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Betulinic acid: a new cytotoxic agent against malignant brain-tumor cells
S Fulda1, I Jeremias, H H Steiner
1University Children's Hospital, Ulm, Germany.
Abstract:
Malignant brain tumors are the most common solid tumors in children. The overall prognosis for this group of patients is still poor, emphasizing the importance of more effective therapies. Betulinic acid (Bet A) has been described as a novel cytotoxic compound active against melanoma and neuroblastoma cells. Here we report that Bet A was active against medulloblastoma and glioblastoma cell lines. In addition, Bet A exerted cytotoxic activity against primary tumor cells cultured from patients in 4 of 4 medulloblastoma-tumor samples tested and in 20 of 24 glioblastoma-tumor samples. Since a small percentage of primary-glioblastoma-tumor cells (4/24) did not respond to Bet-A treatment, resistance to Bet A might occur. Induction of apoptosis by Bet A involved mitochondrial perturbations, since inhibition of the mitochondrial permeability transition by the mitochondrion-specific inhibitor bongkrekic acid (BA) reduced Bet-A-induced apoptosis. In addition, mitochondria undergoing Bet-A-induced permeability transition triggered DNA fragmentation in isolated nuclei. Cytochrome c was released from mitochondria of Bet-A-treated cells, and might be involved in activation of caspases. Following treatment with Bet A, caspase-8, caspase-3 and PARP were proteolytically processed. Inhibition of caspase cleavage by the broad-range caspase inhibitor zVAD.fmk strongly reduced Bet-A-induced apoptosis, indicating that apoptosis was mediated by activation of caspases. Since Bet A did not exhibit cytotoxicity against murine neuronal cells in vitro, these findings suggest that Bet A may be a promising new agent for the treatment of medulloblastoma and glioblastoma cells that clearly warrants further pre-clinical and clinical evaluation.
Insights
Betulinic acid (Bet A) shows promise as a new therapy for pediatric brain tumors like medulloblastoma and glioblastoma. This compound effectively kills cancer cells by inducing apoptosis through mitochondrial pathways, with minimal impact on healthy neurons.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Malignant brain tumors are the leading cause of cancer-related death in children, necessitating novel therapeutic strategies.
- Betulinic acid (Bet A), a natural compound, has demonstrated cytotoxic effects against certain cancer types, including melanoma and neuroblastoma.
Purpose of the Study:
- To investigate the efficacy of Betulinic acid (Bet A) against pediatric medulloblastoma and glioblastoma cell lines and primary tumor cells.
- To elucidate the mechanism of action of Bet A, focusing on its role in inducing apoptosis and its interaction with mitochondria and caspases.
Main Methods:
- Cytotoxicity assays were performed on medulloblastoma and glioblastoma cell lines and primary tumor cells.
- Mitochondrial permeability transition was assessed using bongkrekic acid (BA).
- Apoptosis induction was evaluated by measuring DNA fragmentation, cytochrome c release, and caspase activation (caspase-8, caspase-3, PARP) using zVAD.fmk.
Main Results:
- Betulinic acid (Bet A) exhibited significant cytotoxic activity against medulloblastoma and glioblastoma cell lines and a majority of primary tumor samples.
- Bet A-induced apoptosis involved mitochondrial perturbations, including the release of cytochrome c and activation of caspases.
- Bet A demonstrated no cytotoxicity against murine neuronal cells, suggesting potential therapeutic selectivity.
Conclusions:
- Betulinic acid (Bet A) is a potent agent against pediatric medulloblastoma and glioblastoma, acting through caspase-dependent apoptosis.
- The compound's selective toxicity towards cancer cells warrants further investigation for its clinical potential in treating these aggressive brain tumors.