Enhanced radiosensitivity of rat autochthonous mammary tumors by dietary docosahexaenoic acid

Cell-type specific anti-cancerous effects of nitro-oleic acid and its combination with gamma irradiation

Nitro-fatty acids (NFAs) are endogenous lipid mediators capable of post-translational modifications of selected regulatory proteins. Here, we investigated the anti-cancerous effects of nitro-oleic acid (NO2OA) and its combination with gamma irradiation on different cancer cell lines. The effects of NO2OA on cell death, cell cycle distribution, or expression of p21 and cyclin D1 proteins were analyzed in cancer (A-549, HT-29 and FaDu) or normal cell lines (HGF, HFF-1). Dose enhancement ratio at 50 % survival fraction (DERIC50) was calculated for samples pre-treated with NO2OA followed by gamma irradiation. NO2OA suppressed viability and induced apoptotic cell death. These effects were cell line specific but not in general selective for cancer cells. HT-29 cell line exerted higher sensitivity toward NO2OA treatment among cancer cell lines tested: induction of cell cycle arrest in the G2/M phase was associated with an increase in p21 and a decrease in cyclin D1 expression. Pre-treatment of HT-29 cells with NO2OA prior irradiation showed a significantly increased DERIC50, demonstrating radiosensitizing effects. In conclusion, NO2OA exhibited potential for combined chemoradiotherapy. Our results encourage the development of new NFAs with improved features for cancer chemoradiation.

Plasma free fatty acid levels in cervical cancer: concurrent chemoradiotherapy improves abnormal profile

Background: Epidemiology has demonstrated that plasma free fatty acids (FFAs) can prevent the development of cancer. Our study sought to evaluate the relationship between plasma (FFA) levels and cervical cancer. Methods: In recent years, metabolomics-based approaches have been recognized as an emerging tool, so we examined the plasma FFA profiles of 114 patients with cervical cancer and 151 healthy people using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Results: The data results were analyzed by multifactorial binary logistic regression analysis, and it was found that palmitic acid, docosahexaenoic acid (DHA), and total ω-3 fatty acids were negatively correlated with the risk of cervical cancer; whereas tetracosanoic acid was positively correlated with the risk of cervical cancer (OR, 1.026; 95% CI, 1.013-1.040; p < 0.001). Dynamic follow-up of 40 cervical cancer patients who successfully completed CCRT revealed that most fatty acid levels tended to increase after the end of treatment, except for palmitic and stearic acid levels, which were lower than before treatment. Conclusion: Plasma FFA profiles were altered in cervical cancer patients, which may be related to abnormal fatty acid metabolism in cervical cancer. The described changes in fatty acid profiles during CCRT may be related to the good functioning of CCRT. Further studies on plasma FFA composition and its changes due to CCRT in patients with cervical cancer are warranted.

Pronounced Enhancement in Radiosensitization of Esophagus Cancer Cultivated in Docosahexaenoic Acid via the PPAR -γ Activation

Docosahexaenoic acid (DHA) has been reported to suppress the tumor growth and improve prognosis and has been used to cooperate with many other chemotherapy medicines. Up to now, surveys focused on the Interaction between DHA and radiation are relatively modest. Our study sought to evaluate the radiosensitivity changes caused by DHA on esophageal cancer cells. We selected TE-1 and TE-10 esophagus cancer cells as models and performed routine cell proliferation assay and cloning assay to detect the impact of DHA combined with X-ray. We used cell cycle assay, lipid peroxidation assay, comet assay, and apoptosis assay to unearth the potential causes. We also launched a mouse transplanted tumor experiment to verify the synergetic effect of DHA and irradiation. Finally, a western blot assay was used to find a novel mechanism. As a result, DHA improved TE-1 and TE-10 radiosensitivity in vivo and in vitro. What's more, PPAR-γ expression increased due to the DHA supplement. Inhibiting PPAR-γ could attenuate benefits brought out by DHA somehow. Due to its explicit usage and convenience, DHA would serve as an adjuvant therapy before radiotherapy if the clinical trials indicated positive.

Metabolic Rewiring in Radiation Oncology Toward Improving the Therapeutic Ratio

To meet the anabolic demands of the proliferative potential of tumor cells, malignant cells tend to rewire their metabolic pathways. Although different types of malignant cells share this phenomenon, there is a large intracellular variability how these metabolic patterns are altered. Fortunately, differences in metabolic patterns between normal tissue and malignant cells can be exploited to increase the therapeutic ratio. Modulation of cellular metabolism to improve treatment outcome is an emerging field proposing a variety of promising strategies in primary tumor and metastatic lesion treatment. These strategies, capable of either sensitizing or protecting tissues, target either tumor or normal tissue and are often focused on modulating of tissue oxygenation, hypoxia-inducible factor (HIF) stabilization, glucose metabolism, mitochondrial function and the redox balance. Several compounds or therapies are still in under (pre-)clinical development, while others are already used in clinical practice. Here, we describe different strategies from bench to bedside to optimize the therapeutic ratio through modulation of the cellular metabolism. This review gives an overview of the current state on development and the mechanism of action of modulators affecting cellular metabolism with the aim to improve the radiotherapy response on tumors or to protect the normal tissue and therefore contribute to an improved therapeutic ratio.

Radioprotective Agents and Enhancers Factors. Preventive and Therapeutic Strategies for Oxidative Induced Radiotherapy Damages in Hematological Malignancies

Radiation therapy plays a critical role in the management of a wide range of hematologic malignancies. It is well known that the post-irradiation damages both in the bone marrow and in other organs are the main causes of post-irradiation morbidity and mortality. Tumor control without producing extensive damage to the surrounding normal cells, through the use of radioprotectors, is of special clinical relevance in radiotherapy. An increasing amount of data is helping to clarify the role of oxidative stress in toxicity and therapy response. Radioprotective agents are substances that moderate the oxidative effects of radiation on healthy normal tissues while preserving the sensitivity to radiation damage in tumor cells. As well as the substances capable of carrying out a protective action against the oxidative damage caused by radiotherapy, other substances have been identified as possible enhancers of the radiotherapy and cytotoxic activity via an oxidative effect. The purpose of this review was to examine the data in the literature on the possible use of old and new substances to increase the efficacy of radiation treatment in hematological diseases and to reduce the harmful effects of the treatment.

