Circulating miRNAs are known to play important roles in intercellular communication. However, the effects of exosomal miRNAs on cells are not fully understood.
To investigate the role of exosomal miR-1246 in ovarian cancer (OC) microenvironment, researchers from the University of Texas MD Anderson Cancer Center performed RPPA as well as many other in vitro functional assays in ovarian cancer cells (sensitive; HeyA8, Skov3ip1, A2780 and chemoresistant; HeyA8-MDR, Skov3-TR, A2780-CP20). Therapeutic effect of miR-1246 inhibitor treatment was tested in OC animal model. They showed the effect of OC exosomal miR-1246 uptake on macrophages by co-culture experiments.
Substantial expression of oncogenic miR-1246 OC exosomes was found. The researchers showed that Cav1 gene, which is the direct target of miR-1246, is involved in the process of exosomal transfer. A significantly worse overall prognosis were found for OC patients with high miR-1246 and low Cav1 expression based on TCGA data. miR-1246 expression were significantly higher in paclitaxel-resistant OC exosomes than in their sensitive counterparts. Overexpression of Cav1 and anti-miR-1246 treatment significantly sensitized OC cells to paclitaxel. They showed that Cav1 and multi drug resistance (MDR) gene is involved in the process of exosomal transfer. Their proteomic approach also revealed that miR-1246 inhibits Cav1 and acts through PDGFβ receptor at the recipient cells to inhibit cell proliferation. miR-1246 inhibitor treatment in combination with chemotherapy led to reduced tumor burden in vivo. Finally, the researchers demonstrated that when OC cells are co-cultured with macrophages, they are capable of transferring their oncogenic miR-1246 to M2-type macrophages, but not M0-type macrophages.
miR-1246 promotes oncogenic activity in ovarian cancer cell
as well as in the tumor microenvironment
Mechanistic picture showing that miR-1246 directly targets Cav1 in OC cells. Cav1 inhibition leads to increased levels of PDGFRβ protein. Exosomal miR-1246 in the tumor microenvironment is taken up by tumor-associated immune cells.
These results suggest that cancer exosomes may contribute to oncogenesis by manipulating neighboring infiltrating immune cells. This study provide a new mechanistic therapeutic approach to overcome chemoresistance and tumor progression through exosomal miR-1246 in OC patients.