SV40 DNA in human osteosarcomas shows sequence variation among T-antigen genes

Authentic simian virus 40 (SV40) has been detected in association with human choroid plexus and ependymoma tumors, and SV40-like DNA sequences have been found in some human osteosarcomas. We report here an analysis of human osteosarcoma samples for the presence of SV40 DNA using PCR and primers directed at 4 distinct sites of the SV40 genome, coupled with sequence analysis. Authentic SV40 DNA sequences were detected in 5 of 10 osteosarcoma tumor samples. The SV40 regulatory region in each case was identical and of archetypal length (non-duplicated enhancer), as is usually found in natural isolates of SV40 from monkeys and in human brain tumors. A section of the gene that encodes a viral late gene product (VP1) was detected in 5 of 10 tumors and had an exact match with the known sequence of SV40. Two separated segments of the large T-antigen (T-ag) gene were found in the same 5 tumors. Analysis of the DNA sequences encoding the T-ag carboxy terminus revealed sequence variation among the tumors, as observed previously in viral DNA associated with human brain tumors. There does not appear to be a preferential association of a T-ag variable domain sequence with a given tumor type. No sequences from the regulatory region of human polyomaviruses JCV and BKV were detected in the bone tumors. We also noted less efficient recovery of SV40 DNA from tumor samples fixed in paraffin as compared to frozen tumors. Our results confirm the presence of SV40 DNA in human bone tumors and, based on the sequence variation observed for the carboxy terminus of the T-ag gene, suggest that there is not a specific SV40 strain associated with human osteosarcomas. Int. J. Cancer 72:791–800, 1997. © 1997 Wiley-Liss, Inc.     

EXPRESSION OF SV40 Tag AND FORMATION Tag-p53 AND Tag-Rb COMPLEXES IN CHINESE BRAIN TUMORS

Simian virus 40 (SV40), one type of polyomavirus, is able to transform different species including human normal cells to the neoplastic phenotype cell. The biological plausibility of SV40 as a tumorigenic agent has been extensively demonstrated. SV40 is tumorigenic in rodents and can immortalize human epithelial cell lines in vitro. It is also understood that SV40 large tumor antigen (Tag) interferes with p53 and Rb gene functions, and it may induce chromosomal instability. Furthermore, th…     

Expression of the simian virus 40 large tumor antigen (Tag) and formation of Tag-p53 and Tag-pRb complexes in human brain tumors

BACKGROUND: The presence of simian virus 40 (SV40) in human brain tumors remains a controversial issue. Even if SV40 does exist in brain tumors, the questions of whether it is associated with brain tumorigenesis and by what mechanisms are unknown. METHODS: SV40 large tumor antigen (Tag) was investigated by immunoprecipitation, silver staining, and Western blot analysis in 65 brain tumor cases and 8 cases of normal brain tissue. Tag-p53 and Tag-pRb complexes were screened by immunoprecipitation and Western blot analysis in 18 and 15 Tag positive tumor tissues, respectively. RESULTS: Tag was found in all 8 cases of ependymoma and 2 cases of choroid plexus papilloma, 90% of pituitary adenoma cases (9 of 10), 73% of astrocytoma cases (11 of 15), 70% of meningioma cases (7 of 10), 50% of glioblastoma multiforme cases (4 of 8), and 33% of medulloblastoma cases (2 of 6). Five oligodendroglioma cases, 1 pineocytoma case, and 8 cases of normal brain tissue were negative for Tag. The Tag-p53 complex was detected in all 18 Tag positive tumors tested and the Tag-pRb complex was detected in all 15 Tag positive tumors tested. CONCLUSIONS: SV40 Tag not only is expressed in brain tumors; it also can form specific complexes with tumor suppressors p53 and pRb. SV40 is correlated with brain tumorigenesis. The inactivation of p53 and pRb due to the formation of Tag-p53 and Tag-pRb complexes possibly is a significant mechanism in the etiopathogenesis of brain tumors.     

