Up-regulation of caveolae and caveolar constituents in multidrug-resistant cancer cells.
Cancer chemotherapy often results in the development of multidrug resistance (MDR), which is commonly associated with overexpression of P-glycoprotein (P-gp), a plasma membrane drug efflux ATPase. It was shown recently that glycosphingolipids are elevated in MDR cells. Sphingolipids are major constituents of caveolae and of detergent-insoluble, glycosphingolipid-rich membrane domains. Here we report that multidrug-resistant HT-29 human colon adenocarcinoma cells exhibit a 12-fold overexpression of caveolin-1, a 21-kDa coat/adaptor protein of caveolae. Similar observations were made in adriamycin-resistant MCF-7 human breast adenocarcinoma cells. Caveolin-2 expression is also up-regulated in MCF-7-AdrR cells, but neither caveolin-1 nor caveolin-2 were detected in MCF-7 cells stably transfected with P-gp. The up-regulation of caveolins is associated with a 5-fold increase in the number of caveolae-like structures observed in plasma membrane profiles of HT-29-MDR cells and with the appearance of a comparable number of caveolae in MCF-7-AdrR cells. A significant fraction (approximately 40%) of cellular P-gp is localized in low density detergent-insoluble membrane fractions derived from either HT-29-MDR or MCF-7-AdrR cells. The distribution of recombinant P-gp in stably transfected MCF-7 cells was similar, even though these cells do not express caveolins and are devoid of caveolae. The possibility that caveolae contribute to the multidrug resistance and thus are co-selected with P-gp during the acquisition of this phenotype is discussed.
Lavie
Y
Y
Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
Fiucci
G
G
Liscovitch
M
M
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins; D018432:Drug Resistance, Multiple / Q000235:genetics*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C495540:CAV1 protein, human; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins; D008565:Membrane Proteins