Small molecule inhibitors of the host cell COX/AREG/EGFR/ERK pathway attenuate cytomegalovirus-induced pathogenesis

Targeting Host Cellular Factors as a Strategy of Therapeutic Intervention for Herpesvirus Infections

Herpesviruses utilize various host factors to establish latent infection, survival, and spread disease in the host. These factors include host cellular machinery, host proteins, gene expression, multiple transcription factors, cellular signal pathways, immune cell activation, transcription factors, cytokines, angiogenesis, invasion, and factors promoting metastasis. The knowledge and understanding of host genes, protein products, and biochemical pathways lead to discovering safe and effective antivirals to prevent viral reactivation and spread infection. Here, we focus on the contribution of pro-inflammatory, anti-inflammatory, and resolution lipid metabolites of the arachidonic acid (AA) pathway in the lifecycle of herpesvirus infections. We discuss how various herpesviruses utilize these lipid pathways to their advantage and how we target them to combat herpesvirus infection. We also summarize recent development in anti-herpesvirus therapeutics and new strategies proposed or under clinical trials. These anti-herpesvirus therapeutics include inhibitors blocking viral life cycle events, engineered anticancer agents, epigenome influencing factors, immunomodulators, and therapeutic compounds from natural extracts.

Single-Cell RNA Sequencing Identifies Yes-Associated Protein 1-Dependent Hepatic Mesothelial Progenitors in Fibrolamellar Carcinoma

Fibrolamellar carcinoma (FLC) is characterized by in-frame fusion of DnaJ heat shock protein family (Hsp40) member B1 (DNAJB1) with protein kinase cAMP-activated catalytic subunit α (PRKACA) and by dense desmoplasia. Surgery is the only effective treatment because mechanisms supporting tumor survival are unknown. We used single-cell RNA sequencing to characterize a patient-derived FLC xenograft model and identify therapeutic targets. Human FLC cells segregated into four discrete clusters that all expressed the oncogene Yes-associated protein 1 (YAP1). The two communities most enriched with cells coexpressing FLC markers [CD68, A-kinase anchoring protein 12 (AKAP12), cytokeratin 7, epithelial cell adhesion molecule (EPCAM), and carbamoyl palmitate synthase-1] also had the most cells expressing YAP1 and its proproliferative target genes (AREG and CCND1), suggesting these were proliferative FLC cell clusters. The other two clusters were enriched with cells expressing profibrotic YAP1 target genes, ACTA2, ELN, and COL1A1, indicating these were fibrogenic FLC cells. All clusters expressed the YAP1 target gene and mesothelial progenitor marker mesothelin, and many mesothelin-positive cells coexpressed albumin. Trajectory analysis predicted that the four FLC communities were derived from a single cell type transitioning among phenotypic states. After establishing a novel FLC cell line that harbored the DNAJB1-PRKACA fusion, YAP1 was inhibited, which significantly reduced expression of known YAP1 target genes as well as cell growth and migration. Thus, both FLC epithelial and stromal cells appear to arise from DNAJB1-PRKACA fusion in a YAP1-dependent liver mesothelial progenitor, identifying YAP1 as a target for FLC therapy.

BPTF cooperates with p50 NF-κB to promote COX-2 expression and tumor cell growth in lung cancer

Cyclooxygenase-2 (COX-2) is overexpressed in most human cancers, but its precise regulatory mechanism in cancer cells remains unclear. The aims of this study are to discover and identify the new regulatory factors which bind to the COX-2 promoter and regulate COX-2 expression and cancer cell growth, and to elucidate the mechanisms of action of these factors in lung cancer. In this study, the COX-2 promoter-binding protein BPTF (bromodomain PHD finger transcription factor) was detected, identified and verified by biotin-streptavidin-agarose pulldown, mass spectrum analysis and chromatin immunoprecipitation (ChIP) in lung cancer cells, respectively. The expressions of COX-2 and BPTF in lung cancer cell lines, mouse tumor tissues and human clinical samples were detected by RT-PCR, Western blot and immunohistochemistry assays. The interaction of BPTF with NF-kB was analyzed by immunoprecipitation and confocal immunofluorescence assays. We discovered and identified BPTF as a new COX-2 promoter-binding protein in human lung cancer cells. Knockdown of BPTF inhibited COX-2 promoter activity and COX-2 expression in lung cancer cells in vitro and in vivo. We also found that BPTF functioned as a transcriptional regulator through its interaction with the p50 subunit of NF-kB. Knockdown of BPTF abrogated the binding of p50 to the COX-2 promoter, while the inhibition of p50 activity abolished the decreased trend of COX-2 expression and lung cancer cell proliferation caused by BPTF silencing. Moreover, we showed that the expressions of BPTF and COX-2 in tumor tissues of lung cancer patients were positively correlated, and high co-expression of BPTF and COX-2 predicted poor prognosis in lung cancer patients. Collectively, our results indicated that BPTF cooperated with p50 NF-κB to regulate COX-2 expression and lung cancer growth, suggesting that the BPTF/p50/COX-2 axis could be a potential therapeutic target for lung cancer.

