Mechanisms of action of eicosapentaenoic acid in bladder cancer cells in vitro: alterations in mitochondrial metabolism, reactive oxygen species generation and apoptosis induction

The value of plasma omega-3 polyunsaturated fatty acids in predicting the response and prognosis of cervical squamous cell carcinoma patients to concurrent chemoradiotherapy

Background: In recent years, abnormalities in plasma omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have been proven to be related to the risk of cancer, but their prognostic value for cancer is unclear. The purpose of this study was to retrospectively evaluate the response and prognostic significance of plasma omega-3 PUFAs in patients with cervical squamous cell carcinoma (CSCC) treated with concurrent chemoradiotherapy (CCRT). Spearman rank correlation analysis was used to analyze the correlation between omega-3 PUFAs and squamous cell carcinoma antigen (SCC-Ag) levels. Methods: A total of 89 patients with CSCC who underwent CCRT were evaluated retrospectively. Binary logistic regression analysis was used to analyze the independent predictors related to complete response (CR) after CCRT. A Cox proportional hazard model and Kaplan-Meier analysis were utilized to perform survival analysis. Results: According to multivariate logistic regression analyses, a high level of plasma EPA was independently correlated with an increased incidence of CR after CCRT (odds ratio (OR), 0.980; 95% confidence interval (CI), 0.962-0.999, p = 0.038). With a median follow-up of 41.3 months, the CSCC patients in the high EPA (≥46.0 nmol/mL) group exhibited longer OS and PFS. According to our multivariate analysis, pretreatment plasma EPA level was an independent prognostic factor for PFS in patients with CSCC who underwent CCRT (hazard ratio (HR), 0.263; 95% CI, 0.089-0.782, p = 0.016). However, it was not an independent prognostic factor of OS. Spearman rank correlation analysis revealed was a negative correlation between pretreatment SCC-Ag (pre SCC-Ag) levels and EPA levels (r = -0.305, p = 0.004), and a weak negative correlation between posttreatment SCC-Ag (post SCC-Ag) levels and EPA levels (r = -0.251, p = 0.018). Conclusion: Plasma omega-3 PUFAs are related to the response and survival outcome of patients with CSCC who underwent CCRT. Pretreatment plasma EPA levels may be a promising biomarker for predicting the response and prognosis of patients with CSCC who undergo CCRT. In addition, the pretreatment plasma EPA levels presented a negative correlation with the SCC-Ag levels.

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.

Effect of Polyunsaturated Fatty Acids on Temozolomide Drug-Sensitive and Drug-Resistant Glioblastoma Cells

Glioblastomas (GBMs) are notoriously difficult to treat, and the development of multiple drug resistance (MDR) is common during the course of the disease. The polyunsaturated fatty acids (PUFAs) gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) have been reported to improve MDR in several tumors including breast, bladder, and leukaemia. However, the effects of PUFAs on GBM cell MDR are poorly understood. The present study investigated the effects of PUFAs on cellular responses to temozolomide (TMZ) in U87MG cells and the TMZ-resistant (TMZR) cells derived from U87MG. Cells were treated with PUFAs in the absence or presence of TMZ and dose–response, viable cell counting, gene expression, Western blotting, flow cytometry, gas chromatography-mass spectrometry (GCMS), and drug efflux studies were performed. The development of TMZ resistance caused an increase in ABC transporter ABCB1 and ABCC1 expression. GLA-, EPA-, and DHA-treated cells had altered fatty acid composition and accumulated lipid droplets in the cytoplasm. The most significant reduction in cell growth was seen for the U87MG and TMZR cells in the presence of EPA. GLA and EPA caused more significant effects on ABC transporter expression than DHA. GLA and EPA in combination with TMZ caused significant reductions in rhodamine 123 efflux from U87MG cells but not from TMZR cells. Overall, these findings support the notion that PUFAs can modulate ABC transporters in GBM cells.

Inclusion of the in-chain sulfur in 3-thiaCTU increases the efficiency of mitochondrial targeting and cell killing by anticancer aryl-urea fatty acids

Mitochondria in tumor cells are functionally different from those in normal cells and could be targeted to develop new anticancer agents. We showed recently that the aryl-ureido fatty acid CTU is the prototype of a new class of mitochondrion-targeted agents that kill cancer cells by increasing the production of reactive oxygen species (ROS), activating endoplasmic reticulum (ER)-stress and promoting apoptosis. However, prolonged treatment with high doses of CTU were required for in vivo anti-tumor activity. Thus, new strategies are now required to produce agents that have enhanced anticancer activity over CTU. In the present study we prepared a novel aryl-urea termed 3-thiaCTU, that contained an in-chain sulfur heteroatom, for evaluation in tumor cell lines and in mice carrying tumor xenografts. The principal finding to emerge was that 3-thiaCTU was several-fold more active than CTU in the activation of aryl-urea mechanisms that promoted cancer cell killing. Thus, in in vitro studies 3-thiaCTU disrupted the mitochondrial membrane potential, increased ROS production, activated ER-stress and promoted tumor cell apoptosis more effectively than CTU. 3-ThiaCTU was also significantly more active than CTUin vivo in mice that carried MDA-MB-231 cell xenografts. Compared to CTU, 3-thiaCTU prevented tumor growth more effectively and at much lower doses. These findings indicate that, in comparison to CTU, 3-thiaCTU is an aryl-urea with markedly enhanced activity that could now be suitable for development as a novel anticancer agent.

Bioactive Lipids in Age-Related Disorders

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

MicroRNA-98 promotes drug resistance and regulates mitochondrial dynamics by targeting LASS2 in bladder cancer cells

MicroRNA-98(miR-98) has been shown to be critical for tumorigenesis, however its involvement in bladder cancer are unclear. The present study aims to investigate the expression, biological roles and potential mechanisms of miR-98 in human bladder cancer. We found that miR-98 was upregulated in bladder urothelial carcinoma tissues compared with adjacent normal tissues. In addition, miR-98 expression was higher in bladder cancer cell lines than in uroepithelial cell line SV-HUC-1. Functional studies revealed that miR-98 mimic promoted proliferation of T24 cells while miR-98 inhibitor inhibited proliferation of BIU-87 cells. Moreover, miR-98 mimic increased cisplatin/doxorubicin resistance and inhibited apoptosis in T24 cells, while miR-98 inhibitor decreased chemoresistance and facilitated apoptosis in BIU-87 cells. Further experiments using MitoTracker and JC-1 staining showed that miR-98 could regulate mitochondrial fission/fusion balance and mitochondrial membrane potential. Western blot showed that miR-98 upregulated cyclin D1, p-Drp1 and Drp1. Using luciferase reporter assay, we demonstrated that LASS2 acted as a direct target of miR-98. LASS2 overexpression induced mitochondrial fusion and downregulated mitochondrial potential, with decreased p-Drp1 status. Additionally, LASS2 siRNA abrogated the effects of miR-98 mimic on Drp1phosphorylation and chemoresistance. We also found a negative correlation between LASS2 and miR-98 in bladder cancer tissues. In conclusion, our study demonstrates that miR-98 targets LASS2 and regulates bladder cancer chemoresistance through modulation of mitochondrial function.

Decreased Oleic Acid and Marine n - 3 Polyunsaturated Fatty Acids in Tunisian Patients with Urothelial Bladder Cancer

Fatty acids (FAs) are thought to impact carcinogenesis by affecting cell signaling. A case-control study including 250 patients with urothelial bladder cancer (UBC) and 250 controls was conducted. Plasma FAs composition was assessed using capillary gas chromatography. Associations of individual and classes of FAs with UBC were controlled for the main risk factors for UBC. Plasma FAs profile was different in patients compared to controls. Higher levels (third tertile vs. first tertile) in palmitic acid (PA) [multi-adjusted OR (95% CI), 1.83 (1.14-2.92)], and n - 6:n - 3 FA ratio [4.13 (2.38-7.16)] were associated with increased risk for UBC [multi-adjusted OR (95% CI), 1.83 (1.14-2.92)]. In contrast, higher levels (third tertile vs. first tertile) in oleic [0.54 (0.34-0.86)], dihomo-γ-linolenic (DGLA) [0.47 (0.29-0.74)], eicosapentaenoic (EPA) [0.32 (0.19-0.52)], and docosahexaenoic (DHA) acids [0.33 (0.20-0.53)] were associated with lower risk for UBC. Although the study design does not allow proving causality, the findings suggest a possible protective role of oleic acid and marine n - 3 polyunsaturated FAs (PUFAs) against bladder carcinogenesis.

