Research Grants Awarded
Targeting Inflammation In Breast Cancer
Career Catalyst Research
Inflammation within the tumor microenvironment correlates with increased invasiveness and poor prognosis in many types of cancer, including breast cancer. Inflammation is mediated by the production of cytokines, which can be secreted by breast cancer cells, stromal cells or infiltrating immune cells. Inflammatory cytokines promote proliferation, genotoxic stress, angiogenesis and immune tolerance, which are all processes that contribute to breast cancer progression. The inflammatory cytokine interleukin-1beta (IL-1beta) has gained recent attention due to its association with invasive breast cancer. Higher levels of IL-1beta expression are found in invasive breast cancer cell lines and carcinomas, and increased serum levels of IL-1beta correlate with recurrence in breast cancer patients. These observations suggest that targeting IL-1beta activity in breast cancer patients may reduce the formation of invasive lesions. Antagonists of the IL-1 receptor (IL-1R) are currently being used in a clinical setting to relieve symptoms of rheumatoid arthritis. Therefore, using IL-1R antagonists to inhibit breast cancer progression is an attractive possibility because patients can clearly tolerate these drugs.
We have previously demonstrated that inflammatory cells, specifically macrophages, are required for the formation of early stage mammary lesions in a novel mouse model of mammary tumorigenesis. These mice express a chemically inducible fibroblast growth factor receptor-1 (FGFR1) transgene in the mammary epithelium that is activated following systemic administration of a synthetic dimerizer drug, resulting in the formation of mammary tumors. The inducible nature of this mouse model provides a unique model in which to study different stages of mammary tumorigenesis, from the initial development of hyperplastic lesions to the formation of mammary tumors. Gene expression studies of early stage mammary lesions from these mice demonstrated that activation of FGFR1 resulted in a dramatic inflammatory response within the mammary gland. Specifically, we have observed increased levels IL-1beta expression in mammary epithelial cells following activation of FGFR1. Inhibition of IL-1beta activity in vivo resulted in reduced epithelial proliferation and decreased expression of downstream inflammatory markers. Interestingly, these data demonstrate that targeting IL-1beta partially inhibits the formation of early mammary lesions, despite the continued activation of FGFR1 within the epithelial cells.
In addition to the transgenic mouse model, we have established cell culture models to delineate the mechanisms of cross-talk between mammary epithelial cells and macrophages that are involved in promoting tumor formation. Our preliminary studies suggest that FGFR1-induced IL-1beta activates IL-1 receptor (IL-1R) signaling within both mammary epithelial cells and macrophages. Based on our preliminary data, we hypothesize that activation of IL-1R mediates cross-talk between mammary epithelial cells and inflammatory cells to promote FGFR1-induced epithelial cell proliferation and invasion in vitro and the formation of hyperplastic lesions in vivo. To test this hypothesis, we propose the following specific aims:
Specific Aim 1: To define the mechanisms by which IL-1R activation mediates stromal-epithelial cross-talk to affect FGFR1-induced MEC proliferation and invasion in vitro and the formation of hyperplastic lesions in vivo. We have developed a model of heterotypic three-dimensional cell culture using primary mammary epithelial cells and bone marrow derived macrophages that will be used to define the mechanisms by which IL-1R activation in different cell types, specifically mammary epithelial cells and macrophages, promote mammary epithelial cell proliferation and invasion in vitro. Furthermore, we will use transplantation assays to evaluate the ability of IL-1R activation in different cell types, including mammary epithelial cells and leukocytes, to promote the formation of iFGFR1-induced proliferative lesions in vivo. We expect that IL-1R activation in mammary epithelial cells vs. macrophages will provide different contributions to the formation of proliferative lesions. Elucidating these mechanisms will enhance our understanding of stromal-epithelial interactions that could eventually be used design novel therapeutic strategies.
