Non-Functional ("haploinsufficient"), but Not Dominant Negative Clonal IKZF1 Deletions Confer an Adverse Prognosis in Adult BCR-ABL -Negative Acute Lymphoblastic Leukemia

Background: IKAROS (IKZF1) is a key transcription factor for B-cell development. The IKZF1 protein exerts its functions as a dimer (homodimer or heterodimer with other IKAROS family members). Various IKZF1 intragenic deletions have been identified as recurrent aberrations in acute lymphoblastic leukemia: those resulting in the loss of transcription of one allele or at least loss of the dimerization domain ("haploinsufficient", "non-functional") and those involving only the DNA-binding domain but retaining the dimerization domain of the transcription factor, leading to so-called "dominant negative" isoforms.