Inhibition of autophagy promotes cisplatin-induced apoptotic cell death through Atg5 and Beclin 1 in A549 human lung cancer cells

Recent studies have indicated that autophagy contributes to tumorigenesis and participates in acquired chemotherapeutic resistance. The present study aimed to determine the function and underlying mechanism of cisplatin-induced autophagy in A549 human lung cancer cells. Autophagy was measured by LC3B-I/II conversion, LC3B puncta and autophagosomes formation. Apoptotic cell death was measured by caspase-3 activity, caspase-3 cleavage and LDH release. The transcriptional and expressional level of autophagy related proteins were measured by reverse transcription-quantitative polymerase chain reaction and western blot analysis. Beclin 1 and Atg 5 siRNA transfection was used to explore the function of cisplatin-induced autophagy. The results demonstrated that cisplatin induces apoptotic cell death in A549 cells and triggers an autophagic response, as indicated by increased microtubule-associated protein 1 light chain 3 (LC3B)-I/II conversion, increased LC3B puncta and autophagosome formation. Mechanisms underlying cisplatin-induced autophagic responses were also investigated. Cisplatin induced autophagy by upregulating the mRNA and protein expression levels of autophagy protein (Atg)5 and Beclin 1, whereas the mRNA and protein expression levels of serine/threonine-protein kinase ULK1, Atg3, Atg7, Atg12, and sequestosome-1 were not markedly upregulated. In addition, knockdown of Atg5 and Beclin 1 by small interfering RNA transfection impaired cisplatin-induced activation of autophagic responses, increased caspase-3 cleavage and inhibited cell viability. These findings suggested that disruption of autophagy via the inhibition of Atg5 and Beclin 1 may promote cisplatin-induced apoptotic cell death in A549 human lung cancer cells. In conclusion, the present study demonstrated that targeting autophagy may be used in the future for the treatment of lung cancer.