title: Tumor protein D54 is a negative regulator of extracellular matrix-dependent migration and attachment in oral squamous cell carcinoma-derived cell lines.
abstract: OBJECTIVE
  Tumor protein D54 (TPD54) belongs to the TPD52 family of proteins and is expressed in several types of cancer, including oral squamous cell carcinoma (OSCC). Here, we investigated relationships between various OSCC-related characteristics and TPD54 expression in vitro.
  
  
  METHODS
  The expression of TPD54 in several OSCC-derived cell lines and normal, non-malignant, cells was assessed. Based on the results obtained, OSCC-derived SAS cells were subsequently subjected to exogenous over-expression of alternative splice variants (ASVs) of TPD54 and to TPD54 knock-down, mediated by siRNA. Next, the role of TPD54 in cellular growth, apoptosis, invasion, migration and extracellular-matrix (ECM)-dependent migration and attachment was investigated, as also the concomitant expression of integrins and integrin-related proteins by the OSCC-derived cells.
  
  
  RESULTS
  Western blot analysis and RT-PCR revealed that several TPD54 ASVs were expressed in the OSCC-derived cell lines tested. Neither exogenous ASV over-expression nor TPD54 knock-down modulated the proliferation or invasion of SAS cells in a monolayer culture assay. However, exogenous ASV over-expression did decrease anchorage-independent growth and TPD54 knock-down did increase anchorage-independent growth, irrespective of caspase activities. The same effects were observed on ECM-dependent cellular migration and cell attachment to the ECM. The expression levels of the major α and β integrin subunits, and of E-cadherin, were found to be similar to those observed in the non-transfected control cells, whereas talin1 expression was found to be increased after TPD54 knock-down. Also Akt was found to be activated after TPD54 knock-down, even in the absence of serum stimulation. Very similar effects were observed in the OSCC-derived cell lines HSC 2 and HSC 3.
  
  
  CONCLUSIONS
  Our results show that TPD54 affects OSCC cell attachment to the ECM, OSCC cell migration, and Akt/PKB activation by modulating integrin activation via a talin1-mediated inside-out signal of the ECM. Based on these results, we suggest that TPD54 may serve as a novel biomarker for OSCC and as a putative target for OSCC therapy.
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Dentistry, Showa University, 2-1-1 Kitasenzoku, Ota-ku, Tokyo, 145-8515, Japan. mukudai@dent.showa-u.ac.jp
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Mukudai
authors.forename: Seiji
authors.initials: S
authors.lastname: Kondo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fujita
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Yoshihama
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Shirota
authors.forename: Satoru
authors.initials: S
authors.lastname: Shintani
mesh_terms: D017209:Apoptosis / Q000235:genetics; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D005109:Extracellular Matrix / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D016023:Integrins / Q000378:metabolism; D009062:Mouth Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D021122:Protein Subunits / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D044967:Serum / Q000378:metabolism; D016608:Talin / Q000378:metabolism
chemical_list: D016023:Integrins; D009363:Neoplasm Proteins; D021122:Protein Subunits; C486414:TPD52L2 protein, human; D016608:Talin; D051057:Proto-Oncogene Proteins c-akt