Tu1672 IL-21 Production and Function in Peripheral Immune Cells From Crohn's Disease Patients

Introduction:Currently available biomarkers are aiming at the detection of advanced colorectal cancer (CRC) but are of limited value for the detection of premalignant lesions in the colon prior to endoscopy. Here, we identified a precursor protein, denoted Daedalus, for colorectal polyps by using mass spectrometry. Methods:Serum samples from patients were obtained prior to screening colonoscopy for the detection of colorectal polyps and cancer. We purified low-abundance serum proteins from serum samples of healthy controls without polyps, patients with colonic polyps and patients with colorectal cancer cancer by using a novel tandem immunoaffinity depletion system for enhanced detection of low abundance proteins in humans. We then subjected proteins in the flow-through and eluted fractions to tryptic digestion and subsequent analysis by label-free quantitative mass spectrometry with the aim to identify proteins which were specific for the polyp and cancer samples and therefore constitute potential biomarkers. After verification by Western blotting and ELISA, we used receiver operating characteristics (ROC) to calculate the diagnostic accuracy of the identified proteins. Results:We identified several upregulated proteins in the fractionated plasma samples by comparing cancer, polyp and control groups via quantitative mass spectrometry. Western blot analysis with unfractionated plasma samples confirmed that the proteins Daedalus and CRP were significantly increased in the serum of cancer patients and polyp patients compared to healthy controls. ELISA measurements of serum samples from 57 patients yielded the same results. No differences between cancer and polyp patients were noted. The area under a receiver operating characteristic (ROC) curve was 0.86 for Daedalus and 0.79 for CRP alone when we compared controls vs. polyps/ tumor group. For both proteins in combination an AUC value of 0.93 could be achieved, which resulted in a high sensitivity of 92% for detection of colorectal polyps/tumors. Discussion:We identified biomarkers which were able to distinguish control patients from either colorectal polyps or colorectal cancer patients. To our knowledge, Daedalus is the first serum marker protein with high sensitivity and marked specificity for detection of colorectal polyps. Serum testing of Daedalus might allow the stratification of patients for surveillance colonoscopy.