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Expression of ral GTPases, their effectors, and activators in human bladder cancer

Steven Christopher Smith1, Gary Oxford, Alexander S Baras

  • 1Department of Molecular Physiology, University of Virginia, Charlottesville, Virginia 22908, USA.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|July 4, 2007
PubMed
Abstract

Insights

This study reveals RalA and RalB GTPase activation and differential expression in bladder cancer, linking prior model system findings to human disease and suggesting potential therapeutic targets.

Area of Science:

  • Oncology
  • Molecular Biology
  • GTPase Signaling

Background:

  • The Ral family of small G proteins (GTPases) is implicated in cancer progression.
  • Previous studies suggested roles in tumorigenesis, invasion, and metastasis in model systems.
  • A comprehensive analysis of Ral GTPase activation and expression in human tumors was lacking.

Purpose of the Study:

  • To systematically evaluate the activation state, mutation status, and expression levels of RalA and RalB in bladder cancer.
  • To correlate these findings with tumor characteristics and known oncogenic pathways.
  • To establish a link between in vitro/animal model findings and human bladder cancer.

Main Methods:

  • Assessed RalA and RalB activation in 10 bladder cancer cell lines with varying Ras mutation status.
  • Sequenced RalA and RalB cDNAs from 20 bladder cancer cell lines and functionally characterized mutations.
  • Quantified mRNA and protein expression of Ral GTPases, activators (e.g., Aurora-A), and effectors (e.g., RalBP1, Filamin A) in cell lines and tissues.

Main Results:

  • Identified one RalA E97Q mutation in 20 cell lines; observed higher Ral activation in cells with mutant HRAS.
  • Found significant overexpression of RalA and Aurora-A mRNA in bladder cancer, correlating with higher stage and grade.
  • Demonstrated overexpression of RalBP1 (mRNA/protein) and underexpression of Filamin A in bladder cancer; confirmed RalA mRNA-protein correlation and overexpression of both GTPases in invasive cancers.

Conclusions:

  • The findings demonstrate RalA and RalB activation and differential expression in human bladder cancer.
  • These results connect prior model system data to human disease.
  • Targeting the Ral GTPase pathway presents a potential therapeutic strategy for bladder cancer.

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