[Telomeres and telomerase in leukemias].

There is increasing evidence that telomere shortening both in vitro and in vivo is the clock that counts cell divisions and determines the onset of cellular senescence. Cells overcome the normal senescence mechanism by stabilising telomere length; probably due to the activity of telomerase activity that specifically elongates telomeres. Most human primary tumors contain telomerase, while the cells of most normal tissues lack this activity. Normal haematopoietic cells express telomerase activity. This review is a discussion of utility of telomere length and telomerase activity measurements in the diagnostics and prognosis of leukaemia as well as the potential value of antitelomerase therapy. Results of telomere lengths measurements in young recipients of allogenic transplants are also reported.