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      The yin and yang of 15-lipoxygenase-1 and delta-desaturases: Dietary omega-6 linoleic acid metabolic pathway in prostate

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          Abstract

          One of the major components in high-fat diets (Western diet) is the omega (ω, n)-6 polyunsaturated fatty acid (PUFA) called linoleic acid (LA). Linoleic acid is the precursor for arachidonic acid (AA). These fatty acids are metabolized to an array of eicosanoids and prostaglandins depending upon the enzymes in the pathway. Aberrant expression of the catabolic enzymes such as cyclooxygenases (COX-1 and/or -2) or lipoxygenases (5-LO, 12-LO, 15-LO-1, and 15-LO-2) that convert PUFA either AA and/or LA to bioactive lipid metabolites appear to significantly contribute to the development of PCa. However, PUFA and its cellular interactions in PCa are poorly understood. We therefore examined the mRNA levels of key enzymes involved in the LA and AA pathways in 18 human donor (normal) prostates compared to 60 prostate tumors using the Affymetrix U95Av2 chips. This comparative (normal donor versus prostate cancer) study showed that: 1) the level of 15-LO-1 expression (the key enzyme in the LA pathway) is low ( P < 0.001), whereas the levels of delta-5 desaturase ( P < 0.001, the key enzyme in the AA pathway), delta-6 desaturase ( P = 0.001), elongase ( P = 0.16) and 15-lipoxygenase-2 (15-LO-2, P = 0.74) are higher in donor (normal) prostates, and 2) Contrary to the observation in the normal tissues, significantly high levels of only 15-LO-1; whereas low levels of delta-6 desaturase, elongase, delta-5 desaturase and 15-LO-2 respectively, were observed in PCa tissues. Although the cyclooxygenase (COX)-1 and COX-2 mRNA levels were high in PCa, no significant differences were observed when compared in donor tissues. Our study underscores the importance of promising dietary intervention agents such as the omega-3 fatty acids as substrate competitors of LA/AA, aimed primarily at high 15-LO-1 and COX-2 as the molecular targets in PCa initiation and/or progression.

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          Transgenic mice: fat-1 mice convert n-6 to n-3 fatty acids.

          Mammals cannot naturally produce omega-3 (n-3) fatty acids--beneficial nutrients found mainly in fish oil--from the more abundant omega-6 (n-6) fatty acids and so they must rely on a dietary supply. Here we show that mice engineered to carry a fat-1 gene from the roundworm Caenorhabditis elegans can add a double bond into an unsaturated fatty-acid hydrocarbon chain and convert n-6 to n-3 fatty acids. This results in an abundance of n-3 and a reduction in n-6 fatty acids in the organs and tissues of these mice, in the absence of dietary n-3. As well as presenting an opportunity to investigate the roles played by n-3 fatty acids in the body, our discovery indicates that this technology might be adapted to enrich n-3 fatty acids in animal products such as meat, milk and eggs.
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            Complementary/alternative medicine use in a comprehensive cancer center and the implications for oncology.

            Oncologists are aware that their patients use complementary/alternative medicine (CAM). As cancer incidence rates and survival time increase, use of CAM will likely increase. This study assessed the prevalence and predictors of CAM use in a comprehensive cancer center. Subjects were English-speaking cancer patients at least 18 years of age, attending one of eight outpatient clinics at The University of Texas M.D. Anderson Cancer Center, Houston, TX, between December 1997 and June 1998. After giving written informed consent, participants completed a self-administered questionnaire. Differences between CAM users and nonusers were assessed by chi(2) and univariate logistic regression analysis. A multivariate logistic regression model identified the simultaneous impact of demographic, clinical, and treatment variables on CAM use; P values were two-sided. Of the 453 participants (response rate, 51.4%), 99.3% had heard of CAM. Of those, 83.3% had used at least one CAM approach. Use was greatest for spiritual practices (80.5%), vitamins and herbs (62.6%), and movement and physical therapies (59.2%) and predicted (P <.001) by sex (female), younger age, indigent pay status, and surgery. After excluding spiritual practices and psychotherapy, 95.8% of participants were aware of CAM and 68.7% of those had used CAM. Use was predicted (P <.0001) by sex (female), education, and chemotherapy. In most categories, CAM use was common among outpatients. Given the number of patients combining vitamins and herbs with conventional treatments, the oncology community must improve patient-provider communication, offer reliable information to patients, and initiate research to determine possible drug-herb-vitamin interactions.
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              A prospective study of dietary fat and risk of prostate cancer.

              The strong correlation between national consumption of fat and national rate of mortality from prostate cancer has raised the hypothesis that dietary fat increases the risk of this malignancy. Case-control and cohort studies have not consistently supported this hypothesis. We examined prospectively the relationship between prostate cancer and dietary fat, including specific fatty acids and dietary sources of fat. We examined the relationship of fat consumption to the incidence of advanced prostate cancer (stages C, D, or fatal cases) and to the total incidence of prostate cancer. We used data from the Health Professionals Follow-up Study, which is a prospective cohort of 51529 U.S. men, aged 40 through 75, who completed a validated food-frequency questionnaire in 1986. We sent follow-up questionnaires to the entire cohort in 1988 and 1990 to document new cases of a variety of diseases and to update exposure information. As of January 31, 1990, 300 new cases of prostate cancer, including 126 advanced cases, were documented in 47855 participants initially free of diagnosed cancer. The Mantel-Haenszel summary estimator was used to adjust for age and other potentially confounding variables. Multiple logistic regression was used to estimate relative risks (RRs) when controlling simultaneously for more than two covariates. Total fat consumption was directly related to risk of advanced prostate cancer (age- and energy-adjusted RR = 1.79, with 95% confidence interval [CI] = 1.04-3.07, for high versus low quintile of intake; P [trend] = .06). This association was due primarily to animal fat (RR = 1.63; 95% CI = 0.95-2.78; P [trend] = .08), but not vegetable fat. Red meat represented the food group with the strongest positive association with advanced cancer (RR = 2.64; 95% CI = 1.21-5.77; P = .02). Fat from dairy products (with the exception of butter) or fish was unrelated to risk. Saturated fat, monounsaturated fat, and alpha-linolenic acid, but not linoleic acid, were associated with advanced prostate cancer risk; only the association with alpha-linolenic acid persisted when saturated fat, monounsaturated fat, linoleic acid, and alpha-linolenic acid were modeled simultaneously (multivariate RR = 3.43; 95% CI = 1.67-7.04; P [trend] = .002). The results support the hypothesis that animal fat, especially fat from red meat, is associated with an elevated risk of advanced prostate cancer. These findings support recommendations to lower intake of meat to reduce the risk of prostate cancer. The potential roles of carcinogens formed in cooking animal fat and of alpha-linolenic acid in the progression of prostate cancer need to be explored.
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                Author and article information

                Journal
                J Carcinog
                Journal of Carcinogenesis
                BioMed Central (London )
                1477-3163
                2006
                27 March 2006
                : 5
                : 9
                Affiliations
                [1 ]Department of Urology and University of Pittsburgh Cancer Institute, 5200 Center Ave., SHMC-Suite G-37, Pittsburgh, PA, 15232, USA
                [2 ]Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA
                [3 ]Department of Mathematics and Computer Science, Duquesne University, Pittsburgh, PA, 15282, USA
                [4 ]Department of Pathology and University of Pittsburgh Cancer Institute, 5200 Center Ave., Pittsburgh, PA, 15232, USA
                Article
                1477-3163-5-9
                10.1186/1477-3163-5-9
                1440856
                16566819
                277f3967-a172-4989-afdf-01b40570b938
                Copyright © 2006 Kelavkar et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 11 November 2005
                : 27 March 2006
                Categories
                Short Paper

                Oncology & Radiotherapy
                Oncology & Radiotherapy

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