Hepatocellular carcinoma (HCC) is regarded as a suitable target for 
antiangiogenic strategies. However, antiangiogenic agents aimed at single 
targets can be neutralized by upregulation of other proangiogenic factors. 
Therefore, combined approaches addressing at least two angiogenic targets should 
be more effective. Employing an appropriate rat hepatoma model, we examined the 
effects of sFlt-1 (soluble vascular endothelial growth factor [VEGF] receptor 1 
as an indirect inhibitor of angiogenesis) and endostatin (a direct inhibitor of 
angiogenesis) in both single-agent as well as combined approaches under in vitro 
and in vivo conditions. Similar to human HCC, rat Morris hepatoma (MH) cells 
secreted high levels of VEGF, but no endogenous sFlt-1. Parental MH or MHES(r) 
cells, stably expressing rat endostatin, were adenovirally transduced either 
with AdsFlt-1 (encoding sFlt-1) or control vector Adnull (containing no 
transgene), followed by subcutaneous inoculation into syngeneic ACI rats. 
Compared with MH/Adnull cells, expressing no antiangiogenic factors at all, 
tumor weights were reduced fourfold in the MHES(r)/Adnull group, 19-fold in the 
MH/AdsFlt-1-group, and 77-fold in the MHES(r)/AdsFlt-1 combination therapy 
group. Analysis of variance did not show a significant interaction between the 
effects of the two factors ES(r) and sFlt-1; their effects multiplied. In 
conclusion, combined expression of sFlt-1 and endostatin effectively suppresses 
HCC growth under in vivo conditions. Supplementary material for this article can 
be found on the HEPATOLOGY website 
(http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).