Effects of eicosapentaenoic acid, gamma-linolenic acid and prostaglandin E1 on three human colon carcinoma cell lines

Omega-3 long-chain polyunsaturated fatty acids: Metabolism and health implications

Recently, omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) have gained substantial interest due to their specific structure and biological functions. Humans cannot naturally produce these fatty acids (FAs), making it crucial to obtain them from our diet. This comprehensive review details n-3 LC-PUFAs and their role in promoting and maintaining optimal health. The article thoroughly analyses several sources of n-3 LC-PUFAs and their respective bioavailability, covering marine, microbial and plant-based sources. Furthermore, we provide an in-depth analysis of the biological impacts of n-3 LC-PUFAs on health conditions, with particular emphasis on cardiovascular disease (CVD), gastrointestinal (GI) cancer, diabetes, depression, arthritis, and cognition. In addition, we highlight the significance of fortification and supplementation of n-3 LC-PUFAs in both functional foods and dietary supplements. Additionally, we conducted a detailed analysis of the several kinds of n-3 LC-PUFAs supplements currently available in the market, including an assessment of their recommended intake, safety, and effectiveness. The dietary guidelines associated with n-3 LC-PUFAs are also highlighted, focusing on the significance of maintaining a well-balanced intake of n-3 PUFAs to enhance health benefits. Lastly, we highlight future directions for further research in this area and their potential implications for public health.

Synthesis and Significance of Arachidonic Acid, a Substrate for Cyclooxygenases, Lipoxygenases, and Cytochrome P450 Pathways in the Tumorigenesis of Glioblastoma Multiforme, Including a Pan-Cancer Comparative Analysis

Glioblastoma multiforme (GBM) is one of the most aggressive gliomas. New and more effective therapeutic approaches are being sought based on studies of the various mechanisms of GBM tumorigenesis, including the synthesis and metabolism of arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA). PubMed, GEPIA, and the transcriptomics analysis carried out by Seifert et al. were used in writing this paper. In this paper, we discuss in detail the biosynthesis of this acid in GBM tumors, with a special focus on certain enzymes: fatty acid desaturase (FADS)1, FADS2, and elongation of long-chain fatty acids family member 5 (ELOVL5). We also discuss ARA metabolism, particularly its release from cell membrane phospholipids by phospholipase A₂ (cPLA₂, iPLA₂, and sPLA₂) and its processing by cyclooxygenases (COX-1 and COX-2), lipoxygenases (5-LOX, 12-LOX, 15-LOX-1, and 15-LOX-2), and cytochrome P450. Next, we discuss the significance of lipid mediators synthesized from ARA in GBM cancer processes, including prostaglandins (PGE₂, PGD₂, and 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂)), thromboxane A₂ (TxA₂), oxo-eicosatetraenoic acids, leukotrienes (LTB₄, LTC₄, LTD₄, and LTE₄), lipoxins, and many others. These lipid mediators can increase the proliferation of GBM cancer cells, cause angiogenesis, inhibit the anti-tumor response of the immune system, and be responsible for resistance to treatment.

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.

α-Linolenic and γ-linolenic acids exercise differential antitumor effects on HT-29 human colorectal cancer cells

α-Linolenic acid (ALA, 18:3n-3) and γ-gamma linolenic acid (GLA, 18:3n-6) are polyunsaturated fatty acids (PUFA) that improve the human health. The present study focused on testing the in vitro antitumor actions of pure ALA and GLA on the HT-29 human colorectal cancer cell line. Cell viability was checked by MTT ((3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, cell membrane damage by the lactate dehydrogenase assay, apoptosis was tested by both caspase-3 activity trial and transmission electron microscopy images, and protein composition was analyzed by quantitative proteomics analysis. MTT test revealed IC₅₀ values of 230 and 255 μM for ALA and GLA, respectively, at 72 h. After 24 h of incubation, both ALA and GLA induced apoptosis on HT-29 colorectal cancer cells according to the caspase-3 assay and microscopy images. SWATH/MS analysis evidenced that ALA significantly affected the mitochondrial protein import pathway and the citric acid cycle pathway, while GLA did not significantly affect any particular pathway. In summary, both ALA and GLA showed concentration-dependent inhibitory effects on HT-29 cells viability and induced cell death by apoptosis. ALA significantly affected cellular pathways, while GLA does not have specific actions on either pathway. Both n-3 and n-6 C18 PUFA are bioactive food components useful in the colorectal cancer prevention.

Differential action of polyunsaturated fatty acids and eicosanoids on bleomycin-induced cytotoxicity to neuroblastoma cells and lymphocytes

INTRODUCTION

This study was conducted to examine whether bleomycin-induced growth inhibitory action on human neuroblastoma cells (IMR-32) is influenced by anti-inflammatory metabolites of polyunsaturated fatty acids (PUFAs): lipoxin A4 (LXA4), resolvin D1 and protectin D1 in vitro.

MATERIAL AND METHODS

The in vitro study was conducted using monolayer cultures of exponentially growing IMR-32 cells. The effects of various PUFAs and eicosanoids and anti-inflammatory metabolites of PUFAs such as lipoxin A4 (LXA4), resolvin D1 and protectin D1 on the growth of IMR-32 cells and human lymphocytes in vitro were investigated. The potential of PUFAs, eicosanoids and LXA4, resolvin D1 and protectin D1 to modify the growth inhibitory effects of bleomycin was also studied in IMR-32 cells and human lymphocytes.

RESULTS

PUFAs inhibited the growth of IMR-32 cells (EPA > DHA = AA > GLA = ALA > DGLA = LA) significantly (p < 0.001) while prostaglandins were found to be not effective. Bleomycin-induced growth inhibitory action on IMR-32 cells was augmented by PUFAs and its metabolites (p < 0.05). PUFAs and LXA4 did not inhibit the growth of human lymphocytes and bleomycin-induced growth inhibitory action was also not enhanced by these bioactive lipids.

CONCLUSIONS

Bioactive lipids have differential action on normal human lymphocytes and tumor cells in vitro. The apparent lack of effect of PUFAs in combination with bleomycin on the growth of human lymphocytes in comparison to their growth inhibitory action on IMR-32 cells suggests that PUFAs can be used in combination with bleomycin to target tumor cells with little concern over this combination's effect on the growth of human lymphocytes. Further studies are warranted to evaluate these differential effects under in vivo conditions.

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

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

Potential applications of fish oils rich in omega-3 polyunsaturated fatty acids in the management of gastrointestinal cancer

BACKGROUND & AIMS

Despite advances in chemotherapeutic agents and surgical approaches for its management, gastrointestinal cancer still accounts for 27% of new cancer cases and 35% of cancer related mortality worldwide. Omega-3 polyunsaturated fatty acids (PUFAs) specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have anti-inflammatory and anticancer activities and are used as immuno-nutrients.

