Identification of New Diagnostic Protein Markers for Colorectal Cancer in Circulating Tumor Exosomes

In terms of frequency, colorectal cancer is the third most common cancer diagnosed in men and the second in women. Screening for colon and rectal cancer is based on the search for blood in the stool. The detection of occult bleeding is an indication for colonoscopy to find the origin of this bleeding. In this context, the search for biochemical markers in the blood of patients for diagnostic purposes has not yielded satisfactory results to date. Cancer cells, including colorectal cancer cells, release extracellular vesicles that contain proteins, mRNAs, DNA that can be transferred to neighboring cells but that also circulate through the blood stream and can modulate tumor progression and metastatic spread. These extracellular vesicles are of two types: exosomes (40 to 100 nm in diameter) formed by budding of endosome membranes and microvesicles (100 to 1000 nm in diameter) resulting from the budding of plasma membrane. Exosomes carry transmembrane proteins on their surface, called tetraspanins (CD9, CD63, CD81) but they also contain proteases involved in the degradation of the extracellular matrix, integrins involved in the tropism of metastases, and matrix macromolecules involved in the control of tumor invasion. The working hypothesis is that some of these exosomal proteins may be good diagnostic and / or prognostic markers for colorectal cancer. This project will aim to isolate exosomes from patient blood and to quantify previously cited proteins according to the accreditation criteria of clinical laboratory biology analyzes. For this purpose, exosomes will be isolated from sera of patients and their number, size and protein composition will be characterized. This project is an innovative and non-invasive prospective approach in the screening of protein markers for colorectal cancer diagnostic and / or prognostic.