Eicosapentaenoic acid suppresses cell proliferation in MCF-7 human breast cancer xenografts in nude rats via a pertussis toxin-sensitive signal transduction pathway

Oncogenic signaling of the free-fatty acid receptors FFA1 and FFA4 in human breast carcinoma cells

Globally, breast cancer is the most frequent type of cancer in women, and most breast cancer-associated deaths are due to metastasis and recurrence of the disease. Dietary habits, specifically dietary fat intake is a crucial risk factor involved in breast cancer development and progression. Decades of research has revealed that free-fatty acids (FFA) modulate carcinogenic processes through fatty acid metabolism and lipid peroxidation. The ground-breaking discovery of free-fatty acid receptors, which are members of the G-protein coupled receptor (GPCR) superfamily, has led to the realization that FFA can also act via these receptors to modulate carcinogenic effects. The long-chain free-fatty acid receptors FFA1 (previously termed GPR40) and FFA4 (previously termed GPR120) are activated by mono- and polyunsaturated fatty acids including ω-3, 6, and 9 fatty acids. Initial enthusiasm towards the study of these receptors focused on their insulin secretagogue and sensitization effects, and the downstream associated metabolic regulation. However, recent studies have demonstrated that abnormal expression and/or aberrant FFA1/FFA4 signaling are evident in human breast carcinomas, suggesting that FFA receptors could be a promising target in the treatment of breast cancer. The current review discusses the diverse roles of FFA1 and FFA4 in the regulation of cell proliferation, migration, invasion, and chemotherapy resistance in human breast carcinoma cells and tissue.

The combined effect of fish oil containing Omega-3 fatty acids and Lactobacillus plantarum on colorectal cancer

Colorectal cancer (CRC) is one of the deadliest malignancies. Recent attempts have indicated the role of diet in the etiology of CRC. Natural dietary compounds such as probiotics and Omega-3 fatty acids that act synergistically can be beneficial in finding a tremendous solution against CRC. To date, the combined effect of fish oil containing Omega-3 fatty acids (Omega-3) and Lactobacillus plantarum (L. plantarum) on CRC has been left behind. We here evaluated the effects of co-encapsulation of Omega-3 and probiotic bacteria on CRC cell lines compared to normal cells. Omega-3 and L. plantarum bacteria were co-encapsulated in three ways, including gelatin-gum Arabic, gelatin-chitosan, and chitosan-gum Arabic complex coacervate microcapsules. After treatment of cells (Normal [L929] and colorectal [C26]) by L. plantarum, Omega-3, and microcapsules, viability and growth capacity of cell lines were measured using the MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay. Isolated total RNA was used to evaluate the expression profile of BCL2-associated X protein (BAX), B-cell lymphoma 2 (BCL-2), and Caspase-3 (CASP3) genes by real-time polymerase chain reaction (PCR). Statistical analysis was performed with SPSS 25 software. A value of p < .05 was considered statistically significant. The results indicated a significant reduction in cell viability of C26 in a concentration-dependent manner in the treated cells with all treatments, except gelatin-gum Arabic microcapsules. The messenger RNA (mRNA) expression level of the BAX and CASP3 genes in C26 cells being treated with all treatments significantly increased than in untreated cells, and the expression level of the anti-apoptotic factor of the BCL-2 gene decreased in C26 cells simultaneously (p < .05). Although, the combined effect of Omega-3 and L. plantarum and microcapsulated treatments had no more effect on viability and apoptosis gene expression of cancer cells compared to Omega-3 or L. plantarum. In conclusion, combination therapy with fish oil containing Omega-3 and L. plantarum does not improve the anticancer effect of each alone.

15-Lipoxygenase and its metabolites in the pathogenesis of breast cancer: A double-edged sword

15-lipoxygenase is one of the key enzymes for the metabolism of unsaturated fatty acids that its manipulation has been proposed recently as a new molecular target for regulating cancer cell growth. Aberrant expression of 15-lipoxygenase enzyme seems to play an indicative role in the pathology of different cancer types, tumor progression, metastasis, or apoptosis. Based on the fact that breast cancer is one of the most common cancers that imposes a burden of mortality in women also, on the other hand, evidence in experimental models and human studies indicate the emerging role of the 15-lipoxygenase pathway in breast cancer pathogenesis, we present a review of recent findings related to the role of 15- lipoxygenase enzyme and metabolites in breast cancer growth, apoptosis, metastasis, and invasion as well as their local and circulating expression pattern in patients with breast cancer. Our review supports the emerging role of 15- lipoxygenase in molecular and cellular processes regulating breast tumor cell fate with both positive and negative effects.

