A Randomized Study to Investigate the Presence of Tocopherol Metabolites in the Colon

OBJECTIVES:

• Determine the effect of high γ-tocopherol vitamin E mixture supplementation on plasma levels of α-, γ-, and δ-tocopherols, and prostaglandin E_2 in patients planning to undergo surgery for colorectal cancer by comparing the blood samples collected before and after the supplementation in each of the groups and analyzing levels of tocopherols and their metabolites in urine samples.
• Test the hypothesis that the supplementation reduces oxidative and nitrosative stress by measuring plasma levels of F_2-isoprostane, C-reactive protein, and 3-nitrotyrosine as well as urinary levels of 8-hydroxy-2-deoxyguanosine (8-OHdG).
• Determine the levels of α-, γ-, and δ-tocopherols in colon tissues and analyze immunohistochemically for cell proliferation, apoptosis, β-catenin localization, RXR expression, cyclooxygenase-2, 8-OHdG, and 3-nitrotyrosine levels in colon cancer tissue slides.

OUTLINE: This is a multicenter study. The first 5 patients receive no supplements (to establish laboratory standards), all other patients are randomized to 1 of 3 treatment arms.

• Arm I: Patients receive no intervention before undergoing planned surgery.
• Arm II: Patients receive oral high γ-tocopherol vitamin E mixture supplementation once daily for 1 week before undergoing planned surgery.
• Arm III: Patients receive oral high γ-tocopherol vitamin E mixture supplementation once daily for 2 weeks before undergoing planned surgery.

Blood and urine samples are collected at baseline and on the day of surgery for tocopherol and biomarker analysis. A sample of colon tissue is removed during standard surgical resection for chemical analysis. Plasma, tumor tissue, and nontumorous tissues are analyzed for levels of F_2-isoprostane, 8-OHdG, 3-nitrotyrosine, and prostaglandin E_2 via enzyme immunoassays and for levels of α-, γ-, and δ-tocopherols via HPLC.