title: Induction of multidrug resistance downregulates the expression of CFTR in colon epithelial cells.
abstract: The epithelial cell line HT-29, which constitutively expresses the cystic fibrosis transmembrane conductance regulator (CFTR), was induced to become drug resistant by cultivation in the presence of colchicine. The gradual acquisition of drug resistance was associated with a corresponding increase in the expression of the multidrug resistance P-glycoprotein (P-gp) and a marked (> 80%) decrease in the constitutive levels of CFTR protein, as determined by immunoblotting. The reduction in CFTR content occurred at the onset of acquisition of drug resistance when P-gp expression was still relatively low. Reversal of drug resistance by removal of colchicine from the culture medium led to a 70% decrease in P-gp levels and a concomitant 40% increase in CFTR. The levels of other membrane proteins such as Na(+)-K(+)-ATPase and alkaline phosphatase remained relatively constant (< 26% variation). We propose that a selective downregulation of CFTR is elicited by acquisition of the multidrug resistance (MDR) phenotype and that induction of P-gp expression leads to a reversible repression of CFTR biosynthesis. These findings provide an experimental foundation for the complementary patterns of expression of the CFTR and MDR1 genes observed in vivo.
authors.affiliation: Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
authors.forename: W
authors.initials: W
authors.lastname: Breuer
authors.forename: I N
authors.initials: IN
authors.lastname: Slotki
authors.forename: D A
authors.initials: DA
authors.lastname: Ausiello
authors.forename: I Z
authors.initials: IZ
authors.lastname: Cabantchik
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000230:Adenocarcinoma; D000469:Alkaline Phosphatase / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis*; D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D003106:Colon; D003110:Colonic Neoplasms; D003550:Cystic Fibrosis; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004351:Drug Resistance / Q000502:physiology*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C505032:CFTR protein, human; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000469:Alkaline Phosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D003078:Colchicine