After applying adenosine deaminase inhibitor 1 week after lineage switch, 60% of the bone marrow blast cells were strongly MPO positive, according to the transformation and amplitude of leukemia cells insensitive to the original treatment.17 A study of ALL antigen receptor gene rearrangement PCR in 27 patients showed 13 relapses as an obvious new clonal subtype (not detected by conventional testing). Here, MPO is linked to leukemia.