ABSTRACT
One of the major causes of chemotherapy failure in cancer treatment is multidrug resistance (MDR) which is mediated by the ABCB1/P-glycoprotein. Previously, through the use of an extensive screening process, we found that vardenafil, a phosphodiesterase 5 (PDE-5) inhibitor significantly reverses MDR in ABCB1 overexpressing cancer cells, and its efficacy was greater than that of tadalafil, another PDE-5 inhibitor. The present study was designed to determine the reversal mechanisms of vardenafil and tadalafil on ABC transporters-mediated MDR. Vardenafil or tadalafil alone, at concentrations up to 20 µM, had no significant toxic effects on any of the cell lines used in this study, regardless of their membrane transporter status. However, vardenafil when used in combination with anticancer substrates of ABCB1, significantly potentiated their cytotoxicity in ABCB1 overexpressing cells in a concentration-dependent manner, and this effect was greater than that of tadalafil. The sensitivity of the parenteral cell lines to cytotoxic anticancer drugs was not significantly altered by vardenafil. The differential effects of vardenafil and tadalafil appear to be specific for the ABCB1 transporter as both vardenafil and tadalafil had no significant effect on the reversal of drug resistance conferred by ABCC1 (MRP1) and ABCG2 (BCRP) transporters. Vardenafil significantly increased the intracellular accumulation of [(3)H]-paclitaxel in the ABCB1 overexpressing KB-C2 cells. In addition, vardenafil significantly stimulated the ATPase activity of ABCB1 and inhibited the photolabeling of ABCB1 with [(125)I]-IAAP. Furthermore, Western blot analysis indicated the incubation of cells with either vardenafil or tadalafil for 72 h did not alter ABCB1 protein expression. Overall, our results suggest that vardenafil reverses ABCB1-mediated MDR by directly blocking the drug efflux function of ABCB1.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors , Cyclic Nucleotide Phosphodiesterases, Type 5/metabolism , Imidazoles/pharmacology , Phosphodiesterase 5 Inhibitors/pharmacology , Piperazines/pharmacology , ATP Binding Cassette Transporter, Subfamily B , ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Adenosine Triphosphatases/antagonists & inhibitors , Adenosine Triphosphatases/chemistry , Adenosine Triphosphatases/metabolism , Carbolines/chemistry , Carbolines/metabolism , Carbolines/pharmacology , Drug Resistance, Neoplasm/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Humans , Imidazoles/chemistry , Imidazoles/metabolism , KB Cells , Models, Molecular , Phosphodiesterase 5 Inhibitors/chemistry , Phosphodiesterase 5 Inhibitors/metabolism , Piperazines/chemistry , Piperazines/metabolism , Protein Conformation , Sulfones/chemistry , Sulfones/metabolism , Sulfones/pharmacology , Tadalafil , Triazines/chemistry , Triazines/metabolism , Triazines/pharmacology , Vardenafil DihydrochlorideABSTRACT
In recent years, a number of TKIs (tyrosine kinase inhibitors) targeting epidermal growth factor receptor (EGFR) family have been synthesized and some have been approved for clinical treatment of cancer by the FDA. We recently reported a new pharmacological action of the 4-anilinoquinazoline derived EGFR TKIs, such as lapatinib (Tykerb) and erlotinib (Tarceva), which significantly affect the drug resistance patterns in cells expressing the multidrug resistance (MDR) phenotype. Previously, we showed that lapatinib and erlotinib could inhibit the drug efflux function of P-glycoprotein (P-gp, ABCB1) and ABCG2 transporters. In this study, we determined if these TKIs have the potential to reverse MDR due to the presence of the multidrug resistance protein 7 (MRP7, ABCC10). Our results showed that lapatinib and erlotinib dose-dependently enhanced the sensitivity of MRP7-transfected HEK293 cells to several established MRP7 substrates, specifically docetaxel, paclitaxel, vinblastine and vinorelbine, whereas there was no or a less effect on the control vector transfected HEK293 cells. [(3)H]-paclitaxel accumulation and efflux studies demonstrated that lapatinib and erlotinib increased the intracellular accumulation of [(3)H]-paclitaxel and inhibited the efflux of [(3)H]-paclitaxel from MRP7-transfected cells but not in the control cell line. Lapatinib is a more potent inhibitor of MRP7 than erlotinib. In addition, the Western blot analysis revealed that both lapatinib and erlotinib did not significantly affect MRP7 expression. We conclude that the EGFR TKIs, lapatinib and erlotinib reverse MRP7-mediated MDR through inhibition of the drug efflux function, suggesting that an EGFR TKI based combinational therapy may be applicable for chemotherapeutic practice clinically.
Subject(s)
Antineoplastic Agents/pharmacology , Drug Resistance, Multiple , Multidrug Resistance-Associated Proteins/antagonists & inhibitors , Quinazolines/pharmacology , Blotting, Western , Cell Line , Erlotinib Hydrochloride , Humans , LapatinibABSTRACT
La espondilolistesis es una de las causas identificables de dolor lumbar más frecuentes en la infancia, llegando a afectar al 6 por ciento de los niños mayores de 6 años. Cómo tratar esta patología ha sido motivo de controversia dado que no se pueden dar reglas generales. El tratamiento debe ser individualizado para cada paciente. Asimismo es importante recalcar el hecho de que aunque un paciente no necesite tratamiento, mientras tenga capacidad de crecer, podrá tener un avance en la deformidad, especialmente en las espondilolistesis displásicas, por lo que el seguimiento periódico de estos pacientes es obligatorio. Con este trabajo pretendemos mostrar nuestra experiencia en el tratamiento de esta patología presentando una serie de 139 pacientes con una media de edad en el diagnóstico de 11,8 años (9 meses-19años) controlados en nuestro centro con una evolución superior a los dos años (AU)