Simian-virus-40 footprints in human lymphoproliferative disorders of HIV− and HIV+ patients

SV40 sequences were investigated by PCR DNA amplification followed by filter hybridization in a series of human lymphoproliferative disorders obtained from human-immunodeficiency-virus (HIV)-seronegative and HIV-infected patients. Our PCR and filter-hybridization conditions enabled us to detect SV40 sequences in the range of 10⁻⁴ to 10⁻² genome equivalents per cell. In non-Hodgkin's lymphomas (NHL) from HIV⁻ patients, SV40 footprints were found in 11 out of 79 (13.9%) samples, while in NHL from HIV⁺ patients SV40 DNA sequences were detected in 2/16 (12.5%). In Hodgkin's disease (HD), SV40 sequences were found in 7/43 (16.3%) and 1/12 (8.3%) in HIV⁻ and HIV⁺ patients respectively. A slightly higher prevalence of SV40 footprints was observed in reactive lympho-adenopathies both in HIV⁻ (3/9, 33.3%) and in HIV⁺ (6/17, 35.3%) patients. Sequence analysis of 2 NHL and 2 HD DNA samples established that the amplified PCR products belong to the SV40 sequences. SV40 prevalence and load were similar in samples from HIV-seronegative and HIV-infected individuals, suggesting that SV40 probably does not undergo strong reactivation phenomena in the context of HIV-related immunosuppression. Moreover, the large T-antigen(Tag) expression was detected by immunohistochemistry in 5/18 SV40-DNA-positive samples analyzed; however, few tumor cells (<1%) in 3/5 samples displayed positivity for SV40 Tag, while this viral oncoprotein was revealed in several reactive histiocytes present in all 5 SV40-positive tissues. These results suggest that the lymphoid tissue could represent a reservoir for SV40 and may constitute the first step in understanding whether this DNA tumor polyomavirus has a role in the pathogenesis of human lymphoproliferative disorders. Int. J. Cancer 78:669–674, 1998. © 1998 Wiley-Liss, Inc.     

Association between SV40 and non-Hodgkin's lymphoma

Millions of people worldwide were inadvertently exposed to live simian virus 40 (SV40) between 1955 and 1963 through immunization with SV40-contaminated polio vaccines. Although the prevalence of SV40 infections in humans is not known, numerous studies suggest that SV40 is a pathogen resident in the human population today. SV40 is a potent DNA tumor virus that is known to induce primary brain cancers, bone cancers, mesotheliomas, and lymphomas in laboratory animals. SV40 oncogenesis is mediated by the viral large tumor antigen (T-ag), which inactivates the tumor suppressor proteins p53 and pRb. During the last decade, independent studies using different molecular biology techniques have shown the presence of SV40 DNA, T-ag, or other viral markers in primary human brain and bone cancers and malignant mesotheliomas. Evidence suggests that there may be geographic differences in the frequency of these virus-positive tumors. Recent large independent controlled studies have shown that SV40 T-ag DNA is significantly associated with human non-Hodgkin's lymphoma (NHL). In our study, we analyzed systemic NHL from 76 HIV-1-positive and 78 HIV-1-negative patients, and nonmalignant lymphoid samples from 79 HIV-1-positive and 107 HIV-1-negative patients without tumors; 54 colon and breast carcinoma samples served as cancer controls. We used polymerase chain reaction (PCR) followed by Southern blot hybridization and DNA sequence analysis to detect DNAs of polyomaviruses and herpesviruses. SV40-specific DNA sequences were detected in 64 (42%) of 154 NHL, none of 186 nonmalignant lymphoid samples, and none of 54 control cancers. For NHL from HIV-1-positive patients, 33% contained SV40 DNA and 39% Epstein Barr virus (EBV) DNA, whereas NHLs from HIV-1-negative patients were 50% positive for SV40 and 15% positive for EBV. Few tumors were positive for both SV40 and EBV. Human herpesvirus type 8 was not detected. SV40 sequences were found most frequently in diffuse large B cell and follicular-type lymphomas. We conclude that SV40 is significantly associated with some types of NHL and that lymphomas should be added to the types of human cancers associated with SV40.     

