Objective    To evaluate the effects of angiostatin on vascular endothelial growth factor expression in human tongue squamous cell carcinoma cells.     Methods    Subcutaneous xenografts of human tongue squamous cell carcinoma (Tca8113) cell line in BALB/c nude mice were employed and eighteen mice were randomly divided into three groups (6 mice each): the PBS group injected with PBS

the AS group injected with 250 ng purified angiostatin

and the AS group injected with 30 μg purified angiostatin. Reagents were injected intraperitoneally twice daily and tumor volume was calculated twice weekly for 21 d

then animals were sacrificed and each tumor specimen was divided into two parts after surgical resection. The first part was submitted to both immunocytochemistry for VEGF

VEGFR1

VEGFR2 and CD34

and TUNEL apoptosis assay. The second part was prepared for  semi-quantitative RT-PCR analysis of VEGF

VEGFR1 and VEGFR2 mRNA abundance.     Results    There was an increase of apoptotic index (AI) (P0.05) in the AS (250 ng) group and in the AS (30 μg) group and there was a decrease of protein and mRNA expression levels of VEGF

VEGFR1 and VEGFR2

tumor volume and MVD (tumor angiogenesis was estimated by using CD34 antibody to determine microvessel density) (P0.05). These changes were more obvious in the the AS (30 μg) group than in the AS (250 ng) group(P0.05).     Conclusion    Angiostatin down-regulates vascular endothelial growth factor expression in human tongue squamous cell carcinoma cells in a dose-dependent manner.