Dilprit Bagga

Differential effects of prostaglandin derived from ω-6 and ω-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion

Omega-6 (ω-6) polyunsaturated fatty acids (PUFA), abundant in the Western diet, are precursors for a number of key mediators of inflammation including the 2-series of prostaglandins (PG). PGE2, a cyclooxygenase (COX) metabolite of arachidonic acid, a ω-6 PUFA, is a potent mediator of inflammation and cell proliferation. Dietary supplements rich in ω-3 PUFA reduce the concentrations of 2-series PG and increase the synthesis of 3-series PG (e.g., PGE3), which are believed to be less inflammatory. However, studies on cellular consequences of increases in 3-series PG in comparison to 2-series PG have not been reported. In this study, we compared the effects of PGE2 and PGE3 on (i) cell proliferation in NIH 3T3 fibroblasts, (ii) expression and transcriptional regulation of the COX-2 gene in NIH 3T3 fibroblasts, and (iii) the production of an inflammatory cytokine, IL-6, in RAW 264.7 macrophages. PGE3, unlike PGE2, is not mitogenic to NIH 3T3 fibroblasts. PGE2 and PGE3 both induce COX-2 mRNA via similar signaling mechanisms; however, compared with PGE2, PGE3 is significantly less efficient in inducing COX-2 gene expression. Furthermore, although both PGE2 and PGE3 induce IL-6 synthesis in RAW 264.7 macrophages, PGE3 is substantially less efficient compared with PGE2. We further show that increasing the ω-3 content of membrane phospholipid results in a decrease in mitogen-induced PGE2 synthesis. Taken together, our data suggest that successful replacement of ω-6 PUFA with ω-3 PUFA in cell membranes can result in a decreased cellular response to mitogenic and inflammatory stimuli.

Effect of Altering Dietary ω-6/ω-3 Fatty Acid Ratios on Prostate Cancer Membrane Composition, Cyclooxygenase-2, and Prostaglandin E2

Purpose: To determine whether altering the dietary content of ω-6 (n-6) and ω-3 (n-3) polyunsaturated fatty acids affects the growth of androgen-sensitive prostate cancer xenografts, tumor membrane fatty acid composition, and tumor cyclooxygenase-2 and prostaglandin E2 (PGE2) levels. Experimental Design: Individually caged male severe combined immunodeficiency mice were fed isocaloric 20% kcal fat diets with the fat derived either primarily from n-6 fatty acids (n-6 group) or with the fat consisting of n-6 and n-3 fatty acids in a ratio of 1:1 (n-3 group), and injected s.c. with Los Angeles Prostate Cancer 4 (LAPC-4) cells. Tumor volumes and mouse weights were measured weekly, caloric intake was measured 3 days per week, and tumors and serum were harvested at 8 weeks postinjection. Results: Tumor growth rates, final tumor volumes, and serum prostate-specific antigen levels were reduced in the n-3 group relative to the n-6 group. The n-3 group tumors had decreased proliferation (Ki67 staining) and increased apoptosis (terminal nucleotidyl transferase–mediated nick end labeling staining). In vitro proliferation of LAPC-4 cells in medium containing n-3 group serum was reduced by 22% relative to LAPC-4 cells cultured in medium containing serum from the n-6 group. The n-6/n-3 fatty acid ratios in serum and tumor membranes were lower in the n-3 group relative to the n-6 group. In addition, n-3 group tumors had decreased cyclooxygenase-2 protein and mRNA levels, an 83% reduction in PGE2 levels, and decreased vascular endothelial growth factor expression. Conclusion: These results provide a sound basis for clinical trials evaluating the effect of dietary n-3 fatty acids from fish oil on tumor PGE2 and membrane fatty acid composition, and serum and tumor biomarkers of progression in men with prostate cancer.

Modulation of omega-3/omega-6 polyunsaturated ratios with dietary fish oils in men with prostate cancer

OBJECTIVES The results of epidemiologic and animal studies support the role of a low-fat diet supplemented with omega-3 fatty acids contained in fish oil in preventing the development and progression of prostate cancer. As a first step in studying the role of a low-fat, fish oil-supplemented (LF/FOS) diet in a clinical setting, we conducted a prospective study in men with untreated prostate cancer to evaluate whether a 3-month dietary intervention affects the ratio of omega-3 to omega-6 fatty acids in plasma and gluteal fat. In addition, we evaluated the feasibility of studying cyclooxygenase-2 (COX-2) expression in serial prostate needle biopsy specimens before and after the diet. METHODS Nine men with untreated prostate cancer consumed an LF/FOS diet for 3 months. Plasma, gluteal adipose tissue, and prostate needle biopsy specimens were obtained from each patient before and after the intervention. The fatty acid compositions of the plasma and gluteal adipose tissue were determined by gas-liquid chromatography, and the COX-2 expression in the prostatic tissue specimens was determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS Short-term intervention with an LF/FOS diet caused a significant increase in the omega-3/omega-6 fatty acid ratio in plasma (P = 0.002) and gluteal adipose tissue (P = 0.002) in men with prostate cancer. The COX-2 expression in prostatic tissue was quantitated by RT-PCR in 7 of 9 patients, and COX-2 expression decreased in 4 of these 7 patients. CONCLUSIONS A short-term dietary intervention in men with prostate cancer leads to a significant increase in the omega-3/omega-6 fatty acid ratios in plasma and adipose tissue. The potential for this diet to prevent the development and progression of prostate cancer by way of altered COX-2 expression and prostaglandin production in prostatic tissue requires further study.

