Quantitative Proteomic Analysis Of Differentially Expressed Proteins In Colorectal Cancer By Colonoscopic Biopsy

Objective Using colorectal biopsies to screening and identifying the differentialexpressed proteins between colorectal cancer and matched adjacent normal tissues bylabel-free quantitative proteomics. In order to provide clues for understanding themolecular mechanisms of colorectal cancer and find potential biomarkers for colorectalcancer. Methods1.Six pairs of human colorectal cancers and their adjacent normaltissues(approx.5cm),were obtained during the colonoscopy screening at ShanghaiJiaotong University Affiliated Sixth People’s Hospital. All of them diagnosised ofadenocarcinoma after surgical resection. After prepared using centrifugal proteomicreactor,two group samples were analysed by Nano LC-MS/MS for selecting andidentifying differentially expressed proteins.Bioinformatics method were applied toanalyse this proteins.2. We use Western Blot to detect the expression level of four proteins(PRELP、SOD3、NGAL and S100A8)which were selected from the quantitative proteomesresults. PRELP and SOD3have been validated by other experiments, while NGAL andS100A8were not. Results1.2281and2266proteins were identified by Label-freequantitative proteomics in colorectal cancer and their adjacent normal tissues, respectively.We identified374significant differential expressed proteins(P<0.05)among2619proteinsin both two groups,137upregulated and127down regulated. The bioinformatics analysisshows that most of them were located in the cytoplasm part, they involved in multiple cellbiological processes,including cell metabolism and molecular transport. KEGG resultsindicated that these proteins involved in21kinds of signal transduction pathways. Thehighest match rate were ribosome and Oxidative phosphorylation pathway.2. Western Blot results indicated that the expression of PRELP and SOD3were downexpressed incolorectal cancer while NGALand S100A8were overexpressed in colorectal cancer.Theseresults were consistent with proteomics. Conclusions1.We identified2619proteins and374differential expressed proteins, they coveraged almost every subcellular site, involvedin multiple cell biological processes and signal transduction pathway. The result mayprovide clues for understanding the molecular mechanisms of colorectal cancer.2.Expression of PRELP and SOD3were downexpressed in colorectal cancer whileNGALand S100A8were overexpressed in colorectal cancer. These four proteins may beassociated with the development and progression of colorectal cancer，and may bepotential biomarkers for early diagnosis of colorectal cancer.3.The label-free quantitativeproteomics combined with biopsy tissues is an effective means of colorectal differenceproteomic study.