Mechanisms of human cytomegalovirus infection with a focus on epidermal growth factor receptor interactions

Human cytomegalovirus (HCMV) is a widespread opportunistic herpesvirus that causes severe diseases in immunocompromised individuals. It has a high prevalence worldwide that is linked with socioeconomic factors. Similar to other herpesviruses, HCMV has the ability to establish lifelong persistence and latent infection following primary exposure. HCMV infects a broad range of cell types. This broad tropism suggests that it may use multiple receptors for host cell entry. The identification of receptors used by HCMV is essential for understanding viral pathogenesis, because these receptors mediate the early events necessary for infection. Many cell surface components have been identified as virus receptors, such as epidermal growth factor receptor (EGFR), which is characterized by tyrosine kinase activity and plays a crucial role in the control of key cellular transduction pathways. EGFR is essential for HCMV binding, signaling, and host cell entry. This review focuses on HCMV infection via EGFR on different cell types and its implications for the cellular environment, viral persistence, and infection.

CMV-induced embryonic mouse organ of corti dysplasia: Network architecture of dysfunctional lateral inhibition

BACKGROUND

Congenital cytomegalovirus infection is the major nongenetic cause of sensorineural hearing loss at birth and beyond. Among other pathologies, there is a striking dysplasia/hyperplasia of organ of Corti hair and supporting cells.

METHODS

Using an in vitro embryonic mouse model of cytomegalovirus-induced cochlear teratogenesis that mimics the known human pathology, and functional signaling network modeling, we tested the hypothesis that cytomegalovirus disrupts the highly ordered organ of Corti hair and supporting cells pattern by dysregulating Notch and Fgfr3, their cognate ligands and downstream effectors.

RESULTS

Several novel emergent properties of the critical lateral inhibition subnetwork became apparent. The subnetwork has classic small-world properties such as short paths between most gene pairs, few long-distance links, and considerable clustering. Concomitantly, the calculated probability that our specific gene expression dataset is from dysplastic organs of Corti is highly significant (p < 1 × 10(-12) ). Furthermore, we determined that the subnetwork has a highly heterogeneous scale-free topology in which the highly linked genes (hubs), Notch and Fgfr3, play a central role in mediating interactions among the less linked genes.

CONCLUSION

This phenomenon has important biologic and therapeutic implications.

GWAS, cytomegalovirus infection, and schizophrenia

In recent years good progress has been made in uncovering the genetic underpinnings of schizophrenia. Even so, as a polygenic disorder, schizophrenia has a complex etiology that is far from understood. Meanwhile data are being collected enabling the study of interactions between genes and the environment. A confluence of data from genetic and environmental exposure studies points to the role of infections and immunity in the pathophysiology of schizophrenia. In a recent study by Børglum et al., a single nucleotide polymorphism (SNP) in the gene CTNNA3 was identified that may provide clues to gene-environment interactions. The carriers of the minor allele for the SNP had a 5 fold risk of later developing schizophrenia if their mothers were CMV positive, while the children not carrying the allele had no excess risk from maternal CMV. In the current paper we summarize recent advances to clarify possible mechanism of such interactions between the host genotype and infection in schizophrenia risk.

Induction of B7-H1 expression by human cytomegalovirus in extravillous cytotrophoblast cells and role of MAPK pathway

Objective: This paper is aimed at to evaluate B7-H1 expression as induced by human cytomegalovirus (HCMV) in extravillous cytotrophoblast cell line HPT-8 and possible underlying mechanism.

Method: Real time PCR and flow cytometry were used to determine B7-H1 mRNA and protein before and after HCMV infection in HPT-8 cells. Western blot analysis was used to determine the level of MAPK phosphorylation in HPT-8 cell lines infected with HCMV.

