Mechanistic study of potentiation of chemotherapy by a haloenol lactone derivative in vitro.
OBJECTIVE
The objective of this study was to understand the biochemical mechanisms by which a haloenol lactone (HEL) derivative potentiates cisplatin-induced cytotoxicity in vitro. HEL was originally designed and synthesized as a site-directed inactivator of glutathione S-transferase pi isozyme (GST-pi). Over-expression of GST-pi has been found to be associated with chemotherapy resistance.


METHODS
A concentration-dependent GST inhibition was assessed after UOK130 cells were exposed to HEL at concentrations of 10 and 20 muM. Potentiated cytotoxicity was evaluated by treatment of UOK130 cells with a selection of alkylating agents in the presence or absence of HEL. Intracellular glutathione (GSH) was determined after exposure to HEL. Protective effect of GSH was examined by co-treatment with GSH ester in UOK130 cells exposed with a combination of cisplatin and HEL. Multiple resistance-associated protein (MRP) 1-3 activity was assayed by determining the rate of (3)H-LTC(4) and (3)H-E(2)17betaG through the MRPs into recombinant membrane vesicles.


RESULTS
Exposure of HEL at 10 and 20 muM caused 28 and 41% of inhibition of cellular GST activity. Cytotoxicity of cisplatin, chlorambucil, and melphalan was enhanced 1.8-2.7-fold by HEL at 10 muM. No significant protection effect by GSH ester exposure was observed on cisplatin toxicity co-treated with HEL. HEL was found to inhibit MRP1, MRP2, and MRP3 with IC(50) of 1.30, 28.2, and 3.66 muM, respectively.


CONCLUSIONS
Haloenol lactone showed inhibitory effect on GST-pi and MRP1-3 (selective inhibition of MRP1 and MRP3), and it was also found to deplete intracellular GSH.
Wang
Wei
W
Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA.
Xia
Cindy Q
CQ
Liu
Ning
N
Gan
Liang-Shang
LS
Zheng
Jiang
J
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004958:Estradiol / Q000096:biosynthesis; D005978:Glutathione / Q000378:metabolism; D051549:Glutathione S-Transferase pi / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D006801:Humans; D017997:Leukotriene C4 / Q000096:biosynthesis; D008566:Membranes / Q000187:drug effects; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis / Q000235:genetics
D015107:4-Butyrolactone; D000970:Antineoplastic Agents; D018906:Antineoplastic Agents, Alkylating; D002945:Cisplatin; D004958:Estradiol; D005978:Glutathione; D051549:Glutathione S-Transferase pi; D017997:Leukotriene C4; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C101132:3-cinnamyl-5-bromomethylidenetetrahydro-2-furanone; C000715087:ABCC2 protein, human; C114462:multidrug resistance-associated protein 3; C421109:multidrug resistance-associated protein 1