In cases of APL with t(11;17)(q23q21), there is evidence of resistance to ATRA and ATO both in vivo and in vitro, particularly in those patients who have the reverse rearrangement RARα-PLZF (20), while patients with t(11;17)(q13;q21) have better prognosis (22). This evidence concerns the gene ZBTB16 and acute promyelocytic leukemia.