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

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

Li Y1, Bi H, Zhong G, Huang L, Li G, Xia Y, Chen X, Huang M.

Author information

1Laboratory of Drug Metabolism and Pharmacokinetics, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, PR China.

Abstract

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.

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