Exosomal transfer of miR-214 mediates gefitinib resistance in non-small cell lung cancer.

Recent studies have demonstrated that exosomal miRNAs mediate as intercellular bio-messengers of drug resistance in lung cancer. Our objective was to investigate whether exosomes derived from gefitinib resistant non-small cell lung cancer cells could confer resistance to its recipient cells. Exosomes were successfully isolated by ultracentrifugation and exosomes morphologies and sizes were determined by transmission electron microscopy and dynamic light scattering analysis. Fluorescent PKH-67 labeled exosomes derived from PC-9GR cells could be taken up and internalized by PC-9 cells. CCK8 measurement showed that PC-9GR-derived exosomes could confer gefitinib resistance in PC-9 cells. MiRNA-214 was upregulated in gefitinib resistant PC-9GR cells and its derived exosomes by qPCR analysis. Inhibition of exosomal miR-214 with antagomir reversed gefitinib resistance conferred by PC-9GR-derived exosomes in vitro, which was confirmed by flow cytometry analysis and westernblot of apoptotic protein (caspase-3, caspase-3 cleaved, bax) and anti-apoptotic protein (bcl-2). Finally, exosomes enriched with miR-214 antagomir was further confirmed to reverse gefitinib resistance in vivo. Our results are the first to show that exosomes derived from gefitinib-resistant PC-9GR cells could transfer resistance to its recipient sensitive PC-9 cells, which might be mediated by exosomal transfer of miR-214.