Tissue specificity of L-pyruvate kinase transgenes results from the combinatorial effect of proximal promoter and distal activator regions

The L-type pyruvate kinase (L-PK) gene is regulated by diet and hormones and expressed at high levels in the hepatocytes, enterocytes, and proximal tubular cells of the kidney and at low levels in the endocrine pancreatic cells. Two regulatory regions have been shown to be important in transgenic mice to confer on a reporter gene a similar tissue-specific and diet-responsive expression: a proximal promoter fragment, with binding sites for the tissue-specific hepatocyte nuclear factors 1 and 4, and presence of the glucose-response element (GIRE) and a distal activator corresponding to a liver-specific hypersensitive site at -3000 bp with respect to the cap site. Although the proximal promoter is able to confer by itself tissue-specific expression on a reporter gene, its activity in vivo is strongly stimulated by the distal activator. To determine the possible role of the distal region on diet responsiveness and tissue specificity of the L-PK gene expression, we have created lines of transgenic mice in which the gene for SV40 T antigen (Tag) was directed by composite regulatory sequences consisting of the L-PK promoter and different enhancers: either the SV40 early enhancer (SV) or the H enhancer of the aldolase A gene (H). The induction of the composite H-PK/Tag and SV-PK/Tag transgenes by a carbohydrate-rich diet in the liver was similar to that of the endogenous L-PK gene. This suggests that in fasted mice the L-PK promoter, and especially the GIRE, is able to silence the activating influence of a strong viral enhancer such as the SV40 enhancer. The H-PK/Tag mice expressed the transgene similarly to the endogenous gene, except in the pancreas, where expression was practically undetectable. Consistently, whereas L-PK/Tag mice develop insulinomas, H-PK/Tag mice develop only hepatomas. In contrast, the transgene expression was partly aberrant in SV-PK/Tag mice. In addition to a normal activation of the transgene in the liver, a strong expression was also detected in the kidney medulla, whereas the transgene was practically silent in enterocytes. Finally, the effect of the distal region (-2070 to -3200) on an ubiquitous promoter was tested by ligating the distal L-PK gene fragment in front of a thymidine kinase/CAT transgene. Such a transgene was constantly expressed in the pancreas and, strikingly, in the brain. It appears, therefore, that the L-PK distal activator exhibits, by itself, a certain neuropancreatic specificity required in combination with the proximal promoter for L-PK gene expression in pancreas endocrine cells.

Growth Properties of Neural Cell Lines Immortalized with the Tsa58 Allele of Sv40 Large T Antigen

In vitro growth properties of three CNS-derived cell lines were compared under a variety of culture conditions. The M213-20 and J30a cell lines were each derived from embryonic CNS culture with the temperature-sensitive (ts) allele of SV40 large T antigen, tsA58, while the A7 cell line was immortalized using wild-type SV40 large T antigen. Cells immortalized with tsA58 SV40 large T proliferate at the permissive temperature, 33° C, while growth is expected to be suppressed at the nonpermissive temperature, 39.5°C. Both the M213-20 and J30a cell lines were capable of proliferating at 39.5°C continuously for up to 6 mo. All three cell lines showed no appreciable differences in growth rates related to temperature over a 7-day period in either serum-containing or defined serum-free media. The percentage of cells in S-phase of the cell cycle did not decrease or was elevated at 39.5°C for all three cell lines. After 3 wk at 39.5°C, the three cell lines also showed positive immunostaining using two monoclonal antibodies reacting with different epitopes of SV40 large T antigen. Double strand DNA sequence analyses of a 300 base pair (bp) fragment of the large T gene from each cell line, which included the ts locus, revealed mutations in both the J30a and M213-20 cell lines. The J30a cell line ts mutation had reverted to wild type, and two additional loci with bp substitutions with predicted amino acid changes were also found. While the ts mutation of the M213-20 cells was retained, an additional bp substitution with a predicted amino acid change was found. The A7 cell line sequence was identical to the reference wild-type sequence. These findings suggest that (a) nucleic acid sequences in the temperature-sensitive region of the tsA58 allele of SV40 large T are not necessarily stable, and (b) temperature sensitivity of cell lines immortalized with tsA58 is not necessarily retained.

Use of the SYBR Green dye for measuring helicase activity

Here we describe a non-radioactive assay that exploits the fluorescent dye SYBR Green to measure the helicase enzyme activity. SYBR Green I emits fluorescence upon intercalation with double-stranded DNA or RNA. The fluorescence is lost proportionally as the nucleic acid is converted to single strands by a helicase, and this decrease in fluorescence intensity can be used to measure the activity of the helicase enzyme. The reaction was prepared by mixing a double-stranded substrate with the helicase enzyme, buffer, ATP and SYBR Green I. After completion, the reaction was terminated by EDTA and fluorescence was measured. Using this technique, a linear increase in substrate release was observed with increasing time and helicase concentrations. The assay described here is speedy, efficient and economical; it holds promise for use in large-scale screening of drugs that target helicases.

High Prevalence of SV40 Infection in Patients with Nodal Non-Hodgkin's Lymphoma But Not Acute Leukemia Independent of Contaminated Polio Vaccines in Taiwan

Recent studies have linked simian virus 40 (SV40) to non-Hodgkin's lymphoma (NHL), especially in countries in which people were exposed to contaminated polio vaccines prior to 1963. In Taiwan, nearly all children were not exposed to contaminated polio vaccine during this period; the relationship between SV40 infection and hematological malignancies is unclear and deserves to be studied. Using PCR amplification of SV40 large T antigen DNA, confirmed by Southern blot hybridization and sequence analysis, 91 frozen lymph nodes from NHL patients were examined. Thirteen (14.3 percent) showed positive for SV40. All other test samples, including diagnostic bone marrow from patients with acute leukemia, peripheral blood from 10 relatives of SV40 positive-patients and 91 age-matched normal volunteers, and 5 reactive hyperplastic lymphoid tissues, showed negative. These results may reflect that human-to-human transmission of SV40 is independent of contaminated polio vaccines; and SV40 is possibly associated with the development of NHL in Taiwan (p = 0.0001). Prospective studies are needed to determine the prevalence of SV40 infections in our and other human populations and to explore the means of transmission of the virus.

A novel mechanism of late gene silencing drives SV40 transformation of human mesothelial cells

Suppression of the late gene expression, usually by integration of the viral DNA into the host genome, is a critical step in DNA tumor virus carcinogenesis. SV40 induces high rates of transformation in infected primary human mesothelial cells in tissue culture, leading to the formation of immortal cell lines (SV40-transformed human mesothelial cell lines, S-HML). The studies described here were designed to elucidate the unusual susceptibility of primary human mesothelial cells to SV40 carcinogenesis. We found that S-HML contained wild-type, mostly episomal SV40 DNA. In these cells, the early genes that code for the viral oncogenes are expressed; at the same time, the synthesis of the late genes, capsid proteins, is suppressed and S-HML are not lysed. Late gene suppression is achieved through the production of antisense RNA molecules. These antisense RNA molecules originate in the early region of the SV40 circular chromosome and proceed in antisense orientation into the late gene region, leading to the formation of highly unstable double-strand RNA, which is rapidly degraded. Our results reveal a novel biological mechanism responsible for the suppression of late viral gene products, an important step in viral carcinogenesis in humans.