Results: 100TCID50 was found to be the most effective dose, capable of stimulating B7-H1 mRNA and protein expression in HPT-8 cells. When empty control group was considered to have a B7-H1 mRNA value of 1, B7-H1 mRNA was 4.32 in 100TCID50 group. In flow cytometry study, mean fluorescence intensity (MFI) of 100TCID50 group was 16.14, while empty control group was 1.34. Both mRNA and protein expression were found to be significantly increased (P<0.05) in 100TCID50 group compared to empty control group. The result of Western blot analysis showed increase in B7-H1 expression caused by the extracellular signaling that was related to ERK activation and the ERK inhibitor U0126 was found to reverse this increase.

Conclusion: HCMV upregulates B7-H1 expression in human extravillous cytotrophoblast cell line HPT-8, which is related to MAPK activation. Our result would be helpful in finding better therapies against intrauterine HCMV infection.

CMV-induced pathology: pathway and gene-gene interaction analysis

Mucoepidermoid carcinoma (MEC) is the most prevalent malignant tumor in major and minor salivary glands (SGs). We have recently identified human cytomegalovirus (hCMV) as a principle component in the multifactorial causation of SG-MEC. This finding is corroborated by the ability of the purified mouse CMV (mCMV) to induce malignant transformation of SG cells in a three-dimensional in vitro mouse model, using a similar oncogenic signaling pathway. Our prior studies indicate that the core tumor microenvironment (TME) is a key regulator of pathologic progression, particularly the cancer-associated fibroblast (CAF) component. Studies of early CAFs immunodetect aberrant expression of ECM components, as well as multiple growth factors, cytokines and transcription factors. Here we present the mechanistic insight derived from a mathematical structure ("wiring diagram") used to model complex relationships between a highly relevant (p=9.43×10(-12)) global "cancer network" of 32 genes and their known links. Detailed characterization of the functional architecture of the examined "cancer network" exposes the critical crosstalk and compensatory pathways that limit the efficacy of targeted anti-kinase therapies.

Treatment of cytomegalovirus infections beyond acute disease to improve human health

Human cytomegalovirus is a common virus that establishes latency and persistence after a primary infection in 50-90% of populations worldwide. In otherwise healthy persons, the infection is generally mild or asymptomatic, although it may cause mononucleosis, prolonged episodes of fever, and hepatitis. However, in AIDS patients and transplant recipients who are immunosuppressed, severe, life-threatening infections may develop. CMV is also the most common congenital infection and may cause birth defects and deafness. Emerging evidence shows a high prevalence of this virus in patients with chronic inflammatory diseases or tumours of different origin, such as breast, colon, and prostate cancer, neuroblastoma, medulloblastoma, and glioblastoma. Several drugs are available to treat CMV infections. This review will highlight the possibility of using anti-CMV therapy to improve outcome not only in patients with acute CMV infections but also in patients with inflammatory diseases and cancer.

Effects of valganciclovir as an add-on therapy in patients with cytomegalovirus-positive glioblastoma: a randomized, double-blind, hypothesis-generating study

Cytomegalovirus is highly prevalent in glioblastomas. In 2006, we initiated a randomized, double-blind, placebo-controlled, hypothesis-generating study to examine the safety and potential efficacy of Valganciclovir as an add-on therapy for glioblastoma. Forty-two glioblastoma patients were randomized in double-blind fashion to receive Valganciclovir or placebo in addition to standard therapy for 6 months. Magnetic resonance images were obtained before and immediately and 3 and 6 months after surgery to evaluate treatment efficacy by measuring contrast enhancing tumor volume (primary end point). Survival data were analyzed for patients and controls in explorative analyses to aid the design of future randomized trials. Trends but no significant differences were observed in tumor volumes in Valganciclovir and placebo patients at 3 (3.58 vs. 7.44 cm3, respectively, p = 0.2881) and 6 (3.31 vs. 13.75 cm3, p = 0.2120) months. Median overall survival (OS) was similar in both groups (17.9 vs. 17.4 months, p = 0.430). Patients could take Valganciclovir for compassionate use after the study phase. Explorative analyses showed an OS of 24.1 months (95% CI, 17.4-40.3) in patients receiving >6 months of Valganciclovir (Val > 6M) versus 13.1 months (95% CI, 7.9-17.7, p < 0.0001) in patients receiving Valganciclovir for 0 or <6 months, and 13.7 months (95% CI, 6.9-17.3, p = 0.0031) in contemporary controls. OS at 4 years was 27.3% in Val>6M patients versus 5.9% in controls (p = 0.0466). Prolonged OS in Val>6M patients suggest that future randomized trials are warranted and should evaluate whether continuous antiviral treatment can improve outcome in glioblastoma patients.

