Decreased tumor growth in Walker 256 tumor-bearing rats chronically supplemented with fish oil involves COX-2 and PGE2 reduction associated with apoptosis and increased peroxidation

The Influence of Omega-3 Fatty Acids on Skeletal Muscle Protein Turnover in Health, Disuse, and Disease

Ingestion of omega-3 fatty acids is known to exert favorable health effects on a number of biological processes such as improved immune profile, enhanced cognition, and optimized neuromuscular function. Recently, data have emerged demonstrating a positive influence of omega-3 fatty acid intake on skeletal muscle. For instance, there are reports of clinically-relevant gains in muscle size and strength in healthy older persons with omega-3 fatty acid intake as well as evidence that omega-3 fatty acid ingestion alleviates the loss of muscle mass and prevents decrements in mitochondrial respiration during periods of muscle-disuse. Cancer cachexia that is characterized by a rapid involuntary loss of lean mass may also be attenuated by omega-3 fatty acid provision. The primary means by which omega-3 fatty acids positively impact skeletal muscle mass is via incorporation of eicosapentaenoic acid (EPA; 20:5n−3) and docosahexaenoic acid (DHA; 22:6n−3) into membrane phospholipids of the sarcolemma and intracellular organelles. Enrichment of EPA and DHA in these membrane phospholipids is linked to enhanced rates of muscle protein synthesis, decreased expression of factors that regulate muscle protein breakdown, and improved mitochondrial respiration kinetics. However, exactly how incorporation of EPA and DHA into phospholipid membranes alters these processes remains unknown. In this review, we discuss the interaction between omega-3 fatty acid ingestion and skeletal muscle protein turnover in response to nutrient provision in younger and older adults. Additionally, we examine the role of omega-3 fatty acid supplementation in protecting muscle loss during muscle-disuse and in cancer cachexia, and critically evaluate the molecular mechanisms that underpin the phenotypic changes observed in skeletal muscle with omega-3 fatty acid intake.

Fish oil decreases the severity of treatment-related adverse events in gastrointestinal cancer patients undergoing chemotherapy: A randomized, placebo-controlled, triple-blind clinical trial

BACKGROUND AND AIMS

Due to its high peroxidizable characteristics, n-3 fatty acids, present in fish oil, could increase tumor cells sensitivity to conventional cancer treatment while non-neoplastic cells remain unaffected, this may lead to an increase in cancer treatment response with no increase on adverse effects. The aim of this study was to evaluate anti-cancer treatment response, performance status and adverse events in gastrointestinal cancer patients supplemented with fish oil. Oxidative stress parameters were investigated in blood non-neoplastic cells as an indicator of cytotoxicity.

METHODS

This is a randomized, triple-blind, placebo-controlled clinical trial. Fish oil group (FOG) received two capsules of fish oil containing 1.55 g of EPA + DHA a day for nine weeks, placebo group (PG) received two capsules containing olive oil. Baseline was set right before the administration of the first chemotherapy, oxidative stress parameters, adverse events presence and grading and performance status were assessed at baseline and after nine weeks of supplementation. Tumor markers, response to treatment and survival were evaluated at baseline and after one year of study inclusion.

RESULTS

76 patients were considered eligible, 56 were randomized, and 51 remained for analysis. After nine weeks, although there were no differences between groups for treatment response and presence of adverse events, PG patients were graded with more severe diarrhea than FOG patients (p = 0.03) and with higher (worse) performance status score (p = 0.02). No differences in lipid peroxidation and activity of antioxidant enzymes were observed between groups.

CONCLUSIONS

Fish oil may lead to a better performance status for gastrointestinal cancer patients undergoing chemotherapy while does not seem to increase treatment-related toxicity. Registered under ClinicalTrials.gov Identifier no. NCT02699047, www.clinicaltrials.gov.

Nutrition and Cancercapsaicin Treatment Reduces Tumor Growth, Tumor Cell Proliferation Ex Vivo and Partially Reverses Cancer Cachexia in Walker 256 Tumor-Bearing Rats

Capsaicin (trans-8-methyl-n-vanillyl-6-nonenamide) is the main pungent component found in hot peppers.

AIM

In this study, we investigated the effect of capsaicin treatment on tumor growth and the metabolic indicators of cachexia in Walker 256 tumor-bearing rats.

METHODS

Male Wistar rats were inoculated subcutaneously in the right flank with 1 ml of a sterile suspension of 3 × 10⁷ Walker tumor cells. The treated groups received capsaicin intraperitoneal 5 mg/kg body weight for 13 days.

RESULTS

The tumor weight on Day 14 in the non-treated group was 18 g. The rats also had a body weight loss, hypoglycemia, hyperlactacidemia, hypertriacylglycerolemia, and a depletion in glycogen storage. Treatment with capsaicin decreased tumor growth by 49% and a reversal of triacylglycerol serum. We also found a 32% reduction in tumor cell proliferation ex vivo. Lactate serum concentrations and body weight were lower but did not reach control levels.

