title: P-glycoprotein-dependent resistance of cancer cells toward the extrinsic TRAIL apoptosis signaling pathway.
abstract: The TNF-related apoptosis-inducing ligand (TRAIL or Apo2L) preferentially cause apoptosis of malignant cells in vitro and in vivo without severe toxicity. Therefore, TRAIL or agonist antibodies to the TRAIL DR4 and DR5 receptors are used in cancer therapy. However, many malignant cells are intrinsically resistant or acquire resistance to TRAIL. It has been previously proposed that the multidrug transporter P-glycoprotein (Pgp) might play a role in resistance of cells to intrinsic apoptotic pathways by interfering with components of ceramide metabolism or by modulating the electrochemical gradient across the plasma membrane. In this study we investigated whether Pgp also confers resistance toward extrinsic death ligands of the TNF family. To this end we focused our study on HeLa cells carrying a tetracycline-repressible plasmid system which shuts down Pgp expression in the presence of tetracycline. Our findings demonstrate that expression of Pgp is a significant factor conferring resistance to TRAIL administration, but not to other death ligands such as TNF-α and Fas ligand. Moreover, blocking Pgp transport activity sensitizes the malignant cells toward TRAIL. Therefore, Pgp transport function is required to confer resistance to TRAIL. Although the resistance to TRAIL-induced apoptosis is Pgp specific, TRAIL itself is not a direct substrate of Pgp. Pgp expression has no effect on the level of the TRAIL receptors DR4 and DR5. These findings might have clinical implications since the combination of TRAIL therapy with administration of Pgp modulators might sensitize TRAIL resistant tumors.
authors.affiliation: Laboratory of Molecular Immunology, Division of Hematology, Chaim Sheba Medical Center, Tel Hashomer, Israel. hgalski@sheba.health.gov.il
authors.forename: Hanan
authors.initials: H
authors.lastname: Galski
authors.forename: Tamar
authors.initials: T
authors.lastname: Oved-Gelber
authors.forename: Masha
authors.initials: M
authors.lastname: Simanovsky
authors.forename: Philip
authors.initials: P
authors.lastname: Lazarovici
authors.forename: Michael M
authors.initials: MM
authors.lastname: Gottesman
authors.forename: Arnon
authors.initials: A
authors.lastname: Nagler
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm; D053222:Fas Ligand Protein / Q000378:metabolism; D006801:Humans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017931:DNA Primers; D053222:Fas Ligand Protein; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha
keywords: ABC; APC; ATP-binding cassette; Allophycocyanin; Apoptosis; BSA; CHX; CsA; D-PBS; DMEM; DMSO; Dulbecco's modified Eagle's medium; Dulbecco's phosphate buffered saline; FBS; FITC; Fas ligand; FasL; HRP; MDR; Modulators; P-glycoprotein; PCR; PE; PI; Pgp; R-VRP; R-verapamil; Resistance; Rh123; Rhodamine 123; TMB; TMD; TNF; TNF-related apoptosis-inducing ligand; TRAIL; bovine serum albumin; cycloheximide; cyclosporine A; dimethyl sulfoxide; fluorescein isothiocyanate; foetal bovine serum; horse radish peroxidase; multidrug resistance; phycoerythrin; polymerase chain reaction; propidium iodide; tetramethylbenzidine; transmembrane domains; tumor necrosis factor.