Gene analysis of Epstein-Barr virus-associated lymphomas in Hu-Pbl/SCID chimeras.

AIMS AND BACKGROUND

The mechanisms of Epstein-Barr virus (EBV)-associated tumor development are incompletely understood. The aim of this study was to investigate the gene expression of EBV-associated lymphomas in hu-PBL/SCID mice.

METHODS

Human peripheral blood lymphocytes (hu-PBL) from EBV-seropositive donors were transplanted into severe combined immunodeficiency (SCID) mice. In situ hybridization was used to detect EBV-encoded small RNA- 1 (EBER1) in tumor tissues. Mutation of TP53 exons 5-8 in EBV-induced lymphomas was analyzed by PCR-SSCP. Immunohistochemical staining was used to examine EBV gene products and cellular oncoproteins.

RESULTS

Twenty-one of 29 mice developed tumors. EBER1 was positive in the nuclei of almost all tumor cells. Immunohistochemistry showed positive staining of LMP1, EBNA2 and ZEBRA in a small number of tumor cells. Immunohistochemically detectable p53 protein expression was common (85.7%), but TP53 gene mutations were identified in only four cases (19.1%) of EBV-associated lymphomas. Positivity rates of C-myc, Bcl-2 and Bax expression were 100%, 95.2%, and 90.5%, respectively, in the 21 cases of EBV-associated lymphomas.

CONCLUSIONS

Our preliminary findings suggest that EBV-associated lymphomas in hu-PBL/SCID chimeras show EBV infection, expression of oncogenic viral genes, and overexpression of cellular oncogenes. TP53 gene mutations are rare but p53 protein is commonly expressed in EBV-associated lymphomas.