胶质瘤组织中SV40Tag Rb和IRS-1蛋白的表达及其与胶质瘤发生发展的关系

目的 探讨SV40Tag、Rb和IRS-1在胶质瘤发生发展过程中的关系和作用.方法 构建布有人脑胶质瘤和脑膜瘤临床标本为主体、配有实验性胶质瘤、正常人或鼠脑等相关组织等118个阵列的组织芯片,采用免疫组织化学和免疫荧光共聚焦技术检测SV40Tag、Rb和IRS-1的表达及SV40Tag与Rb、SV40Tag与IRS-1的联合表达.结果 SV40Tag、Rb和IRS-1在胶质瘤和脑膜瘤中均有表达,82例胶质瘤的阳性表达率分别为65.9%、64.6%和48.8%.正常人脑组织仅有Rb和IRS-1表达,而未见SV40Tag表达.SV40Tag和IRS-1的阳性表达率与病理分级呈正相关(P<0.05),Rb蛋白的阳性表达率与病理分级呈负相关(P<0.05).在82例胶质瘤中,SV40Tag与Rb、SV40Tag与IRS-1联合表达阳性率分别为51.2%和40.2%.结论 外源性SV40Tag随SV40病毒侵入机体,与Rb抑癌基因形成复合物使其抑癌功能丧失,同时诱导信号通路中重要成员IRS-1活化,从而促进细胞恶性变化,可能是脑胶质瘤发生发展的重要原因之一.     

SV40 BKV及JCV在人脑肿瘤中的表达

目的:探讨多瘤病毒SV40、BKV、JCV与人脑肿瘤发生之间的关系.方法:采用聚合酶链式反应(PCR)技术,对脑星形细胞瘤23例,少突胶质细胞瘤19例,室管膜瘤18例,脉络丛乳头状瘤12例,脑膜瘤11例及正常脑组织12例进行了三种病毒的检测.结果:SV40、BKV和JCV在脑肿瘤组织的阳性率分别为56.6%(47例)、53.0%(44例)和14.5%(12例);在正常脑组织中阳性率分别为8.3%(1例)、8.3%(1例)和16.7%(2例).SV40在脑肿瘤组织中阳性率显著高于正常脑组织(P＜0.01),所检测的五种脑肿瘤与正常组织相比具有显著性差异(P＜0.05);BKV在脑肿瘤组织中阳性率显著高于正常脑组织(P＜0.01),所检测的五种脑肿瘤与正常组织相比具有显著性差异(P＜0.05);SV40与BKV在脑肿瘤中的阳性率具有相关性(关联系数=0.56).JCV在肿瘤组织与正常组织间无显著性差异.结论:SV40及BKV参与脑肿瘤的发生.     

人脑肿瘤中SV40大T抗原与pRb形成特异性复合物

目的：探讨ＳＶ４０早期基因编码产物大Ｔ抗原表达及与抑癌蛋白ｐＲｂ的相互作用在人脑肿瘤发生发展中的意义。方法：采用免疫共沉淀ｅｓｔｅｒｎ印迹法检测４３例人脑肿瘤组织及５例正常人脑组织中Ｔａｇ的表达，并对１５例Ｔａｇ阳性瘤组织检测Ｔａｇ－ｐＲｂ复合物的存在。结果：Ｔａｇ在５例室膜瘤及２例脉络丛乳头状瘤中全部表达，垂体腺瘤，星形胶质细胞瘤，脑膜瘤，多形性胶质母细胞瘤及髓母细胞瘤均有Ｔａｇ的表达；     

Presence of simian virus 40 DNA sequences in diffuse large B-cell lymphomas in Tunisia correlates with aberrant promoter hypermethylation of multiple tumor suppressor genes

