JC virus T-antigen regulates glucose metabolic pathways in brain tumor cells

Interplay between cellular metabolism and DNA viruses

Viruses as intracellular pathogens take over the host metabolism and reprogram to facilitate optimal virus production. DNA viruses can cause alterations in several metabolic pathways, including aerobic glycolysis also known as the Warburg effect, pentose phosphate pathway activation, and amino acid catabolism such as glutaminolysis, nucleotide biosynthesis, lipid metabolism, and amino acid biosynthesis. The available energy for productive infection can be increased in infected cells via modification of different carbon source utilization. This review discusses the metabolic alterations of the DNA viruses that will be the basis for future novel therapeutic approaches.

The oncogenic roles of JC polyomavirus in cancer

JC polyomavirus (JCPyV) belongs to the human polyomavirus family. Based on alternative splicing, the early region encodes the large and small T antigens, while the late region encodes the capsid structural proteins (VP1, VP2, and VP3) and the agnoprotein. The regulatory transcription factors for JCPyV include Sp1, TCF-4, DDX1, YB-1, LCP-1, Purα, GF-1, and NF-1. JCPyV enters tonsillar tissue through the intake of raw sewage, inhalation of air droplets, or parent-to-child transmission. It persists quiescently in lymphoid and renal tissues during latency. Both TGF-β1 and TNF-α stimulates JCPyV multiplication, while interferon-γ suppresses the process. The distinct distribution of caspid receptors (α-2, 6-linked sialic acid, non-sialylated glycosaminoglycans, and serotonin) determines the infection capabilities of JCPyV virions, and JCPyV entry is mediated by clathrin-mediated endocytosis. In permissive cells, JCPyV undergoes lytic proliferation and causes progressive multifocal leukoencephalopathy, while its DNA is inserted into genomic DNA and leads to carcinogenesis in non-permissive cells. T antigen targets p53, β-catenin, IRS, Rb, TGF-β1, PI3K/Akt and AMPK signal pathways in cancer cells. Intracranial injection of T antigen into animals results in neural tumors, and transgenic mice develop neural tumors, lens tumor, breast cancer, gastric, Vater’s, colorectal and pancreatic cancers, insulinoma, and hepatocellular carcinoma. Additionally, JCPyV DNA and its encoded products can be detected in the brain tissues of PML patients and brain, oral, esophageal, gastric, colorectal, breast, cervical, pancreatic, and hepatocellular cancer tissues. Therefore, JCPyV might represent an etiological risk factor for carcinogenesis and should be evaluated for early prevention, diagnosis, and treatment of cancers.

The Oncogenic Effects, Pathways, and Target Molecules of JC Polyoma Virus T Antigen in Cancer Cells

JC polyoma virus (JCPyV) is a ubiquitous polyoma virus that infects the individual to cause progressive multifocal leukoencephalopathy and malignancies. Here, we found that T-antigen knockdown suppressed proliferation, glycolysis, mitochondrial respiration, migration, and invasion, and induced apoptosis and G₂ arrest. The reverse was true for T-antigen overexpression, with overexpression of Akt, survivin, retinoblastoma protein, β-catenin, β-transducin repeat-containing protein (TRCP), and inhibitor of growth (ING)1, and the underexpression of mammalian target of rapamycin (mTOR), phosphorylated (p)-mTOR, p-p38, Cyclin D1, p21, vascular endothelial growth factor (VEGF), ING2, and ING4 in hepatocellular and pancreatic cancer cells and tissues. In lens tumor cells, T antigen transcriptionally targeted viral carcinogenesis, microRNAs in cancer, focal adhesion, p53, VEGF, phosphoinositide 3 kinase-Akt, and Forkhead box O signaling pathways, fructose and mannose metabolism, ribosome biosynthesis, and choline and pyrimidine metabolism. At a metabolomics level, it targeted protein digestion and absorption, aminoacryl-tRNA biosynthesis, biosynthesis of amino acids, and the AMPK signal pathway. At a proteomic level, it targeted ribosome biogenesis in eukaryotes, citrate cycle, carbon metabolism, protein digestion and absorption, aminoacryl-tRNA biosynthesis, extracellular-matrix-receptor interaction, and biosynthesis of amino acids. In lens tumor cells, T antigen might interact with various keratins, ribosomal proteins, apolipoproteins, G proteins, ubiquitin-related proteins, RPL19, β-catenin, β-TRCP, p53, and CCAAT-enhancer-binding proteins in lens tumor cells. T antigen induced a more aggressive phenotype in mouse and human cancer cells due to oncogene activation, inactivation of tumor suppressors, and disruption of metabolism, cell adhesion, and long noncoding RNA-microRNA-target axes.