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.

Cancer diets for cancer patients: Lessons from mouse studies and new insights from the study of fatty acid metabolism in tumors

Specific diets for cancer patients have the potential to offer an adjuvant modality to conventional anticancer therapy. If the concept of starving cancer cells from nutrients to inhibit tumor growth is quite simple, the translation into the clinics is not straightforward. Several diets have been described including the Calorie-restricted diet based on a reduction in carbohydrate intake and the Ketogenic diet wherein the low carbohydrate content is compensated by a high fat intake. As for other diets that deviate from normal composition only by one or two amino acids, these diets most often revealed a reduction in tumor growth in mice, in particular when associated with chemo- or radiotherapy. By contrast, in cancer patients, the interest of these diets is almost exclusively supported by case reports precluding any conclusions on their real capacity to influence disease outcome. In parallel, the field of tumor lipid metabolism has emerged in the last decade offering a better understanding of how fatty acids are captured, synthesized or stored as lipid droplets in cancers. Fatty acids participate to cancer cell survival in the hypoxic and acidic tumor microenvironment and also support proliferation and invasiveness. Interestingly, while such addiction for fatty acids may account for cancer progression associated with high fat diet, it could also represent an Achilles heel for tumors. In particular n-3 polyunsaturated fatty acids represent a class of lipids that can exert potent cytotoxic effects in tumors and therefore represent an attractive diet supplementation to improve cancer patient outcomes.

Emerging strategies to target cancer metabolism and improve radiation therapy outcomes

Cancer-specific metabolic changes support the anabolic needs of the rapidly growing tumor, maintain a favorable redox balance, and help cells adapt to microenvironmental stresses like hypoxia and nutrient deprivation. Radiation is extensively applied in a large number of cancer treatment protocols but despite its curative potential, radiation resistance and treatment failures pose a serious problem. Metabolic control of DNA integrity and genomic stability can occur through multiple processes, encompassing cell cycle regulation, nucleotide synthesis, epigenetic regulation of gene activity, and antioxidant defenses. Given the important role of metabolic pathways in oxidative damage responses, it is necessary to assess the potential for tumor-specific radiosensitization by novel metabolism-targeted therapies. Additionally, there are opportunities to identify molecular and functional biomarkers of vulnerabilities to combination treatments, which could then inform clinical decisions. Here, we present a curated list of metabolic pathways in the context of ionizing radiation responses. Glutamine metabolism influences DNA damage responses by mechanisms such as synthesis of nucleotides for DNA repair or of glutathione for ROS detoxification. Repurposed oxygen consumption inhibitors have shown promising radiosensitizing activity against murine model tumors and are now in clinical trials. Production of 2-hydroxy glutarate by isocitrate dehydrogenase1/2 neomorphic oncogenic mutants interferes with the function of α-ketoglutarate-dependent enzymes and modulates Ataxia Telangiectasia Mutated (ATM) signaling and glutathione pools. Radiation-induced oxidative damage to membrane phospholipids promotes ferroptotic cell loss and cooperates with immunotherapies to improve tumor control. In summary, there are opportunities to enhance the efficacy of radiotherapy by exploiting cell-inherent vulnerabilities and dynamic microenvironmental components of the tumor.

Effects of cotreatment with omega-3 polyunsaturated fatty acids and anticancer agents on oxidative stress parameters: a systematic review of in vitro, animal, and human studies

Context

Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid and eicosapentaenoic acid, demonstrate possible beneficial effects as adjuvants in cancer treatment. One mechanism seems to be related to alterations in the redox status of cancer cells. Such alterations are thought to act in synergy with conventional anticancer agents.

Objective

This review examines published data on the effects of cotreatment with anticancer agents and n-3 PUFAS on oxidative stress parameters to determine whether any patterns of oxidative stress alterations can be identified.

Data Sources

A systematic search of MEDLINE (via PubMed) was conducted to identify articles published in English, Spanish, or Portuguese until November 2017.

Study Selection

The following inclusion criteria were applied: (1) individuals or animals with cancer or malignant cell lines supplemented with some source of n-3 PUFAs; (2) concomitant use of anticancer treatment; and (3) evaluation of oxidative stress-related variables.

Data Extraction

A standardized outline was used to extract the following data: study type, supplement used, type of cells, tumor or patient characteristics, study design, anticancer treatment used, and oxidative stress-related outcomes.

Results

After the literature search and screening of 1563 citations, 28 studies were included for data extraction and evaluation: 16 in vitro studies (2 of which also used in vivo studies), 8 animal studies, and 4 human studies (3 clinical trials and 1 case series). In most in vitro and animal studies, intervention groups receiving cotreatment with n-3 PUFAs showed enhanced lipid peroxidation and cytotoxicity compared with groups receiving anticancer treatment alone. Eleven of the 12 studies that investigated the effect of vitamin E on the sensitivity of cancer cells to the oxidative stress caused by n-3 PUFAs showed that vitamin E abolished the positive effects of cotreatment.

Conclusions

Alterations in oxidative stress caused by cotreatment with anticancer agents and n-3 PUFAs can exert positive effects on the efficacy of conventional treatment. This seems to occur in most cells and tumors tested thus far, but not all. Identifying tumors that are sensitive to these oxidative effects may provide support for the rational use of n-3 PUFAs as an adjuvant treatment in specific types of cancer.

