Mechanisms of omega-3 fatty acid-induced growth inhibition in MDA-MB-231 human breast cancer cells

N-3 polyunsaturated fatty acids regulate lipid metabolism through several inflammation mediators: mechanisms and implications for obesity prevention

Obesity is a growing problem that threatens the health and welfare of a large proportion of the human population. The n-3 polyunsaturated fatty acids (PUFA) are dietary factors that have potential to facilitate reduction in body fat deposition and improve obesity-induced metabolic syndromes. The n-3 PUFA up-regulate several inflammation molecules including serum amyloid A (SAA), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in hepatocytes and adipocytes. Actions of these inflammation mediators resemble those of n-3 PUFA in the modulation of many lipid metabolism-related genes. For instance, they both suppress expressions of perilipin, sterol regulatory element binding protein-1 (SREBP-1) and lipoprotein lipase (LPL) to induce lipolysis and reduce lipogenesis. This review will connect these direct or indirect regulating pathways between n-3 PUFA, inflammation mediators, lipid metabolism-related genes and body fat reduction. A thorough knowledge of these regulatory mechanisms will lead us to better utilization of n-3 PUFA to reduce lipid deposition in the liver and other tissues, therefore presenting an opportunity for developing new strategies to treat obesity.

Dietary omega-3 polyunsaturated fatty acids suppress expression of EZH2 in breast cancer cells

The polycomb group (PcG) protein, enhancer of zeste homologue 2 (EZH2), is overexpressed in several human malignancies including breast cancer. Aberrant expression of EZH2 has been associated with metastasis and poor prognosis in cancer patients. Despite the clear role of EZH2 in oncogenesis and therapy failure, not much is known about chemotherapeutics and chemopreventive agents that can suppress its expression and activity. Here, we show that dietary omega-3 (omega-3) polyunsaturated fatty acids (PUFAs) can regulate the expression of EZH2 in breast cancer cells. The treatment of breast cancer cells with omega-3 PUFAs, but not omega-6 PUFAs, led to downregulation of EZH2. Studies using proteosome inhibitor MG132 suggested that omega-3 PUFAs induce degradation of the PcG protein EZH2 through posttranslational mechanisms. Furthermore, downregulation of EZH2 by omega-3 PUFAs was accompanied by a decrease in histone 3 lysine 27 trimethylation (H3K27me3) activity of EZH2 and upregulation of E-cadherin and insulin-like growth factor binding protein 3, which are known targets of EZH2. Treatment with omega-3 PUFAs also led to decrease in invasion of breast cancer cells, an oncogenic phenotype that is known to be associated with EZH2. Thus, our studies suggest that the PcG protein EZH2 is an important target of omega-3 PUFAs and that downregulation of EZH2 may be involved in the mediation of anti-oncogenic and chemopreventive effects of omega-3 PUFAs.

Eleostearic Acid inhibits breast cancer proliferation by means of an oxidation-dependent mechanism

Eleostearic acid (alpha-ESA) is a conjugated linolenic acid that makes up approximately 60% of Momordica charantia (bitter melon) seed oil. Prior work found that water extract from bitter melon was able to inhibit breast cancer. Here, we investigated effects of alpha-ESA on both estrogen receptor (ER)-negative MDA-MB-231 (MDA-wt) and ER-positive MDA-ERalpha7 human breast cancer cells. We found that alpha-ESA inhibited proliferation of both MDA-wt and MDA-ERalpha7 cells, whereas conjugated linoleic acid had comparatively weak antiproliferative activity at 20 to 80 micromol/L concentrations. We also found that alpha-ESA (40 micromol/L) treatment led to apoptosis in the range of 70% to 90% for both cell lines, whereas conjugated linoleic acid (40 micromol/L) resulted in only 5% to 10% apoptosis, similar to results for control untreated cells. Addition of alpha-ESA also caused loss of mitochondrial membrane potential and translocation of apoptosis-inducing factor as well as endonuclease G from the mitochondria to the nucleus. Additionally, alpha-ESA caused a G(2)-M block in the cell cycle. We also investigated the potential for lipid peroxidation to play a role in the inhibitory action of alpha-ESA. We found that when the breast cancer cells were treated with alpha-ESA in the presence of the antioxidant alpha-tocotrienol (20 micromol/L), the growth inhibition and apoptosis effects of alpha-ESA were lost. An AMP-activated protein kinase inhibitor (Dorsomorphin) was also able to partially abrogate the effects of alpha-ESA, whereas a caspase inhibitor (BOC-D-FMK) did not. These results illustrate that alpha-ESA can block breast cancer cell proliferation and induce apoptosis through a mechanism that may be oxidation dependent.

Marine n-3 polyunsaturated fatty acids in adipose tissue and breast cancer risk: a case-cohort study from Denmark

OBJECTIVE

The aim of this study was to investigate the association between the content of marine n-3 polyunsaturated fatty acids (PUFA) in adipose tissue, a biomarker for the long-term intake of seafood, and the subsequent development of breast cancer (BC).

DESIGN

We designed a case-cohort study based on a cohort of healthy Danish women, who in the 1990 s donated adipose tissue biopsies to a biobank in order to investigate the role of diet for the development of cancer and chronic disease. During follow-up, incident cases of BC were identified through national registries, and the content of n-3 PUFA in adipose tissue was compared between cases and the cohort sample.

RESULTS

During follow-up, 463 new cases of BC were identified. After adjusting for potential confounders, no significant association between the content of marine n-3 PUFA and BC was found. When comparing the highest with the lowest quintile, the hazard ratio (HR) was 0.96 (95% CI 0.64-1.43) for total marine n-3 PUFA, 0.84 (95% CI 0.58-1.23) for eicosapentaenoic acid (EPA), and 1.08 (95% CI 0.73-1.58) for docosahexaenoic acid (DHA).

