UC Merced

Breast cancer is the most common cancer in women and 1 in 8 women nationally will develop this disease in their lifetime. Preclinical cancer models have driven novel therapeutic regimens over the last half century yielding progressively improved survival yet 95% of new anticancer drugs will fail in clinical trials and greater than 42,000 people will still succumb to this disease per year. This research focuses on characterization of triple negative breast cancer (TNBC), a clinically difficult form of breast cancer characterized by lack of targetable receptors, advanced diagnosis, and increased aggressiveness, towards identification of current limitations and future direction for optimized preclinical models.

Transcriptional profiling of 4T1, a murine TNBC cell line, at the bulk and single cell level were utilized to culture induced alterations of tumor cells cultured in vitro, in vivo, and ex vivo. Flow cytometric analysis was also used to validate and further the molecular alterations imparted on cancer cells. Furthermore, proteomic and transcriptomic analysis of cancer derived exosomes was performed to identify biomarkers of cancer behavior.

I was able to identify in vitro culturing induced behavioral bias towards proliferative behavior while in vivo conditions favored cell signaling and cancer progressive biological processes such as a transition from epithelial to mesenchymal cell states. Non-cancer stromal cells were also proven to be an essential component for clinical cancer behavior recapitulation in vitro. This key finding was then followed by examination of heterogenous ex vivo tumor cell cultures utilizing numerous culturing techniques finding that retention of not only tumor cell populations, but spatial organization and extracellular matrix composition retention is optimal for native cancer behavior recapitulations. Additionally, TNBC stromal cell effects on chemotherapeutic sensitivity were found to play a significant role towards inhibiting tumor growth. IL17A secreted from γδ T cells are capable of increasing cancer cell sensitivity to Doxorubicin and increased efficacy of antitumor cytotoxic T cell populations. Furthermore, human cancer exosomes derived from cultured cells discovered putative biomarkers of cancer subtypes that were validated with clinical data sets to identify 2 exosomal miRNA (hsa-mir-375, hsa-mir-138-1) and 2 protein biomarkers (FBP1, HLA-A) were found to correlate to breast cancer subtype and aggressiveness.

In summation, the tumor microenvironment is a complex and dynamic tissue to recapitulate under in vitro conditions, multiple effects and approaches have been identified in this work to serve as a basis for future pre-clinical approaches.