DNA from KI, WU and Merkel cell polyomaviruses is not detected in childhood central nervous system tumours or neuroblastomas

Merkel Cell Polyomavirus (MCPyV) and Its Possible Role in Head and Neck Cancers

Despite significant progress in its prevention, diagnosis, and treatment, head and neck cancer (HNC) remains a major global health issue due to its multifactorial pathogenesis. Indeed, HNCs have been found to be associated with different environmental and lifestyle factors, as well as with infection with oncogenic viruses. To date, seven viruses are recognized for their tumorigenic properties and have been proposed as implicated in HNC development, including Merkel Cell Polyomavirus (MCPyV). MCPyV is well recognized as the major etiological agent of Merkel cell carcinoma (MCC), a rare but rapidly metastasizing skin neoplasm. Specifically, in almost 80% of MCC cases, viral genome integration occurs, and a truncated form of Large T Antigen (tLT) is expressed. Although MCC is a rare cancer, MCPyV is a ubiquitous virus, widely distributed among the human population. Therefore, a plausible role of the virus has been proposed, even for other tumors. The current review provides an overview of the available data describing the presence of MCPyV in non-MCC tumors, such as HNCs, with the aim of elucidating the potential contribution of MCPyV to oral cancer. Understanding the role of viral infections in the etiology of cancer opens up the opportunity for developing preventive measures and targeted therapies that effectively address HNC progression while reducing treatment-related side effects.

Merkel Cell Polyomavirus (MCPyV) and Cancers: Emergency Bell or False Alarm?

Merkel cell polyomavirus (MCPyV), the sole member of Polyomavirus associated with oncogenesis in humans, is the major causative factor of Merkel cell carcinoma (MCC), a rare, neuroendocrine neoplasia of the skin. Many aspects of MCPyV biology and oncogenic mechanisms remain poorly understood. However, it has been established that oncogenic transformation is the outcome of the integration of the viral genome into the host DNA. The high prevalence of MCPyV in the population, along with the detection of the virus in various human tissue samples and the strong association of MCPyV with the emergence of MCC, have prompted researchers to further investigate the role of MCPyV in malignancies other than MCC. MCPyV DNA has been detected in several different non-MCC tumour tissues but with significantly lower prevalence, viral load and protein expression. Moreover, the two hallmarks of MCPyV MCC have rarely been investigated and the studies have produced generally inconsistent results. Therefore, the outcomes of the studies are inadequate and unable to clearly demonstrate a direct correlation between cellular transformation and MCPyV. This review aims to present a comprehensive recapitulation of the available literature regarding the association of MCPyV with oncogenesis (MCC and non-MCC tumours).

Merkel cell polyomavirus and non-Merkel cell carcinomas: guilty or circumstantial evidence?

Merkel cell polyomavirus (MCPyV) is the major causative factor of the rare but aggressive cancer, Merkel cell carcinoma (MCC). Two characteristics of MCPyV-positive MCCs are integration of the viral genome and expression of a truncated version of one of its oncogenic proteins, namely large T antigen. The strong association of MCPyV with MCC development has incited researchers to further investigate a possible role of this virus in other cancers. However, many of the examples displaying the presence of the virus in the various non-MCC cancers are not able to clearly demonstrate a direct connection between cellular transformation and the presence of the virus. The prevalence of the virus is significantly lower in non-MCC cancers compared to MCCs, with a lower level of viral load and sparse viral protein expression. Moreover, the state of the viral genome, and whether a truncated large T antigen is expressed, has rarely been investigated. Nonetheless, considering the strong oncogenic potential of MCPyV proteins in MCC, the plausible contribution of MCPyV to transformation and cancer growth in non-MCC tumors cannot be ruled out. Furthermore, the absence of MCPyV in cancers does not exclude a hit-and-run mechanism, or the oncoproteins of MCPyV may potentiate the neoplastic process mediated by co-infecting oncoviruses such as high-risk human papillomaviruses and Epstein-Barr virus. The current review is focusing on the available data describing the presence of MCPyV in non-MCC tumors, with an aim to provide a comprehensive overview of the corresponding literature and to discuss the potential contribution of MCPyV to non-MCC cancer in light of this.

