Polyunsaturated fatty acids sensitize human colon adenocarcinoma HT-29 cells to death receptor-mediated apoptosis

Poly-Unsaturated Fatty Acids (PUFAs) from Cunninghamella elegans Grown on Glycerol Induce Cell Death and Increase Intracellular Reactive Oxygen Species

Cunninghamella elegans NRRL-1393 is an oleaginous fungus able to synthesize and accumulate unsaturated fatty acids, amongst which the bioactive gamma-linolenic acid (GLA) has potential anti-cancer activities. C. elegans was cultured in shake-flask nitrogen-limited media with either glycerol or glucose (both at ≈60 g/L) employed as the sole substrate. The assimilation rate of both substrates was similar, as the total biomass production reached 13.0-13.5 g/L, c. 350 h after inoculation (for both instances, c. 27-29 g/L of substrate were consumed). Lipid production was slightly higher on glycerol-based media, compared to the growth on glucose (≈8.4 g/L vs. ≈7.0 g/L). Lipids from C. elegans grown on glycerol, containing c. 9.5% w/w of GLA, were transformed into fatty acid lithium salts (FALS), and their effects were assessed on both human normal and cancerous cell lines. The FALS exhibited cytotoxic effects within a 48 h interval with an IC50 of about 60 μg/mL. Additionally, a suppression of migration was shown, as a significant elevation of oxidative stress levels, and the induction of cell death. Elementary differences between normal and cancer cells were not shown, indicating a generic mode of action; however, oxidative stress level augmentation may increase susceptibility to anticancer drugs, improving chemotherapy effectiveness.

Molecular Mechanisms Associated with the Inhibitory Role of Long Chain n-3 PUFA in Colorectal Cancer

Colorectal cancer (CRC) is the third leading cause of cancer-related death in the world. Multiple evidence suggests that there is an association between excess fat consumption and the risk of CRC. The long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential for human health, and both in vitro and in vivo studies have shown that these fatty acids can prevent CRC development through various molecular mechanisms. These include the modulation of arachidonic acid (AA) derived prostaglandin synthesis, alteration of growth signaling pathways, arrest of the cell cycle, induction of cell apoptosis, suppression of angiogenesis and modulation of inflammatory response. Human clinical studies found that LC n-3 PUFA combined with chemotherapeutic agents can improve the efficacy of treatment and reduce the dosage of chemotherapy and associated side effects. In this review, we discuss comprehensively the anti-cancer effects of LC n-3 PUFA on CRC, with a main focus on the underlying molecular mechanisms.

The Involvement of Polyunsaturated Fatty Acids in Apoptosis Mechanisms and Their Implications in Cancer

Cancer is a significant global public health issue and, despite advancements in detection and treatment, the prognosis remains poor. Cancer is a complex disease characterized by various hallmarks, including dysregulation in apoptotic cell death pathways. Apoptosis is a programmed cell death process that efficiently eliminates damaged cells. Several studies have indicated the involvement of polyunsaturated fatty acids (PUFAs) in apoptosis, including omega-3 PUFAs such as alpha-linolenic acid, docosahexaenoic acid, and eicosapentaenoic acid. However, the role of omega-6 PUFAs, such as linoleic acid, gamma-linolenic acid, and arachidonic acid, in apoptosis is controversial, with some studies supporting their activation of apoptosis and others suggesting inhibition. These PUFAs are essential fatty acids, and Western populations today have a high consumption rate of omega-6 to omega-3 PUFAs. This review focuses on presenting the diverse molecular mechanisms evidence in both in vitro and in vivo models, to help clarify the controversial involvement of omega-3 and omega-6 PUFAs in apoptosis mechanisms in cancer.

ω-3 and ω-6 Polyunsaturated Fatty Acids Regulate the Proliferation, Invasion and Angiogenesis of Gastric Cancer Through COX/PGE Signaling Pathway

Background

This study aims to investigate the effects of ω-3, ω-6 polyunsaturated fatty acids (PUFAs), and their middle metabolites prostaglandin (PGE)2 and PGE3 on proliferation, invasion, and angiogenesis formation of gastric cancer cells and to explore associated mechanism.

Methods

RT-PCR and ELISA were used to detect the expression of cyclooxygenase (COX)-1 and COX-2 in gastric cancer cell lines. The effect of ω-3, ω-6, PGE2, and PGE3 on the proliferation, invasion, and angiogenesis of gastric cancer cells were measured by cell proliferation, invasion, and angiogenesis assay in vitro. COX-2 small interfering RNA (siRNA) was transfected into gastric cancer cells, and the expression of COX-2 protein was detected by Western blot. COX-2 gene silencing influencing proliferation, invasion, and angiogenesis potential of gastric cancer cells was detected by WST-1, transwell chamber, and angiogenesis assay, respectively.