Characterization of neural cell lines derived from SV40 large T-induced primitive neuroectodermal tumors

We recently reported intriguing properties of neural tumors generated by retrovirus-mediated transfer of the SV40 large T antigen into fetal rat brain transplants. Histopathologically, these neoplasms displayed characteristic features of primitive neuroectodermal tumors (PNET) and exhibited a striking potential for migration into the host brain. In the present study, four cell lines were derived from these PNETs and characterized. Two lines with an immature phenotype expressed the embryonal form of the neural cell adhesion molecule and nestin. They showed spheroid formation and delicate cell processes. The remaining cell lines had a flat, epitheloid appearance and were immunoreactive for synaptophysin, neurofilament proteins and glial fibrillary acidic protein. These cells constitute valuable tools to study the cellular origin(s) and molecular basis of PNETs, differentiation of neural progenitors and tumor cell migration in the brain.

Generation and characterization of islet cell tumor in pTet-on/pTRE-SV40Tag double-transgenic mice model

A line of double-transgenic mice that develop neoplasms arising primarily in the pancreas was established. In these mice, the oncogene SV40 T antigen (Tag) was detected in the pancreas with and without the control of Tet-on system. The transgenic mice that developed pancreatic tumors as early as 20 weeks of age showed hypoglycemia on a blood glucose test. Pathological and immunohistochemical characterizations demonstrated that the tumors belonged to neuroendocrine neoplasms arising from pancreatic islets. A change in IGFs/IGF-1R signaling pathway was detected using real-time PCR analysis. A potential association between the IGFs/IGF-1R system and SV40Tag was studied to further explain the cancerogenesis of the double-transgenic mice by Western blot analysis and immunoprecipitation experiments. The results suggest that a Tag transgenic mice model could be used to study the molecular mechanism of the tumorigenesis of islets.

Oncogenic T-antigen of JC virus is present frequently in human gastric cancers

BACKGROUND

JC virus (JCV) is a polyomavirus that commonly infects humans and is the causative agent of progressive multifocal leukoencephalopathy in immune-compromised patients. An association between JCV and human cancers long has been suspected, because this virus induces brain tumors in several animal models. The oncogenic potential of JCV is mediated by a transforming protein, the T-antigen (T-Ag), which is a multifunctional protein that transforms cells through interactions with various growth-regulatory genes, including p53 and pRb, and by stabilizing beta-catenin. Previously, the laboratory at the authors' institution demonstrated that JCV is present frequently in the human gastrointestinal tract and may play a role in colorectal carcinogenesis. However, to date, no studies have determined whether JCV sequences are present specifically in gastric cancers. The current study was designed to investigate whether JCV sequences and expression are found in human gastric cancers.

METHODS

DNA was extracted from 23 paraffin embedded and 14 frozen gastric cancer specimens. For the detection of JCV gene sequences, polymerase chain reaction amplifications were performed using gene-specific primers for T-Ag, VP-1 (a JCV capsid gene), and the viral regulatory region (or transcriptional control region). Immunohistochemical staining was performed with an anti-T-Ag monoclonal antibody to detect protein expression.

RESULTS

Twenty-one of 37 gastric cancers (57%) harbored JCV T-Ag sequences, and 13 of 37 gastric cancers (30%) contained VP-1 sequences. T-Ag sequences also were found in adjacent nonneoplastic mucosa. In addition, JCV regulatory region sequences were present frequently in gastric cancers and adjacent nonneoplastic mucosa. T-Ag protein expression was found in 9 of 23 gastric cancers (39%), whereas no expression was observed in any of the nonneoplastic tissues.

CONCLUSIONS

To the authors' knowledge, this is the first demonstration of the presence of JCV T-Ag expression in human gastric cancers. These findings suggest a possible role for this polyomavirus in gastric carcinogenesis.

Renal transplant patient with polyoma virus bladder infection and subsequent polyoma virus nephropathy

Polyoma virus nephropathy (PVN) is a significant cause of renal allograft dysfunction in transplant patients. A 58-year-old male received a cadaveric renal transplant and 12 weeks later presented with fever, diarrhea, and dysuria. He was diagnosed with a polyoma virus infection of the bladder by a transurethral bladder biopsy. One year post-transplant, he presented with renal allograft dysfunction and was diagnosed by biopsy with PVN of the non-native kidney. The diagnosis of a polyoma virus infection was confirmed by immunoreactivity to the polyoma T-antigen. We suggest that polyoma virus infection of the bladder be included in the differential diagnosis of urinary dysfunction in post-transplant patients, as such infections might be an under-recognized comorbidity in individuals with PVN.

Generation and characterization of a transgenic mouse model for pancreatic cancer

AIM: To generate a SV40Tag transgenic tumor animal model and to study the mechanism underlying tumorigenesis.

METHODS: A mammary gland expression vector containing SV40Tag DNA was generated. Transgene fragments were microinjeted into fertilized eggs of FVB mice. The genetically manipulated embryos were transferred into the oviducts of pseudo-pregnant female mice. PCR and Northern blot analysis were used for genotype analysis of F1 and F2 mice. Transgene expression was detected by RT-PCR and immunohistochemistry.

RESULTS: SV40Tag gene was detected in two lines of transgenic mice. One of them delivered the transgene to F1 and a tumor was found in the pancreas of these mice. RT-PCR and immunohistochemistry showed that SV40Tag gene was expressed in the tumor. Pathological characterization of the transgenic mice demonstrated that the tumor belonged to pancreatic cystic neoplasm.

CONCLUSION: SV40Tag transgenic mouse model can be successfully established. The transgenic mice develop a pancreatic tumor, which can be used for investigation of the molecular mechanism of tumorigenesis in vivo.

Lymphoproliferative disorders in Costa Rica and simian virus 40

BACKGROUND AND OBJECTIVES

Simian virus 40 (SV40) is an oncogenic DNA virus implicated in some human malignancies, including lymphomas. In the present masked case-control study, we investigated the prevalence of SV40 sequences and the expression of the viral oncoprotein, large tumor antigen (T-ag), in lymphomas and control specimens from patients negative for the human immunodeficiency virus in Costa Rica.

DESIGN AND METHODS

Coded specimens were anlyzed by polymerase chain reaction for SV40 and Epstein-Barr virus (EBV). SV40 sequences were confirmed by Southern blot and DNA sequence analysis. Immunohistochemistry was used to detect the expression of SV40 T-ag in coded samples and to immunophenotype the lymphomas.

RESULTS

When samples were decoded, SV40 DNA sequences were detected significantly more often in lymphomas than in control samples (30/125, 24% vs. 0/91, 0%; p=0.001). SV40 DNA was detected in 26% and 10% of non-Hodgkin's and Hodgkin's lymphomas, respectively. EBV DNA was detected in 10% of lymphomas and 33% of control specimens. None of the lymphomas was positive for both SV40 and EBV. Expression of SV40 T-ag was detected in 64% of B-cell lymphomas that contained T-ag DNA sequences and in none of the samples negative for viral DNA. Not all cells in a positive tumor expressed T-ag and the reactions were relatively low intensity. A germinal center B-cell-like profile was frequently associated with SV40-positive lymphomas. Of note, 20% of patients with SV40-related lymphomas were born in the 1970s and 1980s.

