C-myc activation impairs the NF-kappaB and the interferon response: implications for the pathogenesis of Burkitt's lymphoma

Resolving candidate genes of duck ovarian tissue transplantation via RNA-Seq and expression network analyses

This study aims to identify candidate genes related to ovarian development after ovarian tissue transplantation through transcriptome sequencing (RNA-seq) and expression network analyses, as well as to provide a reference for determining the molecular mechanism of improving ovarian development following ovarian tissue transplantation. We collected ovarian tissues from 15 thirty-day-old ducks and split each ovary into 4 equal portions of comparable sizes before orthotopically transplanting them into 2-day-old ducks. Samples were collected on days 0 (untransplanted), 3, 6, and 9. The samples were paraffin sectioned and then subjected to Hematoxylin-Eosin (HE) staining and follicular counting. We extracted RNA from ovarian samples via the Trizol method to construct a transcriptome library, which was then sequenced by the Illumina Novaseq 6000 sequencing platform. The sequencing results were examined for differentially expressed genes (DEG) through gene ontology (GO) function and the Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses, gene set enrichment analysis (GSEA), weighted correlation network analysis (WGCNA), and protein-protein interaction (PPI) networks. Some of the candidate genes were selected for verification using real-time fluorescence quantitative PCR (qRT-PCR). Histological analysis revealed a significant reduction in the number of morphologically normal follicles at 3, 6, and 9 d after ovarian transplantation, along with significantly higher abnormality rates (P < 0.05). The transcriptome analysis results revealed 2,114, 2,224, and 2,257 upregulated DEGs and 2,647, 2,883, and 2,665 downregulated DEGs at 3, 6, and 9 d after ovarian transplantation, respectively. Enrichment analysis revealed the involvement multiple pathways in inflammatory signaling, signal transduction, and cellular processes. Furthermore, WGCNA yielded 13 modules, with 10, 4, and 6 candidate genes mined at 3, 6 and 9 d after ovarian transplantation, respectively. Transcription factor (TF) prediction showed that STAT1 was the most important TF. Finally, the qRT-PCR verification results revealed that 12 candidate genes exhibited an expression trend consistent with sequencing data. In summary, significant differences were observed in the number of follicles in duck ovaries following ovarian transplantation. Candidate genes involved in ovarian vascular remodeling and proliferation were screened using RNA-Seq and WGCNA.

Latent Epstein-Barr virus infection collaborates with Myc over-expression in normal human B cells to induce Burkitt-like Lymphomas in mice

Epstein-Barr virus (EBV) is an important cause of human lymphomas, including Burkitt lymphoma (BL). EBV+ BLs are driven by Myc translocation and have stringent forms of viral latency that do not express either of the two major EBV oncoproteins, EBNA2 (which mimics Notch signaling) and LMP1 (which activates NF-κB signaling). Suppression of Myc-induced apoptosis, often through mutation of the TP53 (p53) gene or inhibition of pro-apoptotic BCL2L11 (BIM) gene expression, is required for development of Myc-driven BLs. EBV+ BLs contain fewer cellular mutations in apoptotic pathways compared to EBV-negative BLs, suggesting that latent EBV infection inhibits Myc-induced apoptosis. Here we use an EBNA2-deleted EBV virus (ΔEBNA2 EBV) to create the first in vivo model for EBV+ BL-like lymphomas derived from primary human B cells. We show that cord blood B cells infected with both ΔEBNA2 EBV and a Myc-expressing vector proliferate indefinitely on a CD40L/IL21 expressing feeder layer in vitro and cause rapid onset EBV+ BL-like tumors in NSG mice. These LMP1/EBNA2-negative Myc-driven lymphomas have wild type p53 and very low BIM, and express numerous germinal center B cell proteins (including TCF3, BACH2, Myb, CD10, CCDN3, and GCSAM) in the absence of BCL6 expression. Myc-induced activation of Myb mediates expression of many of these BL-associated proteins. We demonstrate that Myc blocks LMP1 expression both by inhibiting expression of cellular factors (STAT3 and Src) that activate LMP1 transcription and by increasing expression of proteins (DNMT3B and UHRF1) known to enhance DNA methylation of the LMP1 promoters in human BLs. These results show that latent EBV infection collaborates with Myc over-expression to induce BL-like human B-cell lymphomas in mice. As NF-κB signaling retards the growth of EBV-negative BLs, Myc-mediated repression of LMP1 may be essential for latent EBV infection and Myc translocation to collaboratively induce human BLs.

Deregulated transcription factors in the emerging cancer hallmarks

Cancer progression is a multifaceted process that entails several stages and demands the persistent expression or activation of transcription factors (TFs) to facilitate growth and survival. TFs are a cluster of proteins with DNA-binding domains that attach to promoter or enhancer DNA strands to start the transcription of genes by collaborating with RNA polymerase and other supporting proteins. They are generally acknowledged as the major regulatory molecules that coordinate biological homeostasis and the appropriate functioning of cellular components, subsequently contributing to human physiology. TFs proteins are crucial for controlling transcription during the embryonic stage and development, and the stability of different cell types depends on how they function in different cell types. The development and progression of cancer cells and tumors might be triggered by any anomaly in transcription factor function. It has long been acknowledged that cancer development is accompanied by the dysregulated activity of TF alterations which might result in faulty gene expression. Recent studies have suggested that dysregulated transcription factors play a major role in developing various human malignancies by altering and rewiring metabolic processes, modifying the immune response, and triggering oncogenic signaling cascades. This review emphasizes the interplay between TFs involved in metabolic and epigenetic reprogramming, evading immune attacks, cellular senescence, and the maintenance of cancer stemness in cancerous cells. The insights presented herein will facilitate the development of innovative therapeutic modalities to tackle the dysregulated transcription factors underlying cancer.

New Possible Ways to Use Exosomes in Diagnostics and Therapy via JAK/STAT Pathways

Exosomes have the potential to be the future of personalized diagnostics and therapy. They are nano-sized particles between 30 and 100 nm flowing in the extracellular milieu, where they mediate cell-cell communication and participate in immune system regulation. Tumor-derived exosomes (TDEs) secreted from different types of cancer cells are the key regulators of the tumor microenvironment. With their immune suppressive cargo, TDEs prevent the antitumor immune response, leading to reduced effectiveness of cancer treatment by promoting a pro-tumorigenic microenvironment. Involved signaling pathways take part in the regulation of tumor proliferation, differentiation, apoptosis, and angiogenesis. Signal transducers and activators of transcription factors (STATs) and Janus kinase (JAK) signaling pathways are crucial in malignancies and autoimmune diseases alike, and their potential to be manipulated is currently the focus of interest. In this review, we aim to discuss exosomes, TDEs, and the JAK/STAT pathways, along with mediators like interleukins, tripartite motif proteins, and interferons.

JAK/STAT Signaling and Cervical Cancer: From the Cell Surface to the Nucleus

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway constitutes a rapid signaling module from the cell surface to the nucleus, and activates different cellular responses, such as proliferation, survival, migration, invasion, and inflammation. When the JAK/STAT pathway is altered, it contributes to cancer progression and metastasis. STAT proteins play a central role in developing cervical cancer, and inhibiting the JAK/STAT signaling may be necessary to induce tumor cell death. Several cancers show continuous activation of different STATs, including cervical cancer. The constitutive activation of STAT proteins is associated with a poor prognosis and overall survival. The human papillomavirus (HPV) oncoproteins E6 and E7 play an essential role in cervical cancer progression, and they activate the JAK/STAT pathway and other signals that induce proliferation, survival, and migration of cancer cells. Moreover, there is a crosstalk between the JAK/STAT signaling cascade with other signaling pathways, where a plethora of different proteins activate to induce gene transcription and cell responses that contribute to tumor growth. Therefore, inhibition of the JAK/STAT pathway shows promise as a new target in cancer treatment. In this review, we discuss the role of the JAK/STAT pathway components and the role of the HPV oncoproteins associated with cellular malignancy through the JAK/STAT proteins and other signaling pathways to induce tumor growth.