Results

COX-2 was only expressed in MKN74 and MKN45 cells. In gastric cancer cell lines with positive COX-2 expression, ω-6 and PGE2 could significantly enhance the proliferation, invasion, and angiogenesis of gastric cancer cells, and after transfection with COX-2 siRNA, the effects of ω-6 and PGE2 on enhancing the proliferation, invasion, and angiogenesis of gastric cancer cells were significantly attenuated; ω-3 and PEG3 could inhibit the proliferation, invasion, and angiogenesis of gastric cancer cells. In gastric cancer cell lines with negative COX-2 expression, ω-6 and PGE2 had no significant effect on the proliferation, invasion, and angiogenesis of gastric cancer; ω-3 and PGE3 could significantly inhibit the proliferation, invasion, and angiogenesis of gastric cancer.

Conclusion

ω-6 PUFAs reinforce the metastatic potential of gastric cancer cells via COX-2/PGE2; ω-3 PUFAs inhibit the metastatic potential of gastric cancer via COX-1/PGE3 signaling axis.

Omega-3 Polyunsaturated Fatty Acids and the Intestinal Epithelium-A Review

Epithelial cells (enterocytes) form part of the intestinal barrier, the largest human interface between the internal and external environments, and responsible for maintaining regulated intestinal absorption and immunological control. Under inflammatory conditions, the intestinal barrier and its component enterocytes become inflamed, leading to changes in barrier histology, permeability, and chemical mediator production. Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) can influence the inflammatory state of a range of cell types, including endothelial cells, monocytes, and macrophages. This review aims to assess the current literature detailing the effects of ω-3 PUFAs on epithelial cells. Marine-derived ω-3 PUFAs, eicosapentaenoic acid and docosahexaenoic acid, as well as plant-derived alpha-linolenic acid, are incorporated into intestinal epithelial cell membranes, prevent changes to epithelial permeability, inhibit the production of pro-inflammatory cytokines and eicosanoids and induce the production of anti-inflammatory eicosanoids and docosanoids. Altered inflammatory markers have been attributed to changes in activity and/or expression of proteins involved in inflammatory signalling including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), peroxisome proliferator activated receptor (PPAR) α and γ, G-protein coupled receptor (GPR) 120 and cyclooxygenase (COX)-2. Effective doses for each ω-3 PUFA are difficult to determine due to inconsistencies in dose and time of exposure between different in vitro models and between in vivo and in vitro models. Further research is needed to determine the anti-inflammatory potential of less-studied ω-3 PUFAs, including docosapentaenoic acid and stearidonic acid.

Folium nelumbinis (Lotus leaf) volatile-rich fraction and its mechanisms of action against melanogenesis in B16 cells

This study was aimed at determining the influence of Folium nelumbinis (Lotus leaf) extracts on melanogenesis in vitro models of melanoma cell line. The anticancer activity of four fractions, including petroleum ether (PEE), n-hexane (HE), ethanol (EE), and ethyl acetate (EAE) from F. nelumbinis on B16 cell lines (C57BL/6J melanoma cell), were evaluated after 24 and 48 h treatment. Results showed that PEE as well as volatile-rich fractions of linolenic acid and linolenic acid ethyl ester significantly (p < 0.05) reduced tyrosinase activity and melanin content in B16 melanoma cells model. Meanwhile, PEE and its primarily contained compound triggered apoptosis of B16 cells in a dose-dependent way. These results demonstrated that PEE possessed effective activities against melanin and tyrosinase generations through the induction of apoptosis. Moreover, a relation between the volatile-rich fractions of F. nelumbinis and the anticancer effects was demonstrated as well.

Prospective clinical trial examining the impact of genetic variation in FADS1 on the metabolism of linoleic acid- and ɣ-linolenic acid-containing botanical oils

BACKGROUND

Unexplained heterogeneity in clinical trials has resulted in questions regarding the effectiveness of ɣ-linolenic acid (GLA)-containing botanical oil supplements. This heterogeneity may be explained by genetic variation within the fatty acid desaturase (FADS) gene cluster that is associated with circulating and tissue concentrations of arachidonic acid (ARA) and dihomo-ɣ-linolenic acid (DGLA), both of which may be synthesized from GLA and result in proinflammatory and anti-inflammatory metabolites, respectively.

OBJECTIVES

The objective of this study was to prospectively compare the capacity of a non-Hispanic white cohort, stratified by FADS genotype at the key single-nucleotide polymorphism (SNP) rs174537, to metabolize 18-carbon omega-6 (n-6) PUFAs in borage oil (BO) and soybean oil (SO) to GLA, DGLA, and ARA.

METHODS

Healthy adults (n = 64) participated in a randomized, double-blind, crossover intervention. Individuals received encapsulated BO (Borago officinalis L.; 37% LA and 23% GLA) or SO [Glycine max (L.) Merr.; 50% LA and 0% GLA] for 4 wk, followed by an 8-wk washout period, before consuming the opposite oil for 4 wk. Serum lipids and markers of inflammation (C-reactive protein) were assessed for both oil types at baseline and during weeks 2 and 4 of the intervention.

RESULTS

SO supplementation failed to alter circulating concentrations of any n-6 long-chain PUFAs. In contrast, a modest daily dose of BO elevated serum concentrations of GLA and DGLA in an rs174537 genotype-dependent manner. In particular, DGLA increased by 57% (95% CI: 0.38, 0.79) in GG genotype individuals, but by 141% (95% CI: 1.03, 2.85) in TT individuals. For ARA, baseline concentrations varied substantially by genotype and increased modestly with BO supplementation, suggesting a key role for FADS variation in the balance of DGLA and ARA.

CONCLUSIONS

The results of this study clearly suggest that personalized and population-based approaches considering FADS genetic variation may be necessary to optimize the design of future clinical studies with GLA-containing oils. This trial was registered at clinicaltrials.gov as NCT02337231.

Omega-3 fatty acid DHA modulates p53, survivin, and microRNA-16-1 expression in KRAS-mutant colorectal cancer stem-like cells

Background

The presence of chemotherapy-resistant colorectal cancer stem cells (CCSCs) with KRAS mutation is thought to be one of the primary causes for treatment failure in colorectal cancer (CRC). P53, survivin, and microRNA-16-1 are challenging targets for anticancer drugs which are associated with chemoresistance in CRC. Yet, no p53-, survivin-, and microRNA-16-1-modulating drug with low toxicity but high efficacy against KRAS-mutant CCSCs have been approved for clinical application in CRC. Here, we investigated whether in vitro concentrations of DHA equal to human plasma levels, are able to modulate, Wt-p53, survivin, and microRNA-16-1 in CRC cells with stem cell-like properties.

Methods

Wt-p53/KRAS-mutant CRC cells (HCT-116) with stem cell-like properties were treated with 100-, 150- and 200-μM/L DHA, after which cell number, viability, growth inhibition, Wt-p53, survivin and microRNA-16-1 expression, caspase-3 activation and apoptotic-rate were evaluated by different cellular and molecular techniques.

Results

After 24-, 48-, and 72-h treatments with 100- to 200-μM/L DHA, growth inhibition- rates were measured to be 54.7% to 59.7%, 73.% to 75.8%, and 63.3% to 97.7%, respectively. Treatment for 48 h with indicated DHA concentrations decreased cell number and viability. In addition, we observed a decrease in both the transcript and protein levels of survivin followed by 1.3- to 1.7- and 1.1- to 4.7-fold increases in the Wt-p53 accumulation and caspase-3 activation levels respectively. Treatment with 100 and 150 μM/L DHA increased microRNA-16-1 expression levels by 1.3- to 1.7-fold and enhanced the microRNA-16-1/survivin mRNA, p53/survivin, and caspase-3/survivin protein ratios by 1.7- to 1.8-, 1.3- to 2.6-, and 1.3- to 2-fold increases respectively. A decrease in the number of live cells and an increase in the number of apoptotic cells were also observed with increasing DHA concentrations.

Conclusion

Wt-p53, survivin, and microRNA-16-1 appear to be promising molecular targets of DHA. Thus, DHA might represent an attractive anti-tumor agent directed against KRAS-mutant CCSCs.

Apoptosis mediated chemosensitization of tumor cells to 5-fluorouracil on supplementation of fish oil in experimental colon carcinoma

5-Fluorouracil has been considered as a cornerstone therapy for colorectal cancer; however, it suffers from low therapeutic response rate and severe side effects. Therefore, there is an urgent need to increase the clinical efficacy of 5-fluorouracil. Recently, fish oil rich in n-3 polyunsaturated fatty acids has been reported to chemosensitize tumor cells to anti-cancer drugs. This study is designed to understand the underlying mechanisms of synergistic effect of fish oil and 5-fluorouracil by evaluation of tumor cell-associated markers such as apoptosis and DNA damage. The colon cancer was developed by administration of N,N-dimethylhydrazine dihydrochloride and dextran sulfate sodium salt. Further these animals were treated with 5-fluorouracil, fish oil, or a combination of both. In carcinogen-treated animals, a decrease in DNA damage and apoptotic index was observed. There was also a decrease in the expression of Fas, FasL, caspase 8, and Bax, and an increase in Bcl-2. In contrast, administration of 5-fluorouracil and fish oil as an adjuvant increased both DNA damage and apoptotic index by activation of both extrinsic and intrinsic apoptotic pathways as compared to the other groups. The increased pro-apoptotic effect by synergism of 5-fluorouracil and fish oil may be attributed to the incorporation of n-3 polyunsaturated fatty acids in membrane, which alters membrane fluidity in cancer cells. In conclusion, this study highlights that the induction of apoptotic pathway by fish oil may increase the susceptibility of tumors to chemotherapeutic regimens.

Apoptosis-Mediated Chemoprevention by Different Ratios of Fish Oil in Experimental Colon Carcinogenesis

Apoptosis plays an important role in prevention of colon cancer. In the present study, different ratios of fish oil and corn oil increased Fas expression in both phases and a decrease in FasL expression only in post initiation phase. Treatment with fish oil activated the intrinsic apoptotic pathway by increasing Bax expression and Cyt c release and decreasing Bcl-2 levels in both phases. This suggests that intrinsic pathway is upregulated by fish oil; however, Fas-FasL activity may be involved in inhibition of reversal of immune surveillance in tumor cells.