INTERPRETATION AND CONCLUSIONS

These results indicate that SV40 is significantly associated with some B-cell neoplasms in Costa Rica today.

Immunodetection of SV40 large T antigen in human central nervous system tumours

BACKGROUND/AIMS

DNA sequences from Simian virus 40 (SV40) have been previously isolated from various human tumours of the central nervous system (CNS). This study aimed to investigate a series of tumours of the CNS for the expression of the SV40 large T antigen (Tag), which is an oncogenic protein of the virus.

METHODS

A French series of 82 CNS tumours was investigated for Tag expression using a monoclonal antibody and immunohistochemistry. A Tag positive hepatocellular carcinoma cell line from transgenic mice and a kidney biopsy from a patient infected by SV40 were used as positive controls.

RESULTS

None of the tumours (20 ependymomas, 20 glioblastomas, 12 oligodendrogliomas, three plexus choroid adenomas, two plexus choroid carcinomas, 15 meningiomas, and 10 medulloblastomas) contained SV40 Tag positive cells.

CONCLUSIONS

The lack of SV40 Tag in 82 CNS tumours of various types is at variance with previous studies from different countries, and suggests that the virus may not be an important factor in CNS tumorigenesis, at least in French cases.

A steroidogenic cell line with differentiation potential from mouse granulosa cells, transfected with Ad4BP and SV40 large T antigen genes

Several steroidogenic cell lines of granulosa cells (GC) have been used to elucidate differentiation mechanisms of GC during folliculogenesis. These cell lines, however, are of limited usefulness since they have lost some of their differentiation potential. The transcription factor adrenal-4 binding protein (Ad4BP), also known as steroidogenic factor-1 or NR5A1, is essential for the expression of all P-450 steroidogenic enzymes. By transfection with the Ad4BP gene together with SV40 DNA, we have generated several steroidogenic cell lines. One selective clone, named 4B2, retained its steroidogenic potential and was therefore analyzed in depth. This cell line responded to 8-Br-cAMP by displaying differentiation characteristics similar to those occurring in the differentiation process of primary cultured GC, including enhanced progesterone secretion, a cell shape change from a fibroblastic to epithelioid conformation, elongated mitochondria, increased gap junction formation and inhibition of cell proliferation. Prostaglandin E2 (PGE2), an intraovarian regulator of GC, stimulated cAMP production, and this eicosanoid, like 8-Br-cAMP, induced differentiation properties with the exception of cell conformation in 4B2 cells. These results suggest that expression of Ad4BP may provide the basis for a repertoire of cAMP-sensitive differentiation properties, including morphological alterations and growth inhibition. Thus, the 4B2 cell line may serve as a tool for elucidation of differentiation mechanisms that are under the control of Ad4BP.

Epithelio-mesenchymal transition in a neoplastic ovarian epithelial hybrid cell line

A hybrid cell line, IOSE-Ov29, was created through fusion of cells from the human ovarian adenocarcinoma line OVCAR3 and the non-tumorigenic SV40 Tag-transfected human ovarian surface epithelial line IOSE-29. OVCAR3 cells exhibit a differentiated epithelial phenotype, whereas line IOSE-29 expresses mesenchymal characteristics that were acquired in culture by epithelio-mesenchymal transition. Microsatellite analysis, comparative genomic hybridization (CGH), and MFISH showed the genotype of the IOSE-Ov29 cells to contain components of both parent cell lines, but to be predominantly OVCAR3 derived. IOSE-Ov29 resembled OVCAR3 and differed from IOSE-29 as shown by its unlimited life span, tumorigenicity, epithelial morphology, keratin, occludin, E-cadherin and CA125 expression, increased expression of kinases of the PI3K pathway, and loss of cGMP-dependent protein kinase expression. IOSE-29-derived properties included SV40 Tag expression, growth inhibition by activin, collagen type III secretion, increased adhesion and spreading on tissue culture plastic, and increased growth rate. Proliferation of all three lines was stimulated by FSH and ATP and inhibited by GnRH I and GnRH II. Interestingly, IOSE-Ov29 was more anchorage independent than either parent line and was the only line that invaded Matrigel in Boyden chambers and formed invasive branches in collagen gels. The results indicate that IOSE-Ov29 is an IOSE-29/OVCAR3 hybrid, which differs from both parent lines genetically and phenotypically. Unexpectedly, fusion with the non-tumorigenic IOSE-29 cells enhanced malignancy-associated characteristics of OVCAR3, presumably as a result of the expression of IOSE-29-derived mesenchymal properties that are usually acquired by carcinoma cells through epithelio-mesenchymal transition during metastatic progression.

Regulation of CNS glial phenotypes in N20.1 cells

The N20.1 oligodendroglial cell line, immortalized with SV40 T antigen, simultaneously expresses oligodendroglial markers and glial fibrillary acidic protein (GFAP), an astroglial marker. This study examines the plasticity of N20.1 cells with regard to GFAP expression, and its relationship to expression of SV40 T antigen, p53, and a novel nuclear antigen detected by the A007 monoclonal antibody. Marked changes occur in GFAP levels and cell morphology when N20.1 cells are switched from the permissive temperature (34 degrees C) to the non-permissive temperature (39 degrees C), and with cyclic AMP elevation at 39 degrees C. At 34 degrees C, levels of GFAP are high; when cells are switched to 39 degrees C, GFAP levels decrease significantly, then increase slightly when forskolin is added. At both temperatures, the cells display feathery GFAP immunostaining. When forskolin is added at 39 degrees C, however, cells display bright fibrous GFAP staining in elongated processes. The changes in GFAP were compared to changes in T antigen and p53. As expected, the decrease in T antigen at 39 degrees C was accompanied by movement of p53 from the nucleus to cytoplasm. Total p53 levels did not change, however, and forskolin did not alter the respective distribution or levels of p53 at either temperature. At both temperatures, the cell bodies and processes show internal expression of sulfatide, as demonstrated with the O4, Sulph I, and A007 antibodies. We show, for the first time, abundant nuclear immunoreactivity with the A007 monoclonal antibody in the N20.1 cells. This nuclear reactivity is seen at 34 degrees C, but not at 39 degrees C, similar to p53, and is not detected with the other sulfatide antibodies. Double-label immunostaining shows that the nuclear A007 immunoreactivity is co-localized in nuclear structures with T antigen and p53 at 34 degrees C, but is not found in every nucleus containing these antigens. We conclude that regulation of GFAP expression and morphology in N20.1 cells is dependent on a combination of T antigen expression and level of cAMP and may be related to regulation of p53 and the A007 nuclear antigen.

