Suppression of the promoter effect of polyunsaturated fatty acids by the absence of dietary vitamin E in experimental mammary carcinoma

Polymeric nanocapsules prevent oxidation of core-loaded molecules: evidence based on the effects of docosahexaenoic acid and neuroprostane on breast cancer cells proliferation

Background

Nanocapsules, as a delivery system, are able to target drugs and other biologically sensitive molecules to specific cells or organs. This system has been intensively investigated as a way to protect bioactives drugs from inactivation upon interaction with the body and to ensure the release to the target. However, the mechanism of improved activity of the nanoencapsulated molecules is far from being understood at the cellular and subcellular levels. Epidemiological studies suggest that dietary polyunsaturated fatty acids (PUFA) can reduce the morbidity and mortality from breast cancer. This influence could be modulated by the oxidative status of the diet and it has been suggested that the anti-proliferative properties of docosahexaenoic acid (DHA) are enhanced by pro-oxidant agents.

Methods

The effect of encapsulation of PUFA on breast cancer cell proliferation in different oxidative medium was evaluated in vitro. We compared the proliferation of the human breast cancer cell line MDA-MB-231 and of the non-cancer human mammary epithelial cell line MCF-10A in different experimental conditions.

Results

DHA possessed anti-proliferative properties that were prevented by alpha-tocopherol (an antioxidant) and enhanced by the pro-oxidant hydrogen peroxide that confirms that DHA has to be oxidized to exert its anti-proliferative properties. We also evaluated the anti-proliferative effects of the 4(RS)-4-F_4t-neuroprostane, a bioactive, non-enzymatic oxygenated metabolite of DHA known to play a major role in the prevention of cardiovascular diseases. DHA-loaded nanocapsules was less potent than non-encapsulated DHA while co-encapsulation of DHA with H₂O₂ maintained the inhibition of proliferation. The nanocapsules slightly improves the anti-proliferative effect in the case of 4(RS)-4-F_4t-neuroprostane that is more hydrophilic than DHA.

Conclusion

Overall, our findings suggest that the sensitivity of tumor cell lines to DHA involves oxidized metabolites. They also indicate that neuroprostane is a metabolite participating in the growth reducing effect of DHA, but it is not the sole. These results also suggest that NC seek to enhance the stability against degradation, enhance cellular availability, and control the release of bioactive fatty acids following their lipophilicities.

Dietary intake of fish, ω-3 and ω-6 fatty acids and risk of colorectal cancer: A prospective study in U.S. men and women

The association between fish, ω-3 and ω-6 polyunsaturated fatty acid (PUFA) intake and risk of colorectal cancer (CRC) remains inconclusive. Recent prospective studies suggest that the relationship may vary by gender, subsite and duration of follow-up. We followed 123,529 US adults (76,386 women and 47,143 men) without a history of cancer at baseline for 24 to 26 years. Fish and PUFA intake was assessed at baseline and updated every 4 years by using a validated food-frequency questionnaire. We found no overall association between fish, ω-3 and ω-6 PUFA intake and CRC risk with hazard ratio (HR) of 1.03 [95% confidence interval (CI): 0.89-1.20] comparing marine ω-3 intake of ≥ 0.30 g/d versus <0.15 g/d among women and 1.05 (95% CI: 0.85-1.30) comparing intake of ≥ 0.41 g/d versus <0.16 g/d among men. However, fish and marine ω-3 PUFA intake appeared to be positively associated with risk of distal colon cancer in both men and women and inversely with risk of rectal cancer in men. In an analysis based on a limited number of cases, marine ω-3 PUFA intake assessed 12-16 years before diagnosis tended to be inversely associated with CRC risk in men (HR: 0.76; 95% CI: 0.52-1.10). In conclusion, although no overall association between fish, ω-3 or ω-6 PUFA intake was observed with CRC risk, marine ω-3 PUFA may be differentially associated with risk of distal colon and rectal cancers and a long latency may be needed for its protection against CRC in men.

