Telomerase activity in human acute myelogenous leukemia: Inhibition of telomerase activity by differentiation-inducing agents

The terminal regions of human chromosomes, the telomeres, shorten with each cell division in most normal somatic cells. Telomerase, a ribonucleoprotein that synthesizes telomeric DNA onto chromosomal ends, is activated in germline cells and almost all tumor cells. Telomerase activity maintains the stability of telomere length, resulting in indefinite cellular proliferation (immortality). In the present study, telomerase activity was analyzed in leukemic mononuclear blood cells obtained from 56 patients with acute myelogenous leukemia (AML) with known cytogenetic alterations. Heterogenous levels of telomerase activity were observed and generally correlated with cytogenetic status. Patients with 11q abnormalities and -5/-7 (unfavorable cytogenetics) tended to have high telomerase activity compared with cells obtained from AML patients with other types of cytogenetics. Additional studies with a larger cohort of patients will determine whether these differences are statistically significant. Chemotherapy agents that result in differentiation of leukemic cells also resulted in inhibition of telomerase activity. Knowledge of telomerase activity in patients with AML, before and throughout therapy, may have clinical utility for following disease progression and may predict early cancer relapse.