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Ral GTPase Activation by Downregulation of RalGAP Enhances Oral Squamous Cell Carcinoma Progression.
P Gao1,2,3, S Liu4, R Yoshida5
11 State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Department of General and Emergency Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
Journal of Dental Research
|July 23, 2019
Summary
Ral GTPases are implicated in oral cancer progression. Downregulation of RalGAPα2, potentially via epigenetic changes, increases Ral GTPase activity, promoting oral squamous cell carcinoma (OSCC) cell migration and invasion.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- Ral small GTPases (RalA and RalB) are Ras family members activated by RalGEFs, which are downstream of Ras.
- Ral GTPase activity is negatively regulated by RalGAP complexes.
- Ral is known to be involved in pancreatic and lung cancers, but its role in oral squamous cell carcinoma (OSCC) is not well understood.
Purpose of the Study:
- To investigate the role of Ral GTPase and its regulator RalGAP in oral squamous cell carcinoma (OSCC).
- To explore the potential epigenetic mechanisms underlying RalGAP downregulation in OSCC.
Main Methods:
- Investigated Ral activation in OSCC cell lines.
- Utilized gene knockdown (RalGAPβ) and overexpression (RalGAPα2) in OSCC cell lines to assess effects on cell motility, migration, and invasion.
- Performed real-time quantitative polymerase chain reaction (RT-qPCR) on patient samples to analyze RalGAPα2 expression.
- Examined DNA methylation and histone modifications of the RalGAPα2 gene in OSCC cell lines.
Main Results:
- Higher Ral activation correlated with increased motility in OSCC cell lines.
- Knockdown of RalGAPβ enhanced RalA activation and promoted migration/invasion in HSC-2 cells.
- Overexpression of RalGAPα2 attenuated RalA activation and inhibited migration/invasion in TSU cells.
- RalGAPα2 expression was significantly downregulated in oral cancer tissues compared to normal epithelia.
- Lower RalGAPα2 expression in OSCC patients correlated with worse overall survival.
- Epigenetic modifications, including DNA methylation and histone H4Ac/H3K27me2 crosstalk, were implicated in RalGAPα2 downregulation.
Conclusions:
- Ral GTPase activation, driven by RalGAP downregulation through epigenetic mechanisms, contributes to OSCC progression.
- RalGAPα2 downregulation is a potential biomarker for poor prognosis in OSCC.
- Targeting the Ral GTPase pathway or addressing epigenetic dysregulation may offer therapeutic strategies for OSCC.
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