Overexpression of inducible nitric oxide synthase and accumulation of 8-OHdG in nasopharyngeal carcinoma

Y. Segawa, Y. Oda, H. Yamamoto, H. Uryu, H. Shiratsuchi, N. Hirakawa, K. Tomita, T. Yamamoto, S. Oda, T. Yamada, S. Komune, M. Tsuneyoshi

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19 Citations (Scopus)


Aims: Nitric oxide (NO), produced by inducible NO synthase (iNOS), has been suggested to cause oxidative stress, leading to 8-hydroxydeoxyguanosine (8-OHdG) accumulation and subsequent transversion mutation of DNA. The aim was to evaluate iNOS expression and the status of oxidative stress in nasopharyngeal carcinoma (NPC). Methods and results: Seventy-three cases of NPC were investigated to examine the immunohistochemical expression of iNOS, 8-OHdG and latent membrane protein-1 (LMP-1) and Epstein-Barr virus-encoded small RNA (EBER) expression using in situ hybridization. iNOS mRNA expression and p53 gene mutations were also assessed. Overexpression of iNOS, LMP-1 and EBER was observed in 62 (84.9%), 28 (38.4%) and 53 (72.6%) cases respectively. p53 gene mutation was found in 10 of 73 (13.7%) cases. Immunohistochemical iNOS expression was associated with the 8-OHdG labelling index, iNOS mRNA expression and p53 gene alteration (P < 0.0001, P = 0.016 and 0.0082 respectively). Conclusions: Our present findings suggest that the expression of iNOS induces oxidative stress in NPC. Although the presence of p53 mutation was associated with iNOS overexpression, the type of acid-base change of p53 was transition, but not transversion, which suggests that the p53 gene is not the direct target of DNA damage by 8-OHdG accumulation.

Original languageEnglish
Pages (from-to)213-223
Number of pages11
Issue number2
Publication statusPublished - Jan 2008

All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine
  • Histology


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