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Differential induction of cell death in human glioma cell lines by sodium nitroprusside
R V Blackburn1, S S Galoforo, C M Berns
1Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073, USA.
Background:
High grade gliomas represent very aggressive and lethal forms of human cancer, which often exhibit recurrence after surgical intervention and resistance to conventional chemotherapeutic and radiologic treatment. The clinically approved antihypertensive agent sodium nitroprusside (SNP) has been shown to induce cytotoxicity toward a number of carcinoma cell lines in vitro.
Methods:
Three human glioma cell lines were examined for susceptibility to the cytotoxic effects of SNP. The role of the protein kinase C (PKC)alpha gene in mediating resistance to SNP-induced killing in U343 cells was investigated using antisense oligonucleotide inhibition. Stable transfection and overexpression of the PKCalpha gene in the SNP-susceptible cell line U251 was performed to further implicate PKCalpha as a mediating factor in SNP cytotoxicity. In addition, the presence of bcl-2 protein in these cells was examined for possible correlation(s) with resistance to SNP.
Results:
Exposure of U251 cells and LN-Z308 cells to 0.5 mM SNP resulted in significant cytotoxicity over a 72-hour period. U343 cells were resistant to SNP killing. U343 cells were shown to exhibit higher basal levels of PKCalpha and bcl-2 than either U251 or LN-Z308 cells. bcl-2 expression and resistance to SNP toxicity both were decreased by the introduction of PKCalpha antisense oligonucleotides into U343 cells. Conversely, enhanced PKC activity in PKCalpha-transfected U251 clones was associated with increased bcl-2 expression and greater resistance to SNP-induced toxicity relative to control transfected cells.
Conclusions:
SNP can induce cytotoxicity in glioma cells. The susceptibility of these glioma cells to nitroprusside-induced killing appears to be correlated inversely with bcl-2 and PKC activity. bcl-2 levels in these cells can be altered through modulation of PKC signaling, specifically, by induction or inhibition of PKCalpha. These in vitro results provide an interesting basis for further study into the potential use of SNP for treatment of human gliomas in patients receiving combination therapy with conventional chemotherapeutic agents that exhibit PKC inhibitory activity.
Insights
Sodium nitroprusside (SNP) shows cytotoxicity in glioma cells, with resistance linked to protein kinase C (PKC)alpha and bcl-2 activity. Modulating PKCalpha impacts bcl-2 levels and SNP sensitivity, suggesting potential combination therapies.
Area of Science:
- Neuro-oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- High-grade gliomas are aggressive cancers with poor prognoses.
- Recurrence and resistance to standard treatments are common challenges.
- Sodium nitroprusside (SNP), an antihypertensive, demonstrates in vitro cytotoxicity against carcinoma cells.
Purpose of the Study:
- To investigate the cytotoxic effects of SNP on human glioma cell lines.
- To determine the role of protein kinase C (PKC)alpha in mediating resistance to SNP.
- To explore the correlation between bcl-2 protein expression and SNP resistance.
Main Methods:
- Examined SNP susceptibility in three human glioma cell lines.
- Utilized antisense oligonucleotide inhibition to study PKCalpha's role in SNP resistance.
- Overexpressed PKCalpha in a susceptible cell line to confirm its mediating role.
- Assessed bcl-2 protein presence and its correlation with SNP resistance.
Main Results:
- SNP induced significant cytotoxicity in U251 and LN-Z308 glioma cells.
- U343 cells exhibited resistance to SNP, with higher basal levels of PKCalpha and bcl-2.
- Inhibiting PKCalpha in U343 cells decreased bcl-2 expression and enhanced SNP sensitivity.
- Overexpressing PKCalpha in U251 cells increased bcl-2 and conferred greater SNP resistance.
Conclusions:
- SNP demonstrates cytotoxicity against glioma cells.
- Glioma cell susceptibility to SNP is inversely correlated with bcl-2 and PKC activity.
- PKCalpha signaling modulates bcl-2 levels, influencing SNP sensitivity.
- These findings support further research into SNP as a potential adjunct therapy for gliomas.
