title: Involvement of phosphatidylinositol-3-kinase in membrane ruffling induced by P-glycoprotein substrates in multidrug-resistant carcinoma cells.
abstract: P-glycoprotein (P-gp) is a transmembrane protein that transports a variety of structurally and functionally diverse drugs. We recently found that the interaction of drugs with P-gp promoted invasion and metastasis. In this study, we sought to determine the mechanism by which the interaction of P-gp with its substrates leads to the earliest membrane changes associated with cellular invasion, i.e., membrane ruffling. We focused on the activation of phosphatidylinositol-3-kinase (PI-3-kinase), a lipid kinase that regulates actin cytoskeletal organization and cell movement. Sensitive or multidrug-resistant (MDR) MCF-7 (human breast cancer) or KB (human oral carcinoma) cells were treated with drugs or vehicle, and then were stained with phalloidin-tetramethyl-rhodamine isothiocyanate. Membrane ruffles were visualized using a fluorescence microscope. PI-3-kinase activity was determined by an in vitro immune-complex kinase assay and thin-layer chromatography. Drugs transported by P-gp, vinblastine and trans-flupenthixol, increased membrane ruffling and PI-3-kinase activity in the MDR cell lines, MCF-7/AdrR and KBV-1, which overexpress P-gp. This effect was not seen with mechlorethamine, a drug that is not transported by P-gp, and was not detected in sensitive parental cell lines that do not express P-gp. A similar effect was also observed in the MDR1 transfectant, MCF-7/BC-19. Wortmannin, an inhibitor of PI-3-kinase, blocked the effect of VBL and tFPT on membrane ruffling and the activity of PI-3-kinase in MDR cells. These results indicate that drugs transported by P-gp induce membrane ruffling, an early indicator of cellular motility and metastatic potential, in cancer cells overexpressing P-gp and that this effect may be mediated through activation of PI-3-kinase.
authors.affiliation: Department of Pharmacology and Medicine, The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ 08901, USA. jyang@umdnj.edu
authors.forename: Jin Ming
authors.initials: JM
authors.lastname: Yang
authors.forename: Andrew
authors.initials: A
authors.lastname: Vassil
authors.forename: William N
authors.initials: WN
authors.lastname: Hait
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001943:Breast Neoplasms; D018432:Drug Resistance, Multiple / Q000502:physiology*; D005260:Female; D006801:Humans; D008560:Membrane Fluidity / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D015398:Signal Transduction; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D014747:Vinblastine; D019869:Phosphatidylinositol 3-Kinases