Colorectal cancer (CRC) is the fourth most common cause of cancer-related death worldwide. Accurate non-invasive screening for CRC would greatly enhance a population's health. Adenomatous polyposis coli (Apc) gene mutations commonly occur in human colorectal adenomas and carcinomas, leading to Wnt signalling pathway activation. Acute conditional transgenic deletion of Apc in murine intestinal epithelium (AhCre(+)Apc(fl)(/)(fl)) causes phenotypic changes similar to those found during colorectal tumourigenesis. This study comprised a proteomic analysis of murine small intestinal epithelial cells following acute Apc deletion to identify proteins that show altered expression during human colorectal carcinogenesis, thus identifying proteins that may prove clinically useful as blood/serum biomarkers of colorectal neoplasia. Eighty-one proteins showed significantly increased expression following iTRAQ analysis, and validation of nine of these by Ingenuity Pathaway Analysis showed they could be detected in blood or serum. Expression was assessed in AhCre(+)Apc(fl)(/)(fl) small intestinal epithelium by immunohistochemistry, western blot and quantitative real-time PCR; increased nucelolin concentrations were also detected in the serum of AhCre(+)Apc(fl)(/)(fl) and Apc(Min)(/)(+) mice by ELISA. Six proteins; heat shock 60kDa protein 1, Nucleolin, Prohibitin, Cytokeratin 18, Ribosomal protein L6 and DEAD (Asp-Glu-Ala-Asp) box polypeptide 5,were selected for further investigation. Increased expression of 4 of these was confirmed in human CRC by qPCR. In conclusion, several novel candidate biomarkers have been identified from analysis of transgenic mice in which the Apc gene was deleted in the intestinal epithelium that also showed increased expression in human CRC. Some of these warrant further investigation as potential serum-based biomarkers of human CRC.
Keywords: Adenomatous polyposis coli; AhCre(+)Apc(+/+); AhCre(+)Apc(fl)(/)(fl); Apc; Apc(Min/+); Biomarkers; CK18; CRC; CTBRC; Cancer Tissue Bank Research Centre; Colorectal cancer; Cytokeratin 18; DDX5; DEAD (Asp-Glu-Ala-Asp) box polypeptide 5; ECE; FAP; FDR; HSPD1; IHC; IPA; LC MS/MS; MMTS; NCL; Nucleolin; PCR; PHB; Prohibitin; Proteomics; ROC; RPL6; Ribosomal protein L6; SEM; TCEP; TEAB; TFA; WB; acute conditional transgenic deletion of the Apc gene in the murine intestinal epithelium; adenomatous polyposis coli; epithelial cell extracts; false discovery rate; familial adenomatous polyposis; gFOBt; germline mutations in the Apc gene, spontaneously develop multiple intestinal adenomas; guaiac faecal blood test; heat shock 60kDa protein 1 (chaperonin); i.p.; iTRAQ; immunohistochemistry; ingenuity pathways analysis; intra-peritoneal; isobaric tags for relative and absolute quantification; liquid chromatography–mass spectrometry; methylmethanethiosulfonate; polymerase chain reaction; receiver operating characteristic; standard error of mean; triethylammonium bicarbonate; trifluoroacetic acid; tris(2-carboxyethyl)phosphine; western blotting; wild type control for acute conditional transgenic deletion of the Apc gene in the murine intestinal epithelium.
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