Lisa M. Arendt, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): [unreadable] This proposal describes a five year training program for the development of an academic career in biomedical sciences. This program will enhance critical skills for utilizing in vivo models as a tool for understanding complex human pathology. Dr. Linda Schuler, a recognized leader in the field of prolactin signaling, will mentor the principal investigator's scientific development. An advisory committee of highly-regarded scientists will provide guidance for this project as well as career advice. [unreadable] An estimate of 211,000 women in the United States will be diagnosed with invasive breast cancer this year. Although the focus for developing treatments has targeted hormonal signaling pathways, a critical gap exists in the knowledge of signaling cross talk among key factors that cooperate for dysregulated growth in this disease. Prolactin's (PRL) central role in mammary development, lactation, and involution has fueled interest in its signaling in breast cancer. The Schuler laboratory has generated transgenic mice that overexpress PRL under control of a mammary selective, non-hormonally responsive promoter, NRL. These mice develop mammary adenocarcinomas that are estrogen receptor alpha positive and negative, similar to human disease. Given the importance of estrogen and its receptor in the pathogenesis as well as treatment of this disease, this model is an excellent tool to study interactions between PRL and estrogen in disease development and progression. Another well-characterized mammary oncogene, transforming growth factor alpha (TGFa) has been correlated with estrogen receptor alpha negative breast tumors in humans and synergizes with PRL to induce mammary tumors in our transgenic model system. Using this model, we will investigate the hypothesis that circulating estrogen enhances the cooperative interaction of local mammary prolactin and TGFa to promote tumor development and progression. The specific aims include: 1) Examining the effect of post-pubertal ovarian estrogen on mammary lesion development, 2) Investigating the influence of estrogen on tumor progression once a lesion has developed, and 3) Identification of pathways of cooperative crosstalk among PRL, TGF alpha, and estrogen that may enhance carcinogenesis in vitro and in vivo. Together these studies will illuminate the cooperative roles of PRL, TGF alpha, and estrogen in the progression of breast cancer and could lead to useful diagnostic strategies and improved therapeutic targets. [unreadable] [unreadable] [unreadable]

Obesity has been identified as an important risk factor for postmenopausal breast cancer and is significantly correlated with diminished treatment response. It is currently not understood how inflammation within obese breast fat contributes to adipose tissue fibrosis and tumor desmoplasia. These conditions have been associated with both increased breast cancer risk and chemotherapy resistance. The long-term goal is to understand how obesity increases local and systemic inflammation leading to progression of treatment-resistant breast tumors. Preliminary studies have shown that transplant of CCL2+ breast stromal cells with transformed breast epithelial cells promoted rapid breast cancer development, with increased numbers of cancer stem-like cells (CSCs). Transient depletion of CD11b+ cells early in tumor development resulted in dramatic reductions in cancer associated fibroblasts (CAFs) and tumor growth rates. Transcriptional analysis of CD11b+ cells from both tumors and mammary glands of obese mice revealed a fibrotic gene signature and expression of platelet-derived growth factor receptor alpha (PDGFR?). This fibrotic gene signature is consistent with fibrocytes, which have attributes of both inflammatory macrophages and myofibroblasts. Based on these preliminary data, the central hypothesis is that fibrocytes are increased by obesity where they promote aggressive tumor growth and chemotherapy resistance through the expansion of CSCs via PDGFR?. This hypothesis will be tested with three specific aims: 1) Examine how fibrocytes are recruited to obese mammary fat and promote fibrosis via PDGFR?; 2) Determine how fibrocytes differentiate into CAFs and promote chemotherapeutic resistance through cancer stem-like cell (CSC) expansion; 3) Identify how obesity enhances fibrocytes in human breast tissue leading to adipose tissue fibrosis and desmoplasic, treatment-resistant breast tumors. A high fat diet model of obesity and GFP-labeled myeloid lineage cells will be used to examine differentiation of obesity-induced fibrocyte populations within the mammary gland. Gleevec, a clinical PDGFR inhibitor, will be used to target fibrocytes and reduce obesity- induced fibrosis. Using the inflammatory model of breast tumor progression, the mechanism of fibrocyte-induced tumor desmoplasia and CSCs expansion will be examined. The efficacy of Gleevec will be tested to reduce CSCs and enhance chemotherapy response. Reduction mammoplasty tissue from obese and lean women and well-annotated breast tumor tissue microarrays will be used to understand how obesity alters treatment response and tumor desmoplasia, and potentially identify patients that might benefit from adjuvant use of Gleevec for treatment of breast cancer. These studies are innovative because fibrocytes have not been investigated in the context of obesity. The impact of these studies is that targeted Gleevec therapy to treat desmoplastic tumors in obese women may significantly improve chemotherapeutic response, leading to reduced mortality. Obesity has been linked to tumor desmoplasia and treatment resistance in other cancers, and understanding the role of fibrocytes in therapy resistance may lead to broad-reaching advances for other obesity-associated cancers.