Additionally, it is well-documented that ERK can exert the tumor-promoting role in a lot of malignancies through upregulation of PD-L1 expression, such as ESCC, breast cancer, colon cancer, intrahepatic cholangiocarcinoma, non-small cell lung carcinoma and gastric cancer [29-34]. This evidence concerns the gene CD274 and esophageal squamous cell carcinoma.