Proliferation of breast epithelial cells in healthy women during the menstrual cycle

mTOR inhibition abrogates human mammary stem cells and early breast cancer progression markers

BACKGROUND

Mammary physiology is distinguished in containing adult stem/progenitor cells that are actively amending the breast tissue throughout the reproductive lifespan of women. Despite their importance in both mammary gland development, physiological maintenance, and reproduction, the exact role of mammary stem/progenitor cells in mammary tumorigenesis has not been fully elucidated in humans or animal models. The implications of modulating adult stem/progenitor cells in women could lead to a better understanding of not only their function, but also toward possible breast cancer prevention led us to evaluate the efficacy of rapamycin in reducing mammary stem/progenitor cell activity and malignant progression markers.

METHODS

We analyzed a large number of human breast tissues for their basal and luminal cell composition with flow cytometry and their stem and progenitor cell function with sphere formation assay with respect to age and menopausal status in connection with a clinical study (NCT02642094) involving a low-dose (2 mg/day) and short-term (5-7 days) treatment of the mTOR inhibitor sirolimus. The expression of biomarkers in biopsies and surgical breast samples were measured with quantitative analysis of immunohistochemistry.

RESULTS

Sirolimus treatment significantly abrogated mammary stem cell activity, particularly in postmenopausal patients. It did not affect the frequency of luminal progenitors but decreased their self-renewal capacity. While sirolimus had no effect on basal cell population, it decreased luminal cell population, particularly in postmenopausal patients. It also significantly diminished prognostic biomarkers associated with breast cancer progression from ductal carcinoma in situ to invasive breast cancer including p16INK4A, COX-2, and Ki67, as well as markers of the senescence-associated secretary phenotype, thereby possibly functioning in preventing early breast cancer progression.

CONCLUSION

Overall, these findings indicate a link from mTOR signaling to mammary stem and progenitor cell activity and cancer progression. Trial registration This study involves a clinical trial registered under the ClinicalTrials.gov identifier NCT02642094 registered December 30, 2015.

Incessant ovulation: a review of its importance in predicting cancer risk

Estrous cycles are recurring changes in therian mammals induced by estrogen, progesterone, and other hormones culminating in endometrial proliferation, ovulation, and implantation if fertilization occurred. In women, the estrous cycle is the menstrual cycle; but, unlike most mammals, the end of an infertile cycle is marked by endometrial sloughing and the start of another without an anestrous phase. Women stop cycling at menopause, while in most mammals, cycles continue until death. Epidemiologic studies identified menarche, menopause, births, lactation, and oral contraceptive (OC) use as key risk factors for ovarian, breast, and endometrial cancers. A composite variable was created to estimate the number of cycles not interrupted by events that stop ovulation. Captured by the phrase "incessant ovulation", repetitive cycles were first postulated to affect ovarian cancer risk and later extended to breast and endometrial cancers. These associations could be explained by cumulative effects of repetitive tissue changes within reproductive organs, immune consequences of repetitive ovulation through the glycoprotein mucin 1, and residual effects of past ovulations that enhance ovarian production of testosterone. The latter two pathways could affect the risk for cancers in other organs not considered "reproductive".

Cell type and stage specific transcriptional, chromatin and cell-cell communication landscapes in the mammary gland

The mammary gland (MG) is composed of three main epithelial lineages, the basal cells (BC), the estrogen receptor (ER) positive luminal cells (ER+ LC), and the ER negative LC (ER- LC). Defining the cell identity of each lineage and how it is modulated throughout the different stages of life is important to understand how these cells function and communicate throughout life. Here, we used transgenic mice specifically labelling ER+ LC combined to cell surface markers to isolate with high purity the 3 distinct cell lineages of the mammary gland and defined their expression profiles and chromatin landscapes by performing bulk RNAseq and ATACseq of these isolated populations in puberty, adulthood and mid-pregnancy. Our analysis identified conserved genes, ligands and transcription factor (TF) associated with a specific lineage throughout life as well as genes, ligands and TFs specific for a particular stage of the MG. In summary, our study identified genes and TF network associated with the identity, function and cell-cell communication of the different epithelial lineages of the MG at different stages of life.

Mapping hormone-regulated cell-cell interaction networks in the human breast at single-cell resolution

The rise and fall of estrogen and progesterone across menstrual cycles and during pregnancy regulates breast development and modifies cancer risk. How these hormones impact each cell type in the breast remains poorly understood because they act indirectly through paracrine networks. Using single-cell analysis of premenopausal breast tissue, we reveal a network of coordinated transcriptional programs representing the tissue-level response to changing hormone levels. Our computational approach, DECIPHER-seq, leverages person-to-person variability in breast composition and cell state to uncover programs that co-vary across individuals. We use differences in cell-type proportions to infer a subset of programs that arise from direct cell-cell interactions regulated by hormones. Further, we demonstrate that prior pregnancy and obesity modify hormone responsiveness through distinct mechanisms: obesity reduces the proportion of hormone-responsive cells, whereas pregnancy dampens the direct response of these cells to hormones. Together, these results provide a comprehensive map of the cycling human breast.

Modulation of Secondary Cancer Risks from Radiation Exposure by Sex, Age and Gonadal Hormone Status: Progress, Opportunities and Challenges

Available data on cancer secondary to ionizing radiation consistently show an excess (2-fold amount) of radiation-attributable solid tumors in women relative to men. This excess risk varies by organ and age, with the largest sex differences (6- to more than 10-fold) found in female thyroid and breasts exposed between birth until menopause (~50 years old) relative to age-matched males. Studies in humans and animals also show large changes in cell proliferation rates, radiotracer accumulation and target density in female reproductive organs, breast, thyroid and brain in conjunction with physiological changes in gonadal hormones during the menstrual cycle, puberty, lactation and menopause. These sex differences and hormonal effects present challenges as well as opportunities to personalize radiation-based treatment and diagnostic paradigms so as to optimize the risk/benefit ratios in radiation-based cancer therapy and diagnosis. Specifically, Targeted Radionuclide Therapy (TRT) is a fast-expanding cancer treatment modality utilizing radiopharmaceuticals with high avidity to specific molecular tumor markers, many of which are influenced by sex and gonadal hormone status. However, past and present dosimetry studies of TRT agents do not stratify results by sex and hormonal environment. We conclude that cancer management using ionizing radiation should be personalized and informed by the patient sex, age and hormonal status.

The progesterone-receptor modulator, ulipristal acetate, drastically lowers breast cell proliferation

PURPOSE

The proliferation of breast epithelial cells increases during the luteal phase of the menstrual cycle, when they are exposed to progesterone, suggesting that ulipristal acetate, a selective progestin-receptor modulator (SPRM), may reduce breast cell proliferation with potential use in breast cancer chemoprevention.

METHODS

Women aged 18-39 were randomized 1:1 to ulipristal 10-mg daily or to a combination oral contraceptive (COC) for 84 days. Participants underwent a breast biopsy and breast MRI at baseline and at end of study treatment. Proliferation of breast TDLU cells was evaluated by Ki67 immunohistochemical stain. We evaluated the breast MRIs for background parenchymal enhancement (BPE). All slides and images were masked for outcome evaluation.

RESULTS

Twenty-eight treatment-compliant participants completed the study; 25 of whom had evaluable Ki67 results at baseline and on-treatment. From baseline to end of treatment, Ki67 % positivity (Ki67%+) decreased a median of 84% in the ulipristal group (N = 13; 2-sided p (2p) = 0.040) versus a median increase of 8% in the COC group (N = 12; 2p = 0.85). Median BPE scores decreased from 3 to 1 in the ulipristal group (p = 0.008) and did not decrease in the COC group.

CONCLUSION

Ulipristal was associated with a major decrease in Ki67%+ and BPE. Ulipristal would warrant further investigation for breast cancer chemoprevention were it not for concerns about its liver toxicity. Novel SPRMs without liver toxicity could provide a new approach to breast cancer chemoprevention.

TRIAL REGISTRATION

NCT02922127, 4 October 2016.

[Non-genetic indications for risk reducing mastectomies: Guidelines of the National College of French Gynecologists and Obstetricians (CNGOF)]

OBJECTIVE

To determine the value of performing a risk-reducting mastectomy (RRM) in the absence of a deleterious variant of a breast cancer susceptibility gene, in 4 clinical situations at risk of breast cancer.

DESIGN

The CNGOF Commission of Senology, composed of 26 experts, developed these recommendations. A policy of declaration and monitoring of links of interest was applied throughout the process of making the recommendations. Similarly, the development of these recommendations did not benefit from any funding from a company marketing a health product. The Commission of Senology adhered to the AGREE II (Advancing guideline development, reporting and evaluation in healthcare) criteria and followed the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method to assess the quality of the evidence on which the recommendations were based. The potential drawbacks of making recommendations in the presence of poor quality or insufficient evidence were highlighted.

METHODS

The Commission of Senology considered 8 questions on 4 topics, focusing on histological, familial (no identified genetic abnormality), radiological (of unrecognized cancer), and radiation (history of Hodgkin's disease) risk. For each situation, it was determined whether performing RRM compared with surveillance would decrease the risk of developing breast cancer and/or increase survival.

RESULTS

The Commission of Senology synthesis and application of the GRADE method resulted in 11 recommendations, 6 with a high level of evidence (GRADE 1±) and 5 with a low level of evidence (GRADE 2±).

CONCLUSION

There was significant agreement among the Commission of Senology members on recommendations to improve practice for performing or not performing RRM in the clinical setting.

MR Elastography of the Breast: Evolution of Technique, Case Examples, and Future Directions

Recognizing that breast cancers present as firm, stiff lesions, the foundation of breast magnetic resonance elastography (MRE) is to combine tissue stiffness parameters with sensitive breast MR contrast-enhanced imaging. Breast MRE is a non-ionizing, cross-sectional MR imaging technique that provides for quantitative viscoelastic properties, including tissue stiffness, elasticity, and viscosity, of breast tissues. Currently, the technique continues to evolve as research surrounding the use of MRE in breast tissue is still developing. In the setting of a newly diagnosed cancer, associated desmoplasia, stiffening of the surrounding stroma, and necrosis are known to be prognostic factors that can add diagnostic information to patient treatment algorithms. In fact, mechanical properties of the tissue might also influence breast cancer risk. For these reasons, exploration of breast MRE has great clinical value. In this review, we will: (1) address the evolution of the various MRE techniques; (2) provide a brief overview of the current clinical studies in breast MRE with interspersed case examples; and (3) suggest directions for future research.

Progestogen addition with low-dose levonorgestrel intrauterine system in menopausal hormone treatment gives less normal breast tissue proliferation than oral norethisterone acetate or medroxyprogesterone acetate

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.

Role of the Microenvironment in Regulating Normal and Cancer Stem Cell Activity: Implications for Breast Cancer Progression and Therapy Response

The epithelial cells in an adult woman’s breast tissue are continuously replaced throughout their reproductive life during pregnancy and estrus cycles. Such extensive epithelial cell turnover is governed by the primitive mammary stem cells (MaSCs) that proliferate and differentiate into bipotential and lineage-restricted progenitors that ultimately generate the mature breast epithelial cells. These cellular processes are orchestrated by tightly-regulated paracrine signals and crosstalk between breast epithelial cells and their tissue microenvironment. However, current evidence suggests that alterations to the communication between MaSCs, epithelial progenitors and their microenvironment plays an important role in breast carcinogenesis. In this article, we review the current knowledge regarding the role of the breast tissue microenvironment in regulating the special functions of normal and cancer stem cells. Understanding the crosstalk between MaSCs and their microenvironment will provide new insights into how an altered breast tissue microenvironment could contribute to breast cancer development, progression and therapy response and the implications of this for the development of novel therapeutic strategies to target cancer stem cells.

Mechanisms for estrogen receptor expression in human cancer

Estrogen is a steroid hormone that has critical roles in reproductive development, bone homeostasis, cardiovascular remodeling and brain functions. However, estrogen also promotes mammary, ovarian and endometrial tumorigenesis. Estrogen antagonists and drugs that reduce estrogen biosynthesis have become highly successful therapeutic agents for breast cancer patients. The effects of estrogen are largely mediated by estrogen receptor (ER) α and ERβ, which are members of the nuclear receptor superfamily of transcription factors. The mechanisms underlying the aberrant expression of ER in breast cancer and other types of human tumors are complex, involving considerable alternative splicing of ERα and ERβ, transcription factors, epigenetic and post-transcriptional regulation of ER expression. Elucidation of mechanisms for ER expression may not only help understand cancer progression and evolution, but also shed light on overcoming endocrine therapy resistance. Herein, we review the complex mechanisms for regulating ER expression in human cancer.

Estrogen and progesterone signalling in the normal breast and its implications for cancer development

The ovarian hormones estrogen and progesterone are master regulators of the development and function of a broad spectrum of human tissues, including the breast, reproductive and cardiovascular systems, brain and bone. Acting through the nuclear estrogen (ER) and progesterone receptors (PR), both play complex and essential coordinated roles in the extensive development of the lobular alveolar epithelial structures of the normal breast during puberty, the normal menstrual cycle and pregnancy. The past decade has seen major advances in understanding the mechanisms of action of estrogen and progesterone in the normal breast and in the delineation of the complex hierarchy of cell types regulated by ovarian hormones in this tissue. There is evidence for a role for both ER and PR in driving breast cancer, and both are favourable prognostic markers with respect to outcome. In this review, we summarize current knowledge of the mechanisms of action of ER and PR in the normal breast, and implications for the development and management of breast cancer.