Targeting Myc-driven stress addiction in colorectal cancer

MYC is a proto-oncogene that encodes a powerful regulator of transcription and cellular programs essential for normal development, as well as the growth and survival of various types of cancer cells. MYC rearrangement and amplification is a common cause of hematologic malignancies. In epithelial cancers such as colorectal cancer, genetic alterations in MYC are rare. Activation of Wnt, ERK/MAPK, and PI3K/mTOR pathways dramatically increases Myc levels through enhanced transcription, translation, and protein stability. Elevated Myc promotes stress adaptation, metabolic reprogramming, and immune evasion to drive cancer development and therapeutic resistance through broad changes in transcriptional and translational landscapes. Despite intense interest and effort, Myc remains a difficult drug target. Deregulation of Myc and its targets has profound effects that vary depending on the type of cancer and the context. Here, we summarize recent advances in the mechanistic understanding of Myc-driven oncogenesis centered around mRNA translation and proteostress. Promising strategies and agents under development to target Myc are also discussed with a focus on colorectal cancer.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

c-Myc plays a key role in IFN-γ-induced persistence of Chlamydia trachomatis

Chlamydia trachomatis (Ctr) can persist over extended times within their host cell and thereby establish chronic infections. One of the major inducers of chlamydial persistence is interferon-gamma (IFN-γ) released by immune cells as a mechanism of immune defence. IFN-γ activates the catabolic depletion of L-tryptophan (Trp) via indoleamine-2,3-dioxygenase (IDO), resulting in persistent Ctr. Here, we show that IFN-γ induces the downregulation of c-Myc, the key regulator of host cell metabolism, in a STAT1-dependent manner. Expression of c-Myc rescued Ctr from IFN-γ-induced persistence in cell lines and human fallopian tube organoids. Trp concentrations control c-Myc levels most likely via the PI3K-GSK3β axis. Unbiased metabolic analysis revealed that Ctr infection reprograms the host cell tricarboxylic acid (TCA) cycle to support pyrimidine biosynthesis. Addition of TCA cycle intermediates or pyrimidine/purine nucleosides to infected cells rescued Ctr from IFN-γ-induced persistence. Thus, our results challenge the longstanding hypothesis of Trp depletion through IDO as the major mechanism of IFN-γ-induced metabolic immune defence and significantly extends the understanding of the role of IFN-γ as a broad modulator of host cell metabolism.

PRMT5-activated c-Myc promote bladder cancer proliferation and invasion through up-regulating NF-κB pathway

AIM

PRMT5 and c-Myc were considered as oncogene of bladder cancer. Nevertheless, whether the interaction between of PRMT5 and c-Myc affect bladder cancer progress is unknown. Herein, we explore the above points and discuss deeply its' potential mechanism.

METHOD

5637 and T24 cells were study subjects in vitro. Western blot was used to examined the protein expression. CCK8 and transwell assay were used to analyze proliferation and invasion ability. Additionally, xenograft tumor model was established. Mice imaging experiment, Immunochemistry assay and western blot were carried out.

RESULT

Western blot result showed successful transfection of PRMT5-siRNA and c-Myc-siRNA. PRMT5-siRNA could inhibit c-Myc expression, and decrease the proliferation and invasion of bladder cells. And c-Myc overexpression could reverse inhibitory action caused by PRMT5 silence. And in vitro studies found low-expression of c-Myc reduced proliferation and invasion of tumor cells and make the NF-κB pathway inactivation. In vivo studies also demonstrated that inhibiting PRMT5 could downregulate c-Myc expression and inhibit the bladder cancer progress, and the potential mechanism was likely to be related to NF-κB signaling pathway.

CONCLUSION

In a word, low-expression of PRMT5 suppressed c-Myc, and thus inhibited proliferation and invasion ability of 5637 and T24 cells through NF-κB pathway.

Activated SUMOylation restricts MHC class I antigen presentation to confer immune evasion in cancer

Activated SUMOylation is a hallmark of cancer. Starting from a targeted screening for SUMO-regulated immune evasion mechanisms, we identified an evolutionarily conserved function of activated SUMOylation, which attenuated the immunogenicity of tumor cells. Activated SUMOylation allowed cancer cells to evade CD8⁺ T cell–mediated immunosurveillance by suppressing the MHC class I (MHC-I) antigen-processing and presentation machinery (APM). Loss of the MHC-I APM is a frequent cause of resistance to cancer immunotherapies, and the pharmacological inhibition of SUMOylation (SUMOi) resulted in reduced activity of the transcriptional repressor scaffold attachment factor B (SAFB) and induction of the MHC-I APM. Consequently, SUMOi enhanced the presentation of antigens and the susceptibility of tumor cells to CD8⁺ T cell–mediated killing. Importantly, SUMOi also triggered the activation of CD8⁺ T cells and thereby drove a feed-forward loop amplifying the specific antitumor immune response. In summary, we showed that activated SUMOylation allowed tumor cells to evade antitumor immunosurveillance, and we have expanded the understanding of SUMOi as a rational therapeutic strategy for enhancing the efficacy of cancer immunotherapies.

RNA helicase DHX15 decreases cell apoptosis by NF-κB signaling pathway in Burkitt lymphoma

Background

DHX15 is one of the RNA helicase family members involving in several biological processes. Studies have reported that overexpression of DHX15 is related to cancer progression. However, the role of DHX15 in Burkitt lymphoma (BL) and latent Epstein-Barr virus (EBV) infection remains to be elucidated.

Methods

Expression of DHX15 was measured in BL patient by immunohistochemical staining. In vitro study, a CCK-8 assay was used to analyze cell proliferation and flow cytometry was performed to assess cell cycle, apoptosis and mitochondria membrane potential. Members of NF-κB signaling pathway and apoptotic-related proteins expression were measured by western-blot. EBV latent infection products and RNA polymerase III transcripts expression were determined by quantitative real-time PCR and western-blot. In vivo study, HE, IHC, TUNEL and ISH assays were used to analyze the effect of DHX15 on subcutaneous tumor nodes formation.

Results

DHX15 was overexpressed in Burkitt lymphoma patients and tends to be associated with poor progression-free survival and poor overall survival. Knockdown of DHX15 significantly inhibited BL tumor growth, reduced cell proliferation, induced cell cycle arrest and increased cell apoptosis. Further analysis showed that canonical NF-κB signaling and its downstream targets, mitochondria and Caspase were involved in the increased cell apoptosis after DHX15 gene knockdown. Furthermore, knockdown of DHX15 reduced EBV latent infection products expression and inhibited RNA polymerase III activity.

Conclusion

DHX15 may be an oncogene in the development of BL and a potential therapeutic target for the treatment of BL and latent EBV infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02426-5.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

Selective targeting of MYC mRNA by stabilized antisense oligonucleotides

MYC is a prolific proto-oncogene driving the malignant behaviors of numerous common cancers, yet potent and selective cell-permeable inhibitors of MYC remain elusive. In order to ultimately realize the goal of therapeutic MYC inhibition in cancer, we have initiated discovery chemistry efforts aimed at inhibiting MYC translation. Here we describe a series of conformationally stabilized synthetic antisense oligonucleotides designed to target MYC mRNA (MYCASOs). To support bioactivity, we designed and synthesized this focused library of MYCASOs incorporating locked nucleic acid (LNA) bases at the 5'- and 3'-ends, a phosphorothioate backbone, and internal DNA bases. Treatment of MYC-expressing cancer cells with MYCASOs leads to a potent decrease in MYC mRNA and protein levels. Cleaved MYC mRNA in MYCASO-treated cells is detected with a sensitive 5' Rapid Amplification of cDNA Ends (RACE) assay. MYCASO treatment of cancer cell lines leads to significant inhibition of cellular proliferation while specifically perturbing MYC-driven gene expression signatures. In a MYC-induced model of hepatocellular carcinoma, MYCASO treatment decreases MYC protein levels within tumors, decreases tumor burden, and improves overall survival. MYCASOs represent a new chemical tool for in vitro and in vivo modulation of MYC activity, and promising therapeutic agents for MYC-addicted tumors.

