Aromatase inhibitors in the treatment of breast cancer

Estradiol, the most potent endogenous estrogen, is biosynthesized from androgens by the cytochrome P450 enzyme complex called aromatase. Aromatase is present in breast tissue, and intratumoral aromatase is the source of local estrogen production in breast cancer tissues. Inhibition of aromatase is an important approach for reducing growth-stimulatory effects of estrogens in estrogen-dependent breast cancer. Steroidal inhibitors that have been developed to date build upon the basic androstenedione nucleus and incorporate chemical substituents at varying positions on the steroid. Nonsteroidal aromatase inhibitors can be divided into three classes: aminoglutethimide-like molecules, imidazole/triazole derivatives, and flavonoid analogs. Mechanism-based aromatase inhibitors are steroidal inhibitors that mimic the substrate, are converted by the enzyme to a reactive intermediate, and result in the inactivation of aromatase. Both steroidal and nonsteroidal aromatase inhibitors have shown clinical efficacy in the treatment of breast cancer. The potent and selective third-generation aromatase inhibitors, anastrozole, letrozole, and exemestane, were introduced into the market as endocrine therapy in postmenopausal patients failing antiestrogen therapy alone or multiple hormonal therapies. These agents are currently approved as first-line therapy for the treatment of postmenopausal women with metastatic estrogen-dependent breast cancer. Several clinical studies of aromatase inhibitors are currently focusing on the use of these agents in the adjuvant setting for the treatment of early breast cancer. Use of an aromatase inhibitor as initial therapy or after treatment with tamoxifen is now recommended as adjuvant hormonal therapy for a postmenopausal woman with hormone-dependent breast cancer.

Signal transducer and activator of transcription 5 as a key signaling pathway in normal mammary gland developmental biology and breast cancer

STAT5 consists of two proteins, STAT5A/B, that impact mammary cell differentiation, proliferation, and survival. In normal development, STAT5 expression and activity are regulated by prolactin signaling with JAK2/ELF5, EGF signaling networks that include c-Src, and growth hormone, insulin growth factor, estrogen, and progesterone signaling pathways. In cancer, erythropoietin signaling can also regulate STAT5. Activation levels are influenced by AKT, caveolin, PIKE-A, Pak1, c-Myb, Brk, beta-integrin, dystroglycan, other STATs, and STAT pathway molecules JAK1, Shp2, and SOCS. TGF-β and PTPN9 can downregulate prolactin- and EGF-mediated STAT5 activation, respectively. IGF, AKT, RANKL, cyclin D1, BCL6, and HSP90A lie downstream of STAT5.

Novel sulfonanilide analogues suppress aromatase expression and activity in breast cancer cells independent of COX-2 inhibition

Aromatase is a particularly attractive target in the treatment of estrogen receptor positive breast cancer. Aromatase levels in breast cancer cells are enhanced by prostaglandins and reduced by COX inhibitors. The synthesis and biological evaluation of a novel series of sulfonanilide analogues derived from the COX-2 selective inhibitor NS-398 are described. The compounds suppress aromatase enzyme activity in SK-BR-3 breast cancer cells in a dose- and time-dependent manner. The effect of these compounds on COX-2 inhibition is investigated in breast cancer cells as well. Structure-activity analysis does not find a correlation between aromatase suppression and COX-2 inhibition. Microsomal aromatase inhibition studies rule out the possibility of direct enzyme inhibition. Real-time PCR analysis demonstrates that the sulfonanilide analogues decrease aromatase gene transcription in SK-BR-3 cells. These studies suggest that the novel sulfonanilide compounds suppress aromatase activity and transcription in SK-BR-3 breast cancer cells independent of COX-2 inhibition.

Role of the azinomycin naphthoate and central amide in sequence-dependent DNA alkylation and cytotoxicity of epoxide-bearing substructures

Studies report a strong correlation between duplex DNA alkylation and in vitro cytotoxicity for a series of azinomycin partial structures 2-6 bearing the biologically relevant epoxide. Compounds lacking the naphthoate ester (e.g., 5 and 6) were poorly reactive toward DNA and were biologically inactive, as were compounds bearing the naphthoate but lacking the terminal carboxamide (e.g., 2). Compounds were evaluated for cytotoxicity against two breast cancer cell lines. [structure: see text]

Human Pancreatic Cancer-Associated Stellate Cells Remain Activated after in vivo Chemoradiation

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extensive fibrotic reaction or desmoplasia and complex involvement of the surrounding tumor microenvironment. Pancreatic stellate cells are a key mediator of the pancreatic matrix and they promote progression and invasion of pancreatic cancer by increasing cell proliferation and offering protection against therapeutic interventions. Our study utilizes human tumor-derived pancreatic stellate cells (HTPSCs) isolated from fine needle aspirates of pancreatic cancer tissue from patients with locally advanced, unresectable pancreatic adenocarcinoma before and after treatment with full-dose gemcitabine plus concurrent hypo-fractionated stereotactic radiosurgery. We show that HTPSCs survive in vivo chemotherapy and radiotherapy treatment and display a more activated phenotype post-therapy. These data support the idea that stellate cells play an essential role in supporting and promoting pancreatic cancer and further research is needed to develop novel treatments targeting the pancreatic tumor microenvironment.

BRCA1 deficient mouse models to study pathogenesis and therapy of triple negative breast cancer

Genetically engineered mice along with allograft and xenograft models can be used to effectively model triple negative breast cancer both for studies of pathophysiology as well as preclinical prevention and therapeutic drug studies. In this review eight distinct genetically engineered mouse models of BRCA1 deficiency are discussed in relationship to the generation of triple negative mammary cancer. Allograft models derived from some of these genetically engineered mice are considered and xenograft models derived from breast cancers that developed from BRCA1 mutation are presented. Examples of the use of genetically engineered, allograft and xenografts models for preventive and therapeutic studies are presented.

If cultural sensitivity is not enough to reduce health disparities, what will pharmacy education do next?

INTRODUCTION

Social determinants greatly impact health, and evidence suggests that health disparities still exist between patient populations. The pharmacist's role in public health continues to evolve; therefore, the deliberate integration of public health into pharmacy education is essential. Pharmacy graduates must be able to recognize social determinants of health in order to help reduce disparities and inequities in access to quality care.

PERSPECTIVE

Cultural sensitivity training has been one of the most commonly used vehicles to educate students about health disparities. Whereas cultural sensitivity is of critical importance, it could unintentionally perpetuate the idea of culture as the sole construct to predict health outcomes. Consequently, it is important that we approach this societal problem from a public health perspective by addressing not just culture, but all other social determinants of health.

IMPLICATIONS

As disparities in health outcomes continue to widen for some patient groups, it is imperative for pharmacy programs to explore novel instructional approaches to teach health disparities. A paradigm shift from awareness to action and advocacy must involve educating students on the multifaceted effects of social determinants when designing interventions to help reduce health disparities.

Enoxacin and Epigallocatechin Gallate (EGCG) Act Synergistically to Inhibit the Growth of Cervical Cancer Cells in Culture

Cervical cancer is a major cause of death in females worldwide. While survival rates have historically improved, there remains a continuous need to identify novel molecules that are effective against this disease. Here, we show that enoxacin, a drug most commonly used to treat a broad array of bacterial infections, is able to inhibit growth of the cervical cancer cells. Furthermore, our data show that epigallocatechin gallate (EGCG), a plant bioactive compound abundant in green tea, and known for its antioxidant effects, similarly functions as an antiproliferative agent. Most importantly, we provide evidence that EGCG functions synergistically against cancer cell proliferation in combined treatment with enoxacin. These data collectively suggest that enoxacin and EGCG may be useful treatment options for cases of cervical cancer.

