Clinical Cancer Research, Vol 1, Issue 11 1359-1368, Copyright © 1995 by American Association for Cancer Research

ARTICLES

Retroviral transfer of a bacterial alkyltransferase gene into murine bone marrow protects against chloroethylnitrosourea cytotoxicity

LC Harris, UK Marathi, CC Edwards, PJ Houghton, DK Srivastava, EF Vanin, BP Sorrentino and TP Brent
Department of Molecular Pharmacology, Division of Experimental Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

The chloroethylnitrosoureas (CENUs) are important antineoplastic drugs for which clinical utility has been restricted by the development of severe delayed myelosuppression in most patients. To investigate the potential of DNA repair proteins to reduce bone marrow sensitivity to the CENUs, we transferred the Escherichia coli ada gene, which encodes a Mr 39,000 O6-alkylguanine-DNA alkyltransferase (ATase), into murine bone marrow cells by the use of a high-titer ecotropic retrovirus. The ada-encoded ATase is resistant to O6-benzylguanine (O6-BG), a potent inhibitor of the mammalian ATases, thus affording the bone marrow an additional level of protection against CENUs. In methylcellulose cultures, ada-infected hematopoietic progenitor cells were twice as resistant as uninfected cells to the toxic effects of 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) following treatment with O6-BG. Although showing no obvious protective effects against leukopenia, overexpression of the bacterial ATase activity reduced the severity of anemia and thrombocytopenia in mice treated with O6-BG and BCNU. These effects, which were maximal at a BCNU dose of 12.5 mg/kg, were associated with improved survival when BCNU was given at this dose. At lower BCNU doses cytotoxicity was limited in both transduced and control mice, and at higher doses the protective effect was saturated due to cytotoxicity. These results suggest that ada gene therapy may be a feasible approach to amelioration of delayed myelosuppression following O6-BG plus CENU combination chemotherapy.

This article has been cited by other articles:

				R. Maze, C. Kurpad, A. E. Pegg, L. C. Erickson, and D. A. Williams Retroviral-Mediated Expression of the P140A, but not P140A/G156A, Mutant Form of O6-Methylguanine DNA Methyltransferase Protects Hematopoietic Cells against O6-Benzylguanine Sensitization to Chloroethylnitrosourea Treatment J. Pharmacol. Exp. Ther., September 1, 1999; 290(3): 1467 - 1474. [Abstract] [Full Text]

				J. A. Allay, H. T. Spencer, S. L. Wilkinson, J. A. Belt, R. L. Blakley, and B. P. Sorrentino Sensitization of Hematopoietic Stem and Progenitor Cells to Trimetrexate Using Nucleoside Transport Inhibitors Blood, November 1, 1997; 90(9): 3546 - 3554. [Abstract] [Full Text] [PDF]

				N. Chinnasamy, J. A. Rafferty, I. Hickson, J. Ashby, H. Tinwell, G. P. Margison, T. M. Dexter, and L. J. Fairbairn O6-Benzylguanine Potentiates the In Vivo Toxicity and Clastogenicity of Temozolomide and BCNU in Mouse Bone Marrow Blood, March 1, 1997; 89(5): 1566 - 1573. [Abstract] [Full Text] [PDF]

				J. S. Reese, O. N. Koc, K. M. Lee, L. Liu, J. A. Allay, W. P. Phillips Jr., and S. L. Gerson Retroviral transduction of a mutant methylguanine DNA methyltransferase gene into human CD34 cells confers resistance to O6-benzylguanine plus 1,3-bis(2-chloroethyl)-1-nitrosourea PNAS, November 26, 1996; 93(24): 14088 - 14093. [Abstract] [Full Text] [PDF]