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A Rapid Screening Workflow to Identify Potential Combination Therapy for GBM using Patient-Derived Glioma Stem Cells
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Inhibition of PI3K/mTOR pathways in glioblastoma and implications for combination therapy with temozolomide

Gautam Prasad1, Theo Sottero, Xiaodong Yang

  • 1Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, USA. dhaaskogan@radonc.ucsf.edu

Neuro-Oncology
|February 15, 2011
PubMed

Insights

A novel PI3K/mTOR dual inhibitor, XL765, shows promise against glioblastoma multiforme (GBM). This targeted agent effectively reduced tumor growth and improved survival in preclinical models, both alone and with chemotherapy.

Area of Science:

  • Oncology
  • Pharmacology
  • Molecular Biology

Background:

  • Glioblastoma multiforme (GBM) exhibits significant molecular heterogeneity and infiltrative growth, leading to resistance against conventional and experimental therapies.
  • Targeted agents are increasingly explored in combination with standard treatments to overcome therapeutic challenges in GBM.

Purpose of the Study:

  • To evaluate the preclinical efficacy of XL765, an orally bioavailable PI3K/mTOR dual inhibitor, as a monotherapy and in combination with temozolomide (TMZ) against glioblastoma multiforme.
  • To assess the impact of XL765 on PI3K signaling pathways and tumor burden in in vitro and in vivo GBM models.

Main Methods:

  • In vitro cytotoxicity was assessed using colorimetric ATP-based assays, and downstream biochemical changes were analyzed by immunoblot.
  • In vivo studies utilized serially passaged human GBM xenografts (GBM 39) intracranially implanted in nude mice, with tumor burden monitored via bioluminescence imaging after luciferase expression.
  • XL765 was administered via oral gavage, and its effects were compared to control, TMZ alone, and the combination of XL765 + TMZ.

Main Results:

  • XL765 demonstrated dose-dependent cytotoxicity in vitro, with specific inhibition of PI3K signaling at cytotoxic concentrations.
  • In vivo, XL765 monotherapy significantly reduced median tumor bioluminescence (p = 0.001) and improved median survival (p = 0.05).
  • The combination of XL765 + TMZ resulted in a substantial reduction in tumor bioluminescence (p = 0.05) compared to TMZ alone, showing a trend toward improved survival.

Conclusions:

  • XL765 exhibits significant preclinical activity as a monotherapy against GBM xenografts.
  • Combining XL765 with temozolomide enhances therapeutic efficacy, suggesting a promising role for this dual inhibitor in combination regimens for GBM treatment.

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