Glucuronidation as a mechanism of intrinsic drug resistance in colon cancer cells: contribution of drug transport proteins

Biochem Pharmacol. 2004 Jan 1;67(1):31-9. doi: 10.1016/j.bcp.2003.07.019.


We have recently shown that drug conjugation catalysed by UDP-glucuronosyltransferases (UGTs) functions as an intrinsic mechanism of resistance to the topoisomerase I inhibitors 7-ethyl-10-hydroxycamptothecin and NU/ICRF 505 in human colon cancer cells and now report on the role of drug transport in this mechanism. The ability of transport proteins to recognise NU/ICRF 505 as a substrate was evaluated in model systems either transfected with breast cancer-resistance protein 1 (Bcrp1), multidrug-resistance protein 2 (Mrp2) or Mrp3, or overexpressing MRP1 or P-170 glycoprotein. Results from chemosensitivity assays suggested that NU/ICRF 505 was not a substrate for any of the above proteins. In drug accumulation studies in human colon cancer cell lines NU/ICRF 505 was taken up avidly and retained in cells lacking UGTs (HCT116), whereas, following equally rapid uptake, it was cleared rapidly from cells displaying UGT activity (HT29) as glucuronide metabolites. HT29 cells were shown to express MRP1 and 3, but not P-170 glycoprotein, MRP2 or breast cancer-resistance protein. The major glucuronide of NU/ICRF 505 inhibited ATP-dependent transport of estradiol 17-beta-glucuronide in Sf9 insect cell membrane vesicles containing MRP1 or MRP3, while co-incubation of HT29 cells with the MRP antagonist, MK571, significantly restored intracellular concentrations of NU/ICRF 505. These data lead us to conclude that the presence of a glucuronide transporter is essential for glucuronidation to represent a major de novo resistance mechanism and that UGTs will contribute more as a primary resistance mechanism when the parent drug (e.g. NU/ICRF 505) is not itself recognised by transport proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthraquinones / pharmacology*
  • Antigens, CD / metabolism
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Biological Transport
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology
  • Carrier Proteins
  • Colonic Neoplasms
  • Drug Interactions
  • Drug Resistance
  • Glucuronides / metabolism*
  • HT29 Cells
  • Humans
  • Irinotecan
  • Membrane Glycoproteins / metabolism
  • Membrane Transport Proteins*
  • Multidrug Resistance-Associated Protein 2
  • Multidrug Resistance-Associated Proteins / antagonists & inhibitors
  • Multidrug Resistance-Associated Proteins / metabolism*
  • Propionates / pharmacology
  • Quinolines / pharmacology
  • Tetraspanin 29
  • Tumor Cells, Cultured
  • Tyrosine / analogs & derivatives*
  • Tyrosine / pharmacology*


  • ABCC2 protein, human
  • Anthraquinones
  • Antigens, CD
  • Antineoplastic Agents, Phytogenic
  • CD9 protein, human
  • Carrier Proteins
  • Glucuronides
  • Membrane Glycoproteins
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Protein 2
  • Multidrug Resistance-Associated Proteins
  • NU-ICRF 505
  • Propionates
  • Quinolines
  • Tetraspanin 29
  • multidrug resistance-associated protein 3
  • Tyrosine
  • verlukast
  • Irinotecan
  • Camptothecin