Thrombospondin-1 expression in oral squamous cell carcinomas: correlations with tumor vascularity, clinicopathological features and survival.

Thrombospondin-1 (TSP-1) is a 450 kd glycoprotein synthesized and incorporated into the extracellular matrix by numerous cell types and reported to suppress tumor growth and progression by its inhibition of angiogenesis. In order to clarify the biological role of TSP-1 and determine its clinicopathological significance in oral squamous cell carcinomas (SCCs), we identified TSP-1 protein expression in 54 oral SCCs by immunohistochemistry and correlated it with microvessel density (MVD), clinicopathological features and patient's survival. Thirty-two out of 54 carcinomas (59%) were identified as having a low level of TSP-1 expression (TSP-1-L), and 22/54 (41%) carcinomas identified as having a high level of TSP-1 expression (TSP-1-H). The MVD counts (mean+/-S.D.=9.0+/-4.9) in TSP-1-H tumors was significantly lower than that (mean+/-S.D.=12.7+/-4.4) in TSP-1-H tumors (P=0.0065). The level of TSP-1 expression was not correlated with T category and histologic grade, but inversely correlated with the pattern of tumor invasion (P=0.0136) and with lymph nodal status (P=0.0119). Furthermore, Kaplan-Meier analysis showed that the 5-year survival rate of TSP-1-H group was significantly higher than that of TSP-l-L group. Our results suggested that TSP-1 expression exerts an inhibitory effect on tumor vascularity, and that it has value in assessment of aggressiveness and prognosis of oral SCCs.