ω-3 Long Chain Polyunsaturated Fatty Acids as Sensitizing Agents and Multidrug Resistance Revertants in Cancer Therapy

Chemotherapy efficacy is strictly limited by the resistance of cancer cells. The ω-3 long chain polyunsaturated fatty acids (ω-3 LCPUFAs) are considered chemosensitizing agents and revertants of multidrug resistance by pleiotropic, but not still well elucidated, mechanisms. Nowadays, it is accepted that alteration in gene expression, modulation of cellular proliferation and differentiation, induction of apoptosis, generation of reactive oxygen species, and lipid peroxidation are involved in ω-3 LCPUFA chemosensitizing effects. A crucial mechanism in the control of cell drug uptake and efflux is related to ω-3 LCPUFA influence on membrane lipid composition. The incorporation of docosahexaenoic acid in the lipid rafts produces significant changes in their physical-chemical properties affecting content and functions of transmembrane proteins, such as growth factors, receptors and ATP-binding cassette transporters. Of note, ω-3 LCPUFAs often alter the lipid compositions more in chemoresistant cells than in chemosensitive cells, suggesting a potential adjuvant role in the treatment of drug resistant cancers.

How plausible is the use of dietary n-3 PUFA in the adjuvant therapy of cancer?

Considerable debate exists regarding the potential antineoplastic effect of dietary long-chain n-3 PUFA contained in fatty fishes. Since the majority of published data has proven that their intake does not induce toxic or carcinogenic effects in humans, their possible preventive use against cancer has been suggested. On the other hand, it is unlikely that they could be effective in cancer patients as a single therapy. Nevertheless, a considerable effort has been put forth in recent years to evaluate the hypothesis that n-3 PUFA might improve the antineoplastic efficiency of currently used anticancer agents. The rationale for this therapeutic combinatory strategy is trying to increase cancer sensitivity to conventional therapies. This could allow the use of lower drug/radiation doses and, thereby, a reduction in the detrimental health effects associated with these treatments. We will here critically examine the studies that have investigated this possibility, by focusing particularly on the biological and molecular mechanisms underlying the antineoplastic effect of these combined treatments. A possible use of n-3 PUFA in combination with the innovative single-targeted anti-cancer therapies, that often are not completely devoid of dangerous side-effects, is also suggested.

Lipidomic analysis reveals a radiosensitizing role of gamma-linolenic acid in glioma cells

Previous studies have demonstrated that gamma-linolenic acid (GLA) is effective against glioma cells under both in vitro and in vivo conditions. In the present study we determined how GLA alone or in combination with irradiation alters the fatty acid (FA) and lipid profiles, the lipid droplet (LD) content, the lipid biosynthetic gene expression and the apoptosis of glioma cells. In GLA-treated cells direct correlations were found between the levels of various FAs and the expression of the corresponding FA biosynthetic genes. The total levels of saturated and monosaturated FAs decreased in concert with the down-regulation of FASN and SCD1 gene expression. Similarly, decreased FADS1 gene expression was paralleled by lowered arachidonic acid (20:4 n-6) and eicosapentaenoic acid (20:5 n-3) contents, while the down-regulation of FADS2 expression was accompanied by a diminished docosahexaenoic acid (22:6 n-3) content. Detailed mass spectrometric analyses revealed that individual treatments gave rise to distinct lipidomic fingerprints. Following uptake, GLA was subjected to elongation, resulting in dihomo-gamma-linolenic acid (20:3 n-6, DGLA), which was used for the synthesis of the LD constituent triacylglycerols and cholesteryl esters. Accordingly, an increased number of LDs were observed in response to GLA administration after irradiation. GLA increased the radioresponsiveness of U87 MG cells, as demonstrated by an increase in the number of apoptotic cells determined by FACS analysis. In conclusion, treatment with GLA increased the apoptosis of irradiated glioma cells, and GLA might therefore increase the therapeutic efficacy of irradiation in the treatment of gliomas.

Combination of unsaturated fatty acids and ionizing radiation on human glioma cells: cellular, biochemical and gene expression analysis

Background

Based on previous observations a potential resort in the therapy of the particularly radioresistant glioma would be its treatment with unsaturated fatty acids (UFAs) combined with irradiation.

Methods

We evaluated the effect of different UFAs (arachidonic acid (AA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and oleic acid (OA)) on human U87 MG glioma cell line by classical biochemical end-point assays, impedance-based, real-time cellular and holographic microscopic analysis. We further analyzed AA, DHA, and GLA at morphological, gene and miRNA expression level.

Results

Corresponding to LDH-, MTS assays and real-time cytoxicity profiles AA, DHA, and GLA enhanced the radio sensitivity of glioma cells. The collective application of polyunsaturated fatty acids (PUFAs) and irradiation significantly changed the expression of EGR1, TNF-α, NOTCH1, c-MYC, TP53, HMOX1, AKR1C1, NQO1, while up-regulation of GADD45A, EGR1, GRP78, DDIT3, c-MYC, FOSL1 were recorded both in response to PUFA treatment or irradiation alone. Among the analyzed miRNAs miR-146 and miR-181a were induced by DHA treatment. Overexpression of miR-146 was also detected by combined treatment of GLA and irradiation.

Conclusions

Because PUFAs increased the radio responsiveness of glioma cells as assessed by biochemical and cellular assays, they might increase the therapeutic efficacy of radiation in treatment of gliomas. We demonstrated that treatment with DHA, AA and GLA as adjunct to irradiation up-regulated the expression of oxidative-stress and endoplasmic reticulum stress related genes, and affected NOTCH1 expression, which could explain their additive effects.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-142) contains supplementary material, which is available to authorized users.

