Experimental models of endocrine responsive breast cancer: strengths, limitations, and use

Rat Models of Hormone Receptor-Positive Breast Cancer

Hormone receptor-positive (HR+) breast cancer (BC) is the most common type of breast cancer among women worldwide, accounting for 70-80% of all invasive cases. Patients with HR+ BC are commonly treated with endocrine therapy, but intrinsic or acquired resistance is a frequent problem, making HR+ BC a focal point of intense research. Despite this, the malignancy still lacks adequate in vitro and in vivo models for the study of its initiation and progression as well as response and resistance to endocrine therapy. No mouse models that fully mimic the human disease are available, however rat mammary tumor models pose a promising alternative to overcome this limitation. Compared to mice, rats are more similar to humans in terms of mammary gland architecture, ductal origin of neoplastic lesions and hormone dependency status. Moreover, rats can develop spontaneous or induced mammary tumors that resemble human HR+ BC. To date, six different types of rat models of HR+ BC have been established. These include the spontaneous, carcinogen-induced, transplantation, hormone-induced, radiation-induced and genetically engineered rat mammary tumor models. Each model has distinct advantages, disadvantages and utility for studying HR+ BC. This review provides a comprehensive overview of all published models to date.

Targeting hormone-resistant breast cancer cells with docetaxel: a look inside the resistance

Aim: The study aims to analyze the effect of long-term incubation of ERα-positive MCF7 breast cancer cells with 4-hydroxytamoxifen (HT) on their sensitivity to tubulin polymerization inhibitor docetaxel. Methods: The analysis of cell viability was performed by the MTT method. The expression of signaling proteins was analyzed by immunoblotting and flow cytometry. ERα activity was evaluated by gene reporter assay. To establish hormone-resistant subline MCF7, breast cancer cells were treated with 4-hydroxytamoxifen for 12 months. Results: The developed MCF7/HT subline has lost sensitivity to 4-hydroxytamoxifen, and the resistance index was 2. Increased Akt activity (2.2-fold) and decreased ERα expression (1.5-fold) were revealed in MCF7/HT cells. The activity of the estrogen receptor α was reduced (1.5-fold) in MCF7/HT. Evaluation of class III β-tubulin expression (TUBB3), a marker associated with metastasis, revealed the following trends: higher expression of TUBB3 was detected in triple-negative breast cancer MDA-MB-231 cells compared to hormone-responsive MCF7 cells (P < 0.05). The lowest expression of TUBB3 was found in hormone-resistant MCF7/HT cells (MCF7/HT < MCF7 < MDA-MB-231, approximately 1:2:4). High TUBB3 expression strongly correlated with docetaxel resistance: IC₅₀ value of docetaxel for MDA-MB-231 cells was greater than that for MCF7 cells, whereas resistant MCF7/HT cells were the most sensitive to the drug. The accumulation of cleaved PARP (a 1.6-fold increase) and Bcl-2 downregulation (1.8-fold) were more pronounced in docetaxel-treated resistant cells (P < 0.05). The expression of cyclin D1 decreased (2.8-fold) only in resistant cells after 4 nM docetaxel treatment, while this marker was unchanged in parental MCF7 breast cancer cells. Conclusion: Further development of taxane-based chemotherapy for hormone-resistant cancer looks highly promising, especially for cancers with low TUBB3 expression.

Introduction: Cancer Systems and Integrative Biology

The insights provided by the holistic approaches of systems and integrative biology offer a means to address the multiple levels of complexity evident in cancer biology. Often focused on the use of large-scale, high-dimensional omics data for discovery in silico, integration with lower-dimensional data and lower-throughput wet laboratory studies allows for the development of a more mechanistic understanding of the control, execution, and operation of complex biological systems. While no single volume can cover all of the advances across this broad and rapidly developing field, we here provide reviews, methods, and detailed protocols for several state-of-the-art approaches to probe cancer biology from an integrative systems perspective. The protocols presented are intended for easy implementation in the laboratory and often offer a clear rationale for their development and application. This introduction provides a very brief description of systems and integrative biology as context for the chapters that follow, with a short overview of each chapter to allow the reader to easily and quickly find those protocols of most interest.

