title: Gene expression signatures in MLL-rearranged T-lineage and B-precursor acute leukemias: dominance of HOX dysregulation.
abstract: Rearrangements of the MLL locus, located on human chromosome 11q23, are frequent in both infant and therapy-related leukemias. Gene expression analysis of MLL-rearranged B-precursor acute lymphoblastic leukemias (MLL B-ALLs) has identified these cases as a unique subtype of leukemia, characterized by the expression of genes associated with both lymphoid and myeloid hematopoietic lineages. Here we show that MLL fusions also generate a distinct genetic subtype of T-lineage ALL (MLL T-ALL), in which leukemic cells are characterized by an early arrest in thymocyte differentiation, with suggestive evidence of commitment to the gammadelta lineage. Interestingly, multiple genes linked to cell proliferation (eg, PCNA, MYC, CDK2, and POLA) were down-regulated in MLL-fusion samples, relative to those transformed by other T-ALL oncogenes (P <.000 001, Fisher exact test). Overall, MLL T-ALL cases consistently demonstrated increased levels of expression of a subset of major HOX genes--HOXA9, HOXA10, and HOXC6--and the MEIS1 HOX coregulator (P <.008, one-sided Wilcoxon test), a pattern of gene expression that was reiterated in MLL B-ALLs. However, expression of myeloid lineage genes, previously reported in MLL B-ALLs, was not identified in T-lineage cases with this abnormality, suggesting that myeloid gene dysregulation is dispensable in leukemic transformation mediated by MLL fusion proteins. Our findings implicate dysregulation of HOX gene family members as a dominant mechanism of leukemic transformation induced by chimeric MLL oncogenes.
authors.affiliation: Department of Pediatric Oncology, Mayer-630, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA.
authors.forename: Adolfo A
authors.initials: AA
authors.lastname: Ferrando
authors.forename: Scott A
authors.initials: SA
authors.lastname: Armstrong
authors.forename: Donna S
authors.initials: DS
authors.lastname: Neuberg
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Sallan
authors.forename: Lewis B
authors.initials: LB
authors.lastname: Silverman
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Korsmeyer
authors.forename: A Thomas
authors.initials: AT
authors.lastname: Look
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D002648:Child; D004268:DNA-Binding Proteins / Q000235:genetics*; D015973:Gene Expression Regulation, Leukemic; D015321:Gene Rearrangement; D011495:Histone-Lysine N-Methyltransferase; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015458:Leukemia, T-Cell / Q000209:etiology / Q000235:genetics / Q000473:pathology*; D051788:Myeloid-Lymphoid Leukemia Protein; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000209:etiology / Q000235:genetics / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D011519:Proto-Oncogenes; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D004268:DNA-Binding Proteins; C489815:HOXC8 protein, human; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins; C080041:Hoxc6 protein, mouse; C497422:KMT2A protein, human; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; C097899:homeobox protein HOXA9; D051788:Myeloid-Lymphoid Leukemia Protein; C092119:Hoxa10 protein, mouse; D011495:Histone-Lysine N-Methyltransferase; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3