Treatment of LS174T colorectal cancer stem-like cells with n-3 PUFAs induces growth suppression through inhibition of survivin expression and induction of caspase-3 activation

PURPOSE

Colorectal cancer stem cells (CCSCs) are thought to contribute to tumor initiation, progression, metastasis, chemo-resistance and therapy failure. Therefore, assessment of the effectiveness of agents with anti-proliferative activities against CCSCs is warranted. Several studies have shown that different tumorigenic steps, ranging from initiation to metastasis, can be affected by n-3 polyunsaturated fatty acids (PUFAs). Here, we evaluated the effects of the PUFA components docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), alone or in combination, on LS174T cells that serve as a model for colorectal cancer initiating cells with stem cell-like properties.

METHODS

LS174T cells were treated with 50, 100 and 150 μM DHA and EPA, or equal mixtures of DHA/EPA (i.e., 25/25, 50/50 and 75/75 μM), after which cell number, viability, growth inhibition, survivin expression, caspase-3 activation and apoptotic rate were evaluated.

RESULTS

We found that treatment of LS174T cells with increasing PUFA concentrations significantly increased growth inhibition in a dose- and time-dependent manner. After a 72 h treatment with 150 μM DHA and EPA, or their combination (75/75 μM), growth rates were inhibited by 80.3 ± 5.5%, 79.3 ± 5% and 71.1 ± 1%, respectively, compared to untreated cells. We also found that treatment for 48 h with 100 μM DHA and EPA, or their combination (50/50 μM), resulted in 2.9-, 3- and 2.6-fold increases in caspase-3 activation, as well as 54, 62.4 and 100% decreases in survivin mRNA expression levels, respectively, compared to untreated cells. Low survivin mRNA levels combined with high caspase-3 activity levels were found to correlate with a higher growth inhibition in PUFA-treated cells. DHA appears to be a more potent growth inhibitor than EPA and the DHA/EPA combination. An increase in the number of apoptotic cells (early + late), ranging from 12.9 to 44.7%, was observed with increasing DHA doses.

CONCLUSION

From our data we conclude that PUFAs induce growth inhibition via targeting survivin expression in LS174T cells, which serve as a model for CCSCs.

DHA-mediated enhancement of TRAIL-induced apoptosis in colon cancer cells is associated with engagement of mitochondria and specific alterations in sphingolipid metabolism

Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid present in fish oil, may exert cytotoxic and/or cytostatic effects on colon cancer cells when applied individually or in combination with some anticancer drugs. Here we demonstrate a selective ability of subtoxic doses of DHA to enhance antiproliferative and apoptotic effects of clinically useful cytokine TRAIL (tumor necrosis factor-related apoptosis inducing ligand) in cancer but not normal human colon cells. DHA-mediated stimulation of TRAIL-induced apoptosis was associated with extensive engagement of mitochondrial pathway (Bax/Bak activation, drop of mitochondrial membrane potential, cytochrome c release), activation of endoplasmic reticulum stress response (CHOP upregulation, changes in PERK level), decrease of cellular inhibitor of apoptosis protein (XIAP, cIAP1) levels and significant changes in sphingolipid metabolism (intracellular levels of ceramides, hexosyl ceramides, sphingomyelines, sphingosines; HPLC/MS/MS). Interestingly, we found significant differences in representation of various classes of ceramides (especially C16:0, C24:1) between the cancer and normal colon cells treated with DHA and TRAIL, and suggested their potential role in the regulation of the cell response to the drug combination. These study outcomes highlight the potential of DHA for a new combination therapy with TRAIL for selective elimination of colon cancer cells via simultaneous targeting of multiple steps in apoptotic pathways.

Interaction of dietary fatty acids with tumour necrosis factor family cytokines during colon inflammation and cancer

Intestinal homeostasis is precisely regulated by a number of endogenous regulatory molecules but significantly influenced by dietary compounds. Malfunction of this system may result in chronic inflammation and cancer. Dietary essential n-3 polyunsaturated fatty acids (PUFAs) and short-chain fatty acid butyrate produced from fibre display anti-inflammatory and anticancer activities. Both compounds were shown to modulate the production and activities of TNF family cytokines. Cytokines from the TNF family (TNF- α, TRAIL, and FasL) have potent inflammatory activities and can also regulate apoptosis, which plays an important role in cancer development. The results of our own research showed enhancement of apoptosis in colon cancer cells by a combination of either docosahexaenoic acid (DHA) or butyrate with TNF family cytokines, especially by promotion of the mitochondrial apoptotic pathway and modulation of NF κ B activity. This review is focused mainly on the interaction of dietary PUFAs and butyrate with these cytokines during colon inflammation and cancer development. We summarised recent knowledge about the cellular and molecular mechanisms involved in such effects and outcomes for intestinal cell behaviour and pathologies. Finally, the possible application for the prevention and therapy of colon inflammation and cancer is also outlined.

