ESR1 and neoplasm: For gastric cancer, estrogens may protect against the development of this malignancy by acting on estrogen receptors (ERα and ERβ), which have been identified in gastric cancer cells.43 Estrogen inhibits cell growth and increases apoptosis in gastric cancer cells44, 45 and stimulates the expression of trefoil factor proteins, which play a role in mucosal protection and repair and their trefoil factor genes may act as tumor suppressors.41