METHODS

A literature search was conducted to identify primary research reporting on applications of the omega-3 PUFAs in gastrointestinal cancer.

RESULTS

Reported laboratory studies indicate a clear role for omega-3 PUFAs in preventing cancer development at various stages including cancer cell proliferation, survival, angiogenesis, inflammation and metastasis. In clinical settings, omega-3 PUFAs have been reported to improve the immune response, maintain lean body mass, improve quality of life and improve overall survival in patients with colorectal and pancreatic cancer. In contrast to other GI cancers, there is a strong connection between inflammation and oesophageal cancer.

CONCLUSIONS

Little work has been done exploring the role for omega-3 PUFAs in oesophageal cancer prevention and management. The authors are conducting a clinical trial investigating the use of parenteral omega-3 PUFAs supplementary to the standard of care (epirubicin, oxaliplatin and capecitabine palliative chemotherapy) in patients with advanced oesophagogastric cancer as a promising new therapeutic approach.

Effect of polyunsaturated fatty acids and their metabolites on bleomycin-induced cytotoxic action on human neuroblastoma cells in vitro

In the present study, we noted that bleomycin induced growth inhibitory action was augmented by all the polyunsaturated fatty acids (PUFAs) tested on human neuroblastoma IMR-32 (0.5 × 10(4) cells/100 µl of IMR) cells (EPA > DHA > ALA = GLA = AA > DGLA = LA: ∼ 60, 40, 30, 10-20% respectively) at the maximum doses used. Of all the prostaglandins (PGE1, PGE2, PGF2α, and PGI2) and leukotrienes (LTD4 and LTE4) tested; PGE1, PGE2 and LTD4 inhibited the growth of IMR-32 cells to a significant degree at the highest doses used. Lipoxin A4 (LXA4), 19,20-dihydroxydocosapentaenoate (19, 20 DiHDPA) and 10(S),17(S)-dihydroxy-4Z,7Z,11E,13Z,15E,19Z-docosahexaenoic acid (protectin: 10(S),17(S)DiHDoHE), metabolites of DHA, significantly inhibited the growth of IMR-32 cells. Pre-treatment with AA, GLA, DGLA and EPA and simultaneous treatment with all PUFAs used in the study augmented growth inhibitory action of bleomycin. Surprisingly, both indomethacin and nordihydroguaiaretic acid (NDGA) at 60 and 20 µg/ml respectively enhanced the growth of IMR-32 cells even in the presence of bleomycin. AA enhanced oxidant stress in IMR-32 cells as evidenced by an increase in lipid peroxides, superoxide dismutase levels and glutathione peroxidase activity. These results suggest that PUFAs suppress growth of human neuroblastoma cells, augment growth inhibitory action of bleomycin by enhancing formation of lipid peroxides and altering the status of anti-oxidants and, in all probability, increase the formation of lipoxins, resolvins and protectins from their respective precursors that possess growth inhibitory actions.

Potential of long-chain n-3 polyunsaturated fatty acids in melanoma prevention

The possible antineoplastic activity of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) has been supported by ample preclinical studies that have identified a number of molecular factors and pathways affected by these fatty acids and involved in cell growth, apoptosis, invasion, and angiogenesis. The aim of this critical review is to assess the current state of knowledge on the potential anticancer effects of LC n-3 PUFAs against malignant melanoma, one of the most common cancers among Western populations. The results of preclinical as well as human observational and interventional studies investigating the effects of LC n-3 PUFAs in melanoma were examined. Overall, the analysis of the literature reveals that, even though a large body of information is available, further effort is needed to identify the main molecular targets of LC n-3 PUFAs in melanoma. Moreover, additional well-designed human observational studies are essential to shed further light on the issue. The results of these studies could provide support and specific information for the development of clinical studies, especially those performed in combination with conventional or innovative antineoplastic therapies.

The multifaceted effects of omega-3 polyunsaturated Fatty acids on the hallmarks of cancer

Omega-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid, and docosahexaenoic acid have been shown to have multiple beneficial antitumour actions that affect the essential alterations that dictate malignant growth. In this review we explore the putative mechanisms of action of omega-3 polyunsaturated fatty acid in cancer protection in relation to self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, apoptosis, limitless replicative potential, sustained angiogenesis, and tissue invasion, and how these will hopefully translate from bench to bedside.

Eicosapentaenoic acid (EPA) efficacy for colorectal aberrant crypt foci (ACF): a double-blind randomized controlled trial

BACKGROUND

Colorectal cancer (CRC) is one of the most commonly occurring neoplasms and a leading cause of cancer death worldwide, and new preventive strategies are needed to lower the burden of this disease. Eicosapentaenoic acid (EPA), the omega-3 polyunsaturated fatty acid that is widely used in the treatment of hyperlipidemia and prevention of cardiovascular disease, has recently been suggested to have a suppressive effect on tumorigenesis and cancer cell growth. In CRC chemoprevention trials, in general, the incidence of polyps or of the cancer itself is set as the study endpoint. Although the incidence rate of CRC would be the most reliable endpoint, use of this endpoint would be unsuitable for chemoprevention trials, because of the relatively low occurrence rate of CRC in the general population and the long-term observation period that it would necessitate. Moreover, there is an ethical problem in conducting long-term trials to determine whether a test drug might be effective or harmful. Aberrant crypt foci (ACF), defined as lesions containing crypts that are larger in diameter and stain more darkly with methylene blue than normal crypts, are considered as a reliable surrogate biomarker of CRC. Thus, we devised a prospective randomized controlled trial as a preliminary study prior to a CRC chemoprevention trial to evaluate the chemopreventive effect of EPA against colorectal ACF formation and the safety of this drug, in patients scheduled for polypectomy.

METHODS

This study is a multicenter, double-blind, placebo-controlled, randomized controlled trial to be conducted in patients with both colorectal ACF and colorectal polyps scheduled for polypectomy. Eligible patients shall be recruited for the study and the number of ACF in the rectum counted at the baseline colonoscopy. Then, the participants shall be allocated randomly to either one of two groups, the EPA group and the placebo group. Patients in the EPA group shall receive oral 900-mg EPA capsules thrice daily (total daily dose, 2.7 g per day), and those in the placebo group shall receive oral placebo capsules thrice daily. After one month's treatment with EPA/placebo, colonoscopic examination and polypectomy will be performed to evaluate the formation of ACF, and the cell-proliferative activity and cell-apoptotic activity in normal colorectal mucosa and colorectal polyps.

DISCUSSION

This is the first study proposed to explore the effect of EPA against colorectal ACF formation in humans.This trial has been registered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000008172.

Characterization of an arachidonic acid-deficient (Fads1 knockout) mouse model

Arachidonic acid (20:4(Δ5,8,11,14), AA)-derived eicosanoids regulate inflammation and promote cancer development. Previous studies have targeted prostaglandin enzymes in an attempt to modulate AA metabolism. However, due to safety concerns surrounding the use of pharmaceutical agents designed to target Ptgs2 (cyclooxygenase 2) and its downstream targets, it is important to identify new targets upstream of Ptgs2. Therefore, we determined the utility of antagonizing tissue AA levels as a novel approach to suppressing AA-derived eicosanoids. Systemic disruption of the Fads1 (Δ5 desaturase) gene reciprocally altered the levels of dihomo-γ-linolenic acid (20:3(Δ8,11,14), DGLA) and AA in mouse tissues, resulting in a profound increase in 1-series-derived and a concurrent decrease in 2-series-derived prostaglandins. The lack of AA-derived eicosanoids, e.g., PGE₂ was associated with perturbed intestinal crypt proliferation, immune cell homeostasis, and a heightened sensitivity to acute inflammatory challenge. In addition, null mice failed to thrive, dying off by 12 weeks of age. Dietary supplementation with AA extended the longevity of null mice to levels comparable to wild-type mice. We propose that this new mouse model will expand our understanding of how AA and its metabolites mediate inflammation and promote malignant transformation, with the eventual goal of identifying new drug targets upstream of Ptgs2.

Peroxidation of n-3 Polyunsaturated Fatty Acids Inhibits the Induction of iNOS Gene Expression in Proinflammatory Cytokine-Stimulated Hepatocytes

Eicosapentaenoic acid and docosahexaenoic acid (EPA/DHA), n-3 polyunsaturated fatty acids (PUFAs), have a variety of biological activities including anti-inflammatory and anticancer effects. We hypothesized that their peroxidized products contributed in part to anti-inflammatory effects. In the liver, the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated as one of the factors in hepatic inflammation and injury. We examined whether the peroxidation of EPA/DHA influences the induction of iNOS and NO production in proinflammatory cytokine-stimulated cultured hepatocytes, which is in vitro liver inflammation model. Peroxidized EPA/DHA inhibited the induction of iNOS and NO production in parallel with the increased levels of their peroxidation, whereas unoxidized EPA/DHA had no effects at all. Peroxidized EPA/DHA reduced the activation of transcription factor, NF-κB, and the expression of the iNOS antisense transcript, which are involved in iNOS promoter transactivation (mRNA synthesis) and its mRNA stabilization, respectively. These findings demonstrated that peroxidized products of EPA/DHA suppressed the induction of iNOS gene expression through both of the transcriptional and posttranscriptional steps, leading to the prevention of hepatic inflammation.

Cytotoxic activity of an octadecenoic acid extract from Euphorbia kansui (Euphorbiaceae) on human tumour cell strains

We have investigated the cytotoxic and antitumour activity of an octadecenoic acid extract, mainly containing oleic and linoleic acids, from Euphorbia kansui on human gastric (SGC-7901), hepatocellular carcinoma (BEL-7402), and leukaemia (HL-60) tumour cell strains. Significant and dose-dependent antiproliferation effects were observed on tumour cells from the dose of 3.2 μg mL−1, which were comparable with or better than those of the common antitumour agent 5-fluorouracil. Results from the clone formation assay and flow cytometry indicated that the mixture of octadecenoic acids resulted in a dose-dependent reduction in the number of tumour cells and significantly inhibited cell proliferation, with induced apoptosis and G0/G1 phase cell cycle arrest. Also, the octadecenoic acids could not only cause cell apoptosis/necrosis but also functionally and structurally damage the tumour cell membrane and cell ultra-structures. These observations encourage further clinical evaluation of the inhibitory effects of octadecenoic acids on various forms of cancer.

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.

Role of cAMP in the promotion of colorectal cancer cell growth by prostaglandin E2

Background

Prostaglandin E2 (PGE2), a product of the cyclooxygenase (COX) reaction, stimulates the growth of colonic epithelial cells. It is inferred that the abrogation of prostaglandins' growth-promoting effects as a result of COX inhibition underlies the advantageous effects of non-steroidal anti-inflammatory drugs in colorectal carcinoma (CRC). Despite this appreciation, the underlying molecular mechanisms remain obscure since cell culture studies have yielded discrepant results regarding PGE2's mitogenicity.

Methods

We have employed several alternative approaches to score cell proliferation and apoptosis of 4 CRC cell lines exposed to PGE2 under various conditions. To investigate the role of cAMP in PGE2's functions, activation of the cAMP pathway was assessed at different levels (changes in cAMP levels and PKA activity) in cells subjected to specific manipulations including the use of specific inhibitors or prostanoid receptor-selective agonists/antagonists.

Results

Our data document that the dose-response curve to PGE2 is 'bell-shaped', with nano molar concentrations of PGE2 being more mitogenic than micro molar doses. Remarkably, mitogenicity inversely correlates with the ability of PGE2 doses to raise cAMP levels. Consistent with a major role for cAMP, cAMP raising agents and pertussis toxin revert the mitogenic response to PGE2. Accordingly, use of prostanoid receptor-selective agonists argues for the involvement of the EP3 receptor and serum deprivation of HT29 CRC cells specifically raises the levels of Gi-coupled EP3 splice variants.

Conclusion

The present data indicate that the mitogenic action of low PGE2 doses in CRC cells is mediated via Gi-proteins, most likely through the EP3 receptor subtype, and is superimposed by a second, cAMP-dependent anti-proliferative effect at higher PGE2 doses. We discuss how these findings contribute to rationalize conflictive literature data on the proliferative action of PGE2.

Polyunsaturated fatty acids support epithelial barrier integrity and reduce IL-4 mediated permeability in vitro

BACKGROUND

The intestinal mucosa functions as a barrier against harmful dietary and microbial antigens. An intact gut barrier forms a prerequisite for protection against infection and allergy. Both allergic and inflammatory mediators (e.g. IL-4, IFN-gamma) are known to compromise the epithelial barrier integrity by enhancing permeability. Breast milk provides protection against infection and allergy and contains polyunsaturated fatty acids (PUFA).

AIM OF THE STUDY

Although PUFA are commonly used in infant formulas their effect on intestinal barrier is still poorly understood. Therefore the effects of distinct PUFA (n-6: LA, GLA, DGLA, AA; n-3: ALA, EPA, DHA) and a fat blend with PUFA composition similar to that of the human breast milk fat fraction, on barrier integrity were investigated.

METHODS

Human intestinal epithelial cells (T84) were pre-incubated with individual PUFA or a lipase treated fat blend, with or without subsequent IL-4 exposure. Barrier integrity was evaluated by measuring transepithelial resistance and permeability. Membrane phospholipid composition was determined by capillary gas chromatography.

RESULTS

DGLA, AA, EPA, DHA and to a lesser extend GLA enhanced basal TER and strongly reduced IL-4 mediated permeability, while LA and ALA were ineffective. Furthermore, the lipase treated fat blend effectively supported barrier function. PUFA were incorporated in the membrane phospholipid fraction of T84 cells.

