The effects of combining ionizing radiation and adenoviral p53 therapy in nasopharyngeal carcinoma

Int J Radiat Oncol Biol Phys. 1999 Feb 1;43(3):607-16. doi: 10.1016/s0360-3016(98)00432-5.


Purpose: Nasopharyngeal carcinoma (NPC) is a malignant disease of the head/neck region, with a 5-year survival level of approximately 65%. To explore gene therapy as a novel approach which might improve outcome, we have shown previously that introduction of human recombinant wild-type p53 mediated by the adenoviral vector (Ad5CMV-p53) was cytotoxic in two human nasopharyngeal carcinoma (NPC) cell lines (CNE-1 and CNE-2Z). The current work was designed to determine whether this strategy, combined with ionizing radiation (XRT), was more effective than either treatment alone.

Methods and materials: CNE-1, CNE-2Z, and a normal human nasopharyngeal fibroblast strain, KS1, were infected with 2- and 6-plaque-forming units (pfu)/cell of Ad5CMV-p53, respectively. These doses were isoeffective for beta-galactosidase activity in the CNE-1 and CNE-2Z cells. XRT was administered 24 h post-infection, and Western blot analyses were conducted for p53, p21WAF1/CIP1, bax, and bcl-2 2 days after XRT. Cell survival was assessed using a clonogenic assay. Presence of DNA ladders reflecting apoptosis was detected using DNA agarose gel electrophoresis, and cell cycle was analyzed using flow cytometry.

Results: The combination of Ad5CMV-p53 plus XRT (2, 4, and 6 Gy) resulted in an approximately 1-log greater level of cytotoxicity compared to that observed with XRT alone for both NPC cell lines. The two modalities appear to be interacting in a synergistic manner in cancer cells, but not in KS1 fibroblasts. XRT alone stimulated minimal p53 expression in control cells; Ad5CMV-p53 alone induced significant recombinant p53 expression, which was not further enhanced by the addition of XRT. Similar observations were made for p21WAF1/CIP1 expression. No changes were observed for bax or bcl-2 expression with any of these treatments. Apoptosis was induced following 4 Gy of XRT alone, but was observed after only 2 Gy when combined with Ad5CMV-p53. Cell cycle analysis indicated that Ad5CMV-p53 infection did not perturb the cell cycle beyond that observed with XRT alone.

Conclusion: p53 gene therapy and XRT appears to interact in a synergistic manner; underscoring the significant potential of this novel strategy in the treatment of NPC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / enzymology
  • Combined Modality Therapy
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins / metabolism
  • DNA Fragmentation
  • Fibroblasts / radiation effects
  • Fibroblasts / virology
  • Genes, p53*
  • Genetic Therapy / methods*
  • Genetic Vectors / administration & dosage*
  • Genetic Vectors / genetics
  • Humans
  • Nasopharyngeal Neoplasms / radiotherapy
  • Nasopharyngeal Neoplasms / therapy*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Radiotherapy Dosage
  • Tumor Suppressor Protein p53 / metabolism
  • bcl-2-Associated X Protein
  • beta-Galactosidase / metabolism


  • BAX protein, human
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • beta-Galactosidase