Expression of Etk/Bmx tyrosine kinase in the tumorigenicity of nasopharyngeal epithelium and its relation with EB virus infection and the apoptosis-related protein Bcl-2

Abstract

We compared Etk/Bmx expression in nasopharyngeal carcinoma (NPC) and non-neoplastic nasopharyngeal lesions in order to learn whether the expression of this non-receptor protein tyrosine kinase is associated with the development of NPC. We also related Etk/Bmx expression to factors resulting from Epstein-Barr virus (EBV) infection. We used immunohistochemistry (IHC) and in situ hybridization to examine 20 non-neoplastic nasopharyngeal lesions and 49 cases of NPC to assess Etk/Bmx, EB virus latent membrane protein-1 (LMP-1), Bcl-2 and EBV-encoded small RNA-1 expression in these samples. Etk/Bmx expression was present in the basal cell nuclei of the nasopharyngeal epithelium in 1/9 (11.1%) cases of chronic nasopharyngitis and 2/11 cases (18.2%) of dysplasia. While 13/49 (26.5%) NPC cases expressed Etk/Bmx, the difference in frequency between the expression of Etk/Bmx in the non-neoplastic and NPC cases was not significant. Etk/Bmx expression was correlated with the presence of EBER-1 immunopositivity in dysplasia and in NPC but not in chronic nasopharyngitis. The presence of Etk/Bmx immunopositivity was independent of the expression of either LMP-1 or Bcl-2 in either the nasopharyngeal carcinoma or the non-neoplastic lesions. This suggests that in some cases of non-neoplastic and neoplastic nasopharyngeal lesions, Etk/Bmx may participate in regulating epithelial differentiation. While EBV-related small RNA-1 may participate in this regulation, neither LMP-1 or Bcl-2 expression appears to be related to Etk/Bmx expression.