Human cytomegalovirus gene expression in long-term infected glioma stem cells

Role of cytomegalovirus in glioblastoma development: promoter or culprit?

Glioblastoma is the most common primary malignant tumor of the central nervous system, with a median survival of less than two years. While the etiology of glioblastoma is unclear, viral infection has emerged as a potential contributing factor. Cytomegalovirus (CMV) was first reported to be associated with glioblastoma in 2002. Since then, many studies have detected CMV in glioblastoma tissues suggesting it may plays a role in the glioblastoma progression. While there is no direct evidence confirmings CMV as an oncogenic virus, studies have demonstrated that CMV promotes glioblastoma development in cell and animal models, with several CMV-related genes implicated in tumorigenesis. Importantly, adjuvant CMV antiviral therapy has been proven to improve glioblastoma patient survival. This review focuses on clinical studies regarding the relationship between CMV and glioblastoma, the mechanism of CMV in tumorigenesis, advances in animal models of CMV-induced glioblastoma, and key directions for future investigations.

Inflammatory Breast Cancer: The Secretome of HCMV+ Tumor-Associated Macrophages Enhances Proliferation, Invasion, Colony Formation, and Expression of Cancer Stem Cell Markers

Inflammatory breast cancer (IBC) is a highly aggressive phenotype of breast cancer that is characterized by a high incidence early metastasis. We previously reported a significant association of human cytomegalovirus (HCMV) DNA in the carcinoma tissues of IBC patients but not in the adjacent normal tissues. HCMV-infected macrophages serve as “mobile vectors” for spreading and disseminating virus to different organs, and IBC cancer tissues are highly infiltrated by tumor-associated macrophages (TAMs) that enhance IBC progression and promote breast cancer stem cell (BCSC)-like properties. Therefore, there is a need to understand the role of HCMV-infected TAMs in IBC progression. The present study aimed to test the effect of the secretome (cytokines and secreted factors) of TAMs derived from HCMV⁺ monocytes isolated from IBC specimens on the proliferation, invasion, and BCSC abundance when tested on the IBC cell line SUM149. HCMV⁺ monocytes were isolated from IBC patients during modified radical mastectomy surgery and tested in vitro for polarization into TAMs using the secretome of SUM149 cells. MTT, clonogenic, invasion, real-time PCR arrays, PathScan Intracellular Signaling array, and cytokine arrays were used to characterize the secretome of HCMV⁺ TAMs for their effect on the progression of SUM149 cells. The results showed that the secretome of HCMV⁺ TAMs expressed high levels of IL-6, IL-8, and MCP-1 cytokines compared to HCMV^- TAMs. In addition, the secretome of HCMV⁺ TAMs induced the proliferation, invasion, colony formation, and expression of BCSC-related genes in SUM149 cells compared to mock untreated cells. In addition, the secretome of HCMV⁺ TAMs activated the phosphorylation of intracellular signaling molecules p-STAT3, p-AMPKα, p-PRAS40, and p-SAPK/JNK in SUM149 cells. In conclusion, this study shows that the secretome of HCMV⁺ TAMs enhances the proliferation, invasion, colony formation, and BCSC properties by activating the phosphorylation of p-STAT3, p-AMPKα, p-PRAS40, and p-SAPK/JNK intracellular signaling molecules in IBC cells.

The Basis and Advances in Clinical Application of Cytomegalovirus-Specific Cytotoxic T Cell Immunotherapy for Glioblastoma Multiforme

A high percentage of malignant gliomas are infected by human cytomegalovirus (HCMV), and the endogenous expression of HCMV genes and their products are found in these tumors. HCMV antigen expression and its implications in gliomagenesis have emerged as a promising target for adoptive cellular immunotherapy (ACT) strategies in glioblastoma multiforme (GB) patients. Since antigen-specific T cells in the tumor microenvironments lack efficient anti-tumor immune response due to the immunosuppressive nature of glioblastoma, CMV-specific ACT relies on in vitro expansion of CMV-specific CD8+ T cells employing immunodominant HCMV antigens. Given the fact that several hurdles remain to be conquered, recent clinical trials have outlined the feasibility of CMV-specific ACT prior to tumor recurrence with minimal adverse effects and a substantial improvement in median overall survival and progression-free survival. This review discusses the role of HCMV in gliomagenesis, disease prognosis, and recent breakthroughs in harnessing HCMV-induced immunogenicity in the GB tumor microenvironment to develop effective CMV-specific ACT.