Analyses of FGFR3 and PIK3CA mutations in neuroblastomas and the effects of the corresponding inhibitors on neuroblastoma cell lines

Fibroblast growth factor receptor (FGFR)3 and phosphatidylinositol‑4,5‑bisphosphate 3‑kinase, catalytic subunit alpha (PIK3CA) mutations are found in various types of cancer, such as urinary bladder cancer, human papillomavirus‑positive tonsillar and base of the tongue squamous cell carcinoma, breast cancer and some childhood sarcomas. Several drugs can target these genes, some of which have been used for the treatment of urinary bladder cancer. Much less is known about childhood cancer. For this reason, the present study investigated the presence of such mutations in neuroblastomas (NBs) and tested NB cell lines for sensitivity to FGFR and phosphoinositide 3‑kinase (PI3K) inhibitors. In total, 29 NBs were examined for the presence of the three most common FGFR3 and PIK3CA mutations using a competitive allele‑specific TaqMan PCR (CAST‑PCR). Furthermore, the SK‑N‑AS, SK‑N‑BE(2)‑C, SK‑N‑DZ, SK‑N‑FI and SK‑N‑SH NB cell lines (where SK‑N‑DZ had a deletion of PIK3C2G, none had FGFR mutations according to the Cancer Program's Dependency Map, but some were chemoresistant), were tested for sensitivity to FGFR (AZD4547) and PI3K (BEZ235 and BKM120) inhibitors by viability, cytotoxicity, apoptosis and proliferation assays. CAST‑PCR detected one FGFR3 mutation in 1/29 NBs. Following treatment with FGFR and PI3K inhibitors, a decrease in viability and proliferation was observed in the majority, but not all, the cell lines. Following combination treatment with both drugs, the sensitivity of all cell lines was increased. On the whole, the findings of this study demonstrate that FGFR3 and PIK3CA mutations are uncommon in patients with NB. However, certain NB cell lines are rather sensitive to both FGFR and PI3K inhibitors alone, and even more so when the different drugs are used in combination.

Viral Sequences Detection by High-Throughput Sequencing in Cerebrospinal Fluid of Individuals with and without Central Nervous System Disease

Meningitis, encephalitis, and myelitis are various forms of acute central nervous system (CNS) inflammation, which can coexist and lead to serious sequelae. Known aetiologies include infections and immune-mediated processes. Despite advances in clinical microbiology over the past decades, the cause of acute CNS inflammation remains unknown in approximately 50% of cases. High-throughput sequencing was performed to search for viral sequences in cerebrospinal fluid (CSF) samples collected from 26 patients considered to have acute CNS inflammation of unknown origin, and 10 patients with defined causes of CNS diseases. In order to better grasp the clinical significance of viral sequence data obtained in CSF, 30 patients without CNS disease who had a lumbar puncture performed during elective spinal anaesthesia were also analysed. One case of human astrovirus (HAstV)-MLB2-related meningitis and disseminated infection was identified. No other viral sequences that can easily be linked to CNS inflammation were detected. Viral sequences obtained in all patient groups are discussed. While some of them reflect harmless viral infections, others result from reagent or sample contamination, as well as index hopping. Altogether, this study highlights the potential of high-throughput sequencing in identifying previously unknown viral neuropathogens, as well as the interpretation issues related to its application in clinical microbiology.

