Lipid hydroperoxides from processed dietary oils enhance growth of hepatocarcinoma cells

Multiomics characterization of fatty acid metabolism for the clinical management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignancy and there is a lack of effective biomarkers for HCC diagnosis. Living organisms are complex, and different omics molecules interact with each other to implement various biological functions. Genomics and metabolomics, which are the top and bottom of systems biology, play an important role in HCC clinical management. Fatty acid metabolism is associated with malignancy, prognosis, and immune phenotype in cancer, which is a potential hallmark in malignant tumors. In this study, the genes and metabolites related to fatty acid metabolism were thoroughly investigated by a dynamic network construction algorithm named EWS-DDA for the early diagnosis and prognosis of HCC. Three gene ratios and eight metabolite ratios were identified by EWS-DDA as potential biomarkers for HCC clinical management. Further analysis using biological analysis, statistical analysis and document validation in the discovery and validation sets suggested that the selected potential biomarkers had great clinical prognostic value and helped to achieve effective early diagnosis of HCC. Experimental results suggested that in-depth evaluation of fatty acid metabolism from different omics viewpoints can facilitate the further understanding of pathological alterations associated with HCC characteristics, improving the performance of early diagnosis and clinical prognosis.

Plasma lipids, tumor parameters and survival in HCC patients with HBV and HCV

INTRODUCTION AND AIMS

Hepatocellular carcinoma (HCC) is a consequence of chronic liver disease, particularly from hepatitis B or C and increasingly from obesity and metabolic syndrome. Since lipids are an important component of cell membranes and are involved in cell signaling and tumor cell growth, we wished to evaluate the relationship between HCC patient plasma lipids and maximum tumor diameter and other indices of HCC human biology.

METHODS

We examined prospectively-collected data from a multi-institutional collaborative Turkish HCC working group, from predominantly HBV-based patients, for plasma lipid profiles, consisting of triglycerides, total cholesterol, LDL-cholesterol (LDL) and HDL-cholesterol (HDL) and compared these with the associated patient maximum tumor diameter (MTD), portal vein thrombosis, alpha-fetoprotein (AFP) and also with patient survival.

RESULTS

We found that both low HDL (p=0.0002) and high LDL (p=0.003) levels were significantly associated with increased MTD, as well as in a final multiple linear regression model on MTD. The combination of low HDL combined with high HDL levels were significant in a regression model on MTD, PVT and an HCC Aggressiveness Index (Odds Ratio 12.91 compared to an Odds Ratio of 1 for the reference). Furthermore, in a Cox regression model on death, the HDL plus LDL combination had a significantly higher Hazard Ratio than the reference category.

CONCLUSIONS

Low plasma HDL, high plasma LDL and especially the combination, were significantly related to more aggressive HCC phenotype and the combination was significantly related to a higher Hazard Ratio for death.

Cytotoxic Activity of Piperazin-2-One-Based Structures: Cyclic Imines, Lactams, Aminophosphonates, and Their Derivatives

N-Heterocycles are considered as desirable scaffolds for the development of novel lead compounds for anticancer drug research. Among them, phosphorus-containing amino-derivatives play a crucial role. A series of imines and products of their further reactions with P-nucleophiles were obtained starting from vicinal bisamines. Reaction of ethylenediamine and α-carbonyl esters yielded in novel unexpected products, which structures were confirmed by crystallographic measurements. The cytotoxic activity evaluation was done on a variety of cell lines including HUH7, AKH12, DAOY, UW228-2, D283, D425, and U251. Human umbilical vein endothelial cells (HUVECs) were used as control. Two of the tested compounds, bearing TADDOL-derived, and trifluoromethyl substituents showed a significant effect on cell viability, though comparable to nonmalignant cells.

Brief High Oxygen Concentration Induces Oxidative Stress in Leukocytes and Platelets: A Randomized Cross-over Pilot Study in Healthy Male Volunteers

BACKGROUND

Supplemental oxygen is administered routinely in the clinical setting to relieve or prevent tissue hypoxia, but excessive exposure may induce oxidative damage or disrupt essential homeostatic functions. It is speculated that oxidative stress in leukocytes and platelets may contribute to vascular diseases by promoting inflammation and cell aggregation.

METHODS

In this pilot study 30 healthy male volunteers (18-65 years) were exposed to high oxygen concentration (non-rebreather mask, 8 L/min, 100% O2) and synthetic air (non-rebreather mask, 8 L/min, 21% O2) in a cross-over design for 20 min at a 3-week interval. Venous blood samples were obtained at baseline and 1, 3, and 6 h postintervention. Primary outcome was generation of reactive oxygen species in leukocytes as measured by the redox-sensitive fluorescent dye dihydrorhodamine 123. Additional outcomes were oxidative stress in platelets and platelet aggregation as measured by thromboelastography (ROTEM) and Multiplate analyses.

