MPO and acute promyelocytic leukemia: Using QPCR, we determined the effect of ATRA and ATO individually or in combination at 72 h and following 96 h post treatment termination, on the mRNA levels of several genes involved in APL processes such as leukemic differentiation (TGM2, RARβ), granulocyte function (MPO, PRTN3) and other ATRA-regulated targets (e.g., CCL2) in comparison to single agent treatment15,44.