The Aza-Analogous Benzo[c]phenanthridine P8-D6 Acts as a Dual Topoisomerase I and II Poison, thus Exhibiting Potent Genotoxic Properties

Abstract

The benzo[c]phenanthridine P8-D6 was recently found to suppress the catalytic activity of both human topoisomerase (Topo) I and II. Concomitantly, potent cytotoxic activity was observed in different human tumor cell lines, raising questions about the underlying mechanisms in vitro. In the present study, we addressed the question of whether P8-D6 acts as a so-called Topo poison, stabilizing the covalent Topo–DNA intermediate, thus inducing fatal DNA strand breaks in proliferating cells. In HT-29 colon carcinoma cells, fluorescence imaging revealed P8-D6 to be taken up by the cells and to accumulate in the perinuclear region. Confocal microscopy demonstrated that the compound is partially located inside the nuclei, thus reaching the potential target. In the “in vivo complex of enzyme” (ICE) bioassay, treatment of HT-29 cells with P8-D6 for 1 h significantly enhanced the proportion of Topo I and II covalently linked to the DNA in concentrations ≥1 µM, indicating effective dual Topo poisoning. Potentially resulting DNA damage was analyzed by single-cell gel electrophoresis (“comet assay”). Already at 1 h of incubation, significant genotoxic effects were observed in the comet assay in concentrations as low as 1 nM. Taken together, the present study demonstrates the high Topo-poisoning and genotoxic potential of P8-D6 in human tumor cells.

Newly Synthesized Imino-Derivatives Analogues of Resveratrol Exert Inhibitory Effects in Breast Tumor Cells

“…Sodium salts (E)-4-(2,5-dihydroxy benzylidene)-imino-sodium benzoate (4) was obtained by reaction of (3) with sodium bicarbonate in aqueous solution with a yield of 28%. (E)-4-(3,5-dihydroxybenzylidene)-imino-benzoic acid (6) was obtained by reaction of 3,5-dihydroxybenzaldeyde (5) with 4-aminobenzoic acid (2) in methanol (Scheme 2). The solution was stirred and refluxed for 24 h. After evaporation of the solvent in vacuum, a solid obtained was washed several times with CHCl 3 to afford the pure product (6), yield 17%.…”

“…1 H and 13 C NMR chemical shifts are consistent with the proposed structures. In the NMR spectra of compounds (3), ( 4), (6), and (7), signals related to the imminic group are diagnostic. In the 1 H NMR the signals of the imminic proton (CH = N) of the four compounds are attributed to 8.87, 8.83, 9.60, and 8.48 ppm, respectively.…”

“…A large body of studies has been performed in order to characterize the mechanisms of action of the above-mentioned compounds. Certain agents are able to inhibit the human topoisomerases I and II (hTopoI and II), crucial enzymes involved in the DNA replication, transcription, recombination and chromatin remodeling [ 3 , 4 , 5 , 6 ]. For instance, cisplatin is known for its ability to interact with many types of proteins regulating the DNA replication and cell division like DNA topoisomerase II [ 7 ].…”

Newly Developed Dual Topoisomerase Inhibitor P8-D6 is Highly Active in Ovarian Cancer

“…Consequently, an important aim is to reduce mortality by improved new therapeutic options. P8-D6 acts as a dual topoisomerase poison by stabilizing the covalent Topo-DNA-intermediate of both topoisomerase (Topo) enzymes I and II (4). Topoisomerases regulate torsional stress in DNA to enable essential genome functions (e.g.…”

Synthesis, anticancer evaluation and molecular docking studies of new benzimidazole- 1,3,4-oxadiazole derivatives as human topoisomerase types I poison

“…Human Topo are divided into two classes: Topoisomerase I (topo I), breaks only one strand of DNA and Topoisomerase II (topo II), breaks both strands of DNA 9–11 . Several Topo poisons have been approved for the chemotherapeutic treatment of different cancer types in recent decades, including the Topo I inhibitors camptothecin, topotecan and the Topo-II-targeting drugs etoposide and amsacrin 12 , 13 .…”