Gene Therapeutic Exploration: Retrovirus-Mediated Soluble Vascular Endothelial Growth Factor Receptor-2 (sFLK-1) Inhibits the Tumorigenicity of S180, MCF-7, and B16 Cells In Vivo

Effect of isotretinoin (13-cis-retinoic acid) on levels of soluble VEGF receptors (sVEGFR1, sVEGFR2, sVEGFR3) in patients with acne vulgaris

Background/aim: The effect of isotretinoin on soluble VEGFRs has not been previously investigated. This study evaluate the effects of isotretinoin (13-cis-retinoic acid) on soluble VEGFR1 (sVEGFR1), soluble VEGFR2 (sVEGFR2) and soluble VEGFR3 (sVEGFR3).Methods: The study included 38 patients (28 females, 10 males) receiving systemic isotretinoin treatment and 38 healthy individuals (28 females, 10 males) with similar age and gender characteristics. The blood samples of the patient group at third months and blood samples of the control group were compared in terms of sVEGFR1, sVEGFR2 and sVEGFR3 concentrations.Results: It was significant that sVEGFR1 was low and sVEGFR3 was high in patients receiving isotretinoin (p: .038, p: .021, respectively). There was no significant change in sVEGFR2 levels between the groups (p: .519).Conclusions: We think that the effect of isotretinoin on sVEGFR1, sVEGFR2 and sVEGFR3 may be secondary to its effects on the VEGF family. However, after clarifying the effect of isotretinoin on the VEGF family, we think that it can be used in some tumors and vascular diseases.

Suppression of lymphangiogenesis by soluble vascular endothelial growth factor receptor-2 in a mouse lung cancer model

The vascular endothelial growth factor (VEGF) family has a key role in the formation of blood vessels and lymphatics. Among the members of this family, VEGF-C is one of the most important factors involved in lymphangiogenesis via binding with two receptors (vascular endothelial growth factor receptor-2 and -3: VEGFR-2 and VEGFR-3). Soluble VEGFR-2 (sVEGFR-2) has a role in maintaining the alymphatic state of the cornea associated with binding to VEGF-C, and selectively inhibits lymphangiogenesis but not angiogenesis. In this study, we introduced sVEGFR-2 into lung cancer cells and evaluated the influence on tumor progression and on genes regulating lymphatic formation and metastasis in vivo. A retroviral vector was used to introduce the sVEGFR-2 gene into Lewis lung carcinoma cells (LLC), which were designated as LLC-sVEGFR-2 cells. Proteins secreted into the culture supernatant by these cells were detected by western blotting using specific antibodies. To examine lymphangiogenesis by primary lung cancer in vivo, LLC-sVEGFR-2 cells were subcutaneously injected into C57BL/6 mice. At 14days after injection, immunohistochemistry was performed using an antibody directed against lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), a marker of lymphatics. Expression of mRNA for VEGFR-2, VEGFR-3 and matrix metalloproteinases (MMPs) was also determined by real-time PCR. Furthermore, LLC-sVEGFR-2 cells were directly inoculated into the left lung in C57BL/6 mice and the number of micro-metastases in pulmonary lymph nodes was determined. Introduction of sVEGFR-2 into LLC cells resulted in secretion of sVEGFR-2 protein into the culture supernatant. There were fewer LYVE-1 positive lymphatics after inoculation of LLC-sVEGFR-2 into mice compared with the control group. In addition, VEGFR-2, VEGFR-3, and MMPs gene expression was suppressed in the primary tumors of the LLC-sVEGFR-2 group compared with the control group. Furthermore, there were fewer micro-metastases in the pulmonary lymph nodes of the LLC-sVEGFR-2 group compared with the control group after cells were directly inoculated into the lung. These findings indicate that introduction of sVEGFR-2 suppressed lymphangiogenesis in primary lung cancer and also suppressed lymphogenic metastasis by inhibiting VEGF-C, followed by down-regulation of VEGFR-2, VEGFR-3 and MMPs. Accordingly, sVEGFR-2 might be a promising target for treatment of cancer by regulating lymphangiogenesis and lymphogenic metastasis.

