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Published on: March 28, 2021
Cyclopamine sensitizes glioblastoma cells to temozolomide treatment through Sonic hedgehog pathway
Gabriela Basile Carballo1, Diana Matias2, Jessica Honorato Ribeiro1
1Laboratório de Biomedicina do Cérebro, Instituto Estadual do Cérebro Paulo Niemeyer (IECPN), Secretaria de Estado de Saúde, Rio de Janeiro, Brazil; Programa de Pós-Graduação em Anatomia Patológica, Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Aim:
Glioblastoma is an extremely aggressive glioma, resistant to radio and chemotherapy usually performed with temozolomide. One of the main reasons for glioblastoma resistance to conventional therapies is due to the presence of cancer stem-like cells. These cells could recapitulate some signaling pathways important for embryonic development, such as Sonic hedgehog. Here, we investigated if the inhibitor of the Sonic hedgehog pathway, cyclopamine, could potentiate the temozolomide effect in cancer stem-like cells and glioblastoma cell lines in vitro.
Main Methods:
The viability of glioblastoma cells exposed to cyclopamine and temozolomide treatment was evaluated by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while the induction of apoptosis was assessed by western blot. The stemness properties of glioma cells were verified by clonogenic and differentiation assay and the expression of stem cell markers were measured by fluorescence microscopy and western blot.
Key Findings:
The glioblastoma viability was reduced by cyclopamine treatment. Cyclopamine potentiated temozolomide treatment in glioblastoma cell lines by inducing apoptosis through activation of caspase-3 cleaved. Conversely, the combined treatment of cyclopamine and temozolomide potentiated the stemness properties of glioblastoma cells by inducing the expression of SOX-2 and OCT-4.
Significance:
Cyclopamine plays an effect on glioblastoma cell lines but also sensibilize them to temozolomide treatment. Thus, first-line treatment with Sonic hedgehog inhibitor followed by temozolomide could be used as a new therapeutic strategy for glioblastoma patients.
Insights
Cyclopamine enhances temozolomide efficacy in glioblastoma by increasing apoptosis. However, combined treatment boosts cancer stem cell properties, suggesting a complex therapeutic role for Sonic hedgehog inhibitors in glioblastoma treatment.
Area of Science:
- Neuro-oncology
- Cancer Stem Cell Biology
- Molecular Therapeutics
Background:
- Glioblastoma is a highly aggressive brain tumor resistant to standard treatments like temozolomide.
- Cancer stem-like cells contribute to treatment resistance by reactivating developmental pathways, including Sonic hedgehog.
- Targeting these pathways offers a potential strategy to overcome glioblastoma resistance.
Purpose of the Study:
- To investigate the effect of cyclopamine, a Sonic hedgehog pathway inhibitor, on glioblastoma cell lines.
- To determine if cyclopamine can enhance the efficacy of temozolomide in glioblastoma cancer stem-like cells.
- To evaluate the impact of combined cyclopamine and temozolomide treatment on glioblastoma cell viability, apoptosis, and stemness properties.
Main Methods:
- Cell viability assessed using MTT assays.
- Apoptosis induction evaluated via Western blot analysis for cleaved caspase-3.
- Stemness properties analyzed through clonogenic and differentiation assays.
- Expression of stem cell markers (SOX-2, OCT-4) measured by fluorescence microscopy and Western blot.
Main Results:
- Cyclopamine alone reduced glioblastoma cell viability.
- Combined cyclopamine and temozolomide treatment induced apoptosis, evidenced by increased cleaved caspase-3.
- Conversely, combined treatment paradoxically enhanced stemness properties, increasing SOX-2 and OCT-4 expression.
Conclusions:
- Cyclopamine demonstrates activity against glioblastoma cell lines and sensitizes them to temozolomide.
- The combined therapy's impact on stemness suggests a need for careful therapeutic sequencing.
- A strategy involving Sonic hedgehog inhibition followed by temozolomide warrants further investigation as a novel glioblastoma treatment approach.
