Michael Tacke

Improved Diagnosis of Colorectal Cancer Using a Combination of Fecal Occult Blood and Novel Fecal Protein Markers

BACKGROUND & AIMS Annual testing for fecal occult blood is recommended as first-line screening for the detection of colorectal cancer (CRC), but is affected by limited sensitivity. We initiated a proteomics-based search for novel biomarkers to improve the sensitivity of detection of CRC in stool samples. METHODS Six markers, including immunologic fecal occult blood test (iFOBT), were evaluated in a collective of 551 samples (186 CRC, 113 advanced adenoma, and 252 control patients) to establish the diagnostic performance of each marker and marker combinations. RESULTS We tested the known stool markers hemoglobin (iFOBT), hemoglobin-haptoglobin, calprotectin, carcinoembryogenic antigen, and the novel fecal markers tissue inhibitor of metalloproteinase-1 (TIMP-1) and S100A12. The best diagnostic performance was found for S100A12 with an area under the curve of 0.95, followed by TIMP-1 (0.92), hemoglobin-haptoglobin (0.92), hemoglobin (0.91), calprotectin (0.90), and carcinoembryogenic antigen (0.66). By using Bayes logistic regression as a mathematic model, the highest sensitivity (88%) for the detection of CRC at 95% specificity was obtained with the marker pair S100A12 and hemoglobin-haptoglobin. Increasing the specificity to 98%, the combination of S100A12, hemoglobin-haptoglobin, and TIMP-1 resulted in a sensitivity of 82%, with the highest increase of sensitivity found in early tumor stages (international union against cancer stage I: 74% sensitivity vs 57% of the best single marker). CONCLUSIONS Depending on the specificity selected, a marker pair, S100A12 and hemoglobin-haptoglobin, or a triple combination including TIMP-1, allowed the detection of CRC at significantly higher rates than can be obtained with iFOBT alone.

Towards a comprehensive proteome of normal and malignant human colon tissue by 2‐D‐LC‐ESI‐MS and 2‐DE proteomics and identification of S100A12 as potential cancer biomarker

The aim of this study was to characterize the proteome of normal and malignant colonic tissue. We previously studied the colon proteome using 2‐DE and MALDI‐MS and identified 734 proteins (Roeßler, M., Rollinger, W., Palme S., Hagmann, M.‐L., et al.., Clin. Cancer Res. 2005, 11, 6550–6557). Here we report the identification of additional colon proteins from the same set of tissue samples using a complementary nano‐flow 2‐D‐LC‐ESI‐MS. In total, 484 proteins were identified in colon. Of these, 252 had also been identified by the 2‐DE/MALDI‐MS approach, whereas 232 proteins were unique to the 2‐D‐LC‐ESI‐MS analysis. Comparing protein expression in neoplastic and normal colon tissue indicated elevated expression of several proteins in colorectal cancer, among them the well established tumor marker carcinoembryonic antigen, as well as calnexin, 40S ribosomal protein S15a, serpin H1, and S100A12. Overexpression of these proteins was confirmed by immunoblotting. Serum levels of S100A12 were determined by ELISA and were found to be strongly elevated in colorectal cancer patients compared to healthy individuals. We conclude, that 2‐D‐LC‐ESI‐MS is a powerful approach to identify and compare protein profiles of tissue samples, that it is complementary to 2‐DE/MALDI‐MS approaches and has the potential to identify novel biomarkers.

Abstract 2738: Early detection of colorectal cancer applying a combination of serum markers

Background: Fecal occult blood testing (FOBT) is the recommended first line screening for the detection of colorectal cancer (CRC). To improve the detection of CRC we evaluated serum markers and combinations of serum markers as an alternative approach. Methods: Applying Lasso Regression, a specialized form of penalized logistic regression, we selected six markers for an evaluation in a collective of 857 patients including 301 CRC patients, 143 patients with adenoma, 266 healthy controls and 147 disease controls. For each marker and marker combination the performance was assessed. Results: We tested a total of 22 biomarkers for the detection of CRC from serum. Of these six markers were selected for a marker combination by Lasso Regression. Included were the well-known tumor markers CEA and CYFRA21-1 as well as novel markers or markers that are less routinely used for the detection of CRC: ferritin, osteopontin, anti-p53 and seprase. CEA showed the best sensitivity of all markers with 43.9 % at 95% specificity, followed by seprase (42.4%), CYFRA21-1 (35.5%), osteopontin (30.2%), ferritin (23.9%) and anti-p53 (20.0%). When these markers were combined a sensitivity of 72.3% was reached at a corresponding specificity of 95% and of 62.1% at 98% specificity. Focusing on more screening relevant stages, UICC stages 0-III, reduced the sensitivity slightly to 68.0% and 53.3%, respectively. In a sub-collective where matched stool samples were available (75 CRC cases and 234 controls) the sensitivity of the marker combination was comparable to fecal immunochemical testing (FIT) with 82.4% and 68.9% vs. 81.8% and 72.7% at 95% and 98% specificity, respectively. Conclusion: When six markers were combined to detect CRC from serum, the combination reached a performance that was comparable to FIT. This provides a novel tool for CRC screening to trigger a follow-up colonoscopy for a final diagnosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2738.