Autocrine stimulation via coexpression of hepatocyte growth factor (HGF) and its receptor (Met) has been reported in many human sarcomas, but few in carcinomas. In this report, we found that one gastric cancer cell line, SNU-484, among 11 gastric cell lines tested has an autocrine HGF- Met stimulation. RT-PCR, ELISA and scattering assay using MDCK cells revealed that SNU-484 cells secreted a significant amount of active HGF (about 1.25 +/- 0.41 ng/24 h/10(6) cells) into conditioned medium. Resultantly, Met in this cell line was constitutively phosphorylated. Neutralizing antibodies against HGF reduced the tyrosine phosphorylation of Met, resulting in the inhibition of cell proliferation and migration (P <0.005). To the best of our knowledge, this is the first report on autocrine HGF-Met signaling in a gastric cancer cell line. Our observations with SNU-484 cells suggest that HGF is involved in the development and/or progression of some gastric carcinoma through an autocrine mechanism.