Guanosine 5'-triphosphate induces differentiation-dependent apoptosis in human leukemia U937 and KG1 cells
Abstract
Aim: The differentiation capability of guanosine 5'-triphosphate (GTP) was studied using U937 and KG1 cells.
Methods: Cell cycle was analyzed by PI staining using flow cytometry. Apoptosis was measured by Annexin-V-FITC/PI double staining using flow cytometry. Differentiation was observed by morphological criteria, Wright-Giemsa staining and expression of cell surface markers CD11b and CD14.
Results: Variable GTP concentrations (25–200 mol/L) at short treatment times (up to 24 h) showed significant anti-proliferative activities among both cell types. However, longer treatment times (up to 72 h) were required to trigger apoptosis. Cell-cycle analyses of the GTP-treated cells indicated an increase in S-phase population by 48 h followed by the appearance of a sub-G1 peak after 72 h of treatment. The effects of GTP on U937 and KG1 cells were accompanied with differentiation toward monocyte/macrophage lineage. This was evidenced by a sharp increase in the extent of CD11b and CD14 expression after 24 h of exposure to GTP. The viability of both cell types did not significantly change during the first 24 h. However, at longer treatment times (72–96 h), dramatic decreases in both the extent of CD 14 expression and the cell viabilities were observed. Simultaneous measurement of apoptosis and CD14 expression in GTP-treated U937 cells indicated that cells with lower CD 14 content underwent more apoptosis.
Conclusion: These finding may pave the way for further pharmaceutical evaluation of GTP as a suitable differentiating agent for acute myeloblastic leukemia (AML) therapy.
Keywords:
Methods: Cell cycle was analyzed by PI staining using flow cytometry. Apoptosis was measured by Annexin-V-FITC/PI double staining using flow cytometry. Differentiation was observed by morphological criteria, Wright-Giemsa staining and expression of cell surface markers CD11b and CD14.
Results: Variable GTP concentrations (25–200 mol/L) at short treatment times (up to 24 h) showed significant anti-proliferative activities among both cell types. However, longer treatment times (up to 72 h) were required to trigger apoptosis. Cell-cycle analyses of the GTP-treated cells indicated an increase in S-phase population by 48 h followed by the appearance of a sub-G1 peak after 72 h of treatment. The effects of GTP on U937 and KG1 cells were accompanied with differentiation toward monocyte/macrophage lineage. This was evidenced by a sharp increase in the extent of CD11b and CD14 expression after 24 h of exposure to GTP. The viability of both cell types did not significantly change during the first 24 h. However, at longer treatment times (72–96 h), dramatic decreases in both the extent of CD 14 expression and the cell viabilities were observed. Simultaneous measurement of apoptosis and CD14 expression in GTP-treated U937 cells indicated that cells with lower CD 14 content underwent more apoptosis.
Conclusion: These finding may pave the way for further pharmaceutical evaluation of GTP as a suitable differentiating agent for acute myeloblastic leukemia (AML) therapy.