Expression of Epstein-Barr Virus Gene Products, Bcl-2 and p53 Proteins in Nasopharyngeal Carcinomas

ABSTRACT

The authors studied EBV genome expression in 40 conventionally processed samples of nasopharyngeal carcinomas (NPC), using in situ hybridization for EBERs and immunohistochemistry for LMP, Bcl-2 and p53 proteins. The NPCs consisted of 6 keratinizing squamous cell carcinomas (KSCs), 13 nonkeratinizing carcinomas (NKCs) and 21 undifferentiated carcinomas (UCs). The results were summarized as follows 1) EBERs were expressed in 80.0% of all the NPCs (32/40). As for the subtypes, they were detected in 92.3% of NKCs (12/13), in 90.5% of the UCs (19/21), and in 16.7% of the KSCs (1/6). In positive cases, the nuclei of tumor cells displayed uniformly strong staining. 2) LMP was expressed in 10.0% of all the NPCs (4/40), all of which were UC. The LMP expression in the UCs was not correlated to the expression of EBERs, Bcl-2 and p53 proteins. 3) Bcl-2 protein was detected in 85.0% of all the NPCs (34/40). As for the subtypes, they were detected in 92.3% of the NKCs (12/13), in 90.5% of the UCs (19/21), and in 50.0% of the KSCs (3/6). 4) p53 protein was detected in 75.0% of all the NPCs (30/40). As for the subtypes, they were detected in 81.0% of the UCs (17/21), in 69.2% of the NKCs (9/13), and in 66.7% of the KSCs (4/6). 5) In the NPCs the expression of EBER showed a significantly positive correlation with that of p53 or Bcl-2 protein. The above results indicate that the association of EBV with NPC is chiefly with poorly differentiated and undifferentiated carcinomas. Additionally, carcinomas commonly display widespread, strong immunoreactivity of Bcl-2 and p53 proteins over tumor cells. In conclusion, these observations indicate that the EBV-association in NPC appears to contribute to the overexpression of tumor-related genes during carcinogenesis.