Association of Over-Expressed Estrogen Receptor Alpha with Development of Tamoxifen Resistant Hyperplasia and Adenocarcinomas in Genetically Engineered Mice

BACKGROUND

Estrogen receptor alpha (ERα) and cyclin D1 are frequently co-expressed in human breast cancer. Some, but not all, studies link tamoxifen resistance to co-expression of cyclin D1 and ERα. In mice over-expression of either cyclin D1 or ERα in mammary epithelial cells is sufficient to induce mammary hyperplasia. Cyclin D1 over-expression in mice leads to mammary adenocarcinoma associated with activated estrogen signaling pathways. ERα over-expression in mice leads to mammary hyperplasia and cancer. Significantly, disease development in these mice is abrogated by loss of cyclin D1.

METHODS

Genetically engineered mouse models were used to determine whether or not ERα over-expression demonstrated cooperativity with cyclin D1 over-expression in cancer development, reaction to the chemical carcinogen DMBA, or tamoxifen response.

RESULTS

Adding ERα over-expression to cyclin D1 over-expression increased the prevalence of hyperplasia but not cancer. Single dose DMBA exposure did not increase cancer prevalence in any of the genotypes although cyclin D1 over-expressing mice demonstrated a significant increase in hyperplasia. Tamoxifen treatment was initiated at both young and older ages to test for genotype-specific differences in response. Although normal ductal structures regressed in all genotypes at both younger and older ages, tamoxifen did not significantly reduce the prevalence of either hyperplasia or cancer in any of the genotypes. All of the cancers that developed were hormone receptor positive, including those that developed on tamoxifen, and all showed expression of nuclear-localized cyclin D1. In summary, development of tamoxifen resistant hyperplasia and cancer was associated with expression of ERα and cyclin D1.

CONCLUSION

These preclinical models will be useful to test strategies for overcoming tamoxifen resistance, perhaps by simultaneously targeting cell cycle regulatory pathways associated with cyclin D1.

Abstract A26: Aromatase over-expression results in the development of ductal growth abnormalities in the mammary gland of a conditional transgenic mouse model

Estrogens are required for the development of the normal mammary gland; however, studies suggest that estrogen and its metabolites may have mutagenic and carcinogenic potential in the mammary gland. Aromatase is key to estrogen biosynthesis, but its over-expression may play a role in the development of breast cancer by increasing mitotic activity in breast epithelial cells. Therefore, it is highly valuable to have mouse models with increased local estrogen production to use to develop optimal therapeutic and chemopreventive strategies to treat these lesions. The purpose of this study was to evaluate if increased local estrogen production led to the development of mammary gland preneoplasia. To test our hypothesis we developed a conditional transgenic mouse model to control the spatial and temporal aromatase expression in the mammary gland. Mammary glands were collected at 4 and 12 months of age for morphological, histological, gene and protein expression studies in both MMTV-rtTA/tet-op-Aromatase and wild-type mice. RT-PCR analysis of aromatase mRNA confirmed that the gene was conditionally expressed in the mammary gland as compared to control mice. Aromatase activity assays confirmed a significantly higher enzyme activity in the mammary glands of MMTV-rtTA/tet-op-Aromatase compared to wild-type. Mammary glands were evaluated for morphological changes using confocal microscopy, whole-mount and hematoxylin and eosin staining. Aromatase over-expression resulted in a higher incidence of morphological and histological abnormalities such as hyperplastic alveolar nodules, ductal dysplasia, ductal carcinoma in situ, and the unexpected persistence of terminal end buds at 12 months of age. These changes were associated with ERK1/2 and AKT activation. In summary, we generated a novel transgenic mouse system to investigate the role of aromatase over-expression in mammary epithelial cells during mammary gland development. Increased aromatase activity resulted in the development of ductal growth abnormalities and increased ductal density. This model represents a valuable tool to investigate the effect of estrogen over-production in the mammary gland microenvironment at specific times during development.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A26.