CONCLUSIONS

Long chain PUFA DGLA, AA, EPA and DHA were particularly effective in supporting barrier integrity by improving resistance and reducing IL-4 mediated permeability. Fat blends that release specific PUFA upon digestion in the gastrointestinal tract may support natural resistance.

Resveratrol does not ameliorate muscle wasting in different types of cancer cachexia models

BACKGROUND & AIMS

Resveratrol has been reported to have antitumoural effects and recently it has been demonstrated that resveratrol partially blocks skeletal muscle wasting by interfering with NF-kappaB activation. We decided to investigate the potential anti-wasting properties of resveratrol on different models of cancer cachexia in experimental animals.

METHODS AND RESULTS

Incubations of isolated extensor digitorum longus muscles in the presence of 30 microM of resveratrol caused a significant decrease in the rate of protein degradation. However, administration of resveratrol in vivo to both rats bearing the Yoshida AH-130 ascites hepatoma (at the dose of 1 mg/kg body weight) and mice bearing the Lewis lung carcinoma (at two different doses, 5 and 25 mg/kg body weight) had no effect on skeletal muscle mass or body weight in tumour-bearing rodents. In addition, a combination of resveratrol (3 mg/kg body weight) and fish oil was also unable to induce any changes in skeletal muscle weights.

CONCLUSIONS

It is therefore concluded from this study that resveratrol is unable to influence muscle mass in vivo and has no potential role as anticachectic agent for the treatment of muscle wasting associated with tumour growth.

Closely related colon cancer cell lines display different sensitivity to polyunsaturated fatty acids, accumulate different lipid classes and downregulate sterol regulatory element-binding protein 1

N-6 polyunsaturated fatty acids (PUFAs) may be associated with increased risk of colon cancer, whereas n-3 PUFAs may have a protective effect. We examined the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid and arachidonic acid on the colon carcinoma cell lines SW480 derived from a primary tumour, and SW620 derived from a metastasis of the same tumour. DHA had the strongest growth-inhibitory effect on both cell lines. SW620 was relatively more growth-inhibited than SW480, but SW620 also had the highest growth rate in the absence of PUFAs. Flow cytometry revealed an increase in the fraction of cells in the G2/M phase of the cell cycle, particularly for SW620 cells. Growth inhibition was apparently not caused by increased lipid peroxidation, reduced glutathione or low activity of glutathione peroxidase. Transmission electron microscopy revealed formation of cytoplasmic lipid droplets after DHA treatment. In SW620 cells an eightfold increase in total cholesteryl esters and a 190-fold increase in DHA-containing cholesteryl esters were observed after DHA treatment. In contrast, SW480 cells accumulated DHA-enriched triglycerides. Arachidonic acid accumulated in a similar manner, whereas the nontoxic oleic acid was mainly incorporated in triglycerides in both cell lines. Interestingly, nuclear sterol regulatory element-binding protein 1 (nSREBP1), recently associated with cell growth regulation, was downregulated after DHA treatment in both cell lines. Our results demonstrate cell-specific mechanisms for the processing and storage of cytotoxic PUFAs in closely related cell lines, and suggest downregulation of nSREBP1 as a possible contributor to the growth inhibitory effect of DHA.

Toxicity of fatty acids on murine and human melanoma cell lines

High concentrations of certain fatty acids can cause cell death via apoptosis or necrosis. The aim of this study was to investigate the toxicity of saturated and unsaturated fatty acids on melanoma cell lines, which was evaluated by either loss of membrane integrity and/or DNA fragmentation using flow cytometric analysis. Evidence is presented that saturated and unsaturated fatty acids exert toxic effects on melanoma cells through loss of membrane integrity and/or DNA fragmentation. Arachidonic and linoleic acids were the most effective in decreasing the number of viable S91 murine melanoma cells, causing loss of membrane integrity and DNA fragmentation at 100 microM concentration already after 24 h in culture. In B16F10 murine melanoma cells, palmitic acid was the most toxic, inducing cell death by both apoptosis and necrosis. The human melanoma cell lines were more resistant to the toxic effect of fatty acids. In SK-Mel 23 cells, indications of cytotoxicity were detected only after 48 h treatment with arachidonic, linoleic, palmitic and palmitoleic acids at 200 microM concentration. Linoleic acid was the most toxic for this cell line. In SK-Mel 28 human cells, only palmitic acid caused a significant decrease of the number of viable cells, inducing DNA fragmentation after 24 and 48 h treatments at 200 microM concentration.

Prostaglandin EP receptors: Targets for treatment and prevention of colorectal cancer?

The importance of the prostaglandin (PG) synthesis pathway, particularly the rate-limiting enzymatic step catalyzed by cyclooxygenase, to colorectal carcinogenesis and development of novel anticolorectal cancer therapy is well established. The predominant PG species in benign and malignant colorectal tumors is PGE2. PGE2 acts via four EP receptors termed EP1 to EP4. Recently, EP receptors have been identified as potential targets for treatment and/or prevention of colorectal cancer. This review summarizes existing knowledge of the expression and function of the EP receptor subtypes in human and rodent intestine during tumorigenic progression and describes the current literature on targeting EP receptor signaling during intestinal tumorigenesis.

The role of long-chain fatty-acid-CoA ligase 3 in vitamin D3 and androgen control of prostate cancer LNCaP cell growth

The antiproliferative effect of 1alpha,25(OH)(2)D(3) on human prostate cancer cells is well known, but the mechanism is still not fully understood, especially its androgen-dependent action. Based on cDNA microarray results, we found that long-chain fatty-acid-CoA ligase 3 (FACL3/ACS3) might play an important role in vitamin D(3) and androgen regulation of LNCaP cell growth. The expression of FACL3/ACS3 was found to be significantly upregulated by 1alpha,25(OH)(2)D(3) and the regulation was shown to be time-dependent, with the maximal regulation over 3.5-fold at 96h. FACL3/ACS3 was a dominant isoform of FACL/ACS expressed in LNCaP cells as indicated by measuring the relative expression of each isoform. 1alpha,25(OH)(2)D(3) had no significant effect on the expression of FACL1(FACL2), FACL4 and FACL6 except for its downregulation of FACL5 at 24 and 48h by around twofold. The upregulation of FACL3/ACS3 expression by 1alpha,25(OH)(2)D(3) was accompanied with increased activity of FACL/ACS as demonstrated by enzyme activity assay using a (14)C-labeled substrate preferential for FACL3/ACS3. The growth inhibitory effect of 1alpha,25(OH)(2)D(3) on LNCaP cells was significantly attenuated by FACL3/ACS3 activity inhibitor. Androgen withdrawal (DCC-serum), in the presence of antiandrogen Casodex or in AR-negative prostate cancer cells (PC3 and DU145), vitamin D(3) failed to regulate FACL3/ACS3 expression. The upregulation of FACL3/ACS3 expression by vitamin D(3) was recovered by the addition of DHT in DCC-serum medium. Western blot analysis showed that the expression of androgen receptor (AR) protein was consistent with vitamin D(3) regulation of FACL3/ACS3 expression. Taken together, the data suggest that the upregulation of FACL3/ACS3 expression by vitamin D(3) is through an androgen/AR-mediated pathway and might be one of the contributions of the vitamin D(3) antiproliferative effect in prostate cancer LNCaP cells.

