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Each year, nearly one million people develop colorectal cancer, and 50 % of them are expected to die because of cancer within 5 years of diagnosis. Over the last two decades, significant advances in screening, surgery, adjuvant chemotherapy, and patient monitoring have improved the 5-year survival rate. Colorectal cancer is a molecularly heterogeneous disease, and the analysis of its molecular signatures and the identification of colorectal cancer biomarkers will lead to better screening approaches and personalized therapeutic plans. A biomarker is a substance that can be measured and used as an indicator of a biological and/or pathological state. In cancer pathology, biomarkers can be used to detect the disease, to predict prognosis or response to therapy, and to evaluate the efficacy of therapy thereby improving the patient’s life expectancy and quality of life. The carcinoembryonic antigen (CEA) is the biomarker most frequently used in colorectal cancer. It is effective in the surveillance of colorectal cancer patients and in monitoring the efficacy of therapy, whereas it is less useful in colorectal screening. Recent studies indicate that also CEA-related proteins (CEACAMs) are promising potential colorectal cancer biomarkers. CEA and CEACAM proteins play important roles in cancer pathology, and the analysis of their functions will be useful for the identification of diagnostic and/or prognostic factors and therapeutic targets in colorectal and other cancers. List of Abbreviations CEA Carcinoembyonic Antigen CEACAM Carcinoembryonic Antigen-Family Cell Adhesion Molecule FOBT Fecal Occult Blood Test GPI Glycosylphosphatidylinositol Ig Immunoglobulin IgCAM Ig-like Cell Adhesion Molecule PCR Polymerase Chain Reaction TNM Tumor Nodes Metastases Key Facts of Colorectal Cancer • The intestine is the main site of nutrient absorption; it is subdivided in small and large intestine. The latter comprises the right colon, transverse colon, left colon, sigma, and rectum. • Colorectal cancer develops from uncontrolled growth of colorectal mucosa cells. • Colorectal cancer is an epithelial cancer arising in almost 80 % of cases from nonmalignant lesions that turned into cancer within 5–10 years of their appearance. 686 M. Gemei et al.

Colorectal cancer (CRC) is one of the most common types of cancer; it is diagnosed in more than one million people each year and causes the death of about half of them. Early detection can help to decrease CRC-related mortality. In fact, the 5-year survival rate exceeds 90 % when the disease is localized and is only 10 % in case of metastases. Consequently, it is imperative to improve methods for the early detection of the disease. In this context, genomic approaches have resulted in new CRC biomarkers and have helped to shed light on the genetic basis of cancer as a whole. However, the proteome provides a more dynamic and faithful image of the genetic program of a cell. Hence, given the importance of proteins as effectors of cellular behavior, proteomic analysis has the potential to identify biomarkers that can help to classify and predict CRC. Several proteomic technique, such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), quantitative isotopic protein labeling (SILAC, ICAT, and iTRAQ), and two-dimensional gel electrophoresis (2D-PAGE and 2D-DIGE), are being used in cancer research and can improve the diagnosis of patients; they are also helping to optimize personalized therapy. In this chapter, the main proteomic approaches used in biomarker research will be discussed, together with their impact and potential in the clinical setting. The proteomic biomarkers currently used for CRC diagnosis and/or therapy monitoring will be also described. List of Abbreviations 2D-DIGE Two-Dimensional Differential In-gel Electrophoresis 2D-PAGE Two-Dimensional Polyacrylamide Gel Electrophoresis APC Adenomatous Polyposis Coli CEA Carcinoembryonic Antigen CRC Colorectal Cancer Cy2 Cyanine 2 Fluorescent Dye Cy3 Cyanine 3 Fluorescent Dye Cy5 Cyanine 5 Fluorescent Dye DCBE Double-Contrast Barium Enema ESI Electrospray Ionization FIT Fecal Immunological Test FOBT Fecal Occult Blood Test *Email: salvator@unina.it Biomarkers in Cancer DOI 10.1007/978-94-007-7744-6_16-1 # Springer Science+Business Media Dordrecht 2014