Age-dependent histopathological findings in the prostate of probasin/SV40 T antigen transgenic rats: lack of influence of carcinogen or testosterone treatment

Sequential changes in the phenotype of prostatic lesions and the impact of additional carcinogen treatment or castration on development and progression of prostate cancers were examined in probasin/simian virus 40 (SV40) T antigen transgenic (TG) rats. Non-invasive prostate adenocarcinomas were evident in all lobes at 15 weeks of age. Invasive tumors were limited to the anterior lobe at this time point and were found in all lobes in an age-dependent manner thereafter. No metastasis was apparent at any age. Additional carcinogen treatment or castration did not enhance progression or generate selective growth of hormone-independent prostate cancer cells. These results suggest that our TG rats are suitable for clarification of mechanisms in early stages of prostate carcinogenesis, that is, from prostatic intraepithelial neoplasia (PIN) to non-invasive and then invasive lesions.

Immortalisation of ovarian granulosa and Theca cells of the marmoset monkey Calllithrix jacchus

In view of the increasing need for laboratory primates in biomedical research it is desirable to develop appropriate primate-specific cell culture models that could prevent or significantly reduce the increasing use of primary cultures and experiments with living animals. Follicular granulosa and theca cells are essential for the control of hormone-dependent processes such as the ovarian cycle and pregnancy, but also for the occurrence of hormone-dependent diseases. For this reason it is of great interest to know more about control mechanisms existing in these follicular cell types and the effect of pharmacological or toxicological agents on them. An immortalisation protocol for the two ovarian cell types of the marmoset monkey (Callithrix jacchus) has been developed. All cell lines established so far were examined with regard to the maintenance of known, tissue-specific features (e.g. hormone responsiveness and enzyme expression). The results obtained indicate that it is worth while cloning and characterising the cell lines in more detail so that they could be used after an adequate validation as a defined test system both for basic research as well as for pharmacological or toxicological screening.

Continuous porcine cell lines developed from alveolar macrophages: partial characterization and virus susceptibility

Porcine monomyeloid cell lines were established following transfection of primary porcine alveolar macrophage cultures with plasmid pSV3neo, carrying genes for neomycin resistance and SV40 large T antigen. The parental clone 3D4 exhibited a relatively rapid doubling time (25.5 h), high plating efficiency and mixed phenotype with respect to growth on a solid support. Single cell cloning of the 3D4 parent resulted in establishment of several cell lines; three of them designated 3D4/2, 3D4/21 and 3D4/31 were selected for further characterization. All three clones supported the replication of vesicular stomatitis virus (VSV), pseudorabies virus (PRV), classical swine fever virus (CSFV), swine vesicular disease virus (SVDV), swine poxvirus, African swine fever virus (ASFV), herpes simplex virus (HSV), parainfluenza virus, bovine adenovirus (BAV), vaccinia virus (VV), and porcine adenovirus (PAV). Under the conditions tested the cells did not support replication of porcine reproductive and respiratory syndrome virus (PRRSV). The swine myeloid character was confirmed for all three clones by fluorescence activated cell scanning (FACS) analysis using monoclonal antibodies 74-22-15 and DH59B, which recognize the pan-myeloid antigen cluster SWC3a. A subpopulation of each cell line was positive for nonspecific esterase activity and phagocytic activity to varying degrees depending on the media formulation. Cells from all three lines exhibited anchorage dependent growth when maintained in RPMI 1640 medium supplemented with 5-15% fetal bovine serum (FBS) and nonessential amino acids. Propagation in commercially formulated serum free media resulted in colony formation and growth in suspension. The addition of dimethyl sulfoxide (DMSO) or phorbol 12-myristate 13-acetate (PMA) to serum free media restored cell attachment. DMSO was also able to induce expression of CD14 monocyte marker in the 3D4/31 cell line maintained in FBS containing medium, as determined by FACS with monoclonal antibody CAM36A. Supplementation of RPMI medium with 10% porcine serum upregulated the expression of CD14 and induced expression of porcine macrophage markers recognized by antibodies 2B10 and 2G6 (Vet. Immunol. Immunopathol. 74 (2000) 163) in all three cell lines. The porcine myelomonocytic cell lines obtained may have a wide variety of applications in porcine virology and immunology.

Medulloblastomas and primitive neuroectodermal tumors rarely contain polyomavirus DNA sequences

To address the hypothesis that medulloblastoma or supratentorial primitive neuroectodermal tumor (sPNET) can arise through infection by polyomaviruses, we examined genomic DNA isolated from 15 primary medulloblastoma and 5 sPNET biopsy specimens and from 2 medulloblastoma cell lines for the presence of DNA sequences from the polyomaviruses simian virus 40 (SV40), JC virus, and BK virus. These polyomaviruses have oncogenic potential in animals, and their DNA sequences have been detected in other surveys of various solid tumors, including childhood brain tumors. The tumor DNA samples were analyzed by Southern blot hybridization of polymerase chain reaction products that employed probes designed to detect specific polyomavirus sequences. Neither JC virus nor BK virus DNA sequences were detected in any of the specimens. None of the primary medulloblastoma or sPNET specimens contained SV40 sequences. However, SV40 DNA coding and noncoding sequences were detected in the D283-Med (medulloblastoma) cell line. Immunocytochemical studies of D283-Med revealed nuclear expression of SV40 large T antigen. In contrast to childhood ependymomas and choroid plexus tumors, medulloblastomas and sPNETs infrequently express evidence of polyomavirus infection.

Different simian virus 40 genomic regions and sequences homologous with SV40 large T antigen in DNA of human brain and bone tumors and of leukocytes from blood donors

BACKGROUND

Many studies found only a small fragment of the large T-antigen coding sequences in human tumors, raising doubts on authenticity of SV40 sequences detected in these samples.

METHODS

Five different regions of SV40 DNA were investigated in 106 fresh human tumor biopsies (25 brain, 69 bone, 12 Wilms' tumors), 71 tumor-derived cell cultures (38 from brain and 33 from bone tumors) and normal tissues (5 fresh bone biopsies and 38 buffy coats) by polymerase chain reaction (PCR) techniques and filter hybridization with specific oligoprobes. Expression of SV40 Tag sequences was analyzed in human tumor specimens by RT-PCR.

RESULTS

SV40 large T-antigen sequences were detected at high prevalence, in human biopsies of primary brain (37-44%) and bone (21-37%) tumors, in cell cultures derived from brain (30-54%) and bone (53-80%) tumors. SV40 Tag sequences were detected in 29% of buffy coats of blood donors. However, only four brain tumor cell lines showed all the five regions of the SV40 genome investigated. Expression of SV40 Tag sequences was found in 11 of 27 (41%) human tumor samples. DNA sequence analysis indicated that the PCR-amplified products belong to the SV40 wild type. Polymerase chain reaction products of Tag middle portion from 20 of 78 (26%) samples showed a 97% homology with telomeric sequences of human chromosomes 10 and 11.

CONCLUSIONS

Authentic SV40 sequences were detected in human samples. The expression of SV40 Tag sequences indicates that SV40 could play a role, as a cofactor, in the onset/progression of specific human cancers. The inability to detect some regions of the virus genome may suggest that those regions are not required for tumor persistence or growth and have been lost or, alternatively, may be the result of assay conditions that were unable to PCR-amplify those regions in the tumors.

