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KSHV Infection Mimics the Hypoxic Response Based on Next-Generation Sequencing [mRNA-Seq]

ABSTRACT: Purpose: Kaposi’s sarcoma associated-herpesvirus (KSHV) causes several hyperproliferative disorders, including Kaposi’s sarcoma, primary effusion lymphoma and multicentric Castleman’s disease. KSHV encodes for a number of microRNAs (miRNAs), and KSHV infection can affect the expression of cellular miRNAs. Hypoxia has been shown to induce KSHV reactivation, directly induce several KSHV lytic genes, and also induce the most abundant latent viral protein, LANA. Also, several KSHV proteins can stabilize and increase the cellular levels of hypoxia-inducible factor (HIF-1α). However, the degree to which hypoxic pathways are utilized by KSHV has yet to be determined. Methods: We investigated the interplay between hypoxia and KSHV infection by comparing the 31effects of hypoxia and KSHV infection on miRNA and mRNA expression, and by examining the 32effects of hypoxia on uninfected and KSHV-infected cells. This was accomplished using next-33generation sequencing (NGS), qRT-PCR, Taqman assays, and pathway analysis. Results: NGS analysis of human mRNAs revealed striking similarities (~34%) between the transcriptomic response to hypoxia and the transcriptomic response to KSHV infection. Additionally, hsa-miR-210, a key hypoxia-inducible miRNA with pro-angiogenic and anti-apoptotic properties, was found significantly up-regulated by both KSHV infection and hypoxia using Taqman assays. Finally, KSHV infected cells differed somewhat in their response to hypoxia compared to KSHV-uninfected controls. Conclusions: These results demonstrate that KSHV harnesses a part of the hypoxic cellular response and induces miR-210 up-regulation. The understanding of how these miRNAs, genes and pathways are regulated by HIF-1α and KSHV infection are essential to a better understanding of the biology of KSHV-associated diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE79029 | GEO | 2016/12/21

SECONDARY ACCESSION(S): PRJNA314765

REPOSITORIES: GEO

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Project description:The hallmark of Kaposi’s sarcoma (KS), the most common cancer in HIV-infected patients caused by Kaposi’s sarcoma-associated herpesvirus (KSHV) infection, is hyperinflammation. However, the role of inflammation and the mechanism of induction of inflammation in KSHV-induced cancer remain unclear. In a previous high-throughput screening against KSHV-induced oncogenesis, over half of the identified candidates were anti-inflammatory agents. Among them, dexamethasone, a common anti-inflammatory corticosteroid, functions through binding to and activating glucocorticoid receptor (GR). In this study, we examined the mechanism mediating KSHV-induced inflammation. We found that numerous inflammatory pathways were activated in KSHV-transformed cells. Particularly, the interleukin-1 alpha (IL-1α) and IL-1 receptor antagonist (IL-1Ra) from the IL-1 family, implicated in a wide variety of inflammatory diseases, were the most induced and suppressed cytokines in KSHV-transformed KMM cells compared to the matched primary MM cells, respectively. By using reverse genetics, we showed that KSHV-encoded miRNAs mediated IL-1α induction while both miRNAs and vFLIP mediated IL-1Ra suppression. Furthermore, the GR signaling was inhibited in KSHV-transformed cells, which was mediated by vFLIP and vCyclin. Importantly, dexamethasone treatment inhibited cell proliferation, and colony formation in softagar of KMM cells but had a minimal effect on MM cells. Consequently, dexamethasone suppressed the initiation and growth of KS-like KMM tumors in mice. Mechanistically, dexamethasone suppressed IL-1α expression but induced IL-1Ra expression. Treatment with recombinant IL-1α protein was sufficient to rescue the inhibitory effect of dexamethasone while overexpression of IL-1Ra alone caused a weak growth inhibition of KMM cells. Furthermore, dexamethasone induced IκBα expression resulting in the inhibition of the classical and alternative NF-kB pathways and IL-1α expression. Taken together, these results revealed the important role of IL-1 signaling pathway in KSHV-induced inflammation and oncogenesis, which can be inhibited by dexamethasone-activated GR signaling. This study determined the mechanism of inflammation in KSHV-induced oncogenesis and identified IL-1-mediated inflammation as a potential therapeutic target for KSHV-induced malignancies.

Project description:The resistance of hypoxic cells to radiotherapy and chemotherapy is a major problem in the treatment of cancer. Recently, an additional level of Hypoxia Inducible Factor (HIF) dependent transcriptional regulation has emerged involving modulation of a specific set of miRNAs including miR-210. We have recently shown that HIF-1 induction of miR-210 also stabilizes HIF-1 through a positive regulatory loop. We therefore hypothesized that by stabilizing HIF-1 in normoxia, miR-210 may protect cancer cells from radiation. We developed Non-Small Cell Lung Cancer (NSCLC)-derived cell lines (A549 and H1975) stably expressing miR-210 (pmiR-210) or a control miRNA (pmiR-Ctl). MiR-210 expressing cells showed a significant stabilization of HIF-1 associated with mitochondrial defects and a glycolytic phenotype. The cells were subjected to radiation levels ranging from 0 to 10Gy in normoxia and hypoxia. Cells expressing miR-210 in normoxia had the same level of resistance than control cells in hypoxia. pmiR-210 cells under hypoxia showed a low mortality rate due to a decrease in apoptosis and an ability to grow even at 10Gy. We have established that radioresistance was independent of p53 and cell cycle status. In addition, we show here that genomic double strand breaks (DSB) foci disappeared faster in pmiR-210 than in pmiR-Ctl cells, suggesting that miR-210 expression promotes a more efficient DSB repair. Finally, HIF-1 invalidation in pmiR-210 cells (pmiR-210/HIF-1-) abolished radioresistance of cells showing that this mechanism was dependent upon HIF-1. In conclusion, miR-210 appears to be a major component in the radioresistance of hypoxic cancer cells. Given the high stability of most miRNAs, this advantage could even be used by tumor cells in conditions where hypoxia may not be present anymore and strongly suggests that strategies targeting miR-210 would enhance tumor radiosensitization. To identify the set of transcripts targeted by miR-210, we overexpressed has-miR-210 or a control miRNA (ce-miR-67) in human lung adenocarcinoma A549 cells by transduction using lentivirus. The resulting pmiR-67 and pmiR-210 that stably overexpress miR-210 were selected by puromycin. RNA samples were harvested at 2 different times following cell plating (24 hours or 48 hours). Experiments were performed in dye-swap.

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KSHV Infection Mimics the Hypoxic Response Based on Next-Generation Sequencing [mRNA-Seq]

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