The receptor tyrosine kinase FLT3 is a promising molecular therapeutic target in acute myeloid leukemia (AML). Activating mutations of FLT3 are present in approximately one-third of patients, while many nonmutants show evidence of FLT3 activation, which appears to play a significant role in leukemogenesis. We studied the effects of lestaurtinib (CEP701)
BackgroundAurora kinases play an essential role in the orchestration of chromosome separation and cytokinesis during mitosis. Small-molecule inhibition of the aurora kinases has been shown to result in inhibition of cell division, phosphorylation of histone H3 and the induction of apoptosis in a number of cell systems. These characteristics have led aurora kinase inhibitors to be considered as potential therapeutic agents.
SummaryActivating mutations of the FMS-like tyrosine kinase 3 gene (FLT3) occur in approximately one-third of patients with acute myeloid leukaemia (AML) and predict for a poor outcome. Heat shock protein 90 (Hsp90) is a molecular chaperone that is frequently used by cancer cells to stabilise mutant oncoproteins. Mutant FLT3 is chaperoned by Hsp90 in primary AML blasts whereas unmutated FLT3 is not, making Hsp90 inhibitors potentially useful therapeutically. The present study showed that inhibition of Hsp90 by 17-allylamino-17-demethoxygeldanamycin (17-AAG) was cytotoxic to primary AML cells expressing mutant FLT3. Inhibition of Hsp90 results in altered downstream signalling effects in primary AML cells with disruption of Janus kinase-signal transducer and activator of transcription (JAK-STAT), mitogen-activated protein kinase and phosphatidylinositol 3/AKT signalling pathways. Co-treatment of blasts with 17-AAG and cytarabine resulted in a synergistic or additive effect in approximately 50% of AML cases tested. Our results confirm that Hsp90 is a valid molecular target in the therapy of AML. Inhibition of Hsp90 in parallel with conventional AML therapies may have particular benefit in those patients with the poor prognostic FLT3 mutant disease.Keywords: acute myeloid leukaemia, FLT3, heat shock protein 90, Ara-C, 17-allylamino-17-demethoxygeldanamycin. research paper ª
Myelodysplastic syndromes (MDS) are characterized by a clonal disorder of haemopoiesis with defective growth in vitro. The long-term culture system was used to examine aspects of stromal function in MDS patients. Primary long-term cultures of MDS bone marrow showed poor myelopoiesis with progenitors being detected for a median 3.5 weeks (n = 12) compared with 18 weeks in cultures of normal marrow (n = 10; P < 0.0001). The haemopoietic function of adherent layers was assessed in secondary co-cultures seeded with 5 x 10(6) cord blood mononuclear cells on irradiated normal (n = 27; aged 38-82 years) or MDS (n = 32; aged 41-86 years) adherent layers (> 60% confluent). The median myeloid progenitor number/cord blood co-culture was 135 in 5-week-old cultures with normal adherent layers and 22 in those with MDS layers (P < 0.0001). Myeloid colonies were detectable for a median 11 weeks with normal adherent layers and 6 weeks with MDS adherent layers (P < 0.0001); erythroid colonies were detectable for 7 weeks (normal) compared with 5 weeks (MDS) (P < 0.01). The differences in granulocyte-macrophage colony forming unit (CFU-GM) generation were not related to patient age. Cells from adherent layers of at least half of the primary normal (n = 48) and MDS (n = 26) long-term cultures expressed cytokines [interleukin (IL)-3, IL-1 beta, thrombopoietin (Tpo) and erythropoietin (Epo)] and receptors for retinoic acid (RAR alpha) [IL-2, IL-3, macrophage colony stimulating factor (M-CSF) (Fms) and Tpo (Mpl)]. Only IL-1 beta expression was reduced in week-5 MDS cultures compared with those from normal marrows (P < 0.05). There was also a highly significant decline in IL-1 beta expression in normal (but not MDS) adherent layers between week 5 and week 10. Thus, the adherent layers in cultures grown from MDS patients were haemopoietically defective and showed abnormal IL-1 beta expression.
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