Hypoxia-inducible factors mediate coordinated RhoA-ROCK1 expression and signaling in breast cancer cells
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Updated: May 5, 2026
Co-immunoprecipitation Assay Using Endogenous Nuclear Proteins from Cells Cultured Under Hypoxic Conditions
Published on: August 2, 2018
Daniele M Gilkes1, Lisha Xiang, Sun Joo Lee
1Vascular Program, Institute for Cell Engineering, McKusick-Nathans Institute of Genetic Medicine, and Departments of Pediatrics, Oncology, Medicine, Radiation Oncology, and Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Abstract:
Overexpression of Rho kinase 1 (ROCK1) and the G protein RhoA is implicated in breast cancer progression, but oncogenic mutations are rare, and the molecular mechanisms that underlie increased ROCK1 and RhoA expression have not been determined. RhoA-bound ROCK1 phosphorylates myosin light chain (MLC), which is required for actin-myosin contractility. RhoA also activates focal adhesion kinase (FAK) signaling. Together, these pathways are critical determinants of the motile and invasive phenotype of cancer cells. We report that hypoxia-inducible factors coordinately activate RhoA and ROCK1 expression and signaling in breast cancer cells, leading to cell and matrix contraction, focal adhesion formation, and motility through phosphorylation of MLC and FAK. Thus, intratumoral hypoxia acts as an oncogenic stimulus by triggering hypoxia-inducible factor → RhoA → ROCK1 → MLC → FAK signaling in breast cancer cells.
Insights
Hypoxia-inducible factors activate RhoA and ROCK1 signaling in breast cancer cells. This pathway promotes cell motility and invasion, highlighting hypoxia as an oncogenic stimulus.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Rho kinase 1 (ROCK1) and G protein RhoA overexpression are linked to breast cancer progression.
- The precise molecular mechanisms driving ROCK1 and RhoA upregulation remain unclear.
- ROCK1 and RhoA signaling pathways regulate cancer cell motility and invasion.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying increased ROCK1 and RhoA expression in breast cancer.
- To investigate the role of hypoxia-inducible factors in activating RhoA and ROCK1 signaling.
- To determine how hypoxia-triggered signaling impacts breast cancer cell behavior.
Main Methods:
- Analysis of hypoxia-inducible factor (HIF) regulation of RhoA and ROCK1 expression.
- Assessment of RhoA/ROCK1 downstream signaling, including myosin light chain (MLC) and focal adhesion kinase (FAK) phosphorylation.
- Evaluation of cell contractility, focal adhesion formation, and motility in response to hypoxia.
Main Results:
- Hypoxia-inducible factors were found to coordinately activate RhoA and ROCK1 expression and signaling.
- This activation led to increased phosphorylation of MLC and FAK.
- The signaling cascade resulted in enhanced cell and matrix contraction, focal adhesion formation, and increased cell motility.
Conclusions:
- Intratumoral hypoxia acts as an oncogenic stimulus by activating the hypoxia-inducible factor → RhoA → ROCK1 → MLC → FAK signaling axis.
- This pathway promotes a motile and invasive phenotype in breast cancer cells.
- Targeting this hypoxia-driven signaling pathway may offer therapeutic strategies for breast cancer.
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