Human polyomaviruses and cancer: an overview

The name of the family Polyomaviridae, derives from the early observation that cells infected with murine polyomavirus induced multiple (poly) tumors (omas) in immunocompromised mice. Subsequent studies showed that many members of this family exhibit the capacity of mediating cell transformation and tumorigenesis in different experimental models. The transformation process mediated by these viruses is driven by viral pleiotropic regulatory proteins called T (tumor) antigens. Similar to other viral oncoproteins T antigens target cellular regulatory factors to favor cell proliferation, immune evasion and downregulation of apoptosis. The first two human polyomaviruses were isolated over 45 years ago. However, recent advances in the DNA sequencing technologies led to the rapid identification of additional twelve new polyomaviruses in different human samples. Many of these viruses establish chronic infections and have been associated with conditions in immunosuppressed individuals, particularly in organ transplant recipients. This has been associated to viral reactivation due to the immunosuppressant therapy applied to these patients. Four polyomaviruses namely, Merkel cell polyomavirus (MCPyV), Trichodysplasia spinulosa polyomavirus (TSPyV), John Cunningham Polyomavirus (JCPyV) and BK polyomavirus (BKPyV) have been associated with the development of specific malignant tumors. However, present evidence only supports the role of MCPyV as a carcinogen to humans. In the present review we present a summarized discussion on the current knowledge concerning the role of MCPyV, TSPyV, JCPyV and BKPyV in human cancers.

Survey of KI, WU, MW, and STL Polyomavirus in Cancerous and Non-Cancerous Lung Tissues

BACKGROUND/AIMS

The pathogenesis of the human polyomavirus (PyV) KI, WU, MW, and STL has not been elucidated yet. Respiratory transmission is suggested, but the site of the replication, tissue, and cell tropism is not clarified. KIPyV and WUPyV DNA and/or antigen were detected in normal lung tissues previously by others. In fact, a KIPyV DNA sequence was found in lung cancer samples. Up to date, there is no publication about the DNA prevalence of MWPyV and STLPyV neither in normal nor in cancerous lung tissues. The aim of the present study was to examine the DNA prevalence of these polyomaviruses in cancerous and non-cancerous lung tissue samples, in order to study the possible site for viral replication and/or persistence, and the potential association of these viruses with lung carcinogenesis as well.

METHODS

100 cancerous and 47 non-cancerous, formalin-fixed paraffin-embedded lung tissue samples were studied for KIPyV, WUPyV, MWPyV, and STLPyV by real-time PCR.

RESULTS AND CONCLUSION

Neither of the viruses was found in samples from small-cell, non-small-cell (adenocarcinoma, squamous-cell carcinoma and large-cell neuroendocrine lung cancer), mixed-type and non-differentiated lung carcinoma, and non-cancerous lung tissues (from patients with pneumonia, emphysema and fibrosis).

Entry, infection, replication, and egress of human polyomaviruses: an update

Polyomaviruses (PyVs), belonging to the family Polyomaviridae, are a group of small, nonenveloped, double-stranded, circular DNA viruses widely distributed in the vertebrates. PyVs cause no apparent disease in adult laboratory mice but cause a wide variety of tumors when artificially inoculated into neonates or semipermissive animals. A few human PyVs, such as BK, JC, and Merkel cell PyVs, have been unequivocally linked to pathogenesis under conditions of immunosuppression. Infection is thought to occur early in life and persists for the lifespan of the host. Over evolutionary time scales, it appears that PyVs have slowly co-evolved with specific host animal lineages. Host cell surface glycoproteins and glycolipids seem to play a decisive role in the entry stage of viral infection and in channeling the virions to specific intracellular membrane-bound compartments and ultimately to the nucleus, where the genomes are replicated and packaged for release. Therefore the transport of the infecting virion or viral genome to this site of multiplication is an essential process in productive viral infection as well as in latent infection and transformation. This review summarizes the major findings related to the characterization of the nature of the interactions between PyV and host protein and their impact in host cell invasion.

No Evidence of Human Polyomavirus 9, WU and KI DNA in Kidney and Urinary Bladder Tumour Tissue Samples

BACKGROUND/AIMS

The oncogenic potential of human polyomaviruses (HPyVs) has been proposed, but so far only Merkel cell carcinoma polyomavirus seems to be associated with a human tumour. The role of BK polyomavirus (BKPyV) in human tumourigenesis remains controversial. BKPyV establishes persistent infection in the urinary tract, and renal and bladder neoplasms have been studied extensively, but conflicting prevalence data are reported. KI, WU and HPyV9 were detected in urine samples suggesting that these viruses may also infect the urinary tract, but their presence in urinary tract tumours has not been studied. The aim of this work was to examine the prevalence of KIPyV, WUPyV, HPyV9 and BKPyV by PCR in renal and bladder neoplasms.

