Overexpression of deletion-mutant epidermal growth factor receptor is associated with altered genotoxic stress-provoked p53 mRNA induction in a human glioblastoma cell line.
A distinct 801-bp deletion mutation of the epidermal growth factor receptor (EGFR) gene is frequently present in primary glioblastoma multiforme (GBM), confers enhanced tumorigenicity in vivo and is prognostic of a shorter interval to clinical relapse. This study sought to investigate whether overexpression of deletion-mutant (delta) EGFR affects genotoxic stress-provoked mRNA inductions of p53 and murine double minute 2 (MDM2), two other genes strongly involved in the pathogenesis of GBM. In a set of human wild-type (wt) p53 GBM cell lines (U-87MG and U-87MG.delta EGFR) that exclusively differ in EGFR expression (endogenous wt EGFR expression and exogenous delta EGFR overexpression, respectively), ultraviolet (UV) light irradiation-mediated EGFR, p53 and MDM2 genotoxic stress-provoked mRNA inductions were assessed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and densitometry of electrophoretically separated and stained RT-PCR products. Although baseline (at 0 J/m2) p53 mRNA expression in U-87MG.delta EGFR was 42-fold reduced, maximum p53 induction (at 8 J/m2) amounted to 130% compared to U-87MG. Thus, ultimate UV light-mediated p53 mRNA induction was 131.5-fold in U-87MG.delta EGFR and 2.8-fold in U-87MG. In contrast, neither wt/delta EGFR nor MDM2 mRNA expressions were significantly inducible, and MDM2 mRNA profiles were essentially the same among U-87MG and U-87MG.delta EGFR. These data suggest that in human GBM overexpression of delta EGFR is associated with differential genotoxic stress-provoked p53 mRNA induction whereas MDM2 mRNA expression is apparently not directly affected by EGFR status.
Halatsch
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ME
Division of Medical Oncology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA. halatsch@aol.com
Schmidt
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Holland
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Ohnuma
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D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D005909:Glioblastoma / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D051736:Proto-Oncogene Proteins c-mdm2; D012333:RNA, Messenger / Q000096:biosynthesis / Q000528:radiation effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D015533:Transcriptional Activation / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics*; D014466:Ultraviolet Rays
D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D066246:ErbB Receptors