Immune Landscape of CMV Infection in Cancer Patients: From "Canonical" Diseases Toward Virus-Elicited Oncomodulation

Human Cytomegalovirus (HCMV) is an immensely pervasive herpesvirus, persistently infecting high percentages of the world population. Despite the apparent robust host immune responses, HCMV is capable of replicating, evading host defenses, and establishing latency throughout life by developing multiple immune-modulatory strategies. HCMV has coexisted with humans mounting various mechanisms to evade immune cells and effectively win the HCMV-immune system battle mainly through maintaining its viral genome, impairing HLA Class I and II molecule expression, evading from natural killer (NK) cell-mediated cytotoxicity, interfering with cellular signaling, inhibiting apoptosis, escaping complement attack, and stimulating immunosuppressive cytokines (immune tolerance). HCMV expresses several gene products that modulate the host immune response and promote modifications in non-coding RNA and regulatory proteins. These changes are linked to several complications, such as immunosenescence and malignant phenotypes leading to immunosuppressive tumor microenvironment (TME) and oncomodulation. Hence, tumor survival is promoted by affecting cellular proliferation and survival, invasion, immune evasion, immunosuppression, and giving rise to angiogenic factors. Viewing HCMV-induced evasion mechanisms will play a principal role in developing novel adapted therapeutic approaches against HCMV, especially since immunotherapy has revolutionized cancer therapeutic strategies. Since tumors acquire immune evasion strategies, anti-tumor immunity could be prominently triggered by multimodal strategies to induce, on one side, immunogenic tumor apoptosis and to actively oppose the immune suppressive microenvironment, on the other side.

Using Flow Cytometry to Study Myc's Role in Shaping the Tumor Immune Microenvironment

Myc is deregulated in most-if not all-cancers, and it not only promotes tumor progression by inducing cell proliferation but is also responsible for tumor immune evasion. In a nutshell, MYC promotes the development of tumor-associated macrophages, impairs the cellular response to interferons, induces the expression of immunosuppressive molecules, and excludes tumor infiltrating lymphocytes (TILs) from the tumor site. Based on the insights into the role of MYC in promoting and regulating immune evasion by cancer cells, it is of special interest to study the different immune cell populations infiltrating the tumors. MYC inhibition has emerged as a potential new strategy for the treatment of cancer, directly inhibiting tumor progression while also counteracting the immunosuppressive tumor microenvironment, allowing an optimal anti-tumor immune response. Hence, this chapter describes a flow cytometry-based method to study the different immune cell subsets infiltrating the tumor by combining surface, cytoplasmic, and nuclear multicolor protein stainings.

A mean-field approach for modeling the propagation of perturbations in biochemical reaction networks

Often, the time evolution of a biochemical reaction network is crucial for determining the effects of combining multiple pharmaceuticals. Here we illustrate a mathematical framework for modeling the dominant temporal behaviour of a complicated molecular pathway or biochemical reaction network in response to an arbitrary perturbation, such as resulting from the administration of a therapeutic agent. The method enables the determination of the temporal evolution of a target protein as the perturbation propagates through its regulatory network. The mathematical approach is particularly useful when the experimental data that is available for characterizing or parameterizing the regulatory network is limited or incomplete. To illustrate the method, we consider the examples of the regulatory networks for the target proteins c-Myc and Chop, which play an important role in venetoclax resistance in acute myeloid leukemia. First we show how the networks that regulate each target protein can be reduced to a mean-field model by identifying the distinct effects that groups of proteins in the regulatory network have on the target protein. Then we show how limited protein-level data can be used to further simplify the mean-field model to pinpoint the dominant effects of the network perturbation on the target protein. This enables a further reduction in the number of parameters in the model. The result is an ordinary differential equation model that captures the temporal evolution of the expression of a target protein when one or more proteins in its regulatory network have been perturbed. Finally, we show how the dominant effects predicted by the mathematical model agree with RNA sequencing data for the regulatory proteins comprising the molecular network, despite the model not having a priori knowledge of this data. Thus, while the approach gives a simplified model for the expression of the target protein, it allows for the interpretation of the effects of the perturbation on the regulatory network itself. This method can be easily extended to sets of target proteins to model components of a larger systems biology model, and provides an approach for partially integrating RNA sequencing data and protein expression data. Moreover, it is a general approach that can be used to study drug effects on specific protein(s) in any disease or condition.

Transcriptional Regulation of Cancer Immune Checkpoints: Emerging Strategies for Immunotherapy

The study of immune evasion has gained a well-deserved eminence in cancer research by successfully developing a new class of therapeutics, immune checkpoint inhibitors, such as pembrolizumab and nivolumab, anti-PD-1 antibodies. By aiming at the immune checkpoint blockade (ICB), these new therapeutics have advanced cancer treatment with notable increases in overall survival and tumor remission. However, recent reports reveal that 40-60% of patients fail to benefit from ICB therapy due to acquired resistance or tumor relapse. This resistance may stem from increased expression of co-inhibitory immune checkpoints or alterations in the tumor microenvironment that promotes immune suppression. Because these mechanisms are poorly elucidated, the transcription factors that regulate immune checkpoints, known as "master regulators", have garnered interest. These include AP-1, IRF-1, MYC, and STAT3, which are known to regulate PD/PD-L1 and CTLA-4. Identifying these and other potential master regulators as putative therapeutic targets or biomarkers can be facilitated by mining cancer literature, public datasets, and cancer genomics resources. In this review, we describe recent advances in master regulator identification and characterization of the mechanisms underlying immune checkpoints regulation, and discuss how these master regulators of immune checkpoint molecular expression can be targeted as a form of auxiliary therapeutic strategy to complement traditional immunotherapy.

MYC Activity Inference Captures Diverse Mechanisms of Aberrant MYC Pathway Activation in Human Cancers

c-MYC (MYC) is deregulated in more than 50% of all cancers. While MYC amplification is the most common MYC-deregulating event, many other alterations can increase MYC activity. We thus systematically investigated MYC pathway activity across different tumor types. Using a logistic regression framework, we established tumor type-specific, transcriptomic-based MYC activity scores that can accurately capture MYC activity. We show that MYC activity scores reflect a variety of MYC-regulating mechanisms, including MYCL and/or MYCN amplification, MYC promoter methylation, MYC mRNA expression, lncRNA PVT1 expression, MYC mutations, and viral integrations near the MYC locus. Our MYC activity score incorporates all of these mechanisms, resulting in better prognostic predictions compared with MYC amplification status, MYC promoter methylation, and MYC mRNA expression in several cancer types. In addition, we show that tumor proliferation and immune evasion are likely contributors to this reduction in survival. Finally, we developed a MYC activity signature for liquid tumors in which MYC translocation is commonly observed, suggesting that our approach can be applied to different types of genomic alterations. In conclusion, we developed a MYC activity score that captures MYC pathway activity and is clinically relevant. IMPLICATIONS: By using cancer type-specific MYC activity profiles, we were able to assess MYC activity across many more tumor types than previously investigated. The range of different MYC-related alterations captured by our MYC activity score can be used to facilitate the application of future MYC inhibitors and aid physicians to preselect patients for targeted therapy.

