EGFR and esophageal squamous cell carcinoma: Since previous studies documented that EGF-induced EGFR activation could decrease IGFBP-3 protein levels in ESCC TE-2 and TE-7 cell lines [27] and IGFBP-3 has been suggested as a key marker of radiosensitivity that enhances the susceptibility of ESCC to RT [25], in our study, we further examined the levels of IGFBP-3 in EGF-treated KYSE30 and TE-1 cell lines before and after Nimotuzumab administration.