HR and esophageal squamous cell carcinoma: The cytotoxicity of bispecific energized fusion protein Ec-LDP-Hr-AE was carried out on four human esophageal squamous cell carcinoma (ESCC) cell lines expressing different levels of EGFR and HER2 and the EGFR/HER2 negative NIH 3T3 cells by using MTT assays (Fig. 2A).