title: SILAC-based quantitative proteomic analysis of gastric cancer secretome.
abstract: OBJECTIVE
  Gastric cancer is a commonly occurring cancer in Asia and one of the leading causes of cancer deaths. However, there is no reliable blood-based screening test for this cancer. Identifying proteins secreted from tumor cells could lead to the discovery of clinically useful biomarkers for early detection of gastric cancer.
  
  
  METHODS
  A SILAC-based quantitative proteomic approach was employed to identify secreted proteins that were differentially expressed between neoplastic and non-neoplastic gastric epithelial cells. Proteins from the secretome were subjected to SDS-PAGE and SCX-based fractionation, followed by mass spectrometric analysis on an LTQ-Orbitrap Velos mass spectrometer. Immunohistochemical labeling was employed to validate a subset of candidates using tissue microarrays.
  
  
  RESULTS
  We identified 2205 proteins in the gastric cancer secretome of which 263 proteins were overexpressed greater than fourfold in gastric cancer-derived cell lines as compared to non-neoplastic gastric epithelial cells. Three candidate proteins, proprotein convertase subtilisin/kexin type 9 (PCSK9), lectin mannose binding 2 (LMAN2), and PDGFA-associated protein 1 (PDAP1) were validated by immunohistochemical labeling.
  
  
  CONCLUSIONS
  We report here the largest cancer secretome described to date. The novel biomarkers identified in the current study are excellent candidates for further testing as early detection biomarkers for gastric adenocarcinoma.
authors.affiliation: Institute of Bioinformatics, International Technology Park, Bangalore, India.
authors.forename: Arivusudar
authors.initials: A
authors.lastname: Marimuthu
authors.forename: Yashwanth
authors.initials: Y
authors.lastname: Subbannayya
authors.forename: Nandini A
authors.initials: NA
authors.lastname: Sahasrabuddhe
authors.forename: Lavanya
authors.initials: L
authors.lastname: Balakrishnan
authors.forename: Nazia
authors.initials: N
authors.lastname: Syed
authors.forename: Nirujogi Raja
authors.initials: NR
authors.lastname: Sekhar
authors.forename: Teesta V
authors.initials: TV
authors.lastname: Katte
authors.forename: Sneha M
authors.initials: SM
authors.lastname: Pinto
authors.forename: Srinivas M
authors.initials: SM
authors.lastname: Srikanth
authors.forename: Praveen
authors.initials: P
authors.lastname: Kumar
authors.forename: Harsh
authors.initials: H
authors.lastname: Pawar
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Kashyap
authors.forename: Jagadeesha
authors.initials: J
authors.lastname: Maharudraiah
authors.forename: Hassan
authors.initials: H
authors.lastname: Ashktorab
authors.forename: Duane T
authors.initials: DT
authors.lastname: Smoot
authors.forename: Girija
authors.initials: G
authors.lastname: Ramaswamy
authors.forename: Rekha V
authors.initials: RV
authors.lastname: Kumar
authors.forename: Yulan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Meltzer
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Roa
authors.forename: Raghothama
authors.initials: R
authors.lastname: Chaerkady
authors.forename: T S Keshava
authors.initials: TS
authors.lastname: Prasad
authors.forename: H C
authors.initials: HC
authors.lastname: Harsha
authors.forename: Aditi
authors.initials: A
authors.lastname: Chatterjee
authors.forename: Akhilesh
authors.initials: A
authors.lastname: Pandey
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D007553:Isotope Labeling; D037241:Mannose-Binding Lectins / Q000737:chemistry / Q000378:metabolism; D013058:Mass Spectrometry; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000737:chemistry / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D040901:Proteomics; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D000596:Amino Acids; D014408:Biomarkers, Tumor; D036341:Intercellular Signaling Peptides and Proteins; C086797:LMAN2 protein, human; D037241:Mannose-Binding Lectins; D026901:Membrane Transport Proteins; C103312:PDAP1 protein, human; D011506:Proteins; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases