摘要AIM: To investigate the effects of class Ⅰ phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 on the invasiveness and related mechanisms of implanted tumors of SGC7901 human gastric carcinoma cells in nude mice.METHODS: Nude mice were randomly divided into model control groups and LY294002 treatment groups. On days 5, 10 and 15 after treatment,the inhibitory rate of tumor growth, pathological changes in tumor specimens, expression levels of matrix metalloproteinase (MMP)-2, MMP-9, CD34 [representing microvessel density (MVD)] and vascular endothelial growth factor (VEGF), as well as apoptosis indexes in tumor samples were observed.RESULTS: In this study, we showed that treating the tumors with LY294002 could significantly inhibit carcinoma growth by 11.3%, 29.4% and 36.7%, after 5, 10 and 15 d, respectively, compared to the control group. Hematoxylin & eosin staining indicated that the rate of inhibition increased progressively (23.51% ± 3.11%, 43.20% ± 3.27% and 63.28% ± 2.10% at 5, 10 and 15 d, respectively) along with apoptosis.The expression of MMP-2 was also downregulated (from 71.4% ± 1.6% to 47.9% ± 0.7%, 31.9% ± 0.9% and 7.9% ± 0.7%). The same effects were observed in MMP-9 protein expression (from 49.4% ± 1.5% to 36.9% ± 0.4%, 23.5% ± 0.9% and 7.7% ± 0.6%), the mean MVD (from 51.2% ± 3.1% to 41.9% ± 1.5%, 30.9% ± 1.7% and 14.9% ± 0.8%),and the expression of VEGF (from 47.2% ± 3.1% to 25.9% ± 0.5%, 18.6% ± 1.2% and 5.1% ± 0.9%) by immunohistochemical staining.CONCLUSION: The class Ⅰ PI3K inhibitor LY294002 could inhibit the invasiveness of gastric cancer cells by downregulating the expression of MMP-2, MMP-9, and VEGF, and reducing MVD.