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

Crystallization and melting properties of mixtures of milk fat stearin and omega-3 rich oils

Solid milk fat stearin (S₂₅) can be a promising oxidation retarder due to its capacity to entrap liquid oils, especially for incorporating omega-3 (ω-3) rich oils into dairy products. Thermal properties of S₂₅/ω-3 rich oil mixtures are necessary for such application. The effects of S₂₅ on the crystallization and melting behaviours of ω-3 rich oils, namely fish oil (FO), linseed oil (LO) and krill oil (KO), were investigated by differential scanning calorimetry (DSC). Thermograms showed that with S₂₅ concentration increasing, transitions of FO and LO shifted to lower and largely to higher temperatures, respectively, while crystallization temperature of KO slightly decreased. Negative, positive and low values of interaction enthalpy (ΔH_int) suggested the adverse, beneficial and limited effect of S₂₅ on the crystallization of S₂₅/FO, S₂₅/LO and S₂₅/KO mixtures, respectively. LO could have the best oxidative stability upon the addition of S₂₅ since their interactions facilitated earlier and stronger crystallization.

Docosahexaenoic acid-acylated phloridzin, a novel polyphenol fatty acid ester derivative, is cytotoxic to breast cancer cells

Docosahexaenoic acid-acylated phloridzin (PZ-DHA), a novel polyphenol fatty acid ester derivative, was synthesized through a regioselective acylation reaction with the aim of increasing the bioactivity of phloridzin (PZ) and docosahexaenoic acid (DHA). In this study, PZ-DHA's cytotoxic activity was explored using in vitro and in vivo models of mammary carcinoma. PZ-DHA was selectively cytotoxic for mammary carcinoma (MDA-MB-231, MDA-MB-468, 4T1, MCF-7 and T-47D) cells compared to non-malignant human mammary epithelial cells (HMEC and MCF-10A) and fibroblasts by MTS assay and Annexin-V-FLUOS/propidium iodide staining. Flow cytometric analysis of Oregon Green 488- and Ki-67-stained MDA-MB-231 cells showed antiproliferative activity of PZ-DHA at a subcytotoxic concentration. PZ-DHA also arrested MDA-MB-231 cell division at the G2/M phase and down-regulated expression of cyclin B1 and cyclin-dependent kinase 1 (CDK1). PZ-DHA-induced apoptosis in MDA-MB-231 cells was confirmed by caspase 3/7 activation in a luminescence assay and DNA fragmentation by TUNEL staining. Moreover, MDA-MB-231 xenograft growth in non-obese diabetic severe combined immunodeficient mice was suppressed by intra-tumoral administration of PZ-DHA. This study shows that PZ-DHA is selectively cytotoxic to breast cancer cells in vitro and in vivo, suggesting that further investigations of PZ-DHA are warranted as a potential treatment for breast cancer.

Omega-3 polyunsaturated fatty acids and cancer: lessons learned from clinical trials

Over the past decades, extensive studies have addressed the therapeutic effects of omega-3 polyunsaturated fatty acids (omega-3 FAs) against different human diseases such as cardiovascular and neurodegenerative diseases, cancer, etc. A growing body of scientific research shows the pharmacokinetic information and safety of these natural occurring substances. Moreover, during recent years, a plethora of studies has demonstrated that omega-3 FAs possess therapeutic role against certain types of cancer. It is also known that omega-3 FAs can improve efficacy and tolerability of chemotherapy. Previous reports showed that suppression of nuclear factor-κB, activation of AMPK/SIRT1, modulation of cyclooxygenase (COX) activity, and up-regulation of novel anti-inflammatory lipid mediators such as protectins, maresins, and resolvins, are the main mechanisms of antineoplastic effect of omega-3 FAs. In this review, we have collected the available clinical data on the therapeutic role of omega-3 FAs against breast cancer, colorectal cancer, leukemia, gastric cancer, pancreatic cancer, esophageal cancer, prostate cancer, lung cancer, head and neck cancer, as well as cancer cachexia. We also discussed the chemistry, dietary source, and bioavailability of omega-3 FAs, and the potential molecular mechanisms of anticancer and adverse effects.

Docosahexaenoic Acid Induces Growth Suppression on Epithelial Ovarian Cancer Cells More Effectively than Eicosapentaenoic Acid

Omega-3 fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to possess definitively suppressive effects on the growth of epithelial ovarian cancer cells. This study investigated the differential effects of pure EPA and DHA on the growth of epithelial ovarian cancer cells and the potential molecular mechanisms that may be involved. There were significant time- and dose-dependent inhibitory effects of both EPA and DHA on cellular proliferation of the epithelial ovarian cancer cell line TOV-21G (P < 0.05). TOV-21G cells pretreated with peroxisome proliferator receptor activator gamma (PPARγ) antagonist, GW9662, markedly suppressed EPA/DHA-induced apoptosis as determined by TUNEL assay, Annexin V-FITC/PI staining, and caspase-3 activity. EPA/DHA significantly induced PPARγ and p53 overexpression as observed in immunoblotting assay and the induction of p53 by EPA/DHA was abolished by GW9662. In all cases, the effect of DHA was significantly more potent than that of EPA (P < 0.05). Our findings suggested that DHA may be more effective than EPA in growth suppression of TOV-21G cells and the biologic effects may be partly mediated by PPARγ and p53 activation. Further research is required to elucidate additional divergent mechanisms to account for apparent differences between EPA and DHA.

Eicosopentaneoic Acid and Other Free Fatty Acid Receptor Agonists Inhibit Lysophosphatidic Acid- and Epidermal Growth Factor-Induced Proliferation of Human Breast Cancer Cells

Many key actions of ω-3 (n-3) fatty acids have recently been shown to be mediated by two G protein-coupled receptors (GPCRs) in the free fatty acid receptor (FFAR) family, FFA1 (GPR40) and FFA4 (GPR120). n-3 Fatty acids inhibit proliferation of human breast cancer cells in culture and in animals. In the current study, the roles of FFA1 and FFA4 were investigated. In addition, the role of cross-talk between GPCRs activated by lysophosphatidic acid (LPA), and the tyrosine kinase receptor activated by epidermal growth factor (EGF), was examined. In MCF-7 and MDA-MB-231 human breast cancer cell lines, both LPA and EGF stimulated proliferation, Erk activation, Akt activation, and CCN1 induction. LPA antagonists blocked effects of LPA and EGF on proliferation in MCF-7 and MDA-MB-231, and on cell migration in MCF-7. The n-3 fatty acid eicosopentaneoic acid inhibited LPA- and EGF-induced proliferation in both cell lines. Two synthetic FFAR agonists, GW9508 and TUG-891, likewise inhibited LPA- and EGF-induced proliferation. The data suggest a major role for FFA1, which was expressed by both cell lines. The results indicate that n-3 fatty acids inhibit breast cancer cell proliferation via FFARs, and suggest a mechanism involving negative cross-talk between FFARS, LPA receptors, and EGF receptor.

Omega-3 Fatty Acids and Cancer Cell Cytotoxicity: Implications for Multi-Targeted Cancer Therapy

Cancer is a major disease worldwide. Despite progress in cancer therapy, conventional cytotoxic therapies lead to unsatisfactory long-term survival, mainly related to development of drug resistance by tumor cells and toxicity towards normal cells. n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), can exert anti-neoplastic activity by inducing apoptotic cell death in human cancer cells either alone or in combination with conventional therapies. Indeed, n-3 PUFAs potentially increase the sensitivity of tumor cells to conventional therapies, possibly improving their efficacy especially against cancers resistant to treatment. Moreover, in contrast to traditional therapies, n-3 PUFAs appear to cause selective cytotoxicity towards cancer cells with little or no toxicity on normal cells. This review focuses on studies investigating the cytotoxic activity of n-3 PUFAs against cancer cells via apoptosis, analyzing the molecular mechanisms underlying this effective and selective activity. Here, we highlight the multiple molecules potentially targeted by n-3 PUFAs to trigger cancer cell apoptosis. This analysis can allow a better comprehension of the potential cytotoxic therapeutic role of n-3 PUFAs against cancer, providing specific information and support to design future pre-clinical and clinical studies for a better use of n-3 PUFAs in cancer therapy, mainly combinational therapy.

Effect of Docosahexaenoic Acid (DHA) on Breast Cancer Cells

Today, many materials as drug are developed having various prominent function in order to treatment of disease or cancer. Among these materials, especially docosahexaenoic acid (DHA), main constituents of omega-3 fatty acid, has a lot of beneficial and natural effects, so it has been known as anticancer material especially breast cancer. Breast cancer is disease taking high occurrence level among feminine diseases. DHA has anticancer effects on breast cancer cell, representatively inducing apoptosis, inhibiting proliferation or metastasis. Main effect of DHA on breast cancer cell is apoptosis inducing, which has mechanism that treated DHA causes lipid peroxidation increasing reactive oxygen species (ROS) level and it activates caspase 8 and caspase 9 so activated caspase occurs apoptosis. Cell lines of breast cancer are MDA-MB-231, MCF-7, SK-BR-3, T47D and ZR75. Especially this article uses the MCF-7 cell line at experiment of anti-proliferation by DHA, the MDA-MB-231 cell line at experiment of anti-metastasis by DHA, because that cell line has specialized metastasis activity. Therefore, this paper discusses the effects of natural material DHA as drug of breast cancer.

Effect of Docosahexaenoic Acid on Cell Cycle Pathways in Breast Cell Lines With Different Transformation Degree

n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), abundant in fish, have been shown to affect development and progression of some types of cancer, including breast cancer. The aim of our study was to further analyze and clarify the effects of these nutrients on the molecular mechanisms underlying breast cancer. Following treatments with DHA we examined cell viability, death, cell cycle, and some molecular effects in breast cell lines with different transformation, phenotypic, and biochemical characteristics (MCF-10A, MCF-7, SK-BR-3, ZR-75-1). These investigations showed that DHA is able to affect cell viability, proliferation, and cell cycle progression in a different way in each assayed breast cell line. The activation of ERK1/2 and STAT3 pathways and the expression and/or activation of molecules involved in cell cycle regulation such as p21(Waf1/Cip1) and p53, are very differently regulated by DHA treatments in each cell model. DHA selectively: (i) arrests non tumoral MCF-10A breast cells in G0 /G1 cycle phase, activating p21(Waf1/Cip1) , and p53, (ii) induces to death highly transformed breast cells SK-BR-3, reducing ERK1/2 and STAT3 phosphorylation and (iii) only slightly affects each analyzed process in MCF-7 breast cell line with transformation degree lower than SK-BR-3 cells. These findings suggest a more relevant inhibitory role of DHA within early development and late progression of breast cancer cell transformation and a variable effect in the other phases, depending on individual molecular properties and degree of malignancy of each clinical case.

Raman microspectroscopy of noncancerous and cancerous human breast tissues. Identification and phase transitions of linoleic and oleic acids by Raman low-temperature studies

We present the results of Raman studies in the temperature range of 293-77 K on vibrational properties of linoleic and oleic acids and Raman microspectroscopy of human breast tissues at room temperature. Our results confirmed the significant role of unsaturated fatty acids in differentiation of noncancerous and cancerous breast tissues and the role of vibrational spectroscopy in phase transition identification. We have found that vibrational properties are very sensitive indicators to specify phases and phase transitions typical of unsaturated fatty acids at the molecular level. Using Raman spectroscopy we have identified high-temperature, middle-temperature and low-temperature phases of linoleic acid. Results obtained for linoleic acid were compared with parameters characteristic of α and γ phases of oleic acid - the parent compound of polyunsaturated fatty acids.

α-linolenic acid and docosahexaenoic acid, alone and combined with trastuzumab, reduce HER2-overexpressing breast cancer cell growth but differentially regulate HER2 signaling pathways

BACKGROUND

Diets rich in the n-3 fatty acid alpha-linolenic acid (ALA) have been shown to reduce breast tumor growth, enhance the effectiveness of the HER2-targeted drug trastuzumab (TRAS) and reduce HER2 signaling in mouse models. It is unclear whether this is due to direct effects of ALA or due to its long-chain n-3 fatty acids metabolites including docosahexaenoic acid (DHA).

METHODS

The ability of HER2-overexpressing BT-474 human breast cancer cells to convert ALA to long-chain n-3 fatty acids was determined by measurement of phospholipid fatty acids by gas chromatography following treatment with 100 μM ALA. The effects of 96 h treatment with ALA or DHA, at serum levels seen in mice (50-100 μM), alone and combined with TRAS (10 μg/ml), on BT-474 cell growth measured by trypan blue exclusion, apoptosis measured by flow cytometric analysis of Annexin-V/7-AAD stained cells (ALA and TRAS treatment only) and protein biomarkers HER2 signaling measured by western blot were determined.

RESULTS

ALA-treated BT-474 cells had higher phospholipid ALA but no increase in downstream n-3 metabolites including DHA. Both ALA and DHA reduced cell growth with and without TRAS. ALA had no effect on apoptosis. ALA and DHA showed opposite effects on Akt and MAPK phosphorylation; ALA increased and DHA decreased phosphorylation.

CONCLUSIONS

Together these data suggest that, while both ALA and its DHA metabolite can reduce HER2-overexpressing breast cancer growth with and without TRAS, they demonstrate for the first time that DHA is responsible for the effects of ALA-rich diets on HER2 signaling pathways.

Omega-3 DHA- and EPA-dopamine conjugates induce PPARγ-dependent breast cancer cell death through autophagy and apoptosis

BACKGROUND

The omega-3 docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may form conjugates with amines that have potential health benefits against common diseases including cancers. Here we synthesized DHA-dopamine (DHADA) and EPA-dopamine (EPADA) conjugates and studied their biological effects on different breast cancer cell lines.

METHODS AND RESULTS

MTT assays indicated that increasing concentrations of DHADA and EPADA significantly affected viability in MCF-7, SKBR3 and MDA-MB-231 breast cancer cells, whereas no effect was observed in MCF-10A non-tumorigenic epithelial breast cells. DHADA and EPADA enhanced Beclin-1 expression, as evidenced by immunoblotting, real-time-PCR and functional analyses. Chromatin Immunoprecipitation (ChIP) and Re-ChIP assays revealed that both compounds induced recruitment of Peroxisome-Proliferator-Activated-Receptor gamma (PPARγ) and RNA Polymerase-II at the Retinoic-X-Receptor binding region on Beclin-1 promoter. Moreover, both compounds enhanced autophagosome formation, evaluated by LC-3 and monodansylcadaverine labeling, that was prevented by the PPARγ antagonist GW9662, addressing the direct involvement of PPARγ. Noteworthy, long-term treatment with DHADA and EPADA caused the blockade of autophagic flux followed by apoptotic cell death as evidenced by PARP cleavage and DNA fragmentation in all breast cancer cells.

CONCLUSIONS

We have provided new insights into the molecular mechanism through which PPARγ, as a central molecule in the cross talk between autophagy and apoptosis, mediates DHADA- and EPADA-induced cell death in breast cancer cells.

GENERAL SIGNIFICANCE

Our findings suggest that omega-3 DHADA- and EPADA activation of PPARγ may assume biological relevance in setting novel adjuvant therapeutic interventions in breast carcinoma.

Fish, n - 3 polyunsaturated fatty acids and n - 6 polyunsaturated fatty acids intake and breast cancer risk: The Japan Public Health Center-based prospective study

Limited and inconsistent studies exist on the association between the intake of fish, n - 3 polyunsaturated fatty acids (PUFA) and n - 6 PUFA and breast cancer. Fish and n - 3 PUFA support various body functions and are thought to reduce the carcinogenesis risk while n - 6 PUFA may have a positive association with cancer risk. We examined the association between intake of fish, n - 3 PUFA [including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA) and alpha-linolenic acid (ALA)] and n - 6 PUFA and breast cancer with subanalyses on estrogen (ER) and progesterone receptor (PR) status. We investigated 38,234 Japanese women aged 45-74 years from the Japan Public Health Center-based prospective study (JPHC study), and during 14.1 years of follow-up time, 556 breast cancer cases were newly diagnosed. Breast cancer risk was not associated with the intake of total fish, n - 3 PUFA and n - 6 PUFA when analyzed in totality through multivariable Cox proportional hazards regression models with age as the time scale. Intake of total n - 6 was positively associated with the development of ER+PR+ tumors [multivariable-adjusted HR Q4 vs. Q1  = 2.94 (95% CI: 1.26-6.89; ptrend  = 0.02)]. Intake of EPA was associated with a decreased breast cancer risk for ER+PR+ tumors [multivariable-adjusted HR Q2 vs. Q1  = 0.47 (95% CI: 0.25-0.89; ptrend =0.47)]. While the overall association between the intake of total fish, n - 3 PUFA and n - 6 PUFA and breast cancer risk is null, for ER+PR+ tumors, a positive association was seen between n - 6 intake and breast cancer, and a marginally significant inverse association was observed for EPA intake.

Exosome-mediated microRNA signaling from breast cancer cells is altered by the anti-angiogenesis agent docosahexaenoic acid (DHA)

BACKGROUND

Docosahexaenoic acid (DHA) is a natural compound with anticancer and anti-angiogenesis activity that is currently under investigation as both a preventative agent and an adjuvant to breast cancer therapy. However, the precise mechanisms of DHA's anticancer activities are unclear. It is understood that the intercommunication between cancer cells and their microenvironment is essential to tumor angiogenesis. Exosomes are extracellular vesicles that are important mediators of intercellular communication and play a role in promoting angiogenesis. However, very little is known about the contribution of breast cancer exosomes to tumor angiogenesis or whether exosomes can mediate DHA's anticancer action.

RESULTS

Exosomes were collected from MCF7 and MDA-MB-231 breast cancer cells after treatment with DHA. We observed an increase in exosome secretion and exosome microRNA contents from the DHA-treated cells. The expression of 83 microRNAs in the MCF7 exosomes was altered by DHA (>2-fold). The most abundant exosome microRNAs (let-7a, miR-23b, miR-27a/b, miR-21, let-7, and miR-320b) are known to have anti-cancer and/or anti-angiogenic activity. These microRNAs were also increased by DHA treatment in the exosomes from other breast cancer lines (MDA-MB-231, ZR751 and BT20), but not in exosomes from normal breast cells (MCF10A). When DHA-treated MCF7 cells were co-cultured with or their exosomes were directly applied to endothelial cell cultures, we observed an increase in the expression of these microRNAs in the endothelial cells. Furthermore, overexpression of miR-23b and miR-320b in endothelial cells decreased the expression of their pro-angiogenic target genes (PLAU, AMOTL1, NRP1 and ETS2) and significantly inhibited tube formation by endothelial cells, suggesting that the microRNAs transferred by exosomes mediate DHA's anti-angiogenic action. These effects could be reversed by knockdown of the Rab GTPase, Rab27A, which controls exosome release.

CONCLUSIONS

We conclude that DHA alters breast cancer exosome secretion and microRNA contents, which leads to the inhibition of angiogenesis. Our data demonstrate that breast cancer exosome signaling can be targeted to inhibit tumor angiogenesis and provide new insight into DHA's anticancer action, further supporting its use in cancer therapy.

The role of n-3 polyunsaturated fatty acids in the prevention and treatment of breast cancer

Breast cancer (BC) is the most common cancer among women worldwide. Dietary fatty acids, especially n-3 polyunsaturated fatty acids (PUFA), are believed to play a role in reducing BC risk. Evidence has shown that fish consumption or intake of long-chain n-3 PUFA, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are beneficial for inhibiting mammary carcinogenesis. The evidence regarding α-linolenic acid (ALA), however, remains equivocal. It is essential to clarify the relation between ALA and cancer since ALA is the principal source of n-3 PUFA in the Western diet and the conversion of ALA to EPA and DHA is not efficient in humans. In addition, the specific anticancer roles of individual n-3 PUFA, alone, have not yet been identified. Therefore, the present review evaluates ALA, EPA and DHA consumed individually as well as in n-3 PUFA mixtures. Also, their role in the prevention of BC and potential anticancer mechanisms of action are examined. Overall, this review suggests that each n-3 PUFA has promising anticancer effects and warrants further research.

Fatty acid esters of phloridzin induce apoptosis of human liver cancer cells through altered gene expression

Phloridzin (phlorizin or phloretin 2′-O-glucoside) is known for blocking intestinal glucose absorption. We have investigated the anticarcinogenic effect of phloridzin and its novel derivatives using human cancer cell lines. We have synthesised novel acylated derivatives of phloridzin with six different long chain fatty acids by regioselective enzymatic acylation using Candida Antarctica lipase B. The antiproliferative effects of the new compounds were investigated in comparison with the parent compounds, phloridzin, aglycone phloretin, the six free fatty acids and chemotherapeutic drugs (sorafenib, doxorubicin and daunorubicin) using human hepatocellular carcinoma HepG2 cells, human breast adenocarcinoma MDA-MB-231 cells and acute monocytic leukemia THP-1 cells along with normal human and rat hepatocytes. The fatty acid esters of phloridzin inhibited significantly the growth of the two carcinoma and leukemia cells while similar treatment doses were not toxic to normal human or rat hepatocytes. The antiproliferative potency of fatty esters of phloridzin was comparable to the potency of the chemotherapeutic drugs. The fatty acid esters of phloridzin inhibited DNA topoisomerases IIα activity that might induce G₀/G₁ phase arrest, induced apoptosis via activation of caspase-3, and decreased ATP level and mitochondrial membrane potential in HepG2 cells. Based on the high selectivity on cancer cells, decosahexaenoic acid (DHA) ester of phloridzin was selected for gene expression analysis using RT²PCR human cancer drug target array. Antiproliferative effect of DHA ester of phloridzin could be related to the down regulation of anti-apoptotic gene (BCL2), growth factor receptors (EBFR family, IGF1R/IGF2, PDGFR) and its downstream signalling partners (PI3k/AKT/mTOR, Ras/Raf/MAPK), cell cycle machinery (CDKs, TERT, TOP2A, TOP2B) as well as epigenetics regulators (HDACs). These results suggest that fatty esters of phloridzin have potential chemotherapeutic effects mediated through the attenuated expression of several key proteins involved in cell cycle regulation, DNA topoisomerases IIα activity and epigenetic mechanisms followed by cell cycle arrest and apoptosis.

Targeting FASN in Breast Cancer and the Discovery of Promising Inhibitors from Natural Products Derived from Traditional Chinese Medicine

Molecular targeted therapy has been developed for cancer chemoprevention and treatment. Cancer cells process a fundamental change in its bioenergetic metabolism from normal cells on an altered lipid metabolism, also known as the de novo fatty acid synthesis, for sustaining their high proliferation rates. Fatty acid synthesis is now associated with clinically aggressive tumor behavior and tumor cell growth and has become a novel target pathway for chemotherapy development. Although the underlying mechanisms of the altered de novo fatty acid synthesis still remains unclear, recent progress has shown that by targeting Fatty acid synthase (FASN), a key enzyme that catalyzes the synthesis of endogenous long chain fatty acid could be a critical target for drug discovery. However, relatively few FASN inhibitors have been discovered. With the long history of clinical practices and numerous histological case study reports, traditional Chinese medicine enjoys an important role in seeking bioactive anticancer natural compounds. Herein, we will give an overall picture of the current progress of molecular targeted therapy in cancer fatty acid synthesis, describe the advances in the research on natural products-derived FASN inhibitors and their potential for enhancing our understanding of fatty acids in tumor biology, and may provide new therapeutic moieties for breast cancer patient care.

Down-regulation of lipid raft-associated onco-proteins via cholesterol-dependent lipid raft internalization in docosahexaenoic acid-induced apoptosis

Lipid rafts, plasma membrane microdomains, are important for cell survival signaling and cholesterol is a critical lipid component for lipid raft integrity and function. DHA is known to have poor affinity for cholesterol and it influences lipid rafts. Here, we investigated a mechanism underlying the anti-cancer effects of DHA using a human breast cancer cell line, MDA-MB-231. We found that DHA decreased cell surface levels of lipid rafts via their internalization, which was partially reversed by cholesterol addition. With DHA treatment, caveolin-1, a marker for rafts, and EGFR were colocalized with LAMP-1, a lysosomal marker, in a cholesterol-dependent manner, indicating that DHA induces raft fusion with lysosomes. DHA not only displaced several raft-associated onco-proteins, including EGFR, Hsp90, Akt, and Src, from the rafts but also decreased total levels of those proteins via multiple pathways, including the proteasomal and lysosomal pathways, thereby decreasing their activities. Hsp90 overexpression maintained its client proteins, EGFR and Akt, and attenuated DHA-induced cell death. In addition, overexpression of Akt or constitutively active Akt attenuated DHA-induced apoptosis. All these data indicate that the anti-proliferative effect of DHA is mediated by targeting of lipid rafts via decreasing cell surface lipid rafts by their internalization, thereby decreasing raft-associated onco-proteins via proteasomal and lysosomal pathways and decreasing Hsp90 chaperone function.

DHA is a more potent inhibitor of breast cancer metastasis to bone and related osteolysis than EPA

Breast cancer patients often develop bone metastasis evidenced by osteolytic lesions, leading to severe pain and bone fracture. Attenuation of breast cancer metastasis to bone and associated osteolysis by fish oil, rich in EPA and DHA, has been demonstrated previously. However, it was not known whether EPA and DHA differentially or similarly affect breast cancer bone metastasis and associated osteolysis. In vitro culture of parental and luciferase gene encoded MDA-MB-231 human breast cancer cell lines treated with EPA and DHA revealed that DHA inhibits proliferation and invasion of breast cancer cells more potently than EPA. Intra-cardiac injection of parental and luciferase gene encoded MDA-MB-231 cells to athymic NCr nu/nu mice demonstrated that DHA-treated mice had significantly less breast cancer cell burden in bone, and also significantly less osteolytic lesions than EPA-treated mice. In vivo cell migration assay as measured by luciferase intensity revealed that DHA attenuated cell migration specifically to the bone. Moreover, the DHA-treated group showed reduced levels of CD44 and TRAP positive area in bone compared to EPA-treated group. Breast cancer cell burden and osteolytic lesions were also examined in intra-tibially breast cancer cell injected mice and found less breast cancer cell growth and associated osteolysis in DHA-treated mice as compared to EPA-treated mice. Finally, doxorubicin-resistant MCF-7 (MCF-7dox) human breast cancer cell line was used to examine if DHA can improve sensitization of MCF-7dox cells to doxorubicin. DHA improved the inhibitory effect of doxorubicin on proliferation and invasion of MCF-7dox cells. Interestingly, drug resistance gene P-gp was also down-regulated in DHA plus doxorubicin-treated cells. In conclusion, DHA attenuates breast cancer bone metastasis and associated osteolysis more potently than EPA, possibly by inhibiting migration of breast cancer cell to the bone as well as by inhibiting osteoclastic bone resorption.

Inhibition of the HER2 pathway by n-3 polyunsaturated fatty acids prevents breast cancer in fat-1 transgenic mice

Overexpression of the tyrosine kinase receptor, ErbB2/HER2/Neu, occurs in 25-30% of invasive breast cancer (BC) with poor patient prognosis. Due to confounding factors, inconsistencies still remain regarding the protective effects of n-3 polyunsaturated fatty acids (PUFAs) on BC. We therefore evaluated whether fat-1 transgenic mice, endogenously synthesizing n-3 PUFAs from n-6 PUFAs, were protected against BC development, and we then aimed to study in vivo a mechanism potentially involved in such protection. E0771 BC cells were implanted into fat-1 and wild-type (WT) mice. After tumorigenesis examination, we analyzed the expression of proteins involved in the HER2 signaling pathway and lipidomic analyses were performed in tumor tissues and plasma. Our results showed that tumors totally disappeared by day 15 in fat-1 mice but continued to grow in WT mice. This prevention can be related in part to significant repression of the HER2/β-catenin signaling pathway and formation of significant levels of n-3 PUFA-derived bioactive mediators (particularly 15-hydroxyeicosapentaenoic acid, 17-hydroxydocosahexaenoic acid, and prostaglandin E3) in the tumors of fat-1 mice compared with WT mice. All together these data demonstrate an anti-BC effect of n-3 PUFAs through, at least in part, HER2 signaling pathway downregulation, and highlight the importance of gene-diet interactions in BC.

Omega-3 polyunsaturated fatty acids selectively inhibit growth in neoplastic oral keratinocytes by differentially activating ERK1/2

The long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs)—eicosapentaenoic acid (EPA) and its metabolite docosahexaenoic acid (DHA)—inhibit cancer formation in vivo, but their mechanism of action is unclear. Extracellular signal-regulated kinase 1/2 (ERK1/2) activation and inhibition have both been associated with the induction of tumour cell apoptosis by n-3 PUFAs. We show here that low doses of EPA, in particular, inhibited the growth of premalignant and malignant keratinocytes more than the growth of normal counterparts by a combination of cell cycle arrest and apoptosis. The growth inhibition of the oral squamous cell carcinoma (SCC) lines, but not normal keratinocytes, by both n-3 PUFAs was associated with epidermal growth factor receptor (EGFR) autophosphorylation, a sustained phosphorylation of ERK1/2 and its downstream target p90RSK but not with phosphorylation of the PI3 kinase target Akt. Inhibition of EGFR with either the EGFR kinase inhibitor AG1478 or an EGFR-blocking antibody inhibited ERK1/2 phosphorylation, and the blocking antibody partially antagonized growth inhibition by EPA but not by DHA. DHA generated more reactive oxygen species and activated more c-jun N-terminal kinase than EPA, potentially explaining its increased toxicity to normal keratinocytes. Our results show that, in part, EPA specifically inhibits SCC growth and development by creating a sustained signalling imbalance to amplify the EGFR/ERK/p90RSK pathway in neoplastic keratinocytes to a supraoptimal level, supporting the chemopreventive potential of EPA, whose toxicity to normal cells might be reduced further by blocking its metabolism to DHA. Furthermore, ERK1/2 phosphorylation may have potential as a biomarker of n-3 PUFA function in vivo.

Mechanisms of omega-3 polyunsaturated fatty acids in prostate cancer prevention

This review focuses on several key areas where progress has been made recently to highlight the role of omega-3 polyunsaturated fatty acid in prostate cancer prevention.

Dietary fat in breast cancer survival

Laboratory evidence suggests a plausible role for dietary fat in breast cancer pathophysiology. We conducted a systematic literature review to assess the epidemiological evidence on the impact of total dietary fat and fat subtypes, measured pre- and/or postcancer diagnosis, in relation to breast cancer-specific and all-cause mortality among breast cancer survivors. Studies were included if they were in English, had a sample size ≥200, and presented the hazard ratio/rate ratio for recurrence, disease-specific mortality, or all-cause mortality (n = 18). Although the results are mixed, most studies suggested that higher saturated fat intake prediagnosis was associated with increased risk of breast cancer-specific and all-cause mortality. Postdiagnostic trans fat intake was associated with a 45% and 78% increased risk of all-cause mortality. Higher monounsaturated fat intake before and after diagnosis was generally associated with increased risk of all-cause and breast cancer-specific mortality, albeit the majority of the studies were statistically nonsignificant. Two studies evaluating omega-3 fat intake suggested an inverse association with all-cause mortality. Although there were too few studies on fat subtypes to draw definitive conclusions, high consumption of saturated fat may exert a detrimental effect on breast cancer-specific and all-cause mortality, whereas omega-3 fat may be beneficial. The inconsistent and limited evidence warrants research to assess the impact of consumption of fat subtypes on breast cancer recurrence and mortality.

Polyunsaturated fatty acids affect the localization and signaling of PIP3/AKT in prostate cancer cells

AKT is a serine-threonine protein kinase that plays important roles in cell growth, proliferation and apoptosis. It is activated after binding to phosphatidylinositol phosphates (PIPs) with phosphate groups at positions 3,4 and 3,4,5 on the inositol ring. In spite of extensive research on AKT, one aspect has been largely overlooked, namely the role of the fatty acid chains on PIPs. PIPs are phospholipids composed of a glycerol backbone with fatty acids at the sn-1 and sn-2 position and inositol at the sn-3 position. Here, we show that polyunsaturated fatty acids (PUFAs) modify phospholipid content. Docosahexaenoic acid (DHA), an ω3 PUFA, can replace the fatty acid at the sn-2 position of the glycerol backbone, thereby changing the species of phospholipids. DHA also inhibits AKT(T308) but not AKT(S473) phosphorylation, alters PI(3,4,5)P3 (PIP3) and phospho-AKT(S473) protein localization, decreases pPDPK1(S241)-AKT and AKT-BAD interaction and suppresses prostate tumor growth. Our study highlights a potential novel mechanism of cancer inhibition by ω3 PUFA through alteration of PIP3 and AKT localization and affecting the AKT signaling pathway.

Combination of intermittent calorie restriction and eicosapentaenoic acid for inhibition of mammary tumors

There are a number of dietary interventions capable of inhibiting mammary tumorigenesis; however, the effectiveness of dietary combinations is largely unexplored. Here, we combined 2 interventions previously shown individually to inhibit mammary tumor development. The first was the use of the omega-3 fatty acid, eicosapentaenoic acid (EPA), and the second was the implementation of calorie restriction. MMTV-Her2/neu mice were used as a model for human breast cancers, which overexpress Her2/neu. Six groups of mice were enrolled. Half were fed a control (Con) diet with 10.1% fat calories from soy oil, whereas the other half consumed a diet with 72% fat calories from EPA. Within each diet, mice were further divided into ad libitum (AL), chronic calorie-restricted (CCR), or intermittent calorie-restricted (ICR) groups. Mammary tumor incidence was lowest in ICR-EPA (15%) and highest in AL-Con mice (87%), whereas AL-EPA, CCR-Con, CCR-EPA, and ICR-Con groups had mammary tumor incidence rates of 63%, 47%, 40%, and 59%, respectively. Survival was effected similarly by the interventions. Consumption of EPA dramatically reduced serum leptin (P < 0.02) and increased serum adiponectin in the AL-EPA mice compared with AL-Con mice (P < 0.001). Both CCR and ICR decreased serum leptin and insulin-like growth factor I (IGF-I) compared with AL mice but not compared with each other. These results illustrate that mammary tumor inhibition is significantly increased when ICR and EPA are combined as compared with either intervention alone. This response may be related to alterations in the balance of serum growth factors and adipokines.

N-3 poly-unsaturated fatty acids shift estrogen signaling to inhibit human breast cancer cell growth

Although evidence has shown the regulating effect of n-3 poly-unsaturated fatty acid (n-3 PUFA) on cell signaling transduction, it remains unknown whether n-3 PUFA treatment modulates estrogen signaling. The current study showed that docosahexaenoic acid (DHA, C22:6), eicosapentaenoic acid (EPA, C20:5) shifted the pro-survival and proliferative effect of estrogen to a pro-apoptotic effect in human breast cancer (BCa) MCF-7 and T47D cells. 17 β-estradiol (E2) enhanced the inhibitory effect of n-3 PUFAs on BCa cell growth. The IC50 of DHA or EPA in MCF-7 cells decreased when combined with E2 (10 nM) treatment (from 173 µM for DHA only to 113 µM for DHA+E2, and from 187 µm for EPA only to 130 µm for EPA+E2). E2 also augmented apoptosis in n-3 PUFA-treated BCa cells. In contrast, in cells treated with stearic acid (SA, C18:0) as well as cells not treated with fatty acid, E2 promoted breast cancer cell growth. Classical (nuclear) estrogen receptors may not be involved in the pro-apoptotic effects of E2 on the n-3 PUFA-treated BCa cells because ERα agonist failed to elicit, and ERα knockdown failed to block E2 pro-apoptotic effects. Subsequent studies reveal that G protein coupled estrogen receptor 1 (GPER1) may mediate the pro-apoptotic effect of estrogen. N-3 PUFA treatment initiated the pro-apoptotic signaling of estrogen by increasing GPER1-cAMP-PKA signaling response, and blunting EGFR, Erk 1/2, and AKT activity. These findings may not only provide the evidence to link n-3 PUFAs biologic effects and the pro-apoptotic signaling of estrogen in breast cancer cells, but also shed new insight into the potential application of n-3 PUFAs in BCa treatment.

Carcinogenesis alters fatty acid profile in breast tissue

Cancerogenesis is associated with cell membrane changes. The aim of this study was to investigate whether breast tissues with different degrees of cancer involvement have different fatty acid profiles. Fourteen breast cancer patients with a mean age of 61 years were recruited. Morphological features of the tumoral specimens were characterized. Approximately 60 % of patients had invasive ductal carcinoma, and 80 % were ER positive; 65 % were PR positive; and 65 % were HER2 negative. The segments with confirmed cancer had significantly less amounts of total lipids as compared with the corresponding grossly normal or interface tissues. The fatty acid profile in cancer tissue was significantly different from that in other tissues. Fatty acid composition of five classes of phospholipids revealed the variations between cancer tissue and the other two segments. A transition of changes in fatty acid composition in these fractions of phospholipids was observed. The interface tissue had intermediate amounts of several fatty acids including palmitic acid, stearic acid, and arachidonic acid. Interestingly, we observed significantly higher amounts of the n-3 fatty acid DHA in cancer tissue as compared to the other two tissues. Data from this study will provide evidence that biochemical changes particularly phospholipid composition may take place well in advance prior to morphological changes. Should this theory be confirmed by larger studies, deviation of phospholipid composition from normal values can be used as markers of susceptibility of tissue to cancer development.

Selective sensitization of tumors to chemotherapy by marine-derived lipids: a review

Despite great improvements, a significant proportion of cancer patients still die, mainly because of the development of metastases. At this stage, current treatments still rely heavily on conventional chemotherapy for most cancers. The efficacy of chemotherapy is dose-dependent, which is limited by toxicity to non-tumor tissues, as a result of its poor tumor selectivity. To improve survival length and preserve quality of life, the challenge is to develop approaches aimed at increasing chemotherapy toxicity to tumor tissue while not affecting non-tumor tissues. Marine-derived lipids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have the potential to differentially sensitize tissues to chemotherapy. These lipids enhance the cytotoxicity of 15 anticancer drugs (antimetabolites, alkylating or intercalating agents, microtubule stabilizers, Abl tyrosine kinase inhibitor and arsenic trioxide) to a variety of cancer cell lines or tumors in animals, used as models for breast, prostate, colonic, lung, cervical, ovarian cancers, neuroblastomas, leukemia or lymphomas. However, DHA and EPA do not sensitize non-tumor tissues to anticancer drugs, which suggests that the effect of these lipids is tumor selective. Two phase II clinical trials already support these results, and randomized, phase III trials are ongoing. In this review, we discuss the double-faceted properties of these lipids, and then focus on their potential for transfer to the patient in the light of current therapeutic strategies. Should their beneficial effects be confirmed, the consequences could be considerable by opening up the prospect of systematic supplementation during cancer treatment, a significant shift in current cancer therapeutic paradigms.

Omega-3 but not omega-6 unsaturated fatty acids inhibit the cancer-specific ENOX2 of the HeLa cell surface with no effect on the constitutive ENOX1

Epidemiological and laboratory studies suggest that dietary fatty acids (oleic acid (in olive oil), eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) (in fish oil)) play important roles in carcinogenesis. The most potent antitumor effects of all fatty acids are given by fatty acid conjugated linoleic acid (CLA). The antitumor effects of CLA may be mediated through enhanced apoptosis. While CLA, EPA, and DHA (omega-3 polyunsaturated fatty acids) have inhibitory effects on cancer cells, omega-6 fatty acids have often shown negative or potentiating effects on cancer cells. Linoleic acid (an omega-6) is desaturated in the cell by delta 6 and 5 destaturases to form arachidonic acid. COX 1 and 2 isoforms then act on arachidonic acid to form prostaglandins and other related regulatory molecules. It is normally thought that what is important to the development of the cancerous phenotype is some balance of these various metabolites. In experiments with surface NOX proteins released from HeLa cells, spectrophotometric measurements of the oxidation of NADH revealed inhibition of the cancer-specific ENOX2 activity by CLA and the omega-3 fatty acids, eicosapentaenoic, docosahexaenoic, and α-linolenic acids. The constitutive ENOX1 activity was not inhibited. In contrast, the omega-6 fatty acids, linoleic acid, and arachidonic acid inhibited neither ENOX1 nor ENOX2. The findings indicate the possibility that a direct effect of CLA and omega-3 fatty acids on ENOX2 may be responsible for the potent activity of CLA and omega-3 fatty acids in cancer prevention and therapy.

The janus face of lipids in human breast cancer: how polyunsaturated Fatty acids affect tumor cell hallmarks

For several years, lipids and especially n - 3 and n - 6 polyunsaturated fatty acids (PUFAs) receive much attention in human health. Epidemiological studies tend to correlate a PUFA-rich diet with a reduced incidence of cancer, including breast cancer. However, the molecular and cellular mechanisms supporting the effect of PUFAs in breast cancer cells remain relatively unknown. Here, we review some recent progress in understanding the impact that PUFA may have on breast cancer cell proliferation, apoptosis, migration, and invasion. While most of the results obtained with docosahexaenoic acid and/or eicosapentaenoic acid show a decrease of tumor cell proliferation and/or aggressivity, there is some evidence that other lipids, which accumulate in breast cancer tissues, such as arachidonic acid may have opposite effects. Finally, lipids and especially PUFAs appear as potential adjuvants to conventional cancer therapy.

Lipid raft disruption by docosahexaenoic acid induces apoptosis in transformed human mammary luminal epithelial cells harboring HER-2 overexpression

In HER-2-overexpressing breast cells, HER-2 receptors exist on the cell surface as monomers, homodimers and heterodimers. For signal activation and transduction to occur, HER-2 must be localized to lipid rafts. Therefore, we hypothesized that the amount of lipid rafts on the cell membrane would be a factor in HER-2 signaling. To test this, we used HB4a (an untransformed human mammary epithelial cell line) and HB4aC5.2 cells. HB4aC5.2 cells are HB4a derivatives that have been transfected with five copies of pJ5E.c-ErbB-2 and express approximately 900 times more HER-2 than HB4a cells. In these cells, HER-2 overexpression was accompanied by increased lipid rafts in cell membranes, a hyperactivation of downstream Akt and ERK1/2 proteins, and an increased rate of cell growth compared to HB4a. In addition, HER-2 overexpression was associated with an increased activation of FASN, a key enzyme involved in cellular lipogenesis. Its final product, palmitate, is frequently used to synthesize lipid rafts. We further hypothesized that treatment with docosahexaenoic acid (DHA), an omega-3 fatty acid, would disrupt the lipid rafts and lead to a growth arrest. In HB4aC5.2 cells, but not HB4a cells, we found that DHA treatment disrupted lipid raft; inhibited HER-2 signaling by decreasing activation of Akt, ERK1/2 and FASN proteins; and induced apoptosis. Although little is known about lipid rafts, our data support the idea that disturbances in these microdomains induced by DHA may represent a useful tool for controlling the signaling initiated by HER-2 receptors and its therapeutic potential in the treatment of HER-2 positive breast cancer.

Regulation of rat brain polyunsaturated fatty acid (PUFA) metabolism during graded dietary n-3 PUFA deprivation

Knowing threshold changes in brain lipids and lipid enzymes during dietary n-3 polyunsaturated fatty acid deprivation may elucidate dietary regulation of brain lipid metabolism. To determine thresholds, rats were fed for 15 weeks DHA-free diets having graded reductions of α-linolenic acid (α-LNA). Compared with control diet (4.6% α-LNA), plasma DHA fell significantly at 1.7% dietary α-LNA while brain DHA remained unchanged down to 0.8% α-LNA, when plasma and brain docosapentaenoic acid (DPAn-6) were increased and DHA-selective iPLA(2) and COX-1 activities were downregulated. Brain AA was unchanged by deprivation, but AA selective-cPLA(2), sPLA(2) and COX-2 activities were increased at or below 0.8% dietary α-LNA, possibly in response to elevated brain DPAn-6. In summary, homeostatic mechanisms appear to maintain a control brain DHA concentration down to 0.8% dietary DHA despite reduced plasma DHA, when DPAn-6 replaces DHA. At extreme deprivation, decreased brain iPLA(2) and COX-1 activities may reduce brain DHA loss.

Nutrition modulation of gastrointestinal toxicity related to cancer chemotherapy: from preclinical findings to clinical strategy

Chemotherapy-induced gut toxicity is a major dose-limiting toxicity for many anticancer drugs. Gastrointestinal (GI) complications compromise the efficacy of chemotherapy, promote overall malnutrition, aggravate cancer cachexia, and may contribute to worsened prognosis. The GI tract is an attractive target for nutrition modulation, owing to its direct exposure to the diet, participation in uptake and metabolism of nutrients, high rate of cell turnover, and plasticity to nutrition stimuli. Glutamine, ω-3 polyunsaturated fatty acids, and probiotics/prebiotics are therapeutic factors that potentially modulate GI toxicity related to cancer treatments. Preclinical and clinical evidence are reviewed to critically define plausible benefits of these factors and their potential development into adjuncts to cancer chemotherapy. Mechanisms underlying the action of these nutrients are being unraveled in the laboratory. Optimal strategies to translate these findings into clinical care still remain to be elucidated. Key questions that remain to be answered include the following: which nutrient or combination of nutrients is selected for which patient and chemotherapy regimen? What mechanisms are responsible for modulation, and how are nutrient(s) administered in a clinically optimal manner? Research exploring interactions between different nutrients in GI protection is ongoing and demands further understanding. How nutrition preparations given to chemotherapy-treated patients are formulated in terms of component selection and dose optimization should be carefully studied and justified.

Dietary n-6 PUFA deprivation downregulates arachidonate but upregulates docosahexaenoate metabolizing enzymes in rat brain

BACKGROUND

Dietary n-3 polyunsaturated fatty acid (PUFA) deprivation increases expression of arachidonic acid (AA 20:4n-6)-selective cytosolic phospholipase A(2) (cPLA(2)) IVA and cyclooxygenase (COX)-2 in rat brain, while decreasing expression of docosahexaenoic acid (DHA 22:6n-3)-selective calcium-independent iPLA(2) VIA. Assuming that these enzyme changes represent brain homeostatic responses to deprivation, we hypothesized that dietary n-6 PUFA deprivation would produce changes in the opposite directions.

METHODS

Brain expression of PUFA-metabolizing enzymes and their transcription factors was quantified in male rats fed an n-6 PUFA adequate or deficient diet for 15weeks post-weaning.

RESULTS

The deficient compared with adequate diet increased brain mRNA, protein and activity of iPLA(2) VIA and 15-lipoxygenase (LOX), but decreased cPLA(2) IVA and COX-2 expression. The brain protein level of the iPLA(2) transcription factor SREBP-1 was elevated, while protein levels were decreased for AP-2α and NF-κB p65, cPLA(2) and COX-2 transcription factors, respectively.

CONCLUSIONS

With dietary n-6 PUFA deprivation, rat brain PUFA metabolizing enzymes and some of their transcription factors change in a way that would homeostatically dampen reductions in brain n-6 PUFA concentrations and metabolism, while n-3 PUFA metabolizing enzyme expression is increased. The changes correspond to reported in vitro enzyme selectivities for AA compared with DHA.

Fish oil prevents breast cancer cell metastasis to bone

The data derived from epidemiological and animal models confirm a beneficial effect of fish oil (rich in ω-3 polyunsaturated fatty acids) in the amelioration of tumor growth and progression, including breast cancer. The breast cancer patients often develop bone metastasis evidenced by osteolytic lesions, leading to severe pain and bone fracture. Using a mouse model of MDA-MB-231 human breast cancer cell metastasis to bone, here we show that fish oil diet enriched in DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) prevents the formation of osteolytic lesions in bone, indicating suppression of cancer cell metastasis to bone. These results are supported by our data showing both DHA and EPA significantly attenuate the migration/invasion of MDA-MB-231 breast cancer cells in culture. The mechanism that limits breast cancer cells to selective metastasis to bone remains hitherto unexplored. Aberrant increased expression of CD44 is associated with generation of cancer stem cells, which contribute to metastasis of breast cancer cells. We demonstrate that DHA and EPA significantly inhibit the expression of CD44 protein and mRNA by a transcriptional mechanism. Furthermore, we show markedly reduced levels of CD44 mRNA and protein in the tumors of mice, which were fed fish oil diet than those in control diet. Our data provide the first evidence for a salutary effect of fish oil on breast cancer metastasis to bone. Our results identify a novel function of the fish oil active components, DHA and EPA, which target the cell-intrinsic pro-metastatic molecule CD44 to inhibit migration/invasion.

Lipids, mitochondria and cell death: implications in neuro-oncology

Polyunsaturated fatty acids (PUFAs) are known to inhibit cell proliferation of many tumour types both in vitro and in vivo. Their capacity to interfere with cell proliferation has been linked to their induction of reactive oxygen species (ROS) production in tumour tissues leading to cell death through apoptosis. However, the exact mechanisms of action of PUFAs are far from clear, particularly in brain tumours. The loss of bound hexokinase from the mitochondrial voltage-dependent anion channel has been directly related to loss of protection from apoptosis, and PUFAs can induce this loss of bound hexokinase in tumour cells. Tumour cells overexpressing Akt activity, including gliomas, are sensitised to ROS damage by the Akt protein and may be good targets for chemotherapeutic agents, which produce ROS, such as PUFAs. Cardiolipin peroxidation may be an initial event in the release of cytochrome c from the mitochondria, and enriching cardiolipin with PUFA acyl chains may lead to increased peroxidation and therefore an increase in apoptosis. A better understanding of the metabolism of fatty acids and eicosanoids in primary brain tumours such as gliomas and their influence on energy balance will be fundamental to the possible targeting of mitochondria in tumour treatment.

The nutritional and clinical significance of lipid rafts

PURPOSE OF REVIEW

Lipid rafts are potentially modifiable by diet, particularly (but not exclusively) by dietary fatty acids. This review examines the potential for dietary modification of raft structure and function in the immune system, brain and retinal tissue, the gut, and in cancer cells.

RECENT FINDINGS

In-vitro and ex-vivo studies suggest that dietary n-3 polyunsaturated fatty acids (PUFAs) may exert immunosuppressive and anticancer effects through changes in lipid raft organization. In addition, gangliosides and cholesterol may modulate lipid raft organization in a number of tissues, and recent work has highlighted sphingolipids in membrane microdomains as potential targets for inhibition of tumor growth. The roles of fatty acids and gangliosides, especially in relation to lipid rafts, in cognitive development, age-related cognitive decline, psychiatric disorders, and Alzheimer's disease are poorly understood and require further investigation. The roles of lipid rafts in cancer, in microbial pathogenesis, and in insulin resistance are starting to emerge, and indicate compelling evidence for the growing importance of membrane microdomains in health and disease.

SUMMARY

In-vitro and animal studies show that n-3 PUFAs, cholesterol, and gangliosides modulate the structure and composition of lipid rafts, potentially influencing a wide range of biological processes, including immune function, neuronal signaling, cancer cell growth, entry of pathogens through the gut barrier, and insulin resistance in metabolic disorders. The physiological, clinical, and nutritional relevance of these observations remains to be determined.

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.