Intakes of PUFAs were inversely associated with plasma C-reactive protein 12 years later in a middle-aged population with vitamin E intake as an effect modifier

Although n-3 (ω-3) polyunsaturated fatty acids (PUFAs) are considered anti-inflammatory components, the role of dietary n-6 PUFAs in inflammation remains controversial. Some mechanistic evidence suggests vitamin E as a potential effect modifier in the relationship between PUFAs and inflammation. Our objectives were to evaluate the long-term associations between dietary intakes of PUFAs and elevated plasma C-reactive protein (CRP) and to investigate potential effect modification by vitamin E. Individuals in the placebo group of the SU.VI.MAX trial who had available CRP measurements in 2007-2009 were included in the study (n = 843). Dietary intakes of n-3 PUFAs, n-6 PUFAs, and vitamin E were assessed in 1994-1996 with at least 6 dietary records. The logistic regression OR for elevated CRP (>3 mg/L) and 95% CI were estimated for individual PUFAs and for total n-3 and n-6 PUFA intakes. Models were adjusted for sociodemographical, lifestyle, anthropometric, and dietary variables. Interactions with vitamin E intakes were also assessed. Inverse associations were observed between intakes of total n-3 PUFAs [α-linolenic acid (ALA; 18:3n-3), ALA + eicosapentaenoic acid (EPA; 20:5n-3), EPA + docosapentaenoic acid (DPA; 22:5n-3), DPA + docosahexaenoic acid (DHA; 22:6n-3)] and n-6 PUFA [linoleic acid (18:2n-6) + arachidonic acid (20:4n-6)] and elevated CRP (OR for tertile 3 vs. tertile 1 of intake: 0.41; 95% CI: 0.21, 0.77; P-trend = 0.01; and OR 0.38; 95% CI: 0.21, 0.70; P-trend = 0.002, respectively). Stratification on vitamin E intakes showed that inverse associations between dietary n-3 and n-6 PUFA intakes and elevated CRP were substantial only in individuals with low intakes of vitamin E. Our results supported the contention that intakes of both n-3 and n-6 PUFAs are inversely associated with plasma CRP concentrations. Vitamin E is a potential effect modifier and should therefore be taken into account in such investigations. This trial was registered at clinicaltrials.gov as NCT00272428.

Dietary fat-gene interactions in cancer

Epidemiologic studies have suggested for decades an association between dietary fat and cancer risk. A large body of work performed in tissue culture and xenograft models of cancer supports an important role of various types of fat in modulating the cancer phenotype. Yet, the molecular mechanisms underlining the effects of fat on cancer initiation and progression are largely unknown. The relationships between saturated fat, polyunsaturated fat, cholesterol or phytanic acid with cancer have been reviewed respectively. However, few have considered the relationship between all of these fats and cancer. The purpose of this review is to present a more cohesive view of dietary fat-gene interactions, and outline a working hypothesis of the intricate connection between fat, genes and cancer.

The inhibitory effect of flaxseed on the growth and metastasisof estrogen receptor negative human breast cancer xenograftsis attributed to both its lignan and oil components

Our previous studies have shown that dietary flaxseed (FS) can reduce the growth and metastasis of human estrogen receptor negative (ER-) breast cancer in nude mice. The aims of our study were to determine (i) whether the tumor inhibitory effect of FS was due to its oil (FO), lignan secoisolariciresinol diglycoside (SDG), or both components, and (ii) whether the effect on tumor growth was related to increased lipid peroxidation. Athymic nude mice were orthotopically injected with ER- breast cancer cells (MDA-MB-435) and 8 weeks later were fed either the basal diet (BD) or BD supplemented with 10% FS, SDG, FO, or combined SDG and FO (SDG + FO) for 6 weeks. The SDG and FO levels were equivalent to the amounts in the 10% FS. Compared to the BD group, the tumor growth rate was significantly lower (p < 0.05) in the FS, FO, and SDG + FO groups, in concordance with decreased cell proliferation and increased apoptosis; however, these did not significantly relate to the lipid peroxidation, indexed as malonaldehyde (MDA), in the primary tumors. Lung metastasis incidence was reduced (16-70%) by all treatments, significantly in the FS and SDG + FO groups. The distant lymph node metastasis was significantly decreased (52%) only in the FO group. Although the total metastasis incidence was lowered (42%) significantly only in the SDG + FO group, all treatment groups did not differ significantly. In conclusion, FS reduced the growth and metastasis of established ER- human breast cancer in part due to its lignan and FO components, and not to lipid peroxidation.

Dietary long-chain n-3 fatty acids for the prevention of cancer: a review of potential mechanisms

Increasing evidence from animal and in vitro studies indicates that n-3 fatty acids, especially the long-chain polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid, present in fatty fish and fish oils inhibit carcinogenesis. The epidemiologic data on the association between fish consumption, as a surrogate marker for n-3 fatty acid intake, and cancer risk are, however, somewhat less consistent. This review highlights current knowledge of the potential mechanisms of the anticarcinogenic actions of n-3 fatty acids. Moreover, a possible explanation of why some epidemiologic studies failed to find an association between n-3 fatty acid intake and cancer risk is provided. Several molecular mechanisms whereby n-3 fatty acids may modify the carcinogenic process have been proposed. These include suppression of arachidonic acid-derived eicosanoid biosynthesis; influences on transcription factor activity, gene expression, and signal transduction pathways; alteration of estrogen metabolism; increased or decreased production of free radicals and reactive oxygen species; and mechanisms involving insulin sensitivity and membrane fluidity. Further studies are needed to evaluate and verify these mechanisms in humans to gain more understanding of the effects of n-3 fatty acid intake on cancer risk.

Nutritional factors and breast cancer in Mexico

Breast cancer (BC) morbidity and mortality in Mexico are on the rise, affecting younger women with more frequency. Nutritional factors are often mentioned as determinants of BC but their relevance is not well established in Latin-American countries, where dietary habits show great variation. From a study population previously assembled in Mexico City, 141 histologically confirmed cases of BC were matched by age (+/-3 yr) to an equal number of hospital controls. A food frequency questionnaire was administered to all subjects and the risk of BC was estimated in relation to the intake of selected nutrients. The findings of this study show a protective effect against BC due to a high intake of polyunsaturated fat (odds ratio, OR = 0.10, 95% CI = 0.02-0.40, P for trend = 0.001) and vitamin E (OR = 0.10, 95% CI = 0.02-0.44, P for trend = 0.003) among postmenopausal women. In addition, our findings also suggest that a high intake of total fiber (OR = 0.29, 95% CI = 0.08-1.10, P for trend = 0.080) and carotenes (OR = 0.42, 95% CI = 0.16-1.14, P for trend = 0.088) lowers BC risk among premenopausal women. The relationship between the intake of nutrients and BC risk needs further confirmation.

Enhancing effects of mustard oil on preneoplastic hepatic foci development in Wistar rats

Dietary habits are known to be the major contributory factor in the development of cancer. Mustard oil, which is extensively used in India and elsewhere as a flying and cooking medium, is reported to induce an inflammatory response. The development of altered hepatic foci is an early carcinogenic change in rat liver in diethylnitrosamine (DEN)-induced hepatocarcinogenesis. In the present study, the development of preneoplastic lesions was observed following administration of mustard oil (0.5 mL/day for 8 weeks) in DEN-initiated and partially hepatomized Wistar rats. A significant decrease in the relative and absolute liver weight of mustard oil-exposed rats was recorded. The results revealed a significant increase in the number and area of placental glutathione-S-transferase (GST-P) and gamma-glutamyl transpeptidase (GGT)-positive foci in mustard oil-administered animals. The GST-P- and GGT-positive foci were more prominent in the animals given boiled (up to 300 degrees C for 3 hours) mustard oil in comparison to the animals given fresh mustard oil. These results indicate the possible tumourigenic risk associated with mustard oil consumption.

