Expression of thrombospondin-1 inversely correlated with tumor vascularity and hematogenous metastasis in colon cancer.

Solid tumors require neovascularization for growth and metastasis. Angiogenesis depends on the local balance between various molecules that induce and inhibit neovascularization. Thrombospondin-1 (TSP-1) is thought to be an antiangiogenic factor. In this study, we examined the correlation between expression of TSP-1 and tumor vascularity, and determined its prognostic significance in colon cancer. Microvessel density, determined by immunostaining for factor VIII-related antigen, was significantly higher in tumors that were TSP-1-negative. TSP-1 expression was inversely correlated with prognosis. Patients with TSP-1-negative tumors had a significantly worse prognosis than did those with TSP-1-positive tumors. Frequency of hepatic recurrence was significantly higher in patients with tumors that were TSP-1-negative. In conclusion, TSP-1 is an important negative-regulator of tumor angiogenesis, and TSP-1 may be useful for predicting recurrence in patients with colon cancer.