Gene expression patterns associated with the metastatic phenotype in rodent and human tumors

Using subtractive technology, we have generated metastasis-associated gene expression profiles for rat mammary and pancreatic adenocarcinomas. Several genes whose expression is thought to be related to tumor progression such as c-Met, urokinase-type plasminogen activator receptor, ezrin, HMG-1, oncomodulin, cathepsin, and caveolin were thereby isolated. Half of the metastasis-associated clones showed no significant homology to genes with known function. Notably, several of the metastasis-associated clones were also expressed in metastatic lines but not in nonmetastatic lines of other tumor models. Furthermore, in situ hybridization using selected clones documents the relevance of these results for human cancer because strong expression in tumor cells including metastases was detected in human colorectal cancer samples and, to a lesser extent, in mammary cancer samples. These data support the concept that tumors express a "metastatic program" of genes.