Bioflavonoids as Poisons of Human Topoisomerase IIα and IIβ

Abstract

Bioflavonoids are human dietary components that have been linked to the prevention of cancer in adults and the generation of specific types of leukemia in infants. While these compounds have a broad range of cellular activities, many of their genotoxic effects have been attributed to their actions as topoisomerase II poisons. However, the activities of bioflavonoids against the individual isoforms of human topoisomerase II have not been analyzed. Therefore, we characterized the activity and mechanism of action of three major classes of bioflavonoids, flavones, flavonols, and isoflavones, against human topoisomerase IIR and II . Genistein was the most active bioflavonoid tested and stimulated enzymemediated DNA cleavage ∼10-fold. Generally, compounds were more active against topoisomerase II . DNA cleavage with both enzyme isoforms required a 5-OH and a 4′-OH and was enhanced by the presence of additional hydroxyl groups on the pendant ring. Competition DNA cleavage and topoisomerase II binding studies indicate that the 5-OH group plays an important role in mediating genistein binding, while the 4′-OH moiety contributes primarily to bioflavonoid function. Bioflavonoids do not require redox cycling for activity and function primarily by inhibiting enzyme-mediated DNA ligation. Mutagenesis studies suggest that the TOPRIM region of topoisomerase II plays a role in genistein binding. Finally, flavones, flavonols, and isoflavones with activity against purified topoisomerase IIR and II enhanced DNA cleavage by both isoforms in human CEM leukemia cells. These data support the hypothesis that bioflavonoids function as topoisomerase II poisons in humans and provide a framework for further analysis of these important dietary components.

Resveratrol acts as a topoisomerase II poison in human glioma cells

“…30 In this context, the genotoxic activity of some human dietary components such as bioflavonoid has been attributed to their action as topoisomerase poisons. 5 In this study, we demonstrate through docking simulations that RSV polar groups allow this molecule to establish non-covalent cross-linking interactions with both TOPOII and DNA at the binding interface between these two macromolecules. This result is particularly interesting in that it is suggestive of a stabilizing effect of RSV on the TOPOII/DNA complex which, in turn, could cause a delay in DNA religation.…”

“…3 It has been suggested that some of the cellular effects of polyphenols, such as anti-proliferative and proapoptotic actions, could be correlated with their ability to act on topoisomerases. 4,5 These are ubiquitous nuclear enzymes that modulate the topological state of DNA by breaking and resealing one or both strands of a DNA duplex. In eukaryotic cells, type II topoisomerases, isoforms a and b, function during major cellular processes involving DNA (recombination, replication, proper chromosome structure and segregation) generating intermediate cleavable or covalent complexes with a short half-life.…”

“…Since other polyphenols, namely bioflavonoid as genistein, have been shown to enhance DNA cleavage mediated by human TOPOII 5,13 we tested the hypothesis that RSV could act as a TOPO poison. We first focused our attention on the interference of RSV molecule between DNA and topoisomerase II with a molecular modelling study.…”

DNA topoisomerase II, genotoxicity, and cancer

“…They represent the most abundant natural source of antioxidants, potently inhibit tyrosine kinases, and exhibit anti-proliferative and pro-apoptotic affects leaves [105][106][107][108][109][112][113][114][115][116]. However, they also display cytotoxic and genotoxic properties and many are potent topoisomerase II poisons [117][118][119][120]. Although the physiological actions of bioflavonoids are complex, the sensitivity of cells to genistein-induced toxicity has been correlated to the activity of the type II enzyme [119,121].…”

A simple and robust high-performance liquid chromatography coupled to a diode-array detector method for the analysis of genistein in mouse tissues

“…Soy is a very important constituent in Asian and vegetarian nutrition [2], and represents a huge economic impact on society. Additionally, epidemiological studies suggest that GEN helps to protect against cancer [3][4][5][6][7], cardiovascular diseases [8], osteoporosis [9], age-related diseases [10] and inflammation processes [11]. Probably the most attractive activity of this bioflavonoid is its promising chemopreventive activity, which works by inducing either G 2 /M or G 0 /G 1 cell cycle arrest depending on the cell line [12][13][14].…”