Suppression of Unspecific Enhancement on Breast Magnetic Resonance Imaging (Mri) by Antiestrogen Medication

Aims and Background

The value of breast MRI may be impaired by unspecific enhancement. This may leave patients with difficult-to-assess breast tissue with an uncertain diagnosis. We examined whether this unspecific enhancement (which is mostly due to proliferative or hyperplastic changes of benign breast tissue) may be suppressed by antiestrogen medication.

Methods

In a trial of treatment, 10 peri- or postmenopausal patients who exhibited diffuse and/or focal enhancement on breast MRI before tamoxifen medication agreed to undergo a short-term tamoxifen treatment. MRI monitoring was performed 2, 4 and 8 weeks after onset of antiestrogen therapy (tamoxifen, 30 mg per day).

Results

Six patients showed a significant decrease of enhancement. Unchanged (n = 3) or increased (n = 1) enhancement was seen in 4 patients. One of the three patients with unchanged enhancement proved to have diffuse lobular carcinoma in situ.

Conclusions

Part of the unspecific enhancement seen on breast MRI can probably be suppressed by short-term antiestrogen medication.

Hormone replacement therapy, mammographic density, and breast cancer risk: a cohort study

Purpose

Hormone replacement therapy (HRT) use increases breast cancer risk and mammographic density (MD). We examine whether MD mediates or modifies the association of HRT with the breast cancer.

Methods

For the 4,501 participants in the Danish diet, cancer and health cohort (1993–1997) who attended mammographic screening in Copenhagen (1993–2001), MD (mixed/dense or fatty) was assessed at the first screening after cohort entry. HRT use was assessed by questionnaire and breast cancer diagnoses until 2012 obtained from the Danish cancer registry. The associations of HRT with MD and with breast cancer were analyzed separately using Cox’s regression. Mediation analyses were used to estimate proportion [with 95% confidence intervals (CI)] of an association between HRT and breast cancer mediated by MD.

Results

2,444 (54.3%) women had mixed/dense breasts, 229 (5.4%) developed breast cancer, and 35.9% were current HRT users at enrollment. Compared to never users, current HRT use was statistically significantly associated with having mixed/dense breasts (relative risk and 95% CI 1.24; 1.14–1.35), and higher risk of breast cancer (hazard ratio 1.87; 1.40–2.48). Association between current HRT use and breast cancer risk was partially mediated by MD (percent mediated = 10%; 95% CI 4–22%). The current HRT use-related breast cancer risk was higher in women with mixed/dense (1.94; 1.37–3.87) than fatty (1.37; 0.80–2.35) breasts (p value for interaction = 0.15).

Conclusions

MD partially mediates some of the association between HRT and breast cancer risk. The association between HRT and breast cancer seems to be stronger in women with dense breasts.

Dissecting the Biology of Menstrual Cycle-Associated Breast Cancer Risk

Fluctuations in circulating estrogen and progesterone across the menstrual cycle lead to increased breast cancer susceptibility in women; however, the biological basis for this increased risk is not well understood. Estrogen and progesterone have important roles in normal mammary gland development, where they direct dynamic interactions among the hormonally regulated mammary epithelial, stromal, and immune cell compartments. The continuous fluctuations of estrogen and progesterone over a woman’s reproductive lifetime affect the turnover of mammary epithelium, stem cells, and the extracellular matrix, as well as regulate the phenotype and function of mammary stromal and immune cells, including macrophages and regulatory T cells. Collectively, these events may result in genome instability, increase the chance of random genetic mutations, dampen immune surveillance, and promote tolerance in the mammary gland, and thereby increase the risk of breast cancer initiation. This article reviews the current status of our understanding of the molecular and the cellular changes that occur in the mammary gland across the menstrual cycle and how continuous menstrual cycling may increase breast cancer susceptibility in women.

Timing of breast cancer surgery, menstrual phase, and prognosis: Systematic review and meta-analysis

BACKGROUND

For over 25 years, there has been a debate revolving around the timing of breast cancer surgery, menstrual cycle, and prognosis.

METHODS

This systematic review synthesizes and evaluates the body of evidence in an effort to inform evidence-based practice. A keyword and reference search was performed in PubMed and Web of Science to identify human studies that met the inclusion criteria. A total of 58 studies (48 international and 10 U.S.-based) were identified. We provided a narrative summary on study findings and conducted a meta-analysis on a subset of studies where quantitative information was available.

RESULTS

Findings from both qualitative and quantitative analyses were inconclusive regarding performing breast cancer surgery around a specific phase of the menstrual cycle.

CONCLUSION

Based on the Institute of Medicine criteria, evidence is insufficient to recommend a change in current primary breast cancer surgery practice based on menstrual phase.

Incorporating Biomarkers in Studies of Chemoprevention

Despite Food and Drug Administration approval of tamoxifen and raloxifene for breast cancer risk reduction and endorsement by multiple agencies, uptake of these drugs for primary prevention in the United States is only 4% for risk eligible women likely to benefit from their use. Side effects coupled with incomplete efficacy and lack of a survival advantage are the likely reasons. This disappointing uptake, after the considerable effort and expense of large Phase III cancer incidence trials required for approval, suggests that a new paradigm is required. Current prevention research is focused on (1) refining risk prediction, (2) exploring behavioral and natural product interventions, and (3) utilizing novel translational trial designs for efficacy. Risk biomarkers will play a central role in refining risk estimates from traditional models and selecting cohorts for prevention trials. Modifiable risk markers called surrogate endpoint or response biomarkers will continue to be used in Phase I and II prevention trials to determine optimal dose or exposure and likely effectiveness from an intervention. The majority of Phase II trials will continue to assess benign breast tissue for response and mechanism of action biomarkers. Co-trials are those in which human and animal cohorts receive the same effective dose and the same tissue biomarkers are assessed for modulation due to the intervention, but then additional animals are allowed to progress to cancer development. These collaborations linking biomarker modulation and cancer prevention may obviate the need for cancer incidence trials for non-prescription interventions.

Reprint of "Use of medroxyprogesterone acetate for hormone therapy in postmenopausal women: Is it safe?"

Medroxyprogesterone acetate (MPA) has been in clinical use for over 30 years, and was generally considered to be safe until the results of long-term studies of postmenopausal hormone therapy (HT) using treatment with conjugated equine estrogens (CEE) combined with MPA and CEE alone suggested that MPA, and perhaps other progestogens, may play a role in the increased risk of breast cancer and cardiovascular diseases. This review examines critically the safety of MPA in terms of breast cancer and cardiovascular disease risk, and its effects on brain function. Research into mechanisms by which MPA might cause adverse effects in these areas, combined with the available clinical evidence, suggests a small increase in relative risk for breast cancer and stroke, and a decline in cognitive function, in older women using MPA with an estrogen for postmenopausal HT. However, short-term (less than 5 years) use of MPA with an estrogen in the years immediately after the onset of menopause for the management of vasomotor symptoms does not appear to be associated with any increased risk of these disorders.

Estrogen regulates luminal progenitor cell differentiation through H19 gene expression

Although the role of estrogen signaling in breast cancer development has been extensively studied, the mechanisms that regulate the indispensable role of estrogen in normal mammary gland development have not been well studied. Because of the unavailability of culture system to maintain estrogen-receptor-positive (ERα(+)) cells in vitro, the molecular mechanisms that regulate estrogen/ERα signaling in the normal human breast are unknown. In the present study, we examined the effects of estrogen signaling on ERα(+) human luminal progenitors using a modified matrigel assay and found that estrogen signaling increased the expansion potential of these progenitors. Furthermore, we found that blocking ERα attenuated luminal progenitor expansion and decreased the luminal colony-forming potential of these progenitors. Additionally, blocking ERα decreased H19 expression in the luminal progenitors and led to the development of smaller luminal colonies. We further showed that knocking down the H19 gene in the luminal progenitors significantly decreased the colony-forming potential of the luminal progenitors, and this phenotype could not be rescued by the addition of estrogen. Lastly, we explored the clinical relevance of the estrogen-H19 signaling axis in breast tumors and found that ERα(+) tumors exhibited a higher expression of H19 as compared with ERα(-) tumors and that H19 expression showed a positive correlation with ERα expression in those tumors. Taken together, the present results indicate that the estrogen-ERα-H19 signaling axis plays a role in regulating the proliferation and differentiation potentials of the normal luminal progenitors and that this signaling network may also be important in the development of ER(+) breast cancer tumors.

Prognostic effect of menstrual cycle on timing of surgery in premenopausal breast cancer patients

BACKGROUND

It is controversial whether surgery during different menstrual phases (a kind of host milieu may influence biological characteristics of micrometastatic foci) affects clinical outcomes.

METHODS

Survival outcomes were compared between patients who underwent surgery during the follicular (cycle days 1 to 14) and luteal (days 15 to 31) phases. A range of cutoff days from day 10 to 22 was used to observe the risk trend.

RESULTS

The follicular phase was associated with a more favorable prognosis than the luteal phase in disease-free survival (DFS) [hazard ratio (HR) .318, 95% confidence interval (CI) .10 to .99, P = .049] and overall survival (OS) (HR .260, 95% CI .07 to .92, P = .036). Similar results were detected when the cutoff day was set at days 14, 18, and 19 in DFS and days 11, 13, and 14 in OS. A low HR flat fluctuation was observed from cutoff days 10 to 22, and the risk went up thereafter for both DFS and OS.

CONCLUSION

Surgery performed during the follicular phase provides a more favorable prognosis compared with the luteal phase.

Hormonal regulation of the immune microenvironment in the mammary gland

It is well established that the development and homeostasis of the mammary gland are highly dependent upon the actions of ovarian hormones progesterone and estrogen, as well as the availability of prolactin for the pregnant and lactating gland. More recently it has become apparent that immune system cells and cytokines play essential roles in both mammary gland development as well as breast cancer. Here, we review hormonal effects on mammary gland biology during puberty, menstrual cycling, pregnancy, lactation and involution, and dissect how hormonal control of the immune system may contribute to mammary development at each stage via cytokine secretion and recruitment of macrophages, eosinophils, mast cells and lymphocytes. Collectively, these alterations may create an immunotolerant or inflammatory immune environment at specific developmental stages or phases of the menstrual cycle. Of particular interest for further research is investigation of the combinatorial actions of progesterone and estrogen during the luteal phase of the menstrual cycle and key developmental points where the immune system may play an active role both in mammary development as well as in the creation of an immunotolerant environment, thereby affecting breast cancer risk.

Use of medroxyprogesterone acetate for hormone therapy in postmenopausal women: is it safe?

Medroxyprogesterone acetate (MPA) has been in clinical use for over 30 years, and was generally considered to be safe until the results of long-term studies of postmenopausal hormone therapy (HT) using treatment with conjugated equine estrogens (CEE) combined with MPA and CEE alone suggested that MPA, and perhaps other progestogens, may play a role in the increased risk of breast cancer and cardiovascular diseases. This review examines critically the safety of MPA in terms of breast cancer and cardiovascular disease risk, and its effects on brain function. Research into mechanisms by which MPA might cause adverse effects in these areas, combined with the available clinical evidence, suggests a small increase in relative risk for breast cancer and stroke, and a decline in cognitive function, in older women using MPA with an estrogen for postmenopausal HT. However, short-term (less than 5 years) use of MPA with an estrogen in the years immediately after the onset of menopause for the management of vasomotor symptoms does not appear to be associated with any increased risk of these disorders.

Circulating concentrations of insulin-like growth factor-I, insulin-like growth factor-binding protein-3, genetic polymorphisms and mammographic density in premenopausal Mexican women: results from the ESMaestras cohort

The insulin-like growth factor (IGF) axis plays an essential role in the development of the mammary gland. High circulating levels of IGF-I and of its major binding protein IGFBP3 have been related with increased mammographic density in Caucasian premenopausal women. Some common single nucleotide polymorphisms (SNPs) in genes of the IGF pathway have also been suggested to play a role in mammographic density. We conducted a cross-sectional study nested within the large Mexican ESMaestras cohort to investigate the relation between circulating levels of IGF-I, IGFBP-3, the IGF-I/IGFBP-3 ratio, five common SNPs in the IGF-1, IGFBP-3 and IGF-1R genes and mammographic density in 593 premenopausal Mexican women. Mean age at mammogram was 43.1 (standard deviation, SD = 3.7) years, and average body mass index (BMI) at recruitment was 28.5 kg/m(2). Mean percent mammographic density was 36.5% (SD: 17.1), with mean dense tissue area of 48.3 (SD: 33.3) cm(2) . Mean IGF-I and IGFBP-3 concentrations were 15.33 (SD: 5.52) nmol/l and 114.96 (SD: 21.34) nmol/l, respectively. No significant associations were seen between percent density and biomarker concentrations, but women with higher IGF-I and IGF-I/IGFBP-3 concentrations had lower absolute dense (p(trend) = 0.03 and 0.09, respectively) and nondense tissue areas (p(trend) < 0.001 for both parameters). However, these associations were null after adjustment by BMI. SNPs in specific genes were associated with circulating levels of growth factors, but not with mammographic density features. These results do not support the hypothesis of a strong association between circulating levels of growth hormones and mammographic density in Mexican premenopausal women.

Updates and revisions to the BI-RADS magnetic resonance imaging lexicon

This article summarizes the updates and revisions to the second edition of the BI-RADS MRI lexicon. A new feature in the lexicon is background parenchymal enhancement and its descriptors. Another major focus is on revised terminology for masses and non-mass enhancement. A section on breast implants and associated lexicon terms has also been added. Because diagnostic breast imaging increasingly includes multimodality evaluation, the new edition of the lexicon also contains revised recommendations for combined reporting with mammography and ultrasound if these modalities are included as comparison, and clarification on the use of final assessment categories in MR imaging.

Percutaneous estradiol/oral micronized progesterone has less-adverse effects and different gene regulations than oral conjugated equine estrogens/medroxyprogesterone acetate in the breasts of healthy women in vivo

Gene expression analysis of healthy postmenopausal women in a prospective clinical study indicated that genes encoding for epithelial proliferation markers Ki-67 and progesterone receptor B mRNA are differentially expressed in women using hormone therapy (HT) with natural versus synthetic estrogens. Two 28-day cycles of daily estradiol (E2) gel 1.5 mg and oral micronized progesterone (P) 200 mg/day for the last 14 days of each cycle did not significantly increase breast epithelial proliferation (Ki-67 MIB-1 positive cells) at the cell level nor at the mRNA level (MKI-67 gene). A borderline significant beneficial reduction in anti-apoptotic protein bcl-2, favouring apoptosis, was also seen followed by a slight numeric decrease of its mRNA. By contrast, two 28-day cycles of daily oral conjugated equine estrogens (CEE) 0.625 mg and oral medroxyprogesterone acetate (MPA) 5 mg for the last 14 days of each cycle significantly increased proliferation at both the cell level and at the mRNA level, and significantly enhanced mammographic breast density, an important risk factor for breast cancer. In addition, CEE/MPA affected around 2,500 genes compared with just 600 affected by E2/P. These results suggest that HT with natural estrogens affects a much smaller number of genes and has less-adverse effects on the normal breast in vivo than conventional, synthetic therapy.

Alterations in mast cell frequency and relationship to angiogenesis in the rat mammary gland during windows of physiologic tissue remodeling

BACKGROUND

The mammary epithelium undergoes proliferation and regression accompanied by remodeling of the fibrocellular and vascular stroma. Mast cells are abundant in these compartments and have been implicated in remodeling during wound healing and cancer progression. The purpose of this study was to test the hypothesis that mast cell abundance correlates with physiologic mammary tissue remodeling during estrous cycling, lactogenesis (pregnancy and lactation) and involution.

RESULTS

Mast cell and capillary frequency were quantified in the stroma surrounding ducts and lobules from mammary glands of rats. During estrous cycling, periductal mast cell numbers were unchanged, but lobule-associated mast cells significantly increased in the regressive phase of diestrus II. During lactogenesis, lobular stroma mast cells peaked early in pregnancy, at D2, followed by a significant decrease throughout lactation. Involution was associated with a rapid return in mast cell numbers, similar to diestrus II. Lobular vascularization peaked during the state of metestrus, when limited secretory differentiation occurs. Lobular angiogenesis peaked at D7 of pregnancy, regressed, and then returned to high levels during lactation and early involution, when secretory differentiation is high.

CONCLUSIONS

These results suggest mast cells are predominantly associated with regressive lobular remodeling during cycling and involution, whereas angiogenesis is predominantly associated with secretory differentiation.

Ulipristal acetate does not impact human normal breast tissue

BACKGROUND

Antiprogestins are of growing interest for the development of new treatments in the gynecological field. Ulipristal acetate (UPA) is a progesterone receptor (PR) modulator considered for long-term administration in contraception and is currently being registered for the treatment of uterine fibroids. In light of the influences of hormonal dysfunction in breast pathologies, the secondary consequences of chronic UPA therapy need to be established. The aim of this study was to determine UPA actions mediated by PR and glucocorticoid receptor (GR) in normal and transformed breast.

METHODS

UPA, progesterone (P) and dexamethasone (DEX) effects were observed on PR and GR responsive genes and on proliferation and apoptosis of normal human breast epithelial (HBE) and breast cancer cells. Human normal breast tissue samples were xenografted in athymic mice and treated with estradiol (E2), or E2 + P, or E2 + P + UPA.

RESULTS

Analysis of PR and GR reporter gene transactivation and their respective endogenous target genes indicated that UPA exerted anti-progestational and anti-glucocorticoid activity in both types of cells with a more pronounced effect in cancer cells. When combined with P or DEX, UPA limits the proliferation of HBE cells but increases growth in breast cancer cell lines. UPA administration had no impact on the mitotic index on xenografted human breast tissue exposed to gonadal hormones at similar concentrations to those present in normal women.

CONCLUSIONS

Although further clinical trials are required to confirm that the results from our experimental models can be extrapolated to women treated with UPA, they suggest that such treatment would not be deleterious to normal breast tissue at least for a cycle (28 days) of continuous administration.

Background parenchymal enhancement on breast MRI: impact on diagnostic performance

OBJECTIVE

Breast density is documented to reduce sensitivity and specificity of mammography. However, little is known regarding the effect of normal background parenchymal enhancement on accuracy of breast MRI. The purpose of this study was to evaluate the effect of background parenchymal enhancement on MRI diagnostic performance.

MATERIALS AND METHODS

A review of our established MRI data identified all women undergoing breast MRI from March 1, 2006, through June 30, 2007. Prospectively reported background parenchymal enhancement categories of minimal, mild, moderate, or marked (anticipated BI-RADS MRI lexicon definitions) and assessments were extracted from the database for each patient. Outcomes were determined by pathologic analysis, imaging, and linkage with the regional tumor registry with a minimum of 24 months of follow-up. Patients were dichotomized into categories of minimal or mild versus moderate or marked background parenchymal enhancement. Associations with patient age, abnormal interpretation rate, positive biopsy rate, cancer yield, sensitivity, and specificity were compared using chi-square and z score tests.

RESULTS

The study cohort included 736 women. Moderate or marked background parenchymal enhancement was significantly more frequent among patients younger than 50 years compared with those 50 years old and older (39.7% vs 18.9%; p < 0.0001). Moderate or marked background parenchymal enhancement was also associated with a higher abnormal interpretation rate compared with minimal or mild background parenchymal enhancement (30.5% vs 23.3%; p = 0.046). Positive biopsy rate, cancer yield, sensitivity, and specificity were not significantly different according to background parenchymal enhancement category.

CONCLUSION

Increased background parenchymal enhancement on breast MRI is associated with younger patient age and higher abnormal interpretation rate. However, it is not related to significant differences in positive biopsy rate, cancer yield, sensitivity, or specificity of MRI.

The biology of human breast epithelial progenitors

Current evidence suggests that similar to other tissues in the human body mammary epithelia cells are being maintained by the unique properties of stem cells, undifferentiated as well as lineage-restricted progenitors. Because of their longevity, proliferation and differentiation potentials these primitive breast epithelial cells are likely targets of transforming mutations that can cause them to act as cancer initiating cells. In this context, understanding the molecular mechanisms that regulate the normal functions of the human breast epithelial stem cells and progenitors and how alterations to these same mechanisms can confer a cancer stem cell phenotype on these rare cell populations is crucial to the development of new and more effective therapies again breast cancer. This review article will examine the current state of knowledge about the isolation and characterization of human breast epithelial progenitors and their relevance to breast cancer research.

Lowering oral contraceptive norethindrone dose increases estrogen and progesterone receptor levels with no reduction in proliferation of breast epithelium: a randomized trial

BACKGROUND

This study was conducted to compare breast epithelial-cell proliferation and estrogen and progesterone receptor levels in women taking one of two oral contraceptives (OCs) containing the same dose of estrogen but different doses of the progestin norethindrone (NET).

STUDY DESIGN

Thirty-three women were randomly assigned 1:1 to one of two OCs with 35-mcg ethinylestradiol (EE2) but different doses of NET - 1 or 0.4 mg. At the end of the active pill phase of the third OC cycle, a breast biopsy was performed and the percentages of epithelial cells of the terminal duct lobular units were measured for Ki67 (MIB1), progesterone receptors A and B (PRA and PRB, respectively), and estrogen receptor α (ERα).

RESULTS

The biopsies from 27 women had sufficient epithelium for analysis. The percentages of cells positive for PRA, PRB and ERα were approximately double with the lower progestin dose (PRA: p=.041; PRB: p=.030; ERα: p=.056). The Ki67 percentage was not reduced with the lower progestin dose (12.5% for 0.4-mg NET vs. 7.8% for 1.0-mg NET).

CONCLUSIONS

The increase in PRA-, PRB- and ERα-positive cells with the 60% lower progestin dose OC appears likely to account for its failure to decrease breast-cell proliferation. This breast-cell proliferation result is contrary to that predicted from the results of lowering the medroxyprogesterone acetate dose in menopausal hormone therapy.

Apigenin prevents development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats

The use of progestins as a component of hormone replacement therapy has been linked to an increase in breast cancer risk in postmenopausal women. We have previously shown that medroxyprogesterone acetate (MPA), a commonly administered synthetic progestin, increases production of the potent angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells, leading to the development of new blood vessels and tumor growth. We sought to identify nontoxic chemicals that would inhibit progestin-induced tumorigenesis. We used a recently developed progestin-dependent mammary cancer model in which tumors are induced in Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene (DMBA) treatment. The flavonoid apigenin, which we previously found to inhibit progestin-dependent VEGF synthesis in human breast cancer cells in vitro, significantly delayed the development of, and decreased the incidence and multiplicity of, MPA-accelerated DMBA-induced mammary tumors in this animal model. Whereas apigenin decreased the occurrence of such tumors, it did not block MPA-induced intraductal and lobular epithelial cell hyperplasia in the mammary tissue. Apigenin blocked MPA-dependent increases in VEGF, and suppressed VEGF receptor-2 (VEGFR-2) but not VEGFR-1 in regions of hyperplasia. No differences were observed in estrogen or progesterone receptor (ER/PR) levels, or the number of estrogen receptor-positive cells, within the mammary gland of MPA-treated animals administered apigenin, MPA-treated animals, and placebo treated animals. However, the number of progesterone receptor-positive cells was reduced in animals treated with MPA or MPA and apigenin compared with those treated with placebo. These findings suggest that apigenin has important chemopreventive properties for those breast cancers that develop in response to progestins.

Estrogen up-regulates ATBF1 transcription but causes its protein degradation in estrogen receptor-alpha-positive breast cancer cells

The proper level of estrogen-estrogen receptor (ER) signaling is important for the maintenance of epithelial homeostasis in the breast. In a previous study we demonstrated that ATBF1, which has been suggested as a tumor suppressor in breast cancer, inhibited estrogen-mediated cell proliferation by selectively competing with AIB1 for binding to the ER. However, the expression of ATBF1 mRNA was shown to positively correlate with ER in breast cancer specimens. We, therefore, examined whether estrogen regulates ATBF1. We demonstrated that estrogen up-regulated the transcription of ATBF1, which was mediated by the direct binding of the ER onto the ATBF1 promoter, and that a half-estrogen-responsive element in the ATBF1 promoter was essential for ER direct binding. Furthermore, we found that estrogen at lower levels increased, but at higher levels decreased the expression of ATBF1 protein, which involved the degradation of ATBF1 protein by the estrogen-responsive proteasome system. ATBF1 protein levels fluctuate with estrogen levels. Although lower levels of estrogen increased ATBF1 protein expression, ATBF1 still inhibited cell proliferation caused by lower levels of estrogen. These findings not only reveal an autoregulatory feedback loop between ATBF1 and estrogen-ER signaling but also suggest that ATBF1 plays a role in both the maintenance of breast epithelial homeostasis and breast tumorigenesis caused by elevated estrogen levels.

Background parenchymal enhancement on baseline screening breast MRI: impact on biopsy rate and short-interval follow-up

OBJECTIVE

Background parenchymal enhancement on breast MRI refers to normal enhancement of the patient's fibroglandular tissue. The aim of this study was to determine the effect of background parenchymal enhancement on short-interval follow-up, biopsy, and cancer detection rate on baseline screening MRI in a high-risk group.

MATERIALS AND METHODS

Two hundred fifty baseline high-risk screening MRI examinations were reviewed. For each, the background parenchymal enhancement pattern was recorded (minimal, ≤ 25%; mild, 26-50%; moderate, 51-75%; and marked, > 75%), as were BI-RADS category, biopsy rate, and final pathology result. Results were compared for each enhancement category.

RESULTS

Of the 250 MRI examinations, 24.8% showed minimal enhancement; 34%, mild; 24%, moderate; and 17.2%, marked enhancement. Women with minimal enhancement had a significantly higher number of BI-RADS categories 1 and 2 examinations (64.5%) than women with mild (38.8%), moderate (40%), or marked (25.6%) enhancement. The BI-RADS category 3 rate was 43.6% overall and was significantly lower for women with minimal enhancement (27.4% vs 47.1% for women with mild, 45.0% for women with moderate, and 58.1% for women with marked enhancement). At follow-up, 86.2% of the BI-RADS 3 lesions were converted to BI-RADS category 1 or 2 and 13.8% were converted to BI-RADS 4, with a malignancy rate of 0.9% for lesions undergoing short-interval follow-up. There was no significant difference in biopsy rate or cancer detection rate among enhancement categories.

