Pharmacological characterization of N-substituted phenoxazines directed toward reversing Vinca alkaloid resistance in multidrug-resistant cancer cells

J. K. Horton, K. N. Thimmaiah, F. C. Harwood, J. F. Kuttesch, P. J. Houghton

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Previously we reported the synthesis and partial characterization of 21 N10-substituted phenoxazines in reversing Vinca alkaloid resistance. Here we report on a subset of these compounds; we have compared their activities in increasing Vinca alkaloid accumulation and reversing drug resistance in KB-Ch(R)8-5 and GC3/c1 (human colon carcinoma) cell lines. Results demonstrated that 1) N-substituted phenoxazines increase accumulation of vinblastine; 2) within this series, there is little correlation or ranking of activity between the two cell lines when Vinca alkaloid accumulation is compared at equal concentrations of modulator; 3) N-substituted phenoxazines demonstrate both quantitative and qualitative differences, compared with verapamil, a standard modulator; and 4) the series includes at least two compounds, 10-[3'-[N-bis(hydroxyethyl)amino]propyl]phenoxazine and 10-(N- piperidinoacetyl)phenoxazine, which increase Vinca alkaloid accumulation but do not significantly inhibit efflux. Additionally, certain of these multidrug resistance modulators significantly enhance accumulation (8-50-fold) of Vinca alkaloids in cell lines with very low or undetectable P-glycoprotein levels, where verapamil has little activity. It is concluded that at least part of the activity of some of these N-substituted phenoxazine modulators may be mediated through a P-glycoprotein-independent mechanism.

Original languageEnglish (US)
Pages (from-to)552-559
Number of pages8
JournalMolecular pharmacology
Volume44
Issue number3
StatePublished - 1993
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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