Depletion of O6-alkylguanine-DNA alkyltransferase activity in mammalian tissues and human tumor xenografts in nude mice by treatment with O6-methylguanine

M. Eileen Dolan, Gregory L. Larkin, Hugh F. English, Anthony E. Pegg

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

We have previously shown that exposure of cells in culture to O6-methylguanine significantly reduces their level of the repair protein, O6-alkylguanine-DNA-alkyltransferase (AGT), thus rendering cells more sensitive to the cytotoxic effects of chemotherapeutic chloroethylating agents. Experiments were carried out in mice to determine whether the AGT content of tissues and tumors could be reduced by in vivo treatment with O6-methylguanine. There was a dose-dependent decrease in AGT activity in liver tissues of CD-1 mice to 24% of basal levels after four hourly intraperitoneal injections of O6-methylguanine (110 mg/kg). Although the decline in AGT activity in the liver was reversible, the activity remained at 75% of basal levels for up to 25 h after the final injection. The effect of O6-methylguanine treatment on AGT activity was measured in mouse tissues as well as human colonic carcinoma tumors (HT29 and BE) grown in Swiss athymic nude mice. The activity in the liver, kidney, and spleen of these mice decreased to 33%-35% of control levels, whereas the activity in HT29 tumors was likewise diminished to 25% of control levels after four hourly injections of O6-methylguanine (100 mg/kg). There was no enhancement of the tumoricidal effectiveness of chloroethylating agents on the HT29 tumor after O6-methylguanine treatment, probably due to a disproportionately higher level of AGT in human tissue than in murine tissue. However, these studies suggest that O6-methylguanine can be given in vivo to examine the role of the AGT protein in protecting against the toxic and carcinogenic effects of alkylating agents.

Original languageEnglish (US)
Pages (from-to)103-108
Number of pages6
JournalCancer Chemotherapy and Pharmacology
Volume25
Issue number2
DOIs
StatePublished - Mar 1 1989

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Heterografts
Nude Mice
Tumors
Tissue
Neoplasms
Liver
Level control
Therapeutics
Injections
Poisons
Alkylating Agents
O-(6)-methylguanine
DNA alkyltransferase
Intraperitoneal Injections
Proteins
Repair
Spleen
Cell Culture Techniques
Carcinoma
Kidney

All Science Journal Classification (ASJC) codes

  • Oncology
  • Toxicology
  • Pharmacology
  • Cancer Research
  • Pharmacology (medical)

Cite this

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title = "Depletion of O6-alkylguanine-DNA alkyltransferase activity in mammalian tissues and human tumor xenografts in nude mice by treatment with O6-methylguanine",
abstract = "We have previously shown that exposure of cells in culture to O6-methylguanine significantly reduces their level of the repair protein, O6-alkylguanine-DNA-alkyltransferase (AGT), thus rendering cells more sensitive to the cytotoxic effects of chemotherapeutic chloroethylating agents. Experiments were carried out in mice to determine whether the AGT content of tissues and tumors could be reduced by in vivo treatment with O6-methylguanine. There was a dose-dependent decrease in AGT activity in liver tissues of CD-1 mice to 24{\%} of basal levels after four hourly intraperitoneal injections of O6-methylguanine (110 mg/kg). Although the decline in AGT activity in the liver was reversible, the activity remained at 75{\%} of basal levels for up to 25 h after the final injection. The effect of O6-methylguanine treatment on AGT activity was measured in mouse tissues as well as human colonic carcinoma tumors (HT29 and BE) grown in Swiss athymic nude mice. The activity in the liver, kidney, and spleen of these mice decreased to 33{\%}-35{\%} of control levels, whereas the activity in HT29 tumors was likewise diminished to 25{\%} of control levels after four hourly injections of O6-methylguanine (100 mg/kg). There was no enhancement of the tumoricidal effectiveness of chloroethylating agents on the HT29 tumor after O6-methylguanine treatment, probably due to a disproportionately higher level of AGT in human tissue than in murine tissue. However, these studies suggest that O6-methylguanine can be given in vivo to examine the role of the AGT protein in protecting against the toxic and carcinogenic effects of alkylating agents.",
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Depletion of O6-alkylguanine-DNA alkyltransferase activity in mammalian tissues and human tumor xenografts in nude mice by treatment with O6-methylguanine. / Dolan, M. Eileen; Larkin, Gregory L.; English, Hugh F.; Pegg, Anthony E.

In: Cancer Chemotherapy and Pharmacology, Vol. 25, No. 2, 01.03.1989, p. 103-108.

Research output: Contribution to journalArticle

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AU - Dolan, M. Eileen

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