2-Phenyl-1H-benzimidazoles 7a–e were synthesized and tested for gene activation on ERα- positive MCF-7 breast cancer cells, stably transfected with the reporter plasmid EREwtcluc (MCF-7-2a cells). None of the compounds showed agonistic properties, but they antagonized dependent on hydroxyl groups at the benzimidazole core (5-or 6-OH) and at the aromatic ring in the 2-position (4-OH) in high concentrations the gene activation ...