Blocking ETV6/RUNX1-induced MDM2 overexpression by Nutlin-3 reactivates p53 signaling in childhood leukemia.
ETV6/RUNX1 (E/R) is the most common fusion gene in childhood acute lymphoblastic leukemia. It is responsible for the initiation of leukemia but also indispensable for disease maintenance and propagation, although its function in these latter processes is less clear. We therefore investigated the effects of the perceived p53 pathway alterations in model cell lines and primary leukemias and, in particular, how E/R upregulates MDM2, the predominant negative regulator of p53. We found that E/R transactivates MDM2 in both p53(+/+) and p53(-/-) HCT116 cells by binding to promoter-inherent RUNX1 motifs, which indicates that this activation occurs in a direct and p53-independent manner. Treatment of E/R-positive leukemic cell lines with Nutlin-3, a small molecule that inhibits the MDM2/p53 interaction, arrests their cell cycle and induces apoptosis. These phenomena concur with a p53-induced expression of p21, pro-apoptotic BAX and PUMA, as well as caspase 3 activation and poly ADP-ribose polymerase cleavage. The addition of DNA-damaging and p53-activating chemotherapeutic drugs intensifies apoptosis. Moreover, Nutlin-3 exposure leads to an analogous p53 accumulation and apoptotic surge in E/R-positive primary leukemic cells. Our findings clarify the role of p53 signaling in E/R-positive leukemias and outline the potential basis for its therapeutic exploitation in this setting.
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Kaindl
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Morak
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Portsmouth
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Mecklenbräuker
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Kauer
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Zeginigg
St Anna Kinderspital, Medical University Vienna, Vienna, Austria.
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Attarbaschi
1] St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria [2] St Anna Kinderspital, Medical University Vienna, Vienna, Austria.
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Haas
St Anna Kinderkrebsforschung, Children's Cancer Research Institute, Vienna, Austria.
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Panzer-Grümayer
D017209:Apoptosis / Q000187:drug effects; D002648:Child; D047369:Chromatin Immunoprecipitation; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D050783:Proto-Oncogene Proteins c-ets / Q000235:genetics*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics*; D015398:Signal Transduction; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D000097764:ETS Translocation Variant 6 Protein
D050676:Core Binding Factor Alpha 2 Subunit; D007093:Imidazoles; D010879:Piperazines; D050783:Proto-Oncogene Proteins c-ets; D051736:Proto-Oncogene Proteins c-mdm2; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D000097764:ETS Translocation Variant 6 Protein; C493728:RUNX1 protein, human; C495901:TP53 protein, human; C482205:nutlin 3; C497206:MDM2 protein, human