Angiogenesis effect on rat liver after administration of expression vector encoding vascular endothelial growth factor D

[Tumor hypoxia: the role of HIF]

Solid tumors usually occur and progress in a hypoxic environment, suggesting that tumor cells are resistant to apoptosis and are associated to an increased angiogenesis, which makes them more aggressive, with invasive capacity and resistant to treatment. The genetic and biological mechanisms underlying this phenomenon are still unclear, but many studies suggest a role of HIF in this process. Under hypoxic conditions, the alpha subunit is not destroyed, and will activate transcription of a set of genes contributing to tumor aggressiveness. Its expression is associated to an increased metastatic potential that has been shown in both animal studies and human tumors. Tumor hypoxia has emerged as a key factor in tumor progression and is associated to a poor prognosis, particularly in kidney and prostate tumors. The purpose of this study was to review the significance of hypoxia in carcinogenesis and tumor progression by reviewing the current knowledge on the subject and the mechanisms of action and activation of HIF-1a Tumor hypoxia has emerged as a key factor in tumor progression and is associated to a poor prognosis, particularly in kidney and prostate tumors. The purpose of this study was to review the significance of hypoxia in carcinogenesis and tumor progression by reviewing the current knowledge on the subject and the mechanisms of action and activation of HIF-1a.

Cloning, large-scale production, and purification of active dimeric rat vascular endothelial growth factor (rrVEGF-164)

Large-scale production of recombinant rat vascular endothelial growth factor (rrVEGF-164) is desirable for angiogenic studies. In this study, biologically active recombinant rat vascular endothelial growth factor (rrVEGF-164) was cloned and expressed in the yeast Pichia pastoris, and large-scale production was performed by fermentation. cDNA encoding VEGF-164 was prepared from embryonic rat tissue RNA, and a recombinant pPIC9HV/rVEGF-164 plasmid, containing an AOX1 promoter, was constructed. The methylotrophic P. pastoris was used as the eukaryotic expression system. After transformation, rrVEGF-164 was produced by fermentation ( approximately 124mg/L) and purified by heparin affinity chromatography. SDS-PAGE indicated that rrVEGF-164 was produced as a disulphide-bridged dimer of 48kDa which was purified to near homogeneity by heparin affinity chromatography in a large quantity. A bioassay indicated a three- to fivefold increase in endothelial cell proliferation after 3days, due to the addition of the produced rrVEGF-164. The produced rrVEGF-164 showed a higher biological activity than a commercially available, mouse cell line-based, growth factor. In conclusion, using the P. pastoris expression system we were able to produce biologically active rat VEGF-164 in high quantities and this may provide a powerful tool for basic and applied life sciences.

Vascular endothelial growth factor attenuates hepatic sinusoidal capillarization in thioacetamide-induced cirrhotic rats

AIM: To investigate the effect of vascular endothelial growth factor (VEGF) transfection on hepatic sinusoidal capillarization.

METHODS: Enhanced green fluorescent protein (EGFP)/VEGF transfection was confirmed by immunofluorescence microscopy and immunohistoche-mistry both in primary hepatocytes and in normal liver. Cirrhotic rats were generated by thioacetamide (TAA) administration and then divided into a treatment group, which received injections of 400 &mgr;g of plasmid DNA encoding an EGFP-VEGF fusion protein, and a blank group, which received an equal amount of normal saline through the portal vein. The portal vein pressure was measured in the normal and cirrhotic state, in treated and blank groups. The average number of fenestrae per hepatic sinusoid was determined using transmission electron microscopy (TEM), while the relative abundance of VEGF transcripts was examined by Gene array.