Dietary Melatonin and Omega-3 Fatty Acids Induce Human Cancer Xenograft Regression In Vivo in Rats by Suppressing Linoleic Acid Uptake and Metabolism

Melatonin, the circadian nighttime neurohormone, and eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), which are omega-3 fatty acids (FA) found in high concentrations in fish oil (FO) and plants, abrogate the oncogenic effects of linoleic acid (LA), an omega-6 FA, on the growth of rodent tumors and human breast, prostate, and head and neck squamous cell carcinoma (HNSCC) xenografts in vivo. Here we determined and compared the long-term effects of these inhibitory agents on tumor regression and LA uptake and metabolism to the mitogenic agent 13-[S]-hydroxyoctadecadienoic acid (13-[S]-HODE) in human prostate cancer 3 (PC3) and FaDu HNSCC xenografts in tumor-bearing male nude rats. Rats in this study were split into 3 groups and fed one of 2 diets: one diet containing 5% corn oil (CO, high LA), 5% CO oil and melatonin (2 μg/mL) or an alternative diet 5% FO (low LA). Rats whose diet contained melatonin had a faster rate of regression of PC3 prostate cancer xenografts than those receiving the FO diet, while both in the melatonin and FO groups induced the same rate of regression of HNSCC xenografts. The results also demonstrated that dietary intake of melatonin or FO significantly inhibited tumor LA uptake, cAMP content, 13-[S]-HODE formation, [³H]-thymidine incorporation into tumor DNA, and tumor DNA content. Therefore, long-term ingestion of either melatonin or FO can induce regression of PC3 prostate and HNSCC xenografts via a mechanism involving the suppression of LA uptake and metabolism by the tumor cells.

Targeting ferroptosis in breast cancer

Ferroptosis is a recently discovered distinct type of regulated cell death caused by the accumulation of lipid-based ROS. Metabolism and expression of specific genes affect the occurrence of ferroptosis, making it a promising therapeutic target to manage cancer. Here, we describe the current status of ferroptosis studies in breast cancer and trace the key regulators of ferroptosis back to previous studies. We also compare ferroptosis to common regulated cell death patterns and discuss the sensitivity to ferroptosis in different subtypes of breast cancer. We propose that viewing ferroptosis-related studies from a historical angle will accelerate the development of ferroptosis-based biomarkers and therapeutic strategies in breast cancer.

Bioactive Lipids in Age-Related Disorders

Our own studies and those of others have shown that defects in essential fatty acid (EFA) metabolism occurs in age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, immune dysfunction and cancer. It has been noted that in all these disorders there could occur a defect in the activities of desaturases, cyclo-oxygenase (COX), and lipoxygenase (LOX) enzymes leading to a decrease in the formation of their long-chain products gamma-linolenic acid (GLA), arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). This leads to an increase in the production of pro-inflammatory prostaglandin E2 (PGE2), thromboxanes (TXs), and leukotrienes (LTs) and a decrease in anti-inflammatory lipoxin A4, resolvins, protectins and maresins. All these bioactive molecules are termed as bioactive lipids (BALs). This imbalance in the metabolites of EFAs leads to low-grade systemic inflammation and at times acute inflammatory events at specific local sites that trigger the development of various age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, coronary heart disease, atherosclerosis, and immune dysfunction as seen in rheumatoid arthritis, lupus, nephritis and other localized inflammatory conditions. This evidence implies that methods designed to restore BALs to normal can prevent age-related disorders and enhance longevity and health.

The role of free-fatty acid receptor-4 (FFA4) in human cancers and cancer cell lines

A dietary influence on cancer progression has been evident for many decades, and dietary fatty acids, particularly long chain mono- and polyunsaturated fatty acids, have been shown to play significant roles in influencing growth of a variety of human cancers. The discovery of the family of cell-surface free-fatty acid receptors, which include the long-chain fatty acid receptors FFA1 and FFA4, suggest that many of the effects of dietary fats could be receptor-mediated. FFA4 is ubiquitously expressed and has recently been shown to modulate a variety of important anti-inflammatory and metabolic processes. Since FFA4 is currently an attractive drug target for treatment of metabolic disorders such as diabetes and obesity, understanding its role in cancer progression is critical towards the drug discovery process. In this research update, the current body of knowledge on the role of this receptor in regulating cancer cell proliferation, migration, and invasion, as well as in vivo tumorigenesis is reviewed.