Current evidence linking polyunsaturated Fatty acids with cancer risk and progression

There is increasing evidence that polyunsaturated fatty acids (PUFAs) play a role in cancer risk and progression. The n-3 family of PUFAs includes alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) while the n-6 family includes linolenic acid (LA) and arachidonic acid (AA). EPA and DHA are precursors for anti-inflammatory lipid mediators while AA is a precursor for pro-inflammatory lipid mediators. Collectively, PUFAs play crucial roles in maintaining cellular homeostasis, and perturbations in dietary intake or PUFA metabolism could result in cellular dysfunction and contribute to cancer risk and progression. Epidemiologic studies provide an inconsistent picture of the associations between dietary PUFAs and cancer. This discrepancy may reflect the difficulties in collecting accurate dietary data; however, it also may reflect genetic variation in PUFA metabolism which has been shown to modify physiological levels of PUFAs and cancer risk. Also, host-specific mutations as a result of cellular transformation could modify metabolism of PUFAs in the target-tissue. Clinical trials have shown that supplementation with PUFAs or foods high in PUFAs can affect markers of inflammation, immune function, tumor biology, and prognosis. Pre-clinical investigations have begun to elucidate how PUFAs may mediate cell proliferation, apoptosis and angiogenesis, and the signaling pathways involved in these processes. The purpose of this review is to summarize the current evidence linking PUFAs and their metabolites with cancer and the molecular mechanisms that underlie this association. Identifying the molecular mechanism(s) through which PUFAs affect cancer risk and progression will provide an opportunity to pursue focused dietary interventions that could translate into the development of personalized diets for cancer control.

Interaction of ω-3 polyunsaturated fatty acids with radiation therapy in two different colorectal cancer cell lines

BACKGROUND & AIMS

This study aims at evaluating if docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) increases the efficacy of radiation therapy (RT) on two human colorectal cancer cell lines with different radio-sensitivity.

METHODS

LS174T and HT-29 cells were treated with 20 or 50 μmol/L EPA or DHA followed by single X-ray RT of 0, 2 or 4 Gy, to evaluate cell survival, apoptosis, peroxide and malondialdehyde productions. Inflammation- and apoptosis-related proteins were analyzed by Western Blot. ANOVAs were used for statistical analysis.

RESULTS

LS174T was more sensitive to RT than HT-29. DHA and to a lesser extent EPA increased cell death, apoptosis and peroxide production after RT in LS174T and to a lesser extent in HT-29 (p < 0.05). This was associated with increased expression of heat shock protein 70, decreased expression of NF-kB p65, COX-2 and Bcl-2 proteins.

CONCLUSIONS

The effect of RT combination with DHA and to a lesser extent EPA was synergistic in the radio-sensitive LS174T cells, but additive in the radio-resistant HT-29 cells. This enhanced cytotoxicity was provoked at least partly by lipid peroxidation, which consequently modulated inflammatory response and induced apoptosis.

Reducing endothelial NOS activation and interstitial fluid pressure with n-3 PUFA offset tumor chemoresistance

The aim of this study was to determine how n-3 polyunsaturated fatty acid (PUFAs) counteracted tumor chemoresistance by restoring a functional vascularization. Rats with chemically induced mammary tumors were divided into two nutritional groups: a control group and a group fed with an n-3 PUFA-enriched diet. Both groups were treated with docetaxel. Functional vascular parameters (ultrasounds, interstitial fluid pressure) were determined for both nutritional groups before (W(0)) and during docetaxel treatment [every 2 h up to 1 week (W(+1)) for interstitial fluid pressure, at W(+1) for Evans blue extravasation and at W(+2) and W(+6) for ultrasounds]. In vitro n-3 PUFA-induced changes in endothelial cell migration, permeability and phosphorylation of endothelial nitric oxide synthase were evaluated using human umbilical vein endothelial cells. Whereas docetaxel stabilized tumor growth in the rat control group, it induced a 50% tumor regression in the n-3 PUFA group. Ultrasounds parameters were consistently lower in the n-3 PUFA group at all time points measured, down to ∼50% at W(+6). A single dose of docetaxel in the n-3 PUFA group markedly reduced interstitial fluid pressure from 2 h after injection up to W(+1) when Evans blue extravasation was increased by 3-fold. A decreased activation of endothelial nitric oxide synthase in tumors of the n-3 PUFA group, and in human umbilical vein endothelial cell cultured with n-3 PUFA, points toward a PUFA-induced disruption of nitric oxide signaling pathway. This normalization of tumor vasculature functions under n-3 PUFA diet indicates that such a supplementation, by improving drug delivery in mammary tumors, could be a complementary clinical strategy to decrease anticancer drug resistance.

Docosahexaenoic acid: a natural powerful adjuvant that improves efficacy for anticancer treatment with no adverse effects

Epidemiological studies have linked fish oil consumption to a decreased incidence of cancer. The anticancer effects of fish oil are mostly attributed to its content of omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, DHA, because of its unique effect of altering membrane composition, is often regarded as the major omega-3 fatty acid involved in anticancer activity. Although use of DHA as an anticancer drug to prevent or treat human cancer in clinical settings has not yet been well established, recent studies suggest that DHA can be very effective as an adjuvant with other anticancer agents. In this article, we present studies that show the role of DHA in improving anticancer drug efficacy. Several in vitro and animal studies suggest that combining DHA with other anticancer agents often improves efficacy of anticancer drugs and also reduces therapy-associated side effects. Incorporation of DHA in cellular membranes improves drug uptake, whereas increased lipid peroxidation is another mechanism for DHA-mediated enhanced efficacy of anticancer drugs. In addition, several intracellular targets including cyclooxygenase-2, nuclear factor kappa B, peroxisome proliferator-activated receptor gamma, mitogen-activated protein kinase, AKT, and BCL-2/BAX are found to play an important role in DHA-mediated additive or synergistic interaction with anticancer drugs. The data suggest that DHA is a safe, natural compound that can greatly improve the anticancer properties of anticancer drugs. Use of DHA with anticancer treatments provides an avenue to therapeutic improvement that involves less risk or side effects for patients and reduced regulatory burden for implementation.

