Reversal of MDR1-associated resistance to topotecan by PAK-200S, a new dihydropyridine analogue, in human cancer cell lines.

Abstract

Recent data suggest that expression of the membrane P170-glycoprotein (P-gp) may confer resistance to the topoisomerase-I-interactive agent topotecan. The present study describes the cellular effects of a new dihydropyridine analogue, PAK-200S, on P-gp-mediated resistance to topotecan in human breast and ovarian tumour cells. PAK-200S at a non-cytotoxic concentration of 2.0 microM completely reversed resistance to topotecan in P-gp-expressing MCF-7/adr (breast) and A2780/Dx5 (ovarian) tumour cells, respectively, with no effects on parental cells. Cellular pharmacokinetic studies by reversed-phase high-performance liquid chromatography analysis showed significantly lower cellular drug concentrations of the pharmacologically active closed-ring lactone of topotecan in multidrug-resistant cells than in parental cells. PAK-200S was effective in restoring the cellular lactone concentrations of topotecan in resistant MCF-7/adr cells to levels comparable to those obtained in parental cells. Furthermore, exposure of MCF-7/adr cells to topotecan in the presence of PAK-200S significantly increased the induction of protein-linked DNA breaks. PAK-200S did not alter nuclear topoisomerase I-mediated ex vivo pBR322 DNA plasmid unwinding activity and topoisomerase-I protein expression. These results suggest that reversal of P-gp-mediated resistance to topotecan by PAK-200S was related to the restoration of cellular drug concentrations of the active lactone form of topotecan rather than a direct effect on topoisomerase-I function.

• Authors: U Vanhoefer, M R Müller, R A Hilger, B Lindtner, U Klaassen, N Schleucher, Y M Rustum, S Seeber, A Harstrick
• Journal: British journal of cancer (Br J Cancer) Vol. 81 Issue 8 Pg. 1304-10 (Dec 1999) ISSN: 0007-0920 [Print] England
• PMID: 10604726 (Publication Type: Journal Article)

Chemical References

• ATP Binding Cassette Transporter, Subfamily B, Member 1
• Antineoplastic Agents
• Dihydropyridines
• PAK 200
• Topotecan
• DNA Topoisomerases, Type I
• DNA Topoisomerases, Type II

Topics

• ATP Binding Cassette Transporter, Subfamily B, Member 1 (genetics)
• Antineoplastic Agents (pharmacokinetics, pharmacology)
• Blotting, Western
• DNA Topoisomerases, Type I (metabolism)
• DNA Topoisomerases, Type II (metabolism)
• Dihydropyridines (pharmacology)
• Drug Resistance, Neoplasm (genetics)
• Drug Screening Assays, Antitumor
• Drug Synergism
• Humans
• Neoplasms (enzymology, genetics, pathology)
• Phenotype
• Topotecan (pharmacokinetics, pharmacology)
• Tumor Cells, Cultured