Loss of clusterin both in serum and tissue correlates with the tumorigenesis of esophageal squamous cell carcinoma via proteomics approaches.
OBJECTIVE
To identify the differentially secreted proteins or polypeptides associated with tumorigenesis of esophageal squamous cell carcinoma (ESCC) from serum and to find potential tumor secreted biomarkers.


METHODS
Proteins from human ESCC tissue and its matched adjacent normal tissue; pre-surgery and post-surgery serum; and pre-surgery and normal control serum were separated by two-dimensional electrophoresis (2-DE) to identify differentially expressed proteins. The silver-stained 2-DE were scanned with digital ImageScanner and analyzed with ImageMaster 2D Elite 3.10 software. A cluster of protein spots differentially expressed were selected and identified with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). One of the differentially expressed proteins, clusterin, was down-regulated in cancer tissue and pre-surgery serum, but it was reversed in post-surgery serum. The results were confirmed by semi-quantitative reverse-transcription (RT)-PCR and western blot.


RESULTS
Comparisons of the protein spots identified on the 2-DE maps from human matched sera showed that some proteins were differentially expressed, with most of them showing no differences in composition, shape or density. Being analyzed by MALDI-TOF-MS and database searching, clusterin was differentially expressed and down-regulated in both cancer tissue and pre-surgery serum compared with their counterparts. The results were also validated by RT-PCR and western blot.


CONCLUSIONS
The differentially expressed clusterin may play a key role during tumorigenesis of ESCC. The 2DE-MS based proteomic approach is one of the powerful tools for discovery of secreted markers from peripheral.
Zhang
Li-Yong
LY
National Laboratory of Molecular Oncology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, Beijing, China.
Ying
Wan-Tao
WT
Mao
You-Sheng
YS
He
Hong-Zhi
HZ
Liu
Yu
Y
Wang
Hui-Xin
HX
Liu
Fang
F
Wang
Kun
K
Zhang
De-Chao
DC
Wang
Ying
Y
Wu
Min
M
Qian
Xiao-Hong
XH
Zhao
Xiao-Hang
XH
D000368:Aged; D000595:Amino Acid Sequence; D014408:Biomarkers, Tumor / Q000097:blood; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000097:blood / Q000473:pathology* / Q000601:surgery; D051152:Clusterin; D004938:Esophageal Neoplasms / Q000097:blood / Q000473:pathology* / Q000601:surgery; D005260:Female; D006023:Glycoproteins / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018832:Molecular Chaperones / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000097:blood / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D020543:Proteome; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D014408:Biomarkers, Tumor; C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D020543:Proteome