Cytomegalovirus-induced salivary gland pathology: resistance to kinase inhibitors of the upregulated host cell EGFR/ERK pathway is associated with CMV-dependent stromal overexpression of IL-6 and fibronectin

Background

Recently we identified a relationship between human cytomegalovirus (hCMV) and human salivary gland (SG) mucoepidermoid carcinoma (MEC) in over 90% of cases; tumorigenesis in these cases uniformly correlated with active hCMV protein expression and an upregulation of the EGFR → ERK pathway. Our previously characterized, novel mouse organ culture model of mouse CMV (mCMV)-induced tumorigenesis displays a number of histologic and molecular characteristics similar to human MEC.

Methods

Newborn mouse submandibular glands (SMGs) were incubated with 1 × 10⁵ PFU/ml of lacZ-tagged mCMV RM427+ on day 0 for 24 hours and then cultured in virus-free media for a total of 6 or 12 days with or without EGFR/ERK inhibitors and/or aciclovir. SMGs were collected for histology, immunolocalization (pERK, FN, IL-6), viral distribution, or Western blot analysis (pERK).

Results

Here we report: (1) mouse SMG tumors soon exhibit an acquired resistance to EGFR/ERK pathway kinase inhibitors, alone or in combination; (2) long term tumor regression can only be sustained by concurrent inhibitor and antiviral treatment; (3) CMV-dependent, kinase inhibitor resistance is associated with overexpression of fibronectin and IL-6 proteins in abnormal stromal cells.

Conclusions

Acquired resistance to kinase inhibitors is dependent upon CMV dysregulation of alternative pathways with downstream effectors common with the targeted pathway, a phenomenon with important therapeutic implications for human MEC of salivary glands.

An in vitro mouse model of congenital cytomegalovirus-induced pathogenesis of the inner ear cochlea

Congenital human cytomegalovirus (CMV) infection is the leading nongenetic etiology of sensorineural hearing loss (SNHL) at birth and prelingual SNHL not expressed at birth. The paucity of temporal bone autopsy specimens from infants with congenital CMV infection has hindered the critical correlation of histopathology with pathogenesis. Here, we present an in vitro embryonic mouse model of CMV-infected cochleas that mimics the human sites of viral infection and associated pathology. There is a striking dysplasia/hyperplasia in mouse CMV-infected cochlear epithelium and mesenchyme, including organ of Corti hair and supporting cells and stria vascularis. This is concomitant with significant dysregulation of p19, p21, p27, and Pcna gene expression, as well as proliferating cell nuclear antigen (PCNA) protein expression. Other pathologies similar to those arising from known deafness gene mutations include downregulation of KCNQ1 protein expression in the stria vascularis, as well as hypoplastic and dysmorphic melanocytes. Thus, this model provides a relevant and reliable platform within which the detailed cell and molecular biology of CMV-induced deafness may be studied.

Cytomegalovirus infection in brain tumors: A potential new target for therapy?

Emerging evidence demonstrate a high prevalence of cytomegalovirus (CMV) proteins and nucleic acids in different tumors. CMV is confined to tumor cells and non-cancer cells in close proximity to tumors are consistently virus negative. CMV confers both oncogenic and oncomodulatory mechanisms, and may therefore provide a novel target in cancer treatment.

Is human cytomegalovirus a target in cancer therapy?

Human cytomegalovirus (HCMV) is a herpesvirus that is prevalent in the human population. HCMV has recently been implicated in different cancer forms where it may provide mechanisms for oncogenic transformation, oncomodulation and tumour cell immune evasion. Moreover, antiviral treatment against HCMV has been shown to inhibit tumour growth in preclinical models. Here we describe the possible involvement of HCMV in cancer and discuss the potential molecular impact expression of HCMV proteins have on tumour cells and the surrounding tumour microenvironment.