Omega-3 fatty acids, membrane remodeling and cancer prevention

Proteins are often credited as the macromolecule responsible for performing critical cellular functions, however lipids have recently garnered more attention as our understanding of their role in cell function and human health becomes more apparent. Although cellular membranes are the lipid environment in which many proteins function, it is now apparent that protein and lipid assemblies can be organized to form distinct micro- or nanodomains that facilitate signaling events. Indeed, it is now appreciated that cellular function is partly regulated by the specific spatiotemporal lipid composition of the membrane, down to the nanosecond and nanometer scale. Furthermore, membrane composition is altered during human disease processes such as cancer and obesity. For example, an increased rate of lipid/cholesterol synthesis in cancerous tissues has long been recognized as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids/cholesterol to cellular function in disease models is not yet fully understood. Furthermore, an important consideration in regard to human health is that diet is a major modulator of cell membrane composition. This can occur directly through incorporation of membrane substrates, such as fatty acids, e.g., n-3 polyunsaturated fatty acids (n-3 PUFA) and cholesterol. In this review, we describe scenarios in which changes in membrane composition impact human health. Particular focus is placed on the importance of intrinsic lipid/cholesterol biosynthesis and metabolism and extrinsic dietary modification in cancer and its effect on plasma membrane properties.

Lipid analogues as potential drugs for the regulation of mitochondrial cell death

The mitochondrion plays an important role in the production of energy as ATP, the regulation of cell viability and apoptosis, and the biosynthesis of major structural and regulatory molecules, such as lipids. During ATP production, reactive oxygen species are generated that alter the intracellular redox state and activate apoptosis. Mitochondrial dysfunction is a well-recognized component of the pathogenesis of diseases such as cancer. Understanding mitochondrial function, and how this is dysregulated in disease, offers the opportunity for the development of drug molecules to specifically target such defects. Altered energy metabolism in cancer, in which ATP production occurs largely by glycolysis, rather than by oxidative phosphorylation, is attributable in part to the up-regulation of cell survival signalling cascades. These pathways also regulate the balance between pro- and anti-apoptotic factors that may determine the rate of cell death and proliferation. A number of anti-cancer drugs have been developed that target these factors and one of the most promising groups of agents in this regard are the lipid-based molecules that act directly or indirectly at the mitochondrion. These molecules have emerged in part from an understanding of the mitochondrial actions of naturally occurring fatty acids. Some of these agents have already entered clinical trials because they specifically target known mitochondrial defects in the cancer cell.

Resveratrol induces apoptosis associated with mitochondrial dysfunction in bladder carcinoma cells

OBJECTIVE

Resveratrol shows chemopreventive activity in a variety of human cancers by targeting mitochondria and triggering apoptosis. The purpose of this study was to investigate the antitumor action of resveratrol in bladder cancer and its underlying mechanism.

METHODS

Using two different bladder cell lines, BTT739 and T24, the cytotoxicity of resveratrol were determined by MTT assay. The apoptosis induced by resveratrol was assayed by transferase dUTP nick end labeling staining. To show whether the mitochondrial dysfunction involved in the effects of resveratrol, mitochondrial function was detected by mitochondrial membrane potential, reactive oxygen species production and adenosine 5'-triphosphate content. In addition, the markers of apoptosis in the intrinsic mitochondrial-dependent pathway were analyzed by the release of cytochrome c and the activities of caspase-9 and caspase-3.

RESULTS

Resveratrol effectively decreased cell viability and induced apoptosis in a concentration- and time-dependent manner. In addition, resveratrol significantly disrupted the mitochondrial membrane potential in both intact cells and isolated mitochondria. Resveratrol also increased reactive oxygen species production and reduced adenosine 5'-triphosphate concentrations. Western blot analysis showed that resveratrol provoked the release of cytochrome c from mitochondria to the cytosol. Furthermore, resveratrol significantly promoted the activation of caspase-9 and caspase-3.