CONCLUSION

This study does not indicate any association between the content of total or individual marine n-3 PUFA in adipose tissue and development of BC.

Antineoplastic effects of n-3 polyunsaturated fatty acids in combination with drugs and radiotherapy: preventive and therapeutic strategies

Many data support the beneficial effect of n-3 polyunsaturated fatty acids (PUFAs) as chemopreventive and chemotherapeutic agents in the treatment of several chronic pathologies including cancer. Different molecular mechanisms have been proposed to explain their effects, including alterations in arachidonic acid oxidative metabolism and metabolic conversion of n-3 PUFAs to novel discovered bioactive derivatives; modification of oxidative stress; changes in cell membrane fluidity and structure and altered metabolism and function of membrane proteins. Considerable knowledge has been recently gathered on the possible beneficial effects of n-3 PUFAs administered in combination with different antineoplastic drugs and radiotherapy against melanoma, leukemia, neuroblastoma, and colon, breast, prostate, and lung cancer. The efficacy of these combinations has been demonstrated both in vivo and in vitro, and clinical trials have also been conducted. The aim of this review is to analyze all the n-3 PUFA combinations investigated so far, their efficacy, and the possible molecular mechanisms involved. It would be highly auspicable that the detailed analysis of the literature in this field could further support the common use of n-3 PUFAs in combination with other chemopreventive agents and warrant more clinical investigations designed to test the effectiveness of n-3 PUFA treatments coupled with conventional antineoplastic therapies.

Docosahexaenoic acid downregulates phenobarbital-induced cytochrome P450 2B1 gene expression in rat primary hepatocytes via the c-Jun NH2-terminal kinase mitogen-activated protein kinase pathway

Mitogen-activated protein kinase (MAPK) pathways play central roles in the transduction of extracellular stimuli into cells and the regulation of expression of numerous genes. Docosahexaenoic acid (DHA) was shown to be involved in the regulation of expression of drug metabolizing enzymes (DMEs) in rat primary hepatocytes in response to xenobiotics. Cytochrome P450 2B1 (CYP 2B1) is a DME that is dramatically induced by phenobarbital-type inducers. The constitutive androstane receptor (CAR) plays a critical role in regulating the expression of DMEs, and the phosphorylation/dephosphorylation of CAR is an important event in CYP 2B1 expression. In the present study, we determined the effect of DHA on MAPK transactivation and its role in CYP 2B1 expression induced by phenobarbital. c-Jun NH2-terminal kinase (JNK) JNK1/2 and ERK1/2 were activated by phenobarbital in a dose-dependent manner. DHA (100 muM) inhibited JNK1/2 and ERK2 activation induced by phenobarbital in a time-dependent manner. Both SP600125 (a JNK inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited CYP 2B1 protein and mRNA expression induced by phenobarbital. SB203580 significantly increased the intracellular 3'-5'-cyclic adenosine monophosphate (cAMP) concentration compared with a control group (p < 0.05). Our results suggest that inhibition of JNK activation by DHA is at least part of the mechanisms of DHA's downregulation of CYP 2B1 expression induced by phenobarbital.

Docosahexaenoic acid down-regulates phenobarbital-induced cytochrome P450 2B1 gene expression in rat primary hepatocytes via the sphingomyelinase/ceramide pathway

Docosahexaenoic acid (DHA) regulates the expression of cytochrome P450 2B1 (CYP 2B1) in rat primary hepatocytes in response to xenobiotics. Ceramide, a lipid signaling molecule, is involved in various physiological processes and can be generated by the hydrolysis of sphingomyelin via sphingomyelinase (SMase). DHA activates SMase and increases ceramide formation in vitro. Ceramides differentially enhance adenylyl cyclase activity in vitro depending on the chain length of their fatty acids. In addition, the cAMP-dependent PKA pathway down-regulates CYP 2B1 expression induced by phenobarbital (PB). In the present study, we determined the effect of DHA on SMase transactivation and the downstream pathway in CYP 2B1 expression induced by PB. SMase was activated by DHA 2 h after treatment, and D609 (an SMase inhibitor) attenuated the inhibition of PB-induced CYP 2B1 expression by DHA. Ceramide formation reached a maximum 3 h after DHA administration. C2-ceramide dose-dependently inhibited PB-induced CYP 2B1 expression and increased intracellular cAMP concentrations. SQ22536 (an adenylyl cyclase inhibitor) and H89 (a PKA-specific inhibitor) partially reversed the inhibition of PB-induced CYP 2B1 expression by C2-ceramide. These results suggest that stimulation of SMase, generation of ceramide and activation of the cAMP-dependent PKA pathway are involved in the inhibition exerted by DHA.

Docosahexaenoic acid induces proteasome-dependent degradation of estrogen receptor alpha and inhibits the downstream signaling target in MCF-7 breast cancer cells

About two thirds of breast cancers in women are hormone-dependent and require estrogen for growth, its effects being mainly mediated through estrogen receptor alpha (ERalpha). Docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA, 20:4n-6) have opposite effects on carcinogenesis, with DHA suppressing and AA promoting tumor growth both in vitro and in vivo. However, the mechanism is not clear. Here, we examined whether the effect is mediated through changes in ERalpha distribution. MCF-7 cells, an ERalpha-positive human breast cancer cell line, was cultured in estrogen-free medium containing 0, 10 or 60 microM DHA or AA, then were stimulated with estradiol. DHA supplementation resulted in down-regulation of ERalpha expression (particularly in the extranuclear fraction), a reduction in phosphorylated MAPK, a decrease in cyclin D1 levels and an inhibition in cell viability. In contrast, AA had no such effects. The DHA-induced decrease in ERalpha expression resulted from proteasome-dependent degradation and not from decreased ERalpha mRNA expression. We propose that breast cancer cell proliferation is inhibited by DHA through proteasome-dependent degradation of ERalpha, reduced cyclin D1 expression and inhibition of MAPK signaling.

