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Functional interaction of tumor suppressor DLC1 and caveolin-1 in cancer cells

Xiaoli Du1, Xiaolan Qian, Alex Papageorge

  • 1Laboratory of Cellular Oncology, Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.

Cancer Research
|June 14, 2012
PubMed

Insights

Deleted in liver cancer 1 (DLC1) interacts with Caveolin-1 (CAV-1) via its START domain, a novel tumor suppressor mechanism. This interaction is crucial for DLC1

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • Deleted in liver cancer 1 (DLC1) is a tumor suppressor gene frequently inactivated in non-small cell lung cancer (NSCLC).
  • DLC1 encodes a protein with RhoGTPase-activating (RhoGAP) and StAR-related lipid transfer (START) domains, but its START domain interactions were unmapped.
  • Caveolin-1 (CAV-1) also acts as a tumor suppressor and forms a complex with DLC1.

Purpose of the Study:

  • To map the interaction region between DLC1 and CAV-1.
  • To investigate the functional significance of the DLC1-CAV-1 interaction in tumor suppression.
  • To explore the clinical relevance of DLC1 and CAV-1 expression in lung cancer.

Main Methods:

  • Site-directed mutagenesis to disrupt the DLC1 START domain.
  • Co-immunoprecipitation and immunofluorescence to assess DLC1-CAV-1 interaction and colocalization.
  • Cell proliferation assays to evaluate tumor suppressor function.
  • Analysis of public datasets for DLC1 and CAV-1 expression correlation and clinical outcome in NSCLC.

Main Results:

  • The DLC1 START domain was identified as the region required for interaction with CAV-1.
  • Mutation of the DLC1 START domain disrupted its interaction and colocalization with CAV-1.
  • DLC1 with a mutated START domain failed to suppress neoplastic growth, despite retaining RhoGAP activity.
  • DLC1 and CAV-1 expression levels were correlated in NSCLC cell lines and tumors.
  • Low DLC1 expression was associated with poor clinical outcomes in lung cancer patients.

Conclusions:

  • Complex formation between the DLC1 START domain and CAV-1 is a novel, RhoGAP-independent mechanism contributing to DLC1's tumor suppressor function.
  • The DLC1-CAV-1 interaction is critical for DLC1's ability to inhibit neoplastic growth.
  • DLC1 inactivation, potentially through disruption of this complex, contributes to cancer progression.
  • These findings highlight a new therapeutic target for lung cancer.

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