Activation of EHF via STAT3 phosphorylation by LMP2A in Epstein‐Barr virus–positive gastric cancer

Abstract

Epstein‐Barr virus (EBV) is associated with approximately 10% of gastric cancers (GCs). We previously showed that EBV infection of gastric epithelial cells induces aberrant DNA methylation in promoter regions, which causes silencing of critical tumor suppressor genes. Here, we analyzed gene expressions and active histone modifications (H3K4me3, H3K4me1, and H3K27ac) genome‐widely in EBV‐positive GC cell lines and in vitro EBV‐infected GC cell lines to elucidate the transcription factors contributing to tumorigenesis through enhancer activation. Genes associated with “signaling of WNT in cancer” were significantly enriched in EBV‐positive GC, showing increased active β‐catenin staining. Genes neighboring activated enhancers were significantly upregulated, and EHF motif was significantly enriched in these active enhancers. Higher expression of EHF in clinical EBV‐positive GC compared with normal tissue and EBV‐negative GC was confirmed by RNA‐seq using The Cancer Genome Atlas cohort, and by immunostaining using our cohort. EHF knockdown markedly inhibited cell proliferation. Moreover, there was significant enrichment of critical cancer pathway–related genes (eg, FZD5) in the downstream of EHF. EBV protein LMP2A caused upregulation of EHF via phosphorylation of STAT3. STAT3 knockdown was shown to inhibit cellular growth of EBV‐positive GC cells, and the inhibition was rescued by EHF overexpression. Our data highlighted the important role of EBV infection in gastric tumorigenesis via enhancer activation.

The roles of DNA methylation on the promotor of the Epstein–Barr virus (EBV) gene and the genome in patients with EBV-associated diseases

“…Sulfite genome sequencing and methylation-sensitive polymerase chain reaction confirmed that Cp shows extensive unmethylation in latency III infection and that all EBNAs are expressed by Cp. Cp is hypermethylated and silent in latency I and II infection (Li et al 2021;Salamon et al 2001). It has been shown that Wp and Cp are hypermethylated in B lymphocytes of healthy carriers (Robertson and Ambinder 1997) or defective (Niller et al 2016).…”

Establishment and characterization of a new intrahepatic cholangiocarcinoma cell line derived from a Chinese patient

“…After EHF knockout, proteins that promote the cell cycle (Cyclin B1, Cyclin D1, and PCNA) are downregulated, and proteins that negatively regulate cell cycle progression (P21) are upregulated [ 44 ]. LMP2A in EBV-positive gastric cancer activates EHF through STAT3 phosphorylation [ 45 ]. EHF, by activating TGF-b1 transcription and typical TGF-a signal transduction, promotes colorectal cancer progression [ 46 ].…”

Establishment and characterization of two Epstein–Barr virus‐positive gastric cancer cell lines with epitheliotropic M81 strain undergoing distinct viral and altered cellular expression profiles

“…However, compared with AGS-M81, no expression of LMP2A or BHLF1 could be detected in AGS-Akata. LMP2A and BHLF1 are two important viral oncogenes, 32,33 and lack of these two gene expressions in Akata-infected GC cell lines might discourage us for further relevant studies. HGC27-M81 expressed only 27 viral genes, including 4 latent (LMP1, EBNA1, EBNA3A, and EBNA3C), 13 early genes, and 10 late genes (Figure 7A,B; and Table S2).…”