Leveraging Expertise from Community Resources to Improve the Role of the Pharmacist in HIV Testing and Counseling

The human immunodeficiency virus (HIV) epidemic continues to be a major global public health issue. Moreover, disparities continue to persist in HIV among racial and ethnic minority populations, with the highest rates of new diagnoses in Black/African American and Hispanic/Latino men who have sex with men in the United States. Pharmacists are one of the most accessible and trusted health care professionals. Therefore, it is imperative that student pharmacists are educated on culturally-competent HIV testing and risk behaviors counseling. This study describes the development of a partnership between a pharmacy school and a community-based organization to offer an HIV counseling and testing training program to help develop skills in delivering HIV testing services. The HIV counseling and testing training program contains learning modules that provide a wide array of in-depth information about HIV patient care in the community. The partnership allows for the enjoyment of a myriad of benefits for students, the pharmacy program, the community-based organization, and the public health of the community-at-large. Students feel more prepared and comfortable working with patients in discussing HIV transmission risk factors and test results as a result of this training. Such partnerships support the pharmacist’s role in the public health arena. A successful and durable relationship between a community partner and a school of pharmacy is a feasible strategy for pharmacy progress in public health.

p53 heterozygosity leads to deregulated apoptosis and cell proliferation in the mammary gland of ERα over-expressing mice

Abstract #2008

Background: Transgenic mouse models are a common experimental tool for unraveling gene function. Breast cancer develops as genetic changes accumulate in the ductal epithelium giving rise to precursor lesions such as atypical ductal hyperplasias, which may progress to ductal carcinoma in situ (DCIS) and eventually invasive breast cancer. This process is associated with mutations in tumor suppressor genes such as p53 resulting in the deregulation of essential genes. p53 plays a role in mediating cell response to various stresses by inducing or repressing genes involved in cell cycle arrest, senescence, apoptosis and DNA repair. Studies have shown that p53 is a predictor for local recurrence of DCIS. About 65% of breast cancers are estrogen receptor alpha (ERα) positive and estrogen dependent. Deregulated expression of ERα in normal breast epithelium has been found in conjunction with breast cancer, leading to the concept that loss of the normal regulatory mechanisms that control expression levels of ERα in normal breast epithelium may increase the risk for the development of breast cancer. This study tests the hypothesis that p53 heterozygosity may lead to an aberrant growth response to hormonal stimuli and development of mammary gland preneoplasia.
 Methodology: To examine if p53 heterozygosity promotes disease in mammary glands with deregulated expression of ERα, a conditional ERα in mammary tissue mouse model (MMTV-rtTA/tet-op-ERα or CERM) was bred to a p53 homozygous mutant (p53-/-) mouse model. For progression studies, mammary glands were collected at 12 months of age for morphological and histological studies both in intact nulliparous mice. A group of mice was ovariectomized at 14 weeks of age and 2 weeks later treated with either placebo or 17β-estradiol for 48 hours to dissect the molecular events attributable to specific hormonal stimulation as compared to normal ovarian function.
 Results: Loss of p53 resulted in a statistically significant higher percentage of hyperplastic alveolar nodules, both by itself and in mice with ERα deregulation in the mammary gland. p53 heterozygosity resulted in a higher incidence of morphological and histological abnormalities such as dilated ducts, ductal dysplasia, ductal carcinoma in situ, and abnormal stroma. These lesions showed higher rates of cell proliferation and lower rates of apoptosis. Phospho-p53 immunohistochemistry showed evidence of DNA damage in the p53 heterozygous mice. There was no significant change in the terminal ductal structures in mammary glands of ovariectomized mice when compared to mice treated with exogenous 17β-estradiol after 48 hrs.
 Conclusions: p53 heterozygosity predisposed mammary tissue to preneoplastic changes both by itself and in collaboration with deregulated ERα expression. The combination of deregulated ERα expression and p53 heterozygosity was associated with more disease than either genetic change by itself. Loss of p53 leads to a deregulation in apoptosis and cell proliferation in the mammary gland of ERα over-expressing mice suggesting that both processes are involved in the development of preneoplasia.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2008.