METHODS

A total of 190 formalin-fixed paraffin-embedded renal neoplasms, bladder cancer and kidney biopsy samples were analysed for the presence of BKPyV, KIPyV, WUPyV and HPyV9 DNA by real-time and nested PCR.

RESULTS

Amplifiable DNA was extracted from all the samples, but none of the studied viruses were detected in benign renal neoplasia (0/23), malignant renal tumours (0/89) or bladder cancer (0/76).

CONCLUSION

Our study did not find any evidence that BKPyV, KIPyV, WUPyV or HPyV9 are associated with bladder and renal tumours.

Detection of Merkel cell polyomavirus large T-antigen sequences in human central nervous system tumors

Despite decades of epidemiological investigation, little is known about the etiology of the central nervous system (CNS) tumors, and few well-established risk factors have been recognized. This study tested the presence of Merkel cell polyomavirus (MCPyV), the only member of the Polyomaviridae family convincingly linked to human cancer, in diverse CNS malignancies. In total, 58 CNS tumor biopsies were analyzed for the MCPyV large T-antigen (LT-Ag) gene by quantitative real-time PCR. Merkel cell polyomavirus LT-Ag DNA load was determined as viral copies per cell and viral copies per microliter of purified genomic DNA from CNS tumor samples. The MCPyV LT-Ag sequence was detected in 34 (58.6%) of the 58 tested samples. Viral LT-Ag was quantified in 19.0% of schwannomas, 13.8% of meningiomas, and 5.2% of pituitary adenomas. The difference between MCPyV positivity in different types of CNS malignancies was not statistically significant (P = 0.066). The mean LT-Ag copy number in 34 positive samples was 744.5 ± 737.7 and 0.056 × 10(-3)  ± 0.091 × 10(-3) per microliter and per cell, respectively. Among MCPyV-positive CNS tumors, the mean MCPyV copy number was higher in meningiomas (993.8 ± 853.2 copy per microliter and 0.098 × 10(-3)  ± 0.108 × 10(-3) copy per cell). Multiple linear regression analysis revealed statistically significant difference in MCPyV copy number between meningioma and other CNS tumor types, when the model was adjusted for age and sex (P = 0.024). This study shows the first evidence of the detection of MCPyV LT-Ag sequence at a low copy number in human CNS tumors.

Early and late promoters of BK polyomavirus, Merkel cell polyomavirus, Trichodysplasia spinulosa-associated polyomavirus and human polyomavirus 12 are among the strongest of all known human polyomaviruses in 10 different cell lines

Recently, 11 new human polyomaviruses (HPyVs) have been isolated and named KI, WU, Merkel cell polyomavirus (MCPyV), HPyV6,  -7,  -9,  -10 and  -12, Trichodysplasia spinulosa-associated polyomavirus (TSPyV), STLPyV and NJPyV-2013. Little is known about cell tropism of the novel HPyVs, and cell cultures allowing virus propagation are lacking. Because viral tropism partially depends on the interaction of cellular transcription factors with the viral promoter, we monitored the promoter activity of all known HPyVs. Therefore, we compared the relative early and late promoter activity of the BK polyomavirus (BKPyV) (WW strain) with the corresponding activities of the other HPyVs in 10 different cell lines derived from brain, colon, kidney, liver, lung, the oral cavity and skin. Our results show that the BKPyV, MCPyV, TSPyV and HPyV12 early promoters displayed the strongest activity in most cell lines tested, while the remaining HPyV had relative low early promoter activity. HPyV12 showed the highest late promoter activity of all HPyVs in most cell lines, but also the BKPyV, MCPyV and TSPyV late promoters belonged to the stronger ones among HPyVs. The HPyVs with weak early promoter activity had in general also weak late promoter activity, except for HPyV10 whose late promoter was relatively strong in six of the 10 cell lines. A 20 bp deletion in the promoter of an HPyV12 variant significantly affected both early and late promoter activity in most cell lines. In conclusion, our findings suggest which cell lines may be suitable for virus propagation and may give an indication of the cell tropism of the HPyVs.