CONCLUSION

The treatment with capsaicin reduces tumor growth and cellular proliferation along with increased apoptosis and partial cachexia reversal.

The effects of dietary polyunsaturated fatty acids on miR-126 promoter DNA methylation status and VEGF protein expression in the colorectal cancer cells

Background

There is increasing evidence indicating an aberrant expression of miRNAs in colorectal cancer (CRC) development. Growing evidence has suggested that polyunsaturated fatty acids (PUFAs) could modulate the remodeling of the epigenome. No study has yet been published to examine the direct effect of PUFA on the promoter methylation of miRNAs. This study aimed to examine the potential clinical application of PUFA on the promoter DNA methylation of miR-126 and its angiogenic target molecule (VEGF) in the CRC cells.

Methods

We investigated the direct effect of 100 μM EPA, DHA, and LA for 24 h on promoter methylation status of miR-126 in a panel of five CRC cell lines (HCT116, HT29/219, Caco2, SW742, and LS180) by methylation-specific PCR (MSP). We also quantified the miR-126 and VEGF transcript expression levels in five CRC cell lines affected by PUFA by real-time PCR. Moreover, we analyzed the protein expression level of VEGF, as a target of miR-126, by western blotting assay.

Results

MSP analysis showed extensive DNA methylation of the miR-126 promoter in all five CRC cell lines, and among all three PUFAs, only DHA completely demethylated the promoter of miR-126 in HCT116 and Caco2 cell lines. We found that only DHA significantly induces the expression level of miR-126 in HCT116 and Caco2 cell lines, respectively, by 20.1-fold and 1.68-fold (p < 0.05). Our finding indicates that the downregulation of VEGF protein level is also effectively observed only in DHA-treated HCT116 and Caco2 cells compared to control cells (p < 0.05).

Conclusions

Our results provide evidence that n-3 PUFAs are able to modulate cellular miR-126 DNA methylation and inhibit VEGF expression level in a cell-type specific manner in colorectal cancer cells. DHA always showed higher efficacy than EPA and LA in our experiment. Overall, our results suggest a potential clinical application of n-3 PUFAs as anti-angiogenic agents in CRC therapy.

The implications of signaling lipids in cancer metastasis

Metastasis is the most malignant stage of cancer. Lipid metabolic abnormalities are now increasingly recognized as characteristics of cancer cells. The accumulation of certain lipid species, such as signaling lipids, due to the avidity of lipid metabolism may be a causal factor of tumor malignant progression and metastatic behavior. In this review, we first describe signaling lipids implicated in cancer migration, invasion and metastasis. Next, we summarize the regulatory signaling hubs of lipid anabolic and catabolic metabolism. We then address lipid-rich circulating tumor cells (CTCs) and the lipid composition of exosomes budded off from tumor cells. We also present advances in targeting the regulatory hubs of lipid metabolism and signaling lipids in cancer therapy. Given the complexity of metabolic disorders in cancer, the development of significant portfolios of approaches to target signaling lipids by the integration of multiple chemical modulations, as well as molecular imaging modalities, should offer promising strategies for cancer therapy.

Lipid molecules with cellular signaling roles are increasingly recognized as playing a role in cancer metastasis, the dangerous spread of cancer cells beyond a primary tumor, and these lipids may offer new targets for anti-cancer treatments. Researchers in China led by Xiangjian Luo and Ya Cao at the Central South University in Changsha review the involvement of signaling lipids in cancer. The signaling lipids are a structurally diverse range of molecules that can regulate metabolic processes which become disrupted in cancer. They can act within cells and also when released from some cells to interact with others. Some of the lipids are released in tiny membrane-bound sacs called exosomes. Modifying the lipid content of exosomes, or purifying and then re-administering exosomes to deliver drugs, could offer promising options for developing novel treatments for cancer.

Long-chain n-3 PUFA against breast and prostate cancer: Which are the appropriate doses for intervention studies in animals and humans?

The potential antineoplastic effect of the long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) remains a highly controversial issue. Numerous animal studies have supported the anticancer role of these dietary fatty acids, whereas conflicting results have been obtained in population studies, and only a few intervention human trials have been so far performed. In view of the possibility that the anticancer effects may be maximally observed within a defined range of EPA and DHA doses, herein we critically review the results and doses used in both animal studies and human clinical trials focusing on the possible n-3 PUFA protective effects against breast and prostate cancer. Our main aim is to identify the EPA and/or DHA ranges of doses needed to obtain clear anticancer effects. This may be of great help in designing future animal studies, and also in understanding the most appropriate dose for further human intervention studies. Moreover, since the healthy effects of these fatty acids have been strictly related to their increased incorporation in plasma and tissue lipids, we also examine and discuss the incorporation changes following the administration of the effective anticancer EPA and/or DHA doses in animals and humans.

