Hormonal treatment with sex steroids in women is associated with lower p105 serum concentrations

Background: In breast and ovarian cancer patients elevated serum levels of the oncoprotein p105 were detected. We examined the influence of endocrine factors on the p105 serum concentration. Materials and Methods: The sera of 115 and non-pregnant women were analysed. Of the premenopausal women (n = 77) hormonal contraception was used by 30 women, and of the postmenopausal women (n =33) there were 15 women using hormonal replacement therapy (HRT). The serum specimens were analysed by ELISA. Results: Women with hormonal contraception had significantly lower serum levels than premenospausal controls (82-138 fmol/ml, median 109 fmol/ml vs. 103-183 fmol/ml, median 130 fmol/ml; P<0.001). In postmenopausal women with HRT serum levels were significantly lower than in postmenopausal controls (88-136 fmol/ml, median 117 fmol/ml vs. 99-261 fmol/ml, median 148 fmol/ml; P<0.001). Conclusions: Sex steroids seem to modulate c-erbB-2 activity. These results are important with regard to clinical studies on p105 oncoprotein in cancer patients.