PTEN loss does not predict for response to RAD001 (everolimus) in a glioblastoma orthotopic xenograft test panel

Lin Yang, Michelle J. Clarke, Brett L. Carlson, Ann C. Mladek, Mark A. Schroeder, Paul Decker, Wenting Wu, Gasparj Kitange, Patrickt Grogan, Jennie M. Goble, Joon Uhm, Evanthia Galanis, Caterina Giannini, Heidi A. Lane, C. David James, Jann N Sarkaria

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Abstract

Purpose: Hyperactivation of the phosphatidylinositoi 3-kinase/Akt signaling through disruption of PTEN function is common in glioblastoma multiforme, and these genetic changes are predicted to enhance sensitivity to mammalian target of rapamycin (mTOR) inhibitors such as RAD001 (everolimus). Experimental Design: To test whether PTEN loss could be used as a predictive marker for mTOR inhibitor sensitivity, the response of 17 serially transplantable glioblastoma multiforme xenografts was evaluated in an orthotopic therapy evaluation model. Of these 17 xenograft lines, 7 have either genomic deletion or mutation of PTEN. Results: Consistent with activation of Akt signaling, there was a good correlation between loss of PTEN function and elevated levels of Akt phosphorylation. However, of the 7 lines with disrupted PTEN function, only 1 tumor line (GBM10) was significantly sensitive to RAD001 therapy (25% prolongation in median survival), whereas 1 of 10 xenograft lines with wild-type PTEN was significantly sensitive to RAD001 (GS22; 34% prolongation in survival). Relative to placebo, 5 days of RAD001 treatment was associated with a marked 66% reduction in the MIB1 proliferation index in the sensitive GBM10 line (deleted PTEN) compared with a 25% and 7% reduction in MIB1 labeling index in the insensitive GBM14 (mutant PTEN) and GBM15 (wild-type PTEN) lines, respectively. Consistent with a cytostatic antitumor effect, bioluminescent imaging of luciferase- transduced intracranial GBM10 xenografts showed slowed tumor growth without significant tumor regression during RAD001 therapy. Conclusion: These data suggest that loss of PTEN function is insufficient to adequately predict responsiveness to mTOR inhibitors in glioblastoma multiforme.

Original languageEnglish (US)
Pages (from-to)3993-4001
Number of pages9
JournalClinical Cancer Research
Volume14
Issue number12
DOIs
StatePublished - Jun 15 2008

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ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Yang, L., Clarke, M. J., Carlson, B. L., Mladek, A. C., Schroeder, M. A., Decker, P., Wu, W., Kitange, G., Grogan, P., Goble, J. M., Uhm, J., Galanis, E., Giannini, C., Lane, H. A., James, C. D., & Sarkaria, J. N. (2008). PTEN loss does not predict for response to RAD001 (everolimus) in a glioblastoma orthotopic xenograft test panel. Clinical Cancer Research, 14(12), 3993-4001. https://doi.org/10.1158/1078-0432.CCR-07-4152