Multidrug resistance phenotype associated with selection of an aminopterin resistant dog kidney cell line.
A determination of the mechanisms of drug resistance in tumour cells is important for developing strategies to combat such resistance in persons receiving chemotherapy. This report describes a combined cellular, biochemical, and molecular analysis of a dog kidney cell line selected for resistance to increasing levels of the hydrophilic antifolate, aminopterin. Three distinct drug resistance phenotypes were observed in cells exhibiting high levels of aminopterin resistance. Two of these phenotypes were decreased aminopterin accumulation and increased levels of dihydrofolate reductase specific activity. The third drug resistance phenotype was noted initially as cross resistance to a variety of hydrophobic drugs indicating multidrug resistance. Biochemical assays demonstrated reduced accumulation of the hydrophobic fluorescent drug daunorubicin and of 3H-colchicine in the aminopterin resistant cells. These results were then correlated with increased levels of the multidrug resistance (mdr) gene product, P-glycoprotein, and mdr mRNA levels in the aminopterin resistant cells. However, experiments designed to prove a role for expression of the mdr gene in providing a degree of aminopterin resistance were unsuccessful. It is concluded that aminopterin selection in these dog kidney cells resulted in expression of at least three distinct drug resistance phenotypes and that one of these phenotypes, multidrug resistance, represented a secondary response to the aminopterin selection.
Turker
M S
MS
Department of Pathology, University of Kentucky College of Medicine, Lexington 40536.
Duffin
K Z
KZ
Smith
A C
AC
Martin
G M
GM
Martin
A W
AW
DiMartino
D L
DL
Kersey
D S
DS
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000630:Aminopterin / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D004285:Dogs; D004351:Drug Resistance / Q000235:genetics*; D007150:Immunohistochemistry; D007668:Kidney; D008562:Membrane Glycoproteins / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D013762:Tetrahydrofolate Dehydrogenase; D000630:Aminopterin; D003078:Colchicine