A subset of cells expressing SV40 large T antigen contain elevated p53 levels and have an altered cell cycle phenotype

Cells transformed by the simian virus 40 (SV40) large T antigen (Tag) contain elevated levels of cellular p53 protein. To quantify this relationship, levels of p53 were measured in NIH 3T3 cells that expressed different concentrations of Tag. Using immunoblotting, average p53 levels were shown to increase linearly with Tag concentrations in these cell lines. Single-cell measurements were also performed using flow cytometry to measure p53 immunofluorescence. Surprisingly, the flow cytometry experiments showed that two distinct cell populations, based on p53 content, were present in cells expressing high levels of Tag. One cell population contained elevated p53 levels. A second population did not contain elevated p53, even though high concentrations of Tag were present in the cells. This latter cell population did not appear to arise because of mutations in either Tag or p53. The two cell populations also had phenotypic differences. In exponentially growing cells, Tag alters the cell cycle distribution (decreases the percentage of G1 phase cells and increases the percentages of S and G2 + M phase cells). This phenotype was maximum in the cell population containing elevated p53. A lesser phenotype was found in the cell population that did not contain elevated p53. These data show, firstly, that cells can express significant levels of Tag and not contain elevated levels of p53 and, secondly, that elevated p53 correlates with the altered cell cycle distribution produced by Tag in growing cells.

Inducible and reversible beta-cell autoimmunity and hyperplasia in transgenic mice expressing a conditional oncogene

Expression of the SV40 T antigen (Tag) in pancreatic beta-cells in transgenic mice has been shown to induce beta-cell tumorigenesis. We generated transgenic mice in which Tag expression is inducible and reversible by the tet-on gene regulation system. These mice develop beta-cell tumors only when treated with the inducer doxycycline (dox). Tag expression in vivo is reversible upon dox withdrawal. As a result, beta-cell proliferation is greatly reduced, indicating that genetic changes, which may occur in the transformed cells, do not allow Tag-independent proliferation. Induction of Tag expression after immune recognition of self-antigens has been established triggers an autoimmune response against beta-cells, as evidenced by insulitis. Shut-off of Tag expression results in elimination of insulitis, suggesting that this process depends on continuous expression of the target antigen. In addition, the reversibility of autoimmunity suggests that beta-cell damage caused by the anti-Tag immune response does not elicit secondary responses to other newly exposed beta-cell antigens, which would have persisted after Tag elimination. beta-Cell proliferation in this model is accompanied by cell apoptosis. Apoptosis persisted for several weeks in the islets after dox removal. In close to 40% of the mice analyzed, this process reduced the islet size back to normal, suggesting the existence of a homeostatic mechanism that maintains beta-cell mass within the normal range.

Absence of SV-40 large T antigen (Tag) in malignant mesothelioma effusions: an immunocytochemical study

Simian Virus 40 (SV 40) was recently implicated in the pathogenesis of malignant mesothelioma. The oncogenic capacity of SV-40 is a function of a nuclear protein, the large T antigen (Tag). SV-40 Tag DNA sequences are detected by the polymerase chain reaction in 40-80% of malignant mesothelial proliferations. However, the role of immunohistochemistry (IHC) in demonstrating the nuclear localization of Tag is controversial. We sought to determine the clinical utility of SV-40 Tag IHC in pleural effusion cytology as an ancillary tool in the cytologic diagnosis of malignant mesothelioma (MM). Formalin-fixed, paraffin-embedded cell block sections from 100 pleural effusions (32 MMs, 25 benign reactive, 43 metastatic adenocarcinomas) were immunostained for the SV-40 anti-Tag, using two primary monoclonal SV-40 Tag antibodies: clone Pab 416 and clone Pab 101. Despite strong and consistent immunoreactivity in positive controls, no nuclear immunostaining was observed in any case. We believe the small sample size in cytology cell block sections, the low viral copy number in infected cells, and the effect of formalin fixation may have resulted in absence of immunoreactivity. The role of SV-40 Tag IHC in diagnostic cytopathology remains unclear unless further studies reliably show its detection.

Immortalization of rat middle ear epithelial cells by adeno 12-SV40 hybrid virus

Rat middle ear epithelial cells were infected with the adeno 12-SV40 hybrid virus. The cell line thus obtained displays features of primary cultured epithelial cells in both light microscopic and ultrastructural examinations. The immortalized cells have been in continuous proliferation for 40 passages and more than 17 months. Immunohistochemical analysis of the immortalized cells was positive for the SV40 T antigen and the tumor suppressor protein p53. The cells also stained positive for cytokeratin, an epithelial cell marker, and negative for vimentin, a fibroblast marker. These results, together with karyotype analysis, indicate that this cell line originated from rat middle ear epithelial cells and retains the characteristics of epithelial cells. This cell line will be useful for studying the normal cellular biology of middle ear epithelial cells, as well as the cellular and molecular mechanisms involved in the bacteria-middle ear epithelial cell interaction.

Human polyomavirus BK (BKV) and neuroblastoma: mechanisms of oncogenic action and possible strategy for novel treatment

BACKGROUND

We reported previously that nearly all human neuroblastomas analyzed contain and express genomic DNA sequences deriving from the human polyomavirus BK (BKV) [Flaegstad et al.: Cancer Res 59:1160-1163, 1999].

PROCEDURE

Here we show that the BKV large T antigen is expressed and bound to p53 in neuroblastoma cells and that this interference compromises the tumor suppressor function of p53.

RESULTS

Treatment of neuroblastoma cells with large T antigen antisense constructs relocated active p53 to the nucleus. The relocation event was accompanied by enhanced p21(waf1/cip1) expression as well as induced apoptosis.

CONCLUSIONS

Continuous antisense oligonucleotide treatment of nude rats with human neuroblastoma xenografts resulted in a significant but incomplete reduction of tumor growth compared to rats treated with saline.

Absence of SV40 large T-antigen expression in human mesothelioma cell lines

Simian virus (SV) 40 and SV40-like DNA sequences have recently been detected in several types of human tumors, including malignant mesothelioma. However, the presence of SV40 DNA sequences is not sufficient to account for its possible role in tumor development because the viral proteins must be expressed and ultimately impair the function of relevant cell proteins, such as p53 and pRb. In this study we investigated SV40 large T antigen (SV40 Tag) protein expression in mesothelioma cell lines, established in our laboratory, by Western blotting, immunoprecipitation, and immunocytochemistry using Tag-specific mouse monoclonal antibodies (mAbs) Ab-1 (or Pab 419). By Western blotting of cell extracts, none of the mesothelioma cell lines expressed detectable amounts of SV40 Tag. However, we found that Ab-1 as well as Pab-101, another SV 40 Tag-specific mAb, may generate false-positive signals due to the fact that both antibody preparations are contaminated by a protein of similar size (90 kD) as SV40 Tag and react with the various secondary horseradish peroxidase- conjugated antimouse immunoglobulin Gs tested. The present study suggests that immunodetection of SV40 Tag protein may be puzzling because this contaminating Taglike protein may bind to particular cell structures, thereby generating false-positive signals.