The new role for an old guy: MYC as an immunoplayer

As an oncogene, myelocytomatosis oncogene (MYC) is implicated in the concept of "oncogene addiction," where switching off the oncogene leads to the cell cycle arrest and cell differentiation. However, recent data suggest that MYC also controls the establishment of the tumour microenvironment and that "oncogene addiction" actually has a strong immune background. Evaluation of the MYC role in the immunoediting process led to the speculation that cancer just uses and distorts the physiological mechanism by which MYC normally prevents rapidly proliferating cells from the elicitation of an autoimmune response. Concordantly, elevated levels of MYC and induction of immunosuppressive molecules are observed during the processes of growth and development, tissue repair, placenta development, and so forth, implying that MYC may be involved in saving regular physiologically proliferating cells from the immune system attack. Even more, a growing body of evidence suggests MYC involvement in the shaping of the adaptive immune response, immunological memory development, and establishment of immunotolerance. This paper offers an overview of MYC actions in the context of modulation of the immune response in pathological and physiological conditions. The determination of such a new role for a well-known oncogene opens new perspectives in biomedicine, and consequently, in the treatment of various pathological conditions.

Impact of MYC on Anti-Tumor Immune Responses in Aggressive B Cell Non-Hodgkin Lymphomas: Consequences for Cancer Immunotherapy

Simple Summary

The human immune system has several mechanisms to attack and eliminate lymphomas. However, the MYC oncogene is thought to facilitate escape from this anti-tumor immune response. Since patients with MYC overexpressing lymphomas face a significant dismal prognosis after treatment with standard immunochemotherapy, understanding the role of MYC in regulating the anti-tumor immune response is highly relevant. In this review, we describe the mechanisms by which MYC attenuates the anti-tumor immune responses in B cell non-Hodgkin lymphomas. We aim to implement this knowledge in the deployment of novel immunotherapeutic approaches. Therefore, we also provide a comprehensive overview of current immunotherapeutic options and we discuss potential future treatment strategies for MYC overexpressing lymphomas.

Abstract

Patients with MYC overexpressing high grade B cell lymphoma (HGBL) face significant dismal prognosis after treatment with standard immunochemotherapy regimens. Recent preclinical studies indicate that MYC not only contributes to tumorigenesis by its effects on cell proliferation and differentiation, but also plays an important role in promoting escape from anti-tumor immune responses. This is of specific interest, since reversing tumor immune inhibition with immunotherapy has shown promising results in the treatment of both solid tumors and hematological malignancies. In this review, we outline the current understanding of impaired immune responses in B cell lymphoid malignancies with MYC overexpression, with a particular emphasis on diffuse large B cell lymphoma. We also discuss clinical consequences of MYC overexpression in the treatment of HGBL with novel immunotherapeutic agents and potential future treatment strategies.

Putative role of marginal zone B cells in pathophysiological processes

The maintenance of inner integrity of an organism is founded on the proper performance of two immunity branches, innate and adaptive immune responses. Recently, it became apparent that subset of splenic B cells named marginal zone B cells (MZB cells) exhibits unique developmental and functional features that bridge these two immunity branches. Strategically positioned at the site where blood and lymph are filtered, MZB cells represent a population of sentinels that rapidly proliferate and differentiate into IgM plasmablast cells when encountered with blood-borne, thymus-independent (TI) Ags. Moreover, MZB cells have intrinsic capability to induce potent CD4⁺ helper T cell response and cytokine production upon stimulation with soluble antigens. Due to their ability to overcome a time gap prior the establishment of the full adaptive response towards pathogens, MZB cells connect and direct innate and adaptive immunity. An additional interesting characteristic of MZB cells is capacity to function as regulatory cells in autoimmune processes. MZB cells may also contribute to the control of autoimmunity via the induction of tolerance by apoptotic cells. Importantly, in the clear association with inflammation and autoimmunity, MZB cells may transform into MALT lymphoma, representing a concurrence point for the infection, immunity and malignancy. This paper presents an insight into the complex biology of marginal zone B cells and their role in intertwining and directing innate and adaptive immune processes at the physiological and pathological level.

MYC functions as a switch for natural killer cell-mediated immune surveillance of lymphoid malignancies

The MYC oncogene drives T- and B- lymphoid malignancies, including Burkitt's lymphoma (BL) and Acute Lymphoblastic Leukemia (ALL). Here, we demonstrate a systemic reduction in natural killer (NK) cell numbers in SRα-tTA/Tet-O-MYCON mice bearing MYC-driven T-lymphomas. Residual mNK cells in spleens of MYCON T-lymphoma-bearing mice exhibit perturbations in the terminal NK effector differentiation pathway. Lymphoma-intrinsic MYC arrests NK maturation by transcriptionally repressing STAT1/2 and secretion of Type I Interferons (IFNs). Treating T-lymphoma-bearing mice with Type I IFN improves survival by rescuing NK cell maturation. Adoptive transfer of mature NK cells is sufficient to delay both T-lymphoma growth and recurrence post MYC inactivation. In MYC-driven BL patients, low expression of both STAT1 and STAT2 correlates significantly with the absence of activated NK cells and predicts unfavorable clinical outcomes. Our studies thus provide a rationale for developing NK cell-based therapies to effectively treat MYC-driven lymphomas in the future.

Immunogenic cell death in colon cancer prevention and therapy

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. The colonic mucosa constitutes a critical barrier and a major site of immune regulation. The immune system plays important roles in cancer development and treatment, and immune activation caused by chronic infection or inflammation is well-known to increase cancer risk. During tumor development, neoplastic cells continuously interact with and shape the tumor microenvironment (TME), which becomes progressively immunosuppressive. The clinical success of immune checkpoint blockade therapies is limited to a small set of CRCs with high tumor mutational load and tumor-infiltrating T cells. Induction of immunogenic cell death (ICD), a type of cell death eliciting an immune response, can therefore help break the immunosuppressive TME, engage the innate components, and prime T cell-mediated adaptive immunity for long-term tumor control. In this review, we discuss the current understanding of ICD induced by antineoplastic agents, the influence of driver mutations, and recent developments to harness ICD in colon cancer. Mechanism-guided combinations of ICD-inducing agents with immunotherapy and actionable biomarkers will likely offer more tailored and durable benefits to patients with colon cancer.

Genetic Programs Driving Oncogenic Transformation: Lessons from in Vitro Models

Cancer complexity relies on the intracellular pleiotropy of oncogenes/tumor suppressors and in the strong interplay between tumors and micro- and macro-environments. Here we followed a reductionist approach, by analyzing the transcriptional adaptations induced by three oncogenes (RAS, MYC, and HDAC4) in an isogenic transformation process. Common pathways, in place of common genes became dysregulated. From our analysis it emerges that, during the process of transformation, tumor cells cultured in vitro prime some signaling pathways suitable for coping with the blood supply restriction, metabolic adaptations, infiltration of immune cells, and for acquiring the morphological plasticity needed during the metastatic phase. Finally, we identified two signatures of genes commonly regulated by the three oncogenes that successfully predict the outcome of patients affected by different cancer types. These results emphasize that, in spite of the heterogeneous mutational burden among different cancers and even within the same tumor, some common hubs do exist. Their location, at the intersection of the various signaling pathways, makes a therapeutic approach exploitable.

Epigenomic Reordering Induced by Polycomb Loss Drives Oncogenesis but Leads to Therapeutic Vulnerabilities in Malignant Peripheral Nerve Sheath Tumors

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive sarcoma with recurrent loss-of-function alterations in polycomb-repressive complex 2 (PRC2), a histone-modifying complex involved in transcriptional silencing. To understand the role of PRC2 loss in pathogenesis and identify therapeutic targets, we conducted parallel global epigenomic and proteomic analysis of archival formalin-fixed, paraffin-embedded (FFPE) human MPNST with and without PRC2 loss (MPNST_LOSS vs. MPNST_RET). Loss of PRC2 resulted in increased histone posttranslational modifications (PTM) associated with active transcription, most notably H3K27Ac and H3K36me2, whereas repressive H3K27 di- and trimethylation (H3K27me2/3) marks were globally lost without a compensatory gain in other repressive PTMs. Instead, DNA methylation globally increased in MPNST_LOSS. Epigenomic changes were associated with upregulation of proteins in growth pathways and reduction in IFN signaling and antigen presentation, suggesting a role for epigenomic changes in tumor progression and immune evasion, respectively. These changes also resulted in therapeutic vulnerabilities. Knockdown of NSD2, the methyltransferase responsible for H3K36me2, restored MHC expression and induced interferon pathway expression in a manner similar to PRC2 restoration. MPNST_LOSS were also highly sensitive to DNA methyltransferase and histone deacetylase (HDAC) inhibitors. Overall, these data suggest that global loss of PRC2-mediated repression renders MPNST differentially dependent on DNA methylation to maintain transcriptional integrity and makes them susceptible to therapeutics that promote aberrant transcription initiation. SIGNIFICANCE: Global profiling of histone PTMs and protein expression in archival human MPNST illustrates how PRC2 loss promotes oncogenesis but renders tumors vulnerable to pharmacologic modulation of transcription.See related commentary by Natarajan and Venneti, p. 3172.

