A Cysteine-Reactive Alkyl Hydroquinone Modifies Topoisomerase IIα, Enhances DNA Breakage, and Induces Apoptosis in Cancer Cells

• Published in: Chemical research in toxicology Vol. 25; no. 11; pp. 2340 - 2351
• Main Authors: Lin, Ting-Yu, Huang, Cheng-Po, Au, Lo-Chun, Chang, Ya-Wen, Hu, Chung-Yi, Lin, Shwu-Bin
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19.11.2012
• Subjects: Antigens, Neoplasm - metabolism; Antineoplastic Agents - chemistry; Antineoplastic Agents - isolation & purification; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Cell Survival - drug effects; Cysteine - chemistry; DNA Breaks - drug effects; DNA Breaks, Double-Stranded - drug effects; DNA Topoisomerases, Type II - metabolism; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - metabolism; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - isolation & purification; Enzyme Inhibitors - pharmacology; Flow Cytometry; Humans; Hydroquinones - chemistry; Hydroquinones - isolation & purification; Hydroquinones - pharmacology; Structure-Activity Relationship; Tumor Cells, Cultured
• ISSN: 0893-228X; 1520-5010; 1520-5010
• DOI: 10.1021/tx3002302

We previously reported that the anticancer activity of a botanical compound 10′(Z),13′(E),15′(E)-heptadecatrienylhydroquinone [HQ17(3)] was attributed to topoisomerase (Topo) IIα poisoning and the induction of oxidative damage. HQ17(3) irreversibly inhibits Topo IIα activity in vitro and is more cytotoxic in leukemia HL-60 cells than in Topo IIα-deficient variant HL-60/MX2 cells, which suggests that Topo IIα is a cellular target of HQ17(3). This study further characterizes the molecular mechanisms of the anticancer activity of HQ17(3). Proteomic analyses indicated that HQ17(3) reacted with Cys-427, Cys-733, and Cys-997 of recombinant Topo IIα in vitro, whereas it reacted with Cys-427 of cellular Topo IIα in Huh7 hepatoma cells. The modification of HQ17(3) inhibited Topo IIα catalytic activity, increased the Topo IIα-DNA cleavage complex, and caused the accumulation of DNA breakage. In Huh7 cells, HQ17(3) treatment caused prompt inhibition of DNA synthesis and consequently induced the expression of DNA damage-related genes DDIT3, GADD45A, and GADD45G. Topo IIα inhibition, apoptosis, and oxidative stress were found to account for cytotoxicity caused by HQ17(3). Pretreatment of Huh7 cells with N-acetylcysteine (NAC) partially attenuated mitochondrial membrane damage, DNA breakage, and caspase activation. However, NAC pretreatment did not diminish HQ17(3)-induced cell death. These results suggest that the anticancer activity of HQ17(3) is attributed significantly to Topo IIα poisoning. The structural feature of HQ17(3) can be used as a model for the design of Topo IIα inhibitors and anticancer drugs.