Abstract: Objective To establish the lung cancer cell strain of ATG5 low expression and detect the effect of celastrol on lung cancer cell apoptosis after downregulation of autophagy. Methods H1299 was infected by lentivirus-mediated ATG5 shRNA. RT-qPCR and Western blot assays were applied to confirm the effect of ATG5 knock down. Autophagy levels were measured by Western blot and RFP-LC3 transfection. Cell apoptosis between ATG5 normal expression group and ATG5 low expression group of H1299 cells was detected by FACS after cells were treated with celastrol. Finally, Western blot was used to detect the expression of apoptosis-related proteins Bcl-2, Bax and cleaved caspase-3. Results The expression of ATG mRNA and protein levels were decreased significantly after ATG5 knockdown in H1299 cells (P < 0.05). The autophagy marker of LC3-II level was downregulated and P62 expression was upregulated after inhibition of ATG5, and the RFP-LC3 puncta reduced significantly after ATG5 knockdown (P < 0.05). Compared with control group, the apoptosis rate in ATG5 downregulation group increased significantly after celastrol treatment (P < 0.01). Pro-apoptotic proteins of Bax and cleaved caspase-3 levels were upregulated and anti-apoptotic protein of Bcl-2 level decreased after ATG5 inhibition (P < 0.05). Conclusion The effect of celastrol-induced apoptosis of lung cancer cells was enhanced after downregulation of autophagy, demonstrating inhibition autophay may be a new target of lung cancer treatment.

Key words: ATG5, autophagy, celastrol, lung cancer, apoptosis