Omega 3 fatty acids chemosensitize multidrug resistant colon cancer cells by down-regulating cholesterol synthesis and altering detergent resistant membranes composition

Background

The activity of P-glycoprotein (Pgp) and multidrug resistance related protein 1 (MRP1), two membrane transporters involved in multidrug resistance of colon cancer, is increased by high amounts of cholesterol in plasma membrane and detergent resistant membranes (DRMs). It has never been investigated whether omega 3 polyunsatured fatty acids (PUFAs), which modulate cholesterol homeostasis in dyslipidemic syndromes and have chemopreventive effects in colon cancer, may affect the response to chemotherapy in multidrug resistant (MDR) tumors.

Methods

We studied the effect of omega 3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in human chemosensitive colon cancer HT29 cells and in their MDR counterpart, HT29-dx cells.

Results

MDR cells, which overexpressed Pgp and MRP1, had a dysregulated cholesterol metabolism, due to the lower expression of ubiquitin E3 ligase Trc8: this produced lower ubiquitination rate of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCoAR), higher cholesterol synthesis, higher cholesterol content in MDR cells. We found that DHA and EPA re-activated Trc8 E3 ligase in MDR cells, restored the ubiquitination rate of HMGCoAR to levels comparable with chemosensitive cells, reduced the cholesterol synthesis and incorporation in DRMs. Omega 3 PUFAs were incorporated in whole lipids as well as in DRMs of MDR cells, and altered the lipid composition of these compartments. They reduced the amount of Pgp and MRP1 contained in DRMs, decreased the transporters activity, restored the antitumor effects of different chemotherapeutic drugs, restored a proper tumor-immune system recognition in response to chemotherapy in MDR cells.

Conclusions

Our work describes a new biochemical effect of omega 3 PUFAs, which can be useful to overcome chemoresistance in MDR colon cancer cells.

Docosahexaenoic fatty acid (DHA) in the regulation of colon cell growth and cell death: a review

BACKGROUND

Experimental, epidemiological and clinical data substantiate the beneficial role of n-3 polyunsaturated fatty acids (PUFAs) in preventing inflammation and cancer of the colon. This review covers the unsaturated docosahexaenoic fatty acid (DHA), describes some of its important cellular and molecular mechanisms, its interaction with another dietary lipid, butyrate and with endogenous apoptotic regulators of the tumour necrosis factor (TNF) family. We also discuss the clinical impact of this knowledge and the use of these lipids in colon cancer prevention and treatment.

RESULTS

From the literature, DHA has been shown to suppress the growth, induce apoptosis in colon cancer cells in vitro and decrease the incidence and growth of experimental tumours in vivo. Based on these data and our own experimental results, we describe and discuss the possible mechanisms of DHA anticancer effects at various levels of cell organization. We show that DHA can sensitize colon cancer cells to other chemotherapeutic/chemopreventive agents and affect the action of physiological apoptotic regulators of the TNF family.

CONCLUSION

Use of n-3 PUFAs could be a relatively non-toxic form of supportive therapy for improving colon cancer treatment and slowing down or preventing its recurrence. However, it is necessary to use them with caution, based on solid scientific evidence of their mechanisms of action from the molecular to the cellular and organism levels.

Multiple roles of dihomo-γ-linolenic acid against proliferation diseases

Considerable arguments remain regarding the diverse biological activities of polyunsaturated fatty acids (PUFA). One of the most interesting but controversial dietary approaches focused on the diverse function of dihomo-dietary γ-linolenic acid (DGLA) in anti-inflammation and anti-proliferation diseases, especially for cancers. This strategy is based on the ability of DGLA to interfere in cellular lipid metabolism and eicosanoid (cyclooxygenase and lipoxygenase) biosynthesis. Subsequently, DGLA can be further converted by inflammatory cells to 15-(S)-hydroxy-8,11,13-eicosatrienoic acid and prostaglandin E₁ (PGE₁). This is noteworthy because these compounds possess both anti-inflammatory and anti-proliferative properties. PGE1 could also induce growth inhibition and differentiation of cancer cells. Although the mechanism of DGLA has not yet been elucidated, it is significant to anticipate the antitumor potential benefits from DGLA.

Novel Anticancer Platinum(IV) Complexes with Adamantylamine: Their Efficiency and Innovative Chemotherapy Strategies Modifying Lipid Metabolism

The impressive impact of cisplatin on cancer on one side and severe side effects, as well as the development of drug resistance during treatment on the other side, were the factors motivating scientists to design and synthesize new more potent analogues lacking disadvantages of cisplatin. Platinum(IV) complexes represent one of the perspective groups of platinum-based drugs. In this review, we summarize recent findings on both in vitro and in vivo effects of platinum(IV) complexes with adamantylamine. Based on a literary overview of the mechanisms of activity of platinum-based cytostatics, we discuss opportunities for modulating the effects of novel platinum complexes through interactions with apoptotic signaling pathways and with cellular lipids, including modulations of the mitochondrial cell death pathway, oxidative stress, signaling of death ligands, lipid metabolism/signaling, or intercellular communication. These approaches might significantly enhance the efficacy of both novel and established platinum-based cytostatics.