Effects of fatty acids on the growth of Caco-2 cells

Epidemiological studies suggest that polyunsaturated fatty acids may protect against colorectal neoplasia. In order to explore this observation, cell proliferation and viability, lipid composition, membrane fluidity, and lipid peroxidation were measured in Caco-2 cells after 48h incubation with various fatty acids. Saturated and monounsaturated fatty acids incorporated less well in the membranes than polyunsaturated fatty acids (PUFAs). All of the PUFAs tested had an inhibitory effect on cell proliferation/viability whereas the saturated and monounsaturated fatty acids did not. Addition of palmitic acid had no significant effect on membrane fluidity whereas unsaturated fatty acids increased membrane fluidity in a dose-dependent manner. PUFAs strongly increased tumor cell lipid peroxidation in a dose-dependent manner. Saturated and monounsaturated fatty acids increased lipid peroxidation in this cell line only at high concentration. Preincubation of Caco-2 cells with vitamin E prevented the inhibition of proliferation/viability, the elevation of the MDA concentration and the increased membrane fluidity induced by PUFAs. Our data indicate that PUFAs are potent inhibitors of the growth of colon cancer cells in vitro.

Association between E-cadherin expression by human colon, bladder and breast cancer cells and the 13-HODE:15-HETE ratio. A possible role of their metastatic potential

The relationship between 15(S)-HETE and 13(S)-HODE from different human tumor cells exposed to n-6 and n-3 essential fatty acids (EFAs) and E-cadherin expression was studied. Colon cancer cells (HRT-18) exposed to gamma linoleic acid (18:3n-6, GLA) and eicosapentaenoic (20:5n-3, EPA) (50microM) showed an increased expression of E-cadherin. Breast cancer (MCF-7) exposed to EPA showed an increment whereas GLA had no effect on E-cadherin expression. No expression of E-cadherin was observed for urothelial cancer (T-24) after GLA or EPA treatment. Significant levels of 15(S)-HETE and 13(S)-HODE were detected after GLA or EPA treatment for all tumor lines. E-cadherin expression was inversely proportional to the 13(S)-HODE:15(S)-HETE ratio when cells were pretreated with GLA or EPA. Nevertheless, the liberation of these metabolites seems to be independent of the E-cadherin expression. The increase in the13(S)-HODE:15(S)-HETE correlates to a decrease in the expression of E-cadherin. Both factors may play a role in metastasis development.

Enhancement of lipid peroxidation and of the antitumor effect of hyperthermia upon combination with oral eicosapentaenoic acid

The present study was designed to determine the effect of eicosapentaenoic acid (EPA) on the susceptibility of tumor cells to treatments that kill the cells by lipid peroxidation. Using AH109A carcinoma, a rat liver cancer, we measured EPA content, levels of antioxidants, and degree of lipid peroxidation in tumor tissue and normal liver tissue after oral administration of EPA. In the control group treated with distilled water, EPA in tumor tissue was lower than in normal liver tissue, suggesting that its content of polyunsaturated fatty acids (the substrates for lipid peroxidation) was inherently low. Levels of antioxidants also tended to be lower in tumor tissue. EPA level increased in both tumor and normal tissues after oral administration of EPA. At the same time, glutathione peroxidase (GSH-Px) increased in normal tissue, whereas tumor tissue displayed no increase in antioxidants; instead GSH decreased. The EPA-induced change in balance between substrates for lipid peroxidation and antioxidants suggested that tumor tissue might become more susceptible to lipid peroxidation than normal liver tissue. In fact, hyperthermia treatment did enhance lipid peroxidation and antitumor action. Our results indicate that oral EPA specifically increases the susceptibility of liver tumor tissue to lipid peroxidation, and hence enhance the antitumor effect of hyperthermia and prolongs survival.

Dietary n-6 and n-3 polyunsaturated fatty acids and colorectal carcinogenesis: results from cultured colon cells, animal models and human studies

During the past few decades, many studies have been conducted to evaluate the effects of n-6 and n-3 polyunsaturated fatty acids (PUFAs) on colorectal carcinogenesis. This report provides a brief overview of the recent studies that have been performed in cultured colon cells, animal models as well as of the population-based and short-term biomarker studies with humans. No differential effect between n-6 and n-3 PUFAs has been observed in vitro. Results from animal models indicate that n-6 PUFAs have a tumor enhancing effect, predominantly during the post-initiation phase. n-3 PUFAs may protect against colorectal carcinogenesis during both the initiation and post-initiation phase. Population-based human studies show little or no associations between n-6 or n-3 PUFA intake and colorectal cancer. Short-term biomarker studies in humans suggest though that fish oil (FO) supplementation with high amounts of n-3 PUFAs may protect against colorectal carcinogenesis and that n-6 PUFA supplementation may increase the risk.

Decreased production of insulin-like growth factor-binding protein (IGFBP)-6 by transfection of colon cancer cells with an antisense IGFBP-6 cDNA construct leads to stimulation of cell proliferation

BACKGROUND

: Previously, we have observed that highly unsaturated dietary (n-3) fatty acids inhibit cell proliferation in conjunction with stimulation of insulin-like growth factor-binding protein (IGFBP)-6 secretion in Caco-2 cells, a human colon carcinoma cell line.

METHODS

: To test the converse hypothesis that inhibition of endogenous IGFBP-6 secretion stimulates Caco-2 cell proliferation, cells were transfected with the antisense IGFBP-6 expression construct or pcDNA3 vector only, and single colonies resistant to G418 sulfate were isolated.

RESULTS

: Our initial studies indicated that three antisense clones grew faster and produced less IGFBP-6 than two pcDNA3 clones, so antisense IGFBP-6 #5 and pcDNA3 #8 were selected for further detailed analysis. Both the control and antisense clones grew in serum-free medium reaching a plateau density at day eight. However, the antisense clone grew at a rate faster than that of the control and reached a final density that was 31 +/- 3% higher than the control. Northern blot, ligand blot and immunoblot analyses revealed that accumulation of IGFBP-6 mRNA and concentrations of IGFBP-6 peptide produced by the antisense clone were decreased by 80-90% compared to the control. The doubling times of the antisense and control clones were 21.9 +/- 0.4 and 24.8 +/- 0.3 h (P < 0.05), respectively. Exogenous IGF-I and IGF-II (0.2-200 nmol/L) stimulated proliferation of both the control and antisense clones in a dose-dependent manner, but the relative potency and efficacy of IGF-II was higher in the antisense clone compared to the control. These results indicate that suppression of IGFBP-6 secretion correlates with an increase in the basal rate of Caco-2 cell growth.

