We previously showed that the Epstein-Barr virus, which encodes the BARF1 gene, could transform rodent fibroblasts. In this work, the expression of the BARF1 gene was studied in the human Louckes B-lymphocyte cell line. Introduction of the BARF1 open reading frame under the control of the Mo-MuLV LTR promotor into nontumorigenic Louckes lymphoid cells led to the activation of the c-myc protooncogene and increased expression of the B-cell surface proteins, the transferrin receptor, CD21, and CD23. BARF1-expressing cells induced a diffuse lymphoma-like tumor in newborn rats treated with anti-thymocyte serum that was, however, transient and regressed after 3–4 weeks as the immune system recovered. The tumor induction was similar to that observed with lymphoid cell lines in vitro generated by infection with the B95–8 virus strain, in which lytic antigens are expressed at low levels. After long-term culture, Louckes cell clones lost expression of the BARF1 gene and were unable to induce tumors.

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This project was supported by grants from the INSERM (no. 910111), the “Fondation de France,” the Fédération Nationale des Groupements des Entreprises Françaises dans la Lutte contre le Cancer, and the Association pour la Recherche sur le Cancer (no. 6162).

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