Inhibition of MiR-155 Using Exosomal Delivery of Antagomir Can Up-Regulate PTEN in Triple Negative Breast Cancer

Background: The most aggressive form of breast cancer (BC) is Triple-Negative BC (TNBC), with the poorest prognosis, accounting for nearly 15% of all cases. Since there is no effective treatment, novel strategies, especially targeted therapies, are essential to treat TNBC. Exosomes are nano-sized microvesicles derived from cells and transport various intracellular cargoes, including microRNAs (miRNAs). MiRNAs, small non-coding RNA, are an influential factor in the development of cancerous transformations in cells. Methods: Bioinformatics analysis of genes related to TNBC revealed that PTEN plays a crucial role in the disease. Relative expression of this gene was analyzed with RT-qPCR in 14 TNBC clinical samples. Electroporation was used to load miRNA antagomir into exosomes extracted from the conditioned medium. Then, the expression of miR-155 and PTEN was evaluated in MDA-MB-231 cells treated with antagomir-loaded exosomes. Results: Based on the bioinformatics analysis, miR-155 is a potent inhibitor of PTEN. Following treatment with antagomir-loaded exosomes, RT-qPCR showed significantly reduced miR- 155 and increased PTEN levels in MDA-MB-231 cells. Conclusion: Based on the results of this study, exosomes can be effectively used as a cargo of oligonucleotides like miRNA mimics and antagomirs in targeted therapies.