KSHV-induced notch components render endothelial and mural cell characteristics and cell survival

Abstract

Kaposi sarcoma–associated herpesvirus (KSHV) infection is essential to the development of Kaposi sarcoma (KS). Notch signaling is also known to play a pivotal role in KS cell survival and lytic phase entrance of KSHV. In the current study, we sought to determine whether KSHV regulates Notch components. KSHV-infected lymphatic endothelial cells showed induction of receptors Notch3 and Notch4, Notch ligands Dll4 and Jagged1, and activated Notch receptors in contrast to uninfected lymphatic endothelial cells. In addition, KSHV induced the expression of endothelial precursor cell marker (CD133) and mural cell markers (calponin, desmin, and smooth muscle alpha actin), suggesting dedifferentiation and trans-differentiation. Overexpression of latency proteins (LANA, vFLIP) and lytic phase proteins (RTA, vGPCR, viral interleukin-6) further supported the direct regulatory capacity of KSHV viral proteins to induce Notch receptors (Notch2, Notch3), ligands (Dll1, Dll4, Jagged1), downstream targets (Hey, Hes), and endothelial precursor CD133. Targeting Notch pathway with γ-secretase inhibitor and a decoy protein in the form of soluble Dll4 inhibited growth of KSHV-transformed endothelial cell line. Soluble Dll4 was also highly active in vivo against KS tumor xenograft. It inhibited tumor cell growth, induced tumor cell death, and reduced vessel perfusion. Soluble Dll4 is thus a candidate for clinical investigation.

Latency-Associated Nuclear Antigen of Kaposi Sarcoma–Associated Herpesvirus Promotes Angiogenesis through Targeting Notch Signaling Effector Hey1

“…Multiple KSHV-encoded viral proteins have been demonstrated to activate the Notch pathway (3,6,12,(16)(17)(18)(38)(39)(40). We reported previously that KSHV LANA stabilizes ICN and contributes to cell proliferation (30).…”

“…Importantly, inhibition of Notch signaling has been shown to inhibit tumor growth (16,17). Notch signaling is targeted by KSHV through vFLIP (latent) and vGPCR (lytic), thus contributing to cell proliferation (8,17,18).…”

“…Importantly, inhibition of Notch signaling has been shown to inhibit tumor growth (16,17). Notch signaling is targeted by KSHV through vFLIP (latent) and vGPCR (lytic), thus contributing to cell proliferation (8,17,18). Cheng and colleagues found that numerous downstream targets of the Notch signaling pathway, such as Hey and Hes, were upregulated in three-dimensional cultures of KSHV-infected cells (18).…”

Kaposi sarcoma–associated herpesvirus: immunobiology, oncogenesis, and therapy

“…PELs are also extremely sensitive to NF-κB pathway inhibitors such as bortezomib (186,187), and a clinical trial with adjuvant bortezomib is ongoing. Other targets with encouraging preclinical results are NOTCH (188)(189)(190)(191)(192), and the KSHV receptor, ephrin receptor A2 (EphA2) (193)(194)(195).…”

KSHV Paracrine Effects on Tumorigenesis

“…. Currently, two hypotheses describe the origin of the KS spindle cells: the first hypothesis suggests that KSHV infects both BECs and LECs, and induces a transcriptional dedifferentiation towards the gene expression profile of an endothelial precursor cell (EPC) (R. Liu et al, 2010). This hypothesis is supported by the studies of Chang et al, where a highthroughput approach was employed to study the genome-wide alternative splicing events in LECs and CD34 + EPCs (T.Y.…”