Beneficial and adverse effects of chemopreventive agents

The beneficial and adverse effects of some chemopreventive agents, such as Vitamins A, C, E, beta-carotene, indole-3-carbinol, capsaicin, garlic, and aloe are reviewed. Two large randomized trials with a lung cancer endpoint, the Alpha-Tocopherol, Beta-Carotene (ATBC) Prevention Study and the Beta-Carotene and Retinol Efficacy Trial (CARET), suggested that antioxidants might be harmful in smokers. However, the results of the Linxian study and of the ATBC or the CARET studies were significantly different in this respect, and therefore, the relationship between antioxidant and carcinogenesis remains open to debate. Indole-3-carbinol has cancer promoting activities in the colon, thyroid, pancreas, and liver, whereas capsaicin alters the metabolism of chemical carcinogens and may promote carcinogenesis at high doses. Organosulfur compounds and selenium from garlic have no or a little enhancing effect on cancer promotion stage. Information upon chemopreventive mechanisms that inhibit carcinogenesis is imperfect, although the causes and natures of certain human cancers are known. Therefore, definitive preventive guidelines should be carefully offered for various types of tumors, which properly consider ethnic variations, and the efficacies and the safety of chemopreventive agents.

Effect of an alpha-linolenic acid-rich diet on rat mammary tumor growth depends on the dietary oxidative status

To investigate whether the oxidative status of an 18:3(n-3) polyunsaturated fatty acid (PUFA)-enriched diet could modulate the growth of chemically induced rat mammary tumors, three independent experiments were performed. Experiments I and II examined the variation of tumor growth by addition of antioxidant (vitamin E) or a prooxidant system (sodium ascorbate/2-methyl-1,4-naphthoquinone) to a 15% linseed oil diet rich in 18:3(n-3). Experiment III addressed the role of PUFA in the tumor growth modulation by vitamin E. For this purpose, we compared the effect of vitamin E in 15% fat diets containing a high level of 18:3(n-3) (linseed oil, high-PUFA diet) or devoid of 18:3(n-3) (hydrogenated palm/sunflower oil, low-PUFA diet). In Experiments I-III, tumor growth increased in the presence of vitamin E compared with control (without vitamin E). Furthermore, it decreased when prooxidant was added. In contrast, no difference was observed when the diet was low in PUFA, suggesting that sensitivity of PUFA to peroxidation may interfere with tumor growth. This observation was supported by growth kinetic parameter analysis, which indicated that tumor growth resulted from variations in cell loss but not from changes in cell proliferation. These data show that, in vivo, PUFA effects on tumor growth are highly dependent on diet oxidative status.

N-3, n-6 and n-9 dietary fatty acids modulate the growth parameters of murine salivary gland tumors induced by dimethylbenzanthracene

Variations in dietary fatty acid composition influence the biological behaviour of certain tumours. Diets enriched with oleic acid (18:1 n-9) seem to promote tumour progression on several lines due perhaps to the development of essential fatty acid deficiency (EFAD), whereas n-3 fatty acids have a protective effect. Since the role played by lipids on salivary gland tumorigenesis has not yet been studied, an experimental model is presented. BALB/c mice were fed on four different diets: control, corn oil, fish oil and olein groups. Salivary gland adenocarcinomas were chemically induced by using 9,10-dimethyl-1,2-benzanthracene. Animals were sacrificed at the 20th post-injection week and several tumour parameters were analysed. Linoleic acid showed no promoting activity. Tumour size was larger in the olein group than in fish oil fed mice, indicating that the oleic acid, linked to the induced EFAD condition, has a protumorigenic activity whereas n-3 polyunsaturated fatty acids appear to exert a protective effect.

n-3 polyunsaturated fatty acids and cancer

n-3 Polyunsaturated fatty acids are promising molecules in cancer prevention and the potentiation of cancer treatment. Recent studies have highlighted the importance of their interactions with other food components. Their effects on tumor growth depend upon background levels of n-6 polyunsaturated fatty acids and antioxidants, and this could account for previously inconsistent results in experimental carcinogenesis. Recognition of the role of lipoperoxidation in the anti-tumor effects of polyunsaturated fatty acids, which is apparent in a variety of in-vitro or in-vivo systems, has been a major advance in the field. Consequently, n-3 polyunsaturated fatty acids appear to be excellent substrates for lipid peroxidation in situations where an oxidative stress is involved, such as in the action of several cytotoxic agents in the treatment of cancer.