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.

Tissue-specific expression of SV40 in tumors associated with the Li-Fraumeni syndrome

Inactivation of wild-type p53 tumor suppressor function is the primary mechanism of tumor initiation in Li-Fraumeni syndrome (LFS) individuals with germline p53 mutations. Tumors derived from LFS patients frequently retain the normal p53 allele, suggesting that alternative mechanisms in addition to gene deletion must be involved in inactivating wild-type p53 protein. DNA tumor viruses, such as SV40, target p53 for inactivation through the action of viral oncoproteins. We studied the probands from two unrelated LFS families, each of whom presented with multiple malignant neoplasms. Patient 1 developed an embryonal rhabdomyosarcoma (RMS) and a choroid plexus carcinoma (CPC), while patient 2 developed a CPC and subsequently presented with both an osteosarcoma (OS) and renal cell carcinoma (RCC). We utilized DNA sequence analysis and immunohistochemistry to determine p53 gene status in the germline and tumors, as well as evidence for SV40 T-antigen oncoprotein expression. Each patient harbored a heterozygous germline p53 mutation at codons 175 and 273, respectively. In patient 1, the normal p53 gene was lost while the mutant p53 allele was reduced to homozygosity in the RMS. Both normal and mutant genes were maintained in the CPC. In patient 2, normal and mutant p53 alleles were retained in both the CPC and RCC. Both specific PCR and immunostaining detected SV40 T-antigen in both CPCs and the RCC. In addition to chromosomal alterations, epigenetic mechanisms may disrupt p53 function during tumorigenesis. In two LFS patients, we found SV40 DNA sequences and viral T-antigen expression that could account for inactivation of the normal p53 protein. Inactivation of p53 or other tumor suppressors by viral proteins may contribute to tumor formation in specific tissues of genetically susceptible individuals.

Simian virus 40 is present in most United States human mesotheliomas, but it is rarely present in non-Hodgkin's lymphoma

Simian virus 40 (SV40) causes mesotheliomas, osteosarcomas, ependymomas, choroid plexus tumors, and lymphomas in hamsters. In humans, SV40 has been detected in tumors of the first four types. Using the polymerase chain reaction (PCR), we tested 29 non-Hodgkin's lymphomas (intermediate and high-grade), 25 posttransplant lymphoproliferative disorders, and 5 AIDS lymphomas for SV40 DNA. PCR analysis revealed that 3 of 29 lymphomas, 6 of 25 posttransplant lymphoproliferative disorders, and 2 of 5 AIDS lymphomas contained SV40 sequences corresponding to the retinoblastoma (RB)-pocket binding domain of SV40 tumor antigen (Tag). However, among positive samples, only one posttransplant lymphoproliferative disorder and one AIDS lymphoma contained the SV40 regulatory region, which suggest a higher viral load in these patients. In parallel experiments, 8 of 12 mesotheliomas tested positive for SV40 for both the RB-pocket binding domain of Tag and the SV40 regulatory region. These data confirm the presence of SV40 in most United States mesotheliomas and indicate that in human non-Hodgkin's lymphomas, the prevalence of SV40 is low.

Simian virus 40 DNA sequences in human brain and bone tumours

This report reviews recent observations regarding the association of simian virus 40 (SV40) DNA sequences with brain and bone tumours of childhood [1-3]. Our initial investigation was suggested by the tumorigenicity of SV40 in animals, and the transgenic mouse expression of SV40 large T-antigen in which all animals developed choroid plexus (CP) tumours. Polymerase chain reaction (PCR) analysis and DNA sequencing demonstrated SV40-like DNA sequences, amplified from the "Rb-pocket" binding domain of the viral large T-antigen, in 10/20 CP and 10/11 ependymoma tumours of children. The PCR analysis was subsequently extended to three additional regions of the viral genome: the carboxy-terminal region of large T-antigen, the viral enhancer/origin, and the VP1 gene. All amplified products were related to SV40 sequences. Furthermore, because one individual in the original brain tumour study was a member of a Li-Fraumeni kindred, 151 DNA samples from such families were analysed. Only 18 were positive for viral sequences and 11 of these were isolated from individuals with osteosarcomas. This observation led to a further analysis of DNA from bone tumours, in which 54/160 samples contained SV40-like sequences. These studies associate SV40-like sequences with human CP, ependymoma, and bone tumours. A causal relationship to human oncogenesis remains a subject for further study.