The n3-polyunsaturated fatty acid docosahexaenoic acid induces immunogenic cell death in human cancer cell lines via pre-apoptotic calreticulin exposure

Some anticancer chemotherapeutics, such as anthracyclines and oxaliplatin, elicit immunogenic apoptosis, meaning that dying cancer cells are engulfed by dendritic cells and tumor antigens are efficiently presented to CD8+ T cells, which control residual tumor cells. Immunogenic apoptosis is characterized by pre-apoptotic cell surface exposure of calreticulin (CRT), which usually resides into the endoplasmic reticulum. We investigated the ability of the n3-polyunsaturated fatty acid docosahexaenoic acid (22:6n3, DHA) to induce pre-apoptotic CRT exposure on the surface of the human PaCa-44 pancreatic and EJ bladder cancer cell lines. Cells were treated with 150 μM DHA for different time periods, and, by immunoblot and immunofluorescence, we showed that DHA induced CRT exposure, before the apoptosis-associated phosphatidylserine exposure. As for the known immunogenic compounds, CRT exposure was inhibited by the antioxidant GSH, the pan-caspase zVAD-FMK, and caspase-8 IETD-FMK inhibitor. We provide the first evidence that DHA induces CRT exposure, representing thus a novel potential anticancer immunogenic chemotherapeutic agent.

Dietary n-3 polyunsaturated fatty acids and the paradox of their health benefits and potential harmful effects

There is some evidence to support the toxicity of polyunsaturated fatty acids (PUFAs) and their oxidative products, suggesting their involvement in the pathogenesis of different chronic diseases, including cancer. It has been shown that products of PUFA oxidation may exert a carcinogenic action by forming mutagenic adducts with DNA. However, a large amount of evidence accumulated over several decades has indicated the beneficial effects of administration of n-3 PUFAs in the prevention and therapy of a series of diseases. In particular, there is much evidence that n-3 PUFAs exert anti-inflammatory and antineoplastic effects, whereas n-6 PUFAs promote inflammation and carcinogenesis. In our tissues, both of the two classes of PUFAs can be converted into bioactive products, incorporated into membrane phospholipids or bound to membrane receptors, where they may alter, often in opposite ways, transduction pathways and affect important biological processes, such as cell death and survival, inflammation, and neo-angiogenesis. In the present review, we intend to shed light on the paradox of the coexisting healthy and toxic effects of n-3 PUFAs, focusing on their possible pro-oxidant cytotoxic and carcinogenic effect, in order to understand if their increased intake, recommended by a number of health agencies worldwide and promoted by nutraceutical producers, may or may not represent a hazard to human health.

Determinants of DHA incorporation into tumor tissue during dietary DHA supplementation

Docosahexaenoic acid (DHA), upon incorporation into tumor tissue, has the potential to sensitize tumors to the effects of chemotherapy or radiation therapy. Although DHA has usually been supplied to tumor tissue in the diet, appropriate dietary conditions required to obtain optimal tumor levels have not been established. Hence, we studied mammary tumor tissue responses in rats fed various durations and doses of DHA. Rats fed a palm oil enriched diet (diet 0) were switched to diets providing either 0.8 g DHA/day (diet 1) or 1.5 g DHA/day (diet 2). Tumor tissue fatty acid composition was analysed at baseline (diet 0), at weeks 1, 4 and 9 during diet 1 and at week 4 during diet 2. Dietary DHA supplementation differentially increased DHA within phospholipids (PL) and triacylglycerol (TAG) fractions in tumors. DHA level equilibrated between 2 and 4 weeks in PL while DHA increase was more progressive in TAG and did not reach a steady state. A higher dose of DHA further increased DHA content in tumor PL and TAG (P = 0.018 and P < 0.001, respectively). DHA concentration in plasma PL was positively correlated with DHA in tumor PL (r = 0.72; P = 0.0003) and TAG (r = 0.64; P = 0.003). We conclude that dietary DHA supplementation enhances tumor content of DHA in a time- and dose-dependent manner, and that the DHA level in plasma PL could be used as a proxy for tumor DHA. These findings have implications for dietary DHA supplementations in cancer patients.

RBC and WBC fatty acid composition following consumption of an omega 3 supplement: lessons for future clinical trials

Background

Results from increasing numbers of in vitro and in vivo studies have demonstrated that omega 3 fatty acids incorporated in cell culture media or in the diet of the animals can suppress the growth of cancers. When human clinical trials are initiated to determine the ability of omega 3 fatty acids to alter growth or response to chemotherapeutic interventions of cancers, it will be essential to determine the omega 3 intake of individuals in the trial to determine compliance with consumption of the supplement and to correlate with endpoints of efficacy. We wondered if the fatty acid composition of RBCs might accurately indicate incorporation of omega 3 fatty acids in the WBCs. In this report we determine and compare the changes in fatty acid compositions of red blood cells and white blood cells in response to consumption of three doses of an omega 3 fatty acid supplement.

Results

We found that the fraction of omega 3 fatty acids in both red blood cells and white blood cells increased following consumption of the supplement. There was a linear, dose responsive increase in the fraction of omega 3 fatty acids in red blood cells but the increase in omega 3 in white blood cells was not linear. The magnitude of increase in omega 3 fatty acids was different between the two cell types.

Conclusions

Fatty acid analysis of red blood cells is a good measure of compliance with supplement consumption. However, fatty acid analysis of white blood cells is needed to correlate changes in fatty acid composition of white blood cells with other biochemical changes in the white blood cells.

Trial Registration

ClinicalTrials.gov NCT00899353.

Improving outcome of chemotherapy of metastatic breast cancer by docosahexaenoic acid: a phase II trial

BACKGROUND

Breast cancer becomes lethal when visceral metastases develop. At this stage, anti-cancer treatments aim at relieving symptoms and delaying death without resulting in additional toxicity. On the basis of their differential anti-oxidant defence level, tumour cells can be made more sensitive to chemotherapy than non-tumour cells when membrane lipids are enriched with docosahexaenoic acid (DHA), a peroxidisable and oxidative-stress-inducing lipid of marine origin.

METHODS

This open-label single-arm phase II study evaluated the safety and efficacy (response rate), as primary end points, of the addition of 1.8 g DHA daily to an anthracycline-based chemotherapy (FEC) regimen in breast cancer patients (n = 25) with rapidly progressing visceral metastases. The secondary end points were time to progression (TTP) and overall survival (OS).

