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1.  Antiangiogenic Effects of Noscapine Enhance Radioresponse for GL261 Tumors 
Purpose
To determine whether the tubulin-binding drug noscapine could enhance radiosensitivity of GL261 glioma tumors by inhibiting tumor angiogenesis.
Methods and Materials
The human T98G and murine GL261 glioma cell lines treated with noscapine, radiation, or both were assayed for clonogenic survival. Mice with established GL261 hind limb tumors were treated with noscapine, radiation or both to evaluate the effect of noscapine on radioresponse. In a separate experiment with the same treatment groups, 7 days after radiation tumors were resected and immunostained to measure proliferation rate, apoptosis and angiogenic activity.
Results
Noscapine reduced clonogenic survival without enhancement of radiosensitivity in vitro. Noscapine combined with radiation significantly increased tumor growth delay: 5, 8, 13, 18 days for control, noscapine alone, radiation alone, and the combination treatment, respectively (p < 0.001). To assess the effect of the combination of noscapine plus radiation on the tumor vasculature, tubule formation by the murine endothelial 2H11 cells was tested. Noscapine with radiation significantly inhibited tubule formation compared with radiation alone. By immunohistochemistry, tumors treated with the combination of noscapine plus radiation showed a decrease in BrdU incorporation, an increase in apoptosis by TUNEL and a decrease in tumor vessel density compared with tumors treated with radiation alone.
Conclusion
Noscapine enhanced the sensitivity of GL261 glioma tumors to radiation resulting in a significant tumor growth delay. These findings are clinically relevant, particularly in view of the mild toxicity profile of this drug.
doi:10.1016/j.ijrobp.2008.04.020
PMCID: PMC2572218  PMID: 18640497
Noscapine; glioma; GL261 mouse model; angiogenesis; radioresponse
2.  Flavopiridol downregulates hypoxia-mediated hypoxia-inducible factor-1α expression in human glioma cells by a proteasome-independent pathway: Implications for in vivo therapy1 
Neuro-Oncology  2005;7(3):225-235.
Angiogenesis is a critical step required for sustained tumor growth and tumor progression. The stimulation of endothelial cells by cytokines secreted by tumor cells such as vascular endothelial growth factor (VEGF) induces their proliferation and migration. This is a prominent feature of high-grade gliomas. The secretion of VEGF is greatly upregulated under conditions of hypoxia because of the transcription factor hypoxia-inducible factor (HIF)-1α, which controls the expression of many genes, allowing rapid adaptation of cells to their hypoxic microenvironment. Flavopiridol, a novel cyclin-dependent kinase inhibitor, has been attributed with antiangiogenic properties in some cancer cell lines by its ability to inhibit VEGF production. Here, we show that flavopiridol treatment of human U87MG and T98G glioma cell lines decreases hypoxia-mediated HIF-1α expression, VEGF secretion, and tumor cell migration. These in vitro results correlate with reduced vascularity of intracranial syngeneic GL261 gliomas from animals treated with flavopiridol. In addition, we show that flavopiridol downregulates HIF-1α expression in the presence of a proteasome inhibitor, an agent that normally results in the accumulation and overexpression of HIF-1α. The potential to downregulate HIF-1α expression with flavopiridol treatment in combination with a proteasome inhibitor makes this an extremely attractive anticancer treatment strategy for tumors with high angiogenic activity, such as gliomas.
doi:10.1215/S1152851704000997
PMCID: PMC1871916  PMID: 16053697
flavopiridol; proteasome inhibitor; hypoxia; HIF-1α; VEGF; glioma

Results 1-2 (2)