Extra-cellular exosomes may have the role of a carrier in transferring molecules from the tumor micro-environment to the unaffected cells in breast cancer tumors.

Background: Breast cancer is recognized as a major clinical challenge in gynecological diseases worldwide. Exosomes are small vesicles derived from multicellular bodies that are secreted by many cells into the extracellular environment and thus participate in intercellular communication through the transfer of genetic information such as encoded and non-encoded RNAs to target cells. Tumor-derived exosomes are thought to be a rich source of microRNAs (miRNAs) that can regulate the function of other cancer cells in the tumor microenvironment. However, the exact mechanisms by which tumor cell-derived exosomes affect their neighboring cells, as well as the biological function of exosomal miRNAs in receptor cells, are not well understood.

Materials and methods: In this study, after overexpression of miR-205 in breast cancer cells (MDA-MB-231 class), cell-derived exosomes were successfully isolated and characterized by electron microscopy and dynamic light scattering.

Results: Determination of miR-205 expression levels in exosomes secreted from engineered cells confirmed the high expression of this miRNA in exosomes. It was also found that treatment of tumor exosomes carrying this miRNA had an apoptotic induction effect and also had a significant effect on reducing the expression of Bcl-2 gene transcript in a time-dependent manner in breast cancer cells (P < 0.001).

Conclusion: Overall, this study suggests that exosomal transfer of tumor suppressor miRNAs to cancer cells could be a suitable platform for nucleic acid transfer to these cells and be highly effective in cancer treatment.