RESULTS: Green fluorescent protein was observed in the cytoplasms of liver cells under immunofluorescence microscopy 24 h after transfection with EGFP/VEGF plasmid in vitro. Staining with polyclonal antibodies against VEGF illustrated that hepatocytes expressed immunodetectable VEGF both in vitro and in vitro. There were significant differences in the number of fenestrae and portal vein pressures between normal and cirrhotic rats (7.40 ± 1.71 vs 2.30 ± 1.16 and 9.32 ± 0.85 cmH₂O vs 17.92 ± 0.90 cmH₂O, P < 0.01), between cirrhotic and treated rats (2.30 ± 1.16 cmH₂O vs 4.60 ± 1.65 and 17.92 ± 0.90 cmH₂O vs 15.52 ± 0.93 cmH₂O, P < 0.05) and between the treatment group and the blank group (4.60 ± 1.65 cmH₂O vs 2.10 ± 1.10 cmH₂O and 15.52 ± 0.93 cmH₂O vs 17.26 ± 1.80 cmH₂O, P < 0.05). Gene-array analysis revealed that the relative abundance of transcripts of VEGF family members decreased in the cirrhotic state and increased after transfection.

CONCLUSION: Injection of a plasmid encoding VEGF through the portal vein is an effective method to induce the formation of fenestrae and decrease portal vein pressure in cirrhotic rats. Therefore, it may be a good choice for treating hepatic cirrhosis and portal hypertension.

[Development of blood vessels of the greater omentum in the hepatic lobe after vascular ligation. An experimental model in the rats]

PURPOSE

To verify the development of blood vessels between the greater omentum and the liver in the presence of distinct liver blood intake blockages.

METHODS

Two hundred and eighty conventional male Wistar rats were used, divided into 5 groups: control (n=35), laparotomy (n=35); hepatic artery ligature (n=70), ligature of the right-hand branch of the portal vein (n=70); and ligature of both blood vessels (n=70). The last three groups were divided into two subgroups each (n=35), according to the presence or absence of the transposition of the greater omentum onto the right hepatic lobe. The postoperative periods were 1, 3, 7, 15, 30, 60 and 90 days. At the end of each period, the greater omentum and right hepatic lobe were collected for histopathological examination. The presence of blood vessels between the referred tissues was verified by the administration of Indian ink as a marker of vascular lumen.

RESULTS

Macroscopic and microscopic observation and the dye marker demonstrated the distribution of blood vessels between the greater omentum and liver tissues.

CONCLUSION

The greater omentum was capable of developing blood vessels when fixed to the parenchyma of the liver after the suppression of hepatic blood flow.

Effect of arsenic trioxide on vascularization of tumor

AIM: To explore the effects and mechanisms of anti-vascularization of arsenic trioxide (As₂O₃) injection on the human hepatocellular carcinoma (HCC) cells.

METHODS: Human umbilical vein cell line ECV304 and the nude mice with the high metastastic human HCC transplanted in situ LCI-D20 were used. The growth of ECV304 was analyzed by MTT assay. The inhibitory effect of As₂O₃ on tumor neo-vascularization was investigated by the method of chick chorioallantoic membrane (CAM). The changes of VEGF's expression in the transplanted HCC tissue were investigated by using immunohistochemical SP staining.

RESULTS: As₂O₃ could inhibit the growth of ECV304 cell line, and down-regulate VEGF's expression. As₂O₃ could also inhibit the vascularization in the CAM, and electron microscopy showed that As₂O₃ could damage primitive mesenchymal cells and vascular endothelial cells, and inhibite neovascular gemmation. The expression of VEGF was down-regulated in vivo studies.

CONCLUSION: As₂O₃ injection can inhibit the tumor neovascularization by supressing the growth of vascular endothelial cell, down-regulating the expression of VEGF, damaging the primitive mesenchymal cells and inhibiting neovascular fromation.

Spider angiomas in patients with liver cirrhosis: Role of vascular endothelial growth factor and basic fibroblast growth factor

AIM: To investigate whether vascular endothelial growth factor (VEGF) and basic fibroblastic growth factor (bFGF) are associated with spider angiomas in patients with liver cirrhosis.

METHODS: Eighty-six patients with liver cirrhosis were enrolled and the number and size of the spider angiomas were recorded. Fifty-three healthy subjects were selected as controls. Plasma levels of VEGF and bFGF were measured in both the cirrhotics and the controls.

