Vascular endothelial growth factor protects hepatoma cells against oxidative stress-induced cell death

Determining timing of hepatectomy for colorectal cancer with distant metastasis according to imaging-based tumor shrinkage ratio

BACKGROUND

The optimal timing of surgical resection of liver metastasis remains controversial, and guidelines regarding the upper limits of operative indications have not yet been defined. Surgical indication for metastasis from colorectal cancer (CLM) based on results of preoperative chemotherapy and RNF8 was investigated.

METHODS

Differences in CLM size on CT were evaluated as shrinkage rate/day by dividing tumor shrinkage rates by the interval in days between CT. Levels of RNF8 of resected colorectal cancer and CLM frozen specimen were detected.

RESULTS

When the cut line for shrinkage rate at 12 weeks was set at 0.35%, disease-free survival was significantly better in patients with a shrinkage rate >0.35% vs. ≤0.35% (p=0.003). RNF8 expression was significantly higher in Tis (p=0.001). In liver metastasis, RNF8 expression level was significantly lower in patients with partial response to FOLFOX than with stable disease, (p=0.017).

CONCLUSIONS

A strategy of FOLFOX administration for 12 weeks to patients with low RNF8 expression and hepatectomy planned after 4 weeks rest may be accepted as the best therapeutic option for treating CLM.

Extracellular signal-regulated kinase and Akt activation play a critical role in the process of hepatocyte growth factor-induced epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) has recently been studied to elucidate mechanisms of the liver metastatic process. We investigated EMT in the process of liver metastasis and the effects of chemotherapy on EMT cells as therapeutic strategy for colorectal liver metastasis. We used the CT26 murine colorectal carcinoma cell line to create an in vivo mouse liver metastasis model. Liver tumors were stained immuno-histochemically. Expression of proteins associated with TGF-β/Smad and hepatocyte growth factor (HGF)/c-Met pathways were investigated by western blotting. Cells with c-Met mRNA knockdown by siRNA techniques showed clearly reduced liver metastases compared with regular cells at 21 days. TGF-β and HGF induced EMT expression, but signal transduction was quite different. TGF-β induced ERK, but not Akt phosphory-lation. HGF mediated both ERK and Akt phosphorylation. Akt inhibitor blocked Akt phosphorylation but did not affect TGF-β-induced activation of ERK, Snail and Slug. U-0126 did not reduce Snail activity by TGF-β at a concentration to block ERK phosphorylation. However, Akt inhibitor and U-0126 completely inhibited HGF-induced Slug activation. 5-FU mediated cell death in the EMT process induced by TGF-β more effectively than HGF. ERK/Akt signaling, but not the Smad pathway, may be one of the main processes in HGF-induced EMT, despite the Smad pathway, but not ERK/Akt, being critical for TGF-β-induced EMT. The MAPK/Akt pathway is indispensable in HGF/c-Met signaling. The ERK/Akt pathway particularly may be critical in the HGF-induced EMT process. However, long-term use of chemotherapeutic agents may induce drug resistance and distant metastases through EMT-related signaling pathway activation.

Shark cartilage extract induces cytokines expression and release in endothelial cells and induces E-selectin, plasminogen and t-PA genes expression through an antioxidant-sensitive mechanism

Neovastat® is a standardized extract of marine cartilage, an avascular tissue, which contains many biologically active molecules and has multiple antiangiogenic properties. In addition to VEGFR2 and MMPs inhibition, shark cartilage extract (SCE) has recently been shown to induce tissue plasminogen activator gene (PLAT) expression in bovine endothelial cells in a TNF like manner, by inducing the typical mediators NF-κB and JNK. There is now compelling evidences that the NF-κB and JNK pathways are activated by cytokines induced generation of reactive oxygen species (ROS). We used macroarray genes expression analysis on human umbilical vein endothelial cells, to investigate if that mechanism could mediate the effect of SCE. Transcriptomic results showed that SCE induced expression of several cytokines. Their impact must be important, given that treatment of endothelial cells with the cytokine TNF-α was able to reproduce most of the effects of cartilage extract on genes expression. In addition, most of the genes, known to be inducible by NF-κB or JNK following cytokines stimulation, were less induced by SCE when endothelial cells were pretreated with the antioxidant N-Acetylcysteine (NAC), suggesting a role of ROS in endothelial cell activation by SCE. Finally, the possible effects of PLAT, PLG, SELE, IL8 and PRDX2 (those validated by q-PCR) on angiogenesis, will also be discussed.

