Abstract:Objective:To study the effects of L-NAME on invasion and metastasis of human colorectal carcinoma cell line（LS-174T） and explore its possible mechanism. Methods:The LS-174T cells were co-incubated with L-NAME at various concertrations. Griess techniqe was used to examine the effect of L-NAME on excretion of nitric oxide(NO) of the cells. The effects of L-NAME on invasion and migration of LS-174T were evaluated using Transwell chambers attached with polycarbonate filters and reconstituted basement membrane. Expression of MMP2 mRNA and TIMP2mRNA in LS-174T cells was measured by RT-PCR. Results:(1)L-NAME decreased the excretion of NO of the cells in a dose-dependent manner. (2)The ability of the L-NAME treated LS-174T cells to invade the reconstituted basement membrane increased significantly with the concentration and time, at the concentration of 0.2 mmol/L,0.4 mmol/L, 0.8mmol/L and 1.0mmol/L, respectively,after 72 hour, the inhibition rates were 10.29%,19.62%,34.08% and 42.23%,respetively. （ P<0.05, P<0.01, P<0.01, P<0.01,respectively）. (3)L-NAME can also inhibit LS-174T cells migration ,and the inhibition rates were 20.76%,24.95%,39.43% and 46.85% in L-NAME at 0.2 mmol/L,0.4 mmol/L,0.8mmol/L and 1.0mmol/L, respectively（ P<0.01）. (4)NO concontration was positive related to expression of MMP2mRNA, and negative related to expression of TIMP2mRNA.Conclusions:L-NAME has anti-invasive and anti-metastatic effects on LS-174T cells, and the anti-invasive and anti-metastatic action of L-NAME might be associated with expression of MMP2mRNA,TIMP2mRNA in tumor cells.