title: Proteome analysis and tissue array for profiling protein markers associated with type B thymoma subclassification.
abstract: BACKGROUND
  The prognostic relevance of World Health Organization (WHO) subtypes within type B thymomas is still controversial. Understanding of the molecular characteristics of the different histologic types of thymomas will provide meaningful information for diagnosis and therapeutic management in type B thymoma.
  
  
  METHODS
  Proteins extracted from twelve type B thymoma tissue specimens (six type B1 and six type B2) were analyzed by two-dimensional electrophoresis (2-DE) coupled with MALDI-TOF-MS. Differentially expressed proteins were then assayed in sixty-nine type B thymoma tissues (including B1, B2 and B3) by tissue array analysis with immunohistochemistry staining. The relationship of their expression with clinicopathological parameters, such as tumor stage or WHO classification, was estimated by Spearman's Rank Correlation Test.
  
  
  RESULTS
  Sixteen differentially expressed proteins between type B1 and B2 thymoma tissues were identified. The differential levels of ezrin and glutathione S-transferase pi (GSTP1) were validated using immunohistochemistry staining. A statistically significant difference was observed in the positive rate of ezrin expression between type B1 thymoma and type B3 thymoma (Z = -2.963, P < 0.01). Ezrin showed a tendency to be expressed in higher classification tumors from type B1 to B3. A statistical analysis demonstrated that type B2 and B3 tumors had significantly higher positive expression of GSTP1 than the B1 group (type B2 vs. B1: Z = -2.582, P = 0.01; type B3 vs. B1: Z = -4.012, P ≤ 0.001). The results also showed a strong correlation between GSTP1 and WHO type staging of B1 to B3 tumors (Spearman's correlation coefficient: 0.633, P ≤ 0.001). Statistical analysis showed that there was close correlation between GSTP1 and ezrin expression with the clinical stage (Spearman's correlation coefficients, ezrin: 0.481, P < 0.05; GSTP1: 0.484, P < 0.01).
  
  
  CONCLUSIONS
  Differentially expressed proteins between type B1 and B2 thymoma tissues were analyzed by comparative proteomic analysis. The techniques of proteomic analysis and tissue array provide a potential tool for screening of key molecules in type B thymoma histological sub-classifications. The statistical analysis of ezrin and GSTP1 expression by immunohistochemistry, especially GSTP1, may be a useful approach for type B thymoma classification.
authors.affiliation: Basic Research Laboratory, Shanghai Chest Hospital affiliated to Shanghai Jiao Tong University, Shanghai 200030, China.
authors.forename: Qiang-Ling
authors.initials: QL
authors.lastname: Sun
authors.forename: Wen-Tao
authors.initials: WT
authors.lastname: Fang
authors.forename: Jian
authors.initials: J
authors.lastname: Feng
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Yang
authors.forename: Zhi-Tao
authors.initials: ZT
authors.lastname: Gu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.forename: Hui-Fang
authors.initials: HF
authors.lastname: Sha
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003598:Cytoskeletal Proteins / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D051549:Glutathione S-Transferase pi / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013945:Thymoma / Q000145:classification* / Q000378:metabolism*; D046888:Tissue Array Analysis; D055815:Young Adult; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D051549:Glutathione S-Transferase pi; D020543:Proteome; D000099149:Ezrin