The simian virus SV40 (SV40), a potent DNA oncogenic polyomavirus, has been detected in several human tumors including lymphomas, mainly in diffuse large B-cell type (DLBCL). However, a causative role for this virus has not been convincingly established. Hypermethylation in promoter regions is a frequent process of silencing tumor suppressor genes (TSGs) in cancers, which may be induced by oncogenic viruses. In this study, we investigated the relationship between the presence of SV40 DNA sequences and the methylation status of 13 TSGs in 108 DLBCLs and 60 nontumoral samples from Tunisia. SV40 DNA presence was investigated by PCR assays targeting the large T-antigen, the regulatory and the VP1 regions. Hypermethylation was carried out by methylation-specific PCR. SV40 DNA was detected in 63/108 (56%) of DLBCL and in 4/60 (6%) of nontumoral samples. Hypermethylation frequencies for the tested TSGs were 74% for DAPK, 70% for CDH1, SHP1, and GSTP1, 58% for p16, 54% for APC, 50% for p14, 39% for p15, 19% for RB1, 15% for BLU, 3% for p53, and 0% for p300 and MGMT. No hypermethylation was observed in nontumoral samples. Hypermethylation of SHP1, DAPK, CDH1, GSTP1 and p16 genes were significantly higher in SV40-positive than in SV40-negative DLBCL samples (p values ranging from 0.0006 to <0.0001). Our findings showed a high prevalence of SV40 DNA in DLBCLs in Tunisia. The significant association of promoter hypermethylation of multiple TSGs with the presence of SV40 DNA in DLBCLs supports a functional effect of the virus in those lymphomas.     

SV40大T抗原在人脑肿瘤中的表达

目的　检测 Ｓ Ｖ４０ 早期区域基因编码产物大 Ｔ 抗原（ Ｔａｇ）在人脑肿瘤中的表达，探讨 Ｓ Ｖ４０ 与人脑肿瘤发生的病因学关系。方法　采用免疫共沉淀、银染色及 Ｗｅｓｔｅｒｎ印迹检测 ６５ 例人脑肿瘤组织、８ 例正常人脑组织及 ２ 株人脑胶质瘤细胞系中 Ｔａｇ 的表达。结果　 Ｔａｇ 在 ８ 例室管膜瘤、２ 例脉络丛乳头状瘤及 ２ 株人脑胶质瘤细胞系中全部表达；垂体腺瘤 Ｔａｇ 阳性率为 ９０％ （９／１０），星形胶质细胞瘤７３％ （１１／１５），脑 膜瘤 ７０％ （７／１０），多形性 胶质母细胞 瘤５０％ （４／８），髓母细胞瘤 ３３％ （２／６）；５ 例少枝胶质细胞瘤、１例松果体瘤及 ８ 例正常人脑组织无 Ｔａｇ 表达。结论　 Ｓ Ｖ４０感染与人脑肿瘤的发生有一定关系。     

Involvement of insulin-like growth factor-insulin receptor signal pathway in the transgenic mouse model of medulloblastoma

A transgenic mouse model expressing Simian virus 40 T-antigen (SV40Tag) under the control of a tetracycline system was generated. In this model, a cerebellar tumor was developed after doxycycline hydrochloride treatment. Real time-polymerase chain reaction and immunohistochemistry results indicated that the SV40Tag gene was expressed in the tumor. Pathological analysis showed that the tumor belonged to medulloblastoma. Further molecular characterization of the tumor demonstrated that the insulin-like growth factor (IGF) signaling pathway was activated. We also found that the SV40Tag could bind and translocate insulin receptor substrate 1 into the nucleus in primary cultured tumor cells. The interaction between the IGF pathway and SV40Tag may contribute to the process of malignant transformation in medulloblastoma. This transgenic animal model provides an important tool for studies on the signal pathways involved in the preneoplastic process in medulloblastoma and could help to identify therapeutic targets for brain tumors. ( Cancer Sci 2008; 99: 234–240)     