Trp53 deficient mice predisposed to preterm birth display region-specific lipid alterations at the embryo implantation site

Here we demonstrate that conditional deletion of mouse uterine Trp53 (p53^d/d), molecularly linked to mTORC1 activation and causally linked to premature uterine senescence and preterm birth, results in aberrant lipid signatures within the heterogeneous cell types of embryo implantation sites on day 8 of pregnancy. In situ nanospray desorption electrospray ionization mass spectrometry imaging (nano-DESI MSI) was used to characterize the molecular speciation of free fatty acids, monoacylglycerol species, unmodified and oxidized phosphatidylcholine (PC/Ox-PC), and diacylglycerol (DG) species within implantation sites of p53^d/d mice and floxed littermates. Implantation sites from p53^d/d mice exhibited distinct spatially resolved changes demonstrating accumulation of DG species, depletion of Ox-PC species, and increase in species with more unsaturated acyl chains, including arachidonic and docosahexaenoic acid. Understanding abnormal changes in the abundance and localization of individual lipid species early in the progression to premature birth is an important step toward discovering novel targets for treatments and diagnosis.

Fish oil administration mediates apoptosis of Walker 256 tumor cells by modulation of p53, Bcl-2, caspase-7 and caspase-3 protein expression

Background

Several studies have been shown pro-apoptotic effects of fish oil (FO), rich in n-3 polyunsaturated fatty acids (n-3 PUFA) on cancer cells. Nevertheless, few in vivo experiments have provided data of its ability on apoptosis protein expression in tumor tissue. Thus, in this study we investigate the effect of FO supplementation on apoptosis protein expression in Walker 256 tumor bearing rats. Male Wistar rats were randomly assigned to three groups: fed with regular chow (W); fed regular chow supplemented with FO (WFO) or coconut fat (WCO) (1 g/kg body weight/daily). After thirty days, all animals were inoculated subcutaneously with Walker 256 tumor cells.

Findings

Protein expression was done by western blotting in Walker 256 tumor tissue samples. FO decreased the Bcl-2/Bax ratio (p < 0.05) and increased the p53 (p < 0.05), cleaved caspase-7 (p < 0.05) and cleaved caspase-3 (p < 0.05) in Walker 256 tumor tissue.

Conclusions

Our data suggest that the pro-apoptotic effect of FO in Walker 256 tumor is related with specifics cleaved caspases.

Exercício de força associado a óleo de peixe reduzem massa tumoral e caquexia em ratos

OBJETIVO: Investigar o efeito do treinamento de salto associado à suplementação com óleo de peixe (1g/kg peso corporal/dia) em ratos portadores do tumor de Walker 256, sobre parâmetros bioquímicos de caquexia e crescimento tumoral.MÉTODOS: Oitenta Ratos foram divididos em sedentário sem ou com tumor (S ou SW), exercitado (EX ou EXW), suplementado com óleo de peixe (SO ou SWO) e suplementado e exercitado (EXO ou EXWO). Sessões de treinamento de salto consistiram de 10 séries com duração de 30 segundos e intervalo de 1 minuto entre cada série. Após seis semanas de treinamento, células do tumor de Walker 256 foram inoculadas e após 15 dias os animais foram mortos.RESULTADOS: O peso médio do tumor no grupo SW foi de 25,32 g, p<0,05 vs. ao dos SWO, EXW e EXWO (~11 g). O grupo SW apresentou hipoglicemia, hiperlactatemia, hipertriacilglicerolemia e perda de peso (-7,52±3,19g), caracterizando estado caquético. Suplementação com óleo de peixe (SWO), exercício (EXW) e associação de ambos (EXWO) impediram a instalação da caquexia (p<0,05 vs. SW). No grupo SWO, EXW e suas associações (EXWO) promoveram ganho de peso (p<0,05 vs. SW), mas inferior ao da suplementação isolada (p<0,05 vs. SWO). A proliferação celular in vitro das células tumorais foi menor no grupo SWO (p<0,05 vs. SW) e o exercício reduziu ainda mais (p<0,05 vs. SW e SWO), não havendo incremento quando se associaram ambas as terapias. Lipoperoxidação (p<0,05) foi maior nos SWO, EXW, EXWO vs. S. A expressão de Bcl-2 foi menor também nestes grupos vs. SW.CONCLUSÕES: O treinamento de força e a suplementação com óleo de peixe foram eficazes em evitar a caquexia e induzir a redução do crescimento tumoral, da proliferação tumoral e expressão de Bcl-2, mas a associação de ambos não promoveu efeito aditivo.

