title: Combination therapy in a xenograft model of glioblastoma: enhancement of the antitumor activity of temozolomide by an MDM2 antagonist.
abstract: OBJECTIVE Improvement in treatment outcome for patients with glioblastoma multiforme (GBM) requires a multifaceted approach due to dysregulation of numerous signaling pathways. The murine double minute 2 (MDM2) protein may fulfill this requirement because it is involved in the regulation of growth, survival, and invasion. The objective of this study was to investigate the impact of modulating MDM2 function in combination with front-line temozolomide (TMZ) therapy in GBM. METHODS The combination of TMZ with the MDM2 protein-protein interaction inhibitor nutlin3a was evaluated for effects on cell growth, p53 pathway activation, expression of DNA repair proteins, and invasive properties. In vivo efficacy was assessed in xenograft models of human GBM. RESULTS In combination, TMZ/nutlin3a was additive to synergistic in decreasing growth of wild-type p53 GBM cells. Pharmacodynamic studies demonstrated that inhibition of cell growth following exposure to TMZ/nutlin3a correlated with: 1) activation of the p53 pathway, 2) downregulation of DNA repair proteins, 3) persistence of DNA damage, and 4) decreased invasion. Pharmacokinetic studies indicated that nutlin3a was detected in human intracranial tumor xenografts. To assess therapeutic potential, efficacy studies were conducted in a xenograft model of intracranial GBM by using GBM cells derived from a recurrent wild-type p53 GBM that is highly TMZ resistant (GBM10). Three 5-day cycles of TMZ/nutlin3a resulted in a significant increase in the survival of mice with GBM10 intracranial tumors compared with single-agent therapy. CONCLUSIONS Modulation of MDM2/p53-associated signaling pathways is a novel approach for decreasing TMZ resistance in GBM. To the authors' knowledge, this is the first study in a humanized intracranial patient-derived xenograft model to demonstrate the efficacy of combining front-line TMZ therapy and an inhibitor of MDM2 protein-protein interactions.
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Anhui Provincial Cancer Hospital, Hefei, Anhui, China; and.
authors.forename: Shanbao
authors.initials: S
authors.lastname: Cai
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Bailey
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Goodman Campbell Brain and Spine, Department of Neurosurgery.
authors.forename: M
authors.initials: M
authors.lastname: Reza Saadatzadeh
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Goodman Campbell Brain and Spine, Department of Neurosurgery.
authors.forename: Jixin
authors.initials: J
authors.lastname: Ding
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Indiana University Simon Cancer Center.|Department of Pharmacology and Toxicology.
authors.forename: Eva
authors.initials: E
authors.lastname: Tonsing-Carter
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: Taxiarchis M
authors.initials: TM
authors.lastname: Georgiadis
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: T
authors.initials: T
authors.lastname: Zachary Gunter
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Long
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Minto
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Gordon
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis.
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Sen
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Cai
authors.affiliation: Department of Radiology and Imaging Science, Indiana University, Indianapolis, Indiana.
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Eitel
authors.affiliation: Indiana University Simon Cancer Center.|Department of Medicine, Division of Endocrinology.
authors.forename: David L
authors.initials: DL
authors.lastname: Waning
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine.
authors.forename: Lauren R
authors.initials: LR
authors.lastname: Bringman
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine.
authors.forename: Clark D
authors.initials: CD
authors.lastname: Wells
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Murray
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Jann N
authors.initials: JN
authors.lastname: Sarkaria
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Gelbert
authors.affiliation: Division of Clinical Pharmacology.
authors.forename: David R
authors.initials: DR
authors.lastname: Jones
authors.affiliation: Indiana University Simon Cancer Center.|Goodman Campbell Brain and Spine, Department of Neurosurgery.
authors.forename: Aaron A
authors.initials: AA
authors.lastname: Cohen-Gadol
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Indiana University Simon Cancer Center.
authors.forename: Lindsey D
authors.initials: LD
authors.lastname: Mayo
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.
authors.forename: Harlan E
authors.initials: HE
authors.lastname: Shannon
authors.affiliation: Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Section of Pediatric Hematology/Oncology, Riley Hospital for Children at Indiana University Health.|Indiana University Simon Cancer Center.|Department of Pharmacology and Toxicology.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Pollok
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use*; D001932:Brain Neoplasms / Q000473:pathology / Q000628:therapy*; D003131:Combined Modality Therapy; D004195:Disease Models, Animal; D005909:Glioblastoma / Q000473:pathology / Q000628:therapy*; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use*; D010879:Piperazines / Q000627:therapeutic use*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors*; D000077204:Temozolomide / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
chemical_list: D018906:Antineoplastic Agents, Alkylating; D007093:Imidazoles; D010879:Piperazines; C482205:nutlin 3; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D000077204:Temozolomide
keywords: APE1 = apurinic/apyrimidinic endonuclease I; ATM = ataxia-telangiectasia mutated; BER = base excision repair; BSA = bovine serum albumin; DNA repair; FBS = fetal bovine serum; GAPDH = glyceraldehyde-3-phosphate-dehydrogenase; GBM = glioblastoma; IUSCC, IUSM = Indiana University Simon Cancer Center, Indiana University School of Medicine; MDM2; MDM2 = murine double minute 2; MDM2 inhibitor; MGMT = O6-methylguanine DNA methyltransferase; MS = mass spectroscopy; NSG = NOD.Cg-PrkdcscidIL2rgtm1Wjl/Sz; PBS = phosphate-buffered saline; PK = pharmacokinetic; PPI = protein–protein interaction; S15 = phosphorylation on serine 15-p53; T/N = combination of TMZ and nutlin3a; TBS = Tris-buffered saline; TBST = TBS and Tween 20; TMZ = temozolomide; combination therapy; glioblastoma; oncology; p53; patient-derived xenograft; temozolomide