Objective: To investigate the regulation of telomerase activity in HL-60 and NB4 cells exposed to arsenic trioxide (As(2)O(3)).
Methods: Cell morphology, intracellular DNA distribution, bcl-2 expression and telomerase activity were evaluated in HL-60 and NB4 cells exposed to As(2)O(3) or ATRA.
Results: The differentiation induction of HL-60 and NB4 cells by low concentration of As(2)O(3) was weaker than that by ATRA, but downregulation effect of As(2)O(3) on telomerase activity was more strong and quick. Higher concentration of As(2)O(3) induced apoptosis in HL-60 or NB4 cells accompanied by more rapid down regulation of telomerase activity and bcl-2 expression. Neither As(2)O(3) nor ATRA showed direct inhibition effect on telomerase activity.
Conclusion: The downregulation of telomerase activity by low concentration of As(2)O(3) in HL-60 and NB4 cells is the result of overlap of differentiation and apoptosis. There are similar mechanisms in the regulation of telomerase activity and apoptosis in different leukemia cells. Bcl-2 may play an important role in these mechanisms.