Increased Apoptosis in Infiltrating Mononuclear Cells of Colorectal Cancer

Abstract Context.—Disturbance in apoptosis has been proposed as one of the mechanisms involved in the immune response targeting tumor outgrowth. How colorectal cancer cells escape from attack by the immune system is not yet fully understood. Objective.—To investigate apoptotic molecules associated with colorectal cancer counterattack. Design and Setting.—Tissue samples of colon from 12 patients with colorectal cancer were collected and analyzed by immunostaining. In addition to tumorous tissues, corresponding nontumorous specimens of colon were obtained as controls. Main Outcome Measures.—We examined the expression of Bcl-2, Bcl-xl, Bax, caspase-3, and inducible nitric oxide synthase in infiltrating mononuclear cells of colorectal cancer tissues and also in colorectal cancer tissues. The TUNEL assay was used to detect in situ apoptosis. Results.—Apoptosis was barely detectable in specimens of colorectal cancer, which was consistent with an increase in Bcl-2 level and a decrease in caspase-3 level. In cont...