n-(4-azido-3-iodosalicyl)-n--beta-aminoethylvindesine and azidopine

We evaluated the multidrug resistance (MDR)-modulating effects of progesterone (PRG) and an orally active, structurally related compound, megestrol acetate (MA), in several MDR human cell lines. At 100 microM, both steroids inhibited the binding of a Vinca alkaloid photoaffinity analog to P-glycoprotein (P-gp) in MDR human neuroblastic SH-SY5Y/VCR cells [which show greater than 1500-fold resistance to vincristine (VCR) in the tetrazolium dye (MTT) assay]. However, 100 microM MA markedly enhanced the binding of [3H]-azidopine to P-gp in both SH-SY5Y/VCR cells and the MDR human epidermoid KB-GSV2 cell line (which displays 250-fold resistance to VCR in the MTT assay). PRG had little effect on the binding of [3H]-azidopine to P-gp. MA at low doses was more effective than PRG in sensitizing cells to VCR and enhancing their accumulation of [3H]-VCR. The highly resistant SH-SY5Y/VCR subline exhibited significant collateral sensitivity to both steroids. These data suggest that MA may be a clinically useful modulator of MDR.

Topics: Affinity Labels; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Cells, Cultured; Chemical Phenomena; Chemistry, Physical; Cricetinae; Cricetulus; Dihydropyridines; Drug Interactions; Drug Resistance; Epithelial Cells; Epithelium; Humans; Iodine Radioisotopes; Lung; Megestrol; Megestrol Acetate; Membrane Glycoproteins; Neuroblastoma; Progesterone; Tritium; Tumor Cells, Cultured; Vincristine; Vindesine