Anterior gradient 2: a novel player in tumor cell biology.

AGR2 has evolutionarily conserved roles in development and tissue regeneration and is linked with several human cancers. The exact functions and regulation of AGR2 are poorly understood, but current data identify AGR2 as a clinically relevant factor that modulates the behavior and response of hormone-dependent cancers (breast, prostate) and hormone-independent cancers (colorectal, pancreatic, esophageal and other common cancers). AGR2 protein expression induces metastasis, acts as a p53 tumor suppressor inhibitor and survival factor, participates directly in neoplastic transformation and is involved in drug resistance. Thus, AGR2 is an important tumor biomarker and negative prognostic factor potentially exploitable in clinical practice.