Upregulation of the EGFR/MEK1/MAPK1/2 signaling axis as a mechanism of resistance to antiestrogen‑induced BimEL dependent apoptosis in ER+ breast cancer cells

The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimEL‑dependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the pro‑apoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL pro‑apoptotic action in an antiestrogen‑resistant breast cancer cell model. In addition, the present study identified a pro‑survival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogen‑resistant breast cancer cells survive EGFR targeting by pro‑survival autophagy. These pre‑clinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and pro‑survival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimEL‑dependent apoptosis.

Extra-Virgin Olive Oil and Its Minor Compounds Influence Apoptosis in Experimental Mammary Tumors and Human Breast Cancer Cell Lines

Simple Summary

Breast cancer is a disease influenced by dietetic factors, such as the type and amount of lipids in a diet. In this work, we aimed to elucidate the different effects of two high-fat diets on the histopathological and molecular characteristics of mammary tumors in an experimental model. Animals fed with a diet high in extra-virgin olive oil (EVOO), compared to those fed with a diet high in seed oil, developed tumors with less aggressiveness and proliferation. Tumor molecular analyses of several cell death pathways also suggested an effect of EVOO in this process. In vitro experiments indicated the role of EVOO minor compounds on the effects of this oil. Obtaining insights into the influence and the mechanisms of action of dietary compounds are necessary to understand the relevance that dietetic habits from childhood may have on health and the risk of disease.

Abstract

Breast cancer is the most common malignancy among women worldwide. Modifiable factors such as nutrition have a role in its etiology. In experimental tumors, we have observed the differential influence of high-fat diets in metabolic pathways, suggesting a different balance in proliferation/apoptosis. In this work, we analyzed the effects of a diet high in n-6 polyunsaturated fatty acids (PUFA) and a diet high in extra-virgin olive oil (EVOO) on the histopathological features and different cell death pathways in the dimethylbenz(a)anthracene-induced breast cancer model. The diet high in n-6 PUFA had a stimulating effect on the morphological aggressiveness of tumors and their proliferation, while no significant differences were found in groups fed the EVOO-enriched diet in comparison to a low-fat control group. The high-EVOO diet induced modifications in proteins involved in several cell death pathways. In vitro analysis in different human breast cancer cell lines showed an effect of EVOO minor compounds (especially hydroxytyrosol), but not of fatty acids, decreasing viability while increasing apoptosis. The results suggest an effect of dietary lipids on tumor molecular contexts that result in the modulation of different pathways, highlighting the importance of apoptosis in the interplay of survival processes and how dietary habits may have an impact on breast cancer risk.

Atlas of Lobular Breast Cancer Models: Challenges and Strategic Directions

Invasive lobular carcinoma (ILC) accounts for up to 15% of all breast cancer (BC) cases and responds well to endocrine treatment when estrogen receptor α-positive (ER+) yet differs in many biological aspects from other ER+ BC subtypes. Up to 30% of patients with ILC will develop late-onset metastatic disease up to ten years after initial tumor diagnosis and may experience failure of systemic therapy. Unfortunately, preclinical models to study ILC progression and predict the efficacy of novel therapeutics are scarce. Here, we review the current advances in ILC modeling, including cell lines and organotypic models, genetically engineered mouse models, and patient-derived xenografts. We also underscore four critical challenges that can be addressed using ILC models: drug resistance, lobular tumor microenvironment, tumor dormancy, and metastasis. Finally, we highlight the advantages of shared experimental ILC resources and provide essential considerations from the perspective of the European Lobular Breast Cancer Consortium (ELBCC), which is devoted to better understanding and translating the molecular cues that underpin ILC to clinical diagnosis and intervention. This review will guide investigators who are considering the implementation of ILC models in their research programs.