The role of inflammation in colon cancer

Colorectal cancer (CRC) is the one of the leading causes of cancer-related deaths in the world. CRC is responsible for more than 600,000 deaths annually and incidence rates are increasing in most of the developing countries. Epidemiological and laboratory investigations suggest that environmental factors such as western style dietary habits, tobacco-smoking, and lack of physical activities are considered as risks for CRC. Molecular pathobiology of CRC implicates pro-inflammatory conditions to promote the tumor malignant progression, invasion, and metastasis. It is well known that patients with inflammatory bowel disease are at higher risk of CRC. Many evidences exist reiterating the link between Inflammation and CRC. Inflammation involves interaction between various immune cells, inflammatory cells, chemokines, cytokines, and pro-inflammatory mediators, such as cyclooxygenase (COX) and lipoxygenase (LOX) pathways, which may lead to signaling towards, tumor cell proliferation, growth, and invasion. Thus, this review will focus on mechanisms by which pro-inflammatory mediators and reactive oxygen/nitrogen species play a role in promoting CRC. Based on these mechanisms, various preventive strategies, involving anti-inflammatory agents, such as COX inhibitors, COX-LOX inhibitors, iNOS inhibitors, natural supplements/agents, and synthetic agents, that blocks the inflammatory pathways and suppress CRC are discussed in this review.

Antitumor and anti-cachectic effects of shark liver oil and fish oil: comparison between independent or associative chronic supplementation in Walker 256 tumor-bearing rats

BACKGROUND

Shark liver oil (SLOil) and fish oil (FOil), which are respectively rich in alkylglycerols (AKGs) and n-3 polyunsaturated fatty acids (PUFAs), are able to reduce the growth of some tumors and the burden of cachexia. It is known that FOil is able to reduce proliferation rate and increase apoptotic cells and lipid peroxidation of tumor cells efficiently. However, there are few reports revealing the influence of SLOil on these parameters. In the current study, effects of FOil chronic supplementation on tumor growth and cachexia were taken as reference to compare the results obtained with SLOil supplementation. Also, we evaluated if the association of SLOil and FOil was able to promote additive effects.

METHODS

Weanling male Wistar rats were divided into 4 groups: fed regular chow (C), supplemented (1 g/kg body weight) with SLOil (CSLO), FOil (CFO) and both (CSLO + FO). After 8 weeks half of each group was inoculated with Walker 256 cells originating new groups (W, WSLO, WFO and WSLO + FO). Biochemical parameters of cachexia, tumor weight, hydroperoxide content, proliferation rate and percentage of apoptotic tumor cells were analysed. Fatty acids and AKG composition of tumor and oils were obtained by high performance liquid chromatography and gas chromatography - mass spectrometry, respectively. Statistical analysis was performed by unpaired t-test and one-way ANOVA followed by a post hoc Tukey test.

RESULTS

Fourteen days after inoculation, SLOil was able to restore cachexia parameters to control levels, similarly to FOil. WSLO rats presented significantly lower tumor weight (40%), greater tumor cell apoptosis (~3-fold), decreased tumor cell proliferation (35%), and higher tumor content of lipid hydroperoxides (40%) than observed in W rats, but FOil showed more potent effects. Supplementation with SLOil + FOil did not promote additive effects. Additionally, chromatographic results suggested a potential incorporation competition between the n-3 fatty acids and the AKGs in the tumor cells' membranes.

CONCLUSIONS

SLOil is another marine source of lipids with similar FOil anti-cachectic capacity. Furthermore, despite being less potent than FOil, SLOil presented significant in vivo antitumor effects. These results suggest that the chronic supplementation with SLOil may be adjuvant of the anti-cancer therapy.

Tumor growth reduction is regulated at the gene level in Walker 256 tumor-bearing rats supplemented with fish oil rich in EPA and DHA

We investigated the effect of fish oil (FO) supplementation on tumor growth, cyclooxygenase 2 (COX-2), peroxisome proliferator-activated receptor gamma (PPARγ), and RelA gene and protein expression in Walker 256 tumor-bearing rats. Male Wistar rats (70 days old) were fed with regular chow (group W) or chow supplemented with 1 g/kg body weight FO daily (group WFO) until they reached 100 days of age. Both groups were then inoculated with a suspension of Walker 256 ascitic tumor cells (3×10⁷ cells/mL). After 14 days the rats were killed, total RNA was isolated from the tumor tissue, and relative mRNA expression was measured using the 2^-ΔΔCT method. FO significantly decreased tumor growth (W=13.18±1.58 vs WFO=5.40±0.88 g, P<0.05). FO supplementation also resulted in a significant decrease in COX-2 (W=100.1±1.62 vs WFO=59.39±5.53, P<0.001) and PPARγ (W=100.4±1.04 vs WFO=88.22±1.46, P<0.05) protein expression. Relative mRNA expression was W=1.06±0.022 vs WFO=0.31±0.04 (P<0.001) for COX-2, W=1.08±0.02 vs WFO=0.52±0.08 (P<0.001) for PPARγ, and W=1.04±0.02 vs WFO=0.82±0.04 (P<0.05) for RelA. FO reduced tumor growth by attenuating inflammatory gene expression associated with carcinogenesis.

Effects of omega-3 fatty acids on regulatory T cells in hematologic neoplasms

The development of leukemia and lymphomas is related to the increase in inflammatory process modulators. These, in turn, have divergent actions on the neoplastic process. Populations of T cells have different roles in the neoplastic environment; while interferon-gamma positive T cells have antitumor activity, the FoxP3+interleukin-10 positive population present a pro-tumor activity. Simultaneously, the inflammatory process promotes the mobilization of fatty acids from the cell membrane to produce lipid mediators, which also participate of the inflammatory response. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) omega-3 fatty acids, when incorporated in the plasmatic membrane, decrease the arachidonic acid (AA) metabolism and the production of eicosanoids derived from it. Thus, an alternative family of lipid mediators are produced that are often less inflammatory than those produced from arachidonic acid. Fatty acids can also influence the production of peptide mediators such as cytokines, and the expression of transcription factors, which can determine the production patterns of eicosanoids and cytokines as well as cell differentiation. Due to these properties, the objective of this literature review was to investigate studies published over the last 15 years on the effects of using omega-3 fatty acids on inflammatory markers in leukemia and lymphomas.

The effectiveness of fish oil supplementation in asthmatic rats is limited by an inefficient action on ASM function

Episodes of acute exacerbation are the major clinical feature of asthma and therefore represent an important focus for developing novel therapies for this disease. There are many reports that the n-3 fatty acids found in fish oil exert anti-inflammatory effects, but there are few studies of the action of fish oil on airway smooth muscle (ASM) function. In the present investigation, we evaluated the effect of fish oil supplementation on smooth muscle force of contraction in ovalbumin-induced asthmatic Wistar rats, and its consequences on static lung compliance, mucus production, leukocyte chemotaxis and production of proinflammatory cytokines. Fish oil supplementation suppressed the infiltration of inflammatory cells into the lung in asthmatic animals (2.04 ± 0.19 × 10(6) cells vs. 3.33 ± 0.43 × 10(6) cells in the control asthmatic group; P < 0.05). Static lung compliance increased with fish oil supplementation in asthmatic rats (0.640 ± 0.053 mL/cm H2O vs. 0.399 ± 0.043 mL/cm H2O; P < 0.05). However, fish oil did not prevent asthma-associated lung eosinophilia and did not affect the concentrations of tumor necrosis factor-α and interleukin-1β in lung tissue or the proportion of the airways obliterated with mucus. Fish oil had no effect on the force of contraction in asthmatic rats in response to acetylcholine (3.026 ± 0.274 mN vs. 2.813 ± 0.364 mN in the control asthmatic group). In conclusion, although fish oil exerts some benefits in this model of asthma, its effectiveness appears to be limited by an inefficient action on airway smooth muscle function.

Dietary fish oil reduces glomerular injury and elevated renal hydroxyeicosatetraenoic acid levels in the JCR:LA-cp rat, a model of the metabolic syndrome

We have previously shown nutritional intervention with fish oil (n-3 PUFA) to reduce numerous complications associated with the metabolic syndrome (MetS) in the JCR:LA-corpulent (cp) rat. In the present study, we sought to explore the potential role of fish oil to prevent glomerulosclerosis in JCR:LA-cp rats via renal eicosanoid metabolism and lipidomic analysis. Male lean and MetS JCR:LA-cp rats were fed a lipid-balanced diet supplemented with fish oil (5 or 10 % of total fat). After 16 weeks of feeding, albuminuria was significantly reduced in MetS rats supplemented with 5 or 10 % fish oil ( − 53 and − 70 %, respectively, compared with the untreated MetS rats). The 5 % fish oil diet resulted in markedly lower glomerulosclerosis ( − 43 %) in MetS rats and to a lesser extent in those supplemented with 10 % fish oil. Interestingly, untreated MetS rats had higher levels of 11- and 12-hydroxyeicosatetraenoic acids (HETE) v. lean rats. Dietary fish oil reduced these levels, as well as other (5-, 9- and 15-) HETE. Whilst genotype did not alter prostanoid levels, fish oil reduced endogenous renal levels of 6-keto PGF1α (PGI2 metabolite), thromboxane B2 (TxB2), PGF2α and PGD2 by approximately 60 % in rats fed 10 % fish oil, and TxB2 ( − 50 %) and PGF2α ( − 41 %) in rats fed 5 % fish oil. In conclusion, dietary fish oil prevented glomerular damage in MetS rats and mitigated the elevation in renal HETE levels. These results suggest a potential role for dietary fish oil to improve dysfunctional renal eicosanoid metabolism associated with kidney damage during conditions of the MetS.

