AGR2 and breast cancer: Subsequently, a large number of studies showed that AGR2 was overexpressed in more than half of cases in breast cancer, prostate cancer, pancreatic cancer, esophageal cancer, which had a certain correlation with the development stage and pathological characteristics of the tumor, and might be involved in the process of tumor cell metastasis, survival, invasion and so on, indicating that AGR2 may be a new key gene related to cancer regulation and biomarker.