CONCLUSION

Mild, moderate, and marked background parenchymal enhancement is associated with a significantly lower rate of BI-RADS categories 1 and 2 assessments and a significantly higher rate of BI-RADS category 3 assessments than minimal enhancement. There was no significant difference in biopsy rate or cancer detection rate among the enhancement categories.

Synthetic progestins induce growth and metastasis of BT-474 human breast cancer xenografts in nude mice

OBJECTIVE

Previous studies have shown that sequential exposure to estrogen and progesterone or medroxyprogesterone acetate (MPA) stimulates vascularization and promotes the progression of BT-474 and T47-D human breast cancer cell xenografts in nude mice (Liang et al, Cancer Res 2007, 67:9929). In this follow-up study, the effects of progesterone, MPA, norgestrel (N-EL), and norethindrone (N-ONE) on BT-474 xenograft tumors were compared in the context of several different hormonal environments. N-EL and N-ONE were included in the study because synthetic progestins vary considerably in their biological effects and the effects of these two progestins on the growth of human tumor xenografts are not known.

METHODS

Estradiol-supplemented intact and ovariectomized immunodeficient mice were implanted with BT-474 cells. Progestin pellets were implanted simultaneously with estradiol pellets either 2 days before tumor cell injection (ie, combined) or 5 days after tumor cell injections (ie, sequentially).

RESULTS

Progestins stimulated the growth of BT-474 xenograft tumors independent of exposure timing and protocol, MPA stimulated the growth of BT-474 xenograft tumors in ovariectomized mice, and progestins stimulated vascular endothelial growth factor elaboration and increased tumor vascularity. Progestins also increased lymph node metastasis of BT-474 cells. Therefore, progestins, including N-EL and N-ONE, induce the progression of breast cancer xenografts in nude mice and promote tumor metastasis.

CONCLUSIONS

These observations suggest that women who ingest progestins for hormone therapy or oral contraception could be more at risk for developing breast cancer because of proliferation of existing latent tumor cells. Such risks should be considered in the clinical setting.

The reproductive-cell cycle theory of aging: an update

The Reproductive-Cell Cycle Theory posits that the hormones that regulate reproduction act in an antagonistic pleiotrophic manner to control aging via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence. Since reproduction is the most important function of an organism from the perspective of the survival of the species, if reproductive-cell cycle signaling factors determine the rate of growth, determine the rate of development, determine the rate of reproduction, and determine the rate of senescence, then by definition they determine the rate of aging and thus lifespan. The theory is able to explain: 1) the simultaneous regulation of the rate of aging and reproduction as evidenced by the fact that environmental conditions and experimental interventions known to extend longevity are associated with decreased reproductive-cell cycle signaling factors, thereby slowing aging and preserving fertility in a hostile reproductive environment; 2) two phenomena that are closely related to species lifespan-the rate of growth and development and the ultimate size of the animal; 3). the apparent paradox that size is directly proportional to lifespan and inversely proportional to fertility between species but vice versa within a species; 4). how differing rates of reproduction between species is associated with differences in their lifespan; 5). why we develop aging-related diseases; and 6). an evolutionarily credible reason for why and how aging occurs-these hormones act in an antagonistic pleiotrophic manner via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence (dyosis). In essence, the Reproductive-Cell Cycle Theory can explain aging in all sexually reproductive life forms.

Oral contraceptive use and breast cancer: a prospective study of young women

BACKGROUND

Previous studies convincingly showed an increase in risk of breast cancer associated with current or recent use of oral contraceptives from the 1960s to 1980s. The relation of contemporary oral contraceptive formulations to breast cancer risk is less clear.

METHODS

We assessed lifetime oral contraceptive use and the specific formulations used among 116,608 female nurses ages 25 to 42 years at enrollment in 1989, and subsequently updated this information every 2 years. We related this information to risk of breast cancer up to June 1, 2001.

RESULTS

During 1,246,967 person-years of follow-up, 1,344 cases of invasive breast cancer were diagnosed. Past use of any oral contraceptive was not related to breast cancer risk [multivariate relative risk (RR), 1.12; 95% confidence interval 0.95-1.33]. Current use of any oral contraceptive was related to a marginally significant higher risk (multivariate RR, 1.33; 95% CI, 1.03-1.73). One specific formulation substantially accounted for the excess risk: the RR for current use of triphasic preparations with levonorgestrel as the progestin was 3.05 (95% CI, 2.00-4.66; P < 0.0001).

CONCLUSIONS

Current use of oral contraceptives carries an excess risk of breast cancer. Levonorgestrel used in triphasic preparations may account for much of this elevation in risk.

IMPACT

Different oral contraceptive formulations might convey different risks of breast cancer; ongoing monitoring of these associations is necessary as oral contraceptive formulations change.

Mechanisms for differential effects between natural progesterone and synthetic progestogens on normal breast tissue

Both epidemiological studies and experimental data on normal breast tissue suggest increased cancer risk, proliferation and mammographic breast density (MD) during hormone therapy (HT) containing synthetic progestogens in traditional doses, and the relative risk or RR is approximately 1.5–3 (for women treated vs. untreated with the above therapies), proliferation levels of normal breast epithelial cells of around 10% and increase in MD in up to around 50% of women during treatment. Dose-response relationships have been inferred by correlations between progestogens as levonorgestrel, norethisterone acetate and medroxyprogesterone acetate on the one hand and proliferation and/or MD on the other hand, and of indications of lower relative risk of breast cancer with modern low or ultra-low dose HT. In contrast, natural progesterone endogenously during the menstrual cycle has a weak effect and exogenous estrogen in combination with oral micronized progesterone in HT has shown to yield an indifferent effect on proliferation. Furthermore, in epidemiological studies such as the French E3N cohort, these combinations have not shown any risk increase for breast cancer for at least 5 years of treatment. Experimental data supporting or not supporting the view that the main proliferative mechanism for natural progesterone is through binding to its nascent progesterone receptors is discussed as well as the pros and cons that the non-physiological higher proliferation levels induced by synthetic progestogens is mainly mediated through interaction with potent growth factors and their paracrine and/or cell signaling pathways.