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP.

On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.

Fatty acid uptake by breast cancer cells (MDA-MB-231): effects of insulin, leptin, adiponectin, and TNFalpha

In order to exert metabolic effects, fatty acids must be taken up by cells and metabolize effectively to different classes of cellular lipids (triacylglycerols, phospholipids, etc.) for incorporation into different cellular and intracellular compartments. Therefore, the main aim of the present study is to investigate the uptake and metabolism of fatty acids representing three different series of fatty acids such as oleic acid, 18:1n-9 (OA), arachidonic acid, 20:4n-6 (AA), and eicosapentaneoic acid, 20:5n-3 (EPA) by breast cancer cells, MDA-MB-231. Moreover, we investigated the effects of insulin and several adipokines on the fatty acid uptake by these cells as obesity and insulin resistance syndrome have been suggested to affect breast cancer risk. We report for the first time that AA was predominantly taken up by these cells compared with EPA and OA. Pre-incubation of these cells with TNFalpha stimulated most of the uptake of EPA (30%), whereas uptake of OA and AA was stimulated only 10-15% compared with the controls. Insulin, leptin, and adiponectin had no effect on fatty acid uptake by these cells. Together these results demonstrate that preferential uptake of AA in MDA-MB-231 cells, and the fatty acid uptake activity of these cells is influenced by TNFalpha.

Expression of the fat-1 gene diminishes prostate cancer growth in vivo through enhancing apoptosis and inhibiting GSK-3 beta phosphorylation

Epidemiologic studies inclusively indicate that "unhealthy" dietary fat intake is one of the potential risk factors for cancer. In dietary fat, there are two types of polyunsaturated fatty acids (PUFA), omega-3 (n-3) and omega-6 (n-6). Numerous studies support that the ratio of n-6/n-3 affects tumorigenesis. It was reported that adenoviral transfer of the fat-1 gene, which converts n-6 to n-3, into breast and lung cancer cells had an antitumor effect in vitro. However, the effects of the fat-1 gene expression on tumor growth in vivo have not been studied and the mechanisms remain unclear. Accordingly, prostate cancer DU145 and PC3 cells were transfected with either the fat-1 gene or a control vector. The cells that expressed the fat-1 gene had a lower n-6/n-3 PUFA ratio compared with the cells that expressed the control vector. The fat-1 gene expression significantly inhibited prostate cancer cell proliferation and invasion in vitro. The fat-1 and control vector-transfected prostate cancer cells were s.c. implanted into severe combined immunodeficient mice for 6 weeks. The fat-1 gene expression significantly diminished tumor growth in vivo, but the control vector had no effect. Finally, we evaluated signaling pathways that may be important for fat-1 gene function. Administration of n-3 PUFA induced caspase-3-mediated prostate cancer cell apoptosis in vitro. The fat-1 gene expression inhibited prostate cancer cell proliferation via reduction of GSK-3beta phosphorylation and subsequent down-regulation of both beta-catenin and cyclin D1. These results suggest that fat-1 gene transfer directly into tumor cells could be used as a novel therapeutic approach.

Fish oil targets PTEN to regulate NFkappaB for downregulation of anti-apoptotic genes in breast tumor growth

The molecular mechanism for the beneficial effect of fish oil on breast tumor growth is largely undefined. Using the xenograft model in nude mice, we for the first time report that the fish oil diet significantly increased the level of PTEN protein in the breast tumors. In addition, the fish oil diet attenuated the PI 3 kinase and Akt kinase activity in the tumors leading to significant inhibition of NFkappaB activation. Fish oil diet also prevented the expression of anti-apoptotic proteins Bcl-2 and Bcl-XL in the breast tumors with concomitant increase in caspase 3 activity. To extend these findings we tested the functional effects of DHA and EPA, the two active omega-3 fatty acids of fish oil, on cultured MDA MB-231 cells. In agreement with our in vivo data, DHA and EPA treatment increased PTEN mRNA and protein expression and inhibited the phosphorylation of p65 subunit of NFkappaB in MDA MB-231 cells. Furthermore, DHA and EPA reduced expression of Bcl-2 and Bcl-XL. NFkappaB DNA binding activity and NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes were also prevented by DHA and EPA treatment. Finally, we showed that PTEN expression significantly inhibited NFkappaB-dependent transcription of Bcl-2 and Bcl-XL genes. Taken together, our data reveals a novel signaling pathway linking the fish oil diet to increased PTEN expression that attenuates the growth promoting signals and augments the apoptotic signals, resulting in breast tumor regression.