Caspase-8 and p38MAPK in DATS-induced apoptosis of human CNE2 cells

Nasopharyngeal carcinoma is a common malignancy in Southern China of uncertain etiologic origin. Diallyl trisulfide (DATS), one of the major components of garlic (Allium sativum), is highly bactericidal and fungicidal. In this study, we investigated the function of p38 mitogen-activated protein kinase (MAPK) and caspase-8 in DATS-induced apoptosis of human CNE2 cells using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide], flow cytometry assay, and Western blotting. After CNE2 cells were treated with DATS (50, 100, or 150 μM) for 24 h, cell viability rates were 75.9, 63.4 and 39.6%, and apoptosis rates were 24.5, 36.9, and 62.4%, respectively. The data showed that DATS induced CNE2 cell death in a dose-dependent manner. After human CNE2 cells were treated with 100 μM DATS and inhibitors (10 μM SB203580 and Z-LETD-FMK for p38MAPK and caspase-8, respectively), changes in cell viability and apoptosis and in p38MAPK and caspase-8 activity were detected. Cell viability rates were 66.5 and 68.1% and decreased 9.9 and 11.5% compared with inhibitor treatment alone. Apoptosis rates were 31.53 and 29.98% and increased 9.1 and 10% compared with inhibitor treatment alone. The results indicated that DATS activates p38MAPK and caspase-8, but both inhibitors have an effect on P38MAPK and caspase-8 activity. In conclusion, our data indicate that p38MAPK and caspase-8 are involved in the process of DATS-induced apoptosis in human CNE2 cells and interact with each other.

The roles of p38MAPK and caspase-3 in DADS-induced apoptosis in human HepG2 cells

Objectives

To explore the function of p38MAPK and caspase-3 in DADS-induced apoptosis in human HepG2 cells, and discuss the signal transduetion mechanism of HepG2 cells in the apoptosis process induced by DADS by using the inhibitors of p38MAPK (SB203580) and caspase-3 (Z-DEVD-FMK).

Methods

After the human HepG2 cells had been treated with the DADS and inhibitors for 24 h, cell viability was determined by the MTT method, apoptosis was evaluated by flow cytometry (FCM) and the expressions of p38MAPK and caspase-3 were measured by western-blot.

Results

Our results indicated that DADS activities the p38MAPK and caspase-3, but the inhibitors, SB203580 and Z-DEVD-FMK (for p38MAPKand for caspase-3, respectively), both have the effect of inhibitory activity on P38MAPK and caspase-3. Furthermore, a combination treatment with both DADS and inhibitor (SB203580 or Z-DEVD-FMK) decreases the inhibitory and apoptotic activity of HepG2 cells increased compared with DADS-treated.

Conclusions

Our data indicate that p38MAPK and caspase-3 are involved in the process of DADS-induced apoptosis in human HepG2 cells and interact with each other.

Decreased polyunsaturated Fatty Acid content contributes to increased survival in human colon cancer

Among diet components, some fatty acids are known to affect several stages of colon carcinogenesis, whereas others are probably helpful in preventing tumors. In light of this, our aim was to determine the composition of fatty acids and the possible correlation with apoptosis in human colon carcinoma specimens at different Duke's stages and to evaluate the effect of enriching human colon cancer cell line with the possible reduced fatty acid(s). Specimens of carcinoma were compared with the corresponding non-neoplastic mucosa: a significant decrease of arachidonic acid, PPARα, Bad, and Bax and a significant increase of COX-2, Bcl-2, and pBad were found. The importance of arachidonic acid in apoptosis was demonstrated by enriching a Caco-2 cell line with this fatty acid. It induced apoptosis in a dose- and time-dependent manner via induction of PPARα that, in turn, decreased COX-2. In conclusion, the reduced content of arachidonic acid is likely related to carcinogenic process decreasing the susceptibility of cancer cells to apoptosis.

Docosahexaenoic acid suppresses arachidonic acid-induced proliferation of LS-174T human colon carcinoma cells

AIM: To investigate the impact of arachidonic acid (AA) and docosahexaenoic acid (DHA) and their combination on colon cancer cell growth.

METHODS: The LS-174T colon cancer cell line was used to study the role of the prostaglandin precursor AA and the omega-3 polyunsaturated fatty acid DHA on cell growth. Cell viability was assessed in XTT assays. For analysis of cell cycle and cell death, flow cytometry and DAPI staining were applied. Expression of cyclooxygenase-2 (COX-2), p21 and bcl-2 in cells incubated with AA or DHA was examined by real-time RT-PCR. Prostaglandin E₂ (PGE₂) generation in the presence of AA and DHA was measured using a PGE₂-ELISA.