Progesterone stimulates mitochondrial activity with subsequent inhibition of apoptosis in MCF-10A benign breast epithelial cells

The effects of progesterone on breast epithelial cells remain poorly defined with observations showing both proliferative and antiproliferative effects. As an example, progesterone levels correlate with increased epithelial cell proliferation, but there is discordance between the dividing cells and the cells with nuclear progesterone receptor expression. The release of paracrine growth factors from nuclear receptor-positive cells has been postulated as a mechanism, since in vitro studies show a lack of growth effect by progesterone in breast epithelial cells lacking nuclear receptors. This study examined possible nongenomic effects of progesterone in breast epithelia by using MCF-10A cells known to lack nuclear progesterone receptor expression. Treatment for 30-60 min with progesterone or the progestin, R5020, increased mitochondrial activity as shown by an increase in mitochondrial membrane potential (hyperpolarization) with a concordant increase in total cellular ATP. The reaction was inhibited by a specific progesterone receptor antagonist and not affected by the translation inhibitor cycloheximide. Progestin treatment inhibited apoptosis induced by activation of the FasL pathway, as shown by a decrease in sub-G(1) cell fraction during fluorescence-activated cell sorting and a decrease in caspase 3/7 levels. Progestin treatment did not alter the cell cycle over 48 h. Our study demonstrates a nongenomic action of progesterone on benign breast epithelial cells, resulting in enhanced cellular respiration and protection from apoptosis.

Progesterone receptors A and B and estrogen receptor alpha expression in normal breast tissue and fibroadenomas

Fibroadenomas are the most common benign breast tumors, occurring mainly in young women. Their responses to the hormonal environment are similar to those of normal breast tissue, which suggests that steroid receptors may play a role in tumor development. We evaluated the gene and protein expression of progesterone receptors A and B (PRA and PRB) and the protein expression of estrogen receptor alpha (ER-alpha) in fibroadenoma samples, comparing with adjacent normal breast tissue, from 11 premenopausal women. Progesterone and estradiol levels were determined. No alterations in the PRs gene and protein expression and the ER-alpha protein expression were observed between the follicular and luteal phases, in normal breast versus fibroadenomas. Protein levels of PRA and PRB were higher in fibroadenomas compared to normal breast tissue (P = 0.038 and P = 0.031), while the PRs mRNA levels were similar in both tissues (P = 0.721 and P = 0.139). There were no differences in ER-alpha protein expression between normal breast tissue and fibroadenomas (P = 0.508). The PRA:PRB ratio was similar in the tissues, and also showed a strong correlation in both (r = 0.964, P = 0.0001). Our data suggest a role of PRs in the growth and development of fibroadenomas, although without alterations of the PRA:PRB ratio in these tumors. The absence of alterations in ER-alpha protein levels could be a characteristic behavior of fibroadenomas, unlike breast cancer.

Estrous cycle modulates ovarian carcinoma growth

PURPOSE

The effects of reproductive hormones on ovarian cancer growth are not well understood. Here, we examined the effects of estrous cycle variation and specific reproductive hormones on ovarian cancer growth.

EXPERIMENTAL DESIGN

We investigated the role of reproductive hormones in ovarian cancer growth using both in vivo and in vitro models of tumor growth.

RESULTS

In vivo experiments using the HeyA8 and SKOV3ip1 ovarian cancer models showed that tumor cell inoculation during proestrus significantly increased tumor burden (251-273%) compared with injection during the estrus phase. Treatment of ovariectomized mice with 17beta-estradiol resulted in a 404% to 483% increase in tumor growth compared with controls. Progestins had no significant effect, but did block estrogen-stimulated tumor growth. Tumors collected from mice sacrificed during proestrus showed increased levels of vascular endothelial growth factor (VEGF) and microvessel density compared with mice injected during estrus. HeyA8, SKOV3ip1, and mouse endothelial (MOEC) cells expressed estrogen receptor alpha and beta and progesterone receptor at the protein and mRNA levels, whereas 2774 ovarian cancer cells were estrogen receptor-negative. In vitro assays showed that 17beta-estradiol significantly increased ovarian cancer cell adhesion to collagen in estrogen receptor-positive, but not in estrogen receptor-negative cells. Additionally, 17beta-estradiol increased the migratory potential of MOEC cells, which was abrogated by the mitogen-activated protein kinase (MAPK) inhibitor, PD 09859. Treatment with 17beta-estradiol activated MAPK in MOEC cells, but not in HeyA8 or SKOV3ip1 cells.

CONCLUSION

Our data suggest that estrogen may promote in vivo ovarian cancer growth, both directly and indirectly, by making the tumor microenvironment more conducive for cancer growth.

Progesterone and breast cancer

Progesterone is an ovarian steroid hormone that is essential for normal breast development during puberty and in preparation for lactation and breastfeeding. The actions of progesterone are primarily mediated by its high-affinity receptors, which include the classical progesterone receptor (PR)-A and -B isoforms, located in diverse tissues, including the brain, where progesterone controls reproductive behavior, and the breast and reproductive organs. Progestins are frequently prescribed for contraception or during postmenopausal hormone replacement therapy, in which progestins are combined with estrogen as a means to block estrogen-induced endometrial growth. The role of estrogen as a potent breast mitogen is undisputed, and inhibitors of the estrogen receptor and estrogen-producing enzymes (aromatases) are effective first-line cancer therapies. However, PR action in breast cancer is grossly understudied and remains controversial. Herein, we review existing evidence and discuss the challenges to defining a role for progesterone in breast cancer.

Exogenous and endogenous hormones, mammographic density and breast cancer risk: can mammographic density be considered an intermediate marker of risk?

Elevated mammographic density measures are a well-established, relatively strong risk factor for breast cancer development. A systematic review of prospective cohort studies and cross-sectional studies strikingly establishes parallels between the associations of combined postmenopausal estrogen and progestin replacement therapy with, on the one hand, mammographic densities and, on the other hand, breast cancer risk. Other parallel observations were the inverse associations of both mammographic density and breast cancer risk with the selective estrogen receptor modulator tamoxifen, and direct associations with prolactin. Paradoxically, however, high mammographic density has been found associated with higher risks of both estrogen- and progesterone-receptor positive (ER+/ PR+) and negative (ER-/PR-) breast cancers, while hormone replacement therapy (HRT) use, but also circulating (blood) levels of androgens, estrogens, and prolactin appear to be associated more specifically to the risk of ER+ tumors. The effects of aromatase inhibitors and gonadotropin-releasing hormone agonists on breast density, as well as on breast cancer risk, still require further investigation. Regarding circulating levels of insulin-like growth factor (IGF)-I or IGFBP-3, studies did not show fully consistent relationships with mammographic density measures and breast cancer risk. In view of these various findings, it is impossible, at present, to propose mammographic density measures as an intermediate risk-related phenotype, integrating the effects of exogenous and/or endogenous hormones on the risk of developing breast cancer.