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A Cysteine-Reactive Alkyl Hydroquinone Modifies Topoisomerase IIα, Enhances DNA Breakage, and Induces Apoptosis in Cancer Cells
journal contribution
posted on 2016-02-20, 05:57 authored by Ting-Yu Lin, Cheng-Po Huang, Lo-Chun Au, Ya-Wen Chang, Chung-Yi Hu, Shwu-Bin LinWe 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.