Multidrug-resistant human sarcoma cells with a mutant P-glycoprotein, altered phenotype, and resistance to cyclosporins

J Biol Chem. 1997 Feb 28;272(9):5974-82. doi: 10.1074/jbc.272.9.5974.


A variant of the multidrug-resistant human sarcoma cell line Dx5 was derived by co-selection with doxorubicin and the cyclosporin D analogue PSC 833, a potent inhibitor of the multidrug transporter P-glycoprotein. The variant DxP cells manifest an altered phenotype compared with Dx5, with decreased cross-resistance to Vinca alkaloids and no resistance to dactinomycin. Resistance to doxorubicin and paclitaxel is retained. The multidrug resistance phenotype of DxP cells is not modulated by 2 microM PSC 833 or cyclosporine. DxP cells manifest a decreased ability to transport [3H]cyclosporine. DNA heteroduplex analysis and sequencing reveal a mutant mdr1 gene (deletion of a phenylalanine at amino acid residue 335) in the DxP cell line. The mutant P-glycoprotein has a decreased affinity for PSC 833 and vinblastine and a decreased ability to transport rhodamine 123. Transfection of the mutant mdr1 gene into drug-sensitive MES-SA sarcoma cells confers resistance to both doxorubicin and PSC 833. Our study demonstrates that survival of cells exposed to doxorubicin and PSC 833 in a multistep selection occurred as a result of a P-glycoprotein mutation in transmembrane region 6. These data suggest that Phe335 is an important binding site on P-glycoprotein for substrates such as dactinomycin and vinblastine and for inhibitors such as cyclosporine and PSC 833.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics*
  • Affinity Labels
  • Azides / metabolism
  • Blotting, Western
  • Cell Survival
  • Cyclosporins / therapeutic use*
  • DNA Topoisomerases, Type II / genetics
  • Dihydropyridines / metabolism
  • Doxorubicin / therapeutic use
  • Drug Resistance, Multiple*
  • Humans
  • Neoplasm Proteins / metabolism
  • Phenotype
  • Polymerase Chain Reaction
  • Prazosin / analogs & derivatives
  • Prazosin / metabolism
  • Rhodamine 123
  • Rhodamines / metabolism
  • Sarcoma / drug therapy
  • Sarcoma / genetics*
  • Sarcoma / metabolism
  • Vault Ribonucleoprotein Particles*
  • Verapamil / therapeutic use


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Affinity Labels
  • Azides
  • Cyclosporins
  • Dihydropyridines
  • Neoplasm Proteins
  • Rhodamines
  • Vault Ribonucleoprotein Particles
  • major vault protein
  • Rhodamine 123
  • azidopine
  • Doxorubicin
  • azidoprazosin
  • Verapamil
  • DNA Topoisomerases, Type II
  • Prazosin

Associated data

  • GENBANK/AF016534
  • GENBANK/AF016535