Metastasis of Entamoeba histolytica compared to colon cancer: one more step in invasion.

The multistep invasion process of metastasis is a well-conserved mechanism of normal symbiosis and pathogenic parasitosis. To illustrate this statement, we have compared cellular and molecular aspects of metastasis from colon cancer and enteric amebiasis caused by Entamoeba histolytica. Both types of pathogenic cell, cancer cells and amebic trophozoites, follow the same metastatic route for the liver and other organs. Both establish invasion microecosystems implicating similar kinds of host cells and molecules belonging to closely related families. We have recently found indications that molecules released by trophozoites immediately after adhesion to epithelial monolayers bind to elements of the epithelial intercellular junctions. This phenomenon may lead to the functional disturbance of these junctions. Down-modulation of cell-cell adhesion molecules promotes invasion of colon cancer and other cancer cells. It is our opinion that comparative studies of apparently unrelated systems may reveal cellular and molecular mechanisms of invasion and metastasis that are of general biological importance.