Pituitary neoplasia induced by expression of human neurotropic polyomavirus, JCV, early genome in transgenic mice

In recent years, there has been mounting evidence pointing to the association of polyomaviruses with a wide range of human cancers. The human neurotropic polyomavirus, JCV, infecting greater than 75% of the human population produces a regulatory protein named T-antigen which is expressed at the early phase of viral lytic infection and plays a critical role in completion of the viral life cycle. Furthermore, this protein has the ability to transform neural cells in vitro and its expression has been detected in several human neural-origin tumors. To further investigate the oncogenic potential of the JCV early protein in vivo, transgenic mice expressing JCV T-antigen under the control of its own promoter were generated. Nearly 50% of the animals developed large, solid masses within the base of the skull by 1 year of age. Evaluation of the location as well as histological and immunohistochemical data suggest that the tumors arise from the pituitary gland. As T-antigen is known to interact with several cell cycle regulators, the neoplasms were analysed for the presence of the tumor suppressor protein, p53. Immunoprecipitation/Western blot analysis demonstrated overexpression of wild-type, but not mutant p53 within tumor tissue. In addition, co-immunoprecipitation established an interaction between p53 and T-antigen and overexpression of p53 downstream target protein, p21/WAF1. This report describes the analysis of inheritable pituitary adenomas induced by expression of the human polyomavirus, JCV T-antigen in transgenic mice where T-antigen disrupts the p53 pathway by binding to and sequestering wild-type p53. This animal model may serve as a useful tool to further evaluate mechanisms of tumorigenesis by JCV T-antigen.

Infection with JC virus and possible dysplastic ganglion-like transformation of the cerebral cortical neurons in a case of progressive multifocal leukoencephalopathy

Infection of the cerebral cortical neurons with JC virus (JCV) with possible dysplastic ganglion-like alteration of the infected neurons found in a case of progressive multifocal leukoencephalopathy (PML) is described. The patient was a 21-year-old man with common variable immunodeficiency who died of PML after a 9-month clinical course. At autopsy, the white matter of the cerebrum, brainstem, cerebellum, and spinal cord exhibited extensive demyelination and necrosis. Numerous inclusion-bearing oligodendrocytes and bizarre astrocytes were found. In the occipital and temporal cortex, thick band-like aggregates of dysplastic ganglion-like cells (DGLCs) were found. These DGLCs showed immunohistochemical properties of neurons, and nuclei of some DGLCs were immunoreactive for large T antigen of SV40/JCV and p53, but not for capsid protein JCV VP1. In situ hybridization for mRNA of JCV large T antigen revealed positive signals in the nuclei of some DGLCs. These results indicate that JCV infected neurons and it is suggested that binding of the large T antigen with cellular proteins could have resulted in the dysplastic, ganglion cell-like change of the infected neurons, although the possibility that the aggregates of DGLCs represent a pre-existent malformative lesion of the cortex cannot be excluded completely.

p53, p21(WAF1/CIP1), and MDM2 involvement in the proliferation and apoptosis in an in vitro model of conditionally immortalized human vascular smooth muscle cells

Using an in vitro model of a conditionally immortalized cell line, we have investigated how human vascular smooth muscle cells (VSMCs) are affected by the expression of simian virus 40 (SV40) large T antigen (LT antigen), which binds to cell cycle regulators such as the tumor suppressor protein p53. Cells were obtained after infection of saphenous vein-derived VSMCs with a nonreplicative retroviral vector containing a temperature-sensitive mutant of SV40 LT antigen and were shown to have maintained some characteristics and responses of VSMCs. Under permissive-temperature conditions (36 degrees C), the increased rate of cell proliferation was shown to be associated with expression of LT antigen and with LT antigen binding to and inactivation of p53. p53 inactivation failed to block apoptosis induced by serum withdrawal or UV irradiation. Downregulation of LT antigen expression at a nonpermissive temperature (39 degrees C) was shown to be associated with growth arrest, increased expression of the cell cycle inhibitor p21(WAF1/CIP1), increased murine double minute-2 promoter activity, and differential expression of murine double minute-2 gene products, suggesting that p53-induced transcription/transactivation may be involved in VSMC cycle control but not necessarily in apoptosis. The established SMC line HVTs-SM1 may be a useful model for study of the processes involved in myointimal hyperplasia and cellular aging, as well as for the study of cell cycle control in general.

p53, p21(WAF1/CIP1), and MDM2 involvement in proliferation and apoptosis in an in vitro model of conditionally immortalized human vascular smooth muscle cells

Using an in vitro model of a conditionally immortalized cell line, we investigated how human vascular smooth muscle cells (VSMCs) are affected by the expression of simian virus 40 (SV40) large T antigen (LT antigen), which binds to cell cycle regulators, such as the tumor suppressor protein p53. Cells were obtained after infection of saphenous vein-derived VSMCs with a nonreplicative retroviral vector containing a temperature-sensitive (ts) mutant of SV40 LT antigen and were shown to have maintained some characteristics and responses of VSMCs. Under permissive temperature conditions (36 degrees C), the increased rate of cell proliferation was shown to be associated with expression of LT antigen and with LT-antigen binding to and inactivation of p53. p53 inactivation failed to block apoptosis induced by serum withdrawal or by UV irradiation. Downregulation of LT-antigen expression at the nonpermissive temperature (39 degrees C) was shown to be associated with growth arrest, increased expression of the cell cycle inhibitor p21(WAF1/CIP1), increased MDM2-promoter activity, and differential expression of MDM2 gene products, suggesting that p53-induced transcription/transactivation may be involved in VSMC cell cycle control but not necessarily apoptosis. The established SMC line HVTs-SM1 may be a useful model for the study of processes involved in myointimal hyperplasia and cellular aging, as well as for the study of cell cycle control in general.

JC virus in human glial-derived tumors

To investigate the presence and the role of polyomaviruses JC (JCV), BK (BKV), and the simian polyomavirus (SV40) in human brain tumors, samples from 25 glial-derived tumors (10 astrocytomas, 5 ependymomas, 5 oligodendrogliomas, and 5 glioblastomas) were examined by means of molecular biology and immunohistochemistry. Nested PCR of the large T (LT) region and its sequence analysis showed JCV in 6 cases (4 astrocytomas, 1 oligodendroglioma, and 1 ependymoma), while the transcriptional control region (TCR) was amplified only in 1 astrocytoma, the oligodendroglioma, and the ependymoma, one of which (astrocytoma) also stained positively by immunohistochemistry (JCV LT). TCR sequence analysis of the oligodendroglioma showed a JCV rearranged structure not related to a known viral strain, while the astrocytoma and the ependymoma disclosed a JCV Mad-4 strain that is known to induce brain tumors in animals. We suggest that JCV could have played a role in the pathogenesis of these brain tumors.

