The use of Aurora B inhibitors for the treatment of G3M tumors may be further evaluated by examining the effectiveness and optimal dosing of of AZD1152-HQPA in murine models of G3M tumors such as those explained by Pei et al.[49] and Kawauchi et al.[50] MATERIALS AND METHODS Cell culture Medulloblastoma cells were cultured in standard media at 37C in a 5% CO2 atmosphere. inhibit intracranial tumor growth and prolong survival in mice bearing tumors created from MYC-overexpressing medulloblastoma cells. Our results suggest the potential for therapeutic application of Aurora kinase B inhibitors in the treatment of Group 3 medulloblastoma. overexpression, is usually a negative prognostic factor for overall survival in MB.[18, 19] Approximately 11% of G3MB tumors demonstrate amplification.[20] Furthermore, all G3MB tumors express at high levels and express genes associated with elevated MYC levels.[20] We hypothesized that MB cells overexpressing MYC would be uniquely sensitized to the effects of Aurora B inhibition and that this property could be harnessed for the SPL-B treatment of MYC-overexpressing MB tumors. The goal of our study was not only to determine if MYC overexpression in human MB cells sensitized the cells to the apoptotic effects of Aurora B inhibition, but also to further define the mechanism triggering this response. We demonstrate that Aurora B inhibition triggers cell death impartial of DNA replication and that transient Aurora B inhibition results in a unique impaired growth response in MYC-overexpressing cells. Having defined the response time-course we proceeded to optimize therapy with AZD-1152 HQPA, achieving a prolongation in survival of mice bearing cerebellar xenografts of MB cells having amplification and endogenously overexpressing MYC. RESULTS Co-expression of Aurora B and MYC in Group 3 medulloblastoma MYC has been shown to directly regulate the expression of Aurora A and indirectly the expression of Aurora B in B-cell lymphoma.[15] Therefore, we sought to determine if Aurora kinase gene expression correlates with expression in human MB. SPL-B and mRNA expression SPL-B showed a positive correlation with mRNA expression (vs vs and expression (Fig. ?(Fig.1A).1A). The highest expression was observed in WNT and G3MB relative to other subgroups, normal fetal cerebellum, and adult cerebellum (Fig. ?(Fig.1B).1B). Furthermore, there was a modest correlation between expression and Aurora B expression in G3MB (R=0.57, P=0.002, N=27, Fig. ?Fig.1C).1C). Although WNT tumors express high levels of mRNA we did not observe a correlation to mRNA expression in this small subset of tumor samples (R=0.42, P=0.3, N=8). Aurora kinase gene expression is increased in fetal cerebellum and in all subgroups of MB compared to adult cerebellum, reflecting the proliferative capacity of fetal and tumor tissue. Open in a separate window Physique 1 Aurora kinase mRNA and protein expression in relation to Myc expression in MAP2K7 medulloblastomaA) mRNA expression of in relation to mRNA level in 103 medulloblastoma tumor samples. B) mRNA expression in fetal cerebellum (fCb), adult cerebellum (aCb), and medulloblastoma tumors subgrouped according to RNA expression profile, ANOVA P<0.0001. C) Correlation between mRNA expression and MYC mRNA expression in medulloblastoma tumors subgrouped as Group 3. D) Western blot showing protein expression of Aurora A, Aurora B, and MYC in multiple medulloblastoma cell lines. Cell lines harboring amplification are indicated by a star. The loading control was -Actin. Total protein loaded was 30 g. To further evaluate the expression of Aurora kinase A and B in relation to MYC, protein expression in a number of unsynchronized MB cell lines was evaluated (Fig. ?(Fig.1D).1D). The D425, D458 and MED8A cells, all of which have known amplification of = SPL-B 0.24 hr?1; = 190 L; C0 = 13.3 ng/L; t1/2 = 2.9 hours; AUClinear = 68 ng ? hours/L (Fig. ?(Fig.7A).7A). The calculated effective therapeutic plasma concentration time was 11 hr for any dose of 2.5 mg (equivalent to 50 mg/kg for any 25 gm mouse). The biodistribution of AZD1152-HQPA in the brain was confirmed using LC/MS/MS after subcutaneous administration of the drug in a phosphate buffered saline answer. The peak brain content of AZD1152-HQPA was 0.7 .