Suppression of human trophoblast syncytialization by human cytomegalovirus infection

INTRODUCTION

Placental dysfunction triggers fetal growth restriction in congenital human cytomegalovirus (HCMV) infection. Studies suggest that HCMV infection interferes with the differentiation of human trophoblasts. However, the underlying mechanisms have not been clarified. This study investigated the impact of HCMV infection on gene transcriptomes in cytotrophoblasts (CTBs) associated with placental dysfunction.

METHODS

CTBs were isolated from human term placentas, and spontaneous syncytialization was observed in vitro. The transcriptome profiles were compared between CTB groups with and without HCMV infection by cap analysis gene expression sequencing. The effect of HCMV infection on trophoblast differentiation was evaluated by examining cell fusion status using immunocytochemical staining for desmoplakin and assessing the production of cell differentiation markers, including hCG, PlGF, and soluble Flt-1, using ELISA.

RESULTS

The expression of the genes categorized in the signaling pathways related to the cell cycle was significantly enhanced in CTBs with HCMV infection compared with uninfected CTBs. HCMV infection hindered the alteration of the gene expression profile associated with syncytialization. This suppressive effect under HCMV infection was concurrent with the reduction in hCG and PlGF secretion. Immunostaining for desmoplakin revealed that HCMV infection reduced the cell fusion of cultured CTBs. These findings imply that HCMV infection has a negative impact on syncytialization, which is indispensable for the maintenance of villous function.

DISCUSSION

HCMV infection interferes with gene expression profiles and functional differentiation of trophoblasts. Suppression of syncytialization may be a survival strategy for HCMV to expand infection and could be associated with placental dysfunction.

Viral G Protein-Coupled Receptors: Attractive Targets for Herpesvirus-Associated Diseases

Herpesviruses are ubiquitous pathogens that establish lifelong, latent infections in their host. Spontaneous reactivation of herpesviruses is often asymptomatic or clinically manageable in healthy individuals, but reactivation events in immunocompromised or immunosuppressed individuals can lead to severe morbidity and mortality. Moreover, herpesvirus infections have been associated with multiple proliferative cardiovascular and post-transplant diseases. Herpesviruses encode viral G protein-coupled receptors (vGPCRs) that alter the host cell by hijacking cellular pathways and play important roles in the viral life cycle and these different disease settings. In this review, we discuss the pharmacological and signaling properties of these vGPCRs, their role in the viral life cycle, and their contribution in different diseases. Because of their prominent role, vGPCRs have emerged as promising drug targets, and the potential of vGPCR-targeting therapeutics is being explored. Overall, these vGPCRs can be considered as attractive targets moving forward in the development of antiviral, cancer, and/or cardiovascular disease treatments. SIGNIFICANCE STATEMENT: In the last decade, herpesvirus-encoded G protein-coupled receptors (GPCRs) have emerged as interesting drug targets with the growing understanding of their critical role in the viral life cycle and in different disease settings. This review presents the pharmacological properties of these viral receptors, their role in the viral life cycle and different diseases, and the emergence of therapeutics targeting viral GPCRs.

Persistent HCMV infection of a glioblastoma cell line contributes to the development of resistance to temozolomide

Glioblastoma multiforme (GBM) is the most aggressive form of primary human gliomas. While chemotherapy using the DNA alkylating agent temozolomide (TMZ) is a first line treatment for GBMs, the development of resistance to TMZ is a common limitation to successful treatment. Human Cytomegalovirus (HCMV) is a ubiquitous β-herpesvirus that establishes a lifelong infection latent infection in host haematopoetic cells, where lytic replication of the virus is silenced. HCMV can also establish a persistent infection in hosts, where low levels of virus are lytically produced. Furthermore, multiple studies have identified HCMV DNA and/or proteins in human GBM samples, and have shown that acute infection with HCMV confers a glioblastoma stem cell (GSC) phenotype, further supporting an oncomodulatory role for HCMV in GBM progression and severity. In this current study, we examined the long-term effects of HCMV persistence to cell viability, cell proliferation, and the development of TMZ resistance over time using a glioblastoma cell line known as LN-229. Persistent HCMV infections were established and maintained in this cell line for 30 weeks without the addition of new virus. Here, we report that HCMV persistence in this cell line resulted in increased cell viability, increased cell proliferation, and a marked resistance to the DNA alkylating agent, TMZ, over time, suggesting that low levels of lytically replicating HCMV could contribute to tumor progression in GBM.

Accelerated cancer aggressiveness by viral oncomodulation: New targets and newer natural treatments for cancer control and treatment

An infectious etiology for a number of cancers has been entertained for over 100 years and modern studies have confirmed that a number of viruses are linked to cancer induction. While a large number of viruses have been demonstrated in a number of types of cancers, most such findings have been dismissed in the past as opportunistic infections, especially with persistent viruses with high rates of infectivity of the world’s populations. More recent studies have clearly shown that while not definitely causing these cancers, these viruses appear capable of affecting the biology of these tumors in such a way as to make them more aggressive and more resistant to conventional treatments. The term oncomodulatory viruses has been used to describe this phenomenon. A number of recent studies have shown a growing number of ways these oncomodulatory viruses can alter the pathology of these tumors by affecting cell-signaling, cell metabolism, apoptosis mechanisms, cell-cell communication, inflammation, antitumor immunity suppression, and angiogenesis. We are also learning that much of the behavior of tumors depends on cancer stem cells and stromal cells within the tumor microenvironment, which participate in extensive, dynamic crosstalk known to affect tumor behavior. Cancer stem cells have been found to be particularly susceptible to infection by human cytomegalovirus. In a number of studies, it has been shown that while only a select number of cells are actually infected with the virus, numerous viral proteins are released into cancer and stromal cells in the microenvironment and these viral proteins are known to affect tumor behavior and aggressiveness.

Cytomegalovirus is a tumor-associated virus: armed and dangerous

Human cytomegalovirus (HCMV) gene products are present in multiple human malignancies, often in specific association with tumor cells and tumor vasculature. Emerging evidence from human and mouse models of CMV infection in cancer indicate that CMV can transform epithelial cells, promote epithelial to mesenchymal transition (EMT) and mesenchymal to epithelial (MET) in tumor cells, promote tumor angiogenesis and proliferation and incapacitate the host anti-CMV immune response. This review will discuss the increasing role of HCMV in human cancer by demonstrating how HCMV is well suited for impacting major themes in oncogenesis including initiation, promotion, progression, metastasis and immune evasion. What emerges is a picture of an extremely versatile pathogen that may play a significant role in human cancer progression and death.

Development of a Human Cytomegalovirus (HCMV)-Based Therapeutic Cancer Vaccine Uncovers a Previously Unsuspected Viral Block of MHC Class I Antigen Presentation

Human cytomegalovirus (HCMV) induces a uniquely high frequency of virus-specific effector/memory CD8+ T-cells, a phenomenon termed “memory inflation”. Thus, HCMV-based vaccines are particularly interesting in order to stimulate a sustained and strong cellular immune response against cancer. Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor with high lethality and inevitable relapse. The current standard treatment does not significantly improve the desperate situation underlining the urgent need to develop novel approaches. Although HCMV is highly fastidious with regard to species and cell type, GBM cell lines are susceptible to HCMV. In order to generate HCMV-based therapeutic vaccine candidates, we deleted all HCMV-encoded proteins (immunoevasins) that interfere with MHC class I presentation. The aim being to use the viral vector as an adjuvant for presentation of endogenous tumor antigens, the presentation of high levels of vector-encoded neoantigens and finally the repurposing of bystander HCMV-specific CD8+ T cells to fight the tumor. As neoantigen, we exemplarily used the E6 and E7 proteins of human papillomavirus type 16 (HPV-16) as a non-transforming fusion protein (E6/E7) that covers all relevant antigenic peptides. Surprisingly, GBM cells infected with E6/E7-expressing HCMV-vectors failed to stimulate E6-specific T cells despite high level expression of E6/E7 protein. Further experiments revealed that MHC class I presentation of E6/E7 is impaired by the HCMV-vector although it lacks all known immunoevasins. We also generated HCMV-based vectors that express E6-derived peptide fused to HCMV proteins. GBM cells infected with these vectors efficiently stimulated E6-specific T cells. Thus, fusion of antigenic sequences to HCMV proteins is required for efficient presentation via MHC class I molecules during infection. Taken together, these results provide the preclinical basis for development of HCMV-based vaccines and also reveal a novel HCMV-encoded block of MHC class I presentation.

The role of CMV in glioblastoma and implications for immunotherapeutic strategies

Controversy surrounds the role of cytomegalovirus (CMV) in glioblastoma (GBM). However, several studies have shown that CMV nucleic acids and proteins are present within GBM tumor tissue. CMV has been implicated in GBM pathogenesis by affecting tumor stem cell factors, angiogenesis and immune pathways. Anti-viral therapy has not been found to definitively improve outcomes for patients with GBM. Several studies have leveraged CMV by targeting CMV antigens using ex-vivo expanded T cells or dendritic cell vaccines. The initial results from these studies are promising and larger studies are underway.

