Similar levels of apoptosis were also seen with exposure to VX680, which suggested that this cytostatic pathway may not account for the differential susceptibility of 2884 and S462 cells to these AKIs. of depends upon the activity of the kinase, which correlates with the expression of the regulatory gene products TPX2 and in human tumours, and then treating MPNST cell-lines grown and as xenotransplants with an AURKA specific inhibitor, termed MLN8237 . AURKA is an oncogenic kinase that enables mitotic spindle assembly , and aurora kinase A inhibitors (AKI) often induce a G2/M cell cycle arrest followed by apoptosis in cancer cell lines grown and [7, 8]. Inhibitors of Aurora kinase B (AURKB) are also effective anti-mitotic drugs, which often induce mitotic failure and endoreduplication . Treatment of an MPNST cell-line with MLN8237 stabilized the cell-line’s growth and induced endoreduplication and senescence . Optimal application of these emerging therapies will require a better understanding and prediction of MPNST susceptibilities and tumour cell responses. The examination of copy number variants in human, primary dermal or plexiform neurofibromas and MPNSTs of differing grades provides an additional link between disease progression and the AURKA signalling pathway. In approximately half of the high-grade tumours and not in Rabbit Polyclonal to ABCD1 low-grade MPNSTs or neurofibromas, hemizygous deletion of the gene was reported . The 3-Methylglutaric acid gene encodes a multifunctional protein (RHAMM) that enables mitotic spindle assembly  and may attenuate the activation of AURKA , which relies upon a heterodimeric complex with targeting protein for XKLP2 (TPX2) . As RHAMM binds TPX2 [13, 14], the hemizygous loss of (20q13.2) and (20q11.2) lie within chromosomal regions that are 3-Methylglutaric acid frequently amplified in sporadic MPNSTs [15, 16]. Taken together, these genomic imbalances may oncogene-addict high-grade MPNSTs to AURKA activity and sensitize them to the treatment with AKIs. AURKA also regulates non-mitotic events, such as apicobasal polarization of epithelia , cilia resorption , and embryonic stem cell fate [18, 19]. In mouse embryonic stem cells (mESCs), AURKA is essential for maintenance of stem cell populations and silencing or treatment with AKI was sufficient to drive their differentiation through mesoderm and ectoderm lineages . Thus, AKI may have effects on non-mitotic processes in tumour cells, such as the determination of cell fate and differentiation. Here, we propose that AURKA represents a rational therapeutic target for MPNSTs and that the sensitivity of these tumours to AKI may be regulated by gene dosage and expression of and and as a xenotransplant . To build on these findings and test the efficacy of this new putative therapy against primary human MPNSTs, we treated two human tumours grown as explants (Castellsagu et al., manuscript under preparation). One sporadic (SP-MPNST) and one hereditary (NF1-MPNST) primary, human MPNST were separately transplanted orthotopically and expanded in the flank of NOD-SCID mice (n= 44 and 39, respectively) to a size of 2000 mm3, randomized, and treated by oral gavage with vehicle control or 30 mg/kg/day MLN8237 for a period of four weeks, which is a dosing regimen based upon the published pharmacodynamics for the drug . Treatment of animals with MLN8237 resulted in stabilized disease for tumour explants from both patients, as opposed to the 3-Methylglutaric acid linear expansion of tumour volumes in the vehicle treated cohorts (SP-MPNST, p <0.0001; NF1-MPNST, p= 0.0011) (Fig 1A,B). Once the dosing schedule was completed, tumours were excised and weighed. Consistent with the caliper measurements, treatment with MLN8237 resulted in tumour masses that were significantly lower in both the NF1-MPNST and SP-MPNST explants (p<0.01) compared to those of vehicle treated tumours (Fig 1A,B). Open in a separate window Figure 1 MLN8237 is effective against primary MPNSTs grown as xenotransplants in vivoA. Sporadic MPNST tumours were orthotopically transplanted into mice and allowed to grow to 2000 mm3 before treatment of 30mg/kg MLN8237 or vehicle was delivered daily. Treatment with MLN8237 resulted in stable disease after 2 weeks treatment, as determined by calliper measurements of tumour volumes, n=30 MLN8237 treated and n=14 for vehicle treated, *p<0.01, error bars = SD. Representative images of SP-MPNST tumours after 28 days of MLN8237 treatment or vehicle control are shown and treatment with the AKI resulted in significant reduction in tumour weight (quantitation on the right) (*p<0.01, Error bars = SD).NF1-MPNST tumours also show significantly stabilized tumour volumes and reduced tumour weight in the MLN8237 treated tumours compared to the vehicle controls. Vehicle treated mice, n=18, MLN8237 treated mice, n=21, error bars = SD. After 28 days of treatment, SP-MPNST tumour sections were stained for Ki-67 and DAPI. Ki-67 staining was significantly decreased in treated tumours suggesting that these cells have exited the cell cycle. Furthermore, there was a significant increase in multi-nucleate cells in treated tumours suggesting that cells are undergoing G2/M arrests and endoreduplication post treatment. *p<0.01, error bars = SD. Images are taken at 20x magnification. For insight into.