Upregulation of programmed death ligand 1 and epidermal growth factor receptor is associated with poor prognosis in gastric cancer

Gastric cancer is one of the leading causes of cancer-related death worldwide (1). The incidence rate of gastric carcinoma is particularly high in Asian areas, where specific environmental and genetic triggers differ gastric cancer patients from those in Western countries (2). With the widespread application of endoscopic technology, gastric cancer patients are earlier diagnosed than before. Whereas, overall survival has still not been much prolonged and major breakthroughs have yet to be made since the invention of trastuzumab targeting human epidermal growth factor receptor 2 (HER2) for only a small portion of patients with HER2 overexpression (3)