Coordinated functions of E-cadherin and transforming growth factor β 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 dominant-negative forms of E-cadherin into these cells. We found decreased cell adhesion in the cells expressing dominant-negative 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 beta receptor II (T beta RII) 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 T beta RII in similar to 80% of tumors. To determine if there may be an E-cadherin-dependent regulation of T beta RII, we show the physical interaction of E-cadherin with T beta RII and that this is mediated through the extracellular domains of E-cadherin and T beta RII, respectively. In addition, T beta RI is recruited to this complex. When placed in the context of three-dimensional cell culture, which reflects the physiologic microenvironment, T beta RII-mediated cell signaling is dependent upon intact E-cadherin function. Our results, which suggest that E-cadherin regulates T beta RII function, have important implications for epithelial carcinogenesis characterized through the frequent occurrence of E-cadherin and T beta RII loss.