Novel Approach to Analyze Estrogen Action in Breast Cancer

Institution: La Jolla Institute for Molecular Medicine
Investigator(s): Brian Eliceiri, Ph.D. -
Award Cycle: 2005 (Cycle 11) Grant #: 11IB-0079 Award: $310,950
Award Type: IDEA
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease



Initial Award Abstract (2005)
Estrogen is known to promote mammary tumor growth by inducing cell proliferation through specific estrogen receptors (ERs) and associated signaling pathways. Anti-estrogen therapy is an effective component of treatment for ER-positive breast cancers and is assumed to work by blocking estrogen-induced cancer cell division. Little consideration has been given to the possibility that estrogen influences the host tissues, for example the blood vessels, to promote tumor metastasis independent of effects on the tumor cells themselves.

We intend to test our novel hypothesis that estrogen promotes metastasis of mammary carcinomas through actions on host tissues rather than direct actions on the cancer cells. Furthermore, we propose that the host tissue responds to estrogen involve the vascular system and, thereby, enhance the intravasation (i.e., entry of cancer cells into the blood) of cells from the primary tumor and/or extravasation of cells to distant organ metastatic sites. We have identified mouse mammary carcinoma cells that do not respond to estrogen by increasing cell division. Confirmation of the lack of estrogen-induced cancer cell response (e.g., proliferation, migration, Erkl/2 phosphorylation) will be done using cell lines. For whole animal studies, we will manipulate estrogen levels in mice by removing the ovaries and adding back estrogen to half the mice by implanting a slow-release estrogen pellet. Spontaneous metastasis assays will be performed to analyze dissemination of tumors from the mammary fat pad site of implantation to the lung and this will be compared with experimental metastasis assays. We will document increased invasiveness of primary tumors using confocal microscopic imaging of tumors grown from fluorescently labeled mammary carcinoma cells. Finally, we will examine the impact of estrogen on MMPs and fibrinogen deposition in the vasculature of the primary and metastatic tumor sites. We predict that the number and size of metastatic foci will increase in the presence of estrogen but that the size of the primary tumors will not differ in the presence of estrogen.

We intend to test a novel and important hypothesis that estrogen may have deleterious actions in promoting breast cancer without influencing the cancer cells directly. If our hypothesis is correct, results of this project would have significant implications for the treatment of both ER-positive and ER-negative breast cancers. We also plan to employ and perfect novel microscopic imaging techniques for the study of metastasis of tumor cells that will be extremely useful for future research on mechanisms of breast cancer metastasis.


Final Report (2006)
Estrogen hormones promote breast cancer tumor growth by inducing cell division through specific cellular receptors. Therefore, anti-estrogen therapy is a prominent and effective component of treatment for estrogen receptor-positive breast cancers and is thought to work by blocking estrogen-induced cancer cell division. Little consideration has been given to the possibility that estrogen influences the host tissues to promote tumor metastasis independent of effects on the tumor cells themselves. We have tested our hypothesis that estrogen promotes metastasis of breast cancer cells through actions on host tissues rather than direct actions on the cancer cells. We identified a breast cancer cell line that does not respond to estrogen. We injected these cells into mice with very low estrogen levels and mice with normal levels of estrogen, and found that the presence of estrogen promoted metastasis of the tumor cells to the lungs. We control the estrogen levels in the mice by removing the ovaries, the organs that produce most estrogen, and implanting slow-release estrogen pellets in half the mice. The innovation of this project is two-fold. First, we are testing a novel and important hypothesis that estrogen produced from the ovaries or taken in hormone supplements may have deleterious actions in promoting breast cancer metastasis independent of whether the cancer cells are responsive to estrogen. We believe that these results could have significant implications for the treatment of estrogen receptor-negative breast cancers. Second, we have employed novel imaging techniques for the visualization of tumor cell metastasis. This technique, once optimized, should be of great use to other researchers. The implications of our hypothesis regarding estrogen promotion of cancer metastasis are of critical importance to the clinical treatment of breast cancer and to the advocates of breast cancer research. Our findings could impact the treatment of pre- menopausal vs. peri-menopausal vs. menopausal women with estrogen-dependent and estrogen independent tumors. Finally, through our outreach program, "Innovations in Women's Health Research" (www.ljimm.org/innovations/), we are increasing public awareness of women's health issues including breast cancer.

Note: the following technical description of this project was reported by the PI and colleagues in Cancer Research (2006) 66(7):3667-72. Direct proliferative effects of estrogen (E(2)) on estrogen receptor-positive tumors are well documented; however, the potential for E(2) to mediate effects selective for the host (i.e., angiogenesis, vascular permeability, or stromal effects), which influence tumor growth and/or metastasis, has received less attention. In this study, we examine the capacity for E(2) to promote tumor growth and/or metastasis independent of direct effects on tumor cells. In these studies, we distinguish host versus tumor compartment components of E(2) action in tumor growth and metastasis by analysis of E(2)-non-responsive tumor cells implanted in ovariectomized (OVX) mice that contain s.c. implants of placebo (OVX) or E(2)-containing slow-release pellets (OVX + E(2)). We show that the D121 lung carcinoma cell line is E(2)-non-responsive, and following s.c. implantation in OVX versus OVX + E(2) mice, E(2) action on the host compartment leads to an increase in spontaneous metastasis but not primary tumor growth or neovascularization. Similarly, experimental lung metastasis of E(2)-non-responsive 4T1 mammary carcinoma cells also leads to increased tumor burden in the lungs of OVX + E(2) mice. These results suggest that the E(2) status of the host compartment influences late steps in tumor cell metastasis that can provide important insights into the role of E(2) in the tumor versus host compartments.


Symposium Abstract (2005)
Estrogen is known to promote mammary tumor growth by inducing cell proliferation through specific estrogen receptors (ERs) and associated signaling pathways. Anti-estrogen therapy is an effective component of treatment for ER-positive breast cancers and is assumed to work by blocking estrogen-induced cancer cell division. Little consideration has been given to the possibility that estrogen influences the host tissues, for example the blood vessels, to promote tumor metastasis independent of effects on the tumor cells themselves.

We intend to test our novel hypothesis that estrogen promotes metastasis of mammary carcinomas through actions on host tissues rather than direct actions on the cancer cells. Furthermore, we propose that the host tissue responds to estrogen involve the vascular system and, thereby, enhance the intravasation (i.e., entry of cancer cells into the blood) of cells from the primary tumor and/or extravasation of cells to distant organ metastatic sites. We have identified mouse mammary carcinoma cells that do not respond to estrogen by increasing cell division. Confirmation of the lack of estrogen-induced cancer cell response (e.g., proliferation, migration, Erk1/2 phosphorylation) will be done using cell lines. For whole animal studies, we will manipulate estrogen levels in mice by removing the ovaries and adding back estrogen to half the mice by implanting a slow-release estrogen pellet. Spontaneous metastasis assays will be performed to analyze dissemination of tumors from the mammary fat pad site of implantation to the lung and this will be compared with experimental metastasis assays. We will document increased invasiveness of primary tumors using confocal microscopic imaging of tumors grown from fluorescently labeled mammary carcinoma cells. Finally, we will examine the impact of estrogen on MMPs and fibrinogen deposition in the vasculature of the primary and metastatic tumor sites. We predict that the number and size of metastatic foci will increase in the presence of estrogen but that the size of the primary tumors will not differ in the presence of estrogen.

We intend to test a novel and important hypothesis that estrogen may have deleterious actions in promoting breast cancer without influencing the cancer cells directly. If our hypothesis is correct, results of this project would have significant implications for the treatment of both ER-positive and ER-negative breast cancers. We also plan to employ and perfect novel microscopic imaging techniques for the study of metastasis of tumor cells that will be extremely useful for future research on mechanisms of breast cancer metastasis.

Estrogen induces lung metastasis through a host compartment-specific response.
Periodical:Cancer Research
Index Medicus: Cancer Res
Authors: Banka CL, Lund CV, Nguyen MT, Pakchoian AJ, Mueller BM, Eliceiri BP.
Yr: 2006 Vol: 66 Nbr: 7 Abs: Pg:3667-72