Telomerase activity in preleukemia and acute myelogenous leukemia.

The development of acute leukemia from preleukemia involves the appearance of clones with increasing proliferative potential. The studies described here demonstrate that telomerase activity progressively increases as the bone marrow cells acquire increasing proliferative potential. This was demonstrated by measuring telomerase activity in normal bone marrow, in post-treatment lymphoma marrows with skewed Lyonization, and in MDS and AML marrows. The greater telomerase activity in myelodysplastic marrow than in normal marrow is not due to a higher proportion of blast cells or to a higher proliferative rate of the MDS marrow. These data demonstrate that the increasing proliferative potential of the marrow which occurs during the development of AML is associated with a simultaneous increase in telomerase activity.

Suppression of telomerase activity and cytokine messenger RNA levels in acute myelogenous leukemia cells in vivo in patients by amifostine and interleukin 4.

High levels of telomerase activity and high rates of cell proliferation are associated with a poor prognosis in acute myelogenous leukemia. Furthermore, cytokine production by leukemia cells is believed to play an important role in determining the proliferative characteristics of leukemia. The in vivo effects of two noncytotoxic agents on these parameters were determined in 33 acute myelogenous leukemia patients. Three daily doses of interleukin (IL) 4 or a single dose of amifostine reduced telomerase activity in the leukemia marrow cells in 7 of 9 and 11 of 13 patients, respectively. The administration of a single dose of amifostine resulted in a reduction in tumor necrosis factor alpha and IL-6 transcript levels in the marrow cells of 10 of 13 and 12 of 13 patients in which these transcripts were present. The administration of only three doses of IL-4 or a single dose of amifostine has a significant effect on leukemia cell parameters, which are believed to have a significant impact on the in vivo biology of the disease and on its response to remission induction therapy.