Fibrosis in the peritoneum induced by scirrhous gastric cancer cells may act as "soil" for peritoneal dissemination.

BACKGROUND: Peritoneal metastases are one reason for the poor prognosis of scirrhous gastric cancer. However, the mechanism of peritoneal metastasis remains unclear. We therefore investigated the interaction between gastric cancer cells and peritoneal fibroblasts, in vivo and in vitro.

METHODS: A human scirrhous gastric cancer cell line, OCUM-2MD3, and a human peritoneal fibroblast cell line, NF-2P, were established in our laboratory. We then investigated the effect of OCUM-2MD3 cells on the peritoneum of nude mice and on the proliferation of NF-2P cells, the effect of NF-2P cells on the migratory capability of OCUM-2MD3 cells, and the peritoneal fibrosis on the development of peritoneal metastasis.

RESULTS: The proliferation of peritoneal fibroblasts was recognized in areas with and without cancer cell infiltration. Serum-free conditioned medium from the OCUM-2MD3 cells had induced peritoneal fibrosis in vivo and significantly stimulated the proliferation of NF-2P cells in vitro. The molecular weight (molecular weight ratio 25,000-43,000) of the growth factors produced by the OCUM-2MD3 cells was estimated by gel filtration high performance liquid chromatography. The migratory capability of the OCUM-2MD3 cells was significantly increased by the presence of NF-2P cells. Tumorigenicity in mice with peritoneal fibrosis was greater than in mice with normal peritoneum.

CONCLUSIONS: Peritoneal fibrosis, formed by a factor secreted by scirrhous gastric cancer cells, may be congenial environment ("soil") for peritoneal metastases of scirrhous gastric carcinoma.