Loss of clusterin both in serum and tissue correlates with the tumorigenesis of esophageal squamous cell carcinoma via proteomics approaches

2003 
AIM: 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 postsurgery serum; and pre-surgery and normal control serum were separated by two-dimensional electrophoresis (2-DE)to identify differentially expressed proteins. The silverstained 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 downregulated 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 RTPCR and western blot.CONCLUSION: 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.
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