FINDINGS

High oxygen exposure induced oxidative stress in leukocytes as evidenced by significantly higher mean fluorescence intensity (MFI) compared with synthetic air at 3 h postintervention (47% higher, P = 0.015) and 6 h postintervention (37% higher, P = 0.133). Oxidative stress was also detectable in platelets (33% higher MFI in comparison with synthetic air at 6 h, P = 0.024; MFI 20% above baseline at 3 h, P  = 0.036; 37% above baseline at 6 h, P = 0.002). ROTEM analyses demonstrated reduced mean clotting time 1 h postintervention compared with baseline (-4%, P = 0.049), whereas there were no significant effects on other surrogate coagulation parameters.

CONCLUSION

Clinically relevant oxygen exposure induces oxidative stress in leukocytes and platelets, which may influence the immune and clotting functions of these cells.

Synthesis and Cytotoxic Activity of Chiral Sulfonamides Based on the 2-Azabicycloalkane Skeleton

A series of chiral sulfonamides containing the 2-azabicycloalkane scaffold were prepared from aza-Diels-Alder cycloadducts through their conversion to amines based on 2-azanorbornane or the bridged azepane skeleton, followed by the reaction with sulfonyl chlorides. The cytotoxic activity of the obtained bicyclic derivatives was evaluated using human hepatocellular carcinoma (HCC), medulloblastoma (MB), and glioblastoma (GBM) cell lines. Chosen compounds were shown to notably reduce cell viability as compared to nonmalignant cells.

Improvement of Serum Biochemical Parameters and Hematological Indices Through α-Tocopherol Administration in Dietary Oxidized Olive Oil Induced Toxicity in Rats

Dietary oxidized olive oil, alone or in combination with different doses of α-tocopherol, were given to Swiss albino rats for 30 days; in order to determine its role in oxidative stress and fatty liver, induced by the oxidized olive oils. Serum biochemical parameters and hematological indices of blood were analyzed. The liver was analyzed for histopathological changes, lipid peroxidation, and polar triacylglycerols composition. Results revealed that there was a significant decline in the serum total cholesterol, triglycerides, LDL, glucose and ALT; while a significant increase occurred in the serum HDL levels through the supplementation of α-tocopherol in male and female rats. Hematological parameters were almost in the normal reference range in the groups that were fed α-tocopherol, alone or in combination with oxidized oil, while being significantly altered by the oxidized olive oil. There were acute hepatitis and necrosis in the liver with no fatty changes after feeding with oxidized olive oil, along with varying doses of α-tocopherol. Higher amounts of polar compounds were present in female rats (15.2–93.1 μg/g) compared to male rats (12.2–82.3%) that correspond to the supplementation of α-tocopherol in combination with oxidized oil. Lipid oxidation in liver was minimized by tocopherol, while an increase occurred in the accumulation of oxidized lipids in the liver. These findings revealed that tocopherol is beneficial against the oxidized oil induced biochemical and hematological changes and lipid peroxidation but causes fatty accumulation in the liver. Therefore, the role of tocopherol in patients with fatty liver disease may be considered, as tocopherol may increase the chance of survival.

Plasma cholesterol and lipoprotein levels in relation to tumor aggressiveness and survival in HCC patients

BACKGROUND AND AIMS:

Hepatocellular carcinoma is associated with several chronic liver diseases, especially chronic hepatitis B virus, hepatitis C virus, and alcoholism. It is increasingly appreciated that obesity/metabolic syndrome is also associated with chronic liver disease and subsequent hepatocellular carcinoma.

METHODS:

We retrospectively investigated the serum lipid profiles in a large hepatocellular carcinoma cohort, associated predominantly with the hepatitis B virus, hepatitis C virus, alcohol or nonalcoholic steatohepatitis. The cohort was examined both as a whole, as well as stratified by etiology.

RESULTS:

We found significant associations between parameters of hepatocellular carcinoma biology such as maximum tumor diameter, portal vein thrombosis, tumor multifocality or alpha-fetoprotein levels and individual lipid components, including total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides and body mass index. In a final multiple linear regression model considering all lipid variables together, only high-density lipoprotein cholesterol was significantly associated with the tumor Tumor Aggressiveness Index. High-density lipoprotein cholesterol was found to have a statistically higher hazard ratio for death than low high-density lipoprotein cholesterol levels (Cox). On examination by etiological group, alpha-fetoprotein levels were significantly higher in patients with hepatitis C virus compared to those with alcohol or nonalcoholic steatohepatitis, but maximum tumor diameter, tumor multifocality and portal vein thrombosis were similar across etiological groups. Nonalcoholic steatohepatitis patients had significantly less cirrhosis than other groups and hepatitis B virus patients had significantly higher cholesterol and low-density lipoprotein cholesterol levels than hepatitis C virus patients.

CONCLUSIONS:

This is the first report, to our knowledge, of a relationship between serum lipid parameters and indices of hepatocellular carcinoma growth, invasion and aggressiveness, as well as with survival.

Impact of glutathione peroxidase 4 on cell proliferation, angiogenesis and cytokine production in hepatocellular carcinoma

Insufficient supplementation with the micronutrient selenium and persistent hepatic inflammation predispose to hepatocellular carcinoma (HCC). Inflammation-associated reactive oxygen species attack membrane lipids and form lipid hydroperoxides able to propagate oxidative hepatic damage. Selenium-containing enzyme glutathione peroxidase 4 (GPx4) antagonizes this damage by reducing lipid hydroperoxides to respective hydroxides. However, the role of GPx4 in HCC remains elusive. We generated two human HCC cell lines with stable overexpression of GPx4, performed xenotransplantation into NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ (NSG) host mice and characterized the tumors formed. The experimental data were verified using gene expression data from two independent HCC patient cohorts. GPx4 overexpression protected from oxidative stress and reduced intracellular free radical level. GPx4-overexpressing cells displayed impaired tumor growth, reduced proliferation, altered angiogenesis and decreased expression of clinically relevant cytokine interleukin-8 and C-reactive protein. Moreover, GPx4 overexpression impaired migration of endothelial cells in vitro, and enhanced expression of thrombospondin 1, an endogenous inhibitor of angiogenesis. In patients, GPx4 expression in tumors positively correlated with survival and was linked to pathways which regulate cell proliferation, motility, tissue remodelling, immune response and M1 macrophage polarization. The patient data largely confirmed experimental findings especially in a subclass of poor prognosis tumors with high proliferation. GPx4 suppresses formation and progression of HCC by inhibition of angiogenesis and tumor cell proliferation as well as by immune-mediated mechanisms. Modification of GPx4 expression may represent a novel tool for HCC prevention or treatment.

Determination of triacylglycerol oxidation mechanisms in canola oil using liquid chromatography-tandem mass spectrometry

Triacylglycerol (TG), the main component of edible oil, is oxidized by thermal- or photo- oxidation to form TG hydroperoxide (TGOOH) as the primary oxidation product. Since TGOOH and its subsequent oxidation products cause not only the deterioration of oil quality but also various toxicities, preventing the oxidation of edible oils is essential. Therefore understanding oxidation mechanisms that cause the formation of TGOOH is necessary. Since isomeric information of lipid hydroperoxide provides insights about oil oxidation mechanisms, we focused on dioleoyl-(hydroperoxy octadecadienoyl)-TG (OO-HpODE-TG) isomers, which are the primary oxidation products of the most abundant TG molecular species (dioleoyl-linoleoyl-TG) in canola oil. To secure highly selective and sensitive analysis, authentic OO-HpODE-TG isomer references (i.e., hydroperoxide positional/geometrical isomers) were synthesized and analyzed with HPLC-MS/MS. With the use of the method, photo- or thermal- oxidized edible oils were analyzed. While dioleoyl-(10-hydroperoxy-8E,12Z-octadecadienoyl)-TG (OO-(10-HpODE)-TG) and dioleoyl-(12-hydroperoxy-9Z,13E-octadecadienoyl)-TG (OO-(12-HpODE)-TG) were characteristically detected in photo-oxidized oils, dioleoyl-(9-hydroperoxy-10E,12E-octadecadienoyl)-TG and dioleoyl-(13-hydroperoxy-9E,11E-octadecadienoyl)-TG were found to increase depending on temperature in thermal-oxidized oils. These results prove that our methods not only evaluate oil oxidation in levels that are unquantifiable with peroxide value, but also allows for the determination of oil oxidation mechanisms. From the analysis of marketed canola oils, photo-oxidized products (i.e., OO-(10-HpODE)-TG and OO-(12-HpODE)-TG) were characteristically accumulated compared to the oil analyzed immediately after production. The method described in this paper is valuable in the understanding of oil and food oxidation mechanisms, and may be applied to the development of preventive methods against food deterioration.

