Abstract: Aim To investigate the possible mechanism of human promyelocytic leukemia cells differentiation and apoptosis induced by all trans-retinoic acid (ATRA)and A ra-c.Methods The effects of AT RA and Ara-c on the tolomerase activity of HL-60 cells were detected by PCR-E LISA.Results The tolome rase activity of HL-60 cells declined during the course of differentiation and apoptosis induced by AT RA and Ara-c.Conclusion These finding ssuggest that AT RA and Ara-c can inhibit tolomerase activity of HL-60 cells.It may be one of the important mechanisms of human promyelocytic leukemia cells differentiation and apo ptosis induced by ATRA and Ara-c.

Key words: HL-60 cell, telomerase activity, alltrans-re tinonic acid, cytosirearabinoside