ATR activated by EB virus facilitates chemotherapy resistance to cisplatin or 5-fluorouracil in human nasopharyngeal carcinoma

Epstein-Barr virus deubiquitinating enzyme BPLF1 is involved in EBV carcinogenesis by affecting cellular genomic stability

Increased mutational burden and EBV load have been revealed from normal tissues to Epstein-Barr virus (EBV)-associated gastric carcinomas (EBVaGCs). BPLF1, encoded by EBV, is a lytic cycle protein with deubiquitinating activity has been found to participate in disrupting repair of DNA damage. We first confirmed that BPLF1 gene in gastric cancer (GC) significantly increased the DNA double strand breaks (DSBs). Ubiquitination mass spectrometry identified histones as BPLF1 interactors and potential substrates, and co-immunoprecipitation and in vitro experiments verified that BPLF1 regulates H2Bub by targeting Rad6. Over-expressing Rad6 restored H2Bub but partially reduced γ-H2AX, suggesting that other downstream DNA repair processes were affected. mRNA expression of BRCA2 were significantly down-regulated by next-generation sequencing after over-expression of BPLF1, and over-expression of p65 facilitated the repair of DSBs. We demonstrated BPLF1 may lead to the accumulation of DSBs by two pathways, reducing H2B ubiquitination (H2Bub) and blocking homologous recombination which may provide new ideas for the treatment of gastric cancer.

Activation of MEK1/2/Nrf-2 Signaling Pathway by Epstein-Barr Virus-Latent Membrane Protein 1 Enhances Autophagy and Cisplatin Resistance in T-Cell Lymphoma

Epstein-Barr virus-latent membrane protein 1 (EBV-LMP1) was associated with lymphoma, but its specific mechanism is still controversial. The study is aimed at studying the regulation of lymphoma resistance by EBV-LMP1 through the MEK1/2/Nrf-2 signaling pathway. First, LMP1 was knocked down in EBV-positive SNK-6 cells and overexpressed in EBV-negative KHYG-1 cells. First, we found that overexpression of LMP1 significantly promoted the resistance of KHYG-1 cells to cisplatin (DDP), which was related to increased autophagy in the cells. In contrast, knockdown of LMP1 expression in SNK-6 cells promoted cellular sensitivity to DDP and reduced the autophagy of cells after DDP treatment. Moreover, specific inhibition of autophagy in KHYG-1 cells significantly attenuated the resistance to DDP caused by overexpression of LMP1, but treatment with rapamycin in SNK-6 cells significantly promoted the autophagy in the cells. Subsequently, overexpression of LMP1 promoted the activation of the MEK1/2-Nrf2 pathway in KYHG-1 cells, whereas knockdown of LMP1 in SNK-6 cells inhibited the activation of the MEK1/2-Nrf2 pathway. Inhibition of MEK1/2/Nrf-2 blocked the promoting effects of LMP1 on lymphoma cell resistance. In conclusion, EBV-LMP1 promotes cell autophagy after DDP treatment by activating the MEK1/2/Nrf-2 signaling pathway in lymphoma cells, thus, enhancing the resistance of lymphoma cells to DDP.

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

Small molecule 2,3-DCPE induces S phase arrest by activating the ATM/ATR-Chk1-Cdc25A signaling pathway in DLD-1 colon cancer cells

In our previous study, it was reported that 2[[3-(2,3-dichlorophenoxy)propyl]amino]ethanol (2,3-DCPE) induces apoptosis and cell cycle arrest. The current study aimed to investigate the molecular mechanism involved in 2,3-DCPE-induced S phase arrest. The results demonstrated that 2,3-DCPE upregulated phosphorylated (p-)H2A histone family member X, a biomarker of DNA damage, in the DLD-1 colon cancer cell line. Western blotting revealed that 2,3-DCPE increased the checkpoint kinase (Chk)1 (Ser317 and Ser345) level and decreased the expression of M-phase inducer phosphatase 1 (Cdc25A) in a time-dependent manner. Subsequently, the results demonstrated that the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia and Rad3-related (ATR) inhibitors wortmannin and caffeine had no effect on the cell cycle; however, the inhibitors partially abrogated 2,3-DCPE-induced S phase arrest. Flow cytometry assays revealed that caffeine (2 mM) reduced the proportion of S phase cells from 83 to 39.6% and that wortmannin (500 nM) reduced the proportion of S phase cells from 83 to 48.2%. Furthermore, wortmannin and caffeine inhibited the 2,3-DCPE-mediated phosphorylation of Chk1 and the degradation of Cdc25A. However, these ATM/ATR inhibitors had limited effect on 2,3-DCPE-induced apoptosis. Taken together, the data of the current study indicated that 2,3-DCPE caused DNA damage in colon cancer cells and that 2,3-DCPE-induced S phase arrest was associated with the activation of the ATM/ATR-Chk1-Cdc25A pathway.

