Papovavirus-related RNA sequences in human neurogenic tumours

Association Between Simian Virus 40 and Human Tumors

Simian virus 40 (SV40) is a small DNA tumor virus of monkey origin. This polyomavirus was administered to human populations mainly through contaminated polio vaccines, which were produced in naturally infected SV40 monkey cells. Previous molecular biology and recent immunological assays have indicated that SV40 is spreading in human populations, independently from earlier SV40-contaminated vaccines. SV40 DNA sequences have been detected at a higher prevalence in specific human cancer specimens, such as the brain and bone tumors, malignant pleural mesotheliomas, and lymphoproliferative disorders, compared to the corresponding normal tissues/specimens. However, other investigations, which reported negative data, did not confirm an association between SV40 and human tumors. To circumvent the controversies, which have arisen because of these molecular biology studies, immunological researches with newly developed indirect ELISA tests were carried out in serum samples from patients affected by the same kind of tumors as mentioned above. These innovative indirect ELISAs employ synthetic peptides as mimotopes/specific SV40 antigens. SV40 mimotopes do not cross-react with the homologous human polyomaviruses, BKPyV, and JCPyV. Immunological data obtained from indirect ELISAs, using SV40 mimotopes, employed to analyze serum samples from oncological patients, have indicated that these sera had a higher prevalence of antibodies against SV40 compared to healthy subjects. The main data on (i) the biology and genetics of SV40; (ii) the epidemiology of SV40 in the general population, (iii) the mechanisms of SV40 transformation; (iv) the putative role of SV40 in the onset/progression of specific human tumors, and (v) its association with other human diseases are reported in this review.

Recrudescence of herpes virus infections following resection of schwannomas. An antiviral role of merlin?

After schwannoma resection, reactivation of herpes infections were reported. Also, IgM antibody titers against Herpes viri increase among 30% of patients, who develop fascial palsy following schwannoma resection. Merlin interacts with p53 pathway and seems to function as a suppressor of viral propagation. Loss of merlin may increase viral particles in nerve fascicles, yet these may fail to cause infections due to immunostimulation by other aberrant antigens present in schwannoma cells. Removal of schwannomas may decrease the antigenic diversity and trigger viral recrudescence. Understanding the viral etiology - molecular merlin interactions in schwannoma tissues may also help to develop strategies against delayed fascial palsy seen following schwannoma resection.

Biosafety in handling gene transfer vectors

This unit is devoted to safety issues that must be considered when generating and working with vectors for gene therapy. A short description of the relevant regulatory bodies and mechanisms is followed by a general discussion of containment and safety procedures. This is followed by vector-specific guidelines for nine commonly used vector systems, including adenovirus, vaccinia, HSV-1, lentivirus, and nonviral vectors. Recent tragic experiences with retroviral integration near oncogene loci demonstrate the surprise effects of successful gene therapy. The unit also outlines the problems encountered when taking a promising vector to clinical trials.

Mesothelioma mortality in Europe: impact of asbestos consumption and simian virus 40

Background

It is well established that asbestos is the most important cause of mesothelioma. The role of simian virus 40 (SV40) in mesothelioma development, on the other hand, remains controversial. This potential human oncogene has been introduced into various populations through contaminated polio vaccines. The aim of this study was to investigate whether the possible presence of SV40 in various European countries, as indicated either by molecular genetic evidence or previous exposure to SV40-contaminated vaccines, had any effect on pleural cancer rates in the respective countries.

Methods

We conducted a Medline search that covered the period from January 1969 to August 2005 for reports on the detection of SV40 DNA in human tissue samples. In addition, we collected all available information about the types of polio vaccines that had been used in these European countries and their SV40 contamination status.

Results

Our ecological analysis confirms that pleural cancer mortality in males, but not in females, correlates with the extent of asbestos exposure 25 – 30 years earlier. In contrast, neither the presence of SV40 DNA in tumor samples nor a previous vaccination exposure had any detectable influence on the cancer mortality rate in neither in males (asbestos-corrected rates) nor in females.