The role of Merkel cell polyomavirus and other human polyomaviruses in emerging hallmarks of cancer

Polyomaviruses are non-enveloped, dsDNA viruses that are common in mammals, including humans. All polyomaviruses encode the large T-antigen and small t-antigen proteins that share conserved functional domains, comprising binding motifs for the tumor suppressors pRb and p53, and for protein phosphatase 2A, respectively. At present, 13 different human polyomaviruses are known, and for some of them their large T-antigen and small t-antigen have been shown to possess oncogenic properties in cell culture and animal models, while similar functions are assumed for the large T- and small t-antigen of other human polyomaviruses. However, so far the Merkel cell polyomavirus seems to be the only human polyomavirus associated with cancer. The large T- and small t-antigen exert their tumorigenic effects through classical hallmarks of cancer: inhibiting tumor suppressors, activating tumor promoters, preventing apoptosis, inducing angiogenesis and stimulating metastasis. This review elaborates on the putative roles of human polyomaviruses in some of the emerging hallmarks of cancer. The reciprocal interactions between human polyomaviruses and the immune system response are discussed, a plausible role of polyomavirus-encoded and polyomavirus-induced microRNA in cancer is described, and the effect of polyomaviruses on energy homeostasis and exosomes is explored. Therapeutic strategies against these emerging hallmarks of cancer are also suggested.

Merkel cell polyomavirus infection in childhood: current advances and perspectives

Merkel cell polyomavirus (MCPyV) is a newly discovered human small, non-enveloped, double-stranded DNA virus, which was classified into the Polyomaviridae family. MCPyV is acquired in early childhood through close contact involving respiratory tract secretions and causes a widespread, previously unrecognised, asymptomatic infection in both immunocompetent children and adults. To date, several researchers have established that MCPyV is the potential causative agent of Merkel cell carcinoma, a relatively rare but life-threatening skin cancer of neuroendocrine origin. In our review, we present current data on the presence of MCPyV DNA in children and address the possible role that the respiratory tract plays in the route of viral transmission. Future studies are required to fully elucidate the potential implications of MCPyV infection in children.

Atypical progressive multifocal leukoencephalopathy in a patient with antisynthetase syndrome

Antisynthetase syndrome is a disorder belonging to the dermatomyositis/polymyositis group, with high rates of morbidity and mortality. We herein present the case of a 71-year-old man who was diagnosed with antisynthetase syndrome and treated with rituximab. Almost three years later, the patient showed right-sided hemiparesis that ultimately progressed to complete hemiplegia and advancing cognitive deterioration with a poor clinical outcome. The neuropathological diagnosis was progressive multifocal leukoencephalopathy. Treatment with rituximab for antisynthetase syndrome itself plays a fundamental role in the development of infectious complications.

Human polyomaviruses in disease and cancer

Today the human polyomavirus (HPyV) family consists of 10 members, BK virus (BKV) and JC virus (JCV) isolated 40 years ago and the more recently identified KI virus (KIPyV), WU virus (WUPyV), Merkel cell polyomavirus (MCPyV), HPyV6, HPyV7, trichodysplasia spinulosa virus (TSPyV), HPyV9 and MWPyV. Serological studies suggest that HPyVs subclinically infect the general population with rates ranging from 35% to 90%. However, significant disease is only observed in patients with impaired immune functions. Thus, BKV has been linked to hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplantation and PyV-associated nephropathy (PyVAN) after kidney transplantation; JCV to progressive multifocal leukoencephalopathy (PML) in HIV-AIDS, hematological diseases and in autoimmune diseases treated with certain lymphocyte-specific antibodies. KIPyV and WUPyV have been found in the respiratory tract, HPyV6 and 7 in the skin, and HPyV9 in serum and skin, and MWPyV in stools and skin, but so far none of these PyVs have been linked to any disease. TSPyV, on the other hand, was identified in trichodysplasia spinulosa, a rare skin disease characterized by virus-induced lytic as well as proliferative tumor-like features that is observed in immune-suppressed transplant patients. In contrast to all the other HPyVs so far, MCPyV is unique in its association with a cancer, Merkel cell carcinoma, which is a rare skin cancer arising in the elderly and chronically immunosuppressed individuals. The discovery of the new HPyVs has revived interest in the Polyomaviridae and their association to human disease and cancer. In this review, we summarize knowledge about this expanding family of human pathogens.

