Nox-4–Dependent Nuclear H₂O₂ Drives DNA Oxidation Resulting in 8-OHdG as Urinary Biomarker and Hemangioendothelioma Formation

Abstract

Hemangioendotheliomas are classified as endothelial cell tumors, which are the most common soft tissue tumors in infants. In a murine model of hemangioendothelioma, we previously showed that MCP-1 is required for its development and that the expression of MCP-1 in EOMA cells is redox sensitive. Here, we sought to identify the source of oxidants that drive hemangioendothelioma formation. Seven known isoforms exist of the catalytic subunit gp91. Only the nox-4 isoform of gp91 was present in EOMA cells, in contrast with non-tumor-forming murine endothelial cells that contained multiple forms of nox. Nox-4 knockdown markedly attenuated MCP-1 expression and hemangioendothelioma formation. We report that in EOMA cells, nox-4 is localized such that it delivers H 2 O 2 to the nuclear compartment. Such delivery of H 2 O 2 causes oxidative modification of DNA, which can be detected in the urine of tumor-bearing mice as 8-hydroxy-2-deoxyguanosine. Iron chelation by in vivo administration of deferoxamine improved tumor outcomes. The current state of information connects nox-4 to MCP-1 to form a major axis of control that regulates the fate of hemangioendothelioma development in vivo. Antioxid. Redox Signal. 12, 933-943.

Multidrug Resistance-associated Protein-1 (MRP-1)-dependent Glutathione Disulfide (GSSG) Efflux as a Critical Survival Factor for Oxidant-enriched Tumorigenic Endothelial Cells

“…These tumors result in residual deformity in 50% of affected children, threaten normal development in 10%, and threaten the life of 1% of affected children (4). Previous work using a validated in vivo murine endothelial (EOMA) cell tumor model has established that expression of oxidant-inducible monocyte chemoattractant protein-1 (MCP-1) 3 is required for endothelial cell tumor formation and that Nox-4 is the primary source of oxidants inducing MCP-1 expression in EOMA cells (5)(6)(7). Elevated levels of Nox-4 and increased levels of oxidized nuclear DNA have been reported in human endothelial cell tumors (8).…”

“…A striking feature of the endothelial cell tumors is that Nox-4 is perinuclear and delivers H 2 O 2 directly into the nucleus (7). In EOMA, Nox-4 is constitutively active and present in levels severalfold higher compared with non-tumor-forming endothelial cells (7).…”

“…In EOMA, Nox-4 is constitutively active and present in levels severalfold higher compared with non-tumor-forming endothelial cells (7). Given that the nuclear redox microenvironment must be maintained in an appropriate reduced state in order to defend cell survival and growth (8), it is intuitively clear that EOMA cells must depend on a pivotal mechanism to successfully handle the threat of nuclear oxidative stress.…”

“…Thus, these cells must rely on rapid clearance of GSSG to ensure their survival in an oxidant-rich scenario (13). The objective of this work is to elucidate the mechanisms by which EOMA cells defend survival under conditions of high Nox-4-dependent oxidants, which are also necessary for tumor growth (7). We tested the hypothesis that EOMA cells rely on an extraordinary mechanism to efflux cellular GSSG, which acts as a critical survival factor.…”

Dicer Knockdown Inhibits Endothelial Cell Tumor Growth via MicroRNA 21a-3p Targeting of Nox-4

“…Using this approach, we have previously demonstrated that oxidant-inducible expression of monocyte chemoattractant protein-1 (MCP-1) and macrophage recruitment is required for HE growth (7). Our work has recognized that the primary source of reactive oxygen species in endothelial cells is NADPH oxidase (8). The predominant isoform of the gp91 catalytic subunit of NADPH oxidase present in tumor forming EOMA cells is Nox-4.…”