title: NOTICE OF RETRACTION: 'MicroRNA 21: response to hormonal therapies and regulatory function in leiomyoma, transformed leiomyoma and leiomyosarcoma cells' by Qun Pan, Xiaoping Luo and Nasser Chegini, Molecular Human Reproduction (MHR) 16: 215-227 (2010). doi:10.1093/molehr/gap093.