P53 OVEREXPRESSION AND EPSTEIN-BARR-VIRUS INFECTION IN UNDIFFERENTIATED AND SQUAMOUS-CELL NASOPHARYNGEAL CARCINOMAS

We have analysed 22 nasopharyngeal carcinomas (NPCs) for expression of the small nuclear Epstein-Barr virus (EBV)-encoded RNAs (EBERs) and f or immunohistologically detectable overexpression of p53. In situ hybr idization demonstrated expression of the EBERs in 13 undifferentiated NPCs while nine squamous cell NPCs were EBER-negative. These results t herefore confirm our previous DNA-DNA in situ hybridization studies an d demonstrate that in the nasopharynx EBV is exclusively associated wi th undifferentiated but not with squamous cell carcinomas. p53 overexp ression was demonstrated by immunohistology in 5 of 9 squamous cell NP Cs and in 9 of 13 undifferentiated NPCs. Thus, there appears to be no correlation of p53 overexpression with EBV infection. These results ar e unexpected in the light of previous studies demonstrating that the p 53 gene in primary undifferentiated NPC is consistently in the wild-ty pe configuration. By contrast, analyses of squamous cell carcinomas of the head and neck have demonstrated that p53 overexpression in these cases is the result of p53 gene mutation. Whilst more detailed genetic analysis is required, our results suggest that mechanisms other than mutation of the p53 gene may be responsible for the stabilization of t he protein in cases of undifferentiated NPC. It is tempting to specula te that an EBV-encoded protein may be involved.