Lipid Extracts from the Brains of Silver Carp (Hypophthalmichthys molitrix) Induce Apoptosis in MCF-7 Cells through the Generation of Reactive Oxygen Species and the Mitochondrial Pathway

Previous studies have verified the protective role of n3 polyunsaturated fatty acids (PUFAs) in cancer. Fish brain lipids are rich in n3 PUFAs. However, the action and mechanism of their potent anticancer activities remain unclear. In this study, polar lipids (PLs) and neutral lipids (NLs) were isolated from the total lipids (TLs) of the silver carp brain, and the anticancer effects of the lipid fractions (LFs) were examined in a human breast cancer cell line (MCF-7). The LFs effectively inhibited the cell proliferation of MCF-7 cells in a time- and concentration-dependent manner by cell cycle arrest at the S stage and induction of apoptosis. Further analyses showed that the apoptotic effect of the LFs on MCF-7 cells was associated with the accumulation of elevated levels of reactive oxygen species and the loss of mitochondrial membrane potential. Among the TLs, PLs were more effective at causing breast cancer cell death than NLs. Our study showed that the LFs from silver carp brains may aid the prevention and treatment of human breast cancer.

Free Fatty Acid Receptors and Cancer: From Nutrition to Pharmacology

The effects of fatty acids on cancer cells have been studied for decades. The roles of dietary long-chain n-3 polyunsaturated fatty acids, and of microbiome-generated short-chain butyric acid, have been of particular interest over the years. However, the roles of free fatty acid receptors (FFARs) in mediating effects of fatty acids in tumor cells have only recently been examined. In reviewing the literature, the data obtained to date indicate that the long-chain FFARs (FFA1 and FFA4) play different roles than the short-chain FFARs (FFA2 and FFA3). Moreover, FFA1 and FFA4 can in some cases mediate opposing actions in the same cell type. Another conclusion is that different types of cancer cells respond differently to FFAR activation. Currently, the best-studied models are prostate, breast, and colon cancer. FFA1 and FFA4 agonists can inhibit proliferation and migration of prostate and breast cancer cells, but enhance growth of colon cancer cells. In contrast, FFA2 activation can in some cases inhibit proliferation of colon cancer cells. Although the available data are sometimes contradictory, there are several examples in which FFAR agonists inhibit proliferation of cancer cells. This is a unique response to GPCR activation that will benefit from a mechanistic explanation as the field progresses. The development of more selective FFAR agonists and antagonists, combined with gene knockout approaches, will be important for unraveling FFAR-mediated inhibitory effects. These inhibitory actions, mediated by druggable GPCRs, hold promise for cancer prevention and/or therapy.

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.

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.

Anticancer activities of pterostilbene-isothiocyanate conjugate in breast cancer cells: involvement of PPARγ

Trans-3,5-dimethoxy-4'-hydroxystilbene (PTER), a natural dimethylated analog of resveratrol, preferentially induces certain cancer cells to undergo apoptosis and could thus have a role in cancer chemoprevention. Peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear receptor superfamily, is a ligand-dependent transcription factor whose activation results in growth arrest and/or apoptosis in a variety of cancer cells. Here we investigated the potential of PTER-isothiocyanate (ITC) conjugate, a novel class of hybrid compound (PTER-ITC) synthesized by appending an ITC moiety to the PTER backbone, to induce apoptotic cell death in hormone-dependent (MCF-7) and -independent (MDA-MB-231) breast cancer cell lines and to elucidate PPARγ involvement in PTER-ITC action. Our results showed that when pre-treated with PPARγ antagonists or PPARγ siRNA, both breast cancer cell lines suppressed PTER-ITC-induced apoptosis, as determined by annexin V/propidium iodide staining and cleaved caspase-9 expression. Furthermore, PTER-ITC significantly increased PPARγ mRNA and protein levels in a dose-dependent manner and modulated expression of PPARγ-related genes in both breast cancer cell lines. This increase in PPARγ activity was prevented by a PPARγ-specific inhibitor, in support of our hypothesis that PTER-ITC can act as a PPARγ activator. PTER-ITC-mediated upregulation of PPARγ was counteracted by co-incubation with p38 MAPK or JNK inhibitors, suggesting involvement of these pathways in PTER-ITC action. Molecular docking analysis further suggested that PTER-ITC interacted with 5 polar and 8 non-polar residues within the PPARγ ligand-binding pocket, which are reported to be critical for its activity. Collectively, our observations suggest potential applications for PTER-ITC in breast cancer prevention and treatment through modulation of the PPARγ activation pathway.

