Examination of Epstein-Barr virus and C-type proviral sequences in American and African lymphomas and derivative cell lines.

While Epstein-Barr viral (EBV) DNA is nearly always detectable in African Burkitt's lymphoma (BL), the relatively low frequency of BL in EBV-positive African children and the infrequent finding of EBV in American BL suggest that other cofactors may contribute to the malignant transformation. Among these possible cofactors are type C oncornaviruses. To evaluate this possibility, we screened the cellular DNA from 16 lymphomas (2 African, 14 American) and the DNA from 20 lymphoma-derived cell lines (4 African, 16 American) with a radiolabeled viral DNA probe from EBV and two oncornaviral probes (murine amphotropic 1504A virus and simian sarcoma virus). The radiolabeled EBV DNA probe hybridized with 18 of 36 tumor or cell line DNA's. Only 2 of 11 American BL tumors contained detectable EBV sequences. However, the cell lines derived from three EBV-negative tumors converted in vitro to EBV positivity, suggesting that some of the tumor cells could be infected with EBV. In contrast, none of the tumors or the cell lines derived therefrom hybridized with either the 1504A or the simian sarcoma virus probes, decreasing the likelihood that type C viruses are cofactors with EBV.