Cathepsin B is the driving force of esophageal cell invasion in a fibroblast-dependent manner.

Esophageal cancer, which frequently exhibits coordinated loss of E-cadherin (Ecad) and transforming growth factor beta (TGFbeta) receptor II (TbetaRII), has a high mortality rate. In a three-dimensional organotypic culture model system, esophageal keratinocytes expressing dominant-negative mutant versions of both Ecad and TbetaRII (ECdnT) invade into the underlying matrix embedded with fibroblasts. We also find that cathepsin B induction is necessary for fibroblast-mediated invasion. Furthermore, the ECdnT cells in this physiological context activate fibroblasts through the secretion of TGFbeta1, which, in turn, is activated by cathepsin B. These results suggest that the interplay between the epithelial compartment and the surrounding microenvironment is crucial to invasion into the extracellular matrix.