Overexpression of Pu.1 was reported in a rare case of adult Philadelphia chromosome-positive bilineage leukemia (myeloid and T-cell), in which TCR rearrangement was detected in both the myeloid and T-cell compartments of the disease, suggesting that the AML population emerged from T-ALL cells, potentially due to Pu.1 expression (61). This evidence concerns the gene SPI1 and acute lymphoblastic leukemia.