Conclusion

Using the currently existing data on SV40 prevalence, no association between SV40 prevalence and asbestos-corrected male pleural cancer can be demonstrated.

Emergent human pathogen simian virus 40 and its role in cancer

The polyomavirus simian virus 40 (SV40) is a known oncogenic DNA virus which induces primary brain and bone cancers, malignant mesothelioma, and lymphomas in laboratory animals. Persuasive evidence now indicates that SV40 is causing infections in humans today and represents an emerging pathogen. A meta-analysis of molecular, pathological, and clinical data from 1,793 cancer patients indicates that there is a significant excess risk of SV40 associated with human primary brain cancers, primary bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. Experimental data strongly suggest that SV40 may be functionally important in the development of some of those human malignancies. Therefore, the major types of tumors induced by SV40 in laboratory animals are the same as those human malignancies found to contain SV40 markers. The Institute of Medicine recently concluded that "the biological evidence is of moderate strength that SV40 exposure could lead to cancer in humans under natural conditions." This review analyzes the accumulating data that indicate that SV40 is a pathogen which has a possible etiologic role in human malignancies. Future research directions are considered.

Meningiomas: Updating Basic Science, Management, and Outcome

BACKGROUND

Meningiomas are biologically complex and clinically and surgically challenging. These features, combined with the rewarding potential for cure, make them of great interest to neurologists, neurosurgeons, and neuroscientists alike.

REVIEW SUMMARY

Initially, we review the clinical context of meningiomas, particularly recent changes in histopathological classification, diagnosis, and neuroimaging. Secondly, the underlying basic science as it has evolved over the last decades is summarized. The status of areas recently of intense interest, such as steroid hormone receptors and oncogenic viruses is described. Additionally, emerging areas of great promise, such as cytogenetics and molecular biology are presented. Lastly, we describe recent advances in management. In particular, skull-base surgery, image-guided surgery, and advances in radiotherapy are emphasized. The possible impact of basic research on management and outcome is also outlined.

CONCLUSIONS

Although usually benign and amenable to cure, meningiomas still present significant diagnostic and treatment challenges. Advances in basic science, surgery, and adjuvant therapy are widening the potential for safe, effective, evidence-based management leading to even better outcomes

SV40 in human brain cancers and non-Hodgkin's lymphoma

Simian virus 40 (SV40) is a potent DNA tumor virus that is known to induce primary brain cancers 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 family members. 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 cancers, and a systematic assessment of the data indicates that the virus is significantly associated with this group of human tumors. In addition, recent large independent studies showed that SV40 T-ag DNA is significantly associated with human non-Hodgkin's lymphoma (NHL). Although the prevalence of SV40 infections in humans is not known, numerous observations suggest that SV40 is a pathogen in the human population today. This review examines the molecular biology, pathology, and clinical data implicating SV40 in the pathogenesis of primary human brain cancers and NHL and discusses future research directions needed to define a possible etiologic role for SV40 in these malignancies.

Simian virus 40 in human cancers

BACKGROUND

Many studies have reported the presence of simian virus 40 (SV40) deoxyribonucleic acid (DNA) or protein in human brain tumors and bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. However, the small samples and lack of control groups in some reports have made it difficult to assess their reliability.

METHODS

Studies were included in this analysis if they met the following criteria: original studies of patients with primary brain tumors and bone cancers, malignant mesothelioma, or non-Hodgkin's lymphoma; the investigation of SV40 was performed on primary cancer specimens; the analysis included a control group; and the same technique was used for cases and controls. Included reports were published from 1975 to 2002.

RESULTS

Thirteen studies fulfilled the criteria for the investigation of primary brain cancers (661 tumors and 482 control samples). Specimens from patients with brain tumors were almost four times more likely to have evidence of SV40 infection than were those from controls (odds ratio [OR] = 3.9; 95% confidence interval [CI]: 2.6 to 5.8). The association was even stronger for mesothelioma (OR = 17; 95% CI: 10 to 28; based on 15 studies with 528 mesothelioma samples and 468 control samples) and for bone cancer (OR = 25; 95% CI: 6.8 to 88; based on four studies with 303 cancers and 121 control samples). SV40 DNA was also more frequent in samples from patients with non-Hodgkin's lymphoma (OR = 5.4; 95% CI: 3.1 to 9.3; based on three studies with 301 cases and 578 control samples) than from controls.