Involvement of PPARα in the growth inhibitory effect of arachidonic acid on breast cancer cells

Epidemiological studies suggest that dietary PUFA may influence breast cancer progression.n-3 PUFA are generally known to exert antitumour effects, whereas reports relative ton-6 PUFA anti-carcinogen effects are controversial. Arachidonic acid (AA; 20 : 4n − 6) and its metabolites have been shown to inhibit the growth of human breast cancer cell lines, even if the downstream mechanisms by which AA may influence carcinogenesis remain unresolved. We explored the molecular basis for AA influence on proliferation, signal transduction and apoptosis in two human breast cancer cell lines, MCF-7 and MDA-MB-231. In both cell lines AA inhibited cell growth in a dose-dependent manner, even if MDA-MB-231 was somewhat more growth-inhibited than MCF-7. AA decreased extracellular signal-regulated protein kinase 1/2 phosphorylation level, and positively modulated PPARγ and PPARα expression, with only a slight effect against PPARβ/δ. In addition, AA increased Bak (an apoptosis-regulating protein) expression and reduced procaspase-3 and -9 levels only in MDA-MB-231 cells, thus indicating that the growth inhibitory effect can be correlated with apoptosis induction. In both cell lines the use of a specific antagonist made it possible to establish a relationship between AA growth inhibitory effect and PPARα involvement. AA decreases cell proliferation most likely by inducing apoptosis in MDA-MB-231 cells, while in the MCF-7 cell line the growth inhibitory activity can be attributed to the inhibition of the signal transduction pathway involved in cell proliferation. In both cases, the results here presented suggest PPARα as a possible contributor to the growth inhibitory effect of AA.

An endogenous regulator of inflammation, resolvin E1, modulates osteoclast differentiation and bone resorption

BACKGROUND AND PURPOSE

The inflammation-resolving lipid mediator resolvin E1 (RvE1) effectively stops inflammation-induced bone loss in vivo in experimental periodontitis. It was of interest to determine whether RvE1 has direct actions on osteoclast (OC) development and bone resorption.

EXPERIMENTAL APPROACH

Primary OC cultures derived from mouse bone marrow were treated with RvE1 and analysed for OC differentiation, cell survival and bone substrate resorption. Receptor binding was measured using radiolabelled RvE1. Nuclear factor (NF)-kappaB activation and Akt phosphorylation were determined with western blotting. Lipid mediator production was assessed with liquid chromatography tandem mass spectrometry.

KEY RESULTS

OC growth and resorption pit formation were markedly decreased in the presence of RvE1. OC differentiation was inhibited by RvE1 as demonstrated by decreased number of multinuclear OC, a delay in the time course of OC development and attenuation of receptor activator of NF-kappaB ligand-induced nuclear translocation of the p50 subunit of NF-kappaB. OC survival and apoptosis were not altered by RvE1. Messenger RNA for both receptors of RvE1, ChemR23 and BLT(1) is expressed in OC cultures. Leukotriene B(4) (LTB(4)) competed with [(3)H]RvE1 binding on OC cell membrane preparations, and the LTB(4) antagonist U75302 prevented RvE1 inhibition of OC growth, indicating that BLT(1) mediates RvE1 actions on OC. Primary OC synthesized the RvE1 precursor 18R-hydroxy-eicosapentaenoic acid and LTB(4). Co-incubation of OC with peripheral blood neutrophils resulted in transcellular RvE1 biosynthesis.

CONCLUSIONS AND IMPLICATIONS

These results indicate that RvE1 inhibits OC growth and bone resorption by interfering with OC differentiation. The bone-sparing actions of RvE1 are in addition to inflammation resolution, a direct action in bone remodelling.

Reduced growth and integrin expression of prostate cells cultured with lycopene, vitamin E and fish oil in vitro

Integrins are transmembrane proteins that facilitate the interaction of cells with the extracellular environment. They have also been implicated in cancer progression. The effects of nutrients thought to be involved in the prevention of prostate cancer on integrin expression have not been determined. Prostate cancer cell lines representing a range of malignancy from normal (RWPE-1) to highly invasive phenotypes (22Rv1 < LNCaP < PC-3) were cultured with or without lycopene (10 nm), vitamin E (5 μm) or fish oil (100 μm) for 48 h. Growth and integrin (α2β1, αvβ3 and αvβ5) expression were assessed using Trypan Blue exclusion and monoclonal antibodies combined with flow cytometry. Vitamin E enhanced (P < 0·001) whereas fish oil reduced the growth of all the cell lines tested (P < 0·001). Lycopene had no effect on growth. All the malignant cell lines exhibited lower expression of α2β1 with the addition of lycopene to culture media. Supplemental fish oil reduced α2β1 in most invasive cell lines (LNCaP and PC-3). Each nutrient at physiological levels reduced integrins αvβ3 and αvβ5 in most invasive cell lines (PC-3). The results suggest that integrins may represent an additional target of bioactive nutrients and that the effects of nutrients may be dependent on the type of cell line used.

The potential for treatment with dietary long-chain polyunsaturated n-3 fatty acids during chemotherapy

Dietary intake of long-chain omega-3 (or n-3) polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) can affect numerous processes in the body, including cardiovascular, neurological and immune functions, as well as cancer. Studies on human cancer cell lines, animal models and preliminary trials with human subjects suggest that administration of EPA and DHA, found naturally in our diet in fatty fish, can alter toxicities and/or activity of many drugs used to treat cancer. Multiple mechanisms are proposed to explain how n-3 PUFA modulate the tumor cell response to chemotherapeutic drugs. n-3 PUFA are readily incorporated into cell membranes and lipid rafts, and their incorporation may affect membrane-associated signaling proteins such as Ras, Akt and Her-2/neu. Due to their high susceptibility to oxidation, it has also been proposed that n-3 PUFA may cause irreversible tumor cell damage through increased lipid peroxidation. n-3 PUFA may increase tumor cell susceptibility to apoptosis by altering expression or function of apoptotic proteins, or by modulating activity of survival-related transcription factors such as nuclear factor-kappaB. Some studies suggest n-3 PUFA may increase drug uptake or even enhance drug activation (e.g., in the case of some nucleoside analogue drugs). Further research is warranted to identify specific mechanisms by which n-3 PUFA increase chemotherapy efficacy and to determine the optimal cellular/membrane levels of n-3 PUFA required to promote these mechanisms, such that these fatty acids may be prescribed as adjuvants to chemotherapy.

