Rac1-mediated cytoskeleton rearrangements induced by intersectin-1s deficiency promotes lung cancer cell proliferation, migration and metastasis

Mol Cancer. 2016 Sep 14;15(1):59. doi: 10.1186/s12943-016-0543-1.


Background: The mechanisms involved in lung cancer (LC) progression are poorly understood making discovery of successful therapies difficult. Adaptor proteins play a crucial role in cancer as they link cell surface receptors to specific intracellular pathways. Intersectin-1s (ITSN-1s) is an important multidomain adaptor protein implicated in the pathophysiology of numerous pulmonary diseases. To date, the role of ITSN-1s in LC has not been studied.

Methods: Human LC cells, human LC tissue and A549 LC cells stable transfected with myc-ITSN-1s construct (A549 + ITSN-1s) were used in correlation with biochemical, molecular biology and morphological studies. In addition scratch assay with time lapse microscopy and in vivo xenograft tumor and mouse metastasis assays were performed.

Results: ITSN-1s, a prevalent protein of lung tissue, is significantly downregulated in human LC cells and LC tissue. Restoring ITSN-1s protein level decreases LC cell proliferation and clonogenic potential. In vivo studies indicate that immunodeficient mice injected with A549 + ITSN-1s cells develop less and smaller metastatic tumors compared to mice injected with A549 cells. Our studies also show that restoring ITSN-1s protein level increases the interaction between Cbl E3 ubiquitin ligase and Eps8 resulting in enhanced ubiquitination of the Eps8 oncoprotein. Subsequently, downstream unproductive assembly of the Eps8-mSos1 complex leads to impaired activation of the small GTPase Rac1. Impaired Rac1 activation mediated by ITSN-1s reorganizes the cytoskeleton (increased thick actin bundles and focal adhesion (FA) complexes as well as collapse of the vimentin filament network) in favor of decreased LC cell migration and metastasis.

Conclusion: ITSN-1s induced Eps8 ubiquitination and impaired Eps8-mSos1 complex formation, leading to impaired activation of Rac1, is a novel signaling mechanism crucial for abolishing the progression and metastatic potential of LC cells.

Keywords: Cbl; Cell migration; Cell proliferation; E3 ubiquitin ligase; Eps8; Intersectin-1s; Lung cancer; Rac1; RhoA; Tumor metastasis; mSos1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adaptor Proteins, Vesicular Transport / deficiency*
  • Animals
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology*
  • Mice
  • Neoplasm Metastasis
  • Neoplasm Transplantation
  • Proto-Oncogene Proteins c-cbl / genetics
  • Proto-Oncogene Proteins c-cbl / metabolism*
  • SOS1 Protein / genetics
  • SOS1 Protein / metabolism*
  • Time-Lapse Imaging
  • Ubiquitination
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Adaptor Proteins, Vesicular Transport
  • EPS8 protein, human
  • ITSN1 protein, human
  • RAC1 protein, human
  • SOS1 Protein
  • Proto-Oncogene Proteins c-cbl
  • rac1 GTP-Binding Protein
  • CBL protein, human