Preparation and antitumor effect of a toxin-linked conjugate targeting vascular endothelial growth factor receptor and urokinase plasminogen activator

The aberrant signaling activation of vascular endothelial growth factor receptor (VEGFR) and urokinase plasminogen activator (uPA) is a common characteristic of many tumors, including lung cancer. Accordingly, VEGFR and uPA have emerged as attractive targets for tumor. KDR (Flk-1/VEGFR-2), a member of the VEGFR family, has been recognized as an important target for antiangiogenesis in tumor. In this study, a recombinant immunotoxin was produced to specifically target KDR-expressing tumor vascular endothelial cells and uPA-expressing tumor cells and mediate antitumor angiogenesis and antitumor effect. Based on its potent inhibitory effect on protein synthesis, Luffin-beta (Lβ) ribosome-inactivating protein was selected as part of a recombinant fusion protein, a single-chain variable fragment against KDR (KDRscFv)-uPA cleavage site (uPAcs)-Lβ-KDEL (named as KPLK). The KDRscFv-uPAcs-Lβ-KDEL (KPLK) contained a single-chain variable fragment (scFv) against KDR, uPAcs, Lβ, and the retention signal for endoplasmic reticulum proteins KDEL (Lys-Asp-Glu-Leu). The KPLK-expressing vector was expressed in Escherichia coli, and the KPLK protein was isolated with nickel affinity chromatography and gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis test demonstrated KPLK was effectively expressed. Result of in vitro cell viability assay on non-small cell lung cancer (NSCLC) H460 cell line (uPA-positive cell) revealed that KPLK significantly inhibited cell proliferation, induced apoptosis, and accumulated cells in S and G2/M phases, but the normal cell line (human submandibular gland cell) was unaffected. These effects were enhanced when uPA was added to digest KPLK to release Lβ. For in vivo assay of KPLK, subcutaneous xenograft tumor model of nude mice were established with H460 cells. Growth of solid tumors was significantly inhibited in animals treated with KPLK up to 21 days, tumor weights were decreased, and the expression of angiogenesis marker CD31 was downregulated; meanwhile, the apoptosis-related protein casspase-3 was upregulated. These results suggested that the recombinant KPLK may have therapeutic applications on tumors, especially uPA-overexpressing ones.

Ad-KDRscFv:sTRAIL displays a synergistic antitumor effect without obvious cytotoxicity to normal tissues

AIM

To investigate the antitumor activities and safety of Ad-KDRscFv, Ad-sTRAIL (114-281) and Ad-KDRscFv:sTRAIL in vivo and in vitro.

METHODS

Recombinant replication-defective adenovirus vectors encoding either the extracellular domain (114-281 aa) of TRAIL, the KDRscFv (single chain antibody (scFv) against human vascular endothelial growth factor (VEGF) receptor KDR) or the fusion gene of KDRscFv:sTRAIL were constructed and transfected into HEK 293 cells for virus packaging. The recombinant virus particles were then infected human tumor cell lines of liver cancer (HepG2), gastric cancer (SGC-7901), colorectal cancer (SW480) and normal human liver cell line (LO2) to investigate the antitumor activities. Nude mice of the subcutaneous tumor models were established with HepG2 cells and were randomly divided into different groups to investigate the therapeutic effect and safety of these adenovirus particles on hepatocellular carcinoma. The expression of foreign proteins and the effect on microvascular number were also evaluated.

RESULTS

All three adenovirus particles could induce apoptosis of cancer cells lines HepG2, SGC-7901 and SW480, but had no obvious lethal effect on LO2 cells. Ad-KDRscFv:sTRAIL showed the strongest tumoricidal effect. After intratumoral injection with these adenovirus particles on nude mice model, all the three adenoviruses could inhibit the tumor growth and angiogenesis, and the expression of foreign proteins (sTRAIL, KDRscFv and KDRscFv:sTRAIL fusion protein) was restricted to liver and tumor tissues. In coincidence with the result in vitro, Ad-KDRscFv:sTRAIL also had the strongest antitumor activity in vivo. No obvious pathological changes were detected in vivo.

CONCLUSIONS

Replication-defective recombinant adenovirus of Ad-KDRscFv, Ad-sTRAIL and Ad-KDRscFv:sTRAIL all had tumoricidal activities and Ad-KDRscFv:sTRAIL showed the strongest effect. All three adenoviruses had no obvious toxicity to normal cells and tissues in vitro and in vivo.

Soluble VEGF receptor-2 is increased in sera of subjects with metabolic syndrome in association with insulin resistance

OBJECTIVE

Metabolic syndrome (MetS) is associated with impaired angiogenesis. Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis through binding to its specific receptor, VEGF receptor-2 (VEGFR-2), whereas the expression of VEGF and VEGFR-2 in the myocardium of insulin-resistant rats is down-regulated. Soluble VEGF receptor-1 (sVEGFR-1) and -2 (sVEGFR-2) have been reported to inhibit angiogenesis both in vitro and in vivo. However, the balance between circulating levels of VEGF and its soluble receptors, which may reflect and/or affect cardiovascular VEGF signaling, in subjects with MetS is unknown.

