Colon cancer : Disease related proteins in tumor tissue and serum

Despite the progress in surgical techniques and adjuvant therapies the mortality of around 60% within the group of colon cancer patients did not decrease significantly over the last decades. This determines a growing demand for biomarkers for early detection, prognosis and risk assessment in colorectal malignancies. Desirable criteria for such a biomarker test are minimal burden and maximum safety for the patient, cost efficiency and broad acceptance to reach a high compliance of the patients. More than 300 colon tissue samples and 1000 sera were obtained from CRC and FAP patients at the Lübeck and Düsseldorf University Hospitals in Germany. To identify the consequences of genetic aberrations on protein expression level, samples from patients with advanced sporadic colon cancers in which the corresponding mucosa, adenoma, carcinoma and liver metastasis were available, were analyzed by 2-D gel electrophoresis and mass spectrometry. A total of 46 proteins were found to be upregulated during the progression of sporadic cancer, and 26 were downregulated. Several of the identified polypeptides correlate with proteins regulating specific cell functions (cell cycle, cytoskeleton, metabolic pathways). In a further study we used a 2-DE based proteomic approach to compare the expression pattern of normal colonic mucosa vs. mucosa gained from FAP patients, polyps vs. FAP polyps and sporadic vs. FAP associated cancer, respectively. A total of 47 proteins were always present in FAP mucosa and absent in the normal mucosa. Based on a total of 37 proteins FAP polyps and sporadic polyps could be distinctly separated. In addition, the absence/presence pattern of 66 spots allowed to distinguish FAP cancers from sporadic cancers. These data suggest, that proteome analysis makes it possible to diagnose FAP already on macroscopically normal appearing colonic mucosa. By means of SELDI array based investigations we unrevealed 16 serum proteins that were able to classify 98% of all test set samples correctly. Our SELDI results show that serum marker protein profiling enables to diagnose and discern malignant colon cancer patients from healthy individuals. Although these markers need validation before they can be used in clinics they have potential for the design of a marker panel for objective diagnosis and therapeutic strategies for colorectal cancer and metastasis