MICRO-ENCAPSULATION OF MDCK-RAS-E CELLS PREVENTS LOSS OF E-CADHERIN INVASION-SUPPRESSOR FUNCTION IN-VIVO

The invasion-suppressor molecule E-cadherin mediates Ca2+-dependent cell aggregation and prevents invasion. E-cadherin-positive Madin-Darby canine kidney (MDCK) cells that were non-invasive in vitro formed, upon i.p. injection, tumors that were invasive. Differentiated tubular tumor areas showed an intense immuno-signal for E-cadherin at intercellular contacts, whereas undifferentiated structures did not. Cell lines derived from such tumors turned out to be invasive in vitro and showed decreased Ca2+-dependent cell aggregation but no change in E-cadherin immunopositivity. This combination of phenotypes indicated a loss of the E-cadherin invasion-suppressor function. Micro-encapsulation of i.p.-injected cells prevented the loss of the E-cadherin invasion-suppressor function. We concluded that this loss in vivo was dependent upon immediate contacts between tumor cells and host cells of upon host factors that could not cross the capsule membrane. (C) 1994 Wiley-Liss, Inc.