Prevalence of polyomaviruses and links with human diseases

The simian virus 40 and murine polyomaviruses were shown to be DNA tumor viruses in their natural hosts and/or heterologous experimental hosts in the mid-20th Century. The first two human polyomaviruses, the BK polyomavirus and JC polyomavirus, were discovered in 1971 and were shown to induce severe disease in immunocompromised patients, but their involvement in human cancers is still a matter for debate. The discovery of a polyomavirus associated with Merkel cell carcinoma (Merkel cell polyomavirus) in 2008 resulted in a renewed interest in the Polyomaviridae family, leading to the discovery of new human polyomaviruses. This review addresses the involvement of the nine human polyomaviruses and simian virus 40 in human diseases, with a particular focus on their prevalence and the humoral response directed against structural antigens in the general population and in subjects presenting specific diseases.

Human polyomaviruses in skin diseases

Polyomaviruses are a family of small, nonenveloped viruses with a circular double-stranded DNA genome of ∼5,000 base pairs protected by an icosahedral protein structure. So far, members of this family have been identified in birds and mammals. Until 2006, BK virus (BKV), JC virus (JCV), and simian virus 40 (SV40) were the only polyomaviruses known to circulate in the human population. Their occurrence in individuals was mainly confirmed by PCR and the presence of virus-specific antibodies. Using the same methods, lymphotropic polyomavirus, originally isolated in monkeys, was recently shown to be present in healthy individuals although with much lower incidence than BKV, JCV, and SV40. The use of advanced high-throughput sequencing and improved rolling circle amplification techniques have identified the novel human polyomaviruses KI, WU, Merkel cell polyomavirus, HPyV6, HPyV7, trichodysplasia spinulosa-associated polyomavirus, and HPyV9. The skin tropism of human polyomaviruses and their dermatopathologic potentials are the focus of this paper.

High Levels of Antibodies Against Merkel Cell Polyomavirus Identify a Subset of Patients With Merkel Cell Carcinoma With Better Clinical Outcome

Purpose

A new human polyomavirus, Merkel cell polyomavirus (MCV), was identified in 2008 in tumor tissue of patients with Merkel cell carcinoma (MCC), a relatively rare human skin cancer. In this study, we investigated patients with MCC and controls for the presence of antibodies against MCV and their association with clinical characteristics.

Patients and Methods

Antibodies against MCV were investigated by enzyme-linked immunosorbent assay in 68 patients with MCC and 82 controls using VP1 virus-like particles produced in insect cells.

Results

Antibodies against MCV were detected in all patients with MCC and in 85% of controls. However, high antibody titers (> 10,000) were rarely observed in controls (7.3%) and they were detected in 64.7% of patients with MCC (P < .001) in contrast to the absence of VP1 expression in tumor samples. In addition, the geometric mean titer of anti-MCV in patients with MCC was around 14 times higher than that observed in MCV-positive controls (P < .001) and was not correlated with tumor viral load. High antibody titers were not found to be associated with any subject or tumor characteristics, but better progression-free survival was observed in patients with high antibody titers (hazard ratio, 4.6; 95% CI, 1.7 to 12.2; P = .002).

Conclusion

High titers of MCV antibodies in a much higher proportion of patients with MCC than in controls confirmed the association between MCV infection and MCC. The findings also indicated that a better progression-free survival occurred in patients with high MCV antibody titers and suggested that there are at least two distinct etiologic causes of MCC.