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Role of the bone marrow in breast cancer metastasis and therapy response

Applicant Hynes Nancy E.
Number 138417
Funding scheme Project funding (Div. I-III)
Research institution Friedrich Miescher Institute for Biomedical Research
Institution of higher education Institute Friedrich Miescher - FMI
Main discipline Cellular Biology, Cytology
Start/End 01.01.2012 - 31.12.2013
Approved amount 221'196.00
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All Disciplines (2)

Discipline
Cellular Biology, Cytology
Molecular Biology

Keywords (6)

bone metastasis; breast cancer; tumor environment; animal models of breast cancer; signal transduction inhibitors; "Viscious cycle"

Lay Summary (English)

Lead
Lay summary

Metastatic dissemination is the major cause of cancer associated death. Dissemination of tumor cells is a very early event in cancer progression and metastatic cells relapse even decades after the first diagnose and can show different clinical features compared to the primary disease. In breast cancer, bone, lung and brain are the major sites of tumor metastases. The “seed and the soil” theory propose that selected population of cells can spread from the primary tumor in different organs based on different requirements. Moreover, specific environments can differently influence cancer cells and affect response to therapy. For these reason it is important to investigate the role of the tumor microenvironment and to dissect the molecular cross-talk between cancer cells and the surrounding cells in the stroma. 

Bone marrow (BM) is particularly permissive for cancer dissemination thanks to environmental and structural features like the fenestration of bone sinusoidal capillaries that facilitates the entrance of circulating cells. Moreover, BM is a key reservoir for metastatic breast cancer cells. By still unknown mechanisms, tumor cells can enter into a quiescent state in the bone and remain dormant for very long periods. Regarding this, an important issue is that dormant tumors show resistance to conventional therapy that cannot target non-proliferating cells.

When tumor relapse occurs cancer cells reacquire the proliferative ability, thereby causing osteolytic lesions. During this process cancer cells secrete factors that increase recruitment and activation of osteoclasts, driving osteolysis. In turn, matrix resorption causes the release of soluble factors that sustain tumor cell proliferation and promote the progression of bone metastases, establishing the so called “vicious cycle”. Pre-clinical and clinical evidences suggest that to hit the vicious cycle is a therapeutic strategy, since agents that inhibit bone resorption, like bisphosphonates, inhibit tumor cells expansion.

We aimed to analyze molecular mechanisms involved in the interaction between tumor cells and the BM environment to identify suitable targets in the tumor cells and in the bone environment to inhibit breast cancer growth in the bone. We took advantage of an in-vivo model of bone metastases with SCP1833 subclone of MDA-MB231 breast cancer cells. This is an aggressive breast cancer model which after intra-cardiac injection has a high propensity to home and proliferate in the BM. Cancer cells were engineered to express luciferase and GFP and metastatic dissemination and proliferation was followed by in-vivo bioluminescence.

We used wide-genome approaches to investigate how breast cancer cells affect BM stoma when they home to the endosteal niche and how bone microenvironment can influence tumor cells. To analyze the effect of BM environment on disseminated tumor cells, we compared the transcriptional profile of MDA-MB231 SCP1833 from the mammary fad pad, to mimic the primary tumor, with tumor cells isolated from the BM. Importantly, thanks to GFP expression, tumor cells were directly isolated from the specific environment to be representative of the in-vivo situation. Among the different transcripts up-regulated in BM seeding tumors we focused on ID1 and ID3 as potential targets. The IDs are a family of transcription factor inhibitors that has been described to correlate with poor prognosis in breast cancer and have a role in lung metastases formation. We observed that both ID1 and ID3 are up-regulated in MDA-MB231 SCP1833 compared to the parental cell lines. Moreover, the knock-down of ID1 expression in tumor cells is sufficient to decrease the metastatic potential of MDA-MB231 1833 in-vivo. We are following up these results and we will investigate the molecular mechanism involved in ID1 and ID3 expression as well as their impact on bone marrow environment and metastatic progression.

