Focal adhesions and associated proteins in medullary thyroid carcinoma cells

Lawrence T. Kim, Jason B. Fleming, Christie Lopez-Guzman, Fiemu Nwariaku

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Background. In medullary thyroid carcinoma (MTC), mutations in the RET protooncogene lead to oncogenic transformation. RET activation in other cell types has been shown to cause phosphorylation of the focal adhesion-associated proteins focal adhesion kinase (FAK), paxillin, and p130CAS. We hypothesized that adhesion-dependent signaling might be deranged in MTC cells. Methods. Indirect immunofluorescence was used to label β1 integrin, FAK, paxillin, and p130CAS. Rhodamine-labeled phalloidin was used to visualize actin microfilaments. Phosphorylated protein was detected by immunoprecipitation followed by Western blotting for phosphotyrosine. MTC cell invasiveness was quantified using a modified Boyden chamber assay. Results. Clustering of β1 integrin, FAK, paxillin, and p130CAS into focal adhesions were not detected in MTC cells under any conditions, although clustering was seen as expected in control HeLa cells. Despite this failure, FAK, paxillin and p130CAS were all found to be phosphorylated. Actin microfilaments were generally not seen although in a few cells, small, poorly formed microfilaments could be detected. MTC cells invaded poorly as compared with highly invasive cell lines. However a clear difference was noted between invasiveness on growth factor depleted Matrigel and regular Matrigel. Conclusions. In MTC cells, focal adhesions are not seen in response to interaction with extracellular matrix. Consistent with this failure, actin microfilaments are absent or poorly formed and invasion is weak. Despite the absence of focal adhesions, focal adhesion proteins remain phosphorylated, even though in normal cells their signaling activity is dependent on focal adhesion formation. Deranged adhesion-dependent signaling may contribute to MTC pathogenesis.

Original languageEnglish (US)
Pages (from-to)177-184
Number of pages8
JournalJournal of Surgical Research
Volume111
Issue number2
StatePublished - May 15 2003

Keywords

  • Cell adhesion
  • Focal adhesions
  • Integrins
  • Medullary thyroid cancer
  • Protein tyrosine kinases

ASJC Scopus subject areas

  • Surgery

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