Edible oils become rancid when reacting with oxygen under light or heat, degrading into different products depending on the pathway. Kiyotaka Nakagawa at Tohoku University, Japan, and co-workers used instruments that can separate and identify by weight components in mixtures to study light- and heat-induced oxidation of canola oil. Using authentic samples of possible oxidation products as references, the team found that each process generated two unique species from triacylglycerol, the main ingredient in edible oils. These signature compounds allowed the researchers to reveal that heat-oxidation sped up as temperature increased and that light-oxidized products gradually accumulated in off-the-shelf canola oil after production. This method is more sensitive than conventional protocols and can tell exactly how oils are oxidized, useful for developing techniques for food preservation.

Formation of potentially toxic carbonyls during oxidation of triolein in the presence of alimentary antioxidants

ABSTRACT

A relation between oil uptake and cancer as well as induction of hepatic inflammation was shown earlier. It is discussed that the main oil oxidation products-hydroperoxides and carbonyls-might be the reason for the mentioned diseases. In this manuscript quantitative determination of aldehydes which are formed during oxidation of triolein-as a model substance-using the Rancimat 679 is described. The oxidation of 11 g of triolein is carried out at 120 °C sparging air with a flow of 20 dm3/h for 10 h. A series of aliphatic aldehydes starting from hexanal to decanal as well as decenal was identified by LC-MS/MS and quantified as DNPH derivatives. In addition, the total amount of carbonyls was determined. Based on the calibration with hexanal, all other dominant substances were in the similar concentration range with maximum concentrations of 1.6 µmol/cm3 of hexanal, 2.3 µmol/cm3 of heptanal, 2.5 µmol/cm3 of octanal, 3.2 µmol/cm3 of nonanal, 4.0 µmol/cm3 of decanal after 6 h. The total amount of carbonyls reached a maximum after 6 h being 27 µmol/cm3 for triolein without antioxidant. The results of this investigation will be a basis for further toxicological studies on oxidized oils.

GRAPHICAL ABSTRACT

Oxidative stress mediates an increased formation of vascular endothelial growth factor in human hepatocarcinoma cells exposed to erlotinib

The tyrosine kinase inhibitor erlotinib targets the receptor of epidermal growth factor (EGFR) involved in development of hepatocellular carcinoma (HCC).

Although inefficient in established HCC, erlotinib has been recently proposed for HCC chemoprevention. Since Cyp3A4 and Cyp1A2 enzymes metabolize erlotinib in the liver, the insights into the mechanisms of erlotinib effects on liver cells with maintained drug metabolizing activity are needed.

We applied erlotinib to both commercially available (SNU398, Huh7) and established in Austria HCC cell lines (HCC-1.2, HCC-3). Cyp3A4 and Cyp1A2, microarray gene expression, cell viability, LDH release, DHFC fluorescence were assessed. VEGF expression was analysed by real-time RT-PCR and ELISA.

Higher cumulative expression of erlotinib metabolizing enzymes was observed in HCC-1.2 and HCC-3 cells. Gene expression microarray analysis showed upregulation of VEGF signalling by erlotinib. VEGF was increased up to 134 ± 14% (n = 5, p = 0.002) in HCC-1.2, HCC-3 and Huh7 cells. Interventions by Cyp1A2 and Mek2siRNA, MEK inhibitor UO126, diphenylene iodonium, as well as a combination of N-acetylcysteine with selenium all inhibited VEGF upregulation caused by erlotinib.

Thus, erlotinib increases VEGF production by mechanisms involving Cyp1A2, oxidative stress and MEK1/2. VEGF may favour angiogenesis and growth of early HCC tumours limiting the therapeutic and chemopreventive effects of erlotinib.

Mechanisms Linking Colorectal Cancer to the Consumption of (Processed) Red Meat: A Review

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world. The vast majority of CRC cases have been linked to environmental causes rather than to heritable genetic changes. Over the last decades, epidemiological evidence linking the consumption of red and, more convincingly, of processed red meat to CRC has accumulated. In parallel, hypotheses on carcinogenic mechanisms underlying an association between CRC and the intake of red and processed red meat have been proposed and investigated in biological studies. The hypotheses that have received most attention until now include (1) the presence of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines, two groups of compounds recognized as carcinogenic, (2) the enhancing effect of (nitrosyl)heme on the formation of carcinogenic N-nitroso compounds and lipid peroxidation. However, none of these hypotheses completely explains the link between red and processed red meat intake and the CRC risk. Consequently, scientists have proposed additional mechanisms or refined their hypotheses. This review first briefly summarizes the development of CRC followed by an in-depth overview and critical discussion of the different potential carcinogenic mechanisms underlying the increased CRC risk associated with the consumption of red and processed red meat.

Src Tyrosine Kinase Activation by 4-Hydroxynonenal Upregulates p38, ERK/AP-1 Signaling and COX-2 Expression in YPEN-1 Cells

4-Hydroxynonenal (4-HNE), a major end product of lipid peroxidation, is highly reactive and involved in various cellular processes, such as inflammatory signaling. However, to date, the mechanistic roles of 4-HNE in inflammatory signaling related to protein tyrosine kinases have not been elucidated. In the present study, we investigated the interaction between 4-HNE and Src (a non-receptor tyrosine kinase) for its involvement in the molecular modulation of the inflammatory signaling pathway utilizing the YPEN-1 cell system. Immunoprecipitation experiments showed that 4-HNE phosphorylates (activates) Src at Tyr416 via adduct formation. In addition, LC-MS/MS and a docking simulation model revealed an addiction site at the Cys248 residue of Src, resulting in the stimulation of downstream p38, ERK/AP-1 and cyclooxygenase-2 (COX-2) signaling in YPEN-1 cells. The role of 4-HNE-activated Src in downstream inflammatory signaling was further investigated using dasatinib (a Src inhibitor) and by siRNA knockdown of Src. p38 and ERK were directly regulated by Src, as revealed by immunoblotting of the phosphorylated forms of mitogen-activated protein kinases (MAPKs), which are key elements in the signaling transduction pathway initiated by Src. The study also shows that Src modulates the HNE-enhanced activation of AP-1 and the expression of COX-2 (a target gene of AP-1). Together, the results of this study show that 4-HNE stimulates Src tyrosine kinase in activation of the inflammation process.

Food-derived peroxidized fatty acids may trigger hepatic inflammation: a novel hypothesis to explain steatohepatitis

BACKGROUND & AIMS

Obesity and hepatic steatosis are frequently associated with the development of a non-alcoholic steatohepatitis (NASH). The mechanisms driving progression of a non-inflamed steatosis to NASH are largely unknown. Here, we investigated whether ingestion of peroxidized lipids, as being present in Western style diet, triggers the development of hepatic inflammation.

METHODS

Corn oil containing peroxidized fatty acids was administered to rats by gavage for 6 days. In a separate approach, hepatocytes (HC), endothelial (EC) and Kupffer cells (KC) were isolated from untreated livers, cultured, and incubated with peroxidized linoleic acid (LOOH; linoleic acid (LH) being the main fatty acid in corn oil). Samples obtained from in vivo and in vitro studies were mainly investigated by qRT-PCR and biochemical determinations of lipid peroxidation products.

RESULTS

Rat treatment with peroxidized corn oil resulted in increased hepatic lipid peroxidation, upregulation of nitric oxide synthetase-2 (NOS-2), cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNFα), elevation of total nitric oxides, and increase in cd68-, cd163-, TNFα-, and/or COX-2 positive immune cells in the liver. When investigating liver cell types, LOOH elevated the secretion of TNFα, p38MAPK phosphorylation, and mRNA levels of NOS-2, COX-2, and TNFα, mainly in KC. The elevation of gene expression could be abrogated by inhibiting p38MAPK, which indicates that p38MAPK activation is involved in the pro-inflammatory effects of LOOH.

CONCLUSIONS

These data show for the first time that ingestion of peroxidized fatty acids carries a considerable pro-inflammatory stimulus into the body which reaches the liver and may trigger the development of hepatic inflammation.

Protection against cyclophosphamide-induced myelosuppression by ZPDC glycoprotein (24 kDa)

Immunomodulatory agents are often used to reduce myelosuppression and enhance immune response for cancer treatment. Cyclophosphamide (CTX) can induce oxidative stress in bone marrow resulting in suppression of anti-oxdiantive enzymes and causes myelosuppression. We isolated glycoprotein from Zanthoxylum piperitum DC fruit (ZPDC), and it consists of a carbohydrate (18%) and a protein (82%). The objective of this study was to investigate its protective activity against CTX-induced myelosuppression in Balb/c (n=6/group). The mice were orally administrated by ZPDC glycoprotein (10 and 20 mg/kg, BW) for 1 week in the presence or absence of CTX. Intracellular reactive oxygen species (ROS), anti-oxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT)], cyclin kinase inhibitors (CKIs: p53, p21 and p27), cyclin D1/ cyclin dependent kinase (CDK) 4, PCNA and cytokines [interleukin (IL)-3, and granulocyte⁄ macrophage-colony-stimulating factor (GM-CSF)] were evaluated using biochemical activity, Western blot analysis, and ELISA. The results obtained from this study showed that CTX decreased spleen and thymic indices, bone marrow cellularity and expression of cyclin D1/CDK4 and PCNA, but it increased CKIs, whereas ZPDC glycoprotein (20 mg/kg, BW) resulted in vice versa in CTX-induced Balb/c. Expression of IL-3 and GM-CSF were normalized by ZPDC glycoprotein. Thus, this study suggested that ZPDC glycoprotein prevents oxidative stress and myelosuppression in CTX-induced mice and might be a potential immunomodulatory agent.

