DOI
https://doi.org/10.25772/M5KJ-MB68
Author ORCID Identifier
https://orcid.org/0000-0002-6284-4933
Defense Date
2020
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Clinical and Translational Sciences
First Advisor
J. Chuck Harrell
Abstract
Triple-negative breast cancer (TNBC) is a clinically aggressive disease that is associated with bleak outcomes due to its metastatic propensity, frequent failure to respond to chemotherapy, and lack of alternative treatment options. Despite decades of major translational research efforts, there has been very little success thus far in the development of effective targeted therapies for this disease. It is imperative to develop novel therapeutic strategies to improve patient outcomes, as well as minimize the toxicity associated with standard-of-care chemotherapeutics. Given that metastatic disease accounts for the vast majority of TNBC-related deaths, a better understanding of therapeutic responses within common sites of metastasis is crucial for developing effective treatment strategies. Given the molecular heterogeneity of TNBC, the clinical success of new therapies additionally depends on the identification of reliable drug targets within each TNBC subtype for more effective patient stratification. The studies presented herein sought to address these matters, using clinically relevant patient-derived xenograft (PDX) models to characterize chemotherapeutic efficacy in distinct metastatic sites, to identify promising targeted therapeutic candidates and combination strategies, and to assess the translational potential of these therapeutic strategies, with a focus on both the basal-like and luminal androgen receptor (LAR) subtypes of TNBC. We hypothesized that therapeutic efficacy in the primary tumor setting would be maintained in the metastatic setting, and that PDXs of distinct TNBC subtypes would respond to particular targeted therapies based on the distinct molecular pathways that drive their progression. We therefore expected that therapies targeting the epidermal growth factor receptor (EGFR) and the androgen receptor (AR) would have efficacy in basal-like TNBC and LAR TNBC, respectively, and would be ideal for incorporation into novel combination regimens for these specific disease subtypes. Using a combination of in vitro and in vivo drug response studies, we identified a drug combination, co-targeting EGFR and survivin, that was synergistic across multiple PDX models of basal-like TNBC, despite some of these models responding differently to standard chemotherapies, thus revealing potential pathways that may serve as reliable drug targets in this subset of patients. Furthermore, we identified several potential drug targets and therapeutic candidates for combination with AR-targeted therapies in LAR TNBC. In addition to identifying novel therapeutic strategies that have potential to provide clinical benefit for these subsets of TNBC patients, these studies highlight the utility of PDX models for in vitro and in vivo drug development studies, and demonstrate that the molecular and drug response profiles of primary tumors are maintained in the metastatic setting, indicating that studies employing PDX mammary tumor models can be applicable in advanced disease. Collectively, the data generated in these studies have the potential not only to directly provide clinical benefit for TNBC patients, but also to inspire and inform countless future research endeavors seeking to improve the therapeutic landscape in breast cancer.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
3-2-2020