The Epstein-Barr virus (EBV) latency C promoter drives expression of a family of viral proteins commonly targeted by CD8 cytotoxic T cells. These proteins are not generally expressed in African Burkitt's lymphoma and in EBV-associated Hodgkin's disease. The failure to express these proteins is almost certainly an important factor in the evasion of immunosurveillance by EBV-associated tumors. In a previous study, we have shown that transcriptional activation of the C promoter is inhibited by methylation of a particular CpG site upstream of the promoter that prevents binding of a cellular protein (CBF2), and we have shown that this and adjacent CpG sites are methylated in a Burkitt's lymphoma cell line. In the present study, we show that CpG sites in the CBF2 binding region are predominantly methylated in African Burkitt's lymphoma and in EBV-associated Hodgkin's disease. In addition, we present the first direct evidence that the C promoter is transcriptionally silent in Burkitt's lymphoma. In contrast, we show a complete absence of methylation in the CBF2 binding region in a case of reversible EBV-associated B-cell lymphoma arising in an immunocompromised patient whose tumor shows C promoter transcriptional activity. By inhibiting expression of highly antigenic viral proteins, methylation of transcriptional control sequences may veil the presence of virus in tumor tissue from CD8(+) cytotoxic T-cell immune surveillance and thus facilitate viral tumorigenesis.
word count:ABSTRACT Chronic myelomonocytic leukemia (CMML) is an aggressive hematological malignancy with limited treatment options. Whole exome (WES) and targeted sequencing of several independent cohorts of CMML patients, comparing dysplastic (dCMML) to proliferative (pCMML) CMML, as well as paired chronic phase disease and acute leukemic transformation (LT), associate acquisition of oncogenic RAS pathway mutations, the most common being NRAS G12D , with aggressive disease and with disease progression. Using patient derived progenitor colony assays and a NRAS G12D -Vav-Cre mouse model, we further demonstrate the role of mutant RAS signaling in driving and maintaining pCMML phenotype. RNA-sequencing links RAS pathway mutations with an increased expression of genes encoding the mitotic checkpoint kinases PLK1 and WEE1. Further, we dmeoinstrated that non-mutated lysine methyltransferase KMT2A (MLL1) acts as mediator of NRAS-induced PLK1 and WEE1 expression. Finally, we demonstrate the translational value of our findings by showing that pharmacological PLK1 inhibition decreases monocytosis and hepatosplenomegaly while improving hematopoiesis in RAS mutant patient-derived xenografts. Hence, we define severe CMML as oncogenic RAS pathway-enriched malignancies, with a unique gene expression profile regulated by KMT2A, amenable to therapeutic intervention. RESULTS RAS pathway mutations correlate with WHO-defined proliferative CMML (pCMML)Analysis was first focused on chronic phase CMML, especially with regards to the phenotypic and survival differences between WHO-defined dCMML and pCMML subtypes. Univariate P.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.