Expression of thymidine kinase mediated by a novel non-viral delivery system under the control of vascular endothelial growth factor receptor 2 promoter selectively kills human umbilical vein endothelial cells

AIM: To investigate the killing efficiency of a recombinant plasmid containing a thymidine kinase (TK) domain insert driven by the vascular endothelial growth factor receptor 2 (VEGFR2) promoter (KDR) on vascular endothelial cells.METHODS: The KDR-TK fragment was extracted from pBluescript Ⅱ KDR-TK plasmid by enzymatic digestion with Xho I and Sal I. The enhanced green fluorescence protein (EGFP) carrier was extracted from pEGFP by the same procedure. The KDR-TK was inserted into the pEGFP carrier to construct pEGFP-KDR-TK. Using ultrasound irradiation and microbubble, pEGFP-KDR-TK was transferred into human umbilical vein endothelial cells (HUVECs). The transient infection rate was estimated by green fluorescent protein (GFP) expression. Transfected HUVECs, non-transfected HUVECs, and HepG2 cells were cultured in the presence of different concentrations of ganciclovir (GCV), and the killing efficacy of HSV-TK/GCV was analyzed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT) assay. RESULTS: The recombinant pEGFP-KDR-TK was successfully constructed by inserting the KDR-TK fragment into the pEGFP carrier. Transfected HUVECs showed cytoplasmic green fluorescence, and the transient transfection rate was about 20.3%. Pools of G418-resistant cells exhibited a higher sensitivity to theprodrug/GCV compared to non-transfected HUVECs or non-transfected HepG2 cells, respectively. CONCLUSION: KDR promoter and the suicide gene/prodrug system mediated by diagnostic ultrasound combined with microbubble can significantly kill HUVECs. Such therapy may present a novel and attractive approach to target gene therapy on tumor vessels.

Molecular Modeling Studies of Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitors Combining Molecular Docking and 3D-QSAR Methods

The vascular endothelial growth factor （VEGF） and its receptor tyrosine kinases VEGFR-2 or kinase insertdomain receptor （KDR） have emerged as attractive targets for the design of novel anticancer agents. In the present work, molecular docking method combined with three dimensional quantitative structure-activity relationships （comparative molecular field analysis （CoMFA） and comparative molecular similarity indice analysis （CoMSIA）） to analyze the possible interactions between KDR and those derivatives which acted as selective inhibitors. The CoMFA and CoMSIA models gave a cross-validated coefficient Q2 of 0.713 and 0.549, non-cross-validated R2 values of 0.974 and 0.878, and predicted R2 values of 0.966 and 0.823, respectively. The 3D contour maps generated by the CoMFA and CoMSIA models were used to identify the key structural requirements responsible for the biological activity. The information obtained from 3D-QSAR and docking studies were very helpful to design novel selective inhibitors of KDR with desired activity and good chemical property.

Intravitreal injection of resveratrol inhibits laser-induced murine choroidal neovascularization

AIM:To determine the effects of intravitreal resveratrol(RSV)on murine laser-induced choroidal neovascularization(CNV).METHODS:The toxicity of RSV to choroidal endothelial cell(CEC)was measured using thiazolyl blue tetrazolium bromide(M一)assay.Effects of RSV on choroidal endothelial cell(CEC)migration were evaluated with a modified Boyden chamber assay,while tube formation was evaluated in a 2-D gel assay.CNV was induced by laser photocoagulation in mice.The effects of intravitreal injection of RSV on CNV development were evaluated by fluorescein angiography(FA),confocal analysis of isolectin B4 labeled choroidal flat mounts,and histologic examination of CNV membranes.Immunostaining was used to analyze the expression and phosphorylation of vascular endothelial growth factor receptor 2(VEGFR2).RESULTS:No significant cell toxicity was observed in CEC if the concentration of RSV was less than 200 pmol/L(P>0.05).RSV inhibited vascular endothelial growth factor(VEGF)-induced CEC migration(P<0.05)and tube formation(P<0.05)invitro.Furthermore,intravitrealinjectionof RSV significantly inhibited laser induced CNV formation in mice.The FA leakage,CNV volume and CNV area analysis revealed that there were 41%,45%,and 58%reduction in RSV-treated eyes(1.691±0.1032,178163±78623μm^3 and 6508±619.0μm^2,respectively)compared with those in control(2.724±0.08447,379676±98382μm3and16576±2646μm^2,respectively;P<0.05).Phospho-VEGFR2expression was much weaker in the sections of CNV lesions in RSV injected mice compared with that in control(P<0.05).CONCLUSION:Intravitreal injection of RSV exerts an inhibitory effect on CNV,which may through suppressing endothelial cell migration,tube formation and VEGFR2 phosphorylation.

Targeted agents for second-line treatment of advanced hepatocellular carcinoma

Over the past ten years,sorafenib,a multikinase inhibitor,has been the standard of care for patients with unresectable hepatocellular carcinoma(HCC)and wellpreserved liver function.Recently,lenvatinib,a different multikinase inhibitor,was shown to be non-inferior to sorafenib,in terms of survival,while all other agents previously tested failed to prove non-inferiority(or superiority)when compared to sorafenib.Similarly,in the second-line setting,most investigational drugs failed to provide better survival outcomes than placebo.However,in the last 2 years three positive phase III trials have been published in this setting.The RESORCE trial,a phase III study evaluating regorafenib in HCC patients who experienced disease progression after first-line treatment with sorafenib,showed better outcomes with regorafenib compared to placebo.More recently,the phase III CELESTIAL trial demonstrated the superiority of cabozantinib,a multikinase inhibitor targeting vascular endothelial growth factor receptor,MET,and AXL,vs placebo in the second-and third-line setting in patients progressing on or intolerant to sorafenib.The survival benefits of a sustained anti-angiogenic inhibition were demonstrated also with ramucirumab in the phase III REACH-2 trial in patients previously treated with sorafenib and who had high baseline alpha-fetoprotein levels.Overall,the adverse events reported in these trials were in line with the known safety profiles of the tested agents.After nearly a decade of a certain degree of stagnation,we are now witnessing a period of novel therapeutic advances with multikinase inhibitors and monoclonal antibodies that will likely change the treatment scenario of HCC.

