The Aurora Kinase Inhibitor AZD1152 Causes Perturbation of Cell Cycle Distribution in Cell Lines and Primary AML Samples.

Aurora kinases (AK) participate in chromosome separation during mitosis and are essential for mitotic processes and completion of cytokinesis. AK-A is found at the centrosome and spindle apparatus during prophase to telophase, while AK-B is seen in the midzone during anaphase of the cell cycle. Inhibition of these kinases may be a viable therapeutic strategy. AZD1152 is a specific AK inhibitor, designed to target cell division in proliferating tumour cells, with potential for activity in a wide range of tumours. In order to evaluate the potential utility of the AK inhibitor AZD1152 in acute myeloid leukaemia (AML), the expression levels of AK-A, -B, and -C were evaluated in a panel of myeloid cell lines (HL-60, NB4, NB4R2, U937, KG1, and K562) and in cells from 10 normal bone marrows and 240 AML patients using the Affymetrix gene expression system (Affymetrix Inc.) validated by real-time quantitative polymerase chain reaction in 105 patients. AK-C was absent in all samples, while AK-A and -B were present in 5% and 34%, respectively, of the AML patients and both were present in normal bone marrow samples. Expression levels did not correlate with age, sex, French-American-British classification or cytogenetic risk group. AML cell lines were incubated with a variable concentration of AK inhibitor (0.01 μM to 10 μM) for up to 72 h and the effects on viability, cell growth, cell cycle, and DNA content measured after 24 and 48 h exposure. This resulted in the accumulation of cells with 4N DNA content, indicating an increased proportion of cells in G2, and development of cells with DNA content greater than G2/M phase cells, on occasions showing 8N ploidy. This effect was time and dose dependent. At 24 h AK inhibitor caused a significant increase (p≤0.05) in the number of cells with 4N DNA content, suggestive of G2, or with greater than 4N DNA content at concentrations as low as 0.01 μM. Growth of HL-60 and NB4 cells was inhibited, following 72 h treatment with AK inhibitor (0.01 μM), by 50% and 90% (p<0.05), respectively. Incubation of AML samples (n=28) with AK inhibitor also showed an effect on the cell cycle, with a significant increase in G2 population (p≤0.05), and occasionally an increase of DNA content (p≤0.05) after 24 and 48 h at a minimum concentration of 1.0 μM. Flow cytometric analysis showed histone H3 phosphorylation was decreased, from around 3–5% in untreated cells, only in a proportion (~35%) of primary samples. The growth inhibition effects seen are combined with increased DNA content, which is consistent with the endoreduplication effects associated with these agents. AK-B is expressed in around one-third of AML patients, and agents targeted against this kinase may have therapeutic potential in AML.