Moreover, HIF-1α inhibition also synergized with ATRA in promoting leukemia de-bulking (Fig 4I), therefore suggesting that a strong inhibition of HIF-1α may cooperate with ATRA not only to blunt the leukemia-initiating capacity of APL cells, but also their in vivo survival and/or differentiation. This evidence concerns the gene HIF1A and acute promyelocytic leukemia.