GAST and gastric cancer: Gastrin has been reported to be abnormally expressed in a variety of tumors, such as pancreatic cancer [3], colorectal cancer [4], lung cancer [5], and gastric cancer [6], and it can promote proliferation and metastasis of tumors [7], alter the immune cell signature in the tumor microenvironment [8], and inhibit cancer cell apoptosis [9, 10].