Abstract: Objective To investigate the possible mechanism of phenformin inhibiting proliferation and promoting apoptosis of A549/DDP cells. Methods MTS assay was used to detect the cell viability of A549/DDP cells treated with cisplatin and phenformin. The treatment group was treated with phenformin (2.5 mmol/L), and control group was treated with phosphate buffer saline (PBS). MTS assay was used to detect the effect of phenformin on the proliferation of A549/DDP cells. The colony formation ability was detected by colony formation assay. Flow cytometry was used to detect the effects of phenformin on apoptosis, reactive oxygen species (ROS), mitochondrial mass (Mitotracker) and calcium ion (Rhod-2) in A549/DDP cells. The real-time quantitative PCR was used to detect mitochondrial DNA (mtDNA), and ATP was detected by ATP kit. The effect of phenformin on mitochondrial oxidative phosphorylation complex was detected by Western blot assay. Results Compared with the cisplatin group, the cell viability ratios of A549/DDP cells were decreased at 24 h and 48 h in the phenformin group (P＜0.05), but there was no significant difference in the viability at 24 h and 48 h of A549 cells between the two groups. The viability of A549/DDP cells treated with cisplatin 48 h was high compared with that of A549 cells, but there was no significant difference in the viability of 24 h. The viability of A549/DDP cells treated with phenformin was significantly lower than that of A549 cells (P＜0.05). Compared with the PBS group, the proliferation rate and colony formation of A549/DDP cells decreased at 24 h and 48 h in the phenformin group, while the apoptosis rate and the ROS level increased (P＜0.05). Mitotracker, Rhod-2, mtDNA and ATP were also decreased (P＜0.05). The NDUFB8 protein in complex I, the SDHB protein in complex II, and the MTCO1 protein in complex IV were significantly decreased (P＜0.05). Conclusion (1) A549/DDP cells are more sensitive to phenformin than A549 cells, but more resistant to cisplatin than A549 cells. (2) Phenformin inhibits proliferation and promots apoptosis of A549/DDP cells by increasing intracellular ROS, decreasing mitochondrial mass, calcium ion and mtDNA and inhibiting mitochondrial oxidative phosphorylation complex, and reducing ATP production.

Key words: phenformin, mitochondria, A549/DDP cell