Eicosanoid signalling pathways in the development and progression of colorectal cancer: novel approaches for prevention/intervention

Arachidonic acid metabolism through cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P-450 epoxygenase (EPOX) pathways leads to the generation of biologically active eicosanoids, including prostanoids, leukotrienes, hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acid and hydroperoxyeicosatetraenoic acids. Eicosanoid expression levels vary during tumor development and progression of a range of malignancies, including colorectal cancer. The actions of these autocoids are also directly influenced by diet, as demonstrated by recent evidence for omega-3 fatty acids in colorectal cancer (CRC) prevention and/or treatment. Eicosanoids regulate CRC development and progression, while inhibition of these pathways has generally been shown to inhibit tumor growth/progression. A progressive sequence of colorectal cancer development has been identified, ranging from normal colon, to colitis, dysplasia, and carcinoma. While both COX and LOX inhibition are both promising candidates for colorectal cancer prevention and/or treatment, there is an urgent need to understand the mechanisms through which these signalling pathways mediate their effects on tumorigenesis. This will allow identification of safer, more effective strategies for colorectal cancer prevention and/or treatment. In particular, binding to/signalling through prostanoid receptors have recently been the subject of considerable interest in this area. In this review, we discuss the role of the eicosanoid signalling pathways in the development and progression of colorectal cancer. We discuss the effects of the eicosanoids on tumor cell proliferation, their roles in cell death induction, effects on angiogenesis, migration, invasion and their regulation of the immune response. Signal transduction pathways involved in these processes are also discussed. Finally, novel approaches targeting these arachidonic acid-derived eicosanoids (using pharmacological or natural agents) for chemoprevention and/or treatment of colorectal cancer are outlined.

Tumor growth reduction in Walker 256 tumor-bearing rats performing anaerobic exercise: participation of Bcl-2, Bax, apoptosis, and peroxidation

Physical activity has been used in cancer prevention and treatment. In this study, we investigated some of the mechanisms by which anaerobic exercise reduces tumor growth. To do so, rats were trained for 8 weeks. Training consisted of jumping in a swimming pool for ten 30-s sets, with a load that was 50% of body weight attached to the back, 4 times per week. At the sixth week, anaerobic exercise trained rats (EX group) were inoculated with a suspension of Walker 256 tumor cells. Tumor weight, apoptotic tumor cells, tumor Bax and Bcl-2 protein expression, tumor lipid peroxidation, and tumor cell proliferation ex vivo were evaluated. Tumor weight was significantly lower in the EX group (∼30%) than in rats that did not undergo training (sedentary group) (p < 0.05). Apoptosis in the tumor cells of EX rats was 2-fold higher than in the tumor cells of sedentary rats; in addition, Bax expression increased by 10% and Bcl-2 decreased by 13% in EX rats. Lipid peroxidation was 4-fold higher in the tumor cells of EX rats than in those of sedentary rats (p < 0.05). Tumor cell proliferation ex vivo was 29% lower in the EX group than in the sedentary group (p < 0.05). In conclusion, Walker 256 tumor-bearing exercised rats presented more tumor cell apoptosis, a higher tumor content of lipid peroxides, pro-apoptotic protein expression balance, and reduced tumor weight and cell proliferation ex vivo, compared with sedentary rats. These events, together, account for the lower tumor growth we observed in the EX rats.

Walker-256 tumor growth is inhibited by the independent or associative chronic ingestion of shark liver and fish oil: a response linked by the increment of peritoneal macrophages nitrite production in Wistar rats

Fish oil (FO) is widely known by its capacity to positively modulate immune parameters and decrease the growth of some tumors. Despite the enormous number of studies addressing the effects of FO, there are few reports showing similar results using other marine sources of lipid compounds with biologic importance. This study aimed to compare the effects of shark liver oil (SLO), which is a source of omega-3 fatty acids and alkylglycerols, with those obtained with FO administration, or the association of both, on tumor growth and the innate immune system in Walker-256 tumor-bearing rats. Beginning at 21 days of age, Wistar rats were fed regular chow and/or FO and/or SLO supplement (1 g/kg body weight per day) for 14 weeks. Walker-256 tumor cells were inoculated on the 90th day. As expected, 14 days after inoculation, rats fed with FO presented tumor weights that were 50% lower than the control tumors (P < .05). The association of both FO and SLO and ingestion of SLO alone also reached the same reduction level. Except for adhesion, all macrophage parameters assayed were 200% higher in rats fed with FO and those supplemented with both FO and SLO compared with control rats. Only reactive nitrogen species production was increased by SLO. These results suggest that SLO might also have indirect antitumor properties. Conversely, there were no additive effects when SLO was administered with FO. Therefore, SLO is another marine compound with in vivo antitumor effects, but its action mechanisms seem not to be related to major modifications on macrophage function.