Apatinib as an alternative therapy for advanced hepatocellular carcinoma

Angiogenesis plays an important role in the occurrence and development of tumors.Registered tyrosine kinase inhibitors targeting vascular endothelial growth factor reduce angiogenesis.Apatinib,a tyrosine kinase inhibitor,can specifically inhibit vascular endothelial growth factor receptor 2,showing encouraging anti-tumor effects in a variety of tumors including advanced hepatocellular carcinoma(HCC).This article intends to review the clinical research and application prospects of apatinib in the field of HCC.

Effect of VEGF on Neural Differentiation of Human Embryonic Stem Cells in vitro

The effects of vascular endothelial growth factor （VEGF） on neural differentiation of human embryonic stem cells （hESCs） in vitro and the possible mechanism were observed. The hESCs lines, TJMU1 and TJMU2, were established and stored by our laboratory, hESCs differentiated into neuronal cells through embryonic body formation. In this induction process, hESCs were divided into three groups： group A, routine induction; group B, routine induction＋10 ng/mL VEGF; group C, routine in- duction＋10 ng/mL VEGF＋10 ng/mL VEGFR2/Fc. OCT4, Nestin and GFAP in each group were de- tected by RT-PCR, and the cells expressing Nestin and GFAP were counted by immunofluorescence. The percentage of Nestin positive cells in group B was significantly higher than in groups A and C, while the percentage of GFAP positive cells in group B was significantly lower than in groups A and C （P〈0.01）. There was no significant difference between groups A and C （P〉0.05）. It was concluded that VEGF, via VEGFR2, stimulated the neural differentiation of hESCs in vitro.

Expression of VEGFR2 and NRP-1 in non-small cell lung cancer and their clinical significance

Objective： Vascular-targeted therapy is gradually becoming more appealing for patients with lung cancer. It is unclear whether vascular endothelial growth factor receptor 2（VEGFR2） and neuropilin-1（NRP-1） can be biomarkers for clinical treatment. We aimed to investigate the expression levels of VEGFR2 and NRP-1 in human non-small cell lung cancer（NSCLC） and their clinical significance by observing patient prognosis. Methods： VEGFR2 and NRP-1 were assessed by immunohistochemistry（IHC） in 40 patients with NSCLC and in 10 patients with benign lesions of lung; kinase insert domain receptor（KDR） and NRP-1 copy number gain（CNG） was assessed by fluorescence in situ hybridization（FISH）. The distributions of overall survival（OS） and progression-free survival（PFS） were estimated using the Kaplan-Meier method and compared between groups by log-rank test.Results： Rates of positive immunostaining for VEGFR2 and NRP-1 were 58% and 55%, respectively. KDR and NRP-1 CNG（＋） were detected in 32.5% and 30% of tumors, respectively. Levels of both VEGFR2 and NRP-1 in lung tumors were significantly different than in the control tissue（χ2=11.22, P=0.001; χ2=9.82, P=0.001, respectively）; similar results were obtained using CNGs（χ2=4.39, P=0.036; χ2=3.95, P=0.046, respectively）. Statistically significant correlations were observed with histological grade, clinical TNM stage and the lymph node status（P〈0.05）, but not age, gender or pathology type（P〉0.05）. VEGFR2 showed a strong correlation with NRP-1（Rs=0.68, P=0.00）; similar results were observed with KDR and NRP-1 CNG（Rs=0.32, P=0.04）. Significant differences in OS and PFS were observed between the groups with higher VEGFR2 and NRP-1 and those with lower expression（P〈0.05）. Conclusions： According to these data, VEGFR2 and NRP-1 are highly expressed in NSCLC. We can conclude that they play a key role in NSCLC occurrence, development and metastasis and are associated with patient prognosis（P〈0.05 for OS and PFS）. This information will be beneficial for clinical antiangiogenic treatment in NSCLC.

Discovery of antitumor diterpenoids from Casearia graveolens targeting VEGFR-2 to inhibit angiogenesis

Eight novel clerodane diterpenoids(1-8)were isolated from the twigs of Casearia graveolens.Their structures were elucidated through comprehensive nuclear magnetic resonance(NMR),high-resolution electrospray ionization mass spectrometry(HRESI-MS),and electronic circular dichroism(ECD)analyses.In addition to structural determination,surface plasmon resonance(SPR)assays were conducted to investigate molecular interactions,revealing that compound 8 exhibited high affinity for vascular endothelial growth factor receptor 2(VEGFR2),a key regulator of tumor angiogenesis.Subsequent in vivo experiments demonstrated that compound 8 effectively inhibited angiogenesis and displayed significant antitumor activity by suppressing tumor proliferation and metastasis in zebrafish xenograft models.These findings suggest that compound 8 holds promise as an anticancer lead compound targeting VEGFR-2 to obstruct tumor angiogenesis.