Kaposi's Sarcoma Associated Herpesvirus Infection Induces the Expression of Neuroendocrine Genes in Endothelial Cells.

Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with endothelial Kaposi's sarcoma (KS) in immunocompromised individuals. KS lesion cells exhibit many similarities with neuroendocrine cancers such as the highly vascular and red/purple colored tumor lesions, spindle shaped cells, insignificant role for classic oncogenes in tumor development, release of bioactive amines and indolent growth of the tumors. However, the mechanistic basis for the similarity of KS lesion endothelial cells with neuroendocrine tumors remain unknown. Next-generation sequencing and bioinformatics analysis in the present study demonstrate that endothelial cells latently infected with KSHV express several neuronal and neuroendocrine (NE) genes. De Novo infection of primary dermal endothelial cells with live and UV-inactivated KSHV demonstrated that viral gene expression is responsible for the five selected NE genes (ADM2, HRH1, NSE [ENO2], PGP9.5 and SSTR1) upregulation. Immunofluorescence and immunohistochemistry examination demonstrated a robust expression of NE genes histamine receptor H1 (HRH1) and neuron specific enolase (NSE/ENO2) in KSHV infected KS tissue samples and KS visceral tissue microarrays. Further analysis demonstrated that KSHV latent ORFK12 gene (Kaposin A) mediated decreased host REST/NRSF protein (RE1-silencing transcription factor/neuron-restrictive silencer factor), a neuronal genes transcription repressor protein, is responsible for the NE gene expression in the infected endothelial cells. NE gene expression observed in KSHV infected cells were recapitulated in uninfected endothelial cells by the exogenous expression of ORFK12 and by the treatment of cells with REST inhibitor X5050. When the neuroactive ligand-activating receptor HRH1 and inhibitory somatostatin receptor 1 (SSTR1) were knocked out (KO) by CRISPR, HRH1 KO significantly inhibited cell proliferation while SSTR1 KO induced cell proliferation, and thus suggesting that HRH1 and SSTR1 probably counteract each other in regulating KSHV infected endothelial cell proliferation. These results demonstrate that the similarity of KS lesion cells with neuroendocrine tumors are probably as a result of KSHV infection induced transformation of non-neuronal endothelial cells into cells with neuroendocrine features. These studies suggest a potential role of neuroendocrine pathway genes in the pathobiological characteristics of KSHV infected endothelial cells including potential escape mechanism from the host immune system by the expression of immunological privileged neuronal site NE genes, and NE genes could potentially serve as markers for KSHV infected KS lesion endothelial cells as well as novel therapeutic targets to control KS lesions.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) manipulates several cellular pathways for its survival advantage during its latency in the infected human host. Here we demonstrate that KSHV infection up regulates the expression of genes related to neuronal and neuroendocrine functions that are characteristic of neuroendocrine (NE) tumors, both in vitro and in KS patient's tissues, and the heterogeneity of neuroendocrine receptors having opposing roles in KSHV infected cell proliferation. Induction of NE genes by KSHV could be also providing a potential survival advantage as the expression of proteins of immunological privileged sites such as neurons on endothelial cells may be an avenue to escape the host immune surveillance functions. NE gene products identified here could serve as markers for KSHV infected cells and could potentially serve as therapeutic targets to combat KSHV associated KS.