Long-Chain n-3-to-n-6 Polyunsaturated Fatty Acid Ratios in Breast Adipose Tissue From Women With and Without Breast Cancer

Animal studies suggest that dietary polyunsaturated fatty acids (PUFAs) of the n-6 class, found in corn and safflower oils, may be precursors of intermediates involved in the development of mammary tumors, whereas long-chain (LC) n-3 PUFAs, found in fish oil, can inhibit these effects. This case-control study was designed to examine the relationship between the PUFA composition of breast adipose tissue and the risk of breast cancer. Using fatty acid levels in breast adipose tissue as a biomarker of past qualitative dietary intake of fatty acids, we examined the hypothesis that breast cancer risk is negatively associated with specific LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) and positively associated with n-6 PUFAs (linoleic acid and arachidonic acid). Breast adipose tissue was collected from 73 breast cancer patients and 74 controls with macromastia. The fatty acid levels were determined by gas-liquid chromatography. A logistic regression model was used to obtain odds ratio estimates while adjusting for age. The age-adjusted n-6 PUFA (linoleic acid and arachidonic acid) content was significantly higher in cases than in controls (P = 0.02). There was a trend in the age-adjusted data suggesting that, at a given level of n-6 PUFA, LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) may have a protective effect (P = 0.06). A similar inverse relationship was observed with LC n-3-to-n-6 ratio when the data were adjusted for age (P = 0.09). We conclude that total n-6 PUFAs may be contributing to the high risk of breast cancer in the United States and that LC n-3 PUFAs, derived from fish oils, may have a protective effect.

Effects of a very low fat, high fiber diet on serum hormones and menstrual function implications for breast cancer prevention

Background. Low fat, high fiber dietary interventions that decrease blood estrogen levels may reduce breast cancer risk. Asian women consuming their traditional low fat, high fiber diets have lower blood estrogen levels before and after menopause and lower rates of breast cancer compared with Western women. The current controlled feeding study of premenopausal women was designed to determine the effects of a very low fat (10% of calories) and high fiber (35–45g/day) diet on blood estrogen levels and menstrual function.

Preadipocytes stimulate breast cancer cell growth

Mammary fat may affect human breast cancer development. In this study a novel coculture system was used to investigate stromal-epithelial cell interactions in vitro. The extent of differentiation of a feeder layer of 3T3-L1 preadipocytes affected the clonal growth of breast cancer cells under anchorage-independent conditions. When the feeder-layer preadipocytes were proliferating, the clonal growth of estrogen receptor-positive MCF-7 and estrogen receptor-negative MDA-MB-231 and MDA-MB-436 cells was stimulated by 100%, 43%, and 60%, respectively. In contrast, after differentiation the feeder layer of mature adipocytes inhibited clonal growth of breast cancer cell lines by 60%. No clonal growth stimulation of human pancreatic (Panc-1) or prostatic (PC-3) cancer cells was noted when these cells were grown under identical conditions with a proliferating 3T3-L1 cell feeder layer. These findings suggest that proliferating preadipocytes may be associated with factors that specifically stimulate breast cancer cell growth.

Stromal-epithelial cell interactions in breast cancer.

The vast majority of breast cancers originate from breast ductal epithelial cells and are either infiltrating ductal or intraductal breast cancers (1). These cells exist in a local microenvironment in which both stromal cell products and blood-borne factors may influence both transformation and tumor growth. Breast ductal epithelial cells and stromal cells have a number of things in common. Both cell types produce protein growth factors and active steroids. At the same time both cell types respond to stimulation by peptides and steroids. This chapter will explore the hypothesis that these two cell types interact in both paracrine and endocrine fashion to affect breast epithelial growth, tumor development, and breast tumor metastasis.

Adipose tissue and the effects of fat and calories on breast tumorigenesis in rats

A high fat diet fed ad libitum will promote breast tumorigenesis in rats while caloric restriction of the same high fat diet counteracts this promotional effect. The present study examined the effects of dietary fat and calorie intake on adipose tissue weight and fatty acid composition and on tumor incidence and development. The sites of adipose tissue chosen were the mammary fat pad, representing adipose tissue in the immediate location of the studied tumor, and the abdominal fat depot which in humans has been associated with an increased risk of breast cancer. High (20% corn oil) and low (5% corn oil) fat test diets were offered ad libitum and at 40% restriction levels. In agreement with prior studies, caloric restriction of both high and low fat diets led to marked decreases in tumor incidence (63 to 68% versus 21%), tumor burden (1.84 to 2.05 versus 0.37 to 0.43 tumors/rat), and tumor weight (7.1 to 11.9 versus 1.4 to 2.2 g) at the time of sacrifice (133 days post-DMBA). While final body weights were reduced in proportion to the level of caloric restriction (290 to 291 g versus 184 to 201 g), abdominal fat (8.8 to 9.2 versus 0.9 to 1.6 g), and mammary fat weights (3.1 to 4.1 versus 0.7 to 2.0 g) were reduced markedly in association with the decrease in tumorigenesis. While both tumor and mammary fat were enriched with linoleate reflecting the fatty acid composition of dietary fat, the ratio of arachidonic acid to linoleic acid was higher in tumor tissue than in surrounding normal mammary tissue in both the phospholipid (0.78 versus 0.18) and neutral lipid fractions (0.22 versus 0.03). These observations are consistent with the concept that increases in fat tissue mass in abdominal and mammary fat depots may mediate some of the promotional effects of high fat and high calorie diets. Restriction of dietary fat and calories to reduce body fat and strategies to modify the composition of stored lipids in fat depots may offer nutritional approaches to breast cancer prevention and treatment.