were to determine 1) whether high-dose chemotherapy decreases concentrations of major circulating antioxidants in patients undergoing BMT and 2) whether administration of standard PN maintains systemic antioxidant concentrations compared with PN containing micronutrients and minimal lipids alone. Design: Twenty-four BMT patients were randomly assigned to receive either standard PN containing conventional amounts of dextrose, amino acids, micronutrients, and lipid (120 kJ/d) or a solution containing only micronutrients (identical to those in standard PN) and a small amount of lipid (12 kJ/d). Plasma antioxidant status was measured before conditioning therapy and serially at days 1, 3, 7, 10, and 14 after BMT. Results: Plasma glutathione (GSH) and ␣-and ␥-tocopherol concentrations decreased and the GSH redox state became more oxidized after conditioning chemotherapy. Plasma cysteine concentrations were unchanged, whereas cystine concentrations increased. Plasma vitamin C and zinc concentrations and GSH peroxidase activity increased over time. Plasma ␣-tocopherol concentrations were lower in patients given standard PN. There were no differences in other plasma antioxidants between groups. Conclusions: A significant decline in GSH-glutathione disulfide, cysteine-cystine, and vitamin E status occurs after chemotherapy and BMT. Standard PN does not improve antioxidant status compared with administration of micronutrients alone. Further evaluation of PN formulations to support patients undergoing high-dose chemotherapy and BMT are needed.Am J Clin Nutr 2000;72:181-9.
Some epidemiologic studies suggest that use of vitamin C or vitamin E supplements, both potent antioxidants, may reduce the risk of bladder cancer. The authors examined the association between use of individual vitamin C and vitamin E supplements and bladder cancer mortality among 991,522 US adults in the Cancer Prevention Study II (CPS-II) cohort. CPS-II participants completed a self-administered questionnaire at enrollment in 1982 and were followed regarding mortality through 1998. During follow-up, 1,289 bladder cancer deaths occurred (962 in men and 327 in women). Rate ratios were adjusted for age, sex, cigarette smoking, education, and consumption of citrus fruits and vegetables. Regular vitamin C supplement use (>or=15 times per month) was not associated with bladder cancer mortality, regardless of duration (rate ratio (RR) = 0.91, 95% confidence interval (CI): 0.68, 1.20 for <10 years' use; RR = 1.25, 95% CI: 0.91, 1.72 for >or=10 years' use). Regular vitamin E supplement use for >or=10 years was associated with a reduced risk of bladder cancer mortality (RR = 0.60, 95% CI: 0.37, 0.96), but regular use of shorter duration was not (RR = 1.04, 95% CI: 0.77, 1.40). Results support the hypothesis that long-duration vitamin E supplement use may reduce the risk of bladder cancer mortality.
Glutamine (Gln) and keratinocyte growth factor (KGF) each stimulate intestinal epithelial cell growth, but regulatory mechanisms are not well understood. We determined whether Gln and KGF alter intra-and extracellular thiol/disulfide redox pools in Caco-2 cells cultured in oxidizing or reducing cell medium and whether such redox variations are a determinant of proliferative responses to these agents. Cells were cultured over a physiological range of oxidizing to reducing extracellular thiol/disulfide redox (E h) conditions, obtained by varying cysteine (Cys) and cystine (CySS) concentrations in cell medium. Cell proliferation was determined by 5-bromo-2-deoxyuridine (BrdU) incorporation. Gln (10 mmol/l) or KGF (10 g/l) did not alter BrdU incorporation at reducing E h (Ϫ131 to Ϫ150 mV), but significantly increased incorporation at more oxidizing E h (Gln at 0 to Ϫ109 mV; KGF at Ϫ46 to Ϫ80 mV). Cellular glutathione/glutathione disulfide (GSH/GSSG) E h was unaffected by Gln, KGF, or variations in extracellular Cys/CySS E h. Control cells largely maintained extracellular E h at initial values after 24 h (Ϫ36 to Ϫ136 mV). However, extracellular E h shifted toward a narrow physiological range with Gln and KGF treatment (Gln Ϫ56 to Ϫ88 mV and KGF Ϫ76 to Ϫ92 mV, respectively; P Ͻ 0.05 vs. control). The results indicate that thiol/disulfide redox state in the extracellular milieu is an important determinant of Caco-2 cell proliferation induced by Gln and KGF, that this control is independent of intracellular GSH redox status, and that both Gln and KGF enhance the capability of Caco-2 cells to modulate extremes of extracellular redox.
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