CONCLUSIONS

: Our findings are consistent with the hypothesis that IGFBP-6 inhibits cell growth by binding to endogenously produced IGF-II, thereby preventing IGF-II from interacting with the IGF-I receptor to stimulate cellular proliferation by an autocrine mechanism.

Effect of fatty acids on estradiol and testosterone binding to whole DU-145 prostate cells

Cancer of the prostate is one of the leading causes of cancer related deaths in men. An important role in the development of prostate cancer is played by androgens and androgen ablation is therefore currently used in cancer treatment. In the past, estrogens were widely used in treatment of prostate cancer, but there are indications that estrogens could also be involved in carcinogenesis. Lately, much research has been done on the modulation of the binding of steroid hormones to their receptors by polyunsaturated fatty acids (PUFAs), which could interfere with the steroid hormone's message. Therefore, the aim of this study was to determine in whole DU-145 human prostate cells the effect of EFAs and their metabolites on the binding and affinity of the estrogen receptor (ER) and androgen receptor (AR) to estradiol (E(2)) and testosterone (T), respectively. Fatty acids were dissolved in ethanol and added to the cell culture in a final ethanol concentration of 0.2% on the fourth day of incubation. The results showed that the PUFAs under investigation inhibited the AR's capacity, in contrast to the ER's capacity which was stimulated. However, the dissociation constants (K(d)) of the AR and ER complexes in the presence of the PUFAs, were as follows. Except for eicosapentaenoic acid (EPA) which decreased the AR dissociation constant and EPA and alpha-linolenic acid (ALA) which increased the ER dissociation constant, the remaining FAs had no significant effect on the K(d) values of both the AR and ER complexes. According to these priliminary results it is postulated that men should benefit with a diet rich in certain essential polyunsaturated fatty acids although its function remains to be clarified.

Necrosis and apoptosis in lymphoma cell lines exposed to eicosapentaenoic acid and antioxidants

The present study is focused on the role of oxidative stress in the induction of either necrosis or apoptosis by eicosapentaenoic acid (EPA) in the lymphoma cell lines Raji and Ramos, respectively. To investigate the different death modes induced by EPA, we assessed the importance of some antioxidants and reactive oxygen species in the two cell lines. We observed that different antioxidants counteracted the necrotic effect of EPA on Raji cells to a different extent, and that vitamin E counteracted EPA-induced accumulation of superoxide anion in this cell line. On the contrary, no effects of antioxidants were observed on development of apoptosis induced by EPA in Ramos cells, and vitamin E did not counteract EPA-induced accumulation of superoxide anions in Ramos cells. Moreover, apoptosis was partly inhibited by transcription inhibitors (actinomycin D) and protein synthesis inhibitors (cycloheximide), suggesting dependency upon new protein synthesis prior to apoptosis. Kinase inhibitors (staurosporin and calphostin C) did not alter the EPA-induced apoptosis. The observed cellular accumulation of superoxide anion following EPA incubation may be important for induction of necrosis in Raji cells. In contrast, none of the other investigated parameters indicated a role of oxidative stress promoted by EPA in the induction of apoptosis in Ramos cells.

Tolerance and incorporation of a high-dose eicosapentaenoic acid diester emulsion by patients with pancreatic cancer cachexia

Chemotherapy and radiotherapy offer little benefit to patients with advanced pancreatic cancer. Eicosapentaenoic acid (EPA) has anticancer effects both in vitro and in animal models. The dose of EPA that can be administered to cancer patients has previously been limited by the low purity of available preparations and the tolerability of large capsules. A high-purity preparation of EPA as a 20% oil-in-water diester emulsion allowed a small study of the tolerance, incorporation, and effects of EPA in high doses in five patients with advanced pancreatic cancer. Patients underwent assessment at baseline and every 4 wk thereafter. All patients managed to tolerate a dose providing 18 g EPA per day, with doses between 9 and 27 g daily being taken for at least a month. Dosage was limited by a sensation of fullness, cramping abdominal pain, steatorrhea, and nausea. All such symptoms were controlled by dose reduction or pancreatic enzyme supplements. No other adverse effects attributable to the trial agent were observed. Plasma phospholipid EPA content increased from around 1% at baseline to 10% at 4 wk and 20% at 8 wk. Incorporation of EPA into red blood cell phospholipids reached levels of around 10%. The present study has shown that a novel, high-purity, EPA diester emulsion can be tolerated at a dose providing around 18 g EPA per day with side-effects being easily controlled. The acceptibility of large doses of oral EPA should allow larger controlled clinical studies into potential anticancer effects of EPA.

Effect of 1-(gamma)linolenyl-3-eicosapentaenoyl propane diol on the growth of human pancreatic carcinoma in vitro and in vivo

Essential fatty acids such as (gamma)linolenic (GLA) and eicosapentaenoic (EPA) acids have been proposed as anticancer drugs. The aim of this study was to test the effect of a lipid emulsion containing both GLA and EPA in a novel chemical formulation of 1-(gamma)linolenyl-3-eicosapentaenoyl propane diol on the growth of human pancreatic carcinoma in vitro and in nude mice. This compound had a dose-dependent growth-inhibitory effect on human pancreatic cancer cell lines MIA PaCa-2 and Panc-1 in vitro. The concentration necessary for 50% growth inhibition was 25 micromol/l for MIA PaCa-2 and 68 micromol/l for Panc-1 (95% CI 20-29 and 59-77 micromol/l respectively). Nude mice bearing subcutaneous pancreatic tumours produced with the MIA PaCa-2 cell line were treated with the maximum tolerated dose (6.75 mg GLA and 7.3 mg EPA per g of body weight) administered over 10 days by daily intravenous (i.v.) bolus injections. No antitumour effect or major alteration in tumour lipid fatty acid composition was seen in comparison with control animals. Concurrent treatment with parenteral iron (iron saccharate, 5 microg/gram body weight daily) did not make a significant difference. Further improvements in fatty acid delivery mechanisms are necessary before they can become useful anticancer agents.

