NADPH oxidase 5 (NOX5) - induced reactive oxygen signaling modulates normoxic HIF-1a and p27(Kip1) expression in malignant melanoma and other human tumors

NADPH oxidase 5 (NOX5) generated reactive oxygen species (ROS) have been implicated in signaling cascades that regulate cancer cell proliferation. To evaluate and validate NOX5 expression in human tumors, we screened a broad range of tissue microarrays (TMAs), and report substantial overexpression of NOX5 in malignant melanoma and cancers of the prostate, breast, and ovary. In human UACC-257 melanoma cells that possesses high levels of functional endogenous NOX5, overexpression of NOX5 resulted in enhanced cell growth, increased numbers of BrdU positive cells, and increased ?-H2AX levels. Additionally, NOX5-overexpressing (stable and inducible) UACC-257 cells demonstrated increased normoxic HIF-1a expression and decreased p27(Kip1) expression. Similarly, increased normoxic HIF-1a expression and decreased p27(Kip1) expression were observed in stable NOX5-overexpressing clones of KARPAS 299 human lymphoma cells and in the human prostate cancer cell line, PC-3. Conversely, knockdown of endogenous NOX5 in UACC-257 cells resulted in decreased cell growth, decreased HIF-1a expression, and increased p27(Kip1) expression. Likewise, in an additional human melanoma cell line, WM852, and in PC-3 cells, transient knockdown of endogenous NOX5 resulted in increased p27(Kip1) and decreased HIF-1a expression. Knockdown of endogenous NOX5 in UACC-257 cells resulted in decreased Akt and GSK3ß phosphorylation, signaling pathways known to modulate p27(Kip1) levels. In summary, our findings suggest that NOX5 expression in human UACC-257 melanoma cells could contribute to cell proliferation due, in part, to the generation of high local concentrations of extracellular ROS that modulate multiple pathways that regulate HIF-1 and networks that signal through Akt/GSK3ß/p27(Kip1) . This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

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