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Telomerase is a ribonucleoprotein enzyme that maintains protective structures at the ends of eukaryotic chromosomes. We examined the impact of telomerase inhibition by the dominant-negative human catalytic subunit of telomerase (DN-hTERT) on the biological features of acute leukemia. We introduced vectors encoding dominant- negative (DN)-hTERT, wild-type (WT)-hTERT, or a control vector expressing only a drug-resistant marker into a telomerase-positive human acute lymphoblastic leukemia cell line, HAL-01. Expression of DNhTERT dramatically inhibited telomerase activity, leading to apoptotic cell death. Mutant telomerase expression also enhanced daunorubicin-induced apoptosis. Nude mice (n=5 per group) received subcutanous implants of HAL-01 cells expressing the control vector or DN-hTERT or WT-hTERT. Implantation of HAL-01 cells expressing control vector (n=5) rapidly produced tumors, whereas implantation of those expressing DN-hTERT (n=5) did not. Thus, telomerase inhibition both growth of HAL-01 cells in vitro and tumorigenic capacity in vivo. Furthermore, the G-quadruplex-interactive telomerase-specific inhibitor, telomestatin, shortened the telomere length and induced apoptosis in freshly isolated primary acute leukemia cells. These results suggest that antitelomerase therapy may be useful in some acute leukemias in combination with antileukemic agents such as daunorubicin. [ABSTRACT FROM AUTHOR]

Presents several correspondence focused on leukemia. Efficacy of imatinib mesylate in conjunction with alpha-interferon; Imatnib mesylate-induced hepatotoxicity in chronic myeloid leukemia; Hepatitis C virus infection in patients with B-cell lymphoproliferative disorders; Lack of p53 expression in human myeloid leukemia.

A letter to the editor is presented in response to the article "Recurrent chromosomal aberration at 12q15 in chronic idiopathic myelofibrosis with or without JAK2V617F mutation," published online in the April 19, 2007 issue of "Leukemia."

A letter to the editor is presented about the uncontrolled thrombocytosis in polycythemia vera.

Focuses on a study conducted by the authors which suggests that tyrosine kinase inhibitor ST1571 in vitro affects ph-postive acutelymphoblastic leukemia and chronic myelogenous leukemia in blastic crisis. Examination of ST1571 induced apoptosis with the inhibition of tyrosine kinase autophosphorylation; Detection of apoptosis by flow cytometric analysis.