Incorporation of polyunsaturated fatty acids into CT-26, a transplantable murine colonic adenocarcinoma

Previous studies in our laboratory have shown that marine oils, with high levels of eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic acids (DHA, 22:6n-3), inhibit the growth of CT-26, a murine colon carcinoma cell line, when implanted into the colons of male BALB/c mice. An in vitro model was developed to study the incorporation of polyunsaturated fatty acids (PUFA) into CT-26 cells in culture. PUFA-induced changes in the phospholipid fatty acid composition and the affinity with which different fatty acids enter the various phospholipid species and subspecies were examined. We found that supplementation of cultured CT-26 cells with either 50 microM linoleic acid (LIN, 18:2n-6), arachidonic acid (AA, 20:4n-6), EPA, or DHA significantly alters the fatty acid composition of CT-26 cells. Incorporation of these fatty acids resulted in decreased levels of monounsaturated fatty acids, while EPA and DHA also resulted in lower levels of AA. While significant elongation of both AA and EPA occurred, LIN remained relatively unmodified. Incorporation of radiolabeled fatty acids into different phospholipid species varied significantly. LIN was incorporated predominantly into phosphatidylcholine and had a much lower affinity for the ethanolamine phospholipids. DHA had a higher affinity for plasmenylethanolamine (1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine) than the other fatty acids, while EPA had the highest affinity for phosphatidylethanol-amine (1,2-diacyl-sn-glycero-3-phosphoethanolamine). These results demonstrate that, in vitro, significant differences are seen between the various PUFA in CT-26 cells with respect to metabolism and distribution, and these may help to explain differences observed with respect to their effects on tumor growth and metastasis in the transplantable model.

Effect of eicosapentaenoic acid on the proliferation and incidence of apoptosis in the colorectal cell line HT29

Fish oil has been shown to reduce the induction of colorectal cancer in animal models by a mechanism which may involve suppression of mitosis, increased apoptosis, or both. We used the human colonic adenocarcinoma cell line HT29 to explore the effects of the long-chain n-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) on cell proliferation and death in vitro. Cells were cultured in media containing EPA at 5, 10, and 15 microg/mL. Cell number and thymidine incorporation were used to quantify proliferation, and cell cycle effects were studied using flow cytometry. Gel electrophoresis, annexin-V binding, and morphological criteria were used to characterize apoptosis. Adherent cells and freely floating detached cells were treated as two distinct populations. In the presence of EPA at 10 and 15 microg/mL there was a marked reduction in the growth rate of adherent HT29 colonies, owing to an increased detachment of adherent cells. After treatment with 10 or 15 microg/mL EPA the proportion of adherent cells in S-phase increased, indicating either a block in late S-phase or early G2. Floating cells showed evidence of extensive DNA cleavage, but the proportion of floating cells with sub GO DNA content declined on treatment with 10 or 15 microg/mL EPA even though the number of floating cells increased. We conclude that EPA does not inhibit mitosis of adherent cells, but increases the rate at which they become detached from the substrate, probably at an early stage in the initiation of apoptosis. This mechanism may be analogous to "anoikis," or induction of apoptosis in response to loss of cell contact, and may contribute to the anticarcinogenic effects of fish oil in vivo.

Both (n-3) and (n-6) fatty acids stimulate wound healing in the rat intestinal epithelial cell line, IEC-6

The control of proliferation and epithelial restitution are processes that are poorly understood. The effects of (n-3), (n-6) and trans fatty acids on proliferation of subconfluent IEC-6 cultures and restitution of wounded IEC-6 monolayers were investigated. Incorporation of supplemented fatty acids into cellular phospholipid was also assessed. Sulforhodamine B protein dye binding assay was utilized to assess the proliferative effects of fatty acids on growth of IEC-6 cultures. Incorporation of supplemental fatty acids into cellular phospholipid was examined by thin-layer chromatography combined with gas chromatography. The modulation of epithelial restitution was examined by razor blade wounding confluent IEC-6 monolayers grown in media supplemented with various fatty acids. Inhibition of eicosanoid synthesis by indomethacin during the wounding assay was also assessed. Both (n-3) and (n-6) fatty acids significantly inhibited growth of this intestinal epithelial cell model at concentrations above 125 micromol/L. The trans fatty acid, linoelaidate 18:2(n-6)trans, inhibited growth of IEC-6 cells at concentrations above 250 micromol/L. Another trans fatty acid, elaidate 18:1(n-9)trans, was well-tolerated at concentrations as high as 500 micromol/L. Eicosapentanoic 20:5(n-3), linoleic 18:2(n-6), alpha-linolenic 18:3(n-3), gamma-linolenic 18:3(n-6) and arachidonic 20:4(n-6) acids all significantly enhanced cellular migration in the IEC-6 model of wound healing. Eicosapentanoate, linoleate, alpha-linolenate, gamma-linolenate and arachidonate are all capable of improving reconstitution of epithelial integrity following mucosal injury. Inhibition of eicosanoid synthesis reduced the enhancement of restitution by n-6 fatty acids back to control levels.

Growth inhibitory effect of lithium gammalinolenate on pancreatic cancer cell lines: the influence of albumin and iron

Essential fatty acids, especially gamma linolenic (GLA) and eicosapentaenoic acids, have been proposed as potential anticancer drugs. Our aim was to study the effect of the lithium salt of gamma linolenic acid (LiGLA) on the growth of two human pancreatic cancer cell lines (MIA PaCa2 and Panc 1) and primary human fibroblasts (HFF 5) in vitro. Cell growth was assessed by a microculture tetrazolium (MTT) assay. LiGLA had a selective growth inhibitory effect on pancreatic cancer cell lines with 50% growth inhibition (IC50) at approximately 6-16 mumol/l compared with approximately 111 mumol/l for the fibroblasts. The degree of growth inhibition increased with the time of exposure to LiGLA. Special attention was paid to the influence of albumin and iron on LiGLA-mediated growth inhibition. Albumin incorporated into essentially serum-free culture medium inhibited the effect of LiGLA in a dose-dependent manner, associated with reduced GLA uptake by cancer cells. Ferric ions were confirmed as potentiators of the growth inhibitory effect of LiGLA but more physiologically relevant transferrin-bound iron was ineffective. With further improvements in the fatty acid delivery mechanism, LiGLA may become a useful adjunct in the management of pancreatic cancer patients.

Prostaglandin H synthase expression is variable in human colorectal adenocarcinoma cell lines

The expression of prostaglandin H synthases can be induced by many stimuli and is likely to be important in control of the cell cycle. The analysis of prostaglandin H synthase-1 and -2 expression in colon adenocarcinoma cell lines is a useful model system for studying the function of the prostaglandin H synthases, especially with regard to proliferation and adhesion. Prostaglandin H synthase-1 protein is not found in any of eight human colon adenocarcinoma cell lines. Expression of prostaglandin H synthase-2 is variable for the eight cell lines: three constitutively expressed active protein, four did not express this gene at all, and one had mRNA but no active protein. Thus, five colorectal adenocarcinoma cell lines exhibit "null" expression of prostaglandin synthase-2. The three cell lines with constitutive expression of prostaglandin H synthase-2 produce PGE2. Prostaglandin E2 production could be inhibited by aspirin and NS398 without inhibiting proliferation, while direct addition of prostaglandin E2 inhibits proliferation. Adhesion to collagen IV and fibronectin was stronger in those cell lines that expressed prostaglandin H synthase-2. The constitutive expression of prostaglandin H synthase-2 is associated with increased adhesion to extracellular matrix components and a potential inhibition of proliferation through the production of prostaglandin E2. The absence of PGH synthase-2 expression in some cell lines may result from the original tumor's need to inactivate these associated functions. Our evidence suggests that PGH synthase-2 is a possible candidate for a tumor suppressor gene at 1q23-qter.

