PTEN and breast carcinoma: More recently, a study by Kia et al. [44] showed that poorly-metastatic breast cancer cells (MCF-7) treated with exosomes derived from highly-metastatic breast cancer cells (MDA-MB-231) displayed overexpression of miR-9 and miR-155, which target the tumor suppressor genes, PTEN and DUSP14. They demonstrated that the corresponding miRNAs were enriched in metastatic TN breast cancer and could be transferred into other cells to alter the expression of target genes.