EB virus-induced ATR activation accelerates nasopharyngeal carcinoma growth via M2-type macrophages polarization

Chronic inflammation induced by persistent viruses infection plays an essential role in tumor progression, which influenced on the interaction between the tumor cells and the tumor microenvironment. Our earlier study showed that ATR, a key kinase participant in single-stranded DNA damage response (DDR), was obviously activated by Epstein-Barr virus (EBV) in nasopharyngeal carcinoma (NPC). However, how EBV-induced ATR activation promotes NPC by influencing inflammatory microenvironment, such as tumor-associated macrophages (TAMs), remains elusive. In this study, we showed that EBV could promote the expression of p-ATR and M2-type TAMs transformation in clinical NPC specimens. The expression of p-ATR and M2-type TAMs were closely correlated each other and involved in TNM stage, lymph node metastasis and poor prognosis of the patients. In addition, the expression levels of CD68⁺CD206⁺, Arg1, VEGF, and CCL22 were increased in EB⁺ CNE1 cells, and decreased when ATR was inhibited. In the nude mice, EBV-induced ATR activation promoted subcutaneous transplanted tumor growth, higher expression of Ki67 and lung metastasis via M2-type TAMs recruitment. Experimental data also showed that the polarization of M2, the declined tumor necrosis factor-α (TNF-α) and increased transforming growth factor-β (TGF-β) were associated with ATR. Meanwhile, ATR activation could promote PPAR-δ and inhibited c-Jun and p-JNK expression, then downregulate JNK pathway. Collectively, our current study demonstrated the EBV infection could activate the ATR pathway to accelerate the transition of TAMs to M2, suggesting ATR knockdown could be a potential effective treatment strategy for EBV-positive NPC.

Lgr5 maintains stemness and regulates cell property in nasopharyngeal carcinoma through Wnt/β-catenin signaling pathway

Nasopharyngeal carcinoma (NPC) is a common malignant tumor in Southern China and Southeast Asia. In this study, we found that Leucine rich repeat containing G protein-coupled receptor 5 (Lgr5) was highly expressed in NPC tissues and marked NPC stem cells. Lgr5high tumors showed differential transcriptional landscape compared to Lgr5not high tumors. Lgr5 expression was associated with the clinicopathologic features in NPC and was able to regulate the stemness and viability of NPC cell line CNE1 and HNE1. Meanwhile, the migration, invasion and epithelial-mesenchymal transition (EMT) was modulated by Lgr5 via Wnt/β-catenin signaling pathway. Furthermore, Lgr5 could regulate the sensitivity of NPC cells to chemotherapy drugs. Xenografted tumors from Lgr5-overexpressed CNE1 cells showed stronger tumor forming capacity and higher expression level of stem cell markers. Thus, we characterized previously unidentified role of Lgr5 in NPC cells, potential serving as a NPC stem cell biomarker and a therapeutic target against NPC.

Differential Expression and Alternative Splicing of Transcripts Associated With Cisplatin-Induced Chemoresistance in Nasopharyngeal Carcinoma

Radiotherapy and adjuvant cisplatin (DDP) chemotherapy are standard administrations applied to treat nasopharyngeal carcinoma (NPC). However, the molecular changes and functions of DDP in NPC chemo-resistance remain poorly understood. In the present study, transcriptomic sequencing between 5-8F and 5-8F/DDP cells was performed to identify differential expression and alternative splicing (AS) characteristics in DDP-resistant NPC cells. Transcriptomic profiling identified 1,757 upregulated genes and 1,473 downregulated differentially expressed genes (DEGs). Bioinformatic analysis revealed that these DEGs were associated with or participated in important biological regulatory functions in NPC. Validation of 20 significant DEGs using quantitative real-time reverse transcription PCR showed that the expression patterns of 17 mRNAs were in accordance with the sequencing data. Intron retention was identified as the major AS event in chemoresistant cells. Furthermore, the expression level of matrix metalloproteinase 1 (MMP1), which was one of the most upregulated mRNAs in the chemoresistant cell lines, was significantly associated with the migration, invasion, and proliferation of NPC cells in vitro. Our study revealed that dysregulated genes and AS-mediated DDP chemoresistance might play important roles in NPC development and progression. Targeting aberrantly expressed genes might clarify the pathogenesis of NPC and contribute to developing new therapeutic strategies for NPC.

VE-822 mediated inhibition of ATR signaling sensitizes chondrosarcoma to cisplatin via reversion of the DNA damage response

Introduction

Cisplatin has been reported to elicit the DNA damage response (DDR) via activation of the ATR-Chk1 pathway, which in turn contributes to the induction of cisplatin resistance. Inhibition of ATR-Chk1 signaling reverses cisplatin resistance in some cancers. However, the influence of inhibiting ATR-Chk1 signaling on cisplatin resistance in chondrosarcoma cancer has not been reported.

Materials and methods

We compared the expression levels of ATR kinases in human nasopharyngeal carcinoma, choriocarcinoma and chondrosarcoma cell lines. We inhibited ATR kinase function with VE-822, a selective ATR inhibitor, and suppressed ATR kinase expression with shRNA. Western blotting, the CCK-8 assay, cell cycle distribution assay and apoptosis analysis were used to study the influence of inhibiting ATR-Chk1 signaling on reversing cisplatin resistance in chondrosarcoma cell lines.

Results

We found that chondrosarcoma cells expressed very low basal levels of phosphorylated ATR, but cisplatin treatment induced the activation of ATR-Chk1 signaling in a dose- and time-dependent manner, suggesting the induction of DDR. As expected, ATR inhibition with VE-822 reversed cisplatin-induced DDR and enhanced cisplatin-induced activation of H2AX, which is an important marker of DNA damage. Meanwhile, ATR inhibition by RNA interference also reversed DDR and promoted DNA damage. Furthermore, both pharmacological and molecular inhibition of ATR accelerated cisplatin-induced inhibition of cell proliferation and cell death.

Conclusion

Our results suggested that inhibiting ATR activation promoted cisplatin-induced cell death via reversion of DDR, and VE-822 may be a valuable strategy for the prevention of cisplatin resistance in chondrosarcoma.