MYC inhibition increases PD-L1 expression induced by IFN-γ in hepatocellular carcinoma cells

The effectiveness of immunotherapy targeting the immune checkpoint PD-L1/PD-1 pathway highlights importance of elucidating the regulatory mechanisms of PD-L1 expression in cancer cells. Previous studies demonstrate that oncogene MYC up-regulates PD-L1 expression in lymphomas. In the present study, we investigated the regulatory role of MYC in the PD-L1 expression induced by IFN-γ in HCC cells. Unexpectedly, knockdown of MYC expression using siRNA assay increased the inducible expression of PD-L1 both at mRNA and protein levels. Mechanistically, the inhibition of MYC elevated expression of STAT1, a critical component of IFN-γ signaling pathway, leading to the elevation of PD-L1 expression in HCC cells exposed to IFN-γ. These results suggest that MYC may down-regulate PD-L1 expression in the context of HCC. This study implicates that a combination therapy targeting MYC function and PD-L1/PD-1 pathway might be effective for treatment of HCC.

Immunogenic effects of chemotherapy-induced tumor cell death

Emerging evidence suggests that the clinical success of conventional chemotherapy is not solely attributed to tumor cell toxicity, but also results from the restoration of immunosurveillance, which has been largely neglected in the past preclinical and clinical research. Antitumor immune response can be primed by immunogenic cell death (ICD), a type of cell death characterized by cell-surface translocation of calreticulin (CRT), extracellular release of ATP and high mobility group box 1 (HMGB1), and stimulation of type I interferon (IFN) responses. Here we summarize recent studies showing conventional chemotherapeutics as ICD inducers, which are capable of modulating tumor infiltrating lymphocytes (TILs) and reactivating antitumor immunity within an immuno-suppressive microenvironment. Such immunological effects of conventional chemotherapy are likely critical for better prognosis of cancer patients. Furthermore, combination of ICD-inducing chemotherapeutics with immunotherapy is a promising approach for improving the clinical outcomes of cancer patients.

Epigenetic Therapy Ties MYC Depletion to Reversing Immune Evasion and Treating Lung Cancer

Combining DNA-demethylating agents (DNA methyltransferase inhibitors [DNMTis]) with histone deacetylase inhibitors (HDACis) holds promise for enhancing cancer immune therapy. Herein, pharmacologic and isoform specificity of HDACis are investigated to guide their addition to a DNMTi, thus devising a new, low-dose, sequential regimen that imparts a robust anti-tumor effect for non-small-cell lung cancer (NSCLC). Using in-vitro-treated NSCLC cell lines, we elucidate an interferon α/β-based transcriptional program with accompanying upregulation of antigen presentation machinery, mediated in part through double-stranded RNA (dsRNA) induction. This is accompanied by suppression of MYC signaling and an increase in the T cell chemoattractant CCL5. Use of this combination treatment schema in mouse models of NSCLC reverses tumor immune evasion and modulates T cell exhaustion state towards memory and effector T cell phenotypes. Key correlative science metrics emerge for an upcoming clinical trial, testing enhancement of immune checkpoint therapy for NSCLC.

Cytokines associated with Burkitt's lymphoma in western Kenya

Objective

Burkitt’s lymphoma (BL) is a common aggressive non-Hodgkin’s lymphoma in East and Central Africa among children. Persistent infections with Epstein Barr virus or Plasmodium falciparum are associated with immune hyperstimulation. It is hypothesised that inadvertent cytokine responses to infections indirectly or directly influence B cell neoplastic transformation through c-myelocytomatosis (c-myc) gene translocation. We sought to describe cytokines in children and adolescents with BL. Participants were recruited from western Kenya with parental consent, diagnosis confirmed using histology and consensus panel of immunohistochemistry antibodies. T helper1/2/17A and transforming growth factor-β1 (TGF-β1) cytokines were estimated using cytometric bead array in plasma. Complete blood counts (CBC) were determined by Beckman Coulter^®.

Results

Out of 104 enrolled participants, 32% were confirmed BL and 68% grouped as non-BL. Mean (pg/ml) levels of cytokines in BL and non-BL were: interleukin (IL)-6 100.3 and 39.4 p = 0.152; IL-10 11.5 and 12.5 p = 0.363; IL-17A 17.8 and 64.9 p = 0.094 respectively. Expressions of interferon-γ, IL-2 and tumour necrosis factor-α were low and TGF-β1 undetectable in both groups. Mean CBC differed between the two groups before and after chemotherapy, WBC being significantly so. Interleukin-6, IL-17A and IL-10 responses to infections in the study area may be associated with pathogenesis and be potential therapeutic targets.

Amplification of N-Myc is associated with a T-cell-poor microenvironment in metastatic neuroblastoma restraining interferon pathway activity and chemokine expression

Immune checkpoint inhibitors have significantly improved the treatment of several cancers. T-cell infiltration and the number of neoantigens caused by tumor-specific mutations are correlated to favorable responses in cancers with a high mutation load. Accordingly, checkpoint immunotherapy is thought to be less effective in tumors with low mutation frequencies such as neuroblastoma, a neuroendocrine tumor of early childhood with poor outcome of the high-risk disease group. However, spontaneous regressions and paraneoplastic syndromes seen in neuroblastoma patients suggest substantial immunogenicity. Using an integrative transcriptomic approach, we investigated the molecular characteristics of T-cell infiltration in primary neuroblastomas as an indicator of pre-existing immune responses and potential responsiveness to checkpoint inhibition. Here, we report that a T-cell-poor microenvironment in primary metastatic neuroblastomas is associated with genomic amplification of the MYCN (N-Myc) proto-oncogene. These tumors exhibited lower interferon pathway activity and chemokine expression in line with reduced immune cell infiltration. Importantly, we identified a global role for N-Myc in the suppression of interferon and pro-inflammatory pathways in human and murine neuroblastoma cell lines. N-Myc depletion potently enhanced targeted interferon pathway activation by a small molecule agonist of the cGAS-STING innate immune pathway. This promoted chemokine expression including Cxcl10 and T-cell recruitment in microfluidics migration assays. Hence, our data suggest N-Myc inhibition plus targeted IFN activation as adjuvant strategy to enforce cytotoxic T-cell recruitment in MYCN-amplified neuroblastomas.

MYC: Master Regulator of Immune Privilege

Cancers are often initiated by genetic events that activate proto-oncogenes or inactivate tumor-suppressor genes. These events are also crucial for sustained tumor cell proliferation and survival, a phenomenon described as oncogene addiction. In addition to this cell-intrinsic role, recent evidence indicates that oncogenes also directly regulate immune responses, leading to immunosuppression. Expression of many oncogenes or loss of tumor suppressors induces the expression of immune checkpoints that regulate the immune response, such as PD-L1. We discuss here how oncogenes, and in particular MYC, suppress immune surveillance, and how oncogene-targeted therapies may restore the immune response against tumors.

