title: Pharmacological activation of the p53 pathway by nutlin-3 exerts anti-tumoral effects in medulloblastomas.
abstract: Medulloblastomas account for 20% of pediatric brain tumors. With an overall survival of 40%-70%, their treatment is still a challenge. The majority of medulloblastomas lack p53 mutations, but even in cancers retaining wild-type p53, the tumor surveillance function of p53 is inhibited by the oncoprotein MDM2. Deregulation of the MDM2/p53 balance leads to malignant transformation. Here, we analyzed MDM2 mRNA and protein expression in primary medulloblastomas and normal cerebellum and assessed the mutational status of p53 and MDM2 expression in 6 medulloblastoma cell lines. MDM2 expression was elevated in medulloblastomas, compared with cerebellum. Four of 6 medulloblastoma cell lines expressed wild-type p53 and high levels of MDM2. The tumor-promoting p53-MDM2 interaction can be inhibited by the small molecule, nutlin-3, restoring p53 function. Targeting the p53-MDM2 axis using nutlin-3 significantly reduced cell viability and induced either cell cycle arrest or apoptosis and expression of the p53 target gene p21 in these 4 cell lines. In contrast, DAOY and UW-228 cells harboring TP53 mutations were almost unaffected by nutlin-3 treatment. MDM2 knockdown in medulloblastoma cells by siRNA mimicked nutlin-3 treatment, whereas expression of dominant negative p53 abrogated nutlin-3 effects. Oral nutlin-3 treatment of mice with established medulloblastoma xenografts inhibited tumor growth and significantly increased survival. Thus, nutlin-3 reduced medulloblastoma cell viability in vitro and in vivo by re-activating p53 function. We suggest that inhibition of the MDM2-p53 interaction with nutlin-3 is a promising therapeutic option for medulloblastomas with functional p53 that should be further evaluated in clinical trials.
authors.affiliation: University Children’s Hospital Essen, Pediatric Oncology, Essen, Germany. annette.kuenkele@uk-essen.de
authors.forename: Annette
authors.initials: A
authors.lastname: Künkele
authors.forename: Katleen
authors.initials: K
authors.lastname: De Preter
authors.forename: Lukas
authors.initials: L
authors.lastname: Heukamp
authors.forename: Theresa
authors.initials: T
authors.lastname: Thor
authors.forename: Kristian W
authors.initials: KW
authors.lastname: Pajtler
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hartmann
authors.forename: Michel
authors.initials: M
authors.lastname: Mittelbronn
authors.forename: Michael A
authors.initials: MA
authors.lastname: Grotzer
authors.forename: Hedwig E
authors.initials: HE
authors.lastname: Deubzer
authors.forename: Frank
authors.initials: F
authors.lastname: Speleman
authors.forename: Alexander
authors.initials: A
authors.lastname: Schramm
authors.forename: Angelika
authors.initials: A
authors.lastname: Eggert
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Schulte
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D016022:Case-Control Studies; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002528:Cerebellar Neoplasms / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D002531:Cerebellum / Q000378:metabolism; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D008527:Medulloblastoma / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D051379:Mice; D008819:Mice, Nude; D009154:Mutation / Q000235:genetics; D010879:Piperazines / Q000494:pharmacology*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D046888:Tissue Array Analysis; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D007093:Imidazoles; D010879:Piperazines; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2