Abstract B70: A conditional aromatase over-expressing in the mammary gland transgenic mouse as a potential model in cancer prevention research

B70

Background

Breast cancer develops as genetic changes accumulate in the ductal epithelium giving rise to precursor lesions such as atypical ductal hyperplasias, which may progress to ductal carcinoma in situ (DCIS) and eventually invasive breast cancer. This progress is promoted by estrogens. Estrogens are biosynthesized from androgens by the aromatase enzyme. Estrogen is required for the proliferation and morphogenesis of the normal mammary gland; however, studies suggest that estrogen and its metabolites may have mutagenic and carcinogenic potential in the mammary gland. Therefore, it is highly valuable to have mouse models with increased local estrogen production to use to develop optimal therapeutic and chemopreventive strategies to treat these lesions.

Purpose

The purpose of this work is to develop a conditional transgenic mouse model that would provide an in vivo method of controlling the spatial and temporal regulation of aromatase expression.

Methodology

The transgenic mouse model was developed by using two transgenes. One transgene is composed of the mouse mammary tumor virus-long terminal repeat (MMTV-LTR) linked to sequences encoding the tetracycline responsive reverse transactivator (rtTA). The other transgene has a tetracycline responsive promoter (tet-op) linked to sequences encoding the human aromatase (MMTV-rtTA/tet-op-Arom). Mammary glands were collected at 4 months of age for morphological, histological, and gene expression studies in both MMTV-rtTA/tet-op-Arom and wild-type mice.

Results

RT-PCR analysis of aromatase mRNA shows that the gene is conditionally expressed in the mammary gland as compared to control mice. The mammary glands were evaluated for morphological changes using confocal microscopy, whole-mount and hematoxylin and eosin staining. Preliminary data at 4 months of age shows that overexpressing aromatase in the mammary gland leads to developmental abnormalities, abnormal ductal growth and increased ductal density. Gene expression studies will be performed to evaluate additional markers of proliferation, survival, and differentiation. This model is being cross-bred to our conditional overexpression of estrogen receptor α (ERα) in the mammary gland (CERM) model. CERM mice are an established tool for investigation of mechanisms involved in progression and regression of ERα-induced mammary hyperplasia and DCIS.

Conclusion

The novel CERM/tet-op-aromatase mouse model (CERM/Arom) is being developed to model more closely the human breast with expression of both ERα and aromatase in mammary tissue. This model can be utilized to evaluate agents to prevent carcinogenesis in the presence of aromatase over-expression in the mammary gland at specific times during development. This research is supported by the Susan G. Komen for the Cure Postodoctoral Fellowship Award KG080359 and the NIH National Cancer Institute Grant R01CA112176.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):B70.

Developing a Co-Curricular Activity to Introduce Student Pharmacists to the Cultural Proficiency Continuum Framework

Background:

As the United States becomes more culturally diverse, health professionals must be able to demonstrate competency in caring for a multitude of diverse patients. The cultural proficiency continuum has proven to be an effective framework to assess where individuals and institutions are on the continuum of cultural sensitivity and competence in educational settings.

Innovation:

A co-curricular activity was developed as an exercise in self-awareness to allow first year pharmacy students the opportunity to explore potential biases by evaluating comfort in both social and patient care settings. The 90-minute activity employed a lecture, followed by both small and large group discussions and a debriefing session.

Findings:

Student survey responses showed their appreciation of this framework and its application to patient-centered care. Student self-rated knowledge increased by 3 points on a 10-point scale after completion of the activity. Students agreed that their level of cultural awareness would lead them to respond appropriately in cross-cultural situations, and that the provision of care is dependent on approaches that are culturally proficient.

Conclusion:

This activity dismantles the misconception of cultural competence as an attainable finite skill, but instead presents it as an ongoing process of self-awareness. The co-curricular activity offers an easy to implement model of education that could potentially fit the needs of pharmacy programs searching for ideas to teach cultural competency and social determinants of health, while circumventing the need to affect curricular structure.

