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Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue.
Cancer Res. 1992 Apr 15; 52(8):2268-78.CR

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 I-DNA complexes in CHRC5 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 chromatography) and diminished the IC50 for TPT to a greater extent in CHRC5 cells than in AuxB1 cells. To examine whether similar effects could be detected in Pgp-expressing human cells, MCF-7/Adriar 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/Adriar) 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.

Authors+Show Affiliations

Johns Hopkins Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

1348448

Citation

Hendricks, C B., et al. "Effect of P-glycoprotein Expression On the Accumulation and Cytotoxicity of Topotecan (SK&F 104864), a New Camptothecin Analogue." Cancer Research, vol. 52, no. 8, 1992, pp. 2268-78.
Hendricks CB, Rowinsky EK, Grochow LB, et al. Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue. Cancer Res. 1992;52(8):2268-78.
Hendricks, C. B., Rowinsky, E. K., Grochow, L. B., Donehower, R. C., & Kaufmann, S. H. (1992). Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue. Cancer Research, 52(8), 2268-78.
Hendricks CB, et al. Effect of P-glycoprotein Expression On the Accumulation and Cytotoxicity of Topotecan (SK&F 104864), a New Camptothecin Analogue. Cancer Res. 1992 Apr 15;52(8):2268-78. PubMed PMID: 1348448.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue. AU - Hendricks,C B, AU - Rowinsky,E K, AU - Grochow,L B, AU - Donehower,R C, AU - Kaufmann,S H, PY - 1992/4/15/pubmed PY - 1992/4/15/medline PY - 1992/4/15/entrez SP - 2268 EP - 78 JF - Cancer research JO - Cancer Res VL - 52 IS - 8 N2 - 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 I-DNA complexes in CHRC5 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 chromatography) and diminished the IC50 for TPT to a greater extent in CHRC5 cells than in AuxB1 cells. To examine whether similar effects could be detected in Pgp-expressing human cells, MCF-7/Adriar 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/Adriar) 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. SN - 0008-5472 UR - https://www.unboundmedicine.com/medline/citation/1348448/Effect_of_P_glycoprotein_expression_on_the_accumulation_and_cytotoxicity_of_topotecan__SK&F_104864__a_new_camptothecin_analogue_ L2 - http://cancerres.aacrjournals.org/cgi/pmidlookup?view=long&pmid=1348448 DB - PRIME DP - Unbound Medicine ER -