Impact of human cytomegalovirus on glioblastoma cell viability and chemotherapy treatment

The relationship between human cytomegalovirus (HCMV) and tumours has been extensively investigated, mainly in glioblastoma multiforme (GBM), a malignant tumour of the central nervous system with low overall survival rates. Several reports have demonstrated the presence of HCMV in GBM, although typically restricted to a low number of cells, and studies have indicated that viral proteins have the ability to dysregulate cellular processes and increase tumour malignancy. Treatment of GBM involves the use of the chemotherapeutic agents temozolomide (TMZ) and carmustine (bis-chloroethylnitrosourea, BCNU), which lead to the attachment of adducts to the DNA backbone, causing errors during replication and consequent cell death. It is known that HCMV infection can modulate DNA repair pathways, but what effects the virus may exhibit during chemotherapy are unknown. Here we approach this question by analysing HCMV infection and viral protein accumulation in GBM cell lines with different genotypes and their response to TMZ and BCNU in the presence of the virus. We demonstrate that A172, TP365MG and U251MG GBM cells are efficiently infected by both low-passage (TB40E) and high-passage (AD169) HCMV strains. However, the GBM cell lines vary widely in their permissiveness to viral gene expression and exhibit very different patterns of immediate early, early and late protein accumulation. HCMV reduces the viability of permissive GBM cells in a multiplicity-dependent manner in both the absence and presence of TMZ or BNCU. In sum, we demonstrate that GBM cell lines are equally susceptible but differentially permissive to infection by both low- and high-passage strains of HCMV. This observation not only indicates that viral replication is largely controlled by cellular factors in this system, but also provides a possible explanation for why viral gene products are only found in a subset of cells in GBM tumours. Furthermore, we conclude that the virus does not confer increased resistance to chemotherapeutic drugs in various GBM cell lines, but instead reduces tumour cell viability. These results highlight that the oncomodulatory potential of HCMV is not limited to cancer-promoting activities, but also includes adverse effects on tumour cell proliferation or survival.

The Immunomodulatory Capacity of an Epstein-Barr Virus Abortive Lytic Cycle: Potential Contribution to Viral Tumorigenesis

Epstein-Barr virus (EBV) is characterized by a bipartite life cycle in which latent and lytic stages are alternated. Latency is compatible with long-lasting persistency within the infected host, while lytic expression, preferentially found in oropharyngeal epithelial tissue, is thought to favor host-to-host viral dissemination. The clinical importance of EBV relates to its association with cancer, which we think is mainly a consequence of the latency/persistency mechanisms. However, studies in murine models of tumorigenesis/lymphomagenesis indicate that the lytic cycle also contributes to cancer formation. Indeed, EBV lytic expression is often observed in established cell lines and tumor biopsies. Within the lytic cycle EBV expresses a handful of immunomodulatory (BCRF1, BARF1, BNLF2A, BGLF5 & BILF1) and anti-apoptotic (BHRF1 & BALF1) proteins. In this review, we discuss the evidence supporting an abortive lytic cycle in which these lytic genes are expressed, and how the immunomodulatory mechanisms of EBV and related herpesviruses Kaposi Sarcoma herpesvirus (KSHV) and human cytomegalovirus (HCMV) result in paracrine signals that feed tumor cells. An abortive lytic cycle would reconcile the need of lytic expression for viral tumorigenesis without relaying in a complete cycle that would induce cell lysis to release the newly formed infective viral particles.

CMV70-3P miRNA contributes to the CMV mediated glioma stemness and represents a target for glioma experimental therapy

Glioblastoma multiforme (GBM) is a rapidly progressive brain tumor with a median survival of 15–19 months. Therapeutic resistance and recurrence of the disease is attributed to cancer stem cells (CSC). Here, we report that CMV70-3P miRNA encoded by CMV increases GBM CSC stemness. Inhibition of CMV70-3P expression using oligo inhibitors significantly attenuated the ability of primary glioma cells to proliferate and form neurospheres. At the molecular level, we show that CM70-3P increases expression of cellular SOX2. Collectively, these findings indicate that CMV70-3P is a potential regulator of CMV- mediated glioma progression and cancer stemness.

