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Characterization of HU‐331 as a cannabinoid quinone inhibitor of topoisomerase II (549.6)
Author(s) -
Regal Kellie,
Mercer Susan,
Deweese Joseph
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.549.6
Subject(s) - topoisomerase , dna , biochemistry , topoisomerase inhibitor , mechanism of action , dna damage , enzyme , biology , chemistry , atpase , cleavage (geology) , microbiology and biotechnology , in vitro , paleontology , fracture (geology)
Topoisomerases are essential enzymes that are involved in DNA metabolism. Due to the double‐stranded DNA cleavage mechanism, topoisomerase II is an effective target for anticancer drugs, such as doxorubicin. However, doxorubicin causes cardiac toxicity and can induce DNA damage resulting in secondary cancers. A cannabinoid‐based quinone HU‐331 has been identified as a potential anticancer drug that demonstrates more potency in cancer cells with less off‐target toxicity than doxorubicin. Reports indicate that HU‐331 does not promote cell death via apoptosis, cell cycle arrest, caspase activation, or DNA strand breaks. However, the precise mechanism of action is poorly understood. We proposed that HU‐331 inhibits human topoisomerase IIα function by inhibiting the ATPase domain of the enzyme. We employed biochemical assays to study the mechanism of action of HU‐331 against purified topoisomerase IIα. These assays examined DNA cleavage, ligation, relaxation, and ATPase function of topoisomerase IIα. Our results demonstrate that HU‐331 inhibits topoisomerase IIα‐mediated DNA relaxation at micromolar levels. We find that HU‐331 does not induce DNA strand breaks, decreasing the risk of secondary cancers. When added prior to the DNA substrate, HU‐331 blocks DNA cleavage and relaxation activities of topoisomerase IIα. Our results also show that HU‐331 inhibits the ATPase function of topoisomerase IIα. Preliminary binding studies also indicate that HU‐331 decreases the ability of topoisomerase IIα to bind DNA. We have thus far concluded that HU‐331 impacts the catalytic activity of topoisomerase IIα by inhibiting the ATPase function. These results provide a promising foundation for the potential of HU‐331 as an anticancer drug. Future studies will explore the ability of HU‐331 to abrogate cleavage and relaxation activities. We will also further clarify the impact of HU‐331 on the enzyme:DNA interaction.