Aromatase in Colon Carcinoma

Aromatase is one of the key estrogen-producing enzymes and is regarded as one of the therapeutic targets in estrogen receptor-positive breast cancer patients. Human colon carcinoma has also been recently proposed as being an estrogen-responsive malignancy, but the detailed status of aromatase has not yet been reported. Therefore, in this study, we evaluated the aromatase expression in colon carcinoma using immunohistochemistry and real-time polymerase chain reaction. Aromatase mRNA was significantly higher (p=0.03) in colon carcinoma than in the corresponding non-neoplastic mucosa (n=31). Aromatase immunoreactivity tended to be positively associated with the intratumoral concentration of estrogens (n=53), and in particular, the concentration of estradiol was significantly higher (p=0.02) in aromatase-positive cases in men. Aromatase immunoreactivity was detected in the cytoplasm of the carcinoma cells in 217/328 (65%) examined colon carcinoma cases. Aromatase immunoreactivity was significantly positively correlated with tubular differentiation, and inversely correlated with Ki-67 labeling index, although not necessarily correlated with the clinical outcome of the patients. All these results demonstrate that colon carcinoma expresses functional aromatase, and that estrogens are locally synthesized in the tumor tissues. The findings reported here could contribute to a better understanding of the actions of estrogen in colon carcinoma.