title: miR-17 deregulates a core RUNX1-miRNA mechanism of CBF acute myeloid leukemia.
abstract: BACKGROUND
  Core Binding Factor acute myeloid leukemia (CBF-AML) with t(8;21) RUNX1-MTG8 or inv(16) CBFB-MYH11 fusion proteins often show upregulation of wild type or mutated KIT receptor. However, also non-CBF-AML frequently displays upregulated KIT expression. In the first part of this study we show that KIT expression can be also upregulated by miR-17, a regulator of RUNX1, the gene encoding a CBF subunit. Interestingly, both CBF leukemia fusion proteins and miR-17, which targets RUNX1-3'UTR, negatively affect a common core RUNX1-miRNA mechanism that forces myeloid cells into an undifferentiated, KIT-induced, proliferating state. In the second part of this study we took advantage of the conservation of the core RUNX1-miRNA mechanism in mouse and human, to mechanistically demonstrate in a mouse myeloid cell model that increased KIT-induced proliferation is per se a mechanism sufficient to delay myeloid differentiation.
  
  
  METHODS
  Human (U937) or mouse (32D) myeloid clonal lines were used, respectively, to test: 1) the effect of RUNX1-MTG8 and CBFB-MYH11 fusion proteins, or upregulation of miR-17, on KIT-induced proliferation and myeloid differentiation, and 2) the effect of upregulation of KIT-induced proliferation per se on myeloid cell differentiation.
  
  
  RESULTS
  In the first part of this study we found that stable miR-17 upregulation affects, like the CBF-AML fusion proteins (RUNX1-MTG8 or CBFB-MYH11), a core RUNX1-miRNA mechanism leading to KIT-induced proliferation of differentiation-arrested U937 myeloid cells. In the second part of the study we harnessed the conservation of this core mechanism in human and mouse to demonstrate that the extent of KIT upregulation in 32D mouse myeloid cells with wild type RUNX1 can per se delay G-CSF-induced differentiation. The integrated information gathered from the two myeloid cell models shows that RUNX1 regulates myeloid differentiation not only by direct transcriptional regulation of coding and non-coding myeloid differentiation functions (e.g. miR-223), but also by modulating KIT-induced proliferation via non-coding miRNAs (e.g. miR-221).
  
  
  CONCLUSIONS
  The novelty of this study is dual. On the one hand, miRNAs (e.g. miR-17) can mimic the effects of CBF-AML fusion proteins by affecting a core RUNX1-miRNA mechanism of KIT-induced proliferation of undifferentiated myeloid cells. On the other hand, the extent of KIT-induced proliferation itself can modulate myeloid differentiation of cells with wild type RUNX1 function.
authors.forename: John
authors.initials: J
authors.lastname: Fischer
authors.forename: Stefano
authors.initials: S
authors.lastname: Rossetti
authors.forename: Arani
authors.initials: A
authors.lastname: Datta
authors.forename: Kevin
authors.initials: K
authors.lastname: Eng
authors.forename: Alessandro
authors.initials: A
authors.lastname: Beghini
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Sacchi
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D023081:CCAAT-Binding Factor / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D007446:Chromosome Inversion; D002885:Chromosomes, Human, Pair 16; D002891:Chromosomes, Human, Pair 21; D002898:Chromosomes, Human, Pair 8; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics*; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000473:pathology; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D008954:Models, Biological; D022423:Myeloid Cells / Q000378:metabolism / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D014178:Translocation, Genetic
chemical_list: D020413:3' Untranslated Regions; D023081:CCAAT-Binding Factor; D050676:Core Binding Factor Alpha 2 Subunit; C524941:MIRN17 microRNA, human; D035683:MicroRNAs; D015514:Oncogene Proteins, Fusion; D019009:Proto-Oncogene Proteins c-kit