title: RNAi-mediated silencing of MLL-AF9 reveals leukemia-associated downstream targets and processes.
abstract: BACKGROUND
  The translocation t(9;11)(p22;q23) leading to the leukemogenic fusion gene MLL-AF9 is a frequent translocation in infant acute myeloid leukemia (AML). This study aimed to identify genes and molecular processes downstream of MLL-AF9 (alias MLL-MLLT3) which could assist to develop new targeted therapies for such leukemia with unfavorable prognosis.
  
  
  METHODS
  In the AML cell line THP1 which harbors this t(9;11) translocation, endogenous MLL-AF9 was silenced via siRNA while ensuring specificity of the knockdown and its efficiency on functional protein level.
  
  
  RESULTS
  The differential gene expression profile was validated for leukemia-association by gene set enrichment analysis of published gene sets from patient studies and MLL-AF9 overexpression studies and revealed 425 differentially expressed genes. Gene ontology analysis was consistent with a more differentiated state of MLL-AF9 depleted cells, with involvement of a wide range of downstream transcriptional regulators and with defined functional processes such as ribosomal biogenesis, chaperone binding, calcium homeostasis and estrogen response. We prioritized 41 gene products as candidate targets including several novel and potentially druggable effectors of MLL-AF9 (AHR, ATP2B2, DRD5, HIPK2, PARP8, ROR2 and TAS1R3). Applying the antagonist SCH39166 against the dopamine receptor DRD5 resulted in reduced leukemic cell characteristics of THP1 cells.
  
  
  CONCLUSIONS
  Besides potential new therapeutic targets, the described transcription profile shaped by MLL-AF9 provides an information source into the molecular processes altered in MLL aberrant leukemia.
authors: Children's Research Center, Division of Pediatric Hematology and Oncology, Dr, von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, Lindwurmstrasse 2a, München 80337, Germany. katrin.fleischmann@med.uni-muenchen.de.
authors: Katrin K
authors: KK
authors: Fleischmann
authors: Philipp
authors: P
authors: Pagel
authors: Irene
authors: I
authors: Schmid
authors: Adelbert A
authors: AA
authors: Roscher
mesh_terms: D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D006801:Humans; D015151:Immunoblotting; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome; D014162:Transfection
chemical_list: C474558:MLL-AF9 fusion protein, human; D015514:Oncogene Proteins, Fusion; D034741:RNA, Small Interfering; D051788:Myeloid-Lymphoid Leukemia Protein