Involvement of phosphatidylinositol-3-kinase in membrane ruffling induced by P-glycoprotein substrates in multidrug-resistant carcinoma cells.
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.
Yang
Jin Ming
JM
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
Vassil
Andrew
A
Hait
William N
WN
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*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D014747:Vinblastine; D019869:Phosphatidylinositol 3-Kinases