Docosahexaenoic acid inhibited the Wnt/β-catenin pathway and suppressed breast cancer cells in vitro and in vivo

N-3 fatty acids (FAs) are essential FAs necessary for human health and are known to possess anticancer properties. However, the relationship between n-3 FAs and β-catenin, one of the key components of the Wnt signaling pathway, in mouse breast cancer remains poorly characterized. In this study, 4T1 mouse breast cancer cells were exposed to a representative n-3 FA, docosahexaenoic acid (DHA), to investigate the relationship between n-3 FAs and the Wnt/β-catenin signaling pathway in vivo and in vitro. In vitro studies showed that DHA strongly inhibited cell growth, and induced G1 cell cycle arrest both in 4T1 mouse breast cells and MCF-7 human breast cells. DHA reduced β-catenin expression and T cell factor/lymphoid-enhancing factor reporter activity in 4T1 mouse breast cells. In addition, DHA down-regulated the expression of downstream target genes such as c-myc and cyclinD1. In vivo, therapy experiments were conducted on Babl/c mice bearing breast cancer. We found that feeding mouse the 5% fish oil-supplemented diet for 30 days significantly reduced the growth of 4T1 mouse breast cancer in vivo through inhibition of cancer cell proliferation as well as induction of apoptosis. Feeding animals a 5% fish oil diet significantly induced down-regulation of β-catenin in tumor tissues with a notable increase in apoptosis. In addition, fish oil-supplemented diet decreased lung metastases of breast cancer. These observations suggested that DHA exerted its anticancer activity through down-regulation of Wnt/β-catenin signaling. Thus, our data call for further studies to assess the effectiveness of fish oil as a dietary supplement in the prevention and treatment of breast cancer.

Evolutionary foundations for cancer biology

New applications of evolutionary biology are transforming our understanding of cancer. The articles in this special issue provide many specific examples, such as microorganisms inducing cancers, the significance of within-tumor heterogeneity, and the possibility that lower dose chemotherapy may sometimes promote longer survival. Underlying these specific advances is a large-scale transformation, as cancer research incorporates evolutionary methods into its toolkit, and asks new evolutionary questions about why we are vulnerable to cancer. Evolution explains why cancer exists at all, how neoplasms grow, why cancer is remarkably rare, and why it occurs despite powerful cancer suppression mechanisms. Cancer exists because of somatic selection; mutations in somatic cells result in some dividing faster than others, in some cases generating neoplasms. Neoplasms grow, or do not, in complex cellular ecosystems. Cancer is relatively rare because of natural selection; our genomes were derived disproportionally from individuals with effective mechanisms for suppressing cancer. Cancer occurs nonetheless for the same six evolutionary reasons that explain why we remain vulnerable to other diseases. These four principles-cancers evolve by somatic selection, neoplasms grow in complex ecosystems, natural selection has shaped powerful cancer defenses, and the limitations of those defenses have evolutionary explanations-provide a foundation for understanding, preventing, and treating cancer.

β-Lactoglobulin as a molecular carrier of linoleate: characterization and effects on intestinal epithelial cells in vitro

The dairy protein β-lactoglobulin (βlg) is known to bind hydrophobic ligands such as fatty acids. In the present work, we investigated the biological activity in vitro of linoleate once complexed to bovine βlg. Binding of linoleate (C18:2) to bovine βlg was achieved by heating at 60 °C for 30 min at pH 7.4, resulting in a linoleate/βlg molar binding stoichiometry of 1.1, 2.1, and 3.4. Two types of binding sites were determined by ITC titrations. Binding of linoleate induced the formation of covalent dimers and trimers of βlg. The LD(50) on Caco-2 cells after 24 h was 58 μM linoleate. However, cell viability was unaffected when 200 μM linoleate was presented to the Caco-2 cells as part of the βlg complex. The Caco-2 cells did not increase mRNA transcript levels of long chain fatty acid transport genes, FATP4 and FABPpm, or increase levels of the cAMP signal, in response to the presence of 50 μM linoleate alone or as part of the βlg complex. Therefore, it is proposed that βlg can act as a molecular carrier and alter the bioaccessibility of linoleate/linoleic acid.