RESULTS

The objective response rate was 44%. With a mean follow-up time of 31 months (range 2-96 months), the median TTP was 6 months. Median OS was 22 months and reached 34 months in the sub-population of patients (n = 12) with the highest plasma DHA incorporation. The most common grade 3 or 4 toxicity was neutropaenia (80%).

CONCLUSION

DHA during chemotherapy was devoid of adverse side effects and can improve the outcome of chemotherapy when highly incorporated. DHA has a potential to specifically chemosensitise tumours.

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

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

The lipidome as a composite biomarker of the modifiable part of the risk of breast cancer

The potential for dietary fat to prevent breast cancer makes identification of defined molecules a mandatory step. In order to circumvent the limitations and/or bias of dietary exposure assessment tools, we have used the fatty acid composition of white adipose tissue as biomarker of past lipid intake. When considered separately, candidate fatty acids identified as favourable on the basis of their association with breast cancer risk have usually led to inconsistent results in dietary intervention studies carried out in rats. This inconsistency indicates that any approach based on a single fatty acid should be abandoned for an integrated view over the complex lipid interactions, which finally determines the lipidome, the lipid profile that is found in individuals. We reappraised the role of the complete lipid profile through a comprehensive study of adipose tissue fatty acids obtained in patients with benign or malignant breast tumors. Rather than a single fatty acid, a composite indicator combining elevated monounsaturates and low n-6/n-3 fatty acid ratio was associated with decreased breast cancer risk. The lipidome may provide the opportunity to quantify the modifiable part of the risk of breast cancer. The lipidome may be used as a template for designing proper dietary modifications in order to delay the occurrence of breast cancer. Which dietary modifications should be undertaken in order to bring a pertinent change to the lipidome with respect to the risk of breast cancer is currently unknown. The lipidome may allow the individualization of a high risk population of women, who may be targeted for a dietary prevention of breast cancer. The setting and validation of a high-throughput lipidomic station with analytical capabilities fitted to the need of mass screening is required. These two locks must be resolved before a primary prevention of breast cancer by diet could be contemplated.

Sensitization by docosahexaenoic acid (DHA) of breast cancer cells to anthracyclines through loss of glutathione peroxidase (GPx1) response

Docosahexaenoic acid (DHA, a lipid of marine origin) has been found to enhance the activity of several anticancer drugs through an oxidative mechanism. To examine the relation between chemosensitization by DHA and tumor cells antioxidant status, we used two breast cancer cell lines: MDA-MB-231, in which DHA increases sensitivity to doxorubicin, and MCF-7, which does not respond to DHA. Under these conditions, reactive oxygen species (ROS) level increased on anthracycline treatment only in MDA-MB-231. This was concomitant with a decreased cytosolic glutathione peroxidase (GPx1) activity, a crucial enzyme for protection against hydrogen and lipid peroxides, while major antioxidant enzyme activities increased in both cell lines in response to ROS. GPx-decreased activity was accompanied by an accumulation of glutathione, the GPx cosubstrate, and resulted from a decreased amount of GPx protein. In rat mammary tumors, when a DHA dietary supplementation led to an increased tumor sensitivity to anthracyclines, GPx1 activity was similarly decreased. Furthermore, vitamin E abolished both DHA effects on chemotherapy efficacy enhancement and on GPx1 inhibition. Thus, loss of GPx response to an oxidative stress in transformed cells may account for the ability of peroxidizable targets such as DHA to enhance tumor sensitivity to ROS-generating anticancer drugs.

Colon cancer therapy: new perspectives of nutritional manipulations using polyunsaturated fatty acids

PURPOSE OF REVIEW

Recent advances in the development of new therapeutic strategies combining conventional adjuvant radio/chemotherapy with nutritional manipulations with n-3 polyunsaturated fatty acids (PUFAs) are presented.

RECENT FINDINGS

Studies in cell culture and tumour-bearing animals have reported the ability of long-chain n-3 PUFAs to enhance the cytotoxicity of several anticancer drugs. In colon cancer, combination of n-3 PUFAs with 5-fluorouracil resulted in an additive growth inhibitory effect on different cell lines. Moreover, recent findings suggest that eicosapentaenoic or docosahexaenoic acid may be used to enhance tumour radiosensitivity while reducing mucosal/epidermal radiotoxicity similar to radioprotective agents. The underlying mechanism is probably mediated through lipid peroxidation because the antitumour effect of n-3 PUFAs is shared with the n-6 PUFA, arachidonic acid, and abolished by vitamin E. In vivo, the use of n-3 PUFAs may provide an additional advantage compared with n-6 PUFAs. Downregulation of eicosanoid synthesis from cyclooxygenase II may reduce angiogenesis, inflammation and metastasis induction.

SUMMARY

New insights suggest that n-3 PUFAs may play an important role not only in cancer prevention but also in cancer management. They may act synergistically with radio/chemotherapy to kill tumour cells by increasing oxidative stress while reducing angiogenesis, inflammation and metastasis induction.