CONCLUSIONS

These findings suggest that resveratrol efficiently triggers apoptosis in bladder cancer cells through the intrinsic mitochondrial-dependent pathway, which is associated with mitochondrial dysfunction. Resveratrol might have great pharmacological promise in the treatment of bladder cancer.

Effect of n-3 polyunsaturated fatty acid on gene expression of the critical enzymes involved in homocysteine metabolism

BACKGROUND

Previous studies showed that plasma n-3 polyunsaturated fatty acid (PUFA) was negatively associated with plasma homocysteine (Hcy).

OBJECTIVE

We investigated the regulatory effect of n-3 PUFA on mRNA expression of the critical genes encoding the enzymes involved in Hcy metabolism.

METHODS

HepG2 cells were treated with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA) respectively for 48 h. The cells were collected and total RNA was isolated. The mRNA expression levels of the genes were determined by using Real Time-PCR.

RESULTS

Compared with controls, the mRNA expression levels of 5-methyltetrahydrofolate reductase (MTHFR) were significantly increased in the DHA group (p < 0.05) and ALA group (p < 0.05); Significantly down-regulated mRNA expression of methionine adenosyltransferase (MAT) was observed with the treatments compared with the controls; the level of MAT expression was significant lower in the DHA group than the ALA group (p < 0.05); Cystathionine-γ-lyase (CSE) expression was significantly increased in the DHA (p < 0.05) and EPA groups (p < 0.05) compared with control. No significant changes were shown in mRNA expression levels of S-adenosylhomocysteine hydrolases (SAHH), cystathionine β-synthase (CBS), and 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR).

CONCLUSIONS

Our results suggest that DHA up-regulates CSE and MTHFR mRNA expression and down-regulates MAT mRNA expression involved in Hcy metabolism.

Physical and chemical modulation of lipid rafts by a dietary n-3 polyunsaturated fatty acid increases ethanol-induced oxidative stress

Dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) have been reported to modulate lipid raft-dependent signaling, but not yet lipid raft-dependent oxidative stress. Previously, we have shown that ethanol-induced membrane remodeling, i.e., an increase in membrane fluidity and alterations in physical and biochemical properties of lipid rafts, participated in the development of oxidative stress. Thus, we decided to study n-3 PUFA effects in this context, by pretreating hepatocytes with eicosapentaenoic acid (EPA), a long-chain n-3 PUFA, before addition of ethanol. EPA was found to increase ethanol-induced oxidative stress through membrane remodeling. Addition of EPA resulted in a marked increase in lipid raft aggregation compared to ethanol alone. In addition, membrane fluidity of lipid rafts was markedly enhanced. Interestingly, EPA was found to preferentially incorporate into nonraft membrane regions, leading to raft cholesterol increase. Lipid raft aggregation by EPA enhanced phospholipase Cγ translocation into these microdomains. Finally, phospholipase Cγ was shown to participate in the potentiation of oxidative stress by promoting lysosome accumulation, a major source of low-molecular-weight iron. To conclude, the ability of EPA to modify lipid raft physical and chemical properties plays a key role in the enhancement, by this dietary n-3 PUFA, of ethanol-induced oxidative stress.

Lipids, mitochondria and cell death: implications in neuro-oncology

Polyunsaturated fatty acids (PUFAs) are known to inhibit cell proliferation of many tumour types both in vitro and in vivo. Their capacity to interfere with cell proliferation has been linked to their induction of reactive oxygen species (ROS) production in tumour tissues leading to cell death through apoptosis. However, the exact mechanisms of action of PUFAs are far from clear, particularly in brain tumours. The loss of bound hexokinase from the mitochondrial voltage-dependent anion channel has been directly related to loss of protection from apoptosis, and PUFAs can induce this loss of bound hexokinase in tumour cells. Tumour cells overexpressing Akt activity, including gliomas, are sensitised to ROS damage by the Akt protein and may be good targets for chemotherapeutic agents, which produce ROS, such as PUFAs. Cardiolipin peroxidation may be an initial event in the release of cytochrome c from the mitochondria, and enriching cardiolipin with PUFA acyl chains may lead to increased peroxidation and therefore an increase in apoptosis. A better understanding of the metabolism of fatty acids and eicosanoids in primary brain tumours such as gliomas and their influence on energy balance will be fundamental to the possible targeting of mitochondria in tumour treatment.