CONCLUSION

These results establish that SV40 is associated significantly with brain tumors, bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. Studies are needed to assess current prevalence of SV40 infections.

Conventional epidemiology and the link between SV40 and human cancers

Simian virus 40 (SV40) is known to cause tumourigenesis. The main types of tumour induced by SV40 in laboratory animals mirror the human cancers that have been found to contain SV40 DNA or the viral oncoprotein. Increasing amounts of data support the notion that SV40 may be an aetiological factor in the development of human cancers. Retrospective birth cohort studies have been used in attempts to refute the alleged causal link between SV40 and human cancers. However, these observational studies are affected by several important confounding factors, which mean that firm conclusions cannot be drawn. In this essay, we consider the unique features of SV40 infection in humans and examine the limitations of conventional studies that seek to disprove the aetiological link with human cancer.

Association of SV40 with human tumours

SV40 was discovered as a contaminant of poliovirus vaccines that were inadvertently administered to millions of people in Europe and the United States between 1955 and 1963. Shortly afterwards, SV40 was proven to be oncogenic in rodents and capable of transforming human and animal cells in vitro. The possibility that SV40 might cause tumours in humans thus became a subject of scientific and public interest and scrutiny. However, largely due to a lack of significant epidemiological evidence, interest in assessing SV40's potential carcinogenic role in humans diminished. Recently, many laboratories have reported the presence of SV40-like DNA in a high proportion of human mesotheliomas, ependymomas and osteosarcoma (the three main types of tumours caused by virus in hamsters), renewing the question whether SV40 might be a human tumour virus. Molecular data from these studies are reviewed to re-evaluate the potential role of SV40 as a human carcinogen.

Cell and molecular biology of simian virus 40: implications for human infections and disease

Simian virus 40 (SV40), a polyomavirus of rhesus macaque origin, was discovered in 1960 as a contaminant of polio vaccines that were distributed to millions of people from 1955 through early 1963. SV40 is a potent DNA tumor virus that induces tumors in rodents and transforms many types of cells in culture, including those of human origin. This virus has been a favored laboratory model for mechanistic studies of molecular processes in eukaryotic cells and of cellular transformation. The viral replication protein, named large T antigen (T-ag), is also the viral oncoprotein. There is a single serotype of SV40, but multiple strains of virus exist that are distinguishable by nucleotide differences in the regulatory region of the viral genome and in the part of the T-ag gene that encodes the protein's carboxyl terminus. Natural infections in monkeys by SV40 are usually benign but may become pathogenic in immunocompromised animals, and multiple tissues can be infected. SV40 can replicate in certain types of simian and human cells. SV40-neutralizing antibodies have been detected in individuals not exposed to contaminated polio vaccines. SV40 DNA has been identified in some normal human tissues, and there are accumulating reports of detection of SV40 DNA and/or T-ag in a variety of human tumors. This review presents aspects of replication and cell transformation by SV40 and considers their implications for human infections and disease pathogenesis by the virus. Critical assessment of virologic and epidemiologic data suggests a probable causative role for SV40 in certain human cancers, but additional studies are necessary to prove etiology.

Non-lymphomatous brain tumors in HIV-1 infection: a review

A broad spectrum of malignant tumors affecting various organ systems in HIV-1 infected patients have been described in larger series. Intracerebral mass lesions encountered in HIV-1 infection are mostly due to toxoplasmosis and central nervous system (CNS) lymphoma. Brain tumors (excluding lymphomas) occurring in HIV-1 infected patients have only occasionally been described. The present review summarizes these diverse tumor entities and reports on the controversial theories of a possible oncogenic potential of HIV-1. Although rare, intracerebral tumors must be considered in the differential diagnosis of an intracranial space-occupying lesion in an HIV-1 infected patient.

