Belonging to the protein disulfide isomerase (PD 1) family, the anterior gradient 2 (AGR2) is an estrogen-responsive developmentally regulated gene.117 First recognised in breast cancer cells as an estrogen receptor target,118 but now also observed as overexpressed in other tumours like ovarian,119 pancreatic,120 and colorectal cancers.121. The gene discussed is ESR1; the disease is breast cancer.