The Oncogenic Roles of JC Virus T Antigen in Breast Carcinogenesis

Purpose: JC virus (JCV) infects 80–90% of the population and results in progressive multifocal leukoencephalopathy upon immunodeficiency. The study aimed to pathologically clarify the oncogenic roles of T antigen in human breast cancers.

Methods: Breast cancer, dysplasia, and normal tissues were examined for T antigen of JCV by nested and real-time PCR. The positive rate or copy number of T antigen was compared with clinicopathological parameters of breast cancer. JCV existence was morphologically detected by immunohistochemistry and in situ PCR. T antigen was examined by Western blot using frozen samples of breast cancer and paired normal tissues.

Results: According to nested PCR, the positive rate of breast ductal or lobular carcinoma was lower than that of normal tissue (p < 0.05). T antigen existence was negatively correlated with E-cadherin expression and triple-negative breast cancer (p < 0.05), but positively correlated with lymph node metastasis and estrogen receptor and progestogen receptor expression (p < 0.05). Quantitative PCR showed that JCV copies were gradually decreased from normal, dysplasia to cancer tissues (p < 0.05). JCV T antigen copy number was lower in ductal adenocarcinoma than in normal tissue (p < 0.05), in line with in situ PCR and immunohistochemistry. JCV copies were negatively correlated with tumor size and E-cadherin expression (p < 0.05), but positively correlated with G grading of breast cancer (p < 0.05). Western blot also indicated weaker T antigen expression in breast cancer than normal tissues (p < 0.05).

Conclusion: JCV T antigen might play an important role in breast carcinogenesis. It can be employed as a molecular marker for the differentiation and aggressive behaviors of breast cancer.

Multifaceted Role of AMPK in Viral Infections

Viral pathogens often exploit host cell regulatory and signaling pathways to ensure an optimal environment for growth and survival. Several studies have suggested that 5'-adenosine monophosphate-activated protein kinase (AMPK), an intracellular serine/threonine kinase, plays a significant role in the modulation of infection. Traditionally, AMPK is a key energy regulator of cell growth and proliferation, host autophagy, stress responses, metabolic reprogramming, mitochondrial homeostasis, fatty acid β-oxidation and host immune function. In this review, we highlight the modulation of host AMPK by various viruses under physiological conditions. These intracellular pathogens trigger metabolic changes altering AMPK signaling activity that then facilitates or inhibits viral replication. Considering the COVID-19 pandemic, understanding the regulation of AMPK signaling following infection can shed light on the development of more effective therapeutic strategies against viral infectious diseases.

Selenium nanoparticles reduce glucose metabolism and promote apoptosis of glioma cells through reactive oxygen species-dependent manner

Gliomas are the most common, malignant, and lethal tumors in adults. Furthermore, gliomas are highly resistant to current chemotherapeutic drugs. Thus, new effective anticancer drugs for glioma are urgently needed. Selenium nanoparticles have been reported to have potent anti-tumor activity, although the specific mechanism is not fully understood. This study aimed to test the anti-tumor effect of selenium nanoparticles and its mechanism. We used selenium nanoparticles to treat commercial glioma cell lines, and patient-derived glioma cells, and then used the MTT assay to determine selenium nanoparticles effect against these. Apoptotic cell death was determined by annexin V-Fluos staining kit. Glucose uptake, lactate, and adenosine triphosphate production, together with hexokinase 2 and pyruvate kinase activities were measured to determine the glucose metabolism level. Reactive oxygen species production was tested using 2',7'-dichlorodihydrofluorescein diacetate. Our results showed that selenium nanoparticles had a potent cytotoxic effect in glioma cells, regardless of whether they were drug-resistant or not, whereas it showed less toxic effect in normal healthy cells. Further tests showed that selenium nanoparticles treatment leads to apoptotic cell death enhancement and glucose metabolism reduction, and this process was in a reactive oxygen species pathway-dependent manner. These results may provide a novel direction for glioma therapy in the future.