Concomitantly we are interested in investigating potential pathways modulated in the BM environment after seeding and proliferation of tumor cells. For this purpose we compared the transcriptional profile of BM stroma from the bone of tumor bearing vs tumor free mice. Different BM cell populations were isolated by cell sorting thanks to specific markers. We excluded cells of the hematopoietic compartment from the analysis, concentrating on the CD45- population. We used the best available antibodies that define osteoblasts (CD45-, TR119- Sca1-, CD51+), endothelial cells (CD45-, TR119-, Sca1+, CD31+) and mesenchymal progenitors (CD45-, TR119-, CD31-, Sca-1+). Microarray analysis revealed that BM is strongly affected by breast cancer cell dissemination. Indeed, several components of key molecular pathways involved in tumor development (including TGFBR, PDGFRB, EGFR, HGFR and JAK-STAT signaling pathways) are modulated in the BM environment of mice with tumor cells. We are following up this analysis by testing different small molecule inhibitors to block specific pathways in bone marrow metastases.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
5th International Conference on Tumor Microenvironment and Angiogenesis Poster 02.06.2013 Ascona, Switzerland Bottos Alessia;
AACR Annual Meeting Poster 31.03.2012 Chicago, IL, United States of America Bottos Alessia; Hynes Nancy E.;


Associated projects

Number Title Start Funding scheme
149751 Role of the bone marrow niche in breat cancer metastasis and therapy response 01.01.2014 Project funding (Div. I-III)

Abstract

SUMMARY of the research plan:“Role of the bone marrow niche in breast cancer metastasis and therapy response”Metastatic spread of tumor cells is the major cause of cancer-associated deaths. Latent metastasis, leading to late-onset relapse, occurs frequently in breast cancer. The majority of these metastases arise in the bone, and subsequently in other organs. At this stage the disease is virtually incurable. The tumor microenvironment (niche) plays an important role in regulating tumor growth at primary sites and, likewise, a receptive microenvironment is required for malignant cells to engraft distant tissues. This project addresses the role of bone marrow (BM) in metastatic breast carcinoma spread. BM is a fenestrated organ, with sinusoid capillaries permissive to hematopoietic cells, which migrate to the periphery to maintain blood homeostasis. This permissiveness for natural trafficking is thought to allow the infiltration of BM with disseminating carcinoma cells, and to contribute to formation of dormant metastatic niches. We hypothesize that tumor niches facilitate survival of carcinoma in the BM and also protect cancer cells from therapeutic interventions, ultimately facilitating progress to an incurable phase. This project will investigate the interactions between breast carcinoma cells and the BM with the following goals:(1) Characterization of the BM niche in mice carrying mammary carcinoma:The proposed experiments will establish mammary carcinoma models, representing common breast cancer sub-types, which have BM tropism. The impact of BM metastases on the cellular components of the BM niche will be analyzed by FACS and IHC, thereby characterizing properties of stromal sub-populations and identifying alterations specific for the carcinoma-bearing models. These experiments will uncover the cellular niche constituents that are altered by carcinoma and that potentially contribute to cancer survival in the bone/BM environment. (2) Investigation of the role of the BM niche in tumor response to anti-cancer therapies:Mammary carcinoma that resides in the BM niche may be less sensitive to and/or evade anti-cancer treatments. We will make use of compounds known to promote exit of hematopoietic cells from quiescent niches and investigate their effect on mammary carcinoma cells in the BM, and at distant sites. We aim to identify treatment strategies for activating the potentially dormant tumor cells in the BM niche to render them more sensitive to anti-cancer therapies, that will include tyrosine kinase inhibitors and endocrine agents. (3) Identification of the molecular mechanisms contributing to mammary carcinoma-BM niche interactions:We will identify the signaling events between the BM microenvironment and tumors with BM tropism, which support the survival of disseminated mammary carcinoma. The experiments will be based on expression profiling (transcriptome, cytokines and extracellular matrix protein components) of tumor cells and of BM stroma affected by tumor presence. The analysis will be performed with mammary carcinoma models (characterized in Aim 1) and with primary human tissue from carcinoma patients, consisting of paired samples of malignant breast and cancer-containing BM biopsies. In summary, the proposed experiments are novel and are aimed at advancing our knowledge on mechanisms that control metastatic tumor cell survival and that contribute to targeted therapy resistance. These two questions are currently of the utmost relevance for improving patient treatment and outcome.
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