Synergy of interleukin 10 and toll-like receptor 9 signalling in B cell proliferation: Implications for lymphoma pathogenesis

A network of autocrine and paracrine signals defines B cell homeostasis and is thought to be involved in transformation processes. Investigating interactions of these microenvironmental factors and their relation to proto-oncogenes as c-Myc (MYC) is fundamental to understand the biology of B cell lymphoma. Therefore, B cells with conditional MYC expression were stimulated with CD40L, insulin-like growth factor 1, α-IgM, Interleukin-10 (IL10) and CpG alone or in combination. The impact of forty different interventions on cell proliferation was investigated in MYC deprived cells and calculated by linear regression. Combination of CpG and IL10 led to a strong synergistic activation of cell proliferation (S-phase/doubling of total cell number) comparable to cells with high MYC expression. A synergistic up-regulation of CDK4, CDK6 and CCND3 expression by IL10 and CpG treatment was causal for this proliferative effect as shown by qRT-PCR analysis and inhibition of the CDK4/6 complex by PD0332991. Furthermore, treatment of stimulated MYC deprived cells with MLN120b, ACHP, Pyridone 6 or Ruxolitinib showed that IL10/CpG induced proliferation and CDK4 expression were JAK/STAT3 and IKK/NF-κB dependent. This was further supported by STAT3 and p65/RELA knockdown experiments, showing strongest effects on cell proliferation and CDK4 expression after double knockdown. Additionally, chromatin immunoprecipitation revealed a dual binding of STAT3 and p65 to the proximal promotor of CDK4 after IL10/CpG treatment. Therefore, the observed synergism of IL10R and TLR9 signalling was able to induce proliferation in a comparable way as aberrant MYC and might play a role in B cell homeostasis or transformation.

Recent insights in the pathogenesis of post-transplantation lymphoproliferative disorders

Post-transplant lymphoproliferative disorder (PTLD) is an aggressive complication of solid organ and hematopoietic stem cell transplantation that arises in up to 20% of transplant recipients. Infection or reactivation of the Epstein-Barr virus (EBV), a ubiquitous human herpesvirus, in combination with chronic immunosuppression are considered as the main predisposing factors, however insight in PTLD biology is fragmentary. The study of PTLD is complicated by its morphological heterogeneity and the lack of prospective trials, which also impede treatment optimization. Furthermore, the broad spectrum of underlying disorders and the graft type represent important confounding factors. PTLD encompasses different malignant subtypes that resemble histologically similar lymphomas in the general population. Post-transplant diffuse large B-cell lymphoma (PT-DLBCL), Burkitt lymphoma (PT-BL) and plasmablastic lymphoma (PT-PBL) occur most frequently. However, in many studies various EBV⁺ and EBV^- PTLD subtypes are pooled, complicating the interpretation of the results. In this review, studies of the gene expression pattern, the microenvironment and the genetic profile of PT-DLBCL, PT-BL and PT-PBL are summarized to better understand the mechanisms underlying post-transplantation lymphomagenesis. Based on the available findings we propose stratification of PTLD according to the histological subtype and the EBV status to facilitate the interpretation of future studies and the establishment of clinical trials.

Transcriptional Repression of IFN Regulatory Factor 7 by MYC Is Critical for Type I IFN Production in Human Plasmacytoid Dendritic Cells

Type I IFNs are crucial mediators of human innate and adaptive immunity and are massively produced from plasmacytoid dendritic cells (pDCs). IFN regulatory factor (IRF)7 is a critical regulator of type I IFN production when pathogens are detected by TLR 7/9 in pDC. However, hyperactivation of pDC can cause life-threatening autoimmune diseases. To avoid the deleterious effects of aberrant pDC activation, tight regulation of IRF7 is required. Nonetheless, the detailed mechanisms of how IRF7 transcription is regulated in pDC are still elusive. MYC is a well-known highly pleiotropic transcription factor; however, the role of MYC in pDC function is not well defined yet. To identify the role of transcription factor MYC in human pDC, we employed a knockdown technique using human pDC cell line, GEN2.2. When we knocked down MYC in the pDC cell line, production of IFN-stimulated genes was dramatically increased and was further enhanced by the TLR9 agonist CpGB. Interestingly, MYC is shown to be recruited to the IRF7 promoter region through interaction with nuclear receptor corepressor 2/histone deacetylase 3 for its repression. In addition, activation of TLR9-mediated NF-κB and MAPK and nuclear translocation of IRF7 were greatly enhanced by MYC depletion. Pharmaceutical inhibition of MYC recovered IRF7 expression, further confirming the negative role of MYC in the antiviral response by pDC. Therefore, our results identify the novel immunomodulatory role of MYC in human pDC and may add to our understanding of aberrant pDC function in cancer and autoimmune disease.

Downregulation of c-Myc is involved in TLR3-mediated tumor death of neuroblastoma xenografts

Neuroblastoma (NB) is the deadliest pediatric solid tumor due to its pleomorphic molecular characteristics. In the innate immune system, toll-like receptor 3 (TLR3) recognizes viral double-stranded RNAs to initiate immune signaling. Positive TLR3 expression indicates a favorable prognosis in NB patients, and is associated with MYCN-non-amplified. However, TLR3-mediated innate immune responses remain elusive in NB. In this study, we attempted to dissect the molecular mechanism underlying TLR3-agonist polyinosinic-polycytidylic acid [poly(I:C)] treatment in NB in vivo. We established NB xenograft models in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice with MYCN-amplified SK-N-DZ (DZ) cells or MYCN-non-amplified SK-N-AS (AS) cells. Poly(I:C) treatment led to significant tumor regression in AS xenografts, but not in DZ xenografts. Through immunohistochemical analysis, significant suppression of tumor proliferation, downregulation of c-Myc expression, and upregulation of TLR3 expression were found in the treatment group. Poly(I:C) inducing activation of TLR3/IRF3-mediated innate immunity associated with downregulation of c-Myc can be found in MYCN-non-amplified SK-N-AS cells, but not in MYCN-amplified BE(2)-M17 cells. Knockdown of TLR3 disturbed poly(I:C)-induced suppression of c-Myc and upregulation of p-IRF3 in AS cells. Furthermore, poly(I:C) treatment upregulated active NF-κB, mitochondrial antioxidant manganese superoxide dismutase and 8-hydroxydeoxyguanosine, which works with reactive oxygen species (ROS) generation and DNA damage. Upregulation of active caspase 3 and cleaved poly [ADP-ribose] polymerase 1 were found in poly(I:C)-treated AS xenografts, which indicates the induction of apoptosis. Thus, our results suggest that c-Myc overexpression may increase sensitivity to poly(I:C)-induced tumor growth arrest and ROS-mediated apoptosis in NB. This study demonstrates that c-Myc protein expression has an important role in TLR3-induced innate immune responses, providing future treatment recommendations.

Reconstruction of gene regulatory networks reveals chromatin remodelers and key transcription factors in tumorigenesis

Background

Alterations in genetic and epigenetic landscapes are known to contribute to the development of different types of cancer. However, the mechanistic links between transcription factors and the epigenome which coordinate the deregulation of gene networks during cell transformation are largely unknown.

Methods

We used an isogenic model of stepwise tumorigenic transformation of human primary cells to monitor the progressive deregulation of gene networks upon immortalization and oncogene-induced transformation. We applied a systems biology approach by combining transcriptome and epigenome data for each step during transformation and integrated transcription factor–target gene associations in order to reconstruct the gene regulatory networks that are at the basis of the transformation process.

Results

We identified 142 transcription factors and 24 chromatin remodelers/modifiers (CRMs) which are preferentially associated with specific co-expression pathways that originate from deregulated gene programming during tumorigenesis. These transcription factors are involved in the regulation of divers processes, including cell differentiation, the immune response, and the establishment/modification of the epigenome. Unexpectedly, the analysis of chromatin state dynamics revealed patterns that distinguish groups of genes which are not only co-regulated but also functionally related. Decortication of transcription factor targets enabled us to define potential key regulators of cell transformation which are engaged in RNA metabolism and chromatin remodeling.