RESULTS: AA increased cell growth, whereas DHA reduced viability of LS 174T cells in a time- and dose-dependent manner. Furthermore, DHA down- regulated mRNA of bcl-2 and up-regulated p21. Interestingly, DHA was able to suppress AA-induced cell proliferation and significantly lowered AA-derived PGE₂ formation. DHA also down-regulated COX-2 expression. In addition to the effect on PGE₂ formation, DHA directly reduced PGE₂-induced cell proliferation in a dose-dependent manner.

CONCLUSION: These results suggest that DHA can inhibit the pro-proliferative effect of abundant AA or PGE₂.

Site specific delivery of microencapsulated fish oil to the gastrointestinal tract of the rat

The aim of this study was to design food grade matrices to deliver microencapsulated fish oil to the large bowel of the rat where the potential exists to retard inflammation and cancer development. Digestion in simulated gastric fluid and intestinal fluid demonstrated that only 4-6% of oil was released from the following dried emulsion formulations: 50% fish oil encapsulated in heated casein-glucose-dried glucose syrup (1:1:1) (Cas-Glu-DGS-50); 25% fish oil in casein-modified resistant starch (Hylon VII) (1:1) (Cas-Hylon-25); or 25% fish oil in Cas-Glu-Hylon (1:1:1) (Cas-Glu-Hylon-25). A short-term gavage study (0-12 h) with fish oil and Cas-Glu-DGS-50 demonstrated the appearance of fish oil long chain (LC) n-3 polyunsaturated fatty acids (PUFA) into the plasma indicating specific small intestinal absorption with little LC n-3 PUFA reaching the large bowel. In a 2-week-long term, daily gavage study, the bioavailability of fish oil and fish oil in Cas-Glu-DGS-50 or Cas-Hylon-25 demonstrated that fish oil and Cas-Glu-DGS-50 LC n-3 PUFA were incorporated into the tissue of the small intestine and colon, whereas Cas-Hylon-25 was resistant to degradation in the small intestine. The use of modified Hylon VII for targeted colonic delivery was confirmed in the final short-term gavage study (0-14 h) using Cas-Glu-Hylon-25 with [(14)C]-trilinolenin as a marker incorporated into the microcapsules, where up to 60% of the labeled oil reached the large bowel. Depending on the microencapsulating matrix employed, fish oil can be delivered selectively to the small intestine or to a high degree to the large bowel.

Inhibition of colorectal cancer by targeting hepatocyte nuclear factor-4alpha

Hepatocyte nuclear factor-4alpha (HNF-4alpha) serves as target for fatty acid nutrients and xenobiotic amphipathic carboxylates and may account for the differential effects of dietary fatty acids on colorectal cancer (CRC). The putative role played by HNF-4alpha in CRC has been verified here by evaluating the effect of HNF-4alpha antagonists and HNF-4alpha siRNA on CRC growth and proliferation in cultured CRC cells and xenotransplanted nude mice in vivo. HNF-4alpha ligand antagonists of the MEDICA series, namely, beta,beta'-tetramethylhexadecanedioic acid (M16betabeta) and gamma,gamma'-tetramethyloctadocanedioic acid (M18gammagamma) as well as HNF-4alpha siRNA are shown here to inhibit growth and proliferation of HT29 and Caco2 CRC cells, accompanied by increased subG1 cell population, downregulated PCNA, activation of caspase-3, upregulation of Bak and cytoplasmic cytochrome-c, and downregulation of Bcl-2 resulting in apoptotic death. Inhibition of CRC growth with concomitant apoptosis was further confirmed in nude mice xenotransplanted with HT29 CRC cells. CRC suppression by HNF-4alpha ligand antagonists and by HNF-4alpha siRNA was accounted for by suppression of HNF-4alpha transcription and protein expression. alpha,alpha'-tetrachlorotetradecanedioic acid (Cl-DICA), a MEDICA analogue that fails to suppress HNF-4alpha, was ineffective in suppressing growth of cultured or xenotransplanted HT29 CRC cells. Hence, increased transcriptional activity of HNF-4alpha converging onto genes coding for antiapoptotic oncogenes and cytokines may promote CRC development. Suppression of HNF-4alpha activity by natural or xenobiotic HNF-4alpha ligand antagonists or by HNF-4alpha siRNA may offer a treatment mode for CRC.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

Many studies have shown that addition of fish oil (FO) to the diet reduces tumor growth but the mechanism(s) of action involved is (are) still unknown. In this study, we examine some possible mechanisms in tumor-bearing rats chronically supplemented with FO. Male Wistar rats (21 days old) were fed with regular chow and supplemented with coconut or FO (1g/kg body weight) until they reached 70 days of age. Then, they were inoculated with a suspension of Walker 256 ascitic tumor cells (2 x 10(7)ml) and after 14 days they were killed. Supplementation with FO resulted in significantly lower tumor weight, greater tumor cell apoptosis, lower ex vivo tumor cell proliferation, a higher tumor content of lipid peroxides, lower expression of cyclooxygenase-2 (COX-2) in tumor tissue and a lower plasma concentration of prostaglandin E2 than observed in rats fed regular chow or supplemented with coconut oil. These results suggest that reduction of tumor growth by FO involves an increase in apoptosis and of lipid peroxidation in tumor tissue, with a reduction in tumor cell proliferation ex vivo, COX-2 expression and PGE2 production. Thus, FO may act simultaneously through multiple effects to reduce tumor growth. Whether these effects are connected through a single underlying mechanism remains to be seen.