Differential Subcellular Distribution of Mitoxantrone in Relation to Chemosensitization in Two Human Breast Cancer Cell Lines

The present work investigates the relationship between cancer cell chemosensitivity and subcellular distribution, molecular interaction, and metabolism of an anticancer drug. To get insights into this relationship, we took advantage of the differential sensitivity of two breast cancer cell lines, MDA-MB-231 and MCF-7, to anthracyclines, along with the property of docosahexaenoic acid (DHA, 22:6n-3), to differentially enhance their cytotoxic activity. The fluorescent drug mitoxantrone (MTX) was used because of the possibility to study its subcellular accumulation by confocal spectral imaging (CSI). The use of CSI allowed us to obtain semiquantitative maps of four intracellular species: nuclear MTX bound to DNA, MTX oxidative metabolite in endoplasmic reticulum, cytosolic MTX, and finally, MTX in a low polarity environment characteristic of membranes. MDA-MB-231 cells were found to be more sensitive to MTX (IC50 = 18 nM) than MCF-7 cells (IC50 = 196 nM). According to fluorescence levels, the nuclear and cytosolic MTX content was higher in MCF-7 than in MDA-MB-231 cells, indicating that mechanisms other than nuclear MTX accumulation account for chemosensitivity. In the cytosol, the relative proportion of oxidized MTX was higher in MDA-MB-231 (60%) than in MCF-7 (7%) cells. DHA sensitized MDA-MB-231 (approximately 4-fold) but not MCF-7 cells to MTX and increased MTX accumulation by 1.5-fold in MDA-MB-231 cells only. The DHA-stimulated accumulation of MTX was attributed mainly to the oxidative metabolite. Antioxidant N-acetyl-L-cysteine inhibited the DHA effect on both metabolite accumulation and cell sensitization to MTX. We conclude that drug metabolism and compartmentalization are associated with cell chemosensitization, and the related cytotoxicity mechanisms may involve oxidative stress.

Sensitization by dietary docosahexaenoic acid of rat mammary carcinoma to anthracycline: a role for tumor vascularization

PURPOSE

To investigate whether dietary docosahexaenoic acid (DHA), a peroxidizable polyunsaturated omega-3 fatty acids, sensitizes rat mammary tumors to anthracyclines and whether its action interferes with tumor vascularization, a critical determinant of tumor growth.

EXPERIMENTAL DESIGN

Female Sprague-Dawley rats were initiated by N-methylnitrosourea to develop mammary tumors and then assigned to a control group (n = 18), receiving a supplementation of palm oil, or to a DHA group (n = 54), supplemented with a microalgae-produced oil (DHASCO, 1.5 g/d). The DHA group was equally subdivided into three subgroups with addition of different amounts of alpha-tocopherol. Epirubicin was injected weekly during 6 weeks after the largest tumor reached 1.5 cm(2), and subsequent changes in the tumor surface were evaluated. Tumor vascularization was assessed by power Doppler sonography before and during chemotherapy.

RESULTS

DHA and alpha-tocopherol were readily absorbed and incorporated into rat tissues. Epirubicin induced a 45% mammary tumor regression in the DHA-supplemented group, whereas no tumor regression was observed in the control group. In the DHA group, before chemotherapy was initiated, tumor vascular density was 43% lower than in the control group and remained lower during chemotherapy. Enhancement of epirubicin efficacy by DHA was abolished in a dose-dependent manner by alpha-tocopherol, and the same trend was observed for DHA-induced reduction in tumor vascular density.

CONCLUSIONS

Dietary DHA supplementation led to a reduction in tumor vascularization before the enhancement of any response to anthracyclines, suggesting that DHA chemosensitizes mammary tumors through an inhibition of the host vascular response to the tumor.

ω-3 Polyunsaturated fatty acids and ionizing radiation: Combined cytotoxicity on human colorectal adenocarcinoma cells

OBJECTIVE

This study evaluated whether omega-3 polyunsaturated fatty acids (PUFAs) could enhance the radiosensitivity of three different human colorectal adenocarcinoma cell lines. To understand the underlying mechanisms, the effects of omega-3 PUFAs on the cell growth, survival, and apoptosis were evaluated alone or in combination with an antioxidant (vitamin E) and compared with the effects of omega-6 PUFAs.

METHODS

LS174T, CO112, and Caco-2 cell survival was assessed by clonogenic assay after a 3-d pretreatment with omega-3/omega-6 PUFAs and/or vitamin E before a single X-ray exposure to 4 Gy. Cell growth and viability were measured by double fluorescence-activated cell sorter analyses using propidium iodide and fluorescein isothiocyanate-conjugated annexin V. Student's t test or multivariable linear regression analyses were used for comparison.

RESULTS

Preincubation with 30 to 100 micromol/L of omega-3 PUFAs induced a dose-dependent additive decrease in cell survival after irradiation (P < 0.05). Evaluation of the underlying mechanisms indicated that omega-3 PUFAs mainly decreased the cell number via apoptosis induction. Moreover, formation of lipid peroxidation products and modulation of cyclooxygenase II activity seemed to be involved, because coincubation with 10 micromol/L vitamin E abolished the effect of 50 micromol/L of omega-3 PUFAs (P < 0.05), whereas omega-6 PUFAs could partly mimic omega-3 PUFA effects.

CONCLUSION

These observations suggest that omega-3 PUFAs may be potential candidates as nutritional adjuvants to enhance the efficacy of human colorectal cancer radiotherapy.

Dietary beta-carotene inhibits mammary carcinogenesis in rats depending on dietary alpha-linolenic acid content

To investigate whether dietary alpha-linolenic acid (ALA) content alters the effect of beta-carotene on mammary carcinogenesis, we conducted a chemically induced mammary tumorigenesis experiment in rats randomly assigned to four nutritional groups (15 rats per group) varying in beta-carotene supplementation and ALA content. Two oil formula-enriched diets (15 %) were used: one with 6 g ALA/kg diet in an essential fatty acids (EFA) ratio of linoleic acid:ALA of 5:1 w/w (EFA 5 diet), the other with 24 g ALA/kg diet in an EFA ratio of 1:1 w/w (EFA 1 diet), both designed with a similar linoleic acid content. beta-Carotene was either added (10 mg/kg diet per d) or not added to these diets. beta-Carotene supplementation led to decreased tumour incidence and tumour growth when added to the EFA 5 diet, whereas it had no effect when added to the EFA 1 diet. The decreased tumour growth did not result from an involvement of lipoperoxidation (tumour malondialdehyde content being similar between the groups) or from an inhibition of tumour cell proliferation (as there was an unchanged S phase fraction in the tumours). We concluded that an adequate content of ALA in the diet is required to allow a protective effect of beta-carotene in mammary carcinogenesis. Whether such an interaction between ALA and beta-carotene influences the risk of breast cancer in women needs to be investigated.

