Recent studies suggest estradiol (E₂)/natural progesterone (P) confers less breast cancer risk compared with conjugated equine estrogens (CEE)/synthetic progestogens. We investigate if differences in the regulation of breast cancer-related gene expression could provide some explanation. This study is a subset of a monocentric, 2-way, open observer-blinded, phase 4 randomized controlled trial on healthy postmenopausal women with climacteric symptoms (ClinicalTrials.gov; EUCTR-2005/001016-51). Study medication was two 28-day cycles of sequential hormone treatment with oral 0.625 mg CEE and 5 mg of oral medroxyprogesterone acetate (MPA) or 1.5 mg E₂ as percutaneous gel/day with the addition of 200 mg oral micronized P. MPA and P were added days 15–28/cycle. Material from two core-needle breast biopsies in 15 women in each group was subject to quantitative PCR (Q-PCR). The primary endpoint was a change in breast carcinoma development gene expression. In the first eight consecutive women, RNA was extracted at baseline and after two months of treatment and subjected to microarray for 28856 genes and Ingenuity Pathways Analysis (IPA) to identify risk factor genes. Microarray analysis showed 3272 genes regulated with a fold-change of >±1.4. IPA showed 225 genes belonging to mammary-tumor development function: 198 for CEE/MPA vs. 34 for E₂/P. Sixteen genes involved in mammary tumor inclination were subject to Q-PCR, inclining the CEE/MPA group towards an increased risk for breast carcinoma compared to the E₂/P group at a very high significance level (p = 3.1 × 10⁻⁸, z-score 1.94). The combination of E₂/P affected breast cancer-related genes much less than CEE/MPA.

Background: Androgens, notably testosterone inhibit breast cell proliferation and negative correlations between free testosterone (fT) and breast cell proliferation as well as mammographic density have been described. Dehydroepiandrosterone (DHEA) is reported to be a partial androgen antagonist in breast tumor cells in vitro. Our aim was to investigate if circulating DHEA had any effects on the association between circulating fT and mammographic density in vivo in the normal postmenopausal breast. Methods: We measured visual and digitized mammographic density and serum DHEA, testosterone, sex-hormone-binding globulin and calculated fT in 84 healthy untreated postmenopausal women. Results: Significant negative correlations between fT and both visual and digitized mammographic density were strengthened when the median DHEA level decreased from 10.2 to 8.6 nmol/L. Thereafter, correlations became weaker again probably due to decreasing fT levels and/or sample size. There were no correlations between mammographic density and DHEA, at any of the DHEA concentration ranges studied. Serum levels of fT and DHEA were positively correlated. Conclusion: Our findings demonstrate that circulating DHEA and/or its metabolites counteract the inhibitory action of fT on mammographic breast density.

Background: The impact of hormones on the development of breast cancer is despite extensive studies, incompletely understood. Combined estrogen-progestogen treatment augments the risk for breast cancer beyond that of estrogen alone, according to numerous studies. The role of breast cell proliferation as a promoter in the development and growth of breast cancer is well recognized. Materials and methods: Seventy-nine patients from three randomised trials were subject to a re-analysis of breast cell proliferation: (1) 22 women received continuous combined treatment with oral estradiol (E2) 2 mg/norethisterone acetate (NETA) 1 mg once daily for 3 months. (2) Thirty-seven women received 2 months of sequential treatment with oral conjugated equine estrogens (CEE) 0.625 mg daily combined with medroxyprogesterone acetate (MPA) 5 mg for 14/28 days of each cycle. (3) Twenty women received oral estradiol-valerate (E2V) 2 mg daily combined with levonorgestrel (LNG) intrauterine system (IUS), 20 μg/24 h for 2 months. Fine needle aspiration (FNA) (studies 1 and 3) and core needle biopsy (CNB) (study 2) were used for the assessment of breast cell proliferation. Results: There were no baseline proliferation differences, but at the end of treatment there was a highly significant between-group difference for E2V/LNG IUS versus the other two groups (p = 0.0025). E2/NETA and CEE treatments gave a 4–7-old increase in proliferation during treatment (p = 0.04) and (p = 0.007), respectively, which was absent in the E2V/LNG group, showing a significant correlation with insulin-like growth factor binding protein-3 (IGFBP-3) serum levels. Conclusion: E2V in combination with very low serum concentrations of LNG in the IUS gives no increase in proliferation in the normal breast.

Article Kjell Carlström (1940–2018) was published on July 1, 2018 in the journal Hormone Molecular Biology and Clinical Investigation (volume 35, issue 1).