SV40 infection induces telomerase activity in human mesothelial cells

Mesotheliomas are malignant tumors of the pleural and peritoneal membranes which are often associated with asbestos exposure and with Simian virus 40 (SV40) infection. Telomerase activity is repressed in somatic cells and tissues but is activated in immortal and malignant cells. We evaluated telomerase activity in seven primary malignant mesothelioma biopsies and matched lung specimens and 20 mesothelioma cell lines and eight corresponding primary tumor cultures. All the tumor biopsies, and nearly all primary cell mesothelioma cultures and cell lines were telomerase positive. The findings in cell lines paralleled those observed in primary cultures in cases where paired samples were available. Next, we found that SV40, a DNA tumor virus present in approximately 50% of mesothelioma biopsies in the USA, induced telomerase activity in primary human mesothelial cells, but not in primary fibroblasts. Telomerase activity became detectable as early as 72 h following wild-type (strain 776) SV40 infection, and a clear DNA ladder was detectable 1 week after infection. The amount of telomerase activity increased during passage in cell culture and appeared to parallel increases in the cellular amounts of the SV40 large T-antigen. Thus, SV40 infection leads to telomerase activity before the infected mesothelial cells become transformed and immortalized. SV40 infection of human fibroblasts did not cause detectable telomerase activity. We also determined that the SV40 small t-antigen (tag) plays an important role in inducing telomerase activity because this activity was undetectable or minimal in mesothelial cells infected and/or transformed by SV40 tag mutants. Asbestos alone did not induce telomerase activity, and asbestos did not influence telomerase activity in mesothelial cells infected with SV40. Induction of telomerase activity by SV40 may be related to the very high rate of mesothelial cell immortalization that is characteristically associated with SV40 infection of mesothelial cells.     

人脑胶质组织中SV40大T抗原表达及p53形成特异性复合物

目的 探讨SV40早期区域基因编码产物大T抗原（Tag）表达及与抑癌蛋白p53的相互作用在人脑胶质瘤发生发展中的意义。方法 采用免疫组织化学方法检测89例人脑胶质瘤组织和11例正常人脑组织中Tag的表达,并对Tag表达阳性肿瘤组织进行免疫共沉淀和Western blot表达阳性33例（阳性率37．1％）,Tag表达水平与胶质瘤病理分级呈显著正相关（pearson列联系数＝0．72,P＜0．01）;33例Tag表达阳性瘤组织中均发现Tag表达全部阴性。结果 SV40感染与人脑胶质瘤病因学密切相关,Tag可能是SV40在胶质瘤发生发展中起作用的重要因素;Tag可能是SV40在胶质瘤发生发展中起作用的重要因素：Tag与p53可形成特异性复合物,Tag-p53特异性复合物的形成导致p53失活,可能是人脑胶质癌发生发展的一个重要机理。     

Association of SV40 with human tumors

In 1994, PCR and protein studies suggested that SV40 DNA sequences and proteins were present in 29/48 (60%) USA human mesothelioma samples. Sequence analysis confirmed that the sequences were homologous to SV40. One year later, SV40 was also found in 5/9 human mesotheliomas, and in 1996 SV40 was also reported to be present in 1/3 of the tumor specimens examined. These reports, in combination with an earlier study in 1992 which had detected SV40 in human brain tumors, raised concerns that SV40 was associated with certain types of human tumors, specifically mesothelioma, bone, and brain tumors. These findings raised concerns, because these tumor types are the same malignancies that had been observed in animals injected with SV40. However, a study in 1996 and a presentation made at the International Mesothelioma Interest Group, IMIG in 1997 failed to detect SV40 in mesotheliomas, suggesting the possibility that laboratory artifacts, such as PCR contamination, had caused the previous positive findings. In 1997, the FDA, the NIH, and the CDC organized an international conference in Bethesda to review the literature and to address the possibility that SV40 was present in, and was possibly the cause of, some human tumors. The results of that conference were reported the same year in a meeting review in Oncogene by Carbone and colleagues. Briefly, the consensus was that before accepting the possibility that SV40 was present in human tumors, a multi-laboratory study needed to be conducted. It was recommended that a blinded multi-laboratory study be directed by an independent scientist not previously associated with the controversial reports of SV40 in human specimens. It was also recommended that this study include laboratories that had reported positive findings as well as laboratories that had failed to detect SV40 in human specimens. Since 1997, about 30 independent reports have been published on this topic, including the multi-laboratory study. Evidence in favor and against a possible association of SV40 with human cancer was reviewed at an international consensus meeting at the University of Chicago on 20, 21 April 2001, entitled "Malignant Mesothelioma: Therapeutic Options and the Role of SV40, 2001". The main focus was the association of SV40 with mesothelioma and other human tumors. At the end of the meeting, a panel discussion, which included independent experts who had not published on this topic, critically reviewed the evidence presented at the meeting. The results of the meeting and of the final panel discussion are outlined below.     

Absence of SV40 in Austrian tumors correlates with low incidence of mesotheliomas

Between 1955 and 1963 millions of people were worldwide vaccinated with polio-vaccines that were contaminated with the simian virus 40 (SV40). This tumor-inducing virus has subsequently been detected in several human tumors. In Austria, polio mass vaccination started in winter 1961/62 with a presumably SV40-free British vaccine. Thus, we hypothesized that the Austrian population should be SV40-free. We used a polymerase chain reaction-based (PCR) method to search for SV40 sequences in DNA that was extracted from 14 giant cell tumors, ten osteosarcomas and eight mesotheliomas. SV40 was easily detected in two bone tumor DNAs from Italy, and one from the USA, and in one SV40 positive cell line. In parallel experiments all Austrian samples tested consistently negative. Our findings support the notion that: 1) polio vaccination is the main source for SV40 in human populations, 2) Austria was not exposed to SV40, and 3) its absence correlates with the low incidence of mesotheliomas in Austria.     

High incidence of bk virus large-T-antigen-coding sequences in normal human tissues and tumors of different histotypes

T-antigen (TAg) coding sequences specific for BK virus (BKV) were detected, by PCR amplification followed by Southern-blot hybridization, in a high percentage of human tumors and tumor-cell lines, as well as in normal tissues, by analysis of 189 specimens. Specifically, the BKV early region was detected in 85% of brain tumors and in all normal brain tissues, in 78% of osteosarcomas, in 38% of Ewing's tumors, in 40% of normal bone specimens and in 71% of normal peripheral blood cell samples. Wilms' tumor tissues used as a control were all negative for BKV sequences. RT-PCR analysis indicated that TAg coding sequences were expressed in specimens carrying BKV early region, ranging from 64% of the osteosarcomas to 100% of glioblastomas, Ewing's tumors, peripheral blood cells and normal bone. Moreover, DNA sequencing performed in 12 different positive samples revealed that the amplified PCR products are identical to the early-region sequence of wild-type BKV. The role of BKV TAg and its possible mechanism of action in human tumorigenesis are discussed. © 1995 Wiley-Liss, Inc.     

Absence of simian virus 40 in human brain tumors from northern India

Simian virus 40 (SV40), a monkey polyomavirus, was a contaminant of early poliovirus vaccines administered to millions of individuals in the 1950s and early 1960s. SV40 causes brain tumors in laboratory animals, and SV40 DNA sequences have been variably identified in human choroid plexus tumors and ependymomas. We studied the possible association between SV40 and human brain tumors in northern India, where humans have frequent contact with SV40-infected rhesus macaques. DNA from pathologic specimens from 33 ependymomas, 14 choroid plexus tumors and 18 control brain tissues (contused brain, brain metastases) was extracted and analyzed under masked conditions. We used real-time PCR to detect and quantify SV40 (T antigen) and human (GAPDH) DNA sequences. The SV40 PCR assay detected as few as 10 copies of SV40 DNA and had a linear range from 1 x 10(2) to 1 x 10(6) copies. SV40 DNA was detected in 1 specimen (an ependymoma). However, few SV40 DNA copies were detected in this sample (<10 copies, equivalent to <1 copy/350 cells, based on simultaneous GAPDH quantification), and SV40 was not detected when this sample was retested. Our findings do not support a role for SV40 in choroid plexus tumors or ependymomas from northern India.     

