Promoter-specific effects of metformin on aromatase transcript expression

► Metformin inhibits the PGE2-mediated expression of aromatase (PI.3/PII). ► Metformin has no effect on the DEX/TNFα-mediated expression of aromatase (PI.4). ► Metformin may be a breast-specific inhibitor of aromatase in postmenopausal breast cancer.