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.

Diet, cancer, and the lipidome

The potential for dietary fat to interfere with the development of breast cancer by delaying its occurrence makes the identification of defined molecules a mandatory step in cancer prevention. In order to circumvent the limitations and/or bias of dietary exposure assessment tools, biomarkers of past lipid intake such as the fatty acid composition of white adipose tissue have been used. When considered separately, candidate fatty acids identified as favorable on the basis of their association with breast cancer risk have usually led to inconsistent results in animal intervention studies. This inconsistency indicates that any approach based on a single fatty acid should be abandoned for an integrated view over the complex lipid interactions which finally determines the lipidome, the lipid profile that is found in individuals. This article presents a reappraisal of the role of the lipid profile through a comprehensive reanalysis of adipose tissue fatty acid composition obtained in patients with benign or malignant breast tumors as well as in experimental animals during dietary interventions. Rather than a single fatty acid, a composite indicator combining elevated monounsaturates and low omega6/omega3 fatty acid ratio was associated with breast cancer protection. This lipidome may become the template for identifying breast cancer risk related to diet, and for designing proper dietary modifications to delay the occurrence of breast cancer, although the universality of the findings cannot be assessed from a single study.

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.

Dietary omega-3 fatty acids and ionizing irradiation on human breast cancer xenograft growth and angiogenesis

BACKGROUND

The effects of an omega-3 (n-3) fatty acid enriched diet alone and in combination with gamma irradiation (IR) therapy in nude mice bearing a human MDA-MB231 breast cancer xenograft were tested. The cancer cells were injected into the mammary fat pad of young female mice. Six weeks later, mice were randomly divided into two diet groups: 1) mice with 10% corn oil (rich in omega 6 fatty acids) in their food, 2) mice consuming a 10% fat diet that was enriched in n-3 fatty acids. After two weeks on the diet, treatment with 200 cGy of IR every second day for four treatments (total 800 cGy) was initiated on half of the mice from each diet group. Some mice in each of the 4 groups were euthanized 24 hours after the end of IR while the remaining mice were followed for 3 additional weeks. Tumor sections were stained for endothelial cells with CD31 and PAS and for hypoxia inducible factor 1α (HIF-α).

RESULTS

The tumor cortex within 100 microns of the well-vascularized capsule had little vascularization. Blood vessels, capillaries, and endothelial pseudopods were found at areas greater than 100 microns from the capsule (subcortex). Mice on the corn oil diet and treated with IR 24 hours previously or non-irradiated mice fed the n-3 diet had tumors with fewer blood vessels in the subcortex and more endothelial pseudopods projecting into hypoxic (HIF- α positive) areas than did mice from the non-irradiated corn oil fed group. The tumor growth rate of mice that received IR or that were fed the n-3 fatty acid enriched diet was significantly slower than in the mice fed the 10% corn oil diet. Harmful side effects were found only in the IR treated mice.

CONCLUSION

The omega-3 fatty acid enriched diet proved to be a safe means for retarding tumor growth and vascularization.

α-Tocopherol Suppresses Mammary Tumor Sensitivity to Anthracyclines in Fish Oil-Fed Rats

Polyunsaturated fatty acids (PUFAs) have been reported to enhance the efficacy of chemotherapeutic agents that produce reactive oxygen species such as anthracyclines. We previously reported in a human breast cancer cell line that the increased cytotoxic activity of anthracyclines by several PUFAs was abolished by antioxidants and enhanced by pro-oxidants, suggesting that lipid peroxidation was involved in this effect. To determine the relevance of this observation in vivo, we examined the effect of the oxidative status of the diet on the activity of epirubicin against N-methylnitrosourea-induced mammary tumors in Sprague-Dawley rats. Three groups of rats were fed a basal diet enriched with dietary n-3 PUFA (sardine oil, 15%) alone (control group), with addition of an antioxidant (alpha-tocopherol, 100 UI/kg diet), or with addition of an oxidant system (dehydroascorbate/naphthoquinone). When the first mammary tumor reached 1 cm2, epirubicin was administrated weekly for 3 wk, and subsequent change in tumor size was documented over time. Two weeks after the end of epirubicin injections, tumor size was increased by 34% in the control group. In the pro-oxidant group, tumor size was decreased by 50%. In contrast, tumor size was increased by 188% in the antioxidant group. Thus, addition of pro-oxidants in a fish oil-enriched diet increased the sensitization of mammary tumors to chemotherapy, whereas addition of alpha-tocopherol suppressed tumor response in vivo, indicating that interaction between components of the diet has to be carefully controlled during chemotherapy.

(n-3) fatty acids and cancer therapy

Supplementing the diet of tumor-bearing mice or rats with oils containing (n-3) (omega-3) or with purified (n-3) fatty acids has slowed the growth of various types of cancers, including lung, colon, mammary, and prostate. The efficacy of cancer chemotherapy drugs such as doxorubicin, epirubicin, CPT-11, 5-fluorouracil, and tamoxifen, and of radiation therapy has been improved when the diet included (n-3) fatty acids. Some potential mechanisms for the activity of (n-3) fatty acids against cancer include modulation of eicosanoid production and inflammation, angiogenesis, proliferation, susceptibility for apoptosis, and estrogen signaling. In humans, (n-3) fatty acids have also been used to suppress cancer-associated cachexia and to improve the quality of life. In one study, the response to chemotherapy therapy was better in breast cancer patients with higher levels of (n-3) fatty acids in adipose tissue [indicating past consumption of (n-3) fatty acids] than in patients with lower levels of (n-3) fatty acids. Thus, in combination with standard treatments, supplementing the diet with (n-3) fatty acids may be a nontoxic means to improve cancer treatment outcomes and may slow or prevent recurrence of cancer. Used alone, an (n-3) supplement may be a useful alternative therapy for patients who are not candidates for standard toxic cancer therapies.