Effect of ω-3 fatty acid on gastrointestinal motility after abdominal operation in rats

Objective. To investigate whether ω-3 fatty acid could stimulate gastrointestinal motility after abdominal operation. Method. Wistar rats were randomly divided into 3 group (normal saline group, intralipid group, and ω-3 fatty acid group, n = 18/group) after partial caecectomy and gastrostomosis, each group was divided into 3 groups (POD1, POD3, and POD6, n = 6/group). Serum gastrin (GAS), motilin (MTL), interleukin-1 (IL-1), interleukin-6 (IL-6), tissue necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), gastric emptying rate, and small bowel propulsion rate were measured. Results. On POD 3, gastric emptying rate and small bowel propulsion rate in ω-3 fatty acid group were higher than those in normal saline group and intralipid group. Serum GAS and MTL levels in ω-3 fatty acid group were higher than those in normal saline group, but serum IL-1, IL-6, TNF-α, and COX-2 levels were lower than those in normal saline group and intralipid group. Conclusion. ω-3 fatty acid could accelerate the recovery of gastrointestinal mobility after abdominal operation in rats, mainly by relieving postoperative inflammation.

Docosahexaenoic acid reverts resistance to UV-induced apoptosis in human keratinocytes: involvement of COX-2 and HuR

The dramatic increase in the incidence of nonmelanoma skin cancer over the last decades has been related to the augmented exposure to ultraviolet (UV) radiation (UVR). It is known that apoptosis is induced as a protective mechanism after the acute irradiation of keratinocytes, whereas apoptotic resistance and carcinogenesis may follow the chronic exposure to UVR. We found that not all the human keratinocytes lines studied underwent apoptosis following acute exposure to UVR (10-60 mJ/cm(2)). Whereas UVR induced apoptosis in the HaCaT cells, NCTC 2544 and nr-HaCaT cells showed apoptosis resistance. The cytokeratin pattern of the apoptosis-resistant cells indicated that they possessed a degree of differentiation lower than that of HaCaT cells. They also showed an enhanced expression of cyclooxygenase-2 (COX-2), an early marker of carcinogenesis in various tissues, including skin. n-3 polyunsaturated fatty acids have drawn increasing interest as nutritional factors with the potential to reduce UVR carcinogenesis, and since they are apoptosis inducers and COX-2 inhibitors in cancer cells, we investigated the ability of n-3 polyunsaturated fatty acids to influence the resistance to UVR-induced apoptosis in keratinocytes. We observed that docosahexaenoic acid (DHA) reverted the resistance of nr-HaCaT cells to UVR-induced apoptosis, increasing the Bax/Bcl-2 ratio and caspase-3 activity, and reduced COX-2 levels by inhibiting the expression of the human antigen R (HuR), a known COX-2 mRNA stabilizer in keratinocytes. The transfection of nr-HaCaT cells with HuR siRNA mimicked the proapoptotic effect of DHA. Overall, our findings further support the role of DHA as a suitable anticarcinogenic factor against nonmelanoma skin cancers.

Glucose metabolism by lymphocytes, macrophages, and tumor cells from Walker 256 tumor-bearing rats supplemented with fish oil for one generation

Here we investigated the effect of lifelong supplementation of the diet with coconut fat (CO, rich in saturated fatty acids) or fish oil (FO, rich in n-3 polyunsaturated fatty acids) on tumor growth and lactate production from glucose in Walker 256 tumor cells, peritoneal macrophages, spleen, and gut-associated lymphocytes. Female Wistar rats were supplemented with CO or FO prior to mating and then throughout pregnancy and gestation and then the male offspring were supplemented from weaning until 90 days of age. Then they were inoculated subcutaneously with Walker 256 tumor cells. Tumor weight at 14 days in control rats (those fed standard chow) and CO supplemented was approximately 30 g. Supplementation of the diet with FO significantly reduced tumor growth by 76%. Lactate production (nmol h(-1) mg(-1) protein) from glucose by Walker 256 cells in the group fed regular chow (W) was 381.8 +/- 14.9. Supplementation with coconut fat (WCO) caused a significant reduction in lactate production by 1.6-fold and with fish oil (WFO) by 3.8-fold. Spleen lymphocytes obtained from W and WCO groups had markedly increased lactate production (553 +/- 70 and 635 +/- 150) when compared to non-tumor-bearing rats ( approximately 260 +/- 30). FO supplementation reduced significantly the lactate production (297 +/- 50). Gut-associated lymphocytes obtained from W and WCO groups increased lactate production markedly (280 +/- 31 and 276 +/- 25) when compared to non-tumor-bearing rats ( approximately 90 +/- 18). FO supplementation reduced significantly the lactate production (168 +/- 14). Lactate production by peritoneal macrophages was increased by tumor burden but there was no difference between the groups fed the various diets. Lifelong consumption of FO protects against tumor growth and modifies glucose metabolism in Walker tumor cells and lymphocytes but not in macrophages.

