title: Characterization of periostin isoform pattern in non-small cell lung cancer.
abstract: BACKGROUND
  The extracellular matrix N-glycoprotein periostin (OSF-2, POSTN) is a major constituent of the desmoplastic stroma around solid tumors. It promotes tumor invasion and metastasis via epithelial-mesenchymal transition (EMT). In this study we investigated periostin expression at both RNA and protein level as well as the expression pattern of its splice isoforms in non-small cell lung cancer (NSCLC).
  
  
  METHODS
  Thirty fresh frozen and corresponding formalin-fixed NSCLC tissues (adeno- and squamous cell carcinoma subtype, each n=15) and their matched non-neoplastic tissues were investigated. Periostin mRNA levels were analyzed by quantitative RT-PCR. The EMT-markers periostin and vimentin were analyzed by immunohistochemistry. Laser capture microdissection allowed for analysis of periostin expression in tumor epithelia and stroma, separately. Isoform patterns were investigated by isoform-specific PCR following sequencing in NSCLC, fetal and adult normal lung tissue.
  
  
  RESULTS
  The qRT-PCR analysis showed periostin mRNA up-regulation in NSCLC tissue in relation to normal lung, with significantly higher levels in the adeno-compared to the squamous cell subtype (p<0.05). However, protein levels in both tumor epithelia and stroma correlated with squamous cell carcinoma (p<0.001) and larger tumor size (p<0.05). Further, periostin tumor epithelia expression, correlated with higher tumor grade (p<0.05). Sequence analysis detected eight periostin isoforms in fetal lung, but only five in both NSCLC and matched normal lung tissue. Among the eight isoforms, four are new and were labelled 5, 7, 8 and 9. The exclusive presence of isoforms 1 and 9 in fetal tissue suggests splice-specific regulation during lung embryogenesis. Finally, laser capture microdissection demonstrated that both tumor epithelia and stromal cells can be a source of periostin production in NSCLC.
  
  
  CONCLUSIONS
  This study represents the first analysis of periostin isoform expression patterns in NSCLC and a characterization of periostin expression in cancer versus stromal cells at both RNA and protein level.
authors.affiliation: Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Morra
authors.forename: Markus
authors.initials: M
authors.lastname: Rechsteiner
authors.forename: Silvia
authors.initials: S
authors.lastname: Casagrande
authors.forename: Adriana
authors.initials: A
authors.lastname: von Teichman
authors.forename: Peter
authors.initials: P
authors.lastname: Schraml
authors.forename: Holger
authors.initials: H
authors.lastname: Moch
authors.forename: Alex
authors.initials: A
authors.lastname: Soltermann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism*; D015331:Cohort Studies; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D061346:Laser Capture Microdissection / Q000379:methods; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology; D014746:Vimentin / Q000235:genetics / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; C512835:POSTN protein, human; D020033:Protein Isoforms; D012333:RNA, Messenger; D014746:Vimentin