Resveratrol targeting of AKT and p53 in glioblastoma and glioblastoma stem-like cells to suppress growth and infiltration

OBJECTIVE Glioblastoma multiforme (GBM) is an aggressive brain cancer with median survival of less than 2 years with current treatment. Glioblastomas exhibit extensive intratumoral and interpatient heterogeneity, suggesting that successful therapies should produce broad anticancer activities. Therefore, the natural nontoxic pleiotropic agent, resveratrol, was studied for antitumorigenic effects against GBM. METHODS Resveratrol's effects on cell proliferation, sphere-forming ability, and invasion were tested using multiple patient-derived GBM stem-like cell (GSC) lines and established U87 glioma cells, and changes in oncogenic AKT and tumor suppressive p53 were analyzed. Resveratrol was also tested in vivo against U87 glioma flank xenografts in mice by using multiple delivery methods, including direct tumor injection. Finally, resveratrol was delivered directly to brain tissue to determine toxicity and achievable drug concentrations in the brain parenchyma. RESULTS Resveratrol significantly inhibited proliferation in U87 glioma and multiple patient-derived GSC lines, demonstrating similar inhibitory concentrations across these phenotypically heterogeneous lines. Resveratrol also inhibited the sphere-forming ability suggesting anti-stem cell effects. Additionally, resveratrol blocked U87 glioma and GSC invasion in an in vitro Matrigel Transwell assay at doses similar to those mediating antiproliferative effects. In U87 glioma cells and GSCs, resveratrol reduced AKT phosphorylation and induced p53 expression and activation that led to transcription of downstream p53 target genes. Resveratrol administration via oral gavage or ad libitum in the water supply significantly suppressed GBM xenograft growth; intratumoral or peritumoral resveratrol injection further suppressed growth and approximated tumor regression. Intracranial resveratrol injection resulted in 100-fold higher local drug concentration compared with intravenous delivery, and with no apparent toxicity. CONCLUSIONS Resveratrol potently inhibited GBM and GSC growth and infiltration, acting partially via AKT deactivation and p53 induction, and suppressed glioblastoma growth in vivo. The ability of resveratrol to modulate AKT and p53, as well as reportedly many other antitumorigenic pathways, is attractive for therapy against a genetically heterogeneous tumor such as GBM. Although resveratrol exhibits low bioavailability when administered orally or intravenously, novel delivery methods such as direct injection (i.e., convection-enhanced delivery) could potentially be used to achieve and maintain therapeutic doses in the brain. Resveratrol's nontoxic nature and broad anti-GBM effects make it a compelling candidate to supplement current GBM therapies.

Myelin-forming cell-specific cadherin-19 is a marker for minimally infiltrative glioblastoma stem-like cells

OBJECT

Glioblastoma stem-like cells (GSCs) exhibit stem-like properties, are highly efficient at forming tumor xenografts, and are resistant to many current therapies. Current molecular identifiers of GSCs are scarce and controversial. The authors describe differential cell-surface gene expression profiling to identify GSC-specific markers.

METHODS

Independent human GSC lines were isolated and maintained in standard neural stem cell (NSC) media and were validated for self-renewal, multipotent differentiation, and tumor initiation properties. Candidate upregulated GSCspecific plasma membrane markers were identified through differential Affymetrix U133 Plus 2.0 Array gene expression profiling of GSCs, human NSCs (hNSCs), normal brain tissue, and primary/recurrent glioblastoma multiforme samples. Results were validated by using comparative quantitative reverse transcription polymerase chain reaction and Western blot analysis of GSCs, hNSCs, normal human astrocytes, U87 glioma cell line, and patient-matched serum-cultured glioblastoma multiforme samples.

RESULTS

A candidate GSC-specific signature of 19 upregulated known and novel plasma membrane-associated genes was identified. Preferential upregulation of these plasma membrane-linked genes was validated by quantitative polymerase chain reaction. Cadherin-19 (CDH19) protein expression was enhanced in minimally infiltrative GSC lines.

CONCLUSIONS

Gene expression profiling of GSCs has shown CDH19 to be an exciting new target for drug development and study of GBM tumorigenesis.