Stimulation of aromatase activity in breast fibroblasts by tumor necrosis factor

Abstract

The conversion of androstenedione to estrone, the reaction mediated by the aromatase enzyme complex, may make an important contribution to the synthesis of estrogens in breast tissues. In the present study, the effect of the cytokine, TNFα, on aromatase activity was examined in breast fibroblasts derived from normal and malignant breast tissue. TNFα (2.5–10.0 ng/ml), in the presence of stripped fetal calf serum and dexamethasone, significantly stimulated fibroblast aromatase activity in a dose-dependent manner. IL-1 and IL-6 also stimulated fibroblast aromatase activity, but no marked synergism between TNFα and IL-1 or IL-6 was detected. Using a specific radioimmunoassay, significant concentrations of TNFα were detected in samples of breast cyst fluid and breast tumor cytosol, which had previously been shown to stimulate aromatase activity, but not in conditioned medium from breast tumor-derived fibroblasts. As TNFα may be preferentially expressed and produced in the adipose tissue component of the breast, this cytokine may have an important role in regulating estrogen synthesis in normal and malignant breast tissues.