Conclusions

We reconstructed gene regulatory networks that reveal the alterations occurring during human cellular tumorigenesis. Using these networks we predicted and validated several transcription factors as key players for the establishment of tumorigenic traits of transformed cells. Our study suggests a direct implication of CRMs in oncogene-induced tumorigenesis and identifies new CRMs involved in this process. This is the first comprehensive view of the gene regulatory network that is altered during the process of stepwise human cellular tumorigenesis in a virtually isogenic system.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0310-3) contains supplementary material, which is available to authorized users.

N-Myc expression enhances the oncolytic effects of vesicular stomatitis virus in human neuroblastoma cells

N-myc oncogene amplification is associated but not present in all cases of high-risk neuroblastoma (NB). Since oncogene expression could often modulate sensitivity to oncolytic viruses, we wanted to examine if N-myc expression status would determine virotherapy efficacy to high-risk NB. We showed that induction of exogenous N-myc in a non-N-myc-amplified cell line background (TET-21N) increased susceptibility to oncolytic vesicular stomatitis virus (mutant VSVΔM51) and alleviated the type I IFN-induced antiviral state. Cells with basal N-myc, on the other hand, were less susceptible to virus-induced oncolysis and established a robust IFN-mediated antiviral state. The same effects were also observed in NB cell lines with and without N-myc amplification. Microarray analysis showed that N-myc overexpression in TET-21N cells downregulated IFN-stimulated genes (ISGs) with known antiviral functions. Furthermore, virus infection caused significant changes in global gene expression in TET-21N cells overexpressing N-myc. Such changes involved ISGs with various functions. Therefore, the present study showed that augmented susceptibility to VSVΔM51 by N-myc at least involves downregulation of ISGs with antiviral functions and alleviation of the IFN-stimulated antiviral state. Our studies suggest the potential utility of N-myc amplification/overexpression as a predictive biomarker of virotherapy response for high-risk NB using IFN-sensitive oncolytic viruses.

Disentangling the relationship between tumor genetic programs and immune responsiveness

Correlative studies in humans have demonstrated that an active immune microenvironment characterized by the presence of a T-helper 1 immune response typifies a tumor phenotype associated with better outcome and increased responsiveness to immune manipulation. This phenotype also signifies the counter activation of immune-regulatory mechanisms. Variables modulating the development of an effective anti-tumor immune response are increasingly scrutinized as potential therapeutic targets. Genetic alterations of cancer cells that functionally influence intratumoral immune response include mutational load, specific mutations of genes involved in oncogenic pathways and copy number aberrations involving chemokine and cytokine genes. Inhibiting oncogenic pathways that prevent the development of the immune-favorable cancer phenotype may complement modern immunotherapeutic approaches.

Effects of mTOR and calcineurin inhibitors combined therapy in Epstein-Barr virus positive and negative Burkitt lymphoma cells

Post-transplant lymphoproliferative disorder is a severe complication in solid organ transplant recipients, which is highly associated with Epstein-Barr virus infection in pediatric patients and occasionally presents as Burkitt- or Burkitt-like lymphoma. The mammalian target of rapamycin (mTOR) pathway has been described as a possible antitumor target whose inhibition may influence lymphoma development and proliferation after pediatric transplantation. We treated Epstein-Barr virus positive (Raji and Daudi) and negative (Ramos) human Burkitt lymphoma derived cells with mTOR inhibitor everolimus alone and in combination with clinically relevant immunosuppressive calcineurin inhibitors (tacrolimus or cyclosporin A). Cell proliferation, toxicity, and mitochondrial metabolic activity were analyzed. The effect on mTOR Complex 1 downstream targets p70 S6 kinase, eukaryotic initiation factor 4G, and S6 ribosomal protein activation was also investigated. We observed that treatment with everolimus alone significantly decreased Burkitt lymphoma cell proliferation and mitochondrial metabolic activity. Everolimus in combination with cyclosporin A had a stronger suppressive effect in Epstein-Barr virus negative but not in Epstein-Barr virus positive cells. In contrast, tacrolimus completely abolished the everolimus-mediated suppressive effects. Moreover, we showed a significant decrease in activation of mTOR Complex 1 downstream targets after treatment with everolimus that was attenuated when combined with tacrolimus, but not with cyclosporin A. For the first time we showed the competitive effect between everolimus and tacrolimus when used as combination therapy on Burkitt lymphoma derived cells. Thus, according to our in vitro data, the combination of calcineurin inhibitor cyclosporin A with everolimus is preferred to the combination of tacrolimus and everolimus.

Elevation of c-MYC disrupts HLA class II-mediated immune recognition of human B cell tumors

Elevated levels of the transcription factor c-myc are strongly associated with various cancers, and in particular B cell lymphomas. Although many of c-MYC's functions have been elucidated, its effect on the presentation of Ag through the HLA class II pathway has not been reported previously. This is an issue of considerable importance, given the low immunogenicity of many c-MYC-positive tumors. We report in this paper that increased c-MYC expression has a negative effect on the ability of B cell lymphomas to functionally present Ags/peptides to CD4(+) T cells. This defect was associated with alterations in the expression of distinct cofactors as well as interactions of antigenic peptides with class II molecules required for the presentation of class II-peptide complexes and T cell engagement. Using early passage Burkitt's lymphoma (BL) tumors and transformed cells, we show that compared with B lymphoblasts, BL cells express decreased levels of the class II editor HLA-DM, lysosomal thiol-reductase GILT, and a 47-kDa enolase-like protein. Functional Ag presentation was partially restored in BL cells treated with a c-MYC inhibitor, demonstrating the impact of this oncogene on Ag recognition. This restoration of HLA class II-mediated Ag presentation in early passage BL tumors/cells was linked to enhanced HLA-DM expression and a concurrent decrease in HLA-DO in BL cells. Taken together, these results reveal c-MYC exerts suppressive effects at several critical checkpoints in Ag presentation, which contribute to the immunoevasive properties of BL tumors.

Hepatitis C virus replication in mouse cells is restricted by IFN-dependent and -independent mechanisms

BACKGROUND & AIMS

Current treatment strategies for hepatitis C virus (HCV) infection include pegylated interferon (IFN)-alfa and ribavirin. Approximately 50% of patients control HCV infection after treatment, but the broad range of patients' outcomes and responses to treatment, among all genotypes, indicates a role for host factors. Although the IFN system is important in limiting HCV replication, the virus has evolved mechanisms to circumvent the IFN response. However, direct, IFN-independent antiviral processes also might help control HCV replication. We examined the role of IFN-independent responses against HCV replication.

METHODS

We analyzed replication of the subgenomic JFH1 replicon in embryonic fibroblasts and primary hepatocytes from mice with disruptions in genes encoding factors in the IFN-dependent and alternative antiviral pathways (signal transducers and activators of transcription 1 [STAT1], protein kinase R, interferon regulatory factors (IRF) IRF-1, IRF-3, IRF-5, IRF-7, mitochondrial antiviral signaling molecule [MAVS], and IFN receptor [IFNAR]). We also assessed the effects of expression of these factors by mouse primary hepatocytes on HCV replication.

RESULTS

In addition to IRF-3- and IFN-mediated antiviral responses, IFN-independent, but IRF-1- and IRF-5-dependent mechanisms, restrict HCV replication in mouse embryonic fibroblasts. In primary hepatocytes these IFN-independent require MAVS and IRF-1.

CONCLUSIONS

HCV replication is limited by interferon-mediated pathways as well pathways that are independent of type I IFNs. IRF1 and IRF5 control IFN-independent signaling events that lead to antiviral responses. We observed antiviral roles of IRF1 and IRF5 that were IFN-independent and cell-type specific. These mechanisms are important in controlling viruses that interfere with the IFN signaling because cells retain the ability to induce functional but local antiviral states through expression of interferon-stimulated genes.