Effects of omega-3 fatty acids on progestin stimulation of invasive properties in breast cancer

Clinical studies have shown that progestins increase breast cancer risk in hormone replacement therapy, while we and others have previously reported that progestins stimulate invasive properties in progesterone receptor (PR)-rich human breast cancer cell lines. Based on others' reports that omega-3 fatty acids inhibit metastatic properties of breast cancer, we have reviewed the literature for possible connections between omega-3 fatty-acid-driven pathways and progestin-stimulated pathways in an attempt to suggest theoretical mechanisms for possible omega-3 fatty acid inhibition of progestin stimulation of breast cancer invasion. We also present some data suggesting that fatty acids regulate progestin stimulation of invasive properties in PR-rich T47D human breast cancer cells, and that an appropriate concentration of the omega-3 fatty acid eicosapentaenoic acid inhibits progestin stimulation of invasive properties. It is hoped that focus on the inter-relationship between pathways by which omega-3 fatty acids inhibit and progestins stimulate breast cancer invasive properties will lead to further in vitro, in vivo, and clinical studies testing the hypothesis that omega-3 fatty acids can inhibit progestin stimulation of invasive properties in breast cancer, and ameliorate harmful effects of progestins which occur in combined progestin-estrogen hormone replacement therapy.

Different effects of omega-3 fatty acids on the cell cycle in C2C12 myoblast proliferation

Polyunsaturated fatty acids (PUFAs) are important molecules for human health. We investigated the effects of three major omega-3 PUFAs on C2C12 myoblast proliferation. Both docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids decreased cell growth, whereas linolenic (ALA) acid did not, compared with the control. Cell cycle analysis showed that G(1) phase duration was increased markedly and S-phase duration was decreased by DHA and EPA. In contrast, there was no change in the G(1) or S-phase duration when the cells were treated with linolenic acid. To determine how DHA and EPA affected the cell cycle, cyclins and MAPK proteins were investigated. Western blotting and real-time quantitative PCR showed that DHA and EPA decreased cyclin E and CDK2 levels at both the protein and mRNA level. Also, MAPK phosphorylation levels were decreased by treatment with DHA and EPA. Our results indicated that different kinds of n-3 PUFA differentially affected myoblast cell proliferation. DHA and EPA decreased skeletal muscle cell proliferation through a mechanism involving MAPK-ERK.

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.

Bayesian hierarchical changepoint methods in modeling the tumor growth profiles in xenograft experiments

PURPOSE

The standard approach of using tumor doubling time to assess growth delay may not accurately represent tumor response, especially if the growth rates are not constant. Therefore, we developed a method to compare the antitumor activities of different treatments in xenograft experiments that uses the entire growth curve to estimate nonconstant growth rates.

EXPERIMENTAL DESIGN

A Bayesian hierarchical changepoint (BHC) method was used to model logarithmically transformed tumor volumes (TV). Each tumor was assumed to have a growth profile, represented by a prenadir regression rate, a regression period, a nadir volume, and a postnadir regrowth rate. Confidence intervals were calculated to compare these features between different treatments. We used data from a study assessing the effects of radiation, gemcitabine, and a Chk1/2 inhibitor on MiaPaCa-2 xenografts.

RESULTS

We found that the BHC model provided a good fit to the data and more descriptive features than the tumor doubling approach. This model detected significant tumor regression in the AZD7762 + 1 Gy and GEM + 1 Gy that was not detected when comparing the tumor doubling times. The BHC model also provided evidence that the growth inhibition resulted from a direct tumor effect rather than an indirect effect on the tumor bed, as evidenced by dramatic tumor regression in response to effective treatments and similar postnadir regrowth rates across all treatment groups.

CONCLUSIONS

Compared with the tumor doubling time approach, the BHC model utilizes all data, providing more descriptive features that address mechanisms underlying tumor growth inhibition and maximize the biological information obtained from tumor xenografts studies.

Role of dietary fatty acids in mammary gland development and breast cancer

Breast cancer is the most common cancer among women worldwide. Estimates suggest up to 35% of cases may be preventable through diet and lifestyle modification. Growing research on the role of fats in human health suggests that early exposure in life to specific fatty acids, when tissues are particularly sensitive to their environment, can have long-term health impacts. The present review examines the role of dietary fat in mammary gland development and breast cancer throughout the lifecycle. Overall, n-3 polyunsaturated fatty acids have promising cancer-preventive effects when introduced early in life, and warrant further research to elucidate the mechanisms of action.

