ERBB2 and gastric cancer: To evaluate the role of ER stress in trastuzumab response in clinic, we assessed a total of 21 tissue samples derived from HER2-positive GC patients treated with trastuzumab, including eight cases evaluated as progressive disease (PD) and 13 as partial response (PR) or stable disease (SD) according to response evaluation criteria in solid tumours version 1.1 (RECIST 1.1).