Objective       To determine the effect of the vagal neurotransmitter

substance P

on the change of the invasive and migrative capacity in human hepatocellular carcinoma and its possible molecular mechanism.       Methods       Real-time RT-PCR and agarose gel electrophoresis were used to detect the expression of neurokinin-1 (NK-1) receptor in hepatocellular carcinoma cell lines HepG2 and SMMC-7721. After the cells were treated by substance P at different concentrations (0

100

250 or 500 nmol/L) for different times (0

24

48

72

96 or 120 h)

CellTiter Blue cell viability assay was used to measure cell proliferation. Then after the cells were treated by 0 and 100 nmol/L substance P for 48 h

transwell chamber assay was used to detect cell invasion and migration

Western blotting to test the proteins (E-cadherin

N-cadherin and Slug) considered as the landmarks of epithelial-to-mesenchymal transition (EMT)

and RT-PCR and Western blotting to measure the expression of NK-1 receptor.       Results       NK-1 receptor was expressed in both HepG2 and SMMC-7721 cells. Treatment of different concentrations of substance P (0

100

250 and 500 nmol/L) for 96 h had no effect on the proliferation of the both kinds of cells (P0.05)

however

when the dose increasing to 250 and 500 nmol/L and the time elapsing to 120 h

the proliferation was inhibited obviously (P0.05). Substance P (100 nmol/L) remarkably enhanced the capacity of invasion and migration in the both kinds of cells (P0.05). Compared with control group

the expression of NK-1 receptor was significantly up-regulated (P0.05)

and that of E-Cadherin decreased

whereas

that of N-Cadherin and Slug increased (P0.05) in the cells after substance P treatment (100 nmol/L

for 48 h).       Conclusion       Substance P interacts with NK-1 receptor and induces its up-regulation

and then improves the process of EMT and enhances the invasive and migrative capacity in the hepatocellular carcinoma cells.