Related Experiment Videos
O6-alkylguanine-DNA alkyltransferase activity of human malignant glioma and its clinical implications
1Department of Neurosurgery, Hiroshima University School of Medicine, Japan.
Abstract:
Activity of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) is an important determinant of responsiveness of tumor cells to chloroethylnitrosoureas (CENUs), representative chemotherapeutic agents for primary malignant gliomas. In order to assess the real states of this repair protein in human malignant gliomas, we assayed AGT activity in surgically extirpated 42 malignant glioma samples and studied the distribution of the activity under certain clinical conditions. There were wide variations in AGT activity between individuals. No significant difference in AGT activity on average was seen either between glioblastoma and anaplastic astrocytoma, nor between primary and recurrent tumors. Among 42 malignant gliomas, 7 samples (16.7%) had low AGT activity less than 0.1 pmoles/mg protein. In the case of glioblastoma, tumors possessing higher AGT activity tended to be less responsive to post-operation remission-induction therapy including CENUs. The result of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) chemosensitivity assay by using the corresponding surgical specimens suggested a close relationship between cellular resistance to CENUs and AGT activity. It was found to be unlikely that a short term administration of CENUs had a significant effect on AGT activity of brain tumors in human body. We could detect a bit of definite evidences of the relevance of AGT to resistance to CENUs and need to conduct further investigations for other resistance factors.
Insights
O6-alkylguanine-DNA alkyltransferase (AGT) activity varies widely in malignant gliomas. Higher AGT levels correlate with resistance to chloroethylnitrosoureas (CENUs) chemotherapy, suggesting AGT
Area of Science:
- Neuro-oncology
- Cancer Biology
- Pharmacology
Background:
- O6-alkylguanine-DNA alkyltransferase (AGT) is crucial for DNA repair.
- AGT activity influences tumor cell response to chloroethylnitrosoureas (CENUs), key chemotherapy for malignant gliomas.
- Understanding AGT levels in gliomas is vital for treatment efficacy.
Purpose of the Study:
- To measure AGT activity in human malignant gliomas.
- To investigate the relationship between AGT activity and clinical factors.
- To assess AGT's role in chemoresistance to CENUs.
Main Methods:
- Assayed AGT activity in 42 surgically extirpated malignant glioma samples.
- Analyzed AGT activity distribution across different glioma types and stages.
- Utilized MTT chemosensitivity assays on surgical specimens.
Main Results:
- Significant inter-individual variation in AGT activity was observed.
- No significant difference in AGT activity between glioblastoma and anaplastic astrocytoma, or primary and recurrent tumors.
- 16.7% of gliomas exhibited low AGT activity (<0.1 pmoles/mg protein).
- Higher AGT activity in glioblastomas correlated with reduced responsiveness to CENU-based therapy.
- Chemosensitivity assays indicated a strong link between cellular resistance to CENUs and AGT activity.
- Short-term CENU administration did not significantly alter brain tumor AGT activity.
Conclusions:
- AGT activity is a significant factor in malignant glioma response to CENUs.
- Elevated AGT levels contribute to chemoresistance in gliomas.
- Further research is needed to identify other resistance mechanisms beyond AGT.