Oxidative stress, endogenous antioxidants, alcohol, and hepatitis C: pathogenic interactions and therapeutic considerations

Hepatitis C virus (HCV) is a blood-borne pathogen that was identified as an etiologic agent of non-A, non-B hepatitis in 1989. HCV is estimated to have infected at least 170 million people worldwide. The majority of patients infected with HCV do not clear the virus and become chronically infected, and chronic HCV infection increases the risk for hepatic steatosis, cirrhosis, and hepatocellular carcinoma. HCV induces oxidative/nitrosative stress from multiple sources, including inducible nitric oxide synthase, the mitochondrial electron transport chain, hepatocyte NAD(P)H oxidases, and inflammation, while decreasing glutathione. The cumulative oxidative burden is likely to promote both hepatic and extrahepatic conditions precipitated by HCV through a combination of local and more distal effects of reactive species, and clinical, animal, and in vitro studies strongly point to a role of oxidative/nitrosative stress in HCV-induced pathogenesis. Oxidative stress and hepatopathogenesis induced by HCV are exacerbated by even low doses of alcohol. Alcohol and reactive species may have other effects on hepatitis C patients such as modulation of the host immune system, viral replication, and positive selection of HCV sequence variants that contribute to antiviral resistance. This review summarizes the current understanding of redox interactions of HCV, outlining key experimental findings, directions for future research, and potential applications to therapy.

Ethanol and reactive species increase basal sequence heterogeneity of hepatitis C virus and produce variants with reduced susceptibility to antivirals

Hepatitis C virus (HCV) exhibits a high level of genetic variability, and variants with reduced susceptibility to antivirals can occur even before treatment begins. In addition, alcohol decreases efficacy of antiviral therapy and increases sequence heterogeneity of HCV RNA but how ethanol affects HCV sequence is unknown. Ethanol metabolism and HCV infection increase the level of reactive species that can alter cell metabolism, modify signaling, and potentially act as mutagen to the viral RNA. Therefore, we investigated whether ethanol and reactive species affected the basal sequence variability of HCV RNA in hepatocytes. Human hepatoma cells supporting a continuous replication of genotype 1b HCV RNA (Con1, AJ242652) were exposed to ethanol, acetaldehyde, hydrogen peroxide, or L-buthionine-S,R-sulfoximine (BSO) that decreases intracellular glutathione as seen in patients. Then, NS5A region was sequenced and compared with genotype 1b HCV sequences in the database. Ethanol and BSO elevated nucleotide and amino acid substitution rates of HCV RNA by 4-18 folds within 48 hrs which were accompanied by oxidative RNA damage. Iron chelator and glutathione ester decreased both RNA damage and mutation rates. Furthermore, infectious HCV and HCV core gene were sufficient to induce oxidative RNA damage even in the absence of ethanol or BSO. Interestingly, the dn/ds ratio and percentage of sites undergoing positive selection increased with ethanol and BSO, resulting in an increased detection of NS5A variants with reduced susceptibility to interferon alpha, cyclosporine, and ribavirin and others implicated in immune tolerance and modulation of viral replication. Therefore, alcohol is likely to synergize with virus-induced oxidative/nitrosative stress to modulate the basal mutation rate of HCV. Positive selection induced by alcohol and reactive species may contribute to antiviral resistance.

Enhanced expression of vascular endothelial growth factor-A in ground glass hepatocytes and its implication in hepatitis B virus hepatocarcinogenesis

Ground glass hepatocytes (GGH) in chronic hepatitis B virus (HBV) infection harbor HBV pre-S deletion mutants in endoplasmic reticulum (ER) and exhibit complex biologic features such as ER stress, DNA damage, and growth advantage. The presence of pre-S mutants in serum has been shown to predict the development of hepatocellular carcinoma (HCC) in HBV carriers. GGHs hence represent a potentially preneoplastic lesion. Whether a specific growth factor is overexpressed and activated in GGHs remains to be clarified. In this study, growth factor(s) up-regulated by pre-S mutants was identified using a growth factor array in HuH-7 cells. Immunohistochemistry, reverse-transcriptase polymerase chain reaction, and Western blot analysis were performed to study the participation of these genes and their signal pathways in HuH-7 cells and liver tissues. We demonstrate that vascular endothelial growth factor-A (VEGF-A) was up-regulated by pre-S mutants in HuH-7 cells and further confirmed in GGHs by immunostaining. The VEGF-A up-regulation by pre-S mutants could be suppressed by vomitoxin, an ER stress inhibitor. Furthermore, pre-S mutants-expressed HuH-7 cells exhibited activation of Akt/mTOR (mammalian target of rapamycin) signaling and increased growth advantage, which could be inhibited by VEGF-A neutralization. Consistent with this notion, enhanced expression of VEGF-A and activation of Akt/mTOR signaling, comparable to the levels of paired HCC tissues, were also detected in HBV-related nontumorous livers.

CONCLUSION

The enhanced expression of VEGF-A in GGHs provides potential mechanism to explain the progression from preneoplastic GGHs to HCC in chronic HBV infection.

Clinicopathological features of hepatocellular carcinoma evaluated by vascular endothelial growth factor expression

AIM

To evaluate the significance of the expression of vascular endothelial growth factor (VEGF), its correlation with clinicopathological variables were studied in the tissue of hepatocellular carcinoma (HCC) and surrounding liver.

