Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report a murine leukemia cell variant (L1210/DDP), selected for cisplatin (DDP) resistance, to be cross-resistant to methotrexate (MTX). Cross-resistance of L1210 cells to DDP and MTX has been observed by others, and has also been recorded in P388 murine leukemia and SSC-25 human squamous carcinoma cells. We demonstrated that MTX resistance is not due to dihydrofolate reductase (DHFR) gene amplification, increased DHFR enzyme activity or decreased MTX binding to the target enzyme. Of the mechanisms commonly proposed for MTX resistance, only differences in transport were observed when comparing sensitive (L1210/0) and resistant (L1210/DDP) cells. Our results suggest that MTX resistance in L1210/DDP cells is due to altered methotrexate uptake.
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PMID:Investigations on the mechanisms of methotrexate resistance in a cisplatin-resistant L1210 murine leukemia cell subline. 854 79

Development of resistance to cisplatin in previously treatment-responsive malignancies is a major obstacle to successful treatment. Enhanced DNA repair as well as enhanced replicative bypass of DNA adducts have been suggested to play a role in the development of resistance to cisplatin. However, the relative contribution of these mechanisms is unknown. Second generation platinum compounds containing the 1,2-diaminocyclohexane (dach) carrier ligand have been of particular interest in the studies of resistance mechanisms since they have been effective in treatment of cells resistant to cisplatin. We have investigated the formation and repair of interstrand crosslinks (ICL) in the mouse leukemia cell line L1210/0 and its carrier ligand specific resistant derivatives L1210/DDP and L1210/DACH after treatment with ethylenediamine (en)-Pt and diaminocyclohexane (dach)-Pt compounds. ICL in the overall genome were examined using a modification of the alkaline elution assay. A Southern blot technique was employed for the study of ICL in specific regions of the genome. In the overall genome we found decreased formation of ICL with either -en or -dach carrier ligands in the two resistant cell lines without carrier ligand specificity. Some carrier ligand specificity of ICL formation was observed in the dihydrofolate reductase (DHFR) gene, but it did not correlate with the carrier ligand specificity of resistance. At the level of the overall genome there was no difference in repair of ICL between the sensitive and the two resistant cell lines. When measured in the DHFR gene, however, there was enhanced repair of ICL in the two resistant cell lines compared with the sensitive cell line. The enhanced repair at the level of the gene did not display any carrier ligand specificity.
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PMID:Increased gene specific repair of cisplatin induced interstrand crosslinks in cisplatin resistant cell lines, and studies on carrier ligand specificity. 900 94