Antagonistic effects of selenium and lipid peroxides on growth control in early hepatocellular carcinoma

Activation of the activator protein 1 (AP-1) transcription factor as well as increased serum levels of vascular endothelial growth factor (VEGF) and interleukin (IL)-8 predict poor prognosis of patients with hepatocellular carcinomas (HCCs). Moreover, HCC patients display reduced selenium levels, which may cause lipid peroxidation and oxidative stress because selenium is an essential component of antioxidative glutathione peroxidases (GPx). We hypothesized that selenium-lipid peroxide antagonism controls the above prognostic markers and tumor growth. (1) In human HCC cell lines (HCC-1.2, HCC-3, and SNU398) linoleic acid peroxide (LOOH) and other prooxidants enhanced the expression of VEGF and IL-8. LOOH up-regulated AP-1 activation. Selenium inhibited these effects. This inhibition was mediated by glutathione peroxidase 4 (GPx4), which preferentially degrades lipid peroxides. Selenium enhanced GPx4 expression and total GPx activity, while knock-down of GPx4 by small interfering RNA (siRNA) increased VEGF, and IL-8 expression. (2) These results were confirmed in a rat hepatocarcinogenesis model. Selenium treatment during tumor promotion increased hepatic GPx4 expression and reduced the expression of VEGF and of the AP-1 component c-fos as well as nodule growth. (3) In HCC patients, increased levels of LOOH-related antibodies (LOOH-Ab) were found, suggesting enhanced LOOH formation. LOOH-Ab correlated with serum VEGF and IL-8 and with AP-1 activation in HCC tissue. In contrast, selenium inversely correlated with VEGF, IL-8, and HCC size (the latter only for tumors smaller than 3 cm).

CONCLUSION

Reduced selenium levels result in accumulation of lipid peroxides. This leads to enhanced AP-1 activation and consequently to elevated expression of VEGF and IL-8, which accelerate the growth of HCC. Selenium supplementation could be considered for investigation as a strategy for chemoprevention or additional therapy of early HCC in patients with low selenium levels.

Activity of tumor necrosis factor-α blocked by phytoglycoprotein (38 kDa) at initiation stage in N-nitrosodiethylamine-induced ICR mice

Hepatocellular carcinoma is becoming one of the most prominent types of cancer in the world. Recently, from Styrax japonica Siebold et al. Zuccarini (SJSZ), we isolated a glycoprotein which consists of carbohydrate moiety (52.64%) and protein moiety (42.35%). We evaluated whether SJSZ glycoprotein prevents hepatocarcinogenesis induced by N-nitrosodiethylamine (DEN). The purpose of this study was to evaluate the effect of SJSZ glycoprotein in DEN-induced hepatocarcinogenesis in ICR mice. To know chemopreventive effect of SJSZ glycoprotein on hepatocarcinogenesis, ICR mice were intraperitoneally injected with N-nitrosodiethylamine (DEN, 10 mg/kg) for 7 weeks. After sacrifice, we evaluated indicators of liver tissue damage [the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT), and thiobarbituric acid reactive substances (TBARS)], antioxidative enzymes [activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)], and initiating hepatocarcinogenic indicator [heat shock protein (HSP) 27 and 70] and hepatocarcinogenic signals [protein kinase C (PKC), extracellular signal-regulating kinase (ERK) 1/2, nuclear factor (NF)-κB (p50 and p65) and tumor necrosis factor-α (TNF-α)] using biochemical methods, immunoblot analysis, and RT-PCR. The results obtained from this study revealed that SJSZ glycoprotein (10 mg/kg, BW) decreased the levels of LDH, ALT, and TBARS, whereas the activities of SOD, GPx, and CAT increased in the DEN-induced ICR mice. With respect to the hepatocarcinogenic indicator and hepatocarcinogenic signals, HSP27, HSP70, PKC, ERK1/2, NF-κB (p50 and p65), and TNF-α, activity decreased. Hence, SJSZ glycoprotein might prevent expression of HSP27 and HSP70 by DEN.

