Differential Roles of Estrogens in Obesity-mediated ER+ Breast Cancer Development

Project Information

EOBRECA

Grant agreement ID: 845104

DOI

10.3030/845104

Project closed

EC signature date 22 March 2019

Start date 1 September 2019

End date 23 November 2021

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 160 932,48

EU contribution

€ 160 932,48

Coordinated by

UNIVERSIDAD DE GRANADA
Spain

Periodic Reporting for period 1 - EOBRECA (Differential Roles of Estrogens in Obesity-mediated ER+ Breast Cancer Development)

Reporting period: 2019-09-01 to 2021-08-31

Summary of the context and overall objectives of the project

Breast cancer is the most common cancer and the leading cause of cancer death in women in the world, and risk thereof rises progressively after menopause. Obesity is associated with increased postmenopausal, but not premenopausal, breast cancer risk, particularly for estrogen receptor-positive (ER+) breast cancers, which represent over 70% of all breast cancer cases diagnosed. Importantly, after menopause estrogens are mostly produced in the adipose tissue. These observations suggest a link between the estrogenic milieu associated to menopausal status and obesity, with ER+ breast cancer. This Project investigates if main pre- and postmenopausal estrogens in circulation, estradiol (E2) and estrone (E1) respectively, have different biological functions. In addition, this work investigates if enzymes involved in E1 synthesis, have an oncogenic role in this disease, and could be a new marker for early diagnosis and patient prognosis, and a new therapeutic target for patient´s treatment.
The social impact of this Research Project is based on its potential to reduce disease incidence, morbidity and mortality. In this regards, results obtained from this Project may demonstrate a different role of E2 and E1 in ER+ breast cancer biology; and serve to develop new Hormone Replacement Therapies (HRT) safest for postmenopausal women, reducing the incidence of this disease. Moreover, the identification of E1-synthesizing enzymes as new molecular markers for early disease detection, or even useful to identify subjects at high risk to develop ER+ breast cancer, could reduce significantly the morbidity and mortality of this disease.
The main objective of this project is to better understand the roles of E1 and E2 on obesity-associated ER+ breast cancer development. We hypothesize that E1 plays a key role in the increased risk of developing ER+ breast cancer in obese postmenopausal women through a differential regulation of important molecular pathways in normal tissues than the effect demonstrated for E2. In addition, we hypothesize that high expression of enzymes that convert E2 into E1, have an oncogenic role in the development of this disease and may be a new marker and a new therapeutic target for ER+ breast cancer patients.
After the completion of this project we have obtained several important conclusions:
- Menopause, obesity and cancer increase inflammation in the breast tissue
- Estrone stimulates and estradiol relieves obesity-mediated inflammation
- Adipocytes from the breast tissue, specially thus from obese and postmenopausal women, induce inflammation and progression on breast cancer cells
- Estrone, but not estradiol, activates metastatic programs in ER+ human epithelial cancer cells from the breast and cervix
- Enzymes that convert estradiol into estrone play a key role in ER+ breast carcinogenesis, tumor growth and metastasis

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project was designed to answer three key questions about estrogens and ER+ breast cancer:
1. Do estrone (E1) and estradiol (E2) have different biological functions in the context of obesity?
To answer this question we have treated with E1 or E2 different cell types with the addition or not of TNFα, a pro-inflammatory cytokine. Moreover, we have studied in vivo the role of both estrogens in regulating the activity of a signaling pathway involved in inflammation, called NFκB, in combination with obesity. Results obtained demonstrate that, in contrast to the known anti-inflammatory role of E2, E1 is pro-inflammatory and potentiates obesity-mediated inflammation. Moreover, both estrogens also differ in the regulation of other important processes. These results demonstrate for the first time that the biological functions of the main serum estrogens before and after menopause, E2 and E1 respectively, are not equal.
2. Does estrone have a key role in ER+ breast tumorigenesis?
To solve this question ER+ breast cancer cells were treated with E1 or E2 in vitro and studied for different phenotypic and functional characteristics of cancer aggressiveness. In addition, we assayed in vivo the activity of both estrogens in ER+ breast tumor growth and metastasis. As result of these experiments we found that cells exposed to E1 acquire features of a more aggressive cancer phenotype compared to thus treated with E2 in vitro. These observations were supported by results obtained from in vivo experiments, were we found that E1 increases the proportion of tumor initiating cells, tumor growth and metastasis.
3. Do enzymes converting estradiol into estrone have an oncogenic role in ER+ breast cancer?
The work performed to respond to this question included different experimental approaches, such as: i) analysis of clinical data from public databases, ii) generation and analysis of genetically modified ER+ breast cancer cells and ER+ normal mammary epithelial cells; and iii) discovery of specific inhibitors. Our results demonstrate an association between these enzymes with worse patient outcome. Moreover, the overexpression of these enzymes increases ER+ breast cancer aggressiveness and the acquisition of the ability to develop tumors in mice by ER+ normal mammary epithelial cells. By last, we have identified few potential inhibitors for E1-synthesizing enzymes but further experiments are needed to determine their clinical potential.
Results obtained from this project have been properly disseminated to different audiences, by: the publication of 4 research articles (2 published and 2 submitted); publication in no scientific journals and UGR News Channel; the use of social networks; by radio interview; through conference contribution; and participating in the European Research Night and Science is Wonderful.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

For decades it has been assumed that E2 was the active form of estrogens, and E1 was only an E2 precursor. However, results from this project demonstrate for the first time a different biological function of the main serum estrogens before and after menopause, E2 and E1 respectively. In summary, this project establish that E1, and the enzymes involved in its synthesis, play a key role in ER+ breast cancer development and progression, and may also be related to other estrogen-dependent diseases. Our data also represent the first rational explanation to the increased ER+ breast cancer risk after menopause, particularly for obese postmenopausal women.
The potential impact of this project could be examined from two different points of view:
- Scientific impact: The demonstration that E1, and E1-synthesizing enzymes, play a key role in ER+ breast carcinogenesis open a new paradigm in the study of this disease. Until date, almost all published works in this field have been limited to study the effect of E2 on ER+ breast cancer cells. Our research may serve to focus future investigations in the study of E1, instead E2, as the main estrogen involved in ER+ breast cancer tumorigenesis.
- Socio-economic impact: Breast cancer is the most common cancer and the first cause of death from cancer in women worldwide, and ER+ subtypes represent over 70% of all cases diagnosed. The social and economic impact of this Research Project is based on its potential to reduce disease incidence, morbidity and mortality. This work highlight the clinical relevance of E1, and E1-synthesizing enzymes, in this disease, opening a new line of investigation for the development of new clinical strategies in the prevention and treatment of this disease.

Hypothesis