A Monoclonal Antibody (Mc178-Ab) Targeted to the Ecto-ATP Synthase β-subunit-induced Cell Apoptosis Via a Mechanism Involving the MAPKase and Akt Pathways

Ecto-ATP synthase has been considered to be an effective target for cancer recently. As inhibitors of ecto-ATP synthase were found to be cytotoxic for tumor cells, a monoclonal antibody (Mc178-Ab) against ecto-ATP synthase was generated in our previous study that exhibited both anti-angiogenic and anti-tumorigenic effects. However, the mechanism of action of Mc178-Ab and its downstream pathways for anti-tumor effects remain unclear. In this research, we intended to investigate the mechanism of the anti-tumor action of Mc178-Ab. The expressions of cell surface ATP synthase on A549 and CHO cells were confirmed by flow cytometry and confocal microscope. Proliferation and apoptosis were examined after the treatment with Mc178-Ab. In order to examine the activity of ecto-ATP synthase changed by Mc178-Ab, extracellular ATP generation and intracellular pH levels were assessed. The phosphorylation of the signaling molecules, MAPKase and Akt, was analyzed by western blot. Cell proliferation was blocked, and apoptosis was induced in A549 cells treated with Mc178-Ab, as determined by MTT assay and flow cytometry analysis of Annexin-V/PI staining separately. The intracellular pH level and extracellular ATP generation were also decreased after Mc178-Ab treatment. Finally, western blot data revealed that the phosphorylation of JNK and p38 was increased, while the phosphorylation of ERK and Akt was decreased in A549 cells treated with Mc178-Ab. Compared with A549 cells, Mc178-Ab had less effect on CHO cells. The decreased intracellular pH levels and the altered concentration of extracellular ATP may contribute to the mechanisms of the effect of Mc178-Ab on A549 and CHO cells. The results also suggested that the anti-tumor effect of Mc178-Ab was associated with MAPKase and Akt pathways.