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GSK-3beta inhibition enhances sorafenib-induced apoptosis in melanoma cell lines
David J Panka1, Daniel C Cho, Michael B Atkins
1Division of Oncology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
Abstract:
Glycogen synthase kinase-3beta (GSK-3beta) can participate in the induction of apoptosis or, alternatively, provide a survival signal that minimizes cellular injury. We previously demonstrated that the multikinase inhibitor sorafenib induces apoptosis in melanoma cell lines. In this report, we show that sorafenib activates GSK-3beta in multiple subcellular compartments and that this activation undermines the lethality of the drug. Pharmacologic inhibition and/or down-modulation of the kinase enhances sorafenib-induced apoptosis as determined by propidium iodide staining and by assessing the mitochondrial release of apoptosis-inducing factor and Smac/DIABLO. Conversely, the forced expression of a constitutively active form of the enzyme (GSK-3beta(S9A)) protects the cells from the apoptotic effects of the drug. This protective effect is associated with a marked increase in basal levels of Bcl-2, Bcl-x(L), and survivin and a diminution in the degree to which these anti-apoptotic proteins are down-modulated by sorafenib exposure. Sorafenib down-modulates the pro-apoptotic Bcl-2 family member Noxa in cells with high constitutive GSK-3beta activity. Pharmacologic inhibition of GSK-3beta prevents the disappearance of Noxa induced by sorafenib and enhances the down-modulation of Mcl-1. Down-modulation of Noxa largely eliminates the enhancing effect of GSK-3 inhibition on sorafenib-induced apoptosis. These data provide a strong rationale for the use of GSK-3beta inhibitors as adjuncts to sorafenib treatment and suggest that preservation of Noxa may contribute to their efficacy.
Insights
Inhibiting glycogen synthase kinase-3beta (GSK-3beta) enhances sorafenib-induced apoptosis in melanoma by preserving the pro-apoptotic protein Noxa. This suggests combining GSK-3beta inhibitors with sorafenib may improve melanoma treatment efficacy.
Area of Science:
- Oncology
- Molecular Biology
- Cell Death Signaling
Background:
- Glycogen synthase kinase-3beta (GSK-3beta) plays a dual role in apoptosis and cell survival.
- Sorafenib, a multikinase inhibitor, induces apoptosis in melanoma cells.
- GSK-3beta activity can influence the sensitivity of cancer cells to apoptosis-inducing drugs.
Purpose of the Study:
- To investigate the role of GSK-3beta activation in mediating melanoma cell response to sorafenib.
- To determine if modulating GSK-3beta activity can enhance sorafenib-induced apoptosis.
- To elucidate the molecular mechanisms by which GSK-3beta affects sorafenib lethality.
Main Methods:
- Utilized pharmacologic inhibition and genetic manipulation (forced expression) of GSK-3beta.
- Assessed apoptosis using propidium iodide staining and mitochondrial release of apoptosis-inducing factor and Smac/DIABLO.
- Analyzed the expression levels of key apoptosis regulators, including Bcl-2 family proteins (Bcl-2, Bcl-x(L), survivin, Noxa, Mcl-1).
Main Results:
- Sorafenib activates GSK-3beta, which paradoxically reduces its apoptotic effect.
- Inhibition of GSK-3beta significantly enhances sorafenib-induced apoptosis.
- GSK-3beta activity influences the expression of anti-apoptotic proteins (Bcl-2, Bcl-x(L), survivin) and the pro-apoptotic protein Noxa.
- Preservation of Noxa by GSK-3beta inhibition is critical for the enhanced apoptotic response to sorafenib.
Conclusions:
- GSK-3beta activation undermines sorafenib's lethality in melanoma cells.
- Inhibiting GSK-3beta represents a promising therapeutic strategy to potentiate sorafenib efficacy.
- Targeting GSK-3beta, potentially through Noxa preservation, offers a rationale for combination therapy in melanoma treatment.