Inhibitory effect of SJSZ glycoprotein (38 kDa) on expression of heat shock protein 27 and 70 in chromium (VI)-treated hepatocytes

Chromium (VI) is as an extremely toxic chemical substance, and is also an internationally recognized human carcinogen. The principal objective of this study was to determine whether or not Styrax japonica Siebold et al. Zuccarini (SJSZ) glycoprotein prevents hepatocarcinogenesis in chromium-treated BNL CL.2 cells and ICR mice. Firstly, it was evaluated that SJSZ glycoprotein has strong antioxidant character and scavenges radicals. In an effort to assess the chemopreventive effects of SJSZ glycoprotein on hepatocarcinogenesis, ICR mice were intraperitoneally injected with chromium (10 mg/kg, BW) for 8 weeks. After sacrifice, we evaluated indicators of liver tissue damage [the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT), and thiobarbituric acid-reactive substances (TBARS)], antioxidative enzymes [activities of superoxide dismutase (SOD), catalase (CAT) and gluthathione peroxidase (GPx)], and initiating hepatocarcinogenic indicator [heat shock protein (HSP) 27 and 70] and protein kinase C (PKC), p38 MAPK and PCNA via biochemical methods and immunoblot analysis. The results obtained from this study demonstrated that the SJSZ glycoprotein (50 μg/ml) inhibited the production of intracellular ROS in BNL CL.2 cells. In addition, the SJSZ glycoprotein (10 mg/kg, BW) attenuated the levels of LDH, ALT, and TBARS, whereas it increased antioxidative enzymes in mouse serum. SJSZ glycoprotein attenuated the activity of HSP27, HSP70, PKC, MAPKs, and PCNA in BNL CL.2 cells and liver tissue. Taken together, our results indicate that SJSZ glycoprotein might be have a potent preventive effect against hepatocarcinogenesis induced by oxidative stress.

Lipid hydroperoxide-induced and hemoglobin-enhanced oxidative damage to colon cancer cells

Epidemiological studies have indicated that Western diets are related to an increase in a series of malignancies. Among the compounds that are credited for this toxic effect are heme and lipid peroxides. We evaluated the effects of hemoglobin (Hb) and linoleic acid hydroperoxides (LAOOH) on a series of toxicological endpoints, such as cytotoxicity, redox status, lipid peroxidation, and DNA damage. We demonstrated that the preincubation of SW480 cells with Hb and its subsequent exposure to LAOOH (Hb + LAOOH) led to an increase in cell death, DCFH oxidation, malonaldehyde formation, and DNA fragmentation and that these effects were related to the peroxide group and the heme present in Hb. Furthermore, Hb and LAOOH alone exerted a toxic effect on the endpoints assayed only at concentrations higher than 100 μM. We were also able to show that SW480 cells presented a higher level of the modified DNA bases 8-oxo-7,8-dihydro-2'-deoxyguanosine and 1,N(2)-etheno-2'-deoxyguanosine compared to the control. Furthermore, incubations with Hb led to an increase in intracellular iron levels, and this high level of iron correlated with DNA oxidation, as measured as EndoIII- and Fpg-sensitive sites. Thus, Hb from either red meat or bowel bleeding could act as an enhancer of fatty acid hydroperoxide genotoxicity, which contributes to the accumulation of DNA lesions in colon cancer cells.

Inhibitory effect of phytoglycoprotein (24 kDa) on hepatocarcinogenesis in N-nitrosodiethylamine-treated ICR mice

Objectives

Hepatocellular carcinoma (HCC) is becoming one of the most prominent types of cancer in the world. For a long time in Korea Zanthoxylum piperitum DC (ZPDC) has been used in folk medicine to cure several cancers and inflammation. This study was designed to investigate whether ZPDC glycoprotein protected liver tissues against hepatocarcinogenic compounds such as N-nitrosodiethylamine (DEN).

Methods

To study the chemopreventive effect of ZPDC glycoprotein on hepatocarcinogenesis, ICR mice were injected intraperitoneally with DEN (50 mg/kg) for four weeks. We evaluated the indicators of liver tissue damage (the activity of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT), and thiobarbituric acid-reactive substances (TBARS)), antioxidative enzymes (activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx)), hepatocarcinogenic indicator (heat shock protein (HSP) 70) and hepatocarcinogenic signals (activity of nuclear factor (NF)-κB, cyclooxygenase (COX)-2, and matrix metalloproteinase (MMP)-9) using biochemical methods and immunoblot analysis.

