NC1 domain of human type VIII collagen (α 1) inhibits bovine aortic endothelial cell proliferation and causes cell apoptosis

Endostatin, a natural angiogenesis inhibitor, had been identified for years. It opened a new approach for cancer therapy. Sequence analysis reveled that endostatin is the NC1 domain (non-triple-helical domain) of collagen XVIII. In this report, the cDNA of NC1 domain of type VIII collagen (α 1) was cloned and expressed as soluble form in Escherichia coli. The recombinant protein was purified with Ni-NTA agarose column and named as vastatin. It inhibited the proliferation of bovine aortic endothelial (BAE) cell stimulated by basic fibroblast growth factor (bFGF) in a dose-dependent manner. The ED₅₀ of vastatin was 0.6 μg/ml, while the ED₅₀ of endostatin was 0.5 μg/ml. Treatment of BAE cell with vastatin caused G₀-G₁ arrest and cell apoptosis. It is interesting that sequence analysis showed that there was only about 12% amino acid sequence homology between vastatin and endostatin. The structure - function relationship of these angiogenesis molecules remains to be elucidated.