Specific Aim 2: To evaluate the ability of systemic administration of the IL-1R antagonist to inhibit the formation of FGFR1-induced proliferative lesions in vivo. For these studies, we will determine the effects of the IL-1R antagonist, which is currently in use clinically to treat inflammatory diseases, on the formation of FGFR1-induced proliferative lesions. We expect that inhibition of IL-1R activity will inhibit FGFR1-induced proliferation, inflammation and angiogenesis in vivo. These studies would provide preliminary evidence that an IL-1R antagonist may represent a novel therapy for breast cancer patients with high levels of IL-1beta expression.
Understanding the mechanisms by which inflammatory mediators such as IL-1beta mediate tumor promotion will ultimately lead to the development of novel therapies that target inflammation, which can then be used in combination with agents that target oncogenic changes within the breast cancer cells to more effectively combat breast cancer. Furthermore, the identification of a novel breast cancer therapy that can be used in conjunction with other general and targeted therapies and is known to be tolerated by patients would be a substantial advance in the reduction of breast cancer mortality.
The formation of a breast tumor is the result of a complex interplay between breast cancer cells and cells in the environment surrounding the tumor, called the stroma. While some of the therapies that specifically target breast cancer cells have been successful in the clinic, it is widely recognized that multi-targeted approaches that inhibit both the cancer cells and pro-tumorigenic elements within the stroma may provide more effective cancer therapies. We have used a mouse model of mammary tumor formation to examine how activation of a growth factor signaling pathway within epithelial cells results in tumor-promoting changes in the stroma. Specifically, our studies have demonstrated that activation of fibroblast growth factor receptor-1 (FGFR1), which is a protein that has recently been linked to promotion of human breast cancer, in mammary epithelial cells results in the secretion of a number of proteins into the stroma. Many of these secreted proteins, such as interleukin-1 beta (IL-1beta), are potential mediators of breast cancer progression. IL-1beta is normally secreted from cells associated with the immune system to promote inflammation in response to tissue damage or infection. Recent studies have demonstrated that inflammation is contributes to the formation and progression of breast cancer, which has generated substantial interest in examining the roles of inflammatory mediators in breast cancer initiation and progression. Specifically, studies of IL-1beta in breast cancer tissues have revealed that IL-1beta expression, which is found in 90% of estrogen-receptor negative breast carcinomas, correlates with increased tumor invasiveness. In addition, IL-1beta levels in serum of breast cancer patients correlate with poor prognosis. Based on these promising observations, it has been suggested that inhibition of IL-1beta activity may represent a novel breast cancer therapy useful for patients with high levels of tumor- or serum-associated IL-1beta. Importantly, IL-1beta has also been linked to other diseases, including rheumatoid arthritis, and antagonists of IL-1 signaling are currently being used in the clinic to treat this disease. Therefore, this systemic therapy is already known to be well-tolerated by patients. However, the mechanisms of IL-1beta action on promoting breast cancer and the effectiveness of inhibiting IL-1beta during breast cancer progression have not been extensively studied.
We have used both cell culture lines and the FGFR1 mouse mammary tumor model to examine IL-1beta function during the initiation and promotion of early stage breast lesions. Our preliminary studies suggest that following induction by FGFR1, IL-1beta interacts with both the epithelial cells, which eventually give rise to the tumor cells, as well as on immune cells associated with the stroma. Based on these results, we hypothesize that FGFR1-mediated induction of IL-1beta acts on both epithelial cells and stromal cells to induce inflammation within the mammary gland, which promotes the formation of mammary tumors. The studies outlined in this proposal will examine the effects of IL-1beta-induced signaling in different cell types associated with tumor formation, including epithelial cells and host immune cells. Furthermore, we propose to utilize our transgenic mouse model to determine the effectiveness of IL-1beta inhibitors as anticancer agents during different stages of mammary tumor formation. The identification of a novel breast cancer therapy that can be used in conjunction with other general and targeted therapies and is already known to be tolerated by patients would be a substantial advance in the reduction of breast cancer mortality.