Background: Orchestration of two major classes of angiogenic factors—namely, vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang-2)—has been shown to play a pivotal role in tumour angiogenesis, including hepatocellular carcinoma (HCC). However, few studies have focused on the direct interaction of these factors on in vivo tumour development and angiogenesis.
Aim: To examine the interaction between both factors in murine HCC.
Methods: We examined the combination effect of VEGF and Ang-2 overexpression by means of a combination of a retroviral tetracycline (tet) regulated gene manipulating system in vivo, by providing tet in the drinking water, and a conventional plasmid gene expression system.
Results: Neither Ang-2 nor VEGF overexpression induced proliferation of HCC cells in vitro. In vivo, although overexpression of Ang-2 did not increase tumour development, simultaneous expression of Ang-2 and VEGF synergistically augmented tumour growth and angiogenesis in murine HCC. Ang-2 plus VEGF induced tumour development was markedly attenuated by treatment with neutralising monoclonal antibodies against VEGF receptors. Ang-2 plus VEGF overexpression significantly increased the activities of matrix metalloproteinase (MMP)-2 and MMP-9 in the tumour. Suppression of intratumoral VEGF almost completely abolished this augmentation of MMPs.
Conclusions: These results suggest that Ang-2 synergistically augments VEGF mediated HCC development and angiogenesis. This proangiogenic activity was exerted only in the presence of VEGF, at least partly mediated via induction of MMP-2 and MMP-9 in the tumour.
- α-SMA, α smooth muscle actin
- Ang-1, Ang-2, angiopoietin 1 and 2, respectively
- APMA, p-aminophenylmercuric acetate
- bFGF, basic fibroblast growth factor
- BNL-HCC, BNL 1.7R1 hepatocellular carcinoma
- EC, endothelial cell
- ECM, extracellular matrix
- ELISA, enzyme linked immunosorbent assay
- HCC, hepatocellular carcinoma
- tet, tetracycline
- mAb, monoclonal antibody
- MMP, matrix metalloproteinase
- MVD, microvessel density
- PCR, polymerase chain reaction
- VEGF, vascular endothelial growth factor
- VEGFR-1, fms-like tyrosine kinase (flt-1)
- VEGFR-2, kinase-insert domain containing receptor/fetal liver kinase-1 (KDR/Flk-1)
- vascular endothelial growth factor
- hepatocellular carcinoma
- tumour growth
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.