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O6-methylguanine-DNA methyltransferase and human cancer chemotherapy
1Department of Pathology, Academy of Military Medical Sciences, Beijing, PR China.
Abstract:
Two kinds of human tumor cell strains having different activity of O6-methylguanine-DNA methyltransferase (O6-MT) were transplanted into nude mice. Mice were then injected intraperitoneally (i.p.) with the bifunctional agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride(ACNU). The tumors with low O6-MT activity were quickly suppressed or cured. This result suggests that some tumors, if determined to have low O6-MT activity, might be cured if the host is treated with ACNU. This observation may open a new approach to experimental cancer chemotherapy. Treatment with ACNU of experimental animals bearing HeLaMR tumors (which have low O6-MT activity and are Mer-), resulted in the regression of the tumors or their disappearance. In animals bearing HeLaS3 tumors (which have high O6-MT activity and are Mer+) the tumors were hyperplastic.
Insights
Human tumors with low O6-methylguanine-DNA methyltransferase (O6-MT) activity were effectively treated with the chemotherapy drug ACNU. This suggests ACNU may be a promising experimental cancer therapy for specific tumor types.
Area of Science:
- Oncology
- Cancer Chemotherapy
- DNA Repair Mechanisms
Background:
- O6-methylguanine-DNA methyltransferase (O6-MT) is a DNA repair enzyme.
- The activity of O6-MT can vary between different human tumor cell strains.
- This enzyme plays a role in cellular resistance to DNA-damaging chemotherapy agents.
Purpose of the Study:
- To investigate the efficacy of the bifunctional agent ACNU against human tumor cell strains with differing O6-MT activity in vivo.
- To determine if O6-MT activity levels can predict tumor response to ACNU treatment.
- To explore a potential new strategy for experimental cancer chemotherapy based on O6-MT activity.
Main Methods:
- Two human tumor cell strains with distinct O6-MT activity levels (low and high) were utilized.
- These cell strains were transplanted into nude mice.
- Mice bearing tumors were treated with an intraperitoneal injection of the chemotherapeutic agent ACNU (1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride).
Main Results:
- Tumors exhibiting low O6-MT activity (HeLaMR, Mer-) showed significant suppression or complete cure following ACNU treatment.
- Tumors with high O6-MT activity (HeLaS3, Mer+) demonstrated hyperplasia, indicating resistance to ACNU.
- ACNU treatment led to tumor regression or disappearance in experimental animals with low O6-MT activity tumors.
Conclusions:
- Tumor O6-MT activity is a critical factor in determining sensitivity to ACNU chemotherapy.
- ACNU demonstrates potent anti-tumor effects against O6-MT-deficient human tumors in a preclinical model.
- This study highlights the potential of stratifying cancer patients based on O6-MT activity for ACNU-based experimental chemotherapy.