Molecular biomarkers in the diagnostic of patients with colorectal cancer.

Colorectal cancer (CRC) is currently a well-known and studied issue in experimental research. Worldwide it is the third most common cancer in men and the second most common cancer in women. 70-80% of cases occur sporadically. Most CRCs develop from adenomas. The transition from normal epithelium to adenoma and finally into carcinoma is associated with acquired molecular events. In 5-10 % of cases, CRC develops from germline mutations in cancer-predisposing genes. 15% of patients have a family history of CRC that suggests a hereditary contribution, common exposures or shared risk factors among family members. Genetic alterations in cancer-related genes represent prognostic and predictive CRC biomarkers. Genetic testing of individuals with newly diagnosed CRC as well as of asymptomatic relatives can lead to improved outcomes for the patient and at-risk family members. Discovery of circulating cell-free tumor DNA (ctDNA) promises an improvement of the CRC diagnostics. ctDNA shares common genetic alterations with the primary tumor so it allows non-invasive monitoring of the disease over time. This review is focused on the principal molecular biomarkers associated with CRC and on the key characteristics of initiation and progression of CRC including chromosomal instability, microsatellite instability and signaling pathways where this deregulation leads to tumorigenesis.