Abstract
Glioblastoma multiforme (GBM) is the most malignant and lethal form of astrocytoma. GBM patients have a median survival time of approximately one year and therefore it is essential to identify novel targets and effective therapies. There is mounting evidence that microglia (specialized brain-resident macrophages) play a significant role in the development and progression of GBM tumors. We have established a microglia-glioma cell co-culture system consisting of normal microglia from C57Bl/6J mice and syngeneic GL261 glioma cells. We have demonstrated that microglia strongly stimulate the invasive behavior of GL261 cells in this system. Our preliminary data also indicate that the microglia significantly stimulate GL261 cell proliferation and resistance to ionizing radiation (IR) in these conditions. In a search for small molecule inhibitors that block the stimulatory effects of microglia on glioma cells, we have examined CNI-1493, a drug that is known to selectively interfere with macrophage function. We found that CNI-1493 potently inhibits microglia-stimulated GL261 invasion. We also examined the effect of intracranially administered CNI-1493 on orthotopic GL261 tumors in the presence or absence of fractionated whole brain irradiation (10 Gy total). We found that although CNI-1493 only has a marginal benefit in the absence of IR, it strongly stimulates animal survival in combination with IR: whereas IR treatment increases survival by 10 days, IR in combination with CNI-1493 treatment extends survival beyond 40 days. In conclusion, our observations support the notion that pharmacological targeting of microglia may be beneficial as adjuvant therapy in conjunction with ionizing radiation.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-503. doi:1538-7445.AM2012-LB-503
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