O. Yamada et al., DOWN-REGULATION OF TELOMERASE ACTIVITY IS AN EARLY EVENT OF CELLULAR-DIFFERENTIATION WITHOUT APPARENT TELOMERIC DNA CHANGE, Leukemia research, 22(8), 1998, pp. 711-717
With the use of three different hematopoietic cell lineages, the downr
egulation of telomerase activity was found to be a general response to
the induction of differentiation. The decrease in telomerase activity
occurred as early as 24 h when HL-60 and K562 cells were cultured in
the presence of 1 alpha, 25 dihydroxyvitamin D3 (VD3), all-trans-retin
oic acid (ATRA) and hemin, and completely disappeared after 3 days. On
the other hand, MEG-OI cells showed a marked inhibition of telomerase
activity after 6 days of culture with 12-0-tetradecanoylphorbal 13-ac
etate (TPA). The analysis of telomeric DNA in the HL-60 cells and K562
cells demonstrated no detectable loss of telomeric DNA with cellular
differentiation, with a loss of telomerase activity. The repression of
telomerase is a common molecular event during leukemic cell different
iation. (C) 1998 Elsevier Science Ltd. All rights reserved.