Clinical Cancer Research, Vol 3, Issue 2 301-307, Copyright © 1997 by American Association for Cancer Research

ARTICLES

Retroviral transfer of a bacterial alkyltransferase gene (ada) into human bone marrow cells protects against O6-benzylguanine plus 1, 3-bis(2-chloroethyl)-1-nitrosourea cytotoxicity

UK Marathi, LC Harris, CC Venable and TP Brent
Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

The antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) is limited by the O6-alkylguanine-DNA alkyltransferase (ATase) in tumor cells and by delayed myelosuppression. Inactivation of neoplastic ATase by O6-benzylguanine (BG) improves the therapeutic index for BCNU. We have demonstrated previously that BG + BCNU-induced myelosuppression in mice is reduced by expression of the BG-resistant ATase ada in murine bone marrow. We have now generated an amphotropic retrovirus containing the ada gene and tested the effectiveness of ada expression in preventing BG + BCNU cytotoxicity in human hematopoietic progenitor cells. A retroviral producer clone with a biological titer of 6.5 x 10(4) colony-forming units/ml and 4.4 pmol ATase/mg protein was used for transduction of bone marrow. Cocultivation of these ada producer cells with progenitor cells from six normal individuals resulted in 1.9-3. 9-fold protection against BG + BCNU-induced cytotoxicity in committed progenitor cell assays. Furthermore, this cytoprotective effect was associated with a high transduction efficiency (40%) and a 2-fold increase of ATase activity in the surviving committed progenitor cell colonies. These data provide a basis for testing the clinical effectiveness of retroviral ada gene transfer into hematopoietic cells to increase the therapeutic index of BG + BCNU.

This article has been cited by other articles:

				D. M. Kokkinakis, D. B. Bocangel, S. C. Schold, R. C. Moschel, and A. E. Pegg Thresholds of O6-Alkylguanine-DNA Alkyltransferase which Confer Significant Resistance of Human Glial Tumor Xenografts to Treatment with 1,3-Bis(2-chloroethyl)-1-nitrosourea or Temozolomide Clin. Cancer Res., February 1, 2001; 7(2): 421 - 428. [Abstract] [Full Text]

				D. M. Landis and L. A. Loeb Random Sequence Mutagenesis and Resistance to 5-Fluorouridine in Human Thymidylate Synthases J. Biol. Chem., October 2, 1998; 273(40): 25809 - 25817. [Abstract] [Full Text] [PDF]