Key findings

The results obtained from this study revealed that ZPDC glycoprotein (20 mg/kg) decreased the levels of LDH, ALT, and TBARS, whereas the activity of SOD and GPx increased in the DEN-treated ICR mice. With respect to the hepatocarcinogenic indicator and hepatocarcinogenic signals, HSP70, NF-κB, COX-2, and MMP-9 activity decreased.

Conclusion

The findings suggested that ZPDC glycoprotein prevented damage to liver tissue caused by DEN in the experimental mouse model.

Mechanisms of tumor promotion by reactive oxygen species

This review analyzes the available information concerning mechanisms of non-genotoxic action of reactive oxygen species (ROS) during tumor promotion and pathways of their generation under the influence of chemical compounds. Special attention is given to the ability of ROS to induce pseudohypoxia through inhibition of prolyl oxidase, which is an oxygen sensor in the cell. Functions of HIF-1alpha as a main contributor to the ROS-induced promotion are analyzed. Data suggest that an unregulated high level of HIF-1alpha in the cell could induce the development of tumors. Hypothetical possibilities of ROS production under the influence of different environmental pollutants, which are promoters of tumorigenesis, include functioning of cytochrome P450 during oxidation of substrates, functioning of the mitochondrial respiratory chain, and action of peroxisome proliferators.

Elevated dietary linoleic acid increases gastric carcinoma cell invasion and metastasis in mice

BACKGROUND

Dietary (n-6)-polyunsaturated fatty acids influence cancer development, but the mechanisms have not been well characterised in gastric carcinoma.

METHODS

We used two in vivo models to investigate the effects of these common dietary components on tumour metastasis. In a model of experimental metastasis, immunocompromised mice were fed diets containing linoleic acid (LA) at 2% (LLA), 8% (HLA) or 12% (VHLA) by weight and inoculated intraperitoneally (i.p.) with human gastric carcinoma cells (OCUM-2MD3). To model spontaneous metastasis, OCUM-2MD3 tumours were grafted onto the stomach walls of mice fed with the different diets. In in vitro assays, we investigated invasion and ERK phosphorylation of OCUM-2MD3 cells in the presence or absence of LA. Finally, we tested whether a cyclooxygenase (COX) inhibitor, indomethacin, could block peritoneal metastasis in vivo.

RESULTS

Both the HLA and VHLA groups showed increased incidence of tumour nodules (LA: 53%; HLA: 89%; VHLA: 100%; P<0.03); the VHLA group also displayed increased numbers of tumour nodules and higher total volume relative to LLA group in experimental metastasis model. Both liver invasion (78%) and metastasis to the peritoneal cavity (67%) were more frequent in VHLA group compared with the LLA group (22% and 11%, respectively; P<0.03) in spontaneous metastasis model. We also found that the invasive ability of these cells is greatly enhanced when exposed to LA in vitro. Linoleic acid also increased invasion of other scirrhous gastric carcinoma cells, OCUM-12, NUGC3 and MKN-45. Linoleic acid effect on OCUM-2MD3 cells seems to be dependent on phosphorylation of ERK. The data suggest that invasion and phosphorylation of ERK were dependent on COX. Indomethacin decreased the number of tumours and total tumour volume in both LLA and VHLA groups. Finally, COX-1, which is known to be an important enzyme in the generation of bioactive metabolites from dietary fatty acids, appears to be responsible for the increased metastatic behaviour of OCUM-2MD3 cells in the mouse model.

CONCLUSION

Dietary LA stimulates invasion and peritoneal metastasis of gastric carcinoma cells through COX-catalysed metabolism and activation of ERK, steps that compose pathway potentially amenable to therapeutic intervention.

Endogenous antioxidants and radical scavengers

All living organisms are constantly exposed to oxidant agents deriving from both endogenous and exogenous sources capable to modify biomolecules and induce damages. Free radicals generated by oxidative stress exert an important role in the development of tissue damage and aging. Reactive species (RS) derived from oxygen (ROS) and nitrogen (RNS) pertain to free radicals family and are constituted by various forms of activated oxygen or nitrogen. RS are continuosly produced during normal physiological events but can be removed by antioxidant defence mechanism: the imbalance between RS and antioxidant defence mechanism leads to modifications in cellular membrane or intracellular molecules. In this chapter only endogenous antioxidant molecules will be critically discussed, such as Glutathione, Alpha-lipoic acid, Coenzyme Q, Ferritin, Uric acid, Bilirubin, Metallothioneine, L-carnitine and Melatonin.