Inhibition of tumorigenesis in ApcMin/+ mice by a combination of (-)-epigallocatechin-3-gallate and fish oil

The effect of a combination of (-)-epigallocatechin-3-gallate (EGCG) with fish oil on intestinal tumorigenesis in Apc (Min/+) mice fed a high-fat diet was investigated in the present study. The combined treatment of EGCG and fish oil for 9 weeks reduced the tumor number by 53% as compared to controls while neither agent alone had a significant effect. Apoptosis was significantly increased in all treatment groups. beta-Catenin nuclear positivity in adenomas from the combination group was lower than control mice, implicating the modulation of Wnt signaling by the combination. Fish oil and the combination significantly reduced prostaglandin E 2 (PGE 2) levels in small intestinal tumors as compared to controls, suggesting modulation of aberrant arachidonic acid metabolism by fish oil. Akt phosphorylation in adenomas was significantly reduced in all treatment groups, which may have contributed to the observed increase in apoptosis. The results indicate that a combination of low doses of EGCG and fish oil can inhibit tumor multiplicity in Apc (Min/+) mice.

Dietary canola oil suppressed growth of implanted MDA-MB 231 human breast tumors in nude mice

Long chain omega 3 (n-3) fatty acids, eicosapentaenoic (EPA) and/or docosahexaenoic acid (DHA), have been shown to suppress growth of most cancer cells. In vivo, alpha linolenic acid (ALA, 18:3n-3) can be converted to EPA or DHA. We hypothesized that substituting canola oil (10% ALA) for the corn oil (1% ALA) in the diet of cancer bearing mice would slow tumor growth by increasing n-3 fatty acids in the diet. Sixty nude mice received MDA-MB 231 human breast cancer cells and were fed a diet containing 8% w/w corn oil until the mean tumor volume was 60 mm3. The dietary fat of half of the tumor bearing mice was then changed to 8% w/w canola oil. Compared to mice that consumed the corn oil containing diet, the mice that consumed the canola oil containing diet had significantly more EPA and DHA in both tumors and livers, and the mean tumor growth rate and cell proliferation in the tumor were significantly slower (P<0.05). About 25 days after diet change, mice that consumed the corn oil diet stopped gaining weight, whereas the mice that consumed the canola oil diet continued normal weight gain. Use of canola oil instead of corn oil in the diet may be a reasonable means to increase consumption of n-3 fatty acids with potential significance for slowing growth of residual cancer cells in cancer survivors.

Effect of Chia oil (Salvia Hispanica) rich in omega-3 fatty acids on the eicosanoid release, apoptosis and T-lymphocyte tumor infiltration in a murine mammary gland adenocarcinoma

We investigated the effects of certain dietary polyunsaturated fatty acids (PUFAs) and related eicosanoids on the growth and metastasis formation of a murine mammary gland adenocarcinoma. Salvia hispanica (ChO) and Carthamus tinctorius (SaO) vegetable oil sources of omega-3 and -6 PUFAs and a commercial diet as control (CO), were used. We analysed fatty acids of neoplastic cells (NC) membranes by GLC; the eicosanoids 12- HETE and 12-HHT (LOX and COX metabolites) by HPLC and apoptosis and T-lymphocyte infiltration by flow cytometry and microscopy. NC from ChO groups showed lower levels of arachidonic acid and of both eicosanoids compared to SaO and CO (p<0.05). The ChO diet decreased the tumor weight and metastasis number (p<0.05). Apoptosis and T-lymphocyte infiltration were higher and mitosis decreased with respect to the other diets (p<0.05). Present data showed that ChO, an ancient and almost unknown source of omega-3, inhibits growth and metastasis in this tumor model.

(n-3) PUFA alter raft lipid composition and decrease epidermal growth factor receptor levels in lipid rafts of human breast cancer cells

To determine the mechanism by which the (n-3) fatty acids (FA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) decrease proliferation and induce apoptosis in MDA-MB-231 human breast cancer cells, we examined the effects of EPA and DHA on the lipid composition of lipid rafts as well as epidermal growth factor receptor (EGFR) raft localization and phosphorylation. (n-3) FA (a combination of EPA and DHA) inhibited (P < 0.05) the growth of MDA-MB-231 cells by 48-62% in the presence and absence, respectively, of linoleic acid (LA). More EPA and DHA were incorporated into lipid rafts isolated from MDA-MB-231 cells after treatment with (n-3) FA compared with cells treated with LA (P < 0.05). EPA and DHA treatment decreased (P < 0.05) lipid raft sphingomyelin, cholesterol, and diacylglycerol content and, in the absence of LA, EPA and DHA increased (P < 0.05) raft ceramide levels. Furthermore, there was a marked decrease in EGFR levels in lipid rafts, accompanied by increases in the phosphorylation of both EGFR and p38 mitogen-activated protein kinase (MAPK), in EPA+DHA-treated cells (P < 0.05). As sustained activation of the EGFR and p38 MAPK has been associated with apoptosis in human breast cancer cells, our results indicate that (n-3) FA modify the lipid composition of membrane rafts and alter EGFR signaling in a way that decreases the growth of breast tumors.