Death receptor-3, a new E-Selectin counter-receptor that confers migration and survival advantages to colon carcinoma cells by triggering p38 and ERK MAPK activation

E-selectin-mediated adhesion of colon cancer cells to endothelial cells is a key event in metastasis. However, the signaling mechanisms that confer metastatic advantages to cancer cells adhering to E-selectin are ill defined. By using affinity column chromatography and pull-down assays on purified membrane extracts of HT29 and LoVo cells coupled to mass spectrometry analysis, we obtained the first evidence indicating that E-selectin binds to death receptor-3 (DR3) expressed by the cancer cells. Thereafter, we accumulated several results, suggesting that DR3 is an E-selectin receptor on colon cancer cells and that its activation by E-selectin triggers the activation of p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) and confers migration and survival advantages. First, by Western blotting, we found that the E-selectin-binding protein, identified as DR3, is recognized by two anti-DR3 antibodies. Second, the neutralization of DR3 with an antibody and its knockdown by small interfering RNA decrease the adhesion of colon cancer cells to E-selectin and E-selectin-expressing human umbilical vein endothelial cells. Third, inhibiting DR3 and knocking down its expression impair transendothelial migration of HT29 cells and block the activation of p38 and ERK by E-selectin. Fourth, high molecular weight isoforms of DR3 are expressed in samples of primary human colon carcinoma but not in samples from normal colon tissue. Intriguingly, DR3 is a death receptor but its activation by E-selectin does not induce apoptosis in colon cancer cells, except when ERK is inhibited. Our findings identify novel signaling and functional roles of DR3 activated in response to E-selectin and highlight the potential link between DR3 and metastasis.

Induction of apoptosis in K562/ADM cells by gamma-linolenic acid involves lipid peroxidation and activation of caspase-3

Numerous studies have revealed that gamma-linolenic acid (GLA) possesses effective tumoricidal properties while not inducing damage to normal cells or creating harmful systemic side effects. It can exert anti-tumor efficacy against a variety of cancers including leukemia. However, little is known about the effects of GLA on leukemia resistant to chemotherapy, emerging as a serious clinical problem. The present study tested GLA-induced apoptosis in K562/ADM multidrug-resistant (MDR) leukemic cells and investigated its possible mechanisms. Using cell viability, fluorescent staining of nuclei, flow cytometric Annexin V/PI double staining and lactate dehydrogenase (LDH) release, we found that GLA could inhibit cell growth and induce apoptosis and secondary necrosis. The results showed that incubation with GLA concentrations of 10-60 microg/ml caused a dose- and time-dependent decrease of K562/ADM cell viability, and the IC50 value was 50.5 microg/ml at 24 h and 31.5 microg/ml at 48 h. Flow cytometry using Annexin V/PI double staining assessed apoptosis, necrosis and viability. Typical apoptotic nuclei were shown by staining of K562/ADM cells with DNA-binding fluorochrome Hoechst 33342, characterized by chromatin condensation and nuclear fragmentation. On the other hand, after treated K562/ADM cells with 20 microg/ml GLA for 48 h and with 40 microg/ml GLA for 12 h, the LDH release significantly increased, indicated losses of plasma membrane integrity and presence of necrosis. Further, the inhibition of GLA-induced apoptosis by a pan-caspase inhibitor (z-VAD-fmk) suggested the involvement of caspases. The increase of caspase-3 activity with GLA concentration confirmed its role in the process. The results also showed that the malondialdehyde (MDA) content was also significantly elevated, and antioxidant BHT could block GLA cytotoxity, indicating the cytotoxity induced by GLA may be due to lipid peroxidation.

An introduction to dietary/supplemental omega-3 fatty acids for general health and prevention: Part II

The correction of a subtle nutritional deficiency that may reduce the risk of a future chronic disease is indeed a challenge. However, some specific examples in the past, such as the addition of folic acid to prevent neural tube defects and calcium and vitamin D to prevent osteoporosis, should provide some encouragement that some conditions can be prevented with the appropriate addition of a deficient compound. One of the most intriguing current and future impacts on public health may come from a higher intake of omega-3 fatty acids, such as alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). The omega-3 fatty acids continue to accumulate research that suggests that they may prevent a variety of diverse chronic diseases and potentially some acute clinical scenarios. In the first part of this article, the potential for these compounds to prevent certain cardiovascular conditions are discussed. In the second part, the potential for an impact in arthritis, numerous areas of cancer research, depression, maternal and child health, neurologic diseases, osteoporosis, and other medical disciplines are also briefly covered. The future appears bright for these agents, but specifically which conditions, who qualifies, testing, frequency, adequate sources, future trials, and numerous other questions need to be addressed and answered before the potential impact can catch up to the recent hype.