PAM (PIK3/AKT/mTOR) signaling in glia: potential contributions to brain tumors in aging

Despite a growing proportion of aged individuals at risk for developing cancer in the brain, the prognosis for these conditions remains abnormally poor due to limited knowledge of underlying mechanisms and minimal treatment options. While cancer metabolism in other organs is commonly associated with upregulated glycolysis (i.e. Warburg effect) and hyperactivation of PIK3/AKT/mTOR (PAM) pathways, the unique bioenergetic demands of the central nervous system may interact with these oncogenic processes to promote tumor progression in aging. Specifically, constitutive glycolysis and PIK3/AKT/mTOR signaling in glia may be dysregulated by age-dependent alterations in neurometabolic demands, ultimately contributing to pathological processes otherwise associated with PIK3/AKT/mTOR induction (e.g. cell cycle entry, impaired autophagy, dysregulated inflammation). Although several limitations to this theoretical model exist, the consideration of aberrant PIK3/AKT/mTOR signaling in glia during aging elucidates several therapeutic opportunities for brain tumors, including non-pharmacological interventions.

Emerging Roles and Therapeutic Interventions of Aerobic Glycolysis in Glioma

Glioma is the most common type of intracranial malignant tumor, with a great recurrence rate due to its infiltrative growth, treatment resistance, intra- and intertumoral genetic heterogeneity. Recently, accumulating studies have illustrated that activated aerobic glycolysis participated in various cellular and clinical activities of glioma, thus influencing the efficacy of radiotherapy and chemotherapy. However, the glycolytic process is too complicated and ambiguous to serve as a novel therapy for glioma. In this review, we generalized the implication of key enzymes, glucose transporters (GLUTs), signalings and transcription factors in the glycolytic process of glioma. In addition, we summarized therapeutic interventions via the above aspects and discussed promising clinical applications for glioma.

Effect of the Large and Small T-Antigens of Human Polyomaviruses on Signaling Pathways

Viruses are intracellular parasites that require a permissive host cell to express the viral genome and to produce new progeny virus particles. However, not all viral infections are productive and some viruses can induce carcinogenesis. Irrespective of the type of infection (productive or neoplastic), viruses hijack the host cell machinery to permit optimal viral replication or to transform the infected cell into a tumor cell. One mechanism viruses employ to reprogram the host cell is through interference with signaling pathways. Polyomaviruses are naked, double-stranded DNA viruses whose genome encodes the regulatory proteins large T-antigen and small t-antigen, and structural proteins that form the capsid. The large T-antigens and small t-antigens can interfere with several host signaling pathways. In this case, we review the interplay between the large T-antigens and small t-antigens with host signaling pathways and the biological consequences of these interactions.

Oncogenic virus-induced aerobic glycolysis and tumorigenesis

Enhanced glycolysis under normoxic conditions is known as aerobic glycolysis or the Warburg effect and is a hallmark of many tumors. Viral infection may also induce aerobic glycolysis as it is required for replication and survival. Tumor viruses inducing aerobic glycolysis and lactate production during latent infection suggest a potential role of virus-induced glycolysis in tumorigenesis. Virus or virus-encoded proteins regulate glucose uptake and lactate export, increase the activity of glycolytic enzymes, and modulate glucose metabolic signals. Accumulating evidence suggests that virus-induced glycolysis may facilitate cell growth, transformation, migration, and invasion, but its significance in tumorigenesis remains unclear. We summarize the effects of oncogenic viruses on the metabolic shift to aerobic glycolysis and discuss the possible association of this metabolic reprogramming with tumor development and progression.