Nutritional pharmacology and malignant disease: a therapeutic modality in patients with cancer

It is now established that certain nutrients have a significant effect on cellular metabolism and growth, tissue repair and regeneration, and modulation of host defences. So far, however, potential clinical benefits have been difficult to demonstrate. Nevertheless, the use of nutrients in combinations seems to have promise and may be associated with a reduction in infectious complications and length of hospital stay. Nutritional pharmacology in the future may be able to improve tumour response to chemotherapy and may minimize the metabolic effect of cachexia.

Selected eicosanoids increase the proliferation rate of human colon carcinoma cell lines and mouse colonocytes in vivo

Eicosanoids have been implicated in colon carcinogenesis, but their role remains unclear. The levels of PGE2 are elevated in colon cancer tissues and in blood draining colon tumors. The effect of eicosanoids on the proliferation of colonic cells is unknown. We studied the effect of several prostaglandins (PGs) and leukotriene (LT)B4 on the proliferation rate of the human colon adenocarcinoma cell lines SW1116 and HT-29 and of 16,16-dimethyl PGE2 (dmPGE2) on the colon of BALB/c mice. PGs E2, F2 alpha, I2, the methyl ester of PGE2, dmPGE2, and LTB4 (10(-10), 10(-8), 10(-6) M), administered for up to 72 h, stimulated cell proliferation in SW1116 cells and all but PGF2 alpha and PGI2 stimulated proliferation in HT-29 cells. The proliferative effect was time- and concentration-dependent. However, in SW1116 cells the response to PGs was 'bell-shaped', being maximal at 10(-8) M, with the 10(-10) and 10(-6) M concentrations being less effective. In HT-29 cells, the addition of methyl groups to the PGE2 molecule increased the proliferative effect. None of these eicosanoids affected the distribution of these cells in the cell cycle or their rate of programmed cell death (apoptosis). dmPGE2 stimulated 3.6-fold the proliferation of colonocytes in normal BALB/c mice. This was determined by bivariate flow cytometric analysis of the expression of proliferating cell nuclear antigen (PCNA) in virtually pure populations of mouse colonocytes. dmPGE2 did not alter the cell cycle distribution of these cells. We conclude that several PGs as well as LTB4 stimulate the proliferation of human colon carcinoma cells in vitro, while dmPGE2 has a similar effect on mouse colonocytes in vivo. These findings raise the possibility that eicosanoids may contribute to colonic carcinogenesis by stimulating the proliferation rate of tumor cells in the colon.

Effects of gamma-linolenic and dihomo-gamma-linolenic acids on 7,12-dimethylbenz(alpha)anthracene-induced mammary tumors in rats

The effects of pure gamma-linolenic acid (GLA; C18:3, n-6) and dihomo-gamma-linolenic acid (DGLA; C20:3, n-6) were investigated in 7,12-dimethylbenz(alpha)anthracene (DMBA) (10 mg/rat)-induced mammary tumors in Sprague-Dawley rats. 0.15 g of GLA, DGLA, or corn oil (CO) were administered (two times per week) by oral intubation, for 12 weeks to rats maintained on a 5% (w/w) CO diet. Tumor incidence, tumor multiplicity, and percent of tumor-bearing rats were highest in the CO group. Tumor multiplicity was significantly reduced in the GLA group (p = 0.015). Feeding of GLA and DGLA resulted in significant alterations in levels of these fatty acids in phospholipids of mammary tissue, thymus, colon, liver, stomach, and ovary. These results suggest that GLA may have a small, but significant, inhibitory effect on the development of DMBA-induced mammary tumors in rats.

Effects of linoleic acid and gamma-linolenic acid on the growth and metastasis of a human breast cancer cell line in nude mice and on its growth and invasive capacity in vitro

It has been reported that gamma-linolenic acid (GLA)-rich diets suppress mammary carcinogenesis and transplanted tumor growth and that GLA inhibits the growth of cultured human cancer cell lines. We compared the effects of dietary GLA and linoleic acid (LA) on the growth of MDA-MB-435 human breast cancer cells and their expression of the metastatic phenotype in vivo and in vitro. Athymic nude mice (30/dietary group) were fed isocaloric diets containing 20% (wt/wt) fat but providing 8% GLA or LA for 7 days, and 10(6) tumor cells were then injected into a thoracic mammary fat pad. The diets were continued for a further 11 weeks. The primary tumor growth rates were similar in mice from the two dietary groups; there was a nonstatistically significant trend for the incidence of macroscopic lung metastases and the total lung metastatic volumes to be higher in the GLA-fed mice (79% and 40.1 +/- 13.9 mm3) than in the LA-fed mice (64% and 15.5 +/- 5.4 mm3). The tumor cell phospholipids from the 8% GLA-fed mice contained significantly lower LA levels but higher arachidonic acid levels (both p < 0.001) than those from 8% LA-fed mice. Also the arachidonate-derived eicosanoids (prostaglandin E, leukotriene B4, and 5-, 12-, and 15-hydroxyeicosatetraenoic acids) were significantly higher in tumors from the 8% GLA group. Zymography showed higher 92-kDa type IV collagenase activity in tumors from 8% GLA-fed mice. In vitro, GLA and LA, at 0.5-2 micrograms/ml, stimulated MDA-MB-435 cell growth; 10 micrograms/ml was mildly inhibitory. Whereas LA stimulated tumor cell invasion and 92-kDa type IV collagenase production in vitro, GLA inhibited invasion and did not induce activity of the proteolytic enzyme. Our results do not support the hypothesis that supplementation with GLA would exert a beneficial effect on the progression of an existing breast cancer, perhaps because it is metabolized in vivo to arachidonate-derived eicosanoids that are known to be involved in the metastatic process.

Do Escherichia coli susceptibilities to various antibiotics decrease in the presence of polyunsaturated fatty acids? A preliminary report

Polyunsaturated fatty acids (PUFAs) constitute an ingredient of the daily diet and therefore they might be in close contact with the polymicrobial gastrointestinal flora. In order to study the interaction of bacteria and PUFAs, eight Escherichia coli strains were cultured in the presence of docosahexaenoic acid (DHA) at a concentration of 100 micrograms/ml, and six of the latter eight at 75 micrograms/ml whereas nine other E. coli strains were cultured in the presence of 50 micrograms/ml gamma-linolenic acid (GLA). DHA provoked > or = 4-fold increases in the minimum inhibitory and bactericidal concentrations of various antibiotics in six strains at 100 micrograms/ml and in three strains at 75 micrograms/ml, which were not antibiotic-specific and involved mainly aminoglycosides. GLA provoked in four strains > or = 4-fold increases in MICs-MBCs of ampicillin. The clinical relevance of these observations require further study.