Aromatization of testosterone by epithelial tumor cells cultured from patients with ovarian carcinoma.

Abstract

Ovarian epithelial carcinoma originates from the surface mesothelium. It is controversial whether these tumors possess steroidogenic enzymes, similar to malignancies of other ovarian cell types. This study reports aromatase enzymatic activity for three epithelial cell lines, OV1225, OV166, and 2774, established from patients with ovarian adenocarcinoma. Aneuploidy of the cells was demonstrated by flow cytometric DNA analyses which showed OV1225 tetraploid, OV166 near diploid, and 2774 triploid. Estrogen synthesis was confirmed by measurement of estradiol (6 to 11 pg/10(7) cells/24 h) by radioimmunoassay in extracts of conditioned medium. To directly assay aromatase enzymatic activity, intact cells were incubated with tritiated testosterone. Medium was extracted with organic solvent after addition of trace 14C-labeled 17 beta-estradiol and 14C-labeled estrone. Androgen was separated from estrogen by celite column chromatography. Estrogen was further purified by silica gel thin-layer chromatography and derivatization of separate products to acetates. Purity of compounds was confirmed by consistency of the 3H:14C ratio of acetylated product versus that of product recrystallized with authentic standard. Conversion of testosterone to estradiol proceeded with apparent Michaelis-Menten kinetics. The apparent Km was 4 microM, 15 microM, and 59 microM, and the Vmax was 20 pmol/h/mg of cell protein, 52 pmol/h/mg of cell protein, and 152 pmol/h/mg of cell protein for 2774, OV166, and OV1225, respectively. We conclude that at least a portion of ovarian adenocarcinoma possesses sufficient aromatase activity to convert ovarian stromal androgen to estrogen.