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Updated: Dec 11, 2025
Co-immunoprecipitation Assay Using Endogenous Nuclear Proteins from Cells Cultured Under Hypoxic Conditions
Published on: August 2, 2018
Caveolin-1-Mediated Tumor Suppression Is Linked to Reduced HIF1α S-Nitrosylation and Transcriptional Activity in
Carlos Sanhueza1,2, Jimena Castillo Bennett1,3, Manuel Valenzuela-Valderrama3,4
1Cellular Communication Laboratory, Center for studies on Exercise, Metabolism and Cancer (CEMC), Program of Cell and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago 8380453, Chile.
Abstract:
Caveolin-1 (CAV1) is a well-established nitric oxide synthase inhibitor, whose function as a tumor suppressor is favored by, but not entirely dependent on, the presence of E-cadherin. Tumors are frequently hypoxic and the activation of the hypoxia-inducible factor-1α (HIF1α) promotes tumor growth. HIF1α is regulated by several post-translational modifications, including S-nitrosylation. Here, we evaluate the mechanisms underlying tumor suppression by CAV1 in cancer cells lacking E-cadherin in hypoxia. Our main findings are that CAV1 reduced HIF activity and Vascular Endothelial Growth Factor expression in vitro and in vivo. This effect was neither due to reduced HIF1α protein stability or reduced nuclear translocation. Instead, HIF1α S-nitrosylation observed in hypoxia was diminished by the presence of CAV1, and nitric oxide synthase (NOS) inhibition by Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) reduced HIF1α transcriptional activity in cells to the same extent as observed upon CAV1 expression. Additionally, arginase inhibition by (S)-(2-Boronoethyl)-L-cysteine (BEC) partially rescued cells from the CAV1-mediated suppression of HIF1α transcriptional activity. In vivo, CAV1-mediated tumor suppression was dependent on NOS activity. In summary, CAV1-dependent tumor suppression in the absence of E-cadherin is linked to reduced HIF1α transcriptional activity via diminished NOS-mediated HIF1α S-nitrosylation.
Insights
Caveolin-1 (CAV1) suppresses tumors by reducing hypoxia-inducible factor-1α (HIF1α) activity. This occurs through decreased nitric oxide synthase (NOS)-mediated S-nitrosylation of HIF1α, independent of E-cadherin.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Caveolin-1 (CAV1) is a tumor suppressor, often linked to E-cadherin, and inhibits nitric oxide synthase (NOS).
- Tumor hypoxia activates hypoxia-inducible factor-1α (HIF1α), promoting tumor growth.
- HIF1α activity is regulated by post-translational modifications, including S-nitrosylation.
Purpose of the Study:
- To investigate CAV1's tumor suppressive mechanisms in E-cadherin-deficient cancer cells under hypoxic conditions.
- To elucidate the role of HIF1α S-nitrosylation in CAV1-mediated tumor suppression.
Main Methods:
- In vitro and in vivo experiments evaluating HIF activity and Vascular Endothelial Growth Factor (VEGF) expression.
- Assessing HIF1α protein stability, nuclear translocation, and S-nitrosylation.
- Utilizing NOS inhibition (L-NAME) and arginase inhibition (BEC) to study molecular pathways.
Main Results:
- CAV1 expression reduced HIF activity and VEGF levels in vitro and in vivo.
- CAV1 diminished HIF1α S-nitrosylation, not protein stability or nuclear translocation.
- NOS inhibition mimicked CAV1's effect on HIF1α activity, while arginase inhibition partially reversed it.
- Tumor suppression by CAV1 in vivo was dependent on NOS activity.
Conclusions:
- CAV1-dependent tumor suppression in E-cadherin-negative cancers involves reduced HIF1α transcriptional activity.
- This suppression is mediated by decreased NOS-dependent HIF1α S-nitrosylation.
- CAV1's role as a tumor suppressor is linked to modulation of HIF1α nitrosylation under hypoxia.
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