Differential gene expression profiles of scirrhous gastric cancer cells with high metastatic potential to peritoneum or lymph nodes

Scirrhous gastric cancer is often accompanied by metastasis to the peritoneum and/or lymph nodes, resulting in the highest mortality rate among gastric cancers. Mechanisms involved in gastric cancer metastasis are not fully clarified because metastasis involves multiple steps and requires the accumulation of altered expression of many different genes. Thus, independent analysis of any single gene would be insufficient to understand all of the aspects of gastric cancer metastasis. In this study, we performed global analysis on differential gene expression of a scirrhous gastric cancer cell line (OCUM-2M) and its derivative sublines with high potential for metastasis to the peritoneal cavity (OCUM-2MD3) and lymph nodes (OCUM-2MLN) in a nude mice model. By applying a high-density oligonucleotide array method, expression of approximately 6800 genes was analyzed, and selected genes were confirmed by the Northern blot method. In our observations in OCUM-2MD3 cells, 12 genes were up-regulated, and 20 genes were down-regulated. In OCUM-2MLN cells, five genes were up-regulated, and five genes were down-regulated. The analysis revealed two functional gene clusters with altered expression: (a) down-regulation of a cluster of squamous cell differentiation marker genes such as small proline-rich proteins [SPRRs (SPRR1A, SPRR1B, and SPRR2A], annexin A1, epithelial membrane protein 1, cellular retinoic acid-binding protein 2, and mesothelin in OCUM-2MD3 cells; and (b) up-regulation of a cluster of antigen-presenting genes such as MHC class II (DP, DR, and DM) and invariant chain (II) in OCUM-2MLN cells through up-regulation of CIITA (MHC class II transactivator). We then analyzed six gastric cancer cell lines by Northern blot and observed preferential up-regulation of trefoil factor 1, alpha-1-antitrypsin, and galectin 4 and down-regulation of cytidine deaminase in cells prone to peritoneal dissemination. Genes highly correlated with invasion or peritoneal dissemination of gastric cancer, such as E-cadherin or integrin beta4, were down-regulated in both of the derivative cell lines analyzed in this study. This is the first demonstration of global gene expression analysis of gastric cancer cells with different metastatic potentials, and these results provide a new insight in the study of human gastric cancer metastasis.