Dietary n-3 PUFA deprivation alters expression of enzymes of the arachidonic and docosahexaenoic acid cascades in rat frontal cortex

The enzymes that regulate the brain arachidonic acid (AA) cascade have been implicated in bipolar disorder and neuroinflammation. Fifteen weeks of dietary n-3 polyunsaturated fatty acid (PUFA) deprivation in rats decreases the concentration of docosahexaenoic acid (DHA) and increases its half-life within the brain. Based on this, we hypothesized that such dietary deprivation would decrease expression of enzymes responsible for the metabolic loss of DHA while increasing expression of those responsible for the metabolism of AA. Fifteen weeks of n-3 PUFA deprivation significantly decreased the activity, protein and mRNA expression of the DHA regulatory phospholipase A2 (PLA2), calcium-independent iPLA2, in rat frontal cortex. In contrast the activities, protein and mRNA levels of the AA selective calcium-dependent cytosolic phospholipase (cPLA2) and secretory sPLA2 were increased. Cyclooxygenase (COX)-1 protein but not mRNA was decreased in the n-3 PUFA-deprived rats whereas COX-2 protein and mRNA were increased. This study suggests that n-3 PUFA deprivation increases the half-live of brain DHA by downregulating iPLA2. The finding that n-3 PUFA deprivation increases cPLA2, sPLA2 and COX-2 is opposite to what has been reported after chronic administration of anti-manic agents to rats and suggests that n-3 PUFA deprivation may increase susceptibility to bipolar disorder.

Cell proliferation inhibition and alterations in retinol esterification induced by phytanic acid and docosahexaenoic acid

We investigated the effects of two natural dietary retinoid X receptor (RXR) ligands, phytanic acid (PA) and docosahexaenoic acid (DHA), on proliferation and on the metabolism of retinol (vitamin A) in both cultured normal human prostate epithelial cells (PrECs) and PC-3 prostate carcinoma cells. PA and DHA inhibited the proliferation of the parental PC-3 cells and PC-3 cells engineered to overexpress human lecithin:retinol acyltransferase (LRAT) in both the absence and presence of retinol. A synthetic RXR-specific ligand also inhibited PC-3 cell proliferation, whereas all-trans retinoic acid (ATRA) did not. PA and DHA treatment increased the levels of retinyl esters (REs) in both PrECs and PC-3 cells and generated novel REs that eluted on reverse-phase HPLC at 54.0 and 50.5 min, respectively. Mass spectrometric analyses demonstrated that these novel REs were retinyl phytanate (54.0 min) and retinyl docosahexaenoate (50.5 min). Neither PA nor DHA increased LRAT mRNA levels in these cells. In addition, we demonstrate that retinyl phytanate was generated by LRAT in the presence of PA and retinol; however, retinyl docosahexaenoate was produced by another enzyme in the presence of DHA and retinol.

Targeted quantitative analysis of fatty acids in atherosclerotic plaques by high sensitivity liquid chromatography/tandem mass spectrometry

The quantitative analysis of fatty acid composition in atherosclerotic plaques provides a way to monitor the underlying etiology of atherosclerosis. Previously, the method of choice for analyzing fatty acids in biological samples was gas chromatography/mass spectrometry (GC/MS); however, recent developments in electrospray ionization (ESI)/liquid chromatography (LC)/tandem mass spectrometry have made it a superior alternative. Previous research has largely focused on global analyses of intact lipids rather than more targeted analysis of the fatty acids themselves. We have now developed a targeted, stable isotope dilution LC-electrospray ionization/multiple reaction monitoring/MS method for the quantitative analysis of 10 fatty acids (myristic, palmitic, stearic, oleic, linoleic, alpha-linolenic, gamma-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids) using their trimethylaminoethyl ester (TMAE) derivatives to improve sensitivity. The method was validated, had a detection limit in the fmol range, and was used in the analysis of fatty acids in atherosclerotic plaques from carotid arteries.

Neuro-bioenergetic concepts in cancer prevention and treatment

Cancer remains one of the most difficult and elusive disorders to prevent and treat, despite great efforts in research and treatment over the last 30 years. Researchers have tried to understand the pathogenesis of cancer by discovering the single cellular mechanism or pathway derived from a genetic mutation. There are limited efforts made toward discovering a unified concept of cancer. We propose a neuro-bioenergetic concept of cancer pathogenesis based on the central mechanism of cellular hyperexcitability via inducible overexpression of voltage-gated ion channels, ligand-gated channels and neurotransmitters. Exploration of this concept could lead to a better understanding of the cause of cancer as well as developing more effective and specific strategies toward cancer prevention and treatment.

Essential fatty acids: biochemistry, physiology and pathology

Essential fatty acids (EFAs), linoleic acid (LA), and alpha-linolenic acid (ALA) are essential for humans, and are freely available in the diet. Hence, EFA deficiency is extremely rare in humans. To derive the full benefits of EFAs, they need to be metabolized to their respective long-chain metabolites, i.e., dihomo-gamma-linolenic acid (DGLA), and arachidonic acid (AA) from LA; and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from ALA. Some of these long-chain metabolites not only form precursors to respective prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), but also give rise to lipoxins (LXs) and resolvins that have potent anti-inflammatory actions. Furthermore, EFAs and their metabolites may function as endogenous angiotensin-converting enzyme and 3-hdroxy-3-methylglutaryl coenzyme A reductase inhibitors, nitric oxide (NO) enhancers, anti-hypertensives, and anti-atherosclerotic molecules. Recent studies revealed that EFAs react with NO to yield respective nitroalkene derivatives that exert cell-signaling actions via ligation and activation of peroxisome proliferator-activated receptors. The metabolism of EFAs is altered in several diseases such as obesity, hypertension, diabetes mellitus, coronary heart disease, schizophrenia, Alzheimer's disease, atherosclerosis, and cancer. Thus, EFAs and their derivatives have varied biological actions and seem to be involved in several physiological and pathological processes.

