Angiopoietin-2 inhibits the growth of tongue carcinoma without affecting expression of vascular endothelial growth factor.

Angiopoietin-2 (Ang-2) has been identified as an important factor in tumour angiogenesis through its action in blocking the stabilizing actions of Ang-2 and leading to new tumour vessel growth in the presence of vascular endothelial growth factor (VEGF). In the authors' previous study, over-expression of Ang-2 in Tca8113 tongue tumour cells inhibited growth. The current study aims to clarify the mechanisms of Ang-2-mediated tumour growth inhibition and its role in the regulation of VEGF expression. These studies used tumours derived from Ang-2-transfected Tca8113 cells injected into nude mice. The results showed that Ang-2-transfected tumours displayed aberrant angiogenic vessels with few associated smooth muscle cells. No detectable differences in VEGF expression were observed between Ang-2-transfected and parental tumours. Tumours produced by the Ang-2 transfection also had a higher apoptosis index and lower tumour cell proliferative index than tumours in the control groups. These observations suggest that enhanced expression of Ang-2 has no effect on VEGF expression and results in tumour vessel regression and inhibition of tumour growth.