EXOSOMES MEDIATE MIR-21 TO PROMOTE CISPLATIN RESISTANCE IN LUNG CANCER BY REGULATING PTEN

Liqun Liang^{1, #}, Junmei Jia^{1, #, *}, Hongchun Kang², Bin Song³

¹Oncology Department, The First Affillated Hospital of Shanxi Medical University, Shanxi Province, China - ²Department of Pharmacy, Chongqing Three Gorges Central Hospital, Chongqing City, China.

Objective: This study was designed to investigate the potential molecular mechanisms by which exosomes mediate the transfer of drug resistance between lung cancer cells by microRNA (miRNA, miR-21).

Methods: Exosomes from cell supernatants were extracted by kit, their morphology and size were observed by electron microscopy, and exosome-specific proteins were detected by Western blot. The uptake of PKH26-labeled exosomes by cells transfected with green fluorescent plasmids was observed by laser confocal microscopy. MiR-21 mimic/inhibitor or PTEN overexpression plasmids were transfected into cells to regulate the expression levels of miR-21 and PTEN in cells. Expression levels of miR-21 and PTEN in lung cancer cells were determined by RT-qPCR, Northern blot and Western blot. The CCK-8 method was used to detect cell activity under cisplatin treatment and to calculate IC50. The clone formation experiment verified the sensitivity of different cells to cisplatin.

Results: Compared with the parent cells A549, the expression of miR-21 in A549/DDP was significantly increased, and the regulation of miR-21 level in lung cancer cells could affect the sensitivity of cells to cisplatin. MiR-21 levels in exosomes (exo/DDP) derived from A549/DDP were significantly higher than in those derived from A549 cells. The results showed that exo/DDP could be absorbed by A549 cells. CCK-8 and clone formation experiments showed that after incubating with exo/DDP, the sensitivity of A549 cells to cisplatin decreased significantly and IC50 increased significantly. RT-qPCR and Western blot results showed that after co-incubating exo/DDP in A549 cells, the expression of miR-21 was significantly increased, while that of PTEN was decreased. Meanwhile, by regulating the expression levels of miR-21 and PTEN, this experiment further confirmed that miR-21 could regulate the expression of PTEN, thus affecting the sensitivity of lung cancer cells to cisplatin.

Conclusion: Exosomes secreted by cisplatin-resistant lung cancer cells can transmit miR-21, thereby affecting the level of miR-21 in recipient cells. This, in turn, regulates the expression of cell PTEN and induces cisplatin resistance in lung cancer cells. This study provides a new approach and target to reverse drug resistance in lung cancer.