title: Radioresistance of human glioma spheroids and expression of HSP70, p53 and EGFr.
abstract: BACKGROUND
  Radiation therapy is routinely prescribed for high-grade malignant gliomas. However, the efficacy of this therapeutic modality is often limited by the occurrence of radioresistance, reflected as a diminished susceptibility of the irradiated cells to undergo cell death. Thus, cells have evolved an elegant system in response to ionizing radiation induced DNA damage, where p53, Hsp70 and/or EGFr may play an important role in the process. In the present study, we investigated whether the content of p53, Hsp70 and EGFr are associated to glioblastoma (GBM) cell radioresistance.
  
  
  METHODS
  Spheroids from U-87MG and MO59J cell lines as well as spheroids derived from primary culture of tumor tissue of one GBM patient (UGBM1) were irradiated (5, 10 and 20 Gy), their relative radioresistance were established and the p53, Hsp70 and EGFr contents were immunohistochemically determined. Moreover, we investigated whether EGFr-phospho-Akt and EGFr-MEK-ERK pathways can induce GBM radioresistance using inhibitors of activation of ERK (PD098059) and Akt (wortmannin).
  
  
  RESULTS
  At 5 Gy irradiation UGBM1 and U-87MG spheroids showed growth inhibition whereas the MO59J spheroid was relatively radioresistant. Overall, no significant changes in p53 and Hsp70 expression were found following 5 Gy irradiation treatment in all spheroids studied. The only difference observed in Hsp70 content was the periphery distribution in MO59J spheroids. However, 5 Gy treatment induced a significant increase on the EGFr levels in MO59J spheroids. Furthermore, treatment with inhibitors of activation of ERK (PD098059) and Akt (wortmannin) leads to radiosensitization of MO59J spheroids.
  
  
  CONCLUSIONS
  These results indicate that the PI3K-Akt and MEK-ERK pathways triggered by EGFr confer GBM radioresistance.
authors.affiliation: Laboratório de Marcadores de Estresse Celular, Universidade Luterana do Brasil, Canoas, RS, Brasil.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Fedrigo
authors.forename: Ivana
authors.initials: I
authors.lastname: Grivicich
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Schunemann
authors.forename: Ivan M
authors.initials: IM
authors.lastname: Chemale
authors.forename: Daiane
authors.initials: D
authors.lastname: dos Santos
authors.forename: Thais
authors.initials: T
authors.lastname: Jacovas
authors.forename: Patryck S
authors.initials: PS
authors.lastname: Boschetti
authors.forename: Geraldo P
authors.initials: GP
authors.lastname: Jotz
authors.forename: Aroldo
authors.initials: A
authors.lastname: Braga Filho
authors.forename: Adriana B
authors.initials: AB
authors.lastname: da Rocha
mesh_terms: D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D066246:ErbB Receptors / Q000096:biosynthesis*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D010766:Phosphorylation; D018874:Spheroids, Cellular; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D016159:Tumor Suppressor Protein p53; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases
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