Over 40,000 American women died of breast cancer last year and more than 190,000 new cases were diagnosed, highlighting the health concern this disease still poses to American women. There are three subclassifications of breast cancer based upon receptor status, estrogen receptor (ER) positive, human epidermal growth factor 2 receptor (HER2)-amplified, or triple-negative (ER-negative, progesterone negative, and HER2 normal). Based upon these classifications, patients may be eligible for targeted chemotherapy. Therapies targeting ER are widely applied and include selective estrogen receptor modulators (SERM) such as tamoxifen (TAM), a selective ER downregulator like Faslodex (FAS, fulvestrant, ICI 182,780), or one of the third-generation aromatase inhibitors (AI) including letrozole or anastrozole. Antiestrogens are less toxic than cytotoxic chemotherapy, and TAM has represented the "gold standard" in first-line endocrine therapy for over 30 years. However, these treatments have limitations and adverse side effects that hinder their use; ER-targeted drugs such as tamoxifen or Faslodex may be ineffective due to drug resistance. This suggests the need for additional targeted therapies for the treatment of ER-positive breast cancer. These data highlight the need for new therapeutic options to treat or sensitize tumors that are resistant to endocrine therapy.

This proposal investigates the role of glucose regulated protein 78 (GRP78), a molecular protein chaperone in the endoplasmic reticulum (EnR), in antiestrogen-resistant breast cancer. GRP78 is a key regulator of the unfolded protein response (UPR), a pathway stimulated in the presence of unfolded proteins within the EnR, in endocrine therapeutic resistance. Our group has recently shown increased UPR signaling components expressed in antiestrogen-resistant breast cancer, highlighting the possible importance of this pathway in endocrine resistance. In this application, I will explore the effect of UPR and GRP78 on antiestrogen resistance and epithelial to mesenchymal transition (EMT). EMT is a cellular process by which cells undergo a phenotypic switch from an epithelial-like (differentiated) to mesenchymal-like (undifferentiated). The process of EMT has been postulated to play a role in therapeutic resistance along with progression of cancer and metastases. I propose that antiestrogen therapy induce UPR signaling, thereby triggering an EMT to promote endocrine resistance and survival. Experiments proposed in this application include modulating GRP78 in various different breast cancer cell lines and investigating the molecular mechanisms of antiestrogen resistance in vitro and in an in vivo orthotopic murine model. This application explores the possibility of combining focal adhesion kinase (FAK) inhibitors (to target EMT) and antiestrogen drugs to restore antiestrogen sensitivity and therefore has high clinical translational potential. These studies will further the understanding of the molecular pathways of endocrine resistance leading to rational drug combinations to resensitize/prevent resistant phenotypes, enabling better breast cancer patient treatment and care.

The proposed training program supports my career goals to become an independent researcher devoted to the field of breast cancer. The training program consists of three phases. Phase I of the program involves the continuation of my education through attending seminars, auditing relevant courses, and improvement of my technical skills. This training program was specifically designed to teach new experimental techniques such as magnetic resonance imaging to investigate the effect of GRP78 and drug treatment on tumor vasculature. In Phase II, I will present my work at national and international conferences along with further honing of my writing skills to increase my publishing credentials. In the past year I have submitted abstracts to two accredited meetings, the Keystone symposium on Autophagy and Experimental Biology. I have already directly contributed to two reviews and a book chapter, highlighting the benefit of the collaborative attitude of our group. The third phase of the proposed training program involves taking specific teaching courses offered by Georgetown University and the National Institutes of Health. These courses are geared toward improving researchers' teaching skills to become proficient in teaching undergraduate students basic science courses and spark the interest of the next generation of breast cancer researchers. In addition, this phase of the training plan involves the mentoring of an undergraduate or a first or second year medical/graduate student in the skills necessary to succeed in science. Phase III, under the direct guidance of my mentor, involves the transition from postdoctoral fellow to faculty through writing independent grants such as a K99/R00 or a Susan G. Komen Cancer Catalyst Research Grant. The training program described in this application is designed to promote my development into an independent breast cancer researcher.