Extracellular ATP-dependent suppression of proliferation and induction of differentiation of human HL-60 leukemia cells by distinct mechanisms

Abstract

Extracellular ATP suppressed the growth of HL-60 leukemia cells and induced their differentiation as revealed by N-formyl-methionyl-leucyl-phenylalanine-induced β-glucuronidase release. ATP degraded to ADP, AMP, and adenosine, and the effect of ATP on cell growth was mimicked by these metabolites added to the cultures. The stable analog α,β-methylene ATP, however, had only a weak inhibitory effect on cell growth. Adenine nucleotide-induced growth suppression was reversed by uridine, suggesting the involvement of intracellular pyrimidine starvation secondary to adenosine accumulation. Consistent with this, ATP induced intracellular starvation of pyrimidine nucleotides, and this effect was also prevented by pretreatment of cells with uridine. The order of effectiveness of ATP-induced differentiation of HL-60 cells, unlike that for growth suppression, was ATP > ADP > AMP, and adenosine had no effect. Furthermore, uridine had no effect and the stable analog, α,β-methylene ATP also induced HL-60 cell differentiation, suggesting that differentiation was due to ATP per se. We tested the hypothesis that ATP-induced differentiation arises from activation of adenylyl cyclase by the novel P2Y11 receptor using the cell-permeable inhibitor of protein kinase A, Rp-CPT-cAMPS (8-(4-chlorophenylthio)adenosine-3′,5′-cyclic monophosphorothioate, Rp isomer). Rp-CPT-cAMPS (1–100 μM) prevented ATP-induced differentiation of HL-60 cells as assessed by fMLP-induced β-glucuronidase release. However, Rp-CPT-cAMPS did not prevent ATP-induced growth suppression. Taken together, the data indicate that extracellular ATP suppresses HL-60 growth and induces their differentiation by distinct mechanisms. Growth suppression arises from adenosine generation and consequent pyrimidine starvation. Differentiation arises, at least in part, from a distinct mechanism involving the activation of cell surface P2 receptors coupled to cAMP generation and activation of protein kinase A.