title: Reverse-phase protein array analysis to identify biomarker proteins in human pancreatic cancer.
abstract: BACKGROUND
  Pancreatic cancer is the fourth leading cause of cancer death in the United States. The high mortality rate of patients with pancreatic cancer is primarily due to the difficulty of early diagnosis and a lack of effective therapies. There is an urgent need to discover novel molecular targets for early diagnosis and new therapeutic approaches to improve the clinical outcome of this deadly disease.
  
  
  OBJECTIVE
  We utilized the reverse-phase protein assay (RPPA) to identify differentially expressed biomarker proteins in tumors and matched adjacent, normal-appearing tissue samples from 15 pancreatic cancer patients.
  
  
  METHODS
  The antibody panel used for the RPPA included 130 key proteins involved in various cancer-related pathways. The paired t test was used to determine the significant differences between matched pairs, and the false discovery rate-adjusted p values were calculated to take into account the effect of multiple comparisons.
  
  
  RESULTS
  After correcting for multiple comparisons, we found 19 proteins that had statistically significant differences in expression between matched pairs. However, only four (AKT, β-catenin, GAB2, and PAI-1) of them met the conservative criteria (both a q value <0.05 and a fold-change of ≥3/2 or ≤2/3) to be considered differentially expressed. Overexpression of AKT, β-catenin, and GAB2 in pancreatic cancer tissues identified by RPPA has also been further confirmed by western blot analysis. Further analysis identified several significantly associated canonical pathways and overrepresented network functions.
  
  
  CONCLUSIONS
  GAB2, a newly identified protein in pancreatic cancer, may provide additional insight into this cancer's pathogenesis. Future studies in a larger population are warranted to further confirm our results.
authors.affiliation: Department of Epidemiology, Unit 1365, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX, 77030, USA, yjhuang@mdanderson.org.
authors.forename: Yu-Jing
authors.initials: YJ
authors.lastname: Huang
authors.forename: Marsha L
authors.initials: ML
authors.lastname: Frazier
authors.forename: Nianxiang
authors.initials: N
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Chongjuan
authors.initials: C
authors.lastname: Wei
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D040081:Protein Array Analysis / Q000379:methods*; D040901:Proteomics; D059467:Transcriptome
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins