Direct reversal of DNA damage by mutant methyltransferase protein protects mice against dose-intensified chemotherapy and leads to in vivo selection of hematopoietic stem cells

Direct reversal of O6 adducts caused by chemotherapy agents is accomplished in mammalian cells by the protein O6-methylguanine DNA methyltransferase (MGMT). Some tumors overexpress MGMT and are resistant to alkylator therapy. One future approach to treatment of these tumors may rely on concurrent ph...

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Bibliographic Details
Published in:Cancer research (Chicago, Ill.) Ill.), 2000-09, Vol.60 (18), p.5187-5195
Main Authors: RAGG, Susanne, XU-WELLIVER, Meng, BAILEY, Jeff, D'SOUZA, Maria, COOPER, Ryan, CHANDRA, Saurabh, SESHADRI, Roopa, PEGG, Anthony E, WILLIAMS, David A
Format: Article
Language:English
Subjects:
1,3-bis(2-chloroethyl)-1-nitrosourea
3T3 Cells
Animals
Antineoplastic agents
Antineoplastic Combined Chemotherapy Protocols - pharmacology
Antineoplastic Combined Chemotherapy Protocols - toxicity
Biological and medical sciences
Bone Marrow Transplantation
Carmustine - administration & dosage
Chemotherapy
DNA Damage - physiology
DNA Repair
Dose-Response Relationship, Drug
Gene Transfer Techniques
Genetic Vectors - genetics
Guanine - administration & dosage
Guanine - analogs & derivatives
Hematopoietic Stem Cells - drug effects
Hematopoietic Stem Cells - enzymology
Hematopoietic Stem Cells - physiology
Humans
Medical sciences
Mice
Mice, Inbred C57BL
O-Methylguanine-DNA Methyltransferase - genetics
O-Methylguanine-DNA Methyltransferase - metabolism
O6-benzylguanine
O6-methylguanine DNA methyltransferase
Pharmacology. Drug treatments
Point Mutation
Rats
Retroviridae - genetics
Transduction, Genetic
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Summary:Direct reversal of O6 adducts caused by chemotherapy agents is accomplished in mammalian cells by the protein O6-methylguanine DNA methyltransferase (MGMT). Some tumors overexpress MGMT and are resistant to alkylator therapy. One future approach to treatment of these tumors may rely on concurrent pharmacological depletion of tumor MGMT with O6-benzylguanine (6-BG) and protection of sensitive tissues, such as hematopoietic stem and progenitor cells, using genetic modification with 6-BG-resistant MGMT mutants. We have used retroviral-mediated gene transfer to transduce murine hematopoietic bone marrow cells with MGMT point mutants showing resistance to 6-BG depletion in vitro. These mutants include proline to alanine and proline to lysine substitutions at the 140 position (P140A and P140K, respectively), which show 40- and 1000-fold resistance to 6-BG compared with wild-type (WT) MGMT. Lethally irradiated mice were reconstituted with murine stem cells transduced with murine stem cell virus retrovirus expressing each mutant, WT MGMT, or mock-infected cells and then treated with a combination of 30 mg/kg 6-BG and 10 mg/kg 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or with 40 mg/kg BCNU alone. Compared with mice treated with BCNU alone, significant myeloid toxicity and death occurred in mice reconstituted with mock-infected or WT MGMT (
ISSN:0008-5472
1538-7445