Lymphatic reprogramming of blood vascular endothelium by Kaposi sarcoma–associated herpesvirus

Abstract

Kaposi sarcoma is considered a neoplasm of lymphatic endothelium infected with Kaposi sarcoma-associated herpesvirus. It is characterized by the expression of lymphatic lineage-specific genes by Kaposi sarcoma tumor cells. Here we show that infection of differentiated blood vascular endothelial cells with Kaposi sarcoma-associated herpesvirus leads to their lymphatic reprogramming; induction of ∼70% of the main lymphatic lineage-specific genes, including PROX1, a master regulator of lymphatic development; and downregulation of blood vascular genes.Kaposi sarcoma is the most frequently occurring malignant tumor in individuals infected with the human immunodeficiency (HIV) virus and also occurs in HIV-negative immunosuppressed individuals. Kaposi sarcoma mainly affects the skin and forms lesions of various types, including early inflammatory and patch stage lesions, and tumors with a predominant population of spindle cells. Infection with Kaposi sarcoma-associated herpesvirus (KSHV, also known as human herpesvirus-8) is essential for the formation of Kaposi sarcoma tumors 1,2 . Both latent viral genes, such as latency-associated nuclear antigen (LANA), and lytic viral genes, such as viral G-protein-coupled receptor, have been implicated in KSHV-mediated tumorigenesis 3 . In Kaposi sarcoma lesions, cells infected with KSHV characteristically appear spindle-shaped and are associated with slit-like spaces that sometimes contain red blood cells. Kaposi sarcoma is considered to be a neoplasm of KSHV-infected lymphatic endothelium, due to the morphological characteristics of the tumor cells and the expression of several lymphatic lineage-specific proteins, including VEGFR-3 and podoplanin [4][5][6][7] .The homeobox gene PROX1 is a master gene that controls lymphatic vessel development and differentiation 8 , and ectopic expression of PROX1 in differentiated blood vascular endothelial cells leads to lymphatic endothelial reprogramming of these cells 9,10 . Because KSHV can infect blood vascular endothelium, such as human umbilical vein endothelial cells, in vitro, we wondered whether KSHV infection might result in lymphatic reprogramming of blood vascular endothelium, potentially involving upregulation of PROX1.We first characterized the lineage-specific gene expression of cultured human lymphatic endothelial cells (LECs) versus blood vascular endothelial cells (BECs) 11 by Affymetrix HU133A gene arrays. We found that LECs, but not BECs, expressed PROX1, XLKD1 (encoding the hyaluronan receptor LYVE-1) and a number of other lymphatic lineage-specific genes ( Table 1). We then infected human dermal microvascular endothelial cells (HDMECs) with KSHV and carried out two independent transcriptional profiling studies 7 d later. Efficient KSHV infection was confirmed by high levels of expression of LANA mRNA in infected HDMECs. We found that 3-7% of infected HDMECs were ORF59-positive and 1.5-3% were K8.1 positive, in agreement with previous results [12][13][14] . This indicates that <10% of the cells were undergoing lytic reac...

CEA-related cell adhesion molecule-1 is involved in angiogenic switch in prostate cancer

“…These data demonstrate an increased expression of CEACAM1 in tumor lymphatics prior to angiogenic activation (Kilic et al, in preparation). Recently, CEACAM1 was found to be upregulated in endothelial cells during the lymphatic reprogramming of blood vascular endothelium (Hong et al, 2004). However, additional in vitro and in vivo studies are needed to determine the possible role of CEACAM1 in lymphangiogenesis.…”

The ubiquitin-like modifier FAT10 in cancer development

“…Spinnenhirn and colleagues (Spinnenhirn et al, 2014) showed that the presence of FAT10 resulted in a prolonged life span of S. Typhimurium-infected mice, pointing to a protective role of FAT10. It is assumed that FAT10 plays additional roles in innate immunity since an up-regulation of FAT10 expression was described in HIV-infected renal tubular epithelial cells (RTECs) (Ross et al, 2006;Snyder et al, 2009) and during Kaposi sarcomaassociated herpesvirus infection (Hong et al, 2004). Moreover, the group of J.-Y.…”

The pleiotropic effects of Kaposi's sarcoma herpesvirus

“…Transcriptional profiling of cultured endothelial cells infected with KSHV in vitro has identified several cellular genes that are strongly upregulated by KSHV infection and which may contribute to the increased proliferation, the loss of contact inhibition, and the differentiation stage of KSHVinfected endothelial cells. Thus, the receptor tyrosine kinase c-kit is strongly up-regulated in KSHVinfected DMVECs [78,79]; its ligand, stem cell factor (SCF), enhances the growth of KSHV-infected DMVECs; and a small molecule inhibitor of c-kit, STI 571 ('Gleevec'), inhibits the morphological changes induced by KSHV in DMVECs [78]. Other cellular genes induced by KSHV include the orphan chemokine receptor RDC1 and neuritin, a protein previously linked to neurite outgrowth [80].…”

“…Suppression of RDC1 and neuritin gene expression by antisense oligonucleotides or siRNA reversed the morphological changes and increased proliferation induced by KSHV in DMVECs and also the growth in soft agar and tumourigenicity in the nude mouse model of 3T3 mouse fibroblasts stably transfected with either RDC1 or neuritin [80]. Haem oxygenase 1 (HO-1) is among several other cellular genes induced in cultured endothelial cells by latent KSHV infection [78][79][80][81][82][83] and is also expressed in KSHV-infected spindle cells in KS lesions [83]. The HO-1 inhibitor chromium mesoporphyrin IX inhibits haem-induced proliferation of KSHV-infected, but not uninfected, DMVECs, suggesting a role for HO-1 in the proliferation of KSHV-infected spindle cells [83].…”

“…A comparison of the transcriptional profile of blood vascular endothelial cells with lymphatic endothelial cells before and after infection with KSHV and of KS biopsies [79,82] has revealed that latent KSHV infection causes a reprogramming of blood vascular endothelial cells to differentiate in the direction of lymphatic endothelial cells [79,82]. The homeobox transcription factor Prox1, a master regulator of lymphatic development, is induced by KSHV and may play a central role in this process [79].…”