Coordinated Functions of E-Cadherin and Transforming Growth Factor B Receptor II In vitro and In vivo

In epithelial cells, E-cadherin plays a key role in cell-cell adhesion, and loss of E-cadherin is a hallmark of tumor progression fostering cancer cell invasion and metastasis. To examine E-cadherin loss in squamous cell cancers, we used primary human esophageal epithelial cells (keratinocytes) as a platform and retrovirally transduced wild-type and dominantnegative forms of E-cadherin into these cells. We found decreased cell adhesion in the cells expressing dominantnegative E-cadherin, thereby resulting in enhanced migration and invasion. To analyze which molecular pathway(s) may modulate these changes, we conducted microarray analysis and found up-regulation of transforming growth factor B receptor II (TBRII) in the wild-type E-cadherin-overexpressing cells, which was confirmed by real-time PCR and Western blot analyses. To investigate the in vivo relevance of this finding, we analyzed tissue microarrays of paired esophageal squamous cell carcinomas and adjacent normal esophagus, and we could show a coordinated loss of E-cadherin and TBRII in f80% of tumors. To determine if there may be an E-cadherindependent regulation of TBRII, we show the physical interaction of E-cadherin with TBRII and that this is mediated through the extracellular domains of E-cadherin and TBRII, respectively. In addition, TBRI is recruited to this complex. When placed in the context of three-dimensional cell culture, which reflects the physiologic microenvironment, TBRIImediated cell signaling is dependent upon intact E-cadherin function. Our results, which suggest that E-cadherin regulates TBRII function, have important implications for epithelial carcinogenesis characterized through the frequent occurrence of E-cadherin and TBRII loss. (Cancer Res 2006; 66(20): 9878-85)