The {omega}-3 fatty acid eicosapentaenoic acid elicits cAMP generation in colonic epithelial cells via a "store-operated" mechanism

Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid abundant in fish oil that exerts a wide spectrum of documented beneficial health effects in humans. Because dietary interventions are relatively inexpensive and are widely assumed to be safe, they have broad public appeal. Their endorsement can potentially have a major impact on human health, but hard mechanistic evidence that specifies how these derivatives work at the cellular level is limited. EPA (50 microM) caused a small elevation of cytoplasmic Ca(2+) concentration ([Ca(2+)]) in intact NCM460 human colonic epithelial cells as measured by fura 2 and a profound drop of [Ca(2+)] within the endoplasmic reticulum (ER) of permeabilized cells as monitored by compartmentalized mag-fura 2. Total internal reflection fluorescence microscopy showed that this loss of ER store [Ca(2+)] led to translocation of the ER-resident transmembrane Ca(2+) sensor STIM1. Using sensitive FRET-based sensors for cAMP in single cells, we further found that EPA caused a substantial increase in cellular cAMP concentration, a large fraction of which was dependent on the drop in ER [Ca(2+)], but independent of cytosolic Ca(2+). An additional component of the EPA-induced cAMP signal was sensitive to the phosphodiesterase inhibitor isobutyl methylxanthine. We conclude that EPA slowly releases ER Ca(2+) stores, resulting in the generation of cAMP. The elevated cAMP is apparently independent of classical G protein-coupled receptor activation and is likely the consequence of a newly described "store-operated" cAMP signaling pathway that is mediated by STIM1.

Docosahexaenoic acid induces apoptosis in MCF-7 cells in vitro and in vivo via reactive oxygen species formation and caspase 8 activation

Background

The present study sought to further investigate the in vitro and in vivo anticancer effects of a representative omega-3 fatty acid, docosahexaenoic acid (DHA), with a focus on assessing the induction of oxidative stress and apoptosis as an important mechanism for its anticancer actions.

Methodology/Principal Findings

In vitro studies showed that DHA strongly reduces the viability and DNA synthesis of MCF-7 human breast cancer cells in culture, and also promotes cell death via apoptosis. Mechanistically, accumulation of reactive oxygen species and activation of caspase 8 contribute critically to the induction of apoptotic cell death. Co-presence of antioxidants or selective inhibition or knockdown of caspase 8 each effectively abrogates the cytotoxic effect of DHA. Using athymic nude mice as an in vivo model, we found that feeding animals the 5% fish oil-supplemented diet for 6 weeks significantly reduces the growth of MCF-7 human breast cancer cells in vivo through inhibition of cancer cell proliferation as well as promotion of cell death. Using 3-nitrotyrosine as a parameter, we confirmed that the fish oil-supplemented diet significantly increases oxidative stress in tumor cells in vivo. Analysis of fatty acid content in plasma and tissues showed that feeding animals a 5% fish oil diet increases the levels of DHA and eicosapentaenoic acid in both normal and tumorous mammary tissues by 329% and 300%, respectively.

Conclusions/Significance

DHA can strongly induce apoptosis in human MCF-7 breast cancer cells both in vitro and in vivo. The induction of apoptosis in these cells is selectively mediated via caspase 8 activation. These observations call for further studies to assess the effectiveness of fish oil as a dietary supplement in the prevention and treatment of human breast cancer.

Effects of different dietary fatty acids on the fatty acid compositions and the expression of lipid metabolic-related genes in mammary tumor tissues of rats

In this study, the effects of dietary fatty acids on the fatty acid compositions and lipid metabolic-related genes expression in N-methyl-N-nitrosourea (MNU)-induced rat mammary carcinogenesis were evaluated. The 50-day-old female Sprague-Dawley rats were intervened by different dietary fats (15% wt/wt), including saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), n-6 polyunsaturated fatty acid (PUFA), n-3 PUFA, 1:1 n-6/n-3, 5:1 n-6/n-3, 10:1 n-6/n-3, and 1:2:1 S/M/P (1:1 n-6/n-3), alone or in combination with MNU. There was no mammary tumor occurrence in the control and MNU-treated n-3 PUFA groups after 18 wk. n-3 PUFA diet retarded the weight growth of rats. 1:1 n-6/n-3 diet significantly reduced the MNU-induced tumor incidence and tumor multiplicity compared with SFA, MUFA, n-6 PUFA, 5:1 n-6/n-3, 10:1 n-6/n-3 and 1:2:1 S/M/P diets (42.86% vs. 83.33%-92.31%, 0.79 vs. 2.62-2.85, P < 0.01). Additionally, 1:1 n-6/n-3 diet substantially increased cis-5,8,11,14,17-eicosapentaenoic acid and cis-4,7,10,13,16,19-docosahexaenoic acid levels, whereas it decreased C20:4 level and the mRNA expressions of fatty acid synthase, Cyclooxygenase-2 (COX-2), and 5-lipoxygenase (5-LOX) in mammary tissues (P < 0.05). These results suggest that 1:1 n-6/n-3 in the diet is effective in the prevention of mammary tumor development by increasing the n-3 PUFA content and reducing the expression of lipid metabolic-related genes.

