Establishment and characterization of a high metastatic potential in the peritoneum for human gastric cancer by orthotopic tumor cell implantation.

The aim of this study was to establish an orthotopic implantation model with high metastasis of gastric cancer to the peritoneum which is more faithful to clinical metastasis. A human gastric carcinoma cell line, GC9811, was injected as a single-cell suspension into the stomach of nude mice. The cells from some peritoneum metastatic foci were expanded in vitro and subsequently implanted to the stomach wall of nude mice. By repeating the in vivo stepwise selection method for four rounds and cloning culture, we obtained a cell line designated GC9811-P, which developed peritoneal metastasis in 13 of 13 (100%) of mice, compared with only 20% of those implanted with parental GC9811. The metastatic foci in the peritoneum showed essentially the same histological appearance as those induced by parental cells. Tumor cell growth of GC9811-P in vitro was faster than that of GC9811. Motility assays demonstrated higher motility of GC9811-P than of GC9811. The adhesive ability of GC9811-P cells to laminin was lower than that of GC9811 cells, whereas the ability of GC9811-P cells to adhere to fibronectin was significantly higher than that of parental cells. Differences between GC9811-P and their parental GC9811 cells were found in expression levels of various molecules by flow cytometric and western blot. The findings indicated that up-regulation in the expressions of CD155, VEGF, syndecan-1, and syndecan-2 or down-regulation in the expressions of IL-6 and E-cadherin play an important role in the peritoneal metastasis of human gastric carcinoma cells. The high-metastatic cell line appears to be useful for investigating the mechanisms of peritoneal metastasis and preventing peritoneal metastasis of human gastric cancer.