Comparative proteomics reveals that YK51, a 4-Hydroxypandurantin-A analogue, downregulates the expression of proteins associated with dengue virus infection

Dengue is endemic throughout tropical and subtropical regions of the world. Currently, there is no clinically approved therapeutic drug available for this acute viral infection. Although the first dengue vaccine Dengvaxia has been approved for use in certain countries, it is limited to those without a previous dengue infection while the safety and efficacy of the vaccine in those elderly and younger children still need to be identified. Therefore, it is becoming increasingly important to develop therapeutics/drugs to combat dengue virus (DENV) infection. YK51 is a synthetic analogue of 4-Hydroxypandurantin A (a compound found in the crude extract of the rhizomes of Boesenbergia rotunda) that has been extensively studied by our research group. It has been shown to possess outstanding antiviral activity due to its inhibitory activity against NS2B/NS3 DENV2 protease. However, it is not known how YK51 affects the proteome of DENV infected cells. Therefore, we performed a comparative proteomics analysis to identify changes in protein expression in DENV infected HepG2 cells treated with YK51. Classical two-dimensional gel electrophoresis followed by protein identification using tandem mass spectrometry was employed in this study. Thirty proteins were found to be down-regulated with YK51 treatment. In silico analysis predicted that the down-regulation of eight of these proteins may inhibit viral infection. Our results suggested that apart from inhibiting the NS2B/NS3 DENV2 protease, YK51 may also be causing the down-regulation of a number of proteins that may be responsible in, and/or essential to virus infection. However, functional characterization of these proteins will be necessary before we can conclusively determine their roles in DENV infection.

Distribution and genetic diversity of the human polyomaviruses JC and BK in surface water and sewage treatment plant during 2009 in Porto Alegre, Southern Brazil

Abstract The human polyomaviruses JC and BK (JCPyV and BKPyV) are ubiquitous, species-specific viruses that belong to the family Polyomaviridae. These viruses are known to be excreted in human urine, and they are potential indicators of human wastewater contamination. In order to assess the distribution of both JCPyV and BKPyV in urban water samples collected from a sewage treatment plant (STP) and from a canalized water stream of Porto Alegre, Brazil, two nested-PCR assays were optimized and applied to the samples collected. The amplicons obtained were submitted to sequencing, and the sequences were analyzed with sequences of human polyomaviruses previously deposited in GenBank. Twelve out of 30 water samples (40%) were JCPyV positive, whereas six samples (20%) were BKPyV positive. The sequencing results confirmed the presence of JCPyV subtypes 1 and 3, whereas only BKPyV Ia and Ib were found. This study shows for the first time the presence of human polyomaviruses in surface water and in samples collected in a sewage treatment plant in southern Brazil.

DNA Tumor Viruses and Cell Metabolism

Viruses play an important role in cancerogenesis. It is estimated that approximately 20% of all cancers are linked to infectious agents. The viral genes modulate the physiological machinery of infected cells that lead to cell transformation and development of cancer. One of the important adoptive responses by the cancer cells is their metabolic change to cope up with continuous requirement of cell survival and proliferation. In this review we will focus on how DNA viruses alter the glucose metabolism of transformed cells. Tumor DNA viruses enhance “aerobic” glycolysis upon virus-induced cell transformation, supporting rapid cell proliferation and showing the Warburg effect. Moreover, viral proteins enhance glucose uptake and controls tumor microenvironment, promoting metastasizing of the tumor cells.

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.

Epidemiological trends of histopathologically WHO classified CNS tumors in developing countries: systematic review

BACKGROUND

Many developing countries are lagging behind in reporting epidemiological data for individual central nervous system (CNS) tumors. This paper aimed to elicit patterns for the epidemiology of individual World Health Organization (WHO) classified CNS tumors in countries registered by WHO as "developing".

MATERIALS AND METHODS

Cyber search was carried out through 66 cancer networks/registries and 181 PubMed published papers that reported counts of CNS tumors for the period of 2009-2012. The relationship between the natural log of incidence Age Standardized Rate (ASR) reported by Globocan and Latitude/ Longitude was investigated.

RESULTS

Registries for 21 countries displayed information related to CNS tumors. In contrast tends for classified CNS tumor cases were identified for 38 countries via 181 PubMed publications. Extracted data showed a majority of unclassified reported cases [PubMed (38 countries, 45.7%), registries (21 countries, 96.1%)]. For classified tumors, astrocytic tumors were the most frequently reported type [PubMed (38 countries, 1,245 cases, 15.7%), registries (21 countries, 627 cases, 1.99%]. A significant linear regression relationship emerged between latitudes and reported cases of CNS tumors.

CONCLUSIONS

Previously unreported trends of frequencies for individually classified CNS tumors were elucidated and a possible link of CNS tumors occurrence with geographical location emerged.

