Expression of drug resistance-associated mdr-1, GST pi, and topoisomerase II genes during cell cycle traverse.
The expression of drug resistance-associated mdr-1, GST pi, and topoisomerase II genes was analyzed in cell cycle phase enriched populations of doxorubicin-resistant murine leukemic P388/R-84 cells. Flow cytometric analysis of bromodeoxyuridine (BrdU) incorporation and staining with anti-BrdU antibodies was used to confirm the purity of cell cycle phase enriched populations obtained by centrifugal elutriation. Doxorubicin (DOX) and daunorubicin (DNR) accumulation was significantly lower in S-phase cells, and coincubation with verapamil (VPL) or chlorpromazine (CPZ) enhanced DOX and DNR accumulation more in S-phase than in G1- and G2/M-phase cells. While the cellular content of mdr-1 and topoisomerase II mRNAs changed, GST pi mRNA content remained constant during the cell cycle. S-phase cells had about 3-fold higher mdr-1 mRNA content than G1- and G2/M-phase cells. In G1 cells, P-glycoprotein expression, as determined by C219 monoclonal antibody, was 12% less than that of S and G2/M cells. Topoisomerase II mRNA content increased with the progression of cell cycle and peaked in G2/M cells. These observations suggest that cell cycle stage related changes in expression of drug resistance markers may have a major bearing on chemosensitivity of drug-resistant cells.
Ramachandran
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C
Michigan Cancer Foundation, Detroit 48201.
Mead
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D
Wellham
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LL
Sauerteig
A
A
Krishan
A
A
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis; D000818:Animals; D002453:Cell Cycle / Q000235:genetics*; D002460:Cell Line / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D003630:Daunorubicin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005982:Glutathione Transferase / Q000235:genetics*; D007399:Interphase; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D012333:RNA, Messenger; D004317:Doxorubicin; D005982:Glutathione Transferase; D004250:DNA Topoisomerases, Type II; D003630:Daunorubicin