Occurrence of Aurora A positive multipolar mitoses in distinct molecular classes of colorectal carcinomas and effect of Aurora A inhibition

Aurora A "over-"expression may induce supernumerary centrosomes, respective multipolar mitoses, and aneuploidy. Here, we examined Aurora A positive multipolar mitoses in aneuploid, microsatellite-stable (MSS, "CIN-type") versus near-diploid, microsatellite-instable (MSI, "MIN-type") colorectal carcinomas (CRC) and CRC cell lines as well as the effect of Aurora A inhibition in CRC cell lines. In situ, three-dimensional immunofluorescence (3D-IF) revealed Aurora A positive multipolar mitoses in both CIN- (n = 8) and MIN- (n = 10) type primary CRCs with similar frequencies (CIN: 27 ± 14%; MIN: 34 ± 14%, P = 0.224). In vitro, Aurora A positive multipolar mitoses were detected in asynchronized or thymidine synchronized CIN-type (HT29, CaCo-2), but not MIN-type (HCT116, DLD-1) CRC cells. Nocodazole treatment arrested mitotic cells with multiple centrosomal Aurora A signals in CIN- and MIN-type CRC cells, albeit to a lower extent in CaCo-2 cells. This was associated with concomitant activation of Aurora A (T288 phosphorylation) and Polo-like kinase 1 (PLK-1, T210 phosphorylation). Aurora A inhibition by siRNA resulted in increased apoptosis (>50%) in all cell lines, but did not abolish PLK-1 expression. Double 3D-IF revealed that Aurora A siRNA treated, still viable CIN-type (HT29, CaCo-2) CRC cells were Aurora A negative and mostly in prophase/(pro)metaphase with maintained phosphorylated PLK-1 T210 expression. Aurora A positive multipolar mitoses occur in both aneuploid, CIN- and near-diploid MIN-type CRCs. This appears to be largely independent of Aurora A expression alone. Although Aurora A inhibition causes apoptosis in both CIN- and MIN-type CRC cells, remaining PLK-1 activation by other factors may affect therapeutic Aurora inhibition.

Phase I, open-label, multicentre, dose-escalation, pharmacokinetic and pharmacodynamic trial of the oral aurora kinase inhibitor PF-03814735 in advanced solid tumours

This phase I study (ClinicalTrials.gov ID: NCT00424632) evaluated the safe dose, pharmacokinetics, and pharmacodynamics of the aurora kinase A and B inhibitor, PF-03814735. Patients with advanced solid tumours received oral, once-daily (QD) PF-03814735 on Schedule A: days 1-5 (5-100mg); or Schedule B: days 1-10 (40-60mg) of 21-day cycles. Fifty-seven patients were treated: 32 and 25 on Schedules A and B, respectively. Dose-limiting toxicities were: febrile neutropenia (Schedule A); and increased levels of aspartate amino transferase, left ventricular dysfunction, and prolonged low-grade neutropenia (Schedule B). Maximum tolerated doses were 80mg QD (Schedule A) and 50mg QD (Schedule B). Common treatment-related adverse events were mainly mild to moderate and included diarrhoea, fatigue, nausea, and vomiting. Nineteen patients achieved stable disease, which was prolonged in four cases. PF-03814735 was rapidly absorbed and demonstrated linear pharmacokinetics up to 100mg QD; mean terminal half-life ranged from 14.4 to 23.6h. Aurora B activity, assessed by histone H3 phosphorylation in mitotic cells, decreased in tumour tissue from 10/12 patients evaluated (range: -70% to -3%). (18)F-fluorodeoxyglucose positron emission tomography demonstrated metabolic responses in only 1/21 patients. PF-03814735 was generally well tolerated with manageable toxicities, and a recommended phase II dose could be established for both schedules. Aurora B activity was inhibited in tumour tissue, but clinical or metabolic antitumour activity was limited.