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Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Selective Antitumor Activity and Photocytotoxicity of Glutathione-Activated Abasic Site Trapping Agents
Li Xue1, Dehao Yu1, Lingling Wang2
1Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, Department of Chemical Biology, School of Pharmacy, Tianjin Medical University, Tianjin 300070, P. R. China.
Abstract:
Abasic (AP) sites are one of the most common DNA lesions in cells. Aldehyde-reactive alkoxyamines capture AP sites and block the activity of APE1, the enzyme responsible for initiating their repair. Blocking the APE1 repair of AP sites leads to cell death, and it is an actively investigated approach for treating cancer. However, unselective AP site capture in different cells produces side effects and limits the application of alkoxyamines in chemotherapy. Herein we take advantage of the higher glutathione (GSH) concentration in cancer cells over normal cells to develop GSH-inducible agents that selectively kill cancer cells. 2,4-Dinitrobenzenesulfonamide caged coumarin-based alkoxyamines 1 and 2 are selectively revealed by GSH to release SO2 and fluorescent coumarin-based alkoxyamines 3 and 4 that trap AP sites in cells. GSH-directed AP site trapping and SO2 release result in selective cytotoxicity (defined as IC50WI38/IC50H1299) against H1299 lung cancer cells over normal WI38 lung cells, ranging from 1.8 to 2.8 for 1 and 2. The alkylating agent methylmethanesulfonate (MMS) promotes the formation of AP sites in cells and enhances the cytotoxicity of agent 1 in a dose-dependent way. Moreover, the comet assay and γH2AX assay suggest that AP adducts form a highly toxic DNA interstrand cross-link (ICL) upon photolysis, leading to further cell death. DNA flow cytometric analysis showed that 1 promoted cell apoptosis in the early stage and induced G2/M phase cell-cycle arrest. The 2,4-dinitrobenzenesulfonamide-caged alkoxyamines exhibited selective antitumor activity and photocytotoxicity in cancer cells, illuminating their potential as GSH-directed chemotherapeutic agents.
Insights
Researchers developed new glutathione-inducible agents that selectively target cancer cells by trapping abasic (AP) sites. These agents show promise for cancer treatment by enhancing cytotoxicity and inducing apoptosis in cancer cells while sparing normal cells.
Area of Science:
- Biochemistry
- Molecular Biology
- Medicinal Chemistry
Background:
- Abasic (AP) sites are common DNA lesions crucial for DNA repair.
- Alkoxyamines targeting AP sites and APE1 enzyme show anti-cancer potential but lack selectivity.
- Cancer cells exhibit higher glutathione (GSH) levels than normal cells, offering a target for selective drug delivery.
Purpose of the Study:
- To develop novel GSH-inducible alkoxyamine agents for selective cancer cell killing.
- To investigate the mechanism of action and efficacy of these agents in vitro.
- To evaluate their potential as targeted chemotherapeutic agents.
Main Methods:
- Synthesis of 2,4-dinitrobenzenesulfonamide caged coumarin-based alkoxyamines (1 and 2).
- Assessment of GSH-inducible release of active alkoxyamines (3 and 4) and SO2.
- Evaluation of selective cytotoxicity against H1299 lung cancer cells versus WI38 normal lung cells.
- Analysis of DNA damage (comet assay, γH2AX assay) and cell cycle progression (flow cytometry).
Main Results:
- GSH-inducible agents selectively released active alkoxyamines, trapping AP sites and releasing SO2.
- Compounds 1 and 2 demonstrated selective cytotoxicity against H1299 cancer cells (IC50WI38/IC50H1299 ratios of 1.8-2.8).
- Methylmethanesulfonate enhanced agent 1's cytotoxicity, indicating AP site formation is key.
- AP adducts formed photolytic DNA interstrand cross-links (ICLs), enhancing cell death.
- Agent 1 induced apoptosis and G2/M cell-cycle arrest in cancer cells.
Conclusions:
- 2,4-Dinitrobenzenesulfonamide-caged alkoxyamines are effective GSH-directed chemotherapeutic agents.
- These agents exhibit selective antitumor activity and photocytotoxicity in cancer cells.
- The findings highlight the potential of these compounds for targeted cancer therapy.
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