METHODS AND RESULTS

We carried out a cross-sectional study including 272 consecutive, apparently healthy subjects who were not receiving any drugs. Plasma levels of VEGF and serum levels of its soluble receptors were determined using enzyme-linked immunosorbent assays. VEGF and sVEGFR-1 levels did not differ between subjects with and those without MetS. However, sVEGFR-2 levels were significantly increased in MetS compared with non-MetS subjects. Stepwise regression analysis revealed that HOMA-IR was the strongest independent determinant of the sVEGFR-2 level. Accordingly, the mean sVEGFR-2 levels increased in proportion to both the accumulation of components of MetS and quartile of HOMA-IR. Interestingly, multiple regression analyses revealed that independent determinants of VEGF were the body mass index and blood pressure, whereas, in contrast, those of sVEGFR-2 were HOMA-IR and high-sensitivity C-reactive protein.

CONCLUSIONS

The correlation of sVEGFR-2 with insulin resistance supports the need for further investigations to define the clinical utility and predictive value of serum sVEGFR-2 levels in cardiovascular dysfunction in MetS.

In vivo inhibition of angiogenesis by interleukin-13 gene therapy in a rat model of rheumatoid arthritis

OBJECTIVE

Interleukin-13 (IL-13) is a pleiotropic cytokine that can affect vessel formation, an important component of the rheumatoid arthritis (RA) synovial tissue pannus. The purpose of this study was to use a gene therapy approach to investigate the role of IL-13 in angiogenesis in vivo, using a rat adjuvant-induced arthritis model of RA.

METHODS

Ankle joints of female rats were injected preventatively with an adenovirus vector containing human IL-13 (AxCAIL-13), a control vector with no insert (AxCANI), or phosphate buffered saline (PBS). Joints were harvested at the peak of arthritis, and histologic and biochemical features were evaluated.

RESULTS

AxCAIL-13-treated joint homogenates had lower hemoglobin levels, suggesting reduced joint vascularity, and both endothelial cell migration and tube formation were significantly inhibited (P < 0.05). Similarly, AxCAIL-13 inhibited capillary sprouting in the rat aortic ring assay and vessel growth in the Matrigel plug in vivo assay. IL-13 gene delivery resulted in up-regulation and association of phosphorylated ERK-1/2 and protein kinase Calpha/betaII, suggesting a novel pathway in IL-13-mediated angiostasis. The angiostatic effect of AxCAIL-13 was associated with down-regulation of proangiogenic cytokines (IL-18, cytokine-induced neutrophil chemoattractant 1/CXCL1, lipopolysaccharide-induced CXC chemokine/CXCL5) and up-regulation of the angiogenesis inhibitor endostatin. The expression and activity of matrix metalloproteinases 2 and 9, which participate in angiogenesis, was impaired in response to IL-13 as compared with AxCANI and PBS treatment.

CONCLUSION

Our findings support a role for IL-13 as an in vivo antiangiogenic factor and provide a rationale for its use in RA to control pathologic neovascularization.

mda-7 In combination with bevacizumab treatment produces a synergistic and complete inhibitory effect on lung tumor xenograft

Bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF), has shown antitumor activity by inhibiting tumor angiogenesis in preclinical and clinical studies. However, bevacizumab monotherapy does not induce complete tumor regression. Therefore, additional treatments must be combined with bevacizumab to promote tumor regression. We previously showed that melanoma differentiation associated gene-7 (mda-7) protein exerts potent antitumor and antiangiogenic activity. Thus, in this study, we investigated the therapeutic effects of mda-7 in combination with bevacizumab using lung cancer as a model. In vitro, treatment of human umbilical vein endothelial cells with conditioned medium from Ad-mda7 plus bevacizumab-treated lung tumor cells showed reduced VEGF ligand-receptor binding, and decreased cell survival, resulting in growth arrest and apoptosis. In vivo, treatment of subcutaneous lung tumor xenografts with bevacizumab plus Ad-mda7 resulted in significant tumor growth inhibition and improved survival compared to tumor growth in control mice. Furthermore, tumors in all the Ad-mda7 plus bevacizumab-treated mice completely regressed, and these were tumor free through the study's end. Molecular analysis showed enhanced tumor cell apoptosis and reduced VEGF and CD31 expression in Ad-mda7 plus bevacizumab-treated tumors. Thus, Ad-mda7 and bevacizumab treatment produces a synergistic and complete therapeutic effect against human lung cancer.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.