METHODS

In 56 samples (tumor and non-tumor liver tissue) collected from 28 patients, VEGF expression was examined by immunohistochemistry and western blot analysis.

RESULTS

The value of VEGF expression by western blotting was correlated with immunohistochemical staining grade. In tumor tissue, the value of VEGF expression correlated with tumor size (P = 0.034), á-fetoprotein (P = 0.036) and protein induced by vitamin K absence-II by simple regression, and histological grade (P = 0.0132) by the unpaired t-test. The level of VEGF expression in non-tumor liver was found to correlate with the value of serum albumin (P = 0.008), cholinesterase (P = 0.012) and prothrombin activity (P = 0.046). The frequency of simple nodular type in gross appearance decreased in cases with high tumor/non-tumor (T/N) ratio (P = 0.022), and the degree of portal vein invasion progressed with an increase in the T/N ratio (P = 0.008). The T/N ratio was significantly higher in early recurrence cases (P = 0.0081).

CONCLUSION

This study on the expression of VEGF might be useful to estimate the liver condition and the clinicopathological features of HCC.

The effect of p53 gene expression on the inhibition of cell proliferation by paclitaxel

BACKGROUND/AIMS

We evaluated the relationship between p53 status and paclitaxel (PTX)-induced inhibition of the growth of human stomach cancer cells.

MATERIALS AND METHODS

We made use of two human stomach cancer cell lines, MKN45 and MKN28. Growth inhibition in response to PTX was evaluated by MTT method. We used flow cytometry to monitor the cell cycle and western blot analysis to evaluate the expression of signaling molecules.

RESULTS

PTX inhibited the proliferation of both stomach cancer cell lines in a dose-dependent manner. However, PTX cytotoxicity was stronger in MKN28 cells. Flow cytometric analysis showed that 1 muM PTX enhanced the percentage of MKN 45 cells in the sub-G1 phase of the cell cycle, whereas it increased the percentage of MKN 28 cells arrested at G2/M phase. 1 muM PTX was found to increase cyclin B1 production in MKN28 cells, but not in MKN 45 cells. In contrast, PTX-treatment led to an increase in the cleaved form of caspase-3 in MKN45, but not MKN28 cells. An inhibitor of p53, pifithrin-alpha, antagonized the expression of the cleaved form of caspase-3 in MKN45 cells.

CONCLUSION

Both p53 status and cyclin-B1 expression might be useful for predicting the therapeutic response of stomach cancer to PTX.

Extracellular signal-regulated kinase phosphorylation due to menadione-induced arylation mediates growth inhibition of pancreas cancer cells

BACKGROUND

Cytotoxicity of Vitamin K3 (VK3) is indicated to have the same mechanism with oxidative stress (H(2)O(2)). In the present study, we analyzed the differences and/or similarities in the cellular responses to oxidative stress and VK3 to clarify the mechanism of growth inhibition.

METHODS

Cell viability was determined by a test method with 3-[4, 5-dimethyl-thiazol]-2, 5-dephenyl tetrazolium bromide (MTT). Expressions of cellular proteins were evaluated by Western blot analysis.

RESULTS

The IC50 was calculated to be 47.3 +/- 4.1 microM for VK3 and 2.2 +/- 1.2 microM for H(2)O(2). By Western blot analysis, VK3 or H(2)O(2) was shown to induce rapid phosphorylation of extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinases (JNKs). H(2)O(2)-induced phosphorylation of ERK and JNK was almost complete inhibited by more than 100-muM genistein. VK3-induced JNK phosphorylation was blocked by 100-microM genistein, but ERK phosphorylation was not inhibited completely even if 400-microM genistein was used. H(2)O(2)-induced inhibition of cell proliferation was completely blocked by 400-microM genistein, but the VK3 effect was reduced 72.8 +/- 5.4% by the same concentration of genistein. H(2)O(2)-induced JNK phosphorylation and ERK phosphorylation were inhibited by staurosporine, protein kinase C (PKC) inhibitor. VK3-induced JNK phosphorylation was also blocked, but ERK phosphorylation was not affected. Staurosporine had no effect on VK3- or H(2)O(2)-induced growth inhibition. Treatment with a non-thiol antioxidant agent, catalase, completely abrogated H(2)O(2)-induced JNK and ERK phosphorylation, but a thiol antioxidant, L: -cystein, had no effect on phosphorylation of them. The VK3-induced JNK phosphorylation was inhibited by catalase, but not L: -cystein. But ERK phosphorylation was not inhibited by catalase and was abrogated completely by the thiol antioxidant. Catalase, but not L: -cystein, blocked H(2)O(2)-induced growth inhibition, and L: -cystein, but not catalase, blocked VK3-induced effects on cell proliferation completely.

CONCLUSION

VK3-induced ERK phosphorylation occurs by a different mechanism from oxidative stress, and it might have an important role to induce growth inhibition.