Transformation of myeloid progenitors by MLL oncoproteins is dependent on Hoxa7 and Hoxa9

PM Ayton, ML Cleary - Genes & development, 2003 - genesdev.cshlp.org
PM Ayton, ML Cleary
Genes & development, 2003genesdev.cshlp.org
Transcriptional deregulation through the production of dominant-acting chimeric
transcription factors derived from chromosomal translocations is a common theme in the
pathogenesis of acute leukemias; however, the essential target genes for acute
leukemogenesis are unknown. We demonstrate here that primary myeloid progenitors
immortalized by various MLL oncoproteins exhibit a characteristic Hoxa gene cluster
expression profile, which reflects that preferentially expressed in the myeloid clonogenic …
Transcriptional deregulation through the production of dominant-acting chimeric transcription factors derived from chromosomal translocations is a common theme in the pathogenesis of acute leukemias; however, the essential target genes for acute leukemogenesis are unknown. We demonstrate here that primary myeloid progenitors immortalized by various MLL oncoproteins exhibit a characteristic Hoxa gene cluster expression profile, which reflects that preferentially expressed in the myeloid clonogenic progenitor fraction of normal bone marrow. Continued maintenance of this MLL-dependent Hoxa gene expression profile is associated with conditional MLL-associated myeloid immortalization. Moreover, Hoxa7 and Hoxa9 were specifically required for efficient in vitro myeloid immortalization by an MLL fusion protein but not other leukemogenic fusion proteins. Finally, in a bone marrow transduction/transplantation model, Hoxa9 is essential for MLL-dependent leukemogenesis in vivo, a primary requirement detected at the earliest stages of disease initiation. Thus, a genetic reliance on Hoxa7 and Hoxa9 in MLL-mediated transformation demonstrates a gain-of-function mechanism for MLL oncoproteins as upstream constitutive activators that promote myeloid transformation via a Hox-dependent mechanism.
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