Establishment and characterization of an immortalized human sebaceous gland cell line (SZ95)

Human facial sebaceous gland cells were transfected with a PBR-322-based plasmid containing the coding region for the Simian virus-40 large T antigen. The resulting proliferating cell cultures have been passaged over 50 times to date, have been cloned, and show no signs of senescence after 4&DF;1 2 y in vitro, whereas normal human sebocytes can only be grown for three to six passages. The immortalized transfected cells, termed SZ95, expressed the Simian virus-40 large T antigen and presented an hyper-diploid-aneuploid karyotype with a modal chromosome number of 64.5. The SZ95 cell line exhibited epithelial, polymorphous characteristics with different cell sizes of up to 3.25-fold during proliferation and 6-fold at confluence, showing numerous cytoplasmic lipid droplets. The cells showed large cytoplasm profiles with abundant organelles, including vacuoles and myelin figures which indicated lipid synthesis. Lack of or only few desmosomal areas were observed. SZ95 cells expressed molecules typically associated with human sebocytes, such as keratins 7, 13, and 19, and several proteins of the polymorphous epithelial mucin family. Functional studies revealed synthesis of the sebaceous lipids squalene and wax esters as well as of triglycerides and free fatty acids, even after 25-40 passages; active lipid secretion; population doubling times of 52.4 +/- 1.6 h; reduced growth but maintenance of lipid synthesis under serum-free conditions; and retrieval of cell proliferation after addition of 5alpha-dihydrotestosterone. Retinoids significantly inhibited proliferation of certain SZ95 cell clones in the expected magnitude 13-cis-retinoic acid > all-trans-retinoic acid > > acitretin. Thus SZ95 is an immortalized human sebaceous gland cell line that shows the morphologic, phenotypic and functional characteristics of normal human sebocytes.

Detection of human neurotropic JC virus DNA sequence and expression of the viral oncogenic protein in pediatric medulloblastomas

Medulloblastoma represents greater than 25% of childhood intracranial neoplasms and is considered a highly malignant tumor. This tumor, which arises predominantly in the cerebellar vermis, preferentially affects children between the ages of 5 and 15. Although the etiology of medulloblastomas in humans remains unknown, results from several experiments have indicated that the human neurotropic JC virus (JCV) is able to induce cerebellar neoplasms in rodents that exhibit a phenotype similar to that of human medulloblastomas. JCV is a polyomavirus that is widespread in the human population, with infection occurring most frequently in early childhood. In this study, we have examined the possible association of JCV with human medulloblastomas. By using PCR techniques we demonstrate that 11 of 23 samples of tumor tissue contain DNA sequences corresponding to three different regions of the JCV genome. More importantly, we demonstrate the presence of DNA sequences encoding the N- and C-terminal regions of the JCV oncogenic protein, T antigen, in 11 of 23 samples and the production of T antigen in the nuclei of 4 samples of tumor tissue. These observations provide evidence for a possible association of JCV with human medulloblastomas.

Retina-derived microglial cells induce photoreceptor cell death in vitro

In animals with retinal degeneration, the presence of activated microglial cells in the outer retina during the early stages of injury suggests that they may be involved in the ensuing photoreceptor cell death. In the following study, we investigated the effects of rat retina-derived microglial cells on a photoreceptor cell line (661w) using cell culture techniques. The difficulty of obtaining pure populations of photoreceptor cells necessitated our use of the 661w photoreceptor cells generated from retinas of transgenic mice. 661w Cells were incubated for 24-48 h in basal medium or basal medium conditioned by activated microglial cells (MGCM) or Müller cells (MCCM), and tested for cell death using lactate dehydrogenase (LDH) assay. The induction of apoptosis in the 661w cells by MGCM was investigated using Terminal deoxynucleotidyl Transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and DNA laddering. Treatment of 661w cells with MGCM for 48 h resulted in approximately 73% of cells dead as compared with 19-20% of cells grown in either basal medium or MCCM. Serum supplementation or pretreatment with heat did not abolish the cytotoxicity of MGCM. More TUNEL-positive cells were observed in MGCM-treated cultures as compared with those in basal medium. Bands in multiples of approximately 180 bp formed DNA ladders in MGCM-treated but not in basal medium-treated samples. Our study shows that microglial cells release soluble product(s) that induce degeneration of cultured photoreceptor cells. Moreover, the mechanism of microglia-induced photoreceptor cell death may involve apoptosis similar to that observed in animals with retinal degeneration.

Haploid male germ cells show no susceptibility to transformation by simian virus 40 large tumour antigen in transgenic mice

Cell-type specific tumorigenesis can be induced in transgenic mice by the directed expression of simian virus 40 (SV 40) large tumour antigen (TAg). In an attempt to determine the susceptibility of haploid male germ cells to neoplastic transformation by this oncogene, transgenic mice were generated that harboured a chimeric gene composed of the SV40 T antigen genes fused to the 2.3-kb 5' flanking sequences of the rat proacrosin gene. It was previously shown that this regulatory sequence is able specifically to direct the expression of CAT reporter gene in male germ cells with the onset of translation in early haploid male germ cells. The transgene showed regulated expression in male germ cells. Although T antigen immunostaining was detected specifically in spermatids, no testicular pathology was observed. This indicates that spermatids show no susceptibility to transformation by oncogene TAg. However, in about 10% of animals of two independent transgenic lines, we could find non-testicular tumours in abdomen with a sarcoma-like structure in advanced age which showed SV40 TAg expression.

Asbestos induction of extended lifespan in normal human mesothelial cells: interindividual susceptibility and SV40 T antigen

Normal human mesothelial cells from individual donors were studied for susceptibility to asbestos-induction of apoptosis and generation of an extended lifespan population. Such populations were generated after death of the majority of cells and arose from a subset of mesothelial cultures (4/16) whereas fibroblastic cells (5/5) did not develop extended lifespan populations after asbestos exposure. All mesothelial cultures were examined for the presence of SV40 T antigen to obtain information on (i) the presence of SV40 T antigen expression in normal human mesothelial cells and (ii) the relationship between generation of an extended lifespan population and expression of SV40 T antigen. Immunostaining for SV40 T antigen was positive in 2/38 normal human mesothelial cultures. These cultures also had elevated p53 expression. However, the two isolates expressing SV40 T antigen did not exhibit enhanced proliferative potential or develop an extended lifespan population. Asbestos-generated extended lifespan populations were specifically resistant to asbestos-mediated but not to alpha-Fas-induced apoptosis. Deletion of p16Ink4a was shown in 70% of tumor samples. All mesothelioma cell lines examined showed homozygous deletion of this locus which extended to exon 1beta. Extended lifespan cultures were examined for expression of p16Ink4a to establish whether deletion was an early response to asbestos exposure. During their rapid growth phase, extended lifespan cultures showed decreased expression of p16Ink4a relative to untreated cultures, but methylation was not observed, and p16Ink4a expression became elevated when cells entered culture crisis. These data extend the earlier observation that asbestos can generate extended lifespan populations, providing data on frequency and cell type specificity. In addition, this report shows that generation of such populations does not require expression of SV40 T antigen. Extended lifespan cells could represent a population expressing early changes critical for mesothelioma development. Further study of these populations could identify such changes.