New extracellular factors in glioblastoma multiforme development: neurotensin, growth differentiation factor-15, sphingosine-1-phosphate and cytomegalovirus infection

Recent years have seen considerable progress in understanding the biochemistry of cancer. For example, more significance is now assigned to the tumor microenvironment, especially with regard to intercellular signaling in the tumor niche which depends on many factors secreted by tumor cells. In addition, great progress has been made in understanding the influence of factors such as neurotensin, growth differentiation factor-15 (GDF-15), sphingosine-1-phosphate (S1P), and infection with cytomegalovirus (CMV) on the 'hallmarks of cancer' in glioblastoma multiforme. Therefore, in the present work we describe the influence of these factors on the proliferation and apoptosis of neoplastic cells, cancer stem cells, angiogenesis, migration and invasion, and cancer immune evasion in a glioblastoma multiforme tumor. In particular, we discuss the effect of neurotensin, GDF-15, S1P (including the drug FTY720), and infection with CMV on tumor-associated macrophages (TAM), microglial cells, neutrophil and regulatory T cells (T_reg), on the tumor microenvironment. In order to better understand the role of the aforementioned factors in tumoral processes, we outline the latest models of intratumoral heterogeneity in glioblastoma multiforme. Based on the most recent reports, we discuss the problems of multi-drug therapy in treating glioblastoma multiforme.

The Updated World Health Organization Glioma Classification: Cellular and Molecular Origins of Adult Infiltrating Gliomas

CONTEXT

- In the recently updated World Health Organization (WHO) classification of central nervous system tumors, our concept of infiltrating gliomas as a molecular dichotomy between oligodendroglial and astrocytic tumors has been codified. Advances in animal models of glioma and a wealth of sophisticated molecular analyses of human glioma tissue have led to a greater understanding of some of the biologic underpinnings of gliomagenesis.

OBJECTIVE

- To review our understanding of gliomagenesis in the setting of the recently updated WHO classification of central nervous system tumors. Topics addressed include a summary of an updated diagnostic schema for infiltrating gliomas, the crucial importance of isocitrate dehydrogenase mutations, candidate cells of origin for gliomas, environmental and other posited contributing factors to gliomagenesis, and the possible role of chromatin topology in setting the stage for gliomagenesis.

DATA SOURCES

- We conducted a primary literature search using PubMed.

CONCLUSIONS

- With multidimensional molecular data sets spanning increasingly larger numbers of patients with infiltrating gliomas, our understanding of the disease at the point of surgical resection has improved dramatically and this understanding is reflected in the updated WHO classification. Animal models have demonstrated a diversity of candidates for glioma cells of origin, but crucial questions remain, including the role of neural stem cells, more differentiated progenitor cells, and glioma stem cells. At this stage the increase in data generated from human samples will hopefully inform the creation of newer animal models that will recapitulate more accurately the diversity of gliomas and provide novel insights into the biologic mechanisms underlying tumor initiation and progression.

Human cytomegalovirus infection enhances cell proliferation, migration and upregulation of EMT markers in colorectal cancer-derived stem cell-like cells

Increasing evidence suggests a link between persistent human cytomegalovirus (HCMV) infection and cancer. Although the role of HCMV in cancer is still elusive, recent studies revealed the presence of HCMV nucleic acids and proteins in different cancer types such as glioblastoma, colorectal, breast, and prostate cancers, and neuroblastoma. Although HCMV may not be directly associated with the neoplastic transformation, the presence of HCMV DNA in the tumorous tissue has been associated with altered clinical outcomes in cancer patients. However, the mechanisms involved in the association between colorectal cancer (CRC) and HCMV are unclear. In this study, we investigated the influence of HCMV infection on CRC or their derived cells. Proliferation and migration assays revealed a high infection efficiency in CRC-derived HT29 and SW480 'stem-like' cells. After 24, 48 and 72 h of HCMV infection, both HT29 and SW480 parental and stem-like cells showed a significant increase in cell proliferation and viability (p<0.0001). Moreover, HCMV infection promoted cell migration. These results demonstrate a significant phenotypic alteration in the CRC cell line upon HCMV infection. Using epithelial to mesenchymal transition (EMT) assays, we demonstrated that the EMT markers and driver genes were upregulated during the virus infection. The WNT signaling pathway, which is associated with the proliferation and migration of CRC cells, was upregulated (6-fold) in HCMV-infected cells as compared to the non-infected cells at day 7 from infection.

Cytomegalovirus-targeted immunotherapy and glioblastoma: hype or hope?

Malignant gliomas, including glioblastoma (GBM), are the most common primary brain tumors. Despite extensive research only modest gains have been made in long-term survival. Standard of care involves maximizing safe surgical resection followed by concurrent chemoradiation with temozolomide. Immunotherapy for GBM is an area of intense research in recent years. New immunotherapies, although promising, have not been integrated into standard practice. Human cytomegalovirus (HCMV) is a DNA virus of the family Herpesviridae. Human seroprevalence is approximately 80%, and in most cases, is associated with asymptomatic infection. HCMV may be an important agent in the initiation, promotion and/or progression of tumorigenesis. Regardless of a possible etiologic role in GBM, interest has centered on exploiting this association for development of immunomodulatory therapies.