Purpose: It has been extensively documented that the cyclooxygenase inducible form and 15-lipoxygenase are implicated in colorectal carcinogenesis. Nonetheless, the role of other enzymes involved in the arachidonic acid metabolism, such as 5-lipoxygenase, in colorectal neoplasms has not been fully ascertained. This study was designed to evaluate 5-lipoxygenase expression in sporadic colorectal adenocarcinomas by using immunohistochemistry and to analyze its potential correlations with clinicopathologic parameters and with cyclooxygenase-2 expression.
Methods: Expression of 5-lipoxygenase and cyclooxygenase-2 were evaluated by immunohistochemistry in 50 surgically resected sporadic colorectal adenocarcinomas (28 male and 22 female patients age range, 47-88 (mean age, 69 +/- 8) years). The chi-squared and Spearman correlation tests were used to analyze correlations with clinicopathologic characteristics and to evaluate any relationships between expression of the two enzymes. P values <0.05 were considered statistically significant.
Results: 5-Lipooxygenase and cyclooxygenase-2 immunostaining was found in the cytoplasm of neoplastic cells in 41 (82 percent) and in 43 cases (86 percent), respectively. Spearman correlation test demonstrated a positive correlation in the expression of the two enzymes. A statistically significant correlation also was observed between 5-lipoxygenase expression and tumor stage and lymph node metastasis, whereas no significant correlations emerged regarding cyclooxygenase-2 expression and clinicopathologic parameters.
Conclusions: Our study demonstrates that 5-lipoxygenase is expressed in colorectal adenocarcinomas in association with cyclooxygenase-2 expression. Moreover, an elevated expression of this enzyme seems to be significantly correlated with tumor aggressiveness. Further studies would clarify the need for target therapies inhibiting both metabolic pathways in such tumors.