Abstract 3789: Circular RNA expression is enriched in breast cancer extracellular vesicles and is associated with chemotherapy resistance

Abstract Up to 90% of failures in chemotherapy treatment are associated with metastatic-related drug resistance. Extracellular vesicles (EVs) are believed to play a role in the spread of chemotherapy resistance through the horizontal transfer of oncoproteins and noncoding RNA species, but the underlying mechanisms for this are not fully understood. Here, we study EV biogenesis, release, and uptake in the context of breast cancer chemoresistance. Specifically, we characterized the bioactive cargoes in EVs secreted by chemoresistant triple negative breast cancer cells and chemoresistant estrogen receptor-positive breast cancer cell lines. Preliminary data show that these EVs contain unusually high levels of circular RNAs, small RNA species formed covalently through backsplicing and are typically noncoding. When chemosensitive cells absorb these circRNA-enriched EVs, they experience a significant increase in resistance phenotypes. Moreover, knockdown of the circRNAs via antisense oligonucleotides results in decreased chemoresistance, suggesting a role of circRNAs in the development of chemotherapy resistance. Previous studies have shown that tumor-derived exosomal circRNAs may confer resistance by sponging microRNAs. We are exploring what the circRNAs do mechanistically to promote tumor survival, and clarifying these mechanisms as a whole will serve to potentially provide therapeutic targets against chemotherapy resistance and cancer recurrence. Citation Format: Harrison Ngue, Jitendra Shrestha, Hyejin Kim, Shobha Vasudevan. Circular RNA expression is enriched in breast cancer extracellular vesicles and is associated with chemotherapy resistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3789.