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.

Eicosapentaenoic acid inhibits voltage-gated sodium channels and invasiveness in prostate cancer cells

BACKGROUND AND PURPOSE

The voltage-gated Na(+) channels (Na(v)) and their corresponding current (I(Na)) are involved in several cellular processes, crucial to metastasis of cancer cells. We investigated the effects of eicosapentaenoic (EPA), an omega-3 polyunsaturated fatty acid, on I(Na) and metastatic functions (cell proliferation, endocytosis and invasion) in human and rat prostate cancer cell lines (PC-3 and Mat-LyLu cells).

EXPERIMENTAL APPROACH

The whole-cell voltage clamp technique and conventional/quantitative real-time reverse transcriptase polymerase chain reaction analysis were used. The presence of Na(v) proteins was shown by immunohistochemical methods. Alterations in the fatty acid composition of phospholipids after treatment with EPA and metastatic functions were also examined.

KEY RESULTS

A transient inward Na(+) current (I(Na)), highly sensitive to tetrodotoxin, and Na(V) proteins were found in these cells. Expression of Na(V)1.6 and Na(V)1.7 transcripts (SCN8A and SCN9A) was predominant in PC-3 cells, while Na(V)1.7 transcript (SCN9A) was the major component in Mat-LyLu cells. Tetrodotoxin or synthetic small interfering RNA targeted for SCN8A and SCN9A inhibited metastatic functions (endocytosis and invasion), but failed to inhibit proliferation in PC-3 cells. Exposure to EPA produced a rapid and concentration-dependent suppression of I(Na). In cells chronically treated (up to 72h) with EPA, the EPA content of cell lipids increased time-dependently, while arachidonic acid content decreased. Treatment of PC-3 cells with EPA decreased levels of mRNA for SCN9A and SCN8A, cell proliferation, invasion and endocytosis.

CONCLUSION AND IMPLICATIONS

Treatment with EPA inhibited I(Na) directly and also indirectly, by down-regulation of Na(v) mRNA expression in prostate cancer cells, thus inhibiting their metastatic potential.

Unsaturated fatty acids promote proliferation via ERK1/2 and Akt pathway in bovine mammary epithelial cells

GPR40 has recently been identified as a G protein-coupled cell-surface receptor for long-chain fatty acids (LCFAs). The mRNA of the bovine ortholog of GPR40 (bGPR40) was detected by RT-PCR in cloned bovine mammary epithelial cells (bMEC) and in the bovine mammary gland at various stages of lactation. Oleate and linoleate caused an increase in intracellular Ca(2+) concentrations in these cells, and significantly reduced forskolin-induced cAMP concentrations. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and Akt kinase, which regulates cell proliferation and survival, was rapidly increased by oleate. Incubation with oleate and linoleate for 24h significantly promoted cell proliferation. Moreover, in serum-free medium, oleate significantly stimulated cell proliferation during a 7-day culture. These results suggest that bGPR40 mediates LCFA signaling in mammary epithelial cells and thereby plays an important role in cell proliferation and survival.

Dietary fish oil deactivates a growth-promoting signaling pathway in hepatoma 7288CTC in Buffalo rats

Dietary fish oil decreases growth of solid tumors in rodents. Mechanisms for this effect are not well defined. In rat hepatoma 7288CTC, short-term (1-2 h) treatment with eicosapentaenoic acid during perfusion in situ reduced fatty acid uptake and [(3)H]thymidine incorporation. To determine if dietary fish oil had this effect in vivo, 48 male Buffalo rats were implanted with tissue-isolated hepatoma 7288CTC and were divided into three groups: Diet I (8% olive oil/2% corn oil), Diet II (6% olive oil/2% corn oil/2% fish oil), or Diet III (3% olive oil/3% corn oil/4% fish oil). When tumors weighed 4 to 6 g rats were anesthetized and tumor fatty acid uptake and 13-hydroxyoctadecadienoic acid release were measured in vivo by arterial minus venous differences. Tumors were analyzed for cyclic adenosine monophosphate (cAMP), DNA content, and [(3)H]thymidine incorporation. Fish oil feeding significantly (P < 0.05) reduced tumor growth, cAMP content, fatty acid uptake, 13-hydroxyoctadecadienoic acid formation, DNA content, and [(3)H]thymidine incorporation. Addition of either pertussis toxin or 8-bromoadenosine-cAMP to the arterial blood reversed the inhibitions in tumors in rats fed diet II. These results provide in vivo evidence that dietary fish oil suppressed a specific linoleic acid-dependent, inhibitory G protein-coupled, growth-promoting signaling pathway in rat hepatoma 7288CTC.

