CYP19 gene expression and aromatase activity in endometrial cancer tissue: importance of the type of the disease.

Aromatase (CYP19) activity in malignant endometrium presents local mechanism with potential ability to support tumor growth. The data on interrelation between activity of this enzyme and its mRNA signal in endometrial cancer (EC) tissue are very scarce and inconclusive. To correct this gap we studied aromatase activity and gene expression totally in 19 samples of EC (17 of them -- from postmenopausal women) collected during surgery. Aromatase activity was evaluated by tritium water release assay and CYP19 gene expression -- with rt-PCR. Additionally, all studied EC cases were divided on the basis of case history and some characteristics of host and tumor and in accordance with existing classification into cases belonging to type I or II of the disease (correspondingly, 13 and 6 observations). Positive correlation between enzyme activity and CYP19 mRNA signal (R(s)=+0.63, p<0.05) was revealed in the whole group of studied samples. Aromatase activity varied in evaluated material between 1.45 fM/mg prot./hr and 11.49 fM/mg prot./hr, and in type II cases it was higher (7.27+/-0.96 fM/mg prot/hr) than in type I observations (4.96+/-0.66 fM/mg prot./hr, p=0.066). CYP19 mRNA expression was not revealed in 6 cases and all of them belonged to the type I of disease. Thus, although type II of EC is frequently considered as hormone non-dependent, increased ability of this tumor type to estrogen biosynthesis (on CYP19 gene and protein level) may lead to reconsideration of such conclusion and warrants further investigation.