Upregulation of Cell Surface Glycoproteins in Correlation with KSHV LANA in the Kaposi Sarcoma Tumor Microenvironment

SIMPLE SUMMARY: Despite the widespread use of ART and decreased HIV incidence, Kaposi Sarcoma (KS), predominantly recognized as an AIDS-associated malignancy, continues to be highly prevalent in sub-Saharan Africa, parts of the Mediterranean, and parts of South America. Currently, there are no preventative measures or curative therapies for KS. The treatment is primarily pleiotropic chemotherapy, but the outcomes are inconsistent. Using our previously published transcriptomic profiles from KS lesions, we have identified potential biomarkers, therapeutic targets, and cell lineage determinants that are upregulated in expression and associated with KSHV infection. The protein expression of four surface-associated glycoproteins, FLT4, KDR, UNC5A, and ADAM12, was validated in human KS lesions and KSHV-infected cell line-derived mouse xenografts. The co-localization of CD34 and Prox-1, which are distinct endothelial lineage markers, suggests that cells within KS lesions are of a mesenchymal or progenitor phenotype rather than of a singular endothelial lineage. ABSTRACT: HIV-associated epidemic Kaposi sarcoma (EpKS) remains one of the most prevalent cancers in sub-Saharan Africa despite the widespread uptake of anti-retroviral therapy and HIV-1 suppression. In an effort to define potential therapeutic targets against KS tumors, we analyzed previously published KS bulk tumor transcriptomics to identify cell surface biomarkers. In addition to upregulated gene expression (>6-fold) in the EpKS tumor microenvironment, biomarkers were selected for correlation with KSHV latency-associated nuclear antigen (LANA) expression. The cell surface glycoprotein genes identified were KDR, FLT4, ADAM12, UNC5A, ZP2, and OX40, as well as the endothelial lineage determinants Prox-1 and CD34. Each protein was evaluated for its expression and co-localization with KSHV LANA using multi-color immunofluorescence in KS tissues, KSHV-infected L1T2 cells, uninfected TIVE cells, and murine L1T2 tumor xenografts. Five surface glycoproteins (KDR, FLT4, UNC5A, ADAM12, and CD34) were associated with LANA-positive cells but were also detected in uninfected cells in the KS microenvironment. In vitro L1T2 cultures showed evidence of only FLT4, KDR, and UNC5A, whereas mouse L1T2 xenografts recapitulated human KS cell surface expression profiles, with the exception of CD34 and Prox-1. In KS tumors, most LANA-positive cells co-expressed markers of vascular as well as lymphatic endothelial lineages, suggesting KS-associated dedifferentiation to a more mesenchymal/progenitor phenotype.