To better characterize the deregulation of the TGFβ pathway in APL and to determine its potential as a therapeutic target, we took advantage of the human chorionic gonadotrophin (hCG)-PML/RARα transgenic model and analyzed the effects of halofuginone (HF; dl-trans-7-bromo-6-chloro-3-[3-(3-hydroxy-2piperidyl)acetonyl]-4(3H)-quinazolinone hydrobromide), which is a low-molecular-weight alkaloid that has been shown to modulate TGFβ signaling. Here, RARA is linked to acute promyelocytic leukemia.