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Angiogenesis is crucial for the growth and metastasis of solid tumors with sizes larger than a few cubic millimeter Canstatin, the non-collagenous 1 (NC1) domain of α2 chain of type IV collagen, was previously shown to inhibit proliferation of endothelial cells in vitro and suppress in vivo tumor growth. Our previous studies showed that canstatin-N, the N-terminal 1–89 amino acid fragment of canstatin, inhibited the neovascularization in vivo, potently induced apoptosis of endothelial cells in vitro, and suppressed in vivo tumor growth in BALB/c mice. In the present study, we demonstrated that canstatin-C, the C-terminal 157–227 amino acid fragment of canstatin, also specifically inhibited in vitro the proliferation of human umbilical vein endothelial cells and induced apoptosis, but the apoptosis-inducing activity, while close to that of the full-length canstatin, was much lower than that of canstatin-N. Canstatin-C also suppressed in vivo tumor growth in BALB/c mice at a dosage of 10 mg/kg/day. These results suggest that canstatin-C is an anti-angiogenic domain of canstatin mainly associated with the specific inhibition of proliferation of endothelial cells, whereas canstatin-N with the potential apoptosis-inducing activity on endothelial cells. [Copyright &y& Elsevier]

Type IV collagen is one of the components of vascular basement involved in regulation of angiogenesis. Canstatin, the non-collagenous 1 (NC1) domain of α2 chain of type IV collagen, was identified as an inhibitor of angiogenesis and tumor growth by Kamphaus et al. Our previous studies showed that canstatin-N, the N-terminal 1–89 amino acid fragment of canstatin, inhibited the neovascularization in a dose-dependent manner as tested by CAM assay. In the present study, we demonstrate that canstatin-N produced in Escherichia coli specifically inhibited in vitro the proliferation of human umbilical vein endothelial cells (ECV304) and significantly induced apoptosis. The apoptosis-inducing activity of canstatin-N was much stronger than that of canstatin, indicating that the apoptosis-inducing activity of canstatin is likely located within its N-terminal 1–89 amino acid fragment. Canstatin-N also suppressed in vivo growth of B16 murine melanoma in BALB/c mice at a dosage of 10 mg/kg/day. These results suggest that canstatin-N is a useful candidate molecule for inhibition of tumor growth. [Copyright &y& Elsevier]