Abstract

Introduction Breast cancer is the most deadly female cancer worldwide; however, therapies today are insufficient to eradicate this disease due to tumor heterogeneity. Our group has proposed a new therapeutic target corresponding to a family of long non-coding mitochondrial RNAs (ncmtRNAs) called Sense (SncmtRNAs) and Antisense (ASncmtRNAs). Knockdown of ASncmtRNAs causes massive and selective cell death in tumor cells but not in normal cells. During intercellular communication, cells release extracellular vesicles such as exosomes that contain proteins and RNAs with the potential to influence recipient cells’ proliferation and/or trigger apoptosis. This work proposes that exosomes released post-knockdown of ASncmtRNAs have the ability to modulate tumorigenic properties of the human breast cancer cell line MDA-MB-231 in vitro. Methodology MDA-MB-231 cells were transfected with a therapeutic antisense oligonucleotide (ASO-T) complementary to ASncmtRNA or a non-related ASO (ASO-NR) using Lipofectamine2000. At 24h post-transfection exosomes were purified from supernatants using Exo-spin. Microparticle size and distribution was determined by transmission electron microscopy (TEM) and Nanosight analysis. Exosome markers Alix, TSG101 and CD63 were detected by Western blotting. Tumorigenic properties such as invasion and anchorage-independent growth were analyzed. Results Nanosight and TEM revealed exosomes ranging from 50-120 nm in size. Exosomes released from ASO-T-treated cells contained the exosome markers described above, with some differences in their expression. Invasiveness was inhibited in cells treated with exosomes derived from ASO-T-treated cells, compared to controls. Conclusions These results suggest that exosomes released post-knockdown of ASncmtRNAs regulate tumorigenic properties in vitro, due to their content. Acknowledgements: FONDECYT 11140204, BASAL PFB-16.