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Down-regulation of FXYD3 expression in human lung cancers: its mechanism and potential role in carcinogenesis

Koji Okudela1, Takuya Yazawa, Jun Ishii

  • 1Department of Pathology, Yokohama City University Graduate School of Medicine, Kanazawa-Ku, Yokohama, Japan.

The American Journal of Pathology
|November 7, 2009
PubMed

Insights

FXYD3 (FXYD domain-containing ion-transport associated protein 3) is downregulated in lung cancer, potentially contributing to cancer cell shape changes and progression. Its inactivation may be linked to gene mutations.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • FXYD3 (FXYD domain-containing ion-transport associated protein 3) is a regulator of Na,K-ATPase.
  • Initially identified as overexpressed in breast tumors, its role in lung cancer was unclear.
  • Preliminary data showed FXYD3 downregulation in KRAS-mutated lung cells.

Purpose of the Study:

  • Investigate the role of FXYD3 in lung carcinogenesis.
  • Determine FXYD3 expression levels in lung cancer.
  • Explore the functional impact of FXYD3 loss in lung cancer.

Main Methods:

  • Quantitative analysis of FXYD3 mRNA and protein in lung cancer cell lines and primary tumors.
  • Mutation analysis of the FXYD3 gene.
  • Functional assays involving forced expression of wild-type and mutant FXYD3.
  • Assessment of cytoskeletal organization (cortical actin distribution).
  • Analysis of FXYD3 promoter methylation status.

Main Results:

  • FXYD3 expression was significantly lower in most lung cancer cell lines and primary tumors compared to non-cancerous lung tissue.
  • Decreased FXYD3 levels correlated with tumor dedifferentiation.
  • A somatic mutation (g55c, D19H) was identified in one cell line.
  • Restoration of wild-type FXYD3, but not mutant, normalized cortical actin distribution in FXYD3-deficient cancer cells.
  • No association was found between FXYD3 expression and promoter methylation.

Conclusions:

  • FXYD3 inactivation, potentially via gene mutation or other mechanisms, may contribute to altered cell morphology in lung cancer.
  • FXYD3 plays a role in maintaining cytoskeletal integrity.
  • FXYD3 inactivation could be a factor in lung cancer progression.

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