Analysis of JC virus DNA replication using a quantitative and high-throughput assay

Progressive Multifocal Leukoencephalopathy (PML) is caused by lytic replication of JC virus (JCV) in specific cells of the central nervous system. Like other polyomaviruses, JCV encodes a large T-antigen helicase needed for replication of the viral DNA. Here, we report the development of a luciferase-based, quantitative and high-throughput assay of JCV DNA replication in C33A cells, which, unlike the glial cell lines Hs 683 and U87, accumulate high levels of nuclear T-ag needed for robust replication. Using this assay, we investigated the requirement for different domains of T-ag, and for specific sequences within and flanking the viral origin, in JCV DNA replication. Beyond providing validation of the assay, these studies revealed an important stimulatory role of the transcription factor NF1 in JCV DNA replication. Finally, we show that the assay can be used for inhibitor testing, highlighting its value for the identification of antiviral drugs targeting JCV DNA replication.

Triggering unfolded protein response by 2-Deoxy-D-glucose inhibits porcine epidemic diarrhea virus propagation

The unfolded protein response (UPR) is cyto-protective machinery elicited towards an influx of large amount of protein synthesis in the endoplasmic reticulum (ER). Extensive studies suggest that the UPR can also be activated during virus infection. In the present studies, we first evaluated if porcine epidemic diarrhea virus (PEDV) infection activated the UPR pathways. Electron microscopy analysis demonstrated the morphology changes of ER post-PEDV infection. Western blot and real-time PCR identified the differences of UPR genes in response to PEDV infection. The results suggested that PEDV infection induced UPR in Vero cells. Meanwhile, we silenced the expression of PKR-like ER kinase (PERK) by shRNA, we found that the knockdown of PERK increased virus loads in the cells, which was consistent with the result on 4-phenylbutyrate (4-PBA) treatment. We next determined whether 2-Deoxy-d-glucose (2-DG), an ER stress inducer, possessed antiviral activity against PEDV infection. Plaque formation assay, RT-PCR and Western blot analysis suggested that 2-DG might inhibit virus infection by affecting viral protein translation during the early stage of virus infection. Interestingly, we also found that 2-DG treatment could affect virus assembly, which is similar to previous studies on influenza virus. All these results support the therapeutic potential of using 2-DG or glucose/mannose analogs to induce the UPR to block virus replication.

Giant-cell glioblastoma of childhood associated with HIV-1 and JC virus coinfection

PURPOSE

John Cunningham (JC) viral DNA sequence has seldom been reported in patients with brain tumors such as high grade gliomas and medulloblastomas, pointing to a role in the etiopathogenesis of such tumors.

RESULTS

We present a unique clinical case of an HIV-positive pediatric patient with multifocal leukoencephalopathy and confirmed JC virus (JCV) infection that developed a giant-cell glioblastoma.

CONCLUSIONS

Experimental data with infected primates has previously hypothesized an association of human giant-cell glioblastoma with JCV or progressive multifocal leukoencephalopathy, though such association has not been documented in the literature for humans. Future studies with larger cohorts and molecular pathological analyses are still needed to corroborate the role of the widely spread human neurotropic virus in early transformation and in the development of brain tumors with different histology in the setting of HIV-related severe immunosuppression.

Infectomics Screening for Novel Antiviral Drug Targets

Preclinical Research

Copyright 2012 Wiley-Liss, Inc., A Wiley Company

Infectomics, a novel way to globally and comprehensively understand the interactions between microbial pathogens and their hosts, has significantly expanded understanding of the microbial infections. The infectomics view of viral–host interactions on the viral perspective principally focuses on gene acquisition, deletion, and point mutation, while traditional antiviral drug discovery concentrates on viral encoding proteins. Recently, high‐throughput technologies, such as mass spectrometry‐based proteomics, activity‐based protein profiling, microarray analysis, yeast two‐hybrid assay, small interfering RNA screening, and micro RNA profiling, have been gradually employed in the research of virus–host interactions. Besides, signaling pathways and cellular processes involved in viral–host interactions provide new insights of infectomics in antiviral drug discovery. In this review, we summarize related infectomics approaches in the studies of virus–host interactions, which shed light on the development of novel antiviral drug targets screening.