Paclitaxel-resistance conferred by altered expression of efflux and influx transporters for paclitaxel in the human hepatoma cell line, HepG2

Drug Metab Pharmacokinet. 2009;24(5):418-27. doi: 10.2133/dmpk.24.418.


Paclitaxel-resistant HepG2 (PR-HepG2) cells were established by long-term exposure of HepG2 cells to paclitaxel and expression and function of efflux (P-glycoprotein, MRP2) and influx (OATP1B3) transporters for paclitaxel were examined to understand the mechanisms underlying the resistance. mRNA expression of P-glycoprotein (P-gp) increased in PR-HepG2 more than in HepG2 cells, while that of MRP2 did not change. Interestingly, mRNA expression of OATP1B3 drastically decreased in PR-HepG2 cells. [(3)H]Paclitaxel uptake was less in PR-HepG2 than in HepG2 cells and the uptake in both cells increased by metabolic inhibition. The uptake of [(3)H]paclitaxel and rhodamine 123 increased by verapamil, a P-gp inhibitor. Probenecid, an MRP inhibitor, did not affect [(3)H]paclitaxel uptake in both cells. Sulfobromophthalein, an OATP1B3 inhibitor, inhibited [(3)H]paclitaxel uptake in HepG2 but not in PR-HepG2 cells. Cytotoxicity studies showed that the resistance of PR-HepG2 cells to paclitaxel was reversed by verapamil. PR-HepG2 cells showed cross-resistance to doxorubicin, a P-gp substrate, but not to cisplatin. These results indicate that enhanced expression and function of P-gp may be a predominant mechanism of paclitaxel resistance in PR-HepG2 cells and the reduced influx via OATP1B3 may also serve to lower intracellular paclitaxel concentration in cooperation with P-gp-mediated efflux.

MeSH terms

  • Doxorubicin / pharmacology
  • Drug Resistance, Neoplasm / drug effects*
  • Hep G2 Cells
  • Humans
  • Liver / drug effects
  • Liver / metabolism
  • Multidrug Resistance-Associated Proteins / biosynthesis
  • Organic Anion Transporters, Sodium-Independent / physiology
  • Paclitaxel / metabolism
  • Paclitaxel / pharmacology*
  • Probenecid / pharmacology
  • RNA, Messenger / metabolism
  • Rhodamine 123 / metabolism
  • Sodium Azide / pharmacology
  • Solute Carrier Organic Anion Transporter Family Member 1B3
  • Sulfobromophthalein / pharmacology
  • Verapamil / pharmacology


  • Multidrug Resistance-Associated Proteins
  • Organic Anion Transporters, Sodium-Independent
  • RNA, Messenger
  • SLCO1B3 protein, human
  • Solute Carrier Organic Anion Transporter Family Member 1B3
  • Sulfobromophthalein
  • Rhodamine 123
  • multidrug resistance-associated protein 2
  • Doxorubicin
  • Sodium Azide
  • Verapamil
  • Paclitaxel
  • Probenecid