Background: Tumor tissue consists of a variable mixture of tumor and host-cell populations. Recent developments in laser microdissection (LMD) and cDNA microarray analysis have encouraged us to study the differential gene expression profiles among normal cells, primary carcinoma cells, and metastatic carcinoma cells in cases of gastric carcinoma.
Methods: Total RNA was extracted from the cells obtained by means of LMD from the primary carcinoma, the corresponding gastric epithelium, and the lymph node metastasis in 5 cases of primary gastric carcinoma. RNA was amplified by the T7-based amplification system to be applied to a cDNA microarray. Thereafter, the differentially expressed genes among the 3 populations were evaluated.
Results: cDNA samples for microarray studies were successfully obtained from each cell population of 5 cases. The cDNA microarray demonstrated that several interesting genes, such as cell-cycle regulators and growth factors, were overexpressed in the metastatic cells compared with in the primary carcinoma cells. Oncogenes and cell-adhesion molecules were more overexpressed in the primary carcinoma cells than in the normal cells. On the other hand, caspase 8 and cadherin were more suppressed in the primary carcinoma cells than in the normal cells. Interestingly, among the matrix metalloproteinase family, only MMP7 was identified as a differentially overexpressed gene in both the primary carcinoma and the metastatic cells in comparison with the normal cells.
Conclusions: This study demonstrated that the combined use of LMD, T7-based amplification, and a cDNA microarray enabled us to identify genes directly associated with each population of tumor tissue. The method will open up new possibilities for the precise gene analysis of tumor progression and metastasis.