Oncogenic properties of nucleic acid derived from SV-40 virus

The present report describes the findings on the infectivity of DNA partially purified from SV-40 which was propagated in the monkey kidney cells (BSC-1) in vitro and the importance of nucleic acids as oncogenic factors, particularly the induction of tumor by DNA in newborn hamsters. 593 newborn hamsters in total were used in the present experiments, and cannibalism among them posed as a serious problem. On 30 days postinoculation, very remarkable changes occurred in the liver, lung and subcutaneous areas. Cellular responses of the perivascular cells were predominant. and they were distributed in the interstitial tissues of the liver (liver cirrhosis in primates) and lung. Three hamsters of those subcutaneously inoculated with nucleic acids developed tumors and two tumors appeared in the subcutaneous tissues on 130 days postinoculation, which were identified to be the ones induced by intact SV-40 virus. Other tumors appeared in the liver, lung, intestinal ducts and abdominal surface at 126 days after subcutaneous injection. The cytological observations revealed multiple hemangiosarcoma combined with proliferation of the perivascular cells. On the other hand, cellular responses to nucleic acids were more marked by inoculation of the cell-free filtrate of BSC-1 infected by DNA than of DNA, and essential histologic findings were similar to the respo.nse to infectious DNA. Thirty-nine hamsters (30 per cent) developed tumor within about 200 days postinoculation of the filtrates. Sarcomas were common and they were confined to the subcutaneous tissues in 35 hamsters and to the peritoneum in two others by subcutaneous inoculation of the filtrates. The intestinal gland-cell carcinomas, however, could be induced at 37 and 59 days postinoculation in two hamsters of one litter (7 newborn hamsters) and in the other three newborn hamsters subcutaneous sarcomas were induced by inoculation of the same agent. These results suggest that the observation on the oncogenic capacity of nucleic acids would give us a clue to resolve the course of cancer from the view point of the infectious nucleic acid.