Biology subjects

Messinger, J. E.

Publications and source records attributed to Messinger, J. E..

3 recordsLinked to original sources

bioRxiv2020

Monocarboxylate transporter antagonism reveals metabolic vulnerabilities of viral-driven lymphomas

Epstein-Barr Virus (EBV) is a ubiquitous herpesvirus that typically causes asymptomatic infection but can promote B lymphoid tumors in the immune-suppressed. In vitro, EBV infection of primary B cells stimulates glycolysis during immortalization into lymphoblastoid cell lines (LCLs). Lactate export during glycolysis is crucial for continued proliferation of many cancer cells-part of a phenomenon known as the "Warburg effect," and is mediated by the monocarboxylate transporters 1 and 4 (MCT1 and MCT4). However, the role of MCT1/4 has yet to be studied in EBV-associated malignancies which display Warburg-like metabolism in vitro. Here, we show that EBV infection of B lymphocytes directly promotes temporal induction of MCT1 and MCT4 through the viral proteins EBNA2 and LMP1 respectively, with MCT1 being induced early after infection and MCT4 late. Remarkably, singular MCT1 inhibition early, and dual MCT1/4 inhibition in LCLs using a novel MCT4-selective inhibitor led to growth arrest and lactate buildup. Metabolic profiling in LCLs revealed significatly reduced oxygen consumption rates (OCR) and NAD+/NADH ratios, contrary to prevous observations of increased OCR and unaltered NAD+/NADH ratios in MCT1/MCT4-inhibited cancer cells. Furthermore, U-13C6 glucose labeling of MCT1/4-inhibited LCLs also revealed increased labeling of glutathione in the presence of elevated ROS and depleted glutathione pools, as well as increased labeling of de novo pyrimidine biosynthetic intermediates, suggesting broad effects on LCL metabolism. These vulnerabilities sensitized LCLs as well as EBV+, and the related gammaherpesvirus KSHV+ lymphoma cell lines to killing by metformin and phenformin, pointing at a novel therapeutic approach for viral lymphomas.

cancer biology↗

bioRxiv2019

Identification of Host Biomarkers of EBV Latency IIb and Latency III

Deciphering the molecular pathogenesis of virally induced cancers is challenging due, in part, to the heterogeneity of both viral and host gene expression. Epstein-Barr Virus (EBV) is a ubiquitous herpesvirus prevalent in B-cell lymphomas of the immune suppressed. EBV infection of primary human B cells leads to their immortalization into lymphoblastoid cell lines (LCLs) serving as a model of these lymphomas. In previous studies, our lab has described a temporal model for immortalization with an initial phase characterized by expression of the Epstein-Barr Nuclear Antigens (EBNAs), high c-Myc activity, and hyper-proliferation in the absence of the Latent Membrane Proteins (LMPs), called latency IIb. This is followed by the long-term outgrowth of LCLs expressing the EBNAs along with the LMPs, particularly the NF{kappa}B-activating LMP1, defining latency III. LCLs, however, express a broad distribution of LMP1 such that a subset of these cells expresses LMP1 at levels seen in latency IIb, making it difficult to distinguish these two latency states. In this study, we performed mRNA-Seq on early EBV-infected latency IIb cells and latency III LCLs sorted by NF{kappa}B activity. We found that latency IIb transcriptomes clustered independently from latency III independent of NF{kappa}B. We identified and validated mRNAs defining these latency states. Indeed, we were able to distinguish latency IIb cells from LCLs expressing low levels of LMP1 using multiplex RNA-FISH targeting EBV EBNA2, LMP1, and human CCR7. This study defines latency IIb as a bona fide latency state independent from latency III and identifies biomarkers for understanding EBV-associated tumor heterogeneity.\n\nIMPORTANCEEBV is a ubiquitous pathogen with >95% of adults harboring a life-long latent infection in memory B cells. In immunocompromised individuals, latent EBV infection can result in lymphoma. The established expression profile of these lymphomas is latency III, which includes expression of all latency genes. However, single cell analysis of EBV latent gene expression in these lymphomas suggests heterogeneity where most cells express the transcription factor, EBNA2, and only a fraction express the membrane protein LMP1. Our work describes an early phase after infection where the EBNAs are expressed without LMP1, called latency IIb. However, LMP1 levels within latency III vary widely making these states hard to discriminate. This may have important implications for therapeutic responses. It is crucial to distinguish these states to understand the molecular pathogenesis of these lymphomas. Ultimately, better tools to understand the heterogeneity of these cancers will support more efficacious therapies in the future.

cancer biology↗

bioRxiv2017

c-Myc Represses Transcription of the Epstein-Barr Virus Latent Membrane Protein 1 Early After Primary B Cell Infection

Recent evidence has shown that the EBV oncogene LMP1 is not expressed at high levels early after EBV-infection of primary B cells, despite its being essential for the long-term outgrowth of immortalized lymphoblastoid cell lines (LCLs). In this study, we found that expression of LMP1 increased fifty-fold between seven days post infection and the LCL state. Metabolic labeling of nascently transcribed mRNA indicated this was primarily a transcription-mediated event. EBNA2, the key viral transcription factor regulating LMP1, and CTCF, an important chromatin insulator, were recruited to the LMP1 locus similarly early and late after infection. However, the activating histone H3K9Ac mark was enriched at the LMP1 promoter in LCLs relative to early-infected B cells. We found that high c-Myc activity in EBV-infected lymphoma cells as well as overexpression of c-Myc in an LCL model system repressed LMP1 transcription. Finally, we found that chemical inhibition of c-Myc expression both in LCLs and early after primary B-cell infection increased LMP1 expression. These data support a model in which high levels of endogenous c-Myc activity induced early after primary B-cell infection directly represses LMP1 transcription.\n\nIMPORTANCEEBV is a highly successful pathogen that latently infects greater than 90% of adults worldwide and is also causally associated with a number of B-cell malignancies. EBV expresses a set of viral oncoproteins and non-coding RNAs during the latent life cycle with the potential to promote cancer. Critical among these is the viral latent membrane protein, LMP1. Prior work suggests that LMP1 is essential for EBV to immortalize B cells, but our recent work indicates that LMP1 is not produced at high levels during the first few weeks after infection. Here, we show that the transcription of LMP1 can be negatively regulated by a host transcription factor, c-Myc. Ultimately, understanding the regulation of EBV-encoded oncogenes will allow us to better treat cancers that rely on these viral products for survival.

cancer biology↗