Scheme of hypothesis.

Cancer cells overexpressing ODC suppress type XVIII collagen (COL XVIII) expression. As endostatin is generated from type XVIII collagen by proteolytic cleavage, ODC-overexpressing cancer cells secrete reduced quantities of endostatin. As endostatin inhibits VEGF-mediated endothelial proliferation, VEGF secreted from cancer cells further facilitates endothelial proliferation, leading to angiogenesis.