Abstract ES8-2: Exosome analysis in breast cancer: Clinical translation

Abstract

Abstract There is a growing appreciation that tumor secreted factors can function by orchestrating the cross-talk between cancer, stromal and immune cells. Tumors constitutively release membrane-derived extracellular vesicles (EVs) or exosomes that are readily detected in body fluids and have been appreciated to play important roles in signaling, immunomodulation and metastasis. We examined the role of circulating and stromal-derived EVs in hormonal therapy resistant breast cancer. We identified the full mitochondrial genome in circulating extracellular vesicles (EVs) from patients with hormonal-therapy resistant metastatic breast cancer. We generated xenograft models of hormonal therapy-resistant (HTR) metastatic disease characterized by EVs in the peripheral circulation containing mtDNA. Moreover, these human HT-resistant cells had acquired host-derived (murine) mtDNA promoting ER-independent metabolic proficiency. Functional studies identified cancer associated fibroblasts (CAF)-derived EVs (from patients and xenograft models) laden with the complete mitochondrial genome as a mediator of this phenotype. Specifically, the treatment of HT-naïve cells or HT-treated metabolically dormant populations with CAF-derived mtDNAhi EVs promoted an escape from metabolic quiescence and HTR disease both in vitro and in vivo. Moreover, this phenotype was associated with the acquisition of EV-mtDNA especially in cancer stem-like cells, expression of EV-mtRNA and restoration of metabolic activity. In addition to mtDNA, we also identified miR-221 in CAF derived EVs as a driver of HTR disease. Specifically, EV-mediated transfer of miR-221 to cancer cells and, in combination with hormone therapy, activated an ERlo/Notchhi feed-forward loop responsible for the generation of CD133hi cancer stem like cells. We further determined that the IL6-pStat3 pathway promoted the biogenesis of onco-miR-221hi CAF EVs. Our results illuminate how EV-mediated horizontal transfer of genetic material from host stromal cells to cancer cells triggers the evolution of therapy-resistant metastases, with potentially broad implications for their control. Citation Format: Bromberg JF. Exosome analysis in breast cancer: Clinical translation [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr ES8-2.