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Mol Pharm. 2016 Jun 6;13(6):2010-25. doi: 10.1021/acs.molpharmaceut.6b00140. Epub 2016 Apr 28.

Chemical Reactivity Window Determines Prodrug Efficiency toward Glutathione Transferase Overexpressing Cancer Cells.

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Institute of Environmental Medicine, Division of Biochemical Toxicology, Karolinska Institutet , SE 17177 Stockholm, Sweden.
Department of Radiation Oncology (MaastRO Lab), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center , Universiteitssingel 50/23, PO Box 616, 6200 MD Maastricht, The Netherlands.
Departments of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina , Charleston, South Carolina 29425, United States.
Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina , Charleston, South Carolina 29425, United States.
Department of Toxicology, NUTRIM-School for Nutrition, Toxicology, and Metabolism, Maastricht University Medical Center , Universiteitssingel 50/23, PO Box 616, 6200 MD Maastricht, The Netherlands.
Nano Medical Engineering Laboratory, Discovery Research Institute, RIKEN 2-1 , Hirosawa, Wako-Shi, Saitama 351-0198, Japan.
Department of Chemistry, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet , SE-171 77 Stockholm, Sweden.


Glutathione transferases (GSTs) are often overexpressed in tumors and frequently correlated to bad prognosis and resistance against a number of different anticancer drugs. To selectively target these cells and to overcome this resistance we previously have developed prodrugs that are derivatives of existing anticancer drugs (e.g., doxorubicin) incorporating a sulfonamide moiety. When cleaved by GSTs, the prodrug releases the cytostatic moiety predominantly in GST overexpressing cells, thus sparing normal cells with moderate enzyme levels. By modifying the sulfonamide it is possible to control the rate of drug release and specifically target different GSTs. Here we show that the newly synthesized compounds, 4-acetyl-2-nitro-benzenesulfonyl etoposide (ANS-etoposide) and 4-acetyl-2-nitro-benzenesulfonyl doxorubicin (ANS-DOX), function as prodrugs for GSTA1 and MGST1 overexpressing cell lines. ANS-DOX, in particular, showed a desirable cytotoxic profile by inducing toxicity and DNA damage in a GST-dependent manner compared to control cells. Its moderate conversion of 500 nmol/min/mg, as catalyzed by GSTA1, seems hereby essential since the more reactive 2,4-dinitrobenzenesulfonyl doxorubicin (DNS-DOX) (14000 nmol/min/mg) did not display a preference for GSTA1 overexpressing cells. DNS-DOX, however, effectively killed GSTP1 (20 nmol/min/mg) and MGST1 (450 nmol/min/mg) overexpressing cells as did the less reactive 4-mononitrobenzenesulfonyl doxorubicin (MNS-DOX) in a MGST1-dependent manner (1.5 nmol/min/mg) as shown previously. Furthermore, we show that the mechanism of these prodrugs involves a reduction in GSH levels as well as inhibition of the redox regulatory enzyme thioredoxin reductase 1 (TrxR1) by virtue of their electrophilic sulfonamide moiety. TrxR1 is upregulated in many tumors and associated with resistance to chemotherapy and poor patient prognosis. Additionally, the prodrugs potentially acted as a general shuttle system for DOX, by overcoming resistance mechanisms in cells. Here we propose that GST-dependent prodrugs require a conversion rate "window" in order to selectively target GST overexpressing cells, while limiting their effects on normal cells. Prodrugs are furthermore a suitable system to specifically target GSTs and to overcome various drug resistance mechanisms that apply to the parental drug.


GSTA1; MGST1; TrxR1; doxorubicin; etoposide; glutathione transferases; prodrugs; redox

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