Detection of authentic SV40 DNA sequences in human brain and bone tumours

This report summarizes our follow-up studies of SV40 DNA sequences in human brain tumors of early childhood and our confirmation of the presence of SV40 DNA in human osteosarcomas. We examined brain tumors and osteosarcoma samples by the polymerase chain reaction (PCR) using primers from four separated regions of the SV40 genome. Sequence analysis confirmed that authentic SV40 DNA was present. The regulatory region of each tumor-associated viral DNA was of archetypal length (non-duplicated enhancer); sequence variation was noted at the extreme C-terminus of the large T-antigen (T-ag) genes. Infectious SV40 was recovered from one brain tumor. We sequenced the entire early genomic region from three human isolates of SV40 and two laboratory strains originally recovered from monkeys. The predicted amino acid sequence of the large T-ags showed remarkable sequence conservation among isolates, except for a small variable region identified at the C-terminus of the protein. There were no human-isolate-specific changes detected that could serve to distinguish a human variant of SV40 nor were any tumor-type-specific viral markers observed. Based on these data, we conclude that authentic SV40 is associated with some human brain and bone tumors and that multiple SV40 strains can infect humans.

Sequence analyses of human tumor-associated SV40 DNAs and SV40 viral isolates from monkeys and humans

SV40 DNA has been found associated with several types of human tumors. We now report a sequence comparison of SV40 DNAs from pediatric brain tumors and from osteosarcomas with viral isolates from monkeys and from humans. We analyzed the entire genomic sequences of five isolates, Baylor and VA45-54 strains from monkeys and SVCPC, SVMEN, and SVPML-1 recovered from humans, and compared them to the reference virus SV40-776. The viral sequences were highly conserved, but isolates could be distinguished by variations in the structure of the viral regulatory region and in the nucleotide sequence of the variable domain at the C-terminus of the large T-antigen gene. We conclude that multiple strains of SV40 exist that can be identified on the basis of sequences in these regions of the viral genome. The isolates were more similar to each other and to the Baylor strain than to the reference strain SV40-776. Human isolates SVCPC and SVMEN were found to be identical. The DNAs present in some human brain and bone tumors were authentic SV40 sequences. Many of the C-terminal T-ag sequences associated with human tumors were unique, but some sequences were shared by independent sources. There was no compelling evidence for human-specific strains of SV40 or for tumor type-specific associations, suggesting that SV40 has a relatively broad host range. The source of the viral DNA found in human tumors remains unknown.

The oncogenic potential of eleven avian adenovirus strains

Oncogenic potentials of 11 strains of avian adenovirus representing 10 serotypes were investigated in 22 litters of 1-day-old Syrian hamsters (Mesocricetus auratus). Hamsters were inoculated via two routes: subcutaneous dose of 0.12 ml and intracerebral dose of 0.02 ml. Six strains, Indiana-C (Ind-C), chicken embryo lethal orphan (CELO), Stein, 75-1A, B-3, and A-2, induced fibrosarcomas subcutaneously at the inoculation site. Hamsters inoculated intracerebrally with Ind-C, CELO, Stein, B-3, and A-2 developed carcinomas of the choroid plexus. Strain 75-1A virus produced tumors on subcutaneous inoculation but failed to produce tumors on intracerebral inoculation. The Tipton, J-2, T-8, C-2B, and X-11 strains did not produce tumors in hamsters. Uninoculated control hamsters did not develop tumors.

Natural simian virus 40 strains are present in human choroid plexus and ependymoma tumors

Simian virus 40 (SV40) sequences for large tumor antigen (T-ag) were recently detected in a significant fraction of certain human brain tumors of early childhood (Bergsagel et al., N. Engl. J. Med. 326, 988-993, 1992). In the current study, we sought to determine whether authentic SV40 was present in the choroid plexus and ependymoma tumors previously examined. Polymerase chain reaction and DNA sequence analysis revealed authentic SV40 regulatory region and major capsid (VP1) sequences in 14 of 17 tumors tested. Only one 72-basepair element was detected in the SV40 enhancer region of positive tumor samples, an arrangement designated as "archetypal." The C terminus of the T-ag gene was detected in the same 14 tumors and was sequenced from 5 tumors; some nucleotide changes were found that would result in amino acid changes in T-ag. Infectious SV40 was isolated from one sample after lipofection of tumor DNA into monkey kidney cells. Sequence analysis of the rescued virus SVCPC revealed (i) an archetypal regulatory region, (ii) nucleotide changes in the C terminus of the T-ag gene that distinguished it from SV40 laboratory strains 776 and SV40-B2 and from human isolate SVPML-1, and (iii) identity with previous human brain tumor isolate SVMEN in the three genomic regions sequenced. No human-isolate-specific distinguishing features were detected among the viral sequences analyzed. Thus, authentic SV40 is present in humans and associated with two tumor types known to be induced experimentally by the virus.