RESULTS: Plasma VEGF and bFGF were increased in cirrhotics compared with controls (122 ± 13 vs. 71 ± 11 pg/mL, P = 0.003 for VEGF; 5.1 ± 0.5 vs. 3.4 ± 0.5 pg/mL, P = 0.022 for bFGF). In cirrhotics, plasma VEGF and bFGF were also higher in patients with spider angiomas compared with patients without spider angiomas (185 ± 28 vs. 90 ± 10 pg/mL, P = 0.003 for VEGF; 6.8 ± 1.0 vs. 4.1 ± 0.5 pg/mL, P = 0.017 for bFGF). Multivariate logistic regression showed that young age and increased plasma levels of VEGF and bFGF were the most significant predictors for the presence of spider angiomas in cirrhotic patients (odds ratio [OR] = 6.64, 95% confidence interval [CI] = 2.02-21.79, P = 0.002; OR = 4.35, 95%CI = 1.35-14.01, P = 0.014; OR = 5.66, 95%CI = 1.72-18.63, P = 0.004, respectively).

CONCLUSION: Plasma VEGF and bFGF are elevated in patients with liver cirrhosis. Age as well as plasma levels of VEGF and bFGF are significant predictors for spider angiomas in cirrhotic patients.

Experimental study on therapeutic effect of in vivo expression of Cell I-Hep II recombinant polypeptide of fibronectin on murine H22 hepatocellular carcinoma

AIM: To investigate the inhibitory effect of in vivo expression of expressing plasmid pCH510 of recombinant fibronectin polypeptide (CH50) on hepatocellular carcinoma and the improved therapeutic effect of pCH510 in combination with chemotherapeutic agents and Hsp70-H22 hepatocarcinoma antigen peptide on tumor.

METHODS: Mice were inoculated with H22 hepatocarcinoma cells. The chemotactic effect of the expression of plasmid pCH510 on immunocytes was observed after in vivo transfection, tissue slicing and HE staining. Inhibitory effect of transfection with pCH510 on murine tumor originated from different inoculative doses was observed. The inhibitory effect of immediate transfection with pCH510 after chemotherapy on tumor was compared with that of transfection 5 days after chemotherapy. The change of function and amount of mouse peritoneal macrophages and the peripheral blood immunocytes resulted from administration of chemotherapeutic agents were detected. The peptides mixture was prepared from H22 hepatocarcinoma cells. pCH510 + Hsp70-H22 antigen peptides were injected into tumor-bearing mice with or without chemotherapy, to observe the inhibitory effects on tumor.

RESULTS: At the tumor tissue site injected with pCH510, there were a great number of immunocytes which mainly were macrophages, lymphocytes and neutrophils. Transfection of plasmid pCH510 inhibited significantly the murine tumor induced by different inoculative doses. The inhibitory effect was negatively correlated with the inoculative dose. The therapeutic effect was not improved by immediate transfection with pCH510 after chemotherapy, but was significantly improved by transfection with pCH510 5 days after chemotherapy. Chemotherapeutic agent decreased the number of immunocytes and suppressed their activation in vivo. After injection of drug, the amount of immunocytes was the lowest from d 1 to d 3 and returned to normal level on the 10^th day. Transfection with plasmid pCH510 alone could inhibit tumor induced by the inoculation with 10⁴ H22 cells. The tumor originated from the inoculation with 10⁵ H22 cells was inhibited by pCH510 + Hsp70-H22 antigen peptides and that from the inoculation with 10⁶ H22 cells was inhibited by pCH510 + Hsp70-H22 antigen peptides in combination with chemotherapeutic agents.

CONCLUSION: In vivo expression of pCH510 recruits immune cells, inhibits tumor growth, and enhances the efficacy of chemotherapy. But the proper timing of combining chemotherapy with pCH510 must be taken into great account. The synergism of pCH510 and Hsp70-H22 peptides can improve the efficacy, which could be further enhanced if they are used following chemotherapy. Chemotherapeutic agent + pCH510 + Hsp70-H22 peptides is a promising therapeutic approach of combination treatment of tumor.