Leukemia, lymphoma, and osteogenic and anaplastic sarcomas develop in Syrian golden hamsters inoculated intravenously at 3 weeks of age with simian virus 40, which is a popova virus. Previously, only RNA and herpes DNA viruses have been recognized as capable of inducing leukemia and lymphoma in mammals. The significance of these findings is emphasized in relation to the nature of viral agents that may be involved in analogous diseases of man.

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Abstract.-A number of homologous SV40-exposed hamster embryonic cell lines were examined for the presence of RNA complementary to SV40 DNA. Only those lines containing the SV40 T antigen were found to have such virusspecific RNA. In lines containing the SV40 S antigen, but not the SV40 T antigen, virus-specific RNA was not detected. These findings suggest that the S antigen is not coded for directly by the SV40 genome.A new and apparently virus-specific antigen associated with the surface of SV40-transformed hamster cells1 and of cells acutely infected by SV40 virus has recently been described.2 Diamandopoulos et al. have shown that this new antigen (S antigen) appeared in hamster embryonic cells transformed by SV40 virus, but not in homologous "spontaneously" transformed cells.3 Although these observations suggest that S antigen production is specifically dependent upon exposure to the virus, they do not distinguish between two possible mechanisms: the derepression of host genetic information or the persistence and function of viral genetic information. It should be possible to decide which of these mechanisms may be operative by assaying for virus-specific nucleic acid in the appropriate cell lines. In order to make potentially meaningful biochemical comparisons between cell lines, it is important that significant differences in growth characteristics and genetic background be minimized. The hamster embryonic cell lines of Diamandopoulos et al.3 meet these criteria and thus offer an opportunity to study the nucleic acids of homologous cells, maintained under the same conditions, which have become oncogenic spontaneously or have become oncogenic after exposure to SV40. Some of these lines contain both the SV40 tumor (T) and S antigens, some contain only the S antigen, while others contain neither the S nor the T antigen. We have examined several of these cell lines for the presence of virus-specific nucleic acids. The findings are summarized in this communication.Materials and Methods.-Cell lines: The tumor cell lines employed in these studies were derived from the first hamster passage of SV40-exposed or unexposed hamster embryonic cell lines (E, M, P, and 2Ps).3 Aliquots of each tumor cell line were thawed and propagated in 32-oz. glass bottles in a modified Eagle's medium4 containing four times the usual concentrations of vitamins and amino, acids, glutamine (8 mM), penicillin (100 units/ml), streptomycin (100 jg/ml), and 10% unheated fetal bovine serum. Large roller bottles (Bellco Glass Co., no. 7013) were seeded with 30-50 X 101 cells in 120 ml medium. The bottles were rolled at 0.9 rpm (Bellco cell production apparatus No. 7510) at 370C and the medium was changed at 3-day intervals until confluent monolayers were formed. Included in the study were tumor cells from two SV40-exposed lines that contained both the S and T antigens, from two SV4O-exposed lines that contained the S 589

Several homologous hamster embryonic cell lines, transformed in association with simian virus (SV) 40 infection, were examined for the presence of deoxyribonucleic acid (DNA) complementary to SV40 ribonucleic acid (RNA) made in vitro. The methods employed permitted the detection of 10 −5 μg of viral DNA in 100 μg of cellular DNA, corresponding to one-fifth of an SV40 DNA molecule per cell. Those lines which contained both the SV40 surface (S) and tumor (T) antigens also contained DNA complementary to SV40 RNA synthesized in vitro. In contrast, neither of two lines which contained S, but not T, antigen contained detectable DNA complementary to SV40 RNA. These findings suggest that the production of S antigen does not depend upon the persistence of SV40 DNA in transformed cells.