The C11R gene, which encodes the vaccinia virus growth factor, is partially responsible for MVA-induced NF-κB and ERK2 activation

MVA is an attenuated strain of vaccinia virus (VACV) that is a popular vaccine vector. MVA infection activates NF-κB. For 293T cells, it is known that MVA early gene expression activates extracellular signal-regulated kinase 2 (ERK2), resulting in NF-κB activation. However, other viral and cellular mechanisms responsible for this event are ill defined. The data presented here show that the epidermal growth factor receptor (EGFR) is at least one apical trigger in this pathway: ERK2 and NF-κB activation was diminished when MVA infections occurred in cells devoid of the EGFR (CHO K1 cells) or in the presence of a drug that inhibits EGFR activation (AG1478) in 293T cells. The expression of dominant negative Ras or Raf proteins still permitted NF-κB activation, suggesting that a nonclassical EGFR-based signal transduction pathway triggered ERK2-NF-κB activation. C11R is an early gene present in MVA and other orthopoxviruses. It encodes the soluble, secreted vaccinia virus growth factor (VGF), a protein that binds to and stimulates the EGFR. Here it was observed that NF-κB was activated in 293T cells transfected with a plasmid encoding the C11R gene. Silencing by small interfering RNA (siRNA) or deletion of the C11R gene (MVAΔC11R) reduced both MVA-induced ERK2 and NF-κB activation in 293T cells or the keratinocyte line Hacat, suggesting that this mechanism of MVA-induced NF-κB activation may be common for several cell types.

Murine cytomegalovirus infection of cultured mouse cells induces expression of miR-7a

One goal of virus infection is to reprogramme the host cell to optimize virus replication. As part of this process, viral microRNAs (miRNAs) may compete for components of the miRNA/small interfering RNA pathway, as well as regulate cellular targets. Murine cytomegalovirus (MCMV) has been described to generate large numbers of viral miRNAs during lytic infection and was therefore used to analyse the impact of viral miRNAs on the host-cell small-RNA system, as well as to check for sorting of viral small RNAs into specific Argonaute (Ago) proteins. Deep-sequencing analysis of MCMV-infected cells revealed that viral miRNAs represented only ~13% of all detected miRNAs. All previously described MCMV miRNAs with the exception of miR-m88-1* were confirmed, and for the MCMV miR-m01-1 hairpin, an additional miRNA, designated miR-m01-1-3p, was found. Its presence was confirmed by quantitative real-time PCR and Northern blotting. Deep sequencing after RNA-induced silencing complex (RISC) immunoprecipitation with antibodies specific for either Ago1 or Ago2 showed that all MCMV miRNAs were loaded into both RISCs. The ratio of MCMV to mouse miRNAs was not increased after immunoprecipitation of Ago proteins. Viral miRNAs therefore did not overwhelm the host miRNA processing system, nor were they incorporated preferentially into RISCs. Three mouse miRNAs were found that showed altered expression as a result of MCMV infection. Downregulation of miR-27a, as described previously, could be confirmed. In addition, miR-26a was downregulated, and upregulation of miR-7a dependent on viral protein expression could be observed.

Human cytomegalovirus and mucoepidermoid carcinoma of salivary glands: cell-specific localization of active viral and oncogenic signaling proteins is confirmatory of a causal relationship

Human cytomegalovirus (hCMV) infection is common. Although still controversial, there is growing evidence that active hCMV infection is associated with a variety of malignancies, including brain, breast, lung, colon, and prostate. Given that hCMV is frequently resident in salivary gland (SG) ductal epithelium, we hypothesized that hCMV would be important to the pathogenesis of SG mucoepidermoid carcinoma (MEC). This was initially supported by our finding that purified CMV induces malignant transformation in SG cells in an in vitro mouse model, and utilizes a pathogenic pathway previously reported for human MEC. Here we present the histologic and molecular characterizations of 39 human SG MECs selected randomly from a repository of cases spanning 2004-2011. Serial sections were obtained from formalin-fixed, paraffin embedded, tissue blocks from previous incisional or excisional biopsies. Immunohistochemical assays were performed for active hCMV proteins (IE1 and pp65) and the activated COX/AREG/EGFR/ERK signaling pathway. All four prospective causal criteria for viruses and cancer are fully satisfied: (1) protein markers for active hCMV are present in 97% of MECs; (2) markers of active hCMV are absent in non-neoplastic SG tissues; (3) hCMV-specific proteins (IE1, pp65) are in specific cell types and expression is positively correlated with severity; (4) hCMV correlates and colocalizes with an upregulation and activation of an established oncogenic signaling pathway (COX/AREG/EGFR/ERK). Thus, the evidential support reported here and previously in a mouse model is strongly confirmatory of a causal relationship between hCMV and SG mucoepidermoid carcinoma. To our knowledge, this is the first demonstration of hCMV's role in human oncogenesis that fully responds to all of Koch's Postulates as revised for viruses and cancer. In the absence of any contrary evidence, hCMV can reasonably be designated an "oncovirus."