Dietary factors and growth and metabolism in experimental tumors

Development of a diet that provides adequate nutrition and effective cancer prevention is an important goal in nutrition and cancer research. A confounding aspect of dietary control of tumor growth is the fact that some nutrients may up-regulate tumor growth, whereas other nutrients and nonnutrients down-regulate growth. Both up- and down-regulators may be present in the same foodstuff. Identification of these substances, determination of their mechanisms of action and potencies, as well as the interactions among the different mechanisms are topics of ongoing research. In this review, we describe results obtained in vivo or during perfusion in situ using solid tissue-isolated rodent tumors and human cancer xenografts in nude rats. Linoleic acid (LA), an essential n-6 polyunsaturated fatty acid (PUFA), was identified as an agent in dietary fat that is responsible for an up-regulation of tumor growth in vivo. Tumor LA uptake, mediated by high intratumor cAMP, stimulated formation of the mitogen, 13-hydroxyoctadecadienoic acid (13-HODE) and also increased ERK1/2 phosphorylation, [(3)H]thymidine incorporation and growth. A mechanism for control of this growth-promoting pathway was revealed during studies of the effects of dietary nutrients and nonnutrients known to inhibit tumor growth. These included four groups of lipophilic agents: n-3 fatty acids, melatonin, conjugated LA isomers and trans fatty acids. Each of these agents activated an inhibitory G protein-coupled receptor-mediated pathway that specifically suppressed tumor uptake of saturated, monounsaturated and n-6 PUFAs, thereby inhibiting an early step in the LA-dependent growth-promoting pathway.

Nutritional intervention with omega-3 fatty acids enhances tumor response to anti-neoplastic agents

Nutritional intervention with specific fatty acids depresses tumor growth and enhances tumor responsiveness to chemotherapy. Supplementation of tumors with long chained omega-3 polyunsaturated fatty acids results in enrichment of tumor phospholipid fractions with omega-3 fatty acids resulting in an altered membrane composition and function. Tumors enriched with long chained omega-3 polyunsaturated fatty acids possess membranes with increased fluidity, an elevated unsaturation index, enhanced transport capabilities that results in accumulation of selective anti-cancer agents, increased activity of selected drug activating enzymes, and alteration of signaling pathways important for cancer progression. These nutritionally induced changes in tumor fatty acid composition result in increased sensitivity to chemotherapy, especially in tumor lines that are resistant to chemotherapy and cause specific enhancement of cytotoxicity to tumor cells and protection of normal cells. Pre-disposing tumors to increased chemo-sensitivity through nutritional intervention with specific fatty acids has the potential to improve patient response to chemotherapy with fewer untoward side effects if these pre-clinical findings carry over into a clinical setting.

Effect of fish oil supplementation for 2 generations on changes in macrophage function induced by Walker 256 cancer cachexia in rats

The effect of coconut fat (rich in medium saturated fatty acids) or fish oil (rich in omega-3 polyunsaturated fatty acids) supplementation for 2 generations on tumor growth, cancer cachexia, animal survival and macrophage function was investigated in Walker 256 tumor-bearing rats. Female Wistar rats were supplemented with coconut fat or fish oil prior to mating and then throughout pregnancy and gestation. Both supplementations were daily and orally given at 1 g per kg body weight as a single bolus. Same treatment was performed by the 2 following generations. At 90 days of age, male offspring (50%) from F2 generation were subcutaneously inoculated with 2 x 10(7) Walker 256 tumor cells. At 14 days after tumor implantation, rats not supplemented displayed cancer cachexia characterized by loss of body weight, hypoglycemia, hyperlacticidemia, hypertriglyceridemia, decreased food intake and depletion of glycogen stores in the liver and skeletal muscles. Supplementation with coconut fat did not affect these parameters. However, supplementation with fish oil decreased tumor growth (59%), prevented body weight loss and food intake reduction and attenuated cancer cachexia. In addition, fish oil increased animal survival up to 20 days (from 25% in rats not supplemented to 67% in rats supplemented with fish oil) and improved macrophage function characterized by increased phagocytosis capacity and production of hydrogen peroxide and nitric oxide. These results suggest that fish oil supplementation for 2 generations improves macrophage function in association to reduced tumor growth and attenuated cancer cachexia, maintaining food intake and increasing animal survival.