Objective       To investigate the underlying mechanism of sphingosine kinase 1 (SphK1) in promoting metastasis and invasion in gastric cancer cells.       Methods       Transfection

RNA interference and recombinant plasmid encoding SphK1 (pWPXL-SphK1) were applied to change the expression of the target protein in gastric cancer cell line SGC-7901.Transwell assay was adopted to detect the metastasis and invasion ability of different types of SGC-7901 cells. The content of sphingosine 1-phosphate (S1P) in the supernatant was measured by ELISA. The mRNA expression of S1P receptors

EDG1 and EDG2

were studied by qRT-PCR. While the protein expression of SphK1

EDG1 and EDG2

was measured by Western blotting.       Results      SphK1 over-expression in SGC7901 cells enhanced the metastasis and invasion in the cells

while

SphK1 specific siRNA transfection reduced both the metastasis and invasion

without significant difference when compared with original SGC-7901 cells. Furthermore

overexpression of SphK1 also improve the expression of S1P

and exogenous S1P improved the migration and invasion in gastric cancer cells through EDG1 receptors.       Conclusion       SphK1/S1P/EDG1 plays important roles in the metastasis in gastric cancer

and might provide new target for the diagnosis and therapy of the disease.