title: Cross-talk between signalling pathways and the multidrug resistant protein MDR-1.
abstract: The multidrug resistant protein MDR-1 has been associated with the resistance to a wide range of anti-cancer drugs. Taxol is a substrate for this transporter system and is used in the treatment of a wide range of human malignancies including lung, breast and ovarian cancer. We have generated a series of ovarian cell lines resistant to this compound, all of which overexpress MDR-1 through gene amplification. We present novel evidence that a constitutive activation of the ERK1/2 MAP kinase pathway was also observed although the level of active JNK and p38 remained unchanged. Inhibition of the ERK1/2 MAP kinase pathway using UO126 or PD098059 re-sensitised the Taxol resistant cells at least 20-fold. Importantly, when Mdr-1 cDNA was stably expressed in the wild-type cell line to generate a highly Taxol-resistant sub-line, 1847/MDR5, ERK1/2 MAP kinases again became activated. This result demonstrated that the increased activity of the signalling pathway in the Taxol-resistant lines was directly attributable to MDR-1 overexpression and was not due to the effects of Taxol itself. Additionally, we demonstrated that inhibition of the P13K pathway with LY294002 sensitised the MDR-1-expressing 1847/TX0.5 cells and 1847/MDR5 cells at least 10-fold but had no effect in the wild-type cells. This finding suggests a possible role for this pathway, also, in the generation of resistance to Taxol.
authors.affiliation: Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK.
authors.forename: S
authors.initials: S
authors.lastname: Ding
authors.forename: M
authors.initials: M
authors.lastname: Chamberlain
authors.forename: A
authors.initials: A
authors.lastname: McLaren
authors.forename: L
authors.initials: L
authors.lastname: Goh
authors.forename: I
authors.initials: I
authors.lastname: Duncan
authors.forename: C R
authors.initials: CR
authors.lastname: Wolf
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D010051:Ovarian Neoplasms / Q000188:drug therapy*; D017239:Paclitaxel / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005419:Flavonoids; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D017239:Paclitaxel; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one