Growth inhibition in antimycin A treated-lung cancer Calu-6 cells via inducing a G1 phase arrest and apoptosis

Antimycin A (AMA) inhibits mitochondrial electron transport between cytochrome b and c. We evaluated the effects of AMA on the growth of human lung cancer cell line, Calu-6. AMA inhibited the growth of Calu-6 cells. AMA induced a G1 phase arrest of the cell cycle in these cells at 72 h. AMA increased a cyclin-dependent kinase inhibitor (CDKI), p27 and decreased CDK2, CDK4, and CDK6, as well as cyclin D1 and cyclin E in Calu-6 cells. AMA also induced apoptosis in Calu-6 cells. The apoptotic process in AMA-treated Calu-6 cells was accompanied by the up-regulation of Bax, the loss of mitochondrial membrane potential (ΔΨ_m), and the activation of caspase-3 and -8. All of the tested caspase inhibitors, especially pan-caspase inhibitor (Z-VAD), markedly rescued Calu-6 cells from AMA-induced Calu-6 cell death. Inhibitors of pan-caspase and caspase-8 also prevented the loss of mitochondrial membrane potential (ΔΨ_m). AMA decreased the intracellular ROS levels but increased the O₂^•- levels in Calu-6 cells. In conclusion, AMA as a mitochondrial electron transport inhibitor decreased the growth of lung cancer Calu-6 cell via inducing a G1 arrest of the cell cycle and apoptosis.