Abstract
The histone deacetylase inhibitor depsipeptide [(1S,4S,7Z,10S, 16E,21R)-7-ethylidene-4,21-bis(propan-2-yl)-2-oxa-12,13-dithia-5,8,20,23-tetraazabicyclo[8.7.6]tricos-16-ene-3,6,9,19, 22-pentone] (FK228) has attracted a great deal of interest because of its antiproliferative and apoptotic properties in various malignancies. Histone deacetylase inhibitors induce the expression of the multidrug resistance transporter P-glycoprotein (P-gp), and FK228 is a known P-gp substrate. Thus, FK228 seems to induce its own mechanism of drug resistance by up-regulating P-gp. The goal of this study was to establish human FK228-resistant osteosarcoma cell lines and to investigate whether there are mechanisms of FK228 resistance in addition to P-gp up-regulation. After 72 h in culture, the 50% inhibitory concentrations (IC50) of FK228 were 4.8 and 991 nM in HOS and HOS/FK8 cells, respectively, and 3.6 and 1420 nM in U2OS and U2OS/FK11 cells, respectively. Increased histone H3 acetylation was observed in FK228-resistant cell lines after a 1-h treatment with 10 nM FK228. Unlike in parental cells, significant P-gp overexpression was detected in FK228-resistant cells, and 10 nM FK228 treatment activated the mitogen-activated protein kinase (MAPK) pathway but did not induce Fas ligand (FasL) up-regulation or c-FLIP down-regulation. However, treatment of FK228-resistant cells with a combination of FK228 and mitogen-activated protein kinase kinase (MEK) inhibitors induced apoptosis, up-regulated FasL, and down-regulated c-FLIP. The expression and function of P-gp were unaltered by treatment with MEK inhibitors. These results indicate that the FK228 resistance of osteosarcoma cells is related to P-gp overexpression and MAPK pathway activation by FK228. MEK or P-gp inhibitors may be useful in overcoming this resistance.
Footnotes
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This work was supported by the Ministry of Education, Science, Technology, Sports, and Culture of Japan [Grants-in-Aid for Young Scientists (B) (18790714), Creative Scientific Research (13GS0009), Science Research on Priority Areas (17014052), and Scientific Research (C) (17591083)].
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doi:10.1124/jpet.108.147462.
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ABBREVIATIONS: HDACi, histone deacetylase inhibitor; FasL, Fas ligand; mAb, monoclonal antibody; c-FLIP, cellular FLICE-inhibitory protein; P-gp, P-glycoprotein; MAPK, mitogen-activated protein kinase; ERK, extracellular signal-regulated kinase; MEK, mitogen-activated protein kinase kinase; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; PD98059, 2′-amino-3′-methoxyflavone; U0126, 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophynyltio)butadiene; PBS, phosphate-buffered saline; PI, propidium iodide; BSA, bovine serum albumin; TBST, Tris-buffered saline/Tween 20; siRNA, small interference RNA; RT, reverse transcriptase; PCR, polymerase chain reaction; wt, wild type; ROS, reactive oxidative species; FK228, romidepsin, depsipeptide, or FR901228, (1S,4S,7Z,10S,16E,21R)-7-ethylidene-4,21-bis(propan-2-yl)-2-oxa-12,13-dithia-5,8,20,23-tetraazabicyclo[8.7.6]tricos-16-ene-3,6,9,19,22-pentone.
- Received October 15, 2008.
- Accepted December 9, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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