Epidemiology and etiology of intracranial meningiomas: a review

The frequency of meningiomas has been the topic of relatively few reports. Hospital-based brain tumor series indicate that the incidence is approximately 20% of all intracranial tumors; population-based studies indicate an overall incidence of 2.3/100,000. Although intracranial tumors as a whole show a higher prevalence in males than in females, meningiomas have a 2:1 female-to-male ratio. Between Caucasians and Africans, African-Americans, and Asians, certain differences also have been noted. Meningiomas in children are rare and differ from those in adults and other childhood tumors; they are even more rare in infants. Several features indicating etiologic factors have been identified, among which are ionizing radiation, head injury, hormones, and other receptor binding sites, genetic factors, and viruses. The most common source of exposure of the head to ionizing radiation is dental radiographic examination. Since 1922, head trauma has been considered a possible risk factor, but recent large studies do not support this link. Several factors have prompted studies of estrogens and progestogens as risk factors for meningiomas. Other studies have sought to determine if certain individuals have an inherited predisposition for developing a meningioma and/or if viruses, which may act alone or with other mutagens, figure into the formation of a meningioma. The most promising studies are those of cytogenetics, and future elucidation of factors associated with the loss of one copy of chromosome 22, another phenomenon that has been identified in meningiomas, may lead to screening tests and gene therapy.

Acquired immune deficiency syndrome (AIDS) and cerebral astrocytoma

The presence of cerebral lesions in patients affected by the acquired immune deficiency syndrome (AIDS) has been estimated to be around 10%, with the majority being infective lesions or primary central nervous system lymphomas. The co-occurrence of a cerebral glioma in such patients is rare. The aim of this report is to present four more cases, discussing their clinical and neuroradiological features, as well as the outcome and the possible pathogenesis.

Detection of polyomaviral DNA sequences in normal and adenomatous human pituitary tissues using the polymerase chain reaction

BACKGROUND

Tumor viruses are known to have a role in the pathogenesis of many types of benign and malignant human tumors. The possible roles of these viruses in the development of human pituitary tumors have not been investigated.

METHODS

The polymerase chain reaction was used to screen human pituitary tumors for human papillomaviral (HPV) and Polyomaviral DNA sequences. Sets of consensus primers, which are capable of amplifying HPV Types 16, 18, and 33 and polyomavirus BK, JC, and SV40, were used in these experiments.

RESULTS

Amplification products were not detected using HPV consensus primers in 30 tumors. Twenty-six of 30 tumors demonstrated an amplification product with polyomaviral primers that hybridized to SV40 and BK internal probes and was confirmed to be SV40 in one tumor by direct sequencing. Ten normal postmortem pituitary samples then were examined similarly with Polyomaviral consensus primers; 8 of 10 normal samples demonstrated a similar amplification product that also hybridized with SV40 and BK internal probes by Southern blotting. Polyomaviral DNA sequences in normal and tumor samples were not present at levels detectable by genomic Southern blotting. Expressed viral protein (large T antigen) was not demonstrated in positive samples by Western blot analysis.

CONCLUSIONS

These findings, that polyomaviral DNA sequences are detectable at low levels in certain normal tissues, are in agreement with those of other groups and, to the authors' knowledge, serve as the first report of polyomaviral latency in human pituitary tissue. A role for polyomaviruses in pituitary tumorigenesis could not be established in this analysis.

Ependymoblastoma in an HIV-positive hemophilic girl

A case of an HIV-positive hemophilic girl with an ependymoblastoma is presented. The unusual association between the HIV-related condition and her brain tumor is discussed, speculating a viral mechanism involved in the induction of neoplasia.