Early gene expression changes by Epstein-Barr virus infection of B-cells indicate CDKs and survivin as therapeutic targets for post-transplant lymphoproliferative diseases

Lymphoproliferative diseases (LPDs) associated with Epstein-Barr virus (EBV) infection cause significant morbidity and mortality in bone marrow and solid organ transplant recipients. To gain insight into LPD pathogenesis and to identify potential effective therapeutic approaches, we investigated early molecular events leading to B-cell transformation by gene expression profiling of EBV-infected B-cells from tonsils by Affymetrix microarray 72 hr postinfection when the B-cells hyperproliferation phase starts. Cell cycle and apoptosis were the most significantly affected pathways and enriched gene sets. In particular, we found significantly increased expression of cyclin-dependent kinase (CDK)1 and CCNB1 (cyclin B1) and of one of their downstream targets BIRC5 (survivin). Importantly, the strong upregulation of the antiapoptotic protein survivin was confirmed in lymphoblastoid cell lines (LCLs) and 71% of EBV-positive post-transplant EBV-LPD lesions scored positive for survivin. The validity of early transforming events for the identification of therapeutic targets for EBV-LPD was confirmed by the marked antiproliferative effect of the CDK inhibitor flavopiridol on LCLs and by the strong induction of apoptosis by survivin inhibition with YM155 or terameprocol. Our results suggest that targeting of CDKs and/or survivin in post-transplant EBV-LPD by specific inhibitors might be an important approach to control and eliminate EBV-transformed B-cells that should be further considered.

BCL10 down-regulation in peripheral T-cell lymphomas

The BCL10 gene encodes for a T-cell receptor signaling downstream protein involved in nuclear factor κB activation. It is expressed in normal lymphoid tissues and in several B-non Hodgkin lymphomas, its aberrant function being related to the pathogenesis of certain subtypes. Conversely, conflicting data are available concerning BCL10 expression in peripheral T cell lymphomas. We analyzed BCL10 expression in peripheral T cell lymphomas and correlated it with NFκB activation, proliferation, phenotypic aberration, and survival. First, gene expression analysis of 40 peripheral T cell lymphomas (28 peripheral T cell lymphomas/not otherwise specified, 6 anaplastic large cell lymphomas, and 6 angioimmunoblastic lymphomas), 4 reactive lymph nodes, and 20 samples of normal T-lymphocytes, showed significantly lower BCL10 gene expression in all tumors in comparison to normal samples, the lowest values being detected in anaplastic large cell lymphoma. Secondly, we studied the immunohistochemical expression of BCL10 in 52 peripheral T cell lymphomas/not otherwise specified on tissue microarrays. BCL10 was expressed in 10/52 cases (19%), not showing any significant correlation with either expression of Ki-67 and the T-cell markers or NFκB activation. Furthermore, BCL10 expression was not associated with peculiar gene expression profiles. Finally, we did not find significant correlations with progression free survival and overall survival, although a favorable trend was recorded in BCL10(+) cases. In conclusion, BCL10 was commonly down-regulated in peripheral T cell lymphomas, suggest the T-cell receptor signaling cascade for future characterization.

B7-H1, which represses EBV-immortalized B cell killing by autologous T and NK cells, is oppositely regulated by c-Myc and EBV latency III program at both mRNA and secretory lysosome levels

EBV-immortalized B cells induce a complex immune response such that the virus persists as a clinically silent infection for the lifetime of the infected host. B7-H1, also called PD-L1, is a cosignaling molecule of the B7 family that can inhibit activated T cell effectors by interaction with its receptor PD-1. In this work, we have studied the dependence of B7-H1 on NF-κB and c-Myc, the two main transcription factors in EBV latency III proliferating B cells, on various lymphoblastoid and Burkitt lymphoma cell lines, some of them being inducible or not for the EBV latency III program and/or for c-Myc. We found that B7-H1 repressed killing of EBV-immortalized B cells by their autologous T and NK cells. At the mRNA level, NF-κB was a weak inducer whereas c-Myc was a strong repressor of B7-H1 expression, an effect mediated by STAT1 inhibition. At the protein level, B7-H1 molecules were stored in both degradative and unconventional secretory lysosomes. Surface membrane B7-H1 molecules were constitutively internalized and proteolyzed in lysosomes. The EBV latency III program increased the amounts of B7-H1-containing secretory lysosomes and their export to the surface membrane. By repressing actin polymerization, c-Myc blocked secretory lysosome migration and B7-H1 surface membrane export. In addition to B7-H1, various immunoregulatory molecules participating in the immunological synapse are stored in secretory lysosomes. By playing on actin polymerization, c-Myc could thus globally regulate the immunogenicity of transformed B cells, acting on export of secretory lysosomes to plasma membrane.

Type I interferons directly down-regulate BCL-6 in primary and transformed germinal center B cells: differential regulation in B cell lines derived from endemic or sporadic Burkitt's lymphoma

Type I interferons (IFN) exert multiple effects on both the innate and adaptive immune system in addition to their antiviral and antiproliferative activities. Little is known, however about the direct effects of type I IFNs on germinal center (GC) B cells, the central components of adaptive B cell responses. We used Burkitt's lymphoma (BL) lines, as a model system of normal human GC B cells, to examine the effect of type I IFNs on the expression of BCL-6, the major regulator of the GC reaction. We show that type I IFNs, but not IFNγ, IL-2 and TNFα rapidly down-regulate BCL-6 protein and mRNA expression, in cell lines derived from endemic, but not from sporadic BL. IFNα-induced down-regulation is specific for BCL-6, independent of Epstein-Barr virus and is not accompanied by IRF-4 up-regulation. IFNα-induced BCL-6 mRNA down-regulation does not require de novo protein synthesis and is specifically inhibited by piceatannol. The proteasome inhibitor MG132 non-specifically prevents, while inhibitors of alternate type I IFN signaling pathways do not inhibit IFNα-induced BCL-6 protein downregulation. We validate our results with showing that IFNα rapidly down-regulates BCL-6 mRNA in purified mouse normal GC B cells. Our results identify type I IFNs as the first group of cytokines that can down-regulate BCL-6 expression directly in GC B cells.

Cyclin D1 inhibits whereas c-Myc enhances the cytotoxicity of cisplatin in mouse pancreatic cancer cells via regulation of several members of the NF-κB and Bcl-2 families

Background:

Cisplatin (CDDP) is a drug used for treatment of many types of malignancy but pancreatic cancer is relatively resistant to it. This study aims to determine whether and how cyclin D1 (D1) and c-Myc influence the response of pancreatic cancer cells to CDDP.

Materials and Methods:

Ela-mycPT mouse pancreatic cancer cells were transfected with D1 or c-myc cDNA and treated with CDDP alone or together with NPCD, an inhibitor of cyclin dependent ckinase (CDK) 4 and 6. Reverse transcription followed by polymerase chain reaction (RT-PCR) and western blot assays were used to determine the mRNA and protein levels of interested genes. Cell viability was determined using 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay.

Results:

Treatment of Ela-mycPT1 cells with CDDP caused an increase in c-myc expression but a slightly latent decrease in D1 expression, whereas D1 and c-Myc proteins repressed each other. D1 or c-Myc rendered Ela-mycPT1 cells resistant or sensitive, respectively, to CDDP. D1 induced the expression of several members of the NF-κB family, including RelA, RelB, Nfκb1 and Nfκb2. D1 also induced BIRC5 and several pro-survival members of the Bcl-2 gene family, including Bcl-2 , Mcl-1 and Bad while it decreased the level of the pro-apoptotic Noxa. Inhibition of CDK4 or CDK6 kinase activity by NPCD did not affect these effects of D1. In contrast, c-Myc in Ela-mycPT1 and Ela-mycPT4 cells has the opposite effects to D1 on the expression of most of these apoptosis regulating genes.

Conclusion:

Our results suggest that induction of c-Myc and inhibition of D1 may be mechanisms for CDDP to elicit cytotoxicity. On the other hand, D1 induces whereas c-Myc represses the expression of key NF-κB family members to induce and repress, respectively, the expression of BIRC5 and several Bcl-2 family members, in turn inhibiting or enhancing the response to CDDP.