Identification of a chromosomal breakpoint and detection of a novel form of an MLL-AF17 fusion transcript in acute monocytic leukemia with t(11;17)(q23;q21).

More than 40 genes have been reported as translocation partners of the mixed lineage leukemia gene (MLL) in hematologic malignancies. AF17 was identified earlier than most other MLL translocation partners. On the other hand, there is only 1 report of an MLL-AF17 fusion transcript in acute myeloid leukemia (AML). Here we describe a 40-year-old man with a diagnosis of AML involving t(11;17)(q23;q21). We identified a chromosomal breakpoint for t(11;17)(q23;q21) at MLL intron 6 and AF17 intron 8. Although the previously reported form of the MLL-AF17 fusion transcript was not detected by reverse transcriptase-polymerase chain reaction (PCR) analysis, a novel form of an MLL-AF17 fusion transcript joining MLL exon 6 to AF17 exon 9 was detected by complementary DNA panhandle PCR. The fact that 2 forms of MLL-AF17 retain the leucine zipper domain of AF17 suggests that the dimerization domain of AF17 is critical for leukemogenesis by the MLL-AF17 fusion gene.