Apoptosis induction and S-phase cell cycle arrest by adenosine 5́-triphosphate through its degradation to adenosine in human myeloid leukemia K562 cell line

Adenosine 5́-triphosphate (ATP) is not only the current energy sources for all cells but also plays a critical role in triggering signaling pathways leading to apoptosis or differentiation. During the past years many investigations have been reported the anti-cancer activity of ATP on different cell lines. Also several mechanisms have been proposed for its action and it appears that its mechanism of action depends on the cell type. In the present study effects of ATP on human leukemia K562 cell line as an experimental model of CML and it mechanism of action were studied. K562 cells were cultured and treated with different concentrations of ATP (50-1000 µM) at various time intervals (24-72 h). Effect of ATP on cell proliferation was studied by MTT assay. Apoptosis was studied by flow cytometry and DNA fragmentation assay. Cell cycle and DNA contents were analyzed by flow cytometry. To evaluate the mechanism of action of ATP, effects of ATPγS (an undegradable agonist of ATP) and products of ATP degradation such as AMP, ADP and adenosine were studied. ATP with doses of 100-1000 µM inhibited growth of the cells and induced S-phase cell cycle arrest at the time intervals of 24-72 hour. These effects of ATP led to cell death by apoptosis. In addition, the results showed that these effects of ATP were through its degradation to adenosine and eventually induction of pyrimidine starvation. Because current CML therapy methods which are based on chemotherapy are not very effective and have side effects such as drug resistance, ATP can be proposed as an effective compound alone or in combination with other drugs for treatment of CML.