Biochemical mechanism of modulation of human p-glycoprotein by stemofoline

Wisinee Chanmahasathien, Shinobu Ohnuma, Suresh V. Ambudkar, Pornngarm Limtrakul

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30 Citations (Scopus)


The resistance to chemotherapeutic drugs by cancer cells is considered to be one of the major obstacles for success in the treatment of cancer. A major mechanism underlying this multidrug resistance is the overexpression of P-glycoprotein (P-gp), resulting in insufficient drug delivery to the tumor sites. A previous study has shown that stemofoline, an alkaloid isolated from Stemona burkillii, could enhance the sensitivity of chemotherapeutics in a synergistic fashion. In the present study, we have focused on the effect of stemofoline on the modulation of P-gp function in a multidrug resistant human cervical carcinoma cell line (KB-V1). The effects of stemofoline on a radiolabeled drug, [ 3H]-vinblastine, and fluorescent P-gp substrates, rhodamine 123 and calcein-AM accumulation or retention were investigated to confirm this finding. Stemofoline could increase the accumulation or retention of radiolabeled drugs or fluorescent P-gp substrates in a dose-dependent manner. For additional studies on drug-P-gp binding, P-gp ATPase activity was stimulated by stemofoline in a concentration-dependent manner. More evidence was offered that stemofoline inhibits the effect on photoaffinity labeling of P-gp with [ 125I]-iodoarylazidoprazosin in a concentration-dependent manner. These data indicate that stemofoline may interact directly with P-gp and inhibit P-gp activity, whereas stemofoline has no effect on P-gp expression. Taken together, the results exhibit that stemofoline possesses an effective MDR modulator, and may be used in combination with conventional chemotherapeutic drugs to reverse MDR in cancer cells.

Original languageEnglish
Pages (from-to)1990-1995
Number of pages6
JournalPlanta Medica
Issue number18
Publication statusPublished - 2011


  • KB-V1
  • multidrug resistance
  • P-glycoprotein
  • stemofoline
  • Stemona burkillii
  • Stemonaceae


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