Effect of endurance training upon lipid metabolism in the liver of cachectic tumour-bearing rats

The syndrome of cancer cachexia is accompanied by several alterations in lipid metabolism, and the liver is markedly affected. Previous studies showed that moderate exercise training may prevent liver fat accumulation through diminished delivery of lipids to the liver, increased hepatic oxidation and increased incorporation of triacylglycerol (TAG) into very low density lipoprotein (VLDL). Our aim was to examine the influence of moderate intensity training (8 weeks) upon TAG content, VLDL assembly and secretion, apolipoprotein B (apoB) and microsomal transfer protein (MTP) gene expression in the liver of cachectic tumour-bearing rats. Animals were randomly assigned to a sedentary control (SC), sedentary tumour-bearing (ST) or exercise-trained control (EC) or to an exercise trained tumour-bearing (ET) group. Trained rats ran on a treadmill (60% VO(2max)) for 60 min day(-1), 5 day week(-1), for 8 weeks. TAG content and the rate of VLDL secretion (followed for 3 h), as well as mRNA expression of apoB and MTP, and total cholesterol, VLDL-TAG, VLDL-cholesterol, high density lipoprotein cholesterol (HDL-cholesterol) and tumour weight were evaluated. VLDL-cholesterol showed a decrease in ST (p < 0.05) in relation to SC. Serum TAG, VLDL-TAG and tissue TAG content were all increased in ST (p < 0.01), when compared with SC. ST showed a lower rate of VLDL secretion (p < 0.05) and reduced expression of apoB (p < 0.001) and MTP (p < 0.001), when compared with SC. These parameters were restored to control values (p < 0.05) when the animals were submitted to the exercise training protocol. Tumour weight decreased 10-fold after training (p < 0.001). It is possible to affirm, therefore, that endurance training promoted the re-establishment of lipid metabolism in cachectic tumour-bearing animals, especially in relation to VLDL secretion and assembly.

Production of cachexia mediators by Walker 256 cells from ascitic tumors

In neoplasic cachexia, chemical mediators seem to act as initiators or perpetuators of this process. Walker 256 cells, whose metabolic properties have so far been little studied with respect to cancer cachexia, are used as a model for the study of this syndrome. The main objective of this research was to pinpoint the substances secreted by these cells that may contribute to the progression of the cachectic state. Since inflammatory mediators seem to be involved in the manifestation of this syndrome, the in vitro production of nitric oxide (NO), cytokines (tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6)), and prostaglandin E2 (PGE2) was evaluated in Walker 256 cells isolated from ascitic tumors. After 4 or 5 h, a significant increase in NO production was observed (2.55 +/- 1.56 and 4.05 +/- 1.99 nmol NO per 10(7) cells, respectively). When isolated from a 6-day-old tumor, a significantly lower production of IL-6 and higher production of TNF-alpha than in cells from a 4-day-old tumor were observed, indicating a relationship between the production of cytokines and the time of tumor development after implantation. Considerable production of PGE(2) by Walker 256 cells isolated from the 6-day-old tumor was also observed. Polyamines were also determined in Walker 256 cells. Levels of putrescine, spermidine, and spermine did not show significant differences in tumors developed during 4 or 6 days. Direct evidence of the release of proinflammatory cytokines and PGE2 by Walker 256 cells suggests that these mediators can drive the cachectic syndrome in the host, the effect being dependent on tumor development time.

An enhanced apoptosis and a reduced angiogenesis are associated with the inhibition of lung colonisation in animals fed an n-3 polyunsaturated fatty acid-rich diet injected with a highly metastatic murine melanoma line

Both epidemiological and experimental studies indicate that dietary n-3 PUFA inhibit carcinogenesis and tumour growth. Metastatic diffusion has also been found to be affected in animals fed diets containing purified n-3 PUFA or fish oil. In the present study, we investigated whether the metastatic diffusion of a highly metastatic variant (F10-SR cells) isolated from the B16 melanoma F10 line was affected by feeding host animals a diet containing 5 % fish oil. In these animals, compared with those fed a diet containing 5 % maize oil, there was a reduced number of metastatic pulmonary colonies. The immunohistochemical analysis of appropriate markers revealed that the antimetastatic effect of dietary n-3 PUFA was not related to a reduction of proliferation, but rather to an enhanced apoptotic activity. The reduction of von Willebrand factor immunoreactivity found in pulmonary colonies of F10-SR cells grown in fish oil-fed animals indicates that a decrease of angiogenesis contributes to the antimetastatic effect of dietary n-3 PUFA. This conclusion stands in spite of the higher expression of vascular endothelial growth factor observed in pulmonary colonies grown in fish oil-fed animals.