Assessment of Direct Biomarkers of Aspirin Action to Develop a Precision Chemoprevention Therapy of Colorectal Cancer

Acetylsalicylic acid (ASA) seems the ideal colorectal cancer (CRC) chemoprevention agent. Several ongoing trials are testing the effect of ASA as co-therapy in CRC. The mechanisms of action, the appropriate dose and the ideal target population are unknown. The investigators have demonstrated that doses of 100 mg of ASA induce direct and partial but persistent acetylation of the cyclooxygenase (COX) isoenzyme COX-1 in the normal colorectal mucosa. The primary objective is to perform a study of aspirin by using a proteomic assay for comparing platelet COX-1 and CRC mucosal COX-1 after different doses of ASA. Secondary objectives are: the measurement of prostaglandin E2 (PGE2) and phosphorylated S6 protein (p-S6) levels in CRC mucosa, the assessment of indirect biomarker of aspirin action (serum thromboxane B2 (TXB2) and urinary levels of 11-dehydro-TXB2 (TX-M)), the evaluation of systemic biomarkers of inflammatory/tumorigenic COX-2 by assessing urinary levels of major metabolite of PGE2 (PGE-M). Methods: Phase II randomized clinical trial in 60 patients with newly diagnosed CRC in 3 groups of 20 patients receiving 100 or 300 mg/day, or 100 mg/12 hours of enteric-coated ASA for 3±1 weeks, prior to definitive treatment by surgery. Main outcome: Acetylation of COX-1 and COX-2. Eicosanoid levels in target organs. Expected results: Evidence for the current uncertainty about the mechanisms of action and the dose required to obtain the best chemopreventive effect with ASA in CRC. Confirm acetylation of COX as a key biomarker of efficacy with ASA.