The expression of human papillomavirus type 16 (HPV16 E7) induces cell cycle arrest and apoptosis in radiation and hypoxia resistant glioblastoma cells

Sung Ung Moon, Soo Kyoung Choi, Han J.O. Kim, Kiran Kumar Bokara, Kyung A.H. Park, Won Taek Lee, Jong Eun Lee

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

p53 is a widely known tumor-suppressor gene product that plays a key role in apoptotic cell death induced by DNA-damaging chemotherapeutic agents. Human glioma cells with functional p53 are known to be more resistant to γ-radiation. The aim of this study was to investigate whether the mutant glioblastoma cells (U87MG) transfected with human papilloma virus-type 16 E7 (HPV16 E7) genes were capable of increasing sensitivity towards irradiation and hypoxia-induced cell death. The pLXSN retroviral vector expressed HPV-16E7 genes and was infected into the p53 mutated U87MG cell line. A specific amplification band of HPV16 E7 genes was detected in E7 genes and transfected in the U87MG cell line using a reverse transcriptase polymerase chain reaction. The experimental groups included the mutant glioblastoma cell line (U87MG), empty vector (pLXSN) transfected to mutant glioblastoma cell line (U87MG-LXSN), and retrovirus carrying HPV16 E7 genes transfected to the mutant glioblastoma cell line (U87MG-E7). Hypoxic conditions were optimized using LDH assay and the subjects were exposed to hypoxia (16 and 20 h) and irradiation (9 h). Hoechst-propidium iodide (PI) staining results showed that hypoxia and irradiation increased the number of dead cells in the U87MG-E7 cells compared to U87MG and U87MG-LXSN cells. Results of the FACS analysis showed a similar pattern and recorded 80.44 and 58.94% of apoptotic cells in U87MG-E7 and U87MG cells, respectively. Cell cycle analysis by FACS revealed that, following irradiation and hypoxia, cells showed G2-M arrest. Additionally, the Western blot analysis results showed altered expression of E2F-1, Rb and p53 in the irradiation- and hypoxia-induced U87MG-E7 cells compared to U87MG and U87MG LXSN cells. In conclusion, the over-expression of HPV16 E7 genes in U87MG cell lines increasd cell apoptosis and E2F1 expression compared to the HPV non-infected U87MG cells following irradiation and hypoxia. These results indicate that tumor-specific therapies that increase sensitivity towards radiation and hypoxic conditions may be beneficial for suppression of cancers.

Original languageEnglish
Pages (from-to)1247-1253
Number of pages7
JournalMolecular Medicine Reports
Volume4
Issue number6
DOIs
Publication statusPublished - 2011 Nov

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Genetics
  • Oncology
  • Cancer Research

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