AGR2 and head and neck squamous cell carcinoma: AGR2 was previously shown to regulate the proliferation of stem cells and progenitors and their differentiation into multiple cell lineages in mouse stomach 30 and to be important for the self-renewal ability of CSC in head and neck squamous cell carcinoma.31 Here, we revealed that AGR2 is also overexpressed at the protein level in pancreatic CSC compared with non-stem cancer cells.