Expression and role of thrombospondin-1 in colorectal cancer.

Thrombospondin-1 (TSP1) inhibits angiogenesis and activates transforming growth factor beta-1 (TGF beta-1). The expression and role of TSP1 remain controversial. On 132 colorectal cancer specimens, we performed immunohistochemical staining of TSP1, TGF beta-1, latency-associated peptide (LAP) and CD34, besides performing in situ hybridization (ISH) of TSP1. TSP1 was mainly localised in fibroblasts of the tumor stroma on ISH. The result revealed that 73 cases (55.3%) were evaluated as high-TSP1 while 84 cases (63.6%) were evaluated as high-TGF beta-1. The expression of TSP1 correlated significantly with vessel counts (p = 0.016) and TGF beta-1 expression (p = 0.043). Cox proportional hazard analysis showed that TSP1 expression was significantly correlated with independent prognostic factors. The present study furnishes evidence indicating that TSP1 is expressed in tumor stroma, inhibits tumor angiogenesis and suppresses tumor growth by activating TGF beta-1.