Sensitivity to epidermal growth factor receptor tyrosine kinase inhibitor requires E-cadherin in esophageal cancer and malignant pleural mesothelioma

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) has limited anticancer efficacy in EGFR-positive esophageal cancer (EsC) and malignant mesothelioma (MPM). The underlying molecular mechanism of resistance to EGFR-TKI in these types of cancer remains unclear.We tested sensitivity to EGFR-TKI, expression/activity of common signal transduction pathways and epithelial to mesenchymal transition (EMT) gene signatures in 14 EsC and MPM cultured cell lines in vitro.More than 50% EGFR-positive EsC and MPM cells were resistant to EGFR-TKI, and susceptibility to EGFR-TKI growth-inhibitory effect correlated positively with expression of E-cadherin (epithelial gene marker) and negatively with mesenchymal gene markers. Acquired resistance to EGFR-TKI in intrinsically sensitive cancer cells coincided with spontaneous loss of E-cadherin, while ectopic expression of E-cadherin sensitized resistant cells to EGFR-TKI.E-Cadherin expression appears to be not only a strong biomarker but also a functional requirement and potential therapeutic target for sensitivity to EGFR-TKI.