Simian virus 40 is present in human lymphomas and normal blood

Many independent studies have demonstrated Simian virus 40 (SV40) in normal and neoplastic human tissues. Clonal integration of virus in the DNA of several thyroid and bone tumors suggests a direct role for SV40 in some cancers. However, in most cases the role of SV40 remains unclear. This study determined the presence of SV40, by amplification followed by hybridization, in 266 normal and neoplastic blood and lymphoid samples. Amplification detected SV40 in 14% of non-autoimmune deficiency syndrome (AIDS) lymphomas, 28% of AIDS related lymphoma and 16% of peripheral blood lymphocytes from non-cancerous patients. No SV40 was detected in leukemia samples. Direct Southern blotting of SV40+ samples detected no virus, consistent with less than one viral genome in ten cells. Sequence analysis of SV40 in blood and lymphoid samples found sequences distinct from laboratory strains of SV40. The presence of limited quantities of SV40 in a small proportion of both normal and neoplastic tissues is suggestive of an adventitious presence with no apparent direct role in blood and lymphoid cancers.     

Characterization of the surface proteins of SV40-transformed mouse and human cells: absence of SV40-specific proteins

The proteins of a number of SV40- and spontaneously transformed mouse and human cell lines were compared in an effort to identify a surface protein which would correspond to the SV40 tumor-specific transplantation antigen (TSTA). Analysis of the one- and two-dimensional electrophoretic patterns of 35S-methionine-labelled total proteins and 125I-labelled surface proteins of several of these cell lines failed to reveal the presence of proteins specific to transformation by SV40. Antisera were prepared against SV40- and spontaneously transformed mouse cells in syngeneic mice. In serological assays, these antisera reacted with surface antigens common to both SV40- and spontaneously transformed mouse cell lines. Electrophoretic analysis of the 125I-surface-labelled proteins which these antisera immunoprecipitated from extracts of SV40- and spontaneously transformed mouse and human cells identified a set of common surface proteins with apparent molecular weights of 15, 46, 50, 72, 77, 105, 150 and 230kdal. No SV40-specific surface proteins were detected. Two of the transformed cell surface proteins (105 and 150kdal) were present as well in membrane fractions of 35S-methionine-labelled primary mouse kidney cultures. The proteins of the primary cultures could not be iodinated by lactoperoxidase suggesting that these proteins were present at a "cryptic" location at the surface of normal cells. We were not able to obtain serological or immunochemical evidence for the presence of SV40 large T-antigen at the surface of any of the SV40-transformed cell lines tested using either hamster anti-SV40 tumor sera, a rabbit antiserum against SDS-denatured gel-purified large T-antigen or antisera against SV40-transformed mouse cells. In conjunction with the report that large T-antigen released from disrupted SV40-transformed cells will bind to cell surfaces (Lange-Mutschler and Henning, 1982), we consider the possibility that the specific rejection of SV40-induced tumors by sensitized animals is the result of immunological reactions against both common transformation-related surface antigens and SV40 T-antigen from disrupted cells that has bound to the surface of other tumor cells.     

Induction of tumors in Syrian hamsters by a human renal papovavirus, RF strain.

Injection of RF virus (RFV), a papovavirus isolated from human urine, into newborn Syrian hamsters induced subcutaneous sarcomas in 50% of the recipients with 18- to 48-week latent periods. Transplantation of 2 X 10(6) primary RFV-induced tumor cells into weaning hamsters caused tumors in 100% of the recipients within 1-2 weeks. Continuous tissue culture cell lines were established from two primary tumors; one of these was transplantable. An in vitro-transformed continuous cell line (RF-194) obtained by infection of primary hamster embryo fibroblasts with RFV was transplantable in weaning hamsters. Neither infectious RFV nor virion antigens were detected in transformed cells. No RFV was recovered when transformed cells were fused with permissive, human embryo kidney cells by means of inactivated Sendai virus. Immunoperoxidase staining was used to show that all three RFV-transformed cell lines contained an intranuclear T-antigen closely similar to that of simian virus 40(SV40)-infected cells. Most hamsters (84%) with primary or transplanted RFV tumors responded with antibodies that reacted with RFV T-antigen and the T-antigen of SV40-infected cells. Likewise, hamster antisera against SV40 T-antigen cross-reacted with RFV T-antigen. Adsorption of RFV T-antisera with an excess of lyophilized SV40-transformed cells removed all detectable activity against SV40 T-antigen but left significant activity against RFV T-antigen. The reciprocal adsorption produced an antiserum spedicic for SV40 T-antigen. Thus human and simian papovavirus T-antigens were related but immunologically separable.