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Co-immunoprecipitation Assay Using Endogenous Nuclear Proteins from Cells Cultured Under Hypoxic Conditions
Published on: August 2, 2018
A novel pVHL-independent but NEMO-driven pathway in renal cancer promotes HIF stabilization
A M Nowicka1, I Häuselmann2, L Borsig2
1Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
Abstract:
Activation of hypoxia-inducible factor (HIF) is due to loss of von Hippel-Lindau protein (pVHL) function in most clear cell renal cell carcinomas (ccRCCs). Here we describe a novel pVHL-independent mechanism of HIF regulation and identify nuclear factor (NF)-κB essential modulator (NEMO) as a hitherto unknown oncogenic factor influencing human ccRCC progression. Over 60% of human ccRCCs (n=157) have negative or weak NEMO protein expression by immunohistochemistry. Moderate/strong NEMO protein expression is more frequent in VHL wild-type ccRCCs. We show that NEMO stabilizes HIFα via direct interaction and independently of NF-κB signaling in vitro. NEMO prolongs tumor cell survival via regulation of apoptosis and activation of epithelial-to-mesenchymal transition, facilitating tumor metastasis. Our findings suggest that NEMO-driven HIF activation is involved in progression of ccRCC. Therefore, NEMO may represent a clinically relevant link between NF-κB and the VHL/HIF pathways. Targeting NEMO with specific inhibitors in patients with metastatic ccRCC could be a novel treatment approach in patients with ccRCC expressing functional pVHL.
Insights
Nuclear factor (NF)-κB essential modulator (NEMO) drives clear cell renal cell carcinoma (ccRCC) progression independently of the von Hippel-Lindau (VHL) protein. NEMO stabilizes hypoxia-inducible factor alpha (HIFα), promoting tumor survival and metastasis, suggesting NEMO as a therapeutic target.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Clear cell renal cell carcinoma (ccRCC) pathogenesis often involves hypoxia-inducible factor (HIF) activation due to loss of von Hippel-Lindau protein (pVHL) function.
- A pVHL-independent mechanism of HIF regulation and its role in ccRCC progression remain incompletely understood.
Purpose of the Study:
- To identify novel factors regulating HIF in ccRCC.
- To investigate the role of nuclear factor (NF)-κB essential modulator (NEMO) in ccRCC progression and its relationship with the VHL/HIF pathway.
Main Methods:
- Immunohistochemistry on 157 human ccRCC samples to assess NEMO protein expression.
- In vitro studies to examine NEMO's interaction with HIFα and its effect on NF-κB signaling.
- Analysis of NEMO's impact on tumor cell survival, apoptosis, and epithelial-to-mesenchymal transition (EMT).
Main Results:
- Over 60% of ccRCCs exhibited negative or weak NEMO expression; moderate/strong expression was more common in VHL wild-type tumors.
- NEMO directly interacts with HIFα, stabilizing it independently of NF-κB signaling.
- NEMO promotes ccRCC progression by enhancing tumor cell survival, inhibiting apoptosis, and activating EMT, thereby facilitating metastasis.
Conclusions:
- NEMO is a novel oncogenic factor in ccRCC, driving HIF activation through a pVHL-independent mechanism.
- NEMO links the NF-κB and VHL/HIF pathways in ccRCC progression.
- Targeting NEMO could represent a new therapeutic strategy for metastatic ccRCC, particularly in patients with functional pVHL.
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