Abstract A20: Investigating the role of cell cycle proteins and CDK4/6 inhibitor PD0332991 in the redifferentiation of irreversible dysplasia

Background: An important strategy in cancer prevention treatment programs is to target the reversal of premalignant disease through re-differentiation. Furthermore, understanding early changes occurring during preneoplastic dysplasia may provide diagnostic and therapeutic insight for cancer prevention programs. Aberrant regulation of the CDK4/6-CyclinD-Rb signaling pathway is one of the most common aberrations found in human cancer; however, there are few published reports describing the status of these cell cycle proteins in preneoplasia. Identifying biomarkers of reversal of dysplasia as well as mechanisms of malignant transformation from preneoplastic disease to cancer will be essential in drug development for chemoprevention strategies. Preclinical mouse models of reversible and refractory dysplasia help elucidate mechanisms responsible for irreversible disease progression and highlight potential targets for its reversal and prevention. This study examined and compared the potential roles of altered expression and/or activation of cell cycle regulatory proteins. Additionally, we examined the effect of a CDK4/6 inhibitor PD0332991 in a system of early dysplasia.

Specific Aims: 1. Evaluate expression patterns of cell cycle regulatory network proteins in reversible and irreversible stages of epithelial dysplasia. 2. Test if inhibition of CDK4/6 through PD0332991 can initiate re-differentiation of refractory epithelial dysplasia. 3. Evaluate cell cycle protein expression changes after inhibition of CDK4/6.

Methods: A conditional transgenic mouse model, MMTV-tTA/tet-op-TAg (tTA/TAg) demonstrating time dependent reversible and refractory irreversible stages of salivary epithelial dysplasia following down regulation of the initiating oncogene was used. Previous studies demonstrated refractory dysplasia is a field effect without chromosomal rearrangements. Cell cycle regulatory protein expression patterns were compared by western blot and IHC analyses at the 4 (reversible) and 7 (irreversible) month stages. To test the chemopreventive role of CDK4/6 inhibition, PD0332991 inhibitor was administered to at the 7-month (irreversible) stage of dysplasia. Doxycycline was administered with the maximum recommended dose of PD0339221 (150 mg/kg) for 10 days via gavage.

Results and Conclusions: Cell cycle proteins were differentially expressed at the reversible 4-month vs. irreversible 7-month time-point. The pattern of expression suggests that irreversible refractory dysplasia is maintained independently from the initiating oncogene due to persistent up-regulation of Cyclin D1 and CDK4/6 with consequent Rb phosphorylation and increased levels of DP-1 and E2F in a self-renewing cyclical manner. Treatment with PD0332991 at the 7 month (irreversible) stage resulted in a significant histological reversal in preliminary studies. The data indicate that cell cycle proteins play an important role in maintenance of dysplasia and are valid targets for cancer chemoprevention.

Citation Information: Cancer Prev Res 2011;4(10 Suppl):A20.

Using Biochemistry to Educate Students on the Causal Link between Social Epigenetics and Health Disparities

Background

While pharmacy education standards require students to recognize social determinants of health (SDOH), there is an opportunity to improve how this is taught in the curriculum. One innovative approach is to educate student pharmacists in a biochemistry course through the integration of topics like epigenetics using SDOH as the framework.

Innovation

A 50-minute educational activity was used to supplement material on the regulation of gene expression, in which epigenetic changes are driven by SDOH. It provided students with a biochemical basis to explain some health disparities, rather than viewing them exclusively as social obstacles to health. The activity employed a mini-lecture, a short video, as well as both small and large group discussion. A reflective paper was used to assess students' understanding of the topic, and the role of the pharmacist in helping patients prevent diseases caused by epigenetic changes due to social determinants of health.

