Association of BK and JC Human Polyomaviruses and SV40 with Human Tumors

DNA detection of JC and BK virus in archival urine cytospin slides

To identify decoy cells, cytological examination was performed in urine cytospin slides. Decoy cells are related to Polyomaviruses (JC virus [JCV] and BK virus [BKV]), which are recognized worldwide due to potential infection and morbidity in kidney transplant recipients. Cytologically, it is difficult to evaluate the cytopathic effect of JCV and BKV in urine of patients with urothelial neoplasia. For this reason, there is a need for molecular approaches. To evaluate the incidence of BKV and JCV DNA in archival slides of urine cytospin material with benign and malignant characteristics. A total of 176 urine specimens were used for cytological examination of neoplastic or decoy cells. The samples were analyzed for the presence of JCV and BKV, by polymerase chain reaction (PCR) in DNA Isolated from archival slides of urine cytospin material. A typical samples (n = 48) were compared with the remaining 128 samples without atypia/neoplasia for the presence of JCV or BKV DNA. A statistically nonsignificant result was observed correlating the presence of JCV or BKV. The results show that DNA Isolated from archival slides of urine cytospin material can be used for detection of BKV and JCV.

Identification in human brain tumors of DNA sequences specific for SV40 large T antigen

Simian virus 40 (SV40) sequences have recently been identified in a variety of human neoplasms, including mesothelioma, osteosarcoma, and brain tumors, but significant discrepancies exist regarding the frequency at which this occurs. The SV40 genome is 70% homologous to JC and BK, two related polyomaviruses that are highly prevalent in humans and which may cause in immune-compromised patients progressive multifocal leukoencephalopathy (PML) and cystitis, respectively. We have established a specific and sensitive method to identify SV40 sequence in DNA extracted from histological sections, using PCR followed by Southern hybridization to probes specific to the large T region. We found SV40 large T antigen sequences in all brain tumor types investigated. High frequencies were found in low-grade astrocytomas, anaplastic astrocytomas and secondary glioblastomas derived thereof (13/22, 59%) while somewhat lower frequencies were found in gemistocytic astrocytomas (9/28, 32%) and oligodendrogliomas (3/12, 25%). Primary glioblastomas, giant cell glioblastomas, and gliosarcomas, which clinically develop de novo, contained SV40 sequences in 11-25% of cases. Presence of viral DNA was also observed in pediatric brain tumors, including ependymomas (9/16, 56%), choroid plexus papillomas (6/16, 38%), and medulloblastomas (5/17, 29%). In 8 tumor biopsies with SV40 sequences, the adjacent normal brain tissue was also analyzed but was devoid of viral DNA in all but one case. BK and JC virus sequences were rarely detected, the overall frequencies being 3% and 2%, respectively. It remains to be shown whether the presence of SV40 contributes significantly to malignant transformation or whether certain human neoplasms provide a microenvironment that favors viral replication in humans with latent SV40 infection.

No evidence for simian virus 40 DNA sequences in malignant non-Hodgkin lymphomas

DNA sequences coding for simian virus 40 (SV40) large T antigen have been detected at different frequencies in human non-Hodgkin's lymphomas (NHL) by PCR techniques as well as immunohistochemistry. A highly sensitive quantitative real-time PCR specific for a sequence of SV40 large T antigen was established to test whether SV40 DNA is present in malignant lymphomas of German patients. Thirty-three lymph node samples obtained from 27 patients with NHL and 6 patients with Hodgkin's disease (HD) were tested in addition to 48 samples of peripheral blood mononuclear cells (PBMNC) from patients with NHL containing between 0.1% and >90% circulating lymphoma cells determined by PCR. Fourteen lymph nodes obtained from patients with other diseases than malignant lymphomas and 47 PBMNC samples from healthy volunteers served as controls. All samples from patients with malignant lymphomas and all controls were negative for SV40 DNA by quantitative real-time. In contrast, EBV-DNA could be detected in 29 of 46 DNA preparations isolated from lymph nodes (63%) and in 20 of 47 DNA preparations from PBMNC. EBV-positive samples contained between 5 and 80,000 EBV copies per 100,000 cells. Our results do not support the hypothesis that SV40 plays a major role in the etiology of malignant lymphomas and, in addition, they exclude a clonal SV 40 infection of malignant lymphoma cells in all samples investigated.

Oncogenic transformation by BK virus and association with human tumors

BK virus (BKV), a human polyomavirus closely related to JC virus and Simian Virus 40, is ubiquitous in human populations worldwide. After primary infection, BKV establishes a lifelong latent infection in many organs. BKV transforms rodent cells to the neoplastic phenotype and is highly oncogenic in rodents. This review considers the oncogenic potential of BKV in humans and its possible involvement in human tumors. BKV sequences and T antigen (Tag) are detected in several types of human neoplasms, although the viral load is generally low, with less than one copy of the viral genome per cell. The possible causative role of BKV in human oncogenesis rests on the ability of BKV Tag to inactivate the functions of tumor suppressor proteins p53 and pRB family as well as on its ability to induce chromosomal aberrations in human cells. A 'hit and run' mechanism and secretion of paracrine growth factors by BKV Tag-positive cells, recruiting into proliferation neighboring and distant cells, are discussed as possible BKV pathogenic elements in human oncogenesis.

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.

Episomal vectors for gene expression in mammalian cells

An important reason for preferring mammalian cells for heterologous gene expression is their ability to make authentic proteins containing post-translational modifications similar to those of the native protein. The development of expression systems for mammalian cells has been ongoing for several years, resulting in a wide variety of effective expression vectors. The aim of this review is to highlight episomal expression vectors. Such episomal plasmids are usually based on sequences from DNA viruses, such as BK virus, bovine papilloma virus 1 and Epstein-Barr virus. In this review we will mainly focus on the improvements made towards the usefulness of these systems for gene expression studies and gene therapy.