HDAC1 and neoplasm: As core members of class I histone deacetylases (HDACs), HDAC1, 2 and 3 are abundantly expressed in trophoblast cells and involved in an extremely broad spectrum of gene regulation in the placenta.2, 3, 4 Recent work in tumour cells,5, 6, 7 along with our previous findings in the placenta,8 implied that HDAC1/2/3 might play a significant role in placental BCRP regulation.