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KSHV-induced iNOS in Kaposi’s Sarcoma tumors and mouse model

ABSTRACT: Kaposi’s Sarcoma (KS) is a heterogenous, multifocal vascular malignancy caused by the human herpesvirus 8 (HHV8), also known as Kaposi’s Sarcoma-Associated Herpesvirus (KSHV). Here, we show that KS lesions express iNOS/NOS2 broadly throughout KS lesions, with enrichment in LANA positive spindle cells. The iNOS byproduct 3-nitrotyrosine is also enriched in LANA positive tumor cells and colocalizes with a fraction of LANA-nuclear bodies. We show that iNOS is highly expressed in the L1T3 tumor model of KS. iNOS expression correlated with KSHV lytic cycle gene expression, which was elevated in late-stage tumors (>4 weeks) but to a lesser degree in early stage (1 week) xenografts. Further, we show that L1T3 tumor growth is sensitive to an inhibitor of nitric oxide, L-NMMA. These finding suggest that iNOS is expressed in KSHV infected endothelial-transformed tumor cells in KS, that iNOS expression depends on tumor microenvironment stress conditions, and that iNOS enzymatic activity contributes to KS tumor growth.

ORGANISM(S): Homo sapiens

PROVIDER: GSE222527 | GEO | 2023/07/14

REPOSITORIES: GEO

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Project description:Kaposi's sarcoma (KS), is an AIDS-associated neoplasm caused by the KS herpesvirus (KSHV/ HHV-8). KSHV-sarcomagenesis is the consequence of oncogenic viral gene expression as well as host genetic and epigenetic alterations. Although KSHV is invariably found in all KS lesions, the percentage of KSHV-infected (LANA+) spindle-cells of the lesion is variable, suggesting the existence of paracrine oncogenic mechanisms and/or spindle cells that have lost KSHV. A mouse model of KSHVBac36-driven tumorigenesis allowed us to induce KSHV-episome loss before and after tumor development. Although cells that lose the KSHV episome prior to tumor formation lose their tumorigenicity, explanted KSHV positive tumor cells that lost the KSHV episome remained tumorigenic. This pointed to the existence of virally-induced irreversible oncogenic alterations occurring during KSHV-tumor formation that support the possibility of hit and run viral sarcomagenesis. RNA sequencing and CpG-methylation analysis were performed on KSHV positive and negative cells, KSHV positive and KSHV negative tumors that developed following KSHV-episome loss from explanted tumor cells. When KSHV positive cells form KSHV-driven tumors, along with viral-gene upregulation there is a tendency for hypo-methylation in genes from oncogenic and differentiation pathways. In contrast, KSHV-negative tumors formed after KSHV-episome loss, show a tendency towards gene hyper-methylation when compared to KSHV-positive tumors. Regarding occurrence of host-mutations, we found the same set of innate-immunity related mutations undetected in KSHV-infected cells but present in all KSHV positive tumors, indicating that pre-existing host mutations that provide an in vivo growth advantage are clonally-selected and contribute to KSHV-tumorigenesis. In addition, KSHV negative tumors display de novo mutations related to cell proliferation that, together with the PDGFRAD842V, were responsible for driving tumorigenesis in absence of the KSHV-episomes. KSHV-induced irreversible genetic and epigenetic oncogenic alterations support the possibility of “hit and run” KSHV-sarcomagenesis consistent with the presence of LANA-negative spindle-cells in KS lesions.

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KSHV-induced iNOS in Kaposi’s Sarcoma tumors and mouse model

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