Overexpression of 5-lipoxygenase in sporadic colonic adenomas and a possible new aspect of colon carcinogenesis.

PURPOSE: We aimed to study the intracellular expression of 5-lipoxygenase (5-LOX), the primary competitor with cyclooxygenase-2 in arachidonic acid metabolism, as inflammatory enzymes may be involved in blocking apoptosis and promoting cancer growth by changing arachidonic acid metabolism within cells. Our purpose was to investigate the possible connection between 5-LOX expression and colon carcinogenesis by characterizing 5-LOX expression in histologically different colonic adenomas, determining the relationship between high expression of 5-LOX and various conventional clinicopathological features of adenomas, and finally characterizing the histological localization of cells with 5-LOX overexpression. METHODS: A total of 111 patients were examined and 120 histologically different colonic adenomas analyzed (including four cases of intramucosal adenocarcinoma in a polyp). Immunohistochemical staining with polyclonal anti-5-LOX antibodies was performed. RESULTS: There was a significant correlation between high 5-LOX expression and patient age, increased polyp size, high grade of intraepithelial neoplasia, villous and tubulovillous adenoma, and histological epithelial localization. CONCLUSIONS: We observed a strong positive correlation between 5-LOX overexpression and the appearance of typical high-risk factors for malignant transformation in adenomatous polyps. The results support the role of 5-LOX in early stages of colon carcinogenesis.

Expression of cyclooxygenase-2 in colonic polyps.

INTRODUCTION: Limited data is available regarding the relationships between cyclooxygenase-2 (COX-2) and colorectal cancer formation. OBJECTIVES: The aim of the study was to investigate cyclooxygenase-2 (COX-2) expression in histologically diverse colonic polyps, to determine the association between the expression of this enzyme and selected patho logical and clinical characteristics of polyps, and to establish the location of cells with high COX-2 expression within the polyp. PATIENTS AND METHODS: We examined 212 colonic polyps from 175 patients. Immunohistochemical staining with monoclonal anti-COX-2 antibodies was performed. RESULTS: Statistically significant differences associated with high COX-2 expression were found: in adenomas vs. other polyps (P <0.001), in adenomas with high-grade dysplasia (P <0.000 001), and in polyps of the cecum (P <0.02). Statistically significant differences in COX-2 were also associated with polyp size (P <0.000 001). Cells with high COX-2 expression were usually located in the epithelial layer (P = 0.01). No significant associations were found between high COX-2 expression and the age and sex of patients or the total number of polyps. CONCLUSIONS: We demonstrated that high COX-2 expression is associated with typical risk factors for malignant transformation of colonic polyps. The results suggest the possible role of COX-2 in the early stages of colon carcinogenesis.