Selenium supplementation may increase the efficacy of cetuximab in metastatic colorectal cancer patients

Recently, cyclooxygenase-2 (COX-2) inhibitor therapy has emerged as a possible new approach to the prevention and treatment of colorectal cancer (CRC). The COX enzymes (COX-1 and COX-2) are key enzymes of prostaglandin (PG) biosynthesis and are overexpressed in ≈80% of human CRCs. Presumably, bioactive lipid products of COX, such as PGE2, are responsible for some of the pro-neoplastic effects mediated by this enzyme. The early effects of COX-2-derived PGE2 are in part mediated by the epidermal growth factor receptor (EGFR). Selenomethionine decreases COX-2 protein and PGE2 levels. Cetuximab is a chimeric IgG1 monoclonal antibody that binds to EGFR with high specificity thus blocking ligand-induced phosphorylation of EGFR. Cetuximab has clinically significant activity when given alone or in combination with irinotecan in patients with irinotecan-refractory CRC. We suggest that selenium supplementation by decreasing the COX-2 protein and PGE-2 levels in cancer cells may increase efficacy of cetuximab in advanced CRC patients.