Progressive multifocal leukoencephalopathy and gliomas in a HIV-negative patient

A case of progressive multifocal leukoencephalopathy (PML) is reported, detected at autopsy of a 30-year-old patient. The clinical picture was characterized by a progressive course of mental deterioration and ingravescent neurological symptoms. The patient was HIV-negative. He died of bronchopneumonia, after a clinical course of 13 months. Autopsy disclosed pulmonary tuberculosis with involvement of regional lymph nodes. In the brain, besides numerous PML-foci of varying age and structure, a pleomorphic astrocytoma was found in the white matter of the right parietal lobe. In the brain stem glial proliferation resembling diffuse gliomatosis was also present. In situ hybridization revealed Papova-virus (JCV) in oligoglial nuclei, but not in neoplastic astrocytes. This is the third report on the concomitant occurrence of PML and glioma in man.

Cerebral astrocytoma in association with HIV infection

Cerebral astrocytoma has been found in two patients with AIDS related conditions. The fortuity of this unusual association is discussed, insofar as immunosuppression could favour the growth of certain neoplasms.

Association of polyomaviruses JC, SV40, and BK with human brain tumors

Human brain tumors of 11 different types were analyzed by Southern blot analysis for the presence of JCV, SV40, and BKV. In 21 tumor specimens examined with JCV- and SV40-specific probes no positive hybridizations were obtained. Analysis for BKV DNA, however, revealed the presence of BKV-specific sequences in 11 of 24 tumor specimens. No hybridization was found in DNA from CNS tissues from different areas of 29 individuals without CNS tumors. The BKV DNA sequences were associated with high molecular weight cellular DNA, suggesting a chromosomal location. These data provide evidence for the involvement of BKV in the development of human brain tumors.

Microbial oncogenesis

For more than a century, medical investigators have sought to incriminate microorganisms in the cause of cancer. The first scientific evidence of such a relationship came in 1911, with the first successful induction of a tumor using a cell-free extract. Since that time, considerable data have accrued linking retroviruses, herpes viruses, the hepatitis B virus, papovaviruses, and adenoviruses to various malignant neoplasms. There is also increasing evidence that certain bacteria and parasites participate as cofactors in the development of some cancers. Although proof of cause-and-effect relationships has been difficult to obtain, there can be little doubt that microorganisms occasionally play pivotal roles in the origin of some cancers. Whether attempted intervention against these cancers is best directed against the oncogenic microorganisms themselves or against other environmental cofactors is not yet clear. Nevertheless, the successful application of tumor vaccines in the prevention of Marek's disease in chickens and in modifying the outcome of oncogenic herpesvirus infections in nonhuman primates offers hope of at least limited application of microbial vaccines in the prevention of human cancer.

The correlation of neoplastic vulnerability with central neuroepithelial cytogeny and glioma differentiation

The vulnerability of neuroepithelial cells in the central nervous system (CNS) to neoplastic transformation results from the interaction of several factors: the existence of a reserve population of stem cells, the capability of differentiated cells to reenter the kinetic cycle, the number of replicating cells at risk at a particular time, the length of time during which a particular cell population remains in the cycle, the state of differentiation and the further differentiation potential of that population, and the steps of differentiation that are achieved in successive cell generations. This concept explains many aspects of CNS tumor incidence and the relationship of central neuroepithelial embryonal tumors to tumors of adult cell type. The incidence of different types of central neuroepithelial tumors can be correlated with the width of the window of neoplastic vulnerability. Examples illustrating the existence of only a narrow window include such rare tumors as medulloepitheliomas, cerebral neuroblastomas, gangliogliomas and ependymoblastomas. By contrast, cerebellar medulloblastomas, astrocytomas, mixed astrocytomas and oligodendrogliomas, and glioblastomas exemplify instances in which a relatively wider window of vulnerability exists in the light of cellular neuro-ontogeny and of the capacity of glial cells for postnatal replication. The relationship that may occasionally be established between the development of a glioma and the production of cellular gliosis such as may follow brain injury or accompany multiple sclerosis can also be viewed in the light of that concept. Increasing awareness is needed concerning the development of postradiation gliomas, in particular after the apparently successful treatment of acute lymphocytic leukemia.