Simian Virus 40 Oncogenesis in Hamsters.

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When the virus is injected subcutaneously, sarcomas at the site of injection .... for the intracardiac injection, which becomes SV40-contaminated when the needle.
Brown F, Lewis AM (eds): Simian Virus (SV40): A Possible Human Polyomavirus. Dev Biol Stand. Basel, Karger, 1998, vol94, pp 273-279

Simian Virus 40 Oncogenesis in Hamsters. M. carbone'. R..~tach'.I. Di Rests'. H.I. pas.?. P Rizzo' /"A'

' Cancer Immunology Program,:Card~nalBernardin Cancer Center and Department of Pathology, Loyola University of Chicago, Maywood, Illinois, USA4 Aerodigestive Program, Karmanos Cancer Institute, Detroit, MI, U.S.A. Key words: SV40, oncogenesis, hamsters. Abstract: Simian virus 40 (SV40) is a DNA tumour virus which is highly oncogenic In hamsters.

Only specific histologic types of tumours develop in hamsters injected with SV40, and these are influenced by the route of virus inoculation. When SV40 is injected systemically to expose most different cell types to the virus, the animals develop mesotheliomas, osteosarcomas, sarcomas, and lymphomas within six months. When the virus is injected subcutaneously, sarcomas at the site of injection develop. If hamsters are injected intracranially with SV40, they develop ependymomas. These same tumour types have been found to contain SV40.

Poliovaccines (and adenovaccines) were prepared in Rhesus monkey kidney cells. Dr. Bernice Eddy at the NIH investigated the possibility that these cells harboured oncogenic viruses. In 1960 she demonstrated that the subcutaneous injection of Rhesus monkey kidney cells into newborn hamsters induced sarcomas at the site of inoculation. These findings were initially questioned, but they were eventually published in 1961[1]. In 1960, Sweet and Hilleman had also reported the discovery of a new simian virus in Rhesus monkey kidney cells which induced characteristic cytopathic effects. These authors demonstrated that this virus, which was called SV40, contaminated both the Salk and the Sabin poliovaccines. People injected with the Salk inactivated vaccine developed neutralizing antibodies against SV40, while people fed with the oral attenuated Sabin vaccine did not [2]. The presence of live SV40 in the inactivated vaccine was explained by the failure to inactivate a part of the contaminating SV40 virions by the formaldehyde treatment used to prepare the vaccines. In 1962, Dr. Eddy reported that SV40 was the oncogenic virus in Rhesus monkey kidney cell extracts responsible for the production of sarcomas in newborn hamsters [3], and the ability of SV40 to induce subcutaneous sarcomas in hamsters was soon confirmed by several other investigators [4]. In addition, it was

shown that the intracranial injection of SV40 induced ependymomas in both hamsters [5] and in Mastomys, an African rodent intermediate in size between the rat and the mouse [6]. The oncogenicity of SV40 when injected systemically was studied by Diamandopoulous who injected SV40 in 150 hamsters through the femoral vein to expose most different cell types to the virus. 125 of the 150 hamsters developed tumours, and occasionally more than one tumour type was detected in the same animal. These hamsters developed abdominal and mediastinal lymphomas, osteosarcomas and sarcomas, and one single lymphocytic lymphoma 171. These experiments indicated that only specific cell types could be transformed by SV40 in hamsters, and that the most common cancer in humans, carcinomas and adenocarcinomas, did not develop in hamsters following SV40 injection. The oncogenicity of SV40 is related to the presence and the expression of the SV40 large T-antigen (Tag). Tag is a 90 kDa multifunctional protein that binds and inhibits several tumour suppressor gene products in the host cells, including p53, Rb, p107, p130, p300, and p400 [8]. By inhibiting p53, Tag also eliminates an important cellular check point that blocks cell division and induces apoptosis in cells containing DNA alterations. Cells containing inactivated p53 (by mutation or by its binding with Tag) continue to divide in the presence of DNA alterations, and the accumulation of these DNA aberrations may play an important role in the maintenance of the transformed phenotype [9]. Furthermore, Tag stimulates IGF-1 and IGF-IR, and this stimulates cell division and oncogenesis, especially in the absence of functional tumour suppressors [lo]. Small t is the other viral protein produced by the early region of SV40. In 1979 Lewis and Martin studied the possible role of small t in SV40-mediated oncogenesis. They found that small t mutants injected subcutaneously (sc) into hamsters induced tumours with a prolonged latency when compared to hamsters injected with wild-type SV40 [Ill. Three years later, Dixon et a1 discovered that hamsters injected sc with SV40 small t mutants not only developed sarcomas at the site of injection with a prolonged latency but also developed tumours in the abdominal cavity. These abdominal tumours developed in approximately 15% of injected hamsters, and at the time these were interpreted as metastases from the sc sarcomas [12]. These abdominal tumours never developed following injection of SV40 wildtype (wt) [12]. Further investigations of these abdominal tumours induced by small t mutants revealed that these were not metastases, but true histiocytic lymphomas originating from a specific subpopulation of mononuclear phagocytes which expressed the activation antigen MAC-2 [13]. We were intrigued by these findings because it appeared that small t mutants had a particular tropism for mononuclear phagocytes. We tested this hypothesis by injecting hamsters with small-t mutants intracardially to expose most different cell types to the virus. Control groups of hamsters were injected with medium alone or with wt SV40.

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80 hamsters, 40 males and 40 females, were injected with lo8.'plaque forming units (pfu) of wt SV40 (26 hamsters), SV40 small t mutants dl 2006 (22 hamsters) and dl 883 (12 hamsters), and with medium alone (20 hamsters) into the left cardiac ventricle. Furthermore, 15 hamsters were injected directly into the pleural space with wt SV40 (11 hamsters), or medium alone (four hamsters); and 10 hamsters were injected intraperitoneally with wt SV40 (six hamsters) or medium alone (four hamsters). The volume injected using a 25-gauge cannula was 0.2 rnl of DMEM containing 2% of FBS,

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