Purine salvage rescue by xanthine-guanine phosphoribosyltransferase (XGPRT) potentiates methotrexate resistance conferred by transfer of a mutated dihydrofolate reductase gene.
We have previously shown that successful gene transfer of a mutated dihydrofolate reductase (DHFR) cDNA confers resistance to methotrexate (MTX) upon infected cells. We constructed a retrovirus vector, DC/SV6S31GPT, which carries both the Escherichia coli xanthine-guanine phosphoribosyltransferase gene and the mutated Serine 31 DHFR gene. Mouse fibroblast NIH3T3 cells infected with DC/SV6S31 GPT are more resistant to MTX than cells infected with DC/SV6S31, which carries the Serine 31 DHFR and the neomycin resistance gene cDNA. The mechanism of this augmented resistance is the increased salvaging of purines due to expression of xanthine-guanine phosphoribosyltransferase, as the augmentation does not occur when dialyzed serum, containing little xanthine or guanine, is used for cytotoxicity assays. These results indicate that coexpression of a metabolically related gene can potentiate the resistance carried by a drug resistance gene. This vector may be useful in clinical gene therapy to protect bone marrow from the toxic effects of MTX.
Mineishi
S
S
Program of Molecular Pharmacology and Experimental Therapeutics and Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. sxm@heme.medicine.wisc.edu
Nakahara
S
S
Takebe
N
N
Zhao
S C
SC
Banerjee
D
D
Bertino
J R
JR
D016475:3T3 Cells; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001483:Base Sequence; D015152:Blotting, Northern; D001854:Bone Marrow Cells; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D008297:Male; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010430:Pentosyltransferases / Q000235:genetics*; D011687:Purines / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D013866:Thioguanine / Q000494:pharmacology
D000964:Antimetabolites, Antineoplastic; D017931:DNA Primers; D011687:Purines; D013762:Tetrahydrofolate Dehydrogenase; D010430:Pentosyltransferases; C024827:xanthine phosphoribosyltransferase; D013866:Thioguanine; D008727:Methotrexate