Epstein-Barr virus BARF1-induced NFκB/miR-146a/SMAD4 alterations in stomach cancer cells

Abstract

Epstein-Barr virus (EBV)-encoded BamHI-A rightward frame 1 (BARF1) is a putative viral oncogene in EBV-infected stomach cancer. The aim of the present study was to investigate BARF1-induced cellular protein and microRNA alterations. In this study, BARF1-expressing stomach cancer cells showed a high rate of proliferation, high levels of NFκB, and miR-146a upregulation, which was reversed by NFκB knockdown. During BARF1-induced NFκB upregulation, hCSF1 receptor level was unchanged. Knockdown of BARF1 in the naturally EBV-infected YCCEL1 stomach cancer cells suppressed cell proliferation, and downregulated NFκB and miR-146a. SMAD4 was identified as a miR-146a target and was downregulated in BARF1-expressing cells, whereas SMAD4 expression was restored by anti-miR-146a. Knockdown of BARF1 in YCCEL1 cells upregulated SMAD4, and this effect was reversed by miR-146a overexpression. Transfection of BARF1-expressing cells with pCEP4-SMAD4 abolished the cell proliferating effect of BARF1. In stomach cancer tissues, miR-146a was expressed at higher levels, and more frequent NFκB nuclear positivity immunohistochemically, but not of SMAD4 nuclear loss was found in the EBV-positive group compared with the EBV-negative group. In conclusion, EBV-encoded BARF1 promotes cell proliferation in stomach cancer by upregulating NFκB and miR-146a and downregulating SMAD4, thereby contributing to EBV-induced stomach cancer progression.

miR‐146a‐5p: Expression, regulation, and functions in cancer

“…Through targeting of SMAD4, miR-146a could promote cell proliferation and inhibit apoptosis. Similar upregulation of miR-146a and subsequent targeting of SMAD4 was demonstrated in Epstein-Barr virus (EBV)-infected gastric cells (Kim et al, 2016). However, miR-146a has been shown to induce apoptosis in gastric cancer cells by targeting TGFβ-activated kinase 1 (TAK1), a pro-survival gene that can activate NF-κB signaling ).…”

Viruses as key modulators of the TGF‐β pathway; a double‐edged sword involved in cancer

“…69 EBV-encoded BARF1 is another EBV factor by which FIGURE 4 A schematic illustration of the major HPV proteins and corresponding targets, by which HPV modulates the TGF-β signaling pathway the virus modulates the TGF-β pathway enhancing cell proliferation in gastric cancer; in an NFκB-dependent manner, BARF1 upmodulate miR-146a-5p levels that directly targets SMAD4 and reduces its levels in gastric cancer cells. 71 LMP-1 also induces miR-146a expression that may similarly suppress SMAD4 protein. 72 In summary, reports suggest these EBV proteins as promising target for therapeutic interventions, so that a BARF1-specific mAb was proposed as a novel immunotherapeutic tool toward the management of EBV-associated malignancies.…”

“…-reduced SMAD4 levels, mediated by NF-κB upregulation, which in turn enhances miR-146a-5p to target SMAD4 in gastric cancer. 71 KSHV LANA -downregulated TGFbRII by LANA-mediated histone methylation and deacetylation of TGFbRII promoter. 77 vFLIP -downregulated SMAD2 through the induction of oncogenic miR-17-92.…”

Dengue virus non structural protein 1 disrupts the TGF-β/Smad signaling by utilizing E3 ligase Smurf2

“…Dengue NS1 Protein Inhibits TGF-β signalling by reducing the Smad3 and Smad4 expression DENV replication derailed the TGF-β/Smad signaling pathway by impairing the expression of Smad proteins. Several viral proteins have been known for their interfering role in the TGF-β/Smad signaling pathway 10,11,17 . We used two DENV non-structural proteins, NS1 and NS5, as they have been reported to interact with different host proteins 18 to nd out whether NS1 or NS5 have any role in the TGF-β/Smad pathway.…”

“…Similar results had been observed with Human T-cell leukemia virus type 1 that blocked Smad3 and Smad4 binding with respective promoters to activate the transcription of associate genes 26 . Likewise, BARF1 protein of Epstein-Barr virus downregulated Smad4 to promote cell proliferation and virus induced stomach cancer progression 17 .…”