Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue

Carolyn B. Hendricks, Eric K. Rowinsky, Louise B. Grochow, Ross C. Donehower, Scott H Kaufmann

Research output: Contribution to journalArticle

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Abstract

Topotecan (TPT, 9-dimethylaminomethyl-10-hydroxycamptothecin) is the first topoisomerase I-directed cytotoxic agent to enter clinical trials in the United States in two decades. The effect of P-glycoprotein (Pgp) overexpression on TPT cytotoxicity was examined in CHRC5 (colchicine-resistant) and AuxB1 (parental) Chinese hamster ovary cells. Examination of the IC50 values observed in colony-forming assays revealed that the CHRC5 cells were 15-fold (SD, ±3; n = 3) resistant to TPT after a 1-h exposure and 3.2-fold (SD, ±1.4; n = 4) resistant in continuous exposure experiments. Band depletion immunoblotting revealed that 4-fold higher concentrations of extracellular TPT were required to induce the formation of topo 1-DNA complexes in CHRCS cells as compared to AuxB1 cells. To assess the role of Pgp in this resistance, drug accumulation and cytotoxicity assays were repeated in the absence and presence of quinidine. Addition of quinidine enhanced TPT accumulation (measured by high-performance liquid Chromatograph) and diminished the IC50 for TPT to a greater extent in CHRCS cells than in AuxB1 cells. To examine whether similar effects could be detected in Pgp-expressing human cells, MCF-7/Adria1 breast cancer cells and KG1a human acute myelogenous leukemia cells were examined. Quinidine or verapamil enhanced TPT accumulation in both of these cell lines but had no effect in parental MCF-7 cells or a variety of human leukemia cell lines that do not overexpress Pgp. Cytotoxicity measurements performed by counting the number of surviving cells (MCF-7/Adria') or employing a modified, highly stable tetrazolium dye reduction assay (leukemia cell lines) revealed that quinidine diminished the IC50 for TPT in the Pgp-overexpressing cell lines but not in the control lines. These results suggest that Pgp overexpression diminishes TPT accumulation and TPT cytotoxicity in hamster and human cells. It should be stressed, however, that these effects were substantially smaller than the effects of Pgp overexpression on the accumulation and cytotoxicity of the anthracycline daunorubicin and the epipodophyllotoxin etoposide in the same cell lines.

Original languageEnglish (US)
Pages (from-to)2268-2278
Number of pages11
JournalCancer Research
Volume52
Issue number8
StatePublished - Apr 15 1992
Externally publishedYes

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Topotecan
Camptothecin
P-Glycoprotein
Quinidine
MCF-7 Cells
Cell Line
Inhibitory Concentration 50
Leukemia
9 alpha,11 alpha,15 alpha-trihydroxy-16-phenoxy-17,18,19,20-tetranorprosta-4,5,13-trienoic acid
Podophyllotoxin
Type I DNA Topoisomerase
Daunorubicin
Anthracyclines
Cytotoxins
Colchicine
Etoposide
Cricetulus
Immunoblotting
Drug Resistance
Acute Myeloid Leukemia

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue. / Hendricks, Carolyn B.; Rowinsky, Eric K.; Grochow, Louise B.; Donehower, Ross C.; Kaufmann, Scott H.

In: Cancer Research, Vol. 52, No. 8, 15.04.1992, p. 2268-2278.

Research output: Contribution to journalArticle

Hendricks, Carolyn B. ; Rowinsky, Eric K. ; Grochow, Louise B. ; Donehower, Ross C. ; Kaufmann, Scott H. / Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue. In: Cancer Research. 1992 ; Vol. 52, No. 8. pp. 2268-2278.
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