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The tumor supressor function of STGC3 and its reduced expression in nasopharyngeal carcinoma


STGC3 is a novel candidate tumor suppressor gene that was found to be associated with nasopharyngeal carcinoma (NPC) via the cDNA cloning and RACE processes. The biological function of the STGC3 protein and its expression level in nasopharyngeal carcinoma remain unknown. This study aimed to evaluate the STGC3 protein expression level in NPC and to investigate the inhibitory function of STGC3 as a candidate tumor suppressor gene. We assessed the expression of the STGC3 protein in NPC biopsies and normal control specimens via Western blot and immunohistochemical analysis. The expression of STGC3 as induced by doxycycline (Dox) via a tetracycline (Tet)-regulated system in human nasopharyngeal carcinoma cell line CNE2 was also established, and the effect of STGC3 restoration on the biological behavior of CNE2 was observed. A reduced level of STGC3 expression (0.978 ± 0.213 versus 0.324 ± 0.185, P < 0.05) was detected in NPC versus normal nasopharyngeal tissue by Western blot assay. Immunohistochemical assays for STGC3 detected positive staining in the nuclei and cytoplasm of epithelial cells, and the positive expression rate in NPC, 8 of 21 (38%), was lower than that in normal nasopharynx samples, 16 of 22 (72%). After STGC3 expression was restored, the growth capacity and clone formation potential of CNE2 cells in soft agar were significantly suppressed, and the cell percentage in G0/G1 phase increased, while the percentage of cells entering the S and G2 phases decreased. This indicates that an abnormality in STGC3 expression is associated with nasopharyngeal carcinogenesis and that it may play an important role in controlling cell growth and regulating the cell cycle.



AMV reverse transcriptase


one-way analysis of variance






flow cytometry


integral optical densities


nasopharyngeal carcinoma


phosphate-buffered saline


propidium iodide


polyvinylidene difluoride


Rapid Amplification of cDNA End


reverse tetracycline/doxycycline-responsive transcriptional activator






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Correspondence to Xiu-Sheng He or Zhu-Chu Chen.

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He, XS., Deng, M., Yang, S. et al. The tumor supressor function of STGC3 and its reduced expression in nasopharyngeal carcinoma. Cell Mol Biol Lett 13, 339–352 (2008).

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  • Nasopharyngeal neoplasm
  • STGC3
  • Gene expression
  • Tet-on system