Effect of phorbol 12-myristate 13-acetate on function and gene expression of P-glycoprotein in adriamycin-resistant K562/ADM cells

Pharmacology. 2013;92(3-4):121-30. doi: 10.1159/000353774. Epub 2013 Aug 31.


Background/aims: Multidrug resistance (MDR) is a critical issue during chemotherapy of cancers. Phorbol 12-myristate 13-acetate (PMA), a diester of phorbol, is a typical activator of protein kinase C (PKC). In the present study, we investigated the effect of PMA on MDR and P-glycoprotein (P-gp) gene expression in K562/ADM cells.

Methods: 3-(4,5-dimethylthiazol-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay was used to assess adriamycin (Adr)-induced cytotoxicity towards K562/ADM cells in the absence or presence of PMA. The intracellular accumulation of Adr was measured by determining the mean fluorescence intensity. The effect of PMA on P-gp activity was investigated by rhodamine-123 accumulation and efflux experiment. Protein expression and mRNA expression of P-gp in K562/ADM cells were determined by Western blot analysis and real-time qPCR, respectively.

Results: Adr-induced cytotoxicity towards K562/ADM cells was significantly decreased by PMA at 5 μmol/l. Furthermore, intracellular Adr-associated mean fluorescence intensity was attenuated by 53.8% 1 h after exposure to PMA at 5 μmol/l compared with the control group (p < 0.05). A dose-dependent decrease of intracellular rhodamine-123 and increase of efflux activity of P-gp were also observed in K562/ADM cells incubation with PMA. In addition, P-gp mRNA and protein expression were significantly induced by PMA.

Conclusion: Activation of PKC pathway by PMA can significantly induce expression and activity of P-gp, and thus decrease intracellular Adr level and strengthen MDR in K562/ADM cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Cell Survival / drug effects
  • Doxorubicin / pharmacology*
  • Drug Resistance, Neoplasm*
  • Gene Expression Regulation / drug effects*
  • Humans
  • K562 Cells
  • Protein Kinase C / metabolism*
  • RNA, Messenger / metabolism
  • Tetradecanoylphorbol Acetate / pharmacology*


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • RNA, Messenger
  • Doxorubicin
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate