Astrocytoma is currently incurable due to its diffuse infiltration and the lack of effective therapies. We are developing a mouse model of spontaneous astrocytoma through mutation of Nf1 and p53. Both Nf1 and p53 have been shown to be mutated in sporadic human glioblastomas (GBM). In addition, p53 has been shown to be mutated in anaplastic astrocytomas, although NF1 has not yet been examined. In addition, Nf1 is associated with the disease neurofibromatosis type 1, for which there are no cures and very few therapy options for treatment. The astrocytomas and GBM in the Nf1/p53 mutant mice show diffuse infiltration throughout the central nervous system and form secondary structures around neurons and blood vessels recapitulating the pathology seen in human astrocytomas. We are developing methods for imaging astrocytomas in live animals and quantitating tumor burden in order to use this model for testing experimental therapeutics. During fiscal year 2008 we completed and published a high-throughput system for screening anti-astrocytoma compounds. Using this system we can rapidly determine GI50 and LC50 values for compounds in anaplastic astrocytoma cells. This work was published in the Journal of Biomolecular Screening and a licensing abstract was advertised by the NCI. We also initiated a collaboration with the Molecular Targets Development Program to use this assay for high-throughput screening of compound libraries available at NCI. This year we have also completed the development of a bioluminescent in vivo imaging system for this mouse model and have demonstrated the serial imaging of tumor growth for both astrocytoma and malignant peripheral nerve sheath tumor (MPNST). We are currently using this system to follow the natural history of these tumors to better understand when we can first detect them and how fast they progress to clinical symptoms. This information will be critical for effectively designing in vivo preclinical trials using this model. In another collaboration with the Molecular Targets Development Program, we are examining the effects of a natural compound, Schweinfurthin, on astrocytoma in vitro and in vivo. We have shown that Schweinfurthin acts specifically through a NF1/rasGAP dependent mechanism and may impact Rho signaling. We have shown that a Schweinfurthin analogue is tolerated in vivo, although it does exhibit liver toxicity. We are now testing the efficacy of Schweinfurthin in a tumor challenge model using intracranial injection of astrocytoma cells into mouse brains. This work is being done within the Center for Applied Preclinical Research. We have also initiated a collaboration this year with a clinical NF group at Children's National Medical Center to perform cross-species comparisons of NF1 tumor cells and to take promising therapeutic leads for testing in our Nf1/p53 mouse model.