Enhanced binding to origin DNA at low pH enables easy detection of polyomavirus large T antigen by gel mobility shift assay of unfixed complexes

Enhanced, stable binding by polyomavirus large T antigen to the viral DNA replication origin at pH 6 allowed the development of a gel mobility shift assay for the detection of large T antigen. Such assays were not possible at pH 7.6 without previous fixation, due to instability of the complexes. We demonstrated that the gel mobility shift assay at pH 6 is very sensitive, allowing the detection of as little as 5 ng large T antigen, and is highly specific for DNA containing G(A/G)GGC target sequences. This method was used to detect large T antigen in crude cell lysates from transformed yeast cell lines or nuclear extracts from infected insect cells. Large T antigen-DNA complexes remained at or near the loading well in 5% acrylamide or 1.5% agarose gels, indicating that these complexes are very large. Glycerol gradient analysis showed that protein-DNA complexes formed at pH 6 were massive, and that large T antigen also formed large complexes when incubated at low pH in the absence of DNA. These results show that pH has a major effect on binding of large T antigen to its multiple target sites in the viral origin of DNA replication, presumably by affecting protein-protein interactions that are important for the stability of large T antigen-DNA complexes.

Association of simian virus 40 with a central nervous system lesion distinct from progressive multifocal leukoencephalopathy in macaques with AIDS

The primate polyomavirus SV40 is known to cause interstitial nephritis in primary infections and progressive multifocal leukoencephalopathy (PML) upon reactivation of a latent infection in SIV-infected macaques. We now describe a second central nervous system manifestation of SV40: a meningoencephalitis affecting cerebral gray matter, without demyelination, distinct from PML. Meningoencephalitis appears also to be a primary manifestation of SV40 infection and can be seen in conjunction with SV40-induced interstitial nephritis and pneumonitis. The difference in the lesions of meningoencephalitis and PML does not appear to be due to cellular tropism, as both oligodendrocytes and astrocytes are infected in PML and meningoencephalitis, as determined by in situ hybridization or immunohistochemistry for SV40 coupled with immunohistochemistry for cellular determinants. This is further supported by examination of SV40 nucleic acid sequences from the ori-enhancer and large-T-antigen regions, which reveals no tissue-or lesion-specific variation in SV40 sequences.

Astrocytomas and choroid plexus tumors in two families with identical p53 germline mutations

Germline p53 mutations carry an increased risk of development of breast cancer, soft tissue and osteosarcomas, brain tumors, leukemia and adrenocortical carcinomas. Cerebral neoplasms are usually of astrocytic lineage and occur in 40% of affected families. This report presents clinical, neuropathological and molecular genetic data from 2 families in France with an identical p53 germline mutation in codon 248 (CGG->TGG; Arg->Trp) and a clustering of CNS tumors. The youngest patient in each family developed a malignant choroid plexus tumor while several young adults of both kindred succumbed to low-grade astrocytoma, anaplastic astrocytoma or glioblastoma. The only non-neural neoplasm was an adrenocortical carcinoma in a boy aged 4 years who developed an anaplastic choroid plexus papilloma 2 years later. Of 2 previously reported inherited choroid plexus tumors, 1 occurred in a family which also carried a germline mutation in codon 248. It remains to be shown whether this unusual pattern of CNS tumors is due to an organ-specific effect of this particular p53 mutation or whether it reflects the genetic background of the affected families.

Simian virus 40 oncogenesis in hamsters

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.

Identification of SV40 in brain, kidney and urine of healthy and SIV-infected rhesus monkeys

Recent reports of simian virus 40 (SV40) sequences in human tumors have prompted investigations into the poorly understood association of this polyomavirus with its primate host, the rhesus monkey (Macaca mulatta). In the present study we have used PCR to analyze tissues from 20 monkeys for the presence of SV40. Five of the animals, which were infected with simian immunodeficiency virus (SIV), were found to exhibit SV40-induced lesions and to have SV40 sequences present in their kidney and brain. Lesions associated with SV40 were not observed in 15 SIV monkeys, and SV40 DNA was detected in kidney and urine of only one of these animals. Three regions of SV40 DNA were examined in each tissue: the non-coding transcriptional control region (TCR), the sequences encoding the host range domain (HRD) within the carboxy-terminus of T antigen (TAg), and a portion of the VP1 gene. Each region contained nucleotide alterations compared to the SV40 reference strain 776. In all six animals, the TCR had an archetype structure containing a single 72 bp enhancer element. In addition, the TCR amplified from two animals lacked one of three copies of a GC-rich 21 bp repeat which is part of the promoter in strain 776. Multiple clones of unique HRD sequences were derived from different animals, and in some instances from the same animal. No correlation was found between a particular HRD sequence and its presence in a specific tissue type. Nucleotide changes identified within the VP1 gene indicate that this region, as with the closely-related human polyomavirus JCV, may permit the typing of the virus into individual strains. This study is the first to characterize SV40 sequences present in both healthy and SIV-infected animals and supports the suggestion that strain 776 is not the predominant type of SV40 circulating in its natural host.

Development of a syngeneic bovine fibroblast cell line: implications for the study of bovine cytotoxic T lymphocytes

The study of T-cell-mediated cytotoxicity in domestic animals, especially in cattle, has been hampered by the lack of proper restimulatory as well as target systems. While the currently available bovine cell lines have not been typed for the major histocompatibility complex (MHC) class I molecules they express, methods to derive lines of cells obtained from animals that are MHC-typed have not been thoroughly explored. In the present study, we describe a method for the development of cell lines from MHC-typed animals. Cells obtained from the skin of a calf typed as bovine lymphocyte antigen-A11/-A13 were transfected with a plasmid containing the whole genome of simian vacuolating virus 40 (SV40). A cell line was derived from the resultant transfectants. This cell line expressed bovine MHC class I molecules on the cell surface, and SV40 large T antigen in the nucleus. The cells were permissive to the replicative cycle of bovine herpesvirus-1 (BHV-1), and the major glycoproteins of BHV-1 were expressed at expected times after infection. The present study should contribute to the study of cytotoxic T lymphocyte response of cattle to BHV-1 and other intracellular pathogens.

Simian virus 40-like DNA sequences in human papillary thyroid carcinomas

Sequences of the SV40 virus, a virus of Asian macaques, have been found in human tumors, such as pleural mesotheliomas, ependimomas and choroid plexus tumors. Transgenic mice carrying the SV40 large T gene under the transcriptional control of the thyroglobulin gene promoter, develop thyroid dedifferentiation and follicular thyroid cell proliferation, leading to thyroid hyperplasia and adenocarcinomas. On these bases we investigated the presence of SV40 DNA sequences in 69 samples of papillary thyroid carcinomas (PTC) and in other thyroid and non-thyroid carcinomas, as well as in benign thyroid diseases. By Southern blot and PCR amplification followed by sequence analysis, we found the presence of SV40-related sequences integrated in the tumoral DNA of three cases of PTC. At least the 203 bp fragment of the aminoterminus of large T antigen, the 294 bp fragment of the VP1 gene and the 483 bp entire regulatory region were present in the tumoral DNA of these patients. SV40 sequences were not found in tissues other than PTC. Our results demonstrate that, in addition to previous findings in mesotheliomas and brain tumors, SV40 is somehow linked to papillary thyroid carcinoma. Although our data do not demonstrate a causative role in the development of PTC, this possibility must be considered and requires further studies.