Clioquinol and docosahexaenoic acid act synergistically to kill tumor cells

Clioquinol, an 8-hydroxyquinoline derivative (5-chloro-7-iodo-8-hydroxyquinoline) with antimicrobial properties, has recently been found to have cytotoxic activity towards human cancer cell lines at concentrations achieved by oral administration. This study was initiated to determine whether clioquinol could potentiate the antitumor effects of two drugs, doxorubicin and docosahexaenoic acid (DHA), believed to act in part via the generation of reactant oxidant species. At low micromolar concentrations, clioquinol had little effect upon cell viability and did not potentiate doxorubicin's cytotoxicity. Clioquinol significantly enhanced DHA's cytotoxic effects, an interaction that was shown to be synergistic by isobolographic analysis. Clioquinol exhibited a synergistic interaction with DHA in reducing nuclear factor-kappaB activity and inducing apoptosis, and the combination reduced the level of several molecules that promote cell survival, including Akt, p65, and Bcl-2. Interestingly, clioquinol neither induced lipid peroxidation itself nor increased peroxidation brought about by the addition of DHA. However, when cells were pretreated with antioxidant vitamin E, the synergism of clioquinol and DHA was blocked, indicating the essential role of lipid peroxidation for their action. These findings reveal a novel antitumor drug combination that synergistically targets major cell survival signaling pathways.

Impact of different saturated fatty acid, polyunsaturated fatty acid and cholesterol containing diets on beta-amyloid accumulation in APP/PS1 transgenic mice

The present study assessed the influence of dietary lipids on accumulation of amyloid beta-peptide (Abeta) in the brain. Seven experimental diets with varying n-6/n-3-ratio, saturated and polyunsaturated fatty acid and cholesterol contents were fed to transgenic APPswe/PS1dE9 mice for 3-4 months beginning at a young adult age (6 months). Hippocampal Abeta levels were determined with ELISA and plaque load by using immunocytochemistry. A typical Western diet with 40% saturated fatty acids and 1% of cholesterol increased, while diets supplemented with docosahexaenoic acid (DHA) decreased Abeta levels compared to regular (soy oil based) diet. DHA diet also decreased the number of activated microglia in hippocampus and increased exploratory activity of transgenic mice, but did not improve their spatial learning in the water maze. The favorable effect of DHA on Abeta production was verified in two different cell lines. Regulation of dietary lipid intake may offer a new tool to reduce the risk of Alzheimer's disease at the population level.

Mechanisms involved in Jurkat cell death induced by oleic and linoleic acids

BACKGROUND & AIMS

Previous study from our laboratory showed the toxicity of oleic (OA) and linoleic acids (LA) on Jurkat and Raji cells and human lymphocytes in vitro. The mechanisms involved in the toxicity induced by OA and LA on Jurkat cells were determined in vitro.

METHODS

Jurkat cells were treated in the presence of OA and LA (25, 50, 100 and 200muM). The parameters investigated were: triglycerides and cholesterol ester concentrations determined by enzymatic assay, activation of peroxisome proliferator activated receptor (PPAR) by electrophoretic mobility shift assay, caspase 3, 6 and 8 activities by spectrofluorometric assay, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma production by enzyme linked absorbent assay (ELISA), expression of pro- (Bax) and anti- (Bcl-2) apoptotic genes by real time polymerase chain reaction and expression of pleiotropic genes by macroarray technique

RESULTS

Evidence is presented herein that the increase in triglycerides concentrations induced by OA is more pronounced than that caused by LA in Jurkat cells. Importantly, triglycerides accumulation may be a mechanism to protect lymphocytes against the toxicity induced by fatty acids. Both fatty acids raised PPAR activation, caspase 3 and 6 activities and TNF-alpha production. LA in toxic concentrations modulated the expression of genes related to cell cycle, apoptosis, proliferation, oxidative stress, and cytokine receptors.

CONCLUSION

The findings reported herein support the cell death induced by OA and LA involved triglycerides accumulation, PPAR activation, caspase 3 and 6 activities and TNF-alpha production.

Docosahexaenoic acid inhibits cancer cell growth via p27Kip1, CDK2, ERK1/ERK2, and retinoblastoma phosphorylation

Docosahexaenoic acid (DHA), a PUFA of the n-3 family, inhibited the growth of FM3A mouse mammary cancer cells by arresting their progression from the late-G(1) to the S phase of the cell cycle. DHA upregulated p27(Kip1) levels by inhibiting phosphorylation of mitogen-activated protein (MAP) kinases, i.e., ERK1/ERK2. Indeed, inhibition of ERK1/ERK2 phosphorylation by DHA, U0126 [chemical MAPK extracellularly signal-regulated kinase kinase (MEK) inhibitor], and MEK(SA) (cells expressing dominant negative constructs of MEK) resulted in the accumulation of p27(Kip1). MAP kinase (MAPK) inhibition by DHA did not increase p27(Kip1) mRNA levels. Rather, this fatty acid stabilized p27(Kip1) contents and inhibited MAPK-dependent proteasomal degradation of this protein. DHA also diminished cyclin E phosphorylation, cyclin-dependent kinase-2 (CDK2) activity, and phosphorylation of retinoblastoma protein in these cells. Our study shows that DHA arrests cell growth by modulating the phosphorylation of cell cycle-related proteins.