Findings

A post-activity survey showed that the activity increased students' perception of knowledge about SDOH, as well as the effect of epigenetic changes on health outcomes. Furthermore, this activity increased students' awareness about the role that SDOH play in epigenetic changes and challenged students to understand the role that society plays in health outcomes.

Conclusions

The preventable nature of health inequities creates an opportunity to integrate public health into pharmacy education. The integration of epigenetics and SDOH gives the student an opportunity to provide a mechanistic link between social inequities and biochemical processes.

Abstract 197: Reduction in lobular but not ductal hyperplasia by the PGR inhibitor ORG33628 in a CYP19A1 overexpressing mouse model of breast cancer risk

Background: The Women's Health Initiative demonstrated increased breast cancer risk in women exposed to estrogen with progesterone. Genetically engineered mice with conditional mammary epithelial cell targeted Cytochrome P45019A1 (CYP19A1/aromatase) over-expression (tet-op-CYP19A1/MMTV-rtTA mice) tested the impact of a selective progesterone receptor (PGR) inhibitor, ORG33628, on mammary hyperplasia and cancer development. This model demonstrates increased percentages of PGR+ mammary epithelial cells (MECs) cells at the hyperplastic stage and triple negative (Estrogen Receptor (ER)-, PGR-, Receptor tyrosine-protein kinase erbB-2 (HER2/neu)-) adenocarcinomas.

Purpose: Test if ORG33628 reduces mammary hyperplasia and blocks cancer formation in tet-op-CYP19A1/MMTV-rtTA mice.

Methods: Female tet-op-CYP19A1/MMTV-rtTA mice were implanted subcutaneously with a pellet containing either ORG33628 7.5mg (60-day release) or placebo at age 10m. A smaller study tested ORG33628 in CYP19A1/MMTV-rtTA/trp53+/- mice. Mice were necropsied at age 12m and mammary tissue examined to determine if ORG33628 altered lobular/ductal hyperplasia prevalence or blocked progression to hyperplastic alveolar nodules (HANs) or cancer. Immunohistochemistry (IHC) was employed to compare MEC proliferative index (PI) (Ki-67) and percentage of MECs expressing nuclear-localized ER/PGR. An uterotropic assay tested if ORG33628 blocked estrogen-induced changes in the uterus/cervix. Ovariectomized 6w old mice were implanted subcutaneously with pellets of 0.72g 17β-estradiol and either ORG33628 or placebo, necropsied 3 days later, and uterine weight, PI and ER/PGR expression compared in uterine and cervical epithelium and stroma.

Results: ORG33628 treatment reduced lobular hyperplasia prevalence (Fisher's exact, p<0.05) and percentages of PGR+ MEC (9.3% to 5.2%, t-test, p<0.05), but did not alter ductal hyperplasia or HAN prevalence or block cancer formation. ORG33628 reduced estrogen-induced uterine weight gain (t-test, p<0.05) and PI in cervical epithelium (38.6% to 15%, t-test, p<0.05) in the uterotropic assay.

Conclusions: ORG33628 reduced lobular but not ductal hyperplasia and did not prevent progression to HANs or cancer. In normal development, estrogen plays the more important role in ductal development and progesterone in lobular development paralleling the isolated impact of ORG33628 on lobular disease here. These results suggest that reducing ductal hyperplasia may be a prerequisite for cancer prevention or that reducing lobular hyperplasia at 10m in this model is too late due to the presence of triple negative cancer progenitor cells.

Support: P30CA051008, RO1CA112176, T32CA009686-15, KG080359. Content solely responsibility of authors and does not necessarily represent official NCI/NIH views.

Citation Format: Sarah A. Dabydeen, Weisheng Wang, Edgar S. Diaz-Cruz, Levy Kopelovich, Robert I. Glazer, Priscilla A. Furth. Reduction in lobular but not ductal hyperplasia by the PGR inhibitor ORG33628 in a CYP19A1 overexpressing mouse model of breast cancer risk. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 197. doi:10.1158/1538-7445.AM2013-197