Differential effects of omega-3 and omega-6 Fatty acids on gene expression in breast cancer cells

Essential fatty acids have long been identified as possible oncogenic factors. Existing reports suggest omega-6 (omega-6) essential fatty acids (EFA) as pro-oncogenic and omega-3 (omega-3) EFA as anti-oncogenic factors. The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), inhibit the growth of human breast cancer cells while the omega-6 fatty acids induces growth of these cells in animal models and cell lines. In order to explore likely mechanisms for the modulation of breast cancer cell growth by omega-3 and omega-6 fatty acids, we examined the effects of arachidonic acid (AA), linoleic acid (LA), EPA and DHA on human breast cancer cell lines using cDNA microarrays and quantitative polymerase chain reaction. MDA-MB-231, MDA-MB-435s, MCF-7 and HCC2218 cell lines were treated with the selected fatty acids for 6 and 24 h. Microarray analysis of gene expression profiles in the breast cancer cells treated with both classes of fatty acids discerned essential differences among the two classes at the earlier time point. The differential effects of omega-3 and omega-6 fatty acids on the breast cancer cells were lessened at the late time point. Data mining and statistical analyses identified genes that were differentially expressed between breast cancer cells treated with omega-3 and omega-6 fatty acids. Ontological investigations have associated those genes to a broad spectrum of biological functions, including cellular nutrition, cell division, cell proliferation, metastasis and transcription factors etc., and thus presented an important pool of biomarkers for the differential effect of omega-3 and omega-6EFAs.

Eicosapentaenoic acid prevents endothelin-1-induced cardiomyocyte hypertrophy in vitro through the suppression of TGF-beta 1 and phosphorylated JNK

The cardiovascular benefit of fish oil in humans and experimental animals has been reported. Endothelin (ET)-1 is a well-known cardiac hypertrophic factor. However, although many studies link a fish oil extract, eicosapentaenoic acid (EPA), to cardiac protection, the effects of EPA on cardiac hypertrophy and underlying mechanism(s) are unclear. The present study investigated whether EPA prevents ET-1-induced cardiomyocyte hypertrophy; the potential pathways likely to underlie such an effect were also investigated. Cardiomyocytes were isolated from neonatal rat heart, cultured for 3 days, and then treated for 24 h with vehicle only (control), treated with 0.1 nM ET-1 only, or pretreated with 10 microM EPA and then treated with 0.1 nM ET-1. The cells were harvested, and changes in cell surface area, protein synthesis, expression of a cytoskeletal (alpha-actinin) protein, and cell signaling were analyzed. ET-1 induced a 97% increase in cardiomyocyte surface area, a 72% increase in protein synthesis rate, and an increase in expression of alpha-actinin and signaling molecule [transforming growth factor-beta 1 (TGF-beta 1), c-Jun NH2-terminal kinase (JNK), and c-Jun]. Development of these ET-1-induced cellular changes was attenuated by EPA. Moreover, the hypertrophied cardiomyocytes showed a 1.5- and a 1.7-fold increase in mRNA expression of atrial and brain natriuretic peptides, the classical molecular markers of cardiac hypertrophy, respectively; these changes were also suppressed by EPA. Here we show that ET-1 induces cardiomyocyte hypertrophy and expression of hypertrophic markers, possibly mediated by JNK and TGF-beta 1 signaling pathways. These ET-1-induced effects were blocked by EPA, a major fish oil ingredient, suggesting that fish oil may have beneficial protective effects on cardiac hypertrophy.

Docosahexaenoic acid (omega−3) blocks voltage-gated sodium channel activity and migration of MDA-MB-231 human breast cancer cells

Omega-3 polyunsaturated fatty acids have been suggested to play an important role in cancer prevention/progression, on the one hand, and in modulation of membrane ion channels on the other. We investigated whether docosahexaenoic acid would influence the in vitro migration of MDA-MB-231 human breast cancer cells. An important follow-up question was whether any effect would involve voltage-gated Na(+) channels, shown previously to occur in human breast cancer in vitro and in vivo and to correlate with metastatic potential. Short-term (acute) and long-term (24-72 h) application of docosahexaenoic acid suppressed the activity of the channel activity in a dose-dependent manner. At the working concentrations of docosahexaenoic acid used (0.05-0.5 microM), there was no effect on proliferation. Long-term treatment with docosahexaenoic acid down-regulated mRNA and protein (total and plasma membrane) levels of neonatal Nav1.5 voltage-gated Na(+) channel, known to be predominant in these cells. Docosahexaenoic acid suppressed migration of the MDA-MB-231 cells to the same extent as tetrodotoxin, a highly specific blocker of voltage-gated Na(+) channels, but the two effects were not additive. It was concluded that the docosahexaenoic acid-induced suppression of cellular migration occurred primarily via down-regulation of voltage-gated Na(+) channel (neonatal Nav1.5) mRNA and functional protein expression.

Selective polyunsaturated fatty acids enrichment in phospholipids from neuronal-derived cell lines

Most studies aimed at exploring the molecular and cellular properties of plasma membranes in neural tissues make use of cell lines. However, cell membrane lipid composition of cell lines is notably different from that of brain tissues where they presumably derive from. Using septal-derived SN56 cells and hippocampal-derived HT22 cells, we demonstrated that cell lines exhibit lower contents of saturated (18:0) and long polyunsaturated fatty acids (PUFA; 20:4n-6 and especially 22:6n-3), as well as higher monounsaturated fatty acid contents (mainly 18:1n-9), compared to mouse brain. Also, cell lines exhibited higher contents of sterol esters and lower contents of cholesterol and phospholipids, especially phosphatidylethanolamine and phosphatidylserine. We have also evaluated the effects of different (n-3/n-6) PUFA enrichments on fatty acid and phospholipid contents in these cell lines. Our results show that enrichment of culture medium with 22:6n-3 and 20:4n-6 in a 70/30 proportion during 48 h, using fat-free bovine serum albumin as vehicle, successfully readjusted fatty acid profiles in cell line-polar lipids to values found in natural nerve cells. Interestingly, no differences in cell survival were observed upon enrichment. The generalization of these methodologies would allow a more feasible adaptation of cellular models to the study of in vivo nerve physiology.