Substituted 4,5′-Bithiazoles as Catalytic Inhibitors of Human DNA Topoisomerase IIα

Abstract

Human type II topoisomerases, molecular motors that alter the DNA topology, are a major target of modern chemotherapy. Groups of catalytic inhibitors represent a new approach to overcome the known limitations of topoisomerase II poisons such as cardiotoxicity and induction of secondary tumors. Here, we present a class of substituted 4,5′-bithiazoles as catalytic inhibitors targeting the human DNA topoisomerase IIα. Based on a structural comparison of the ATPase domains of human and bacterial type II topoisomerase, a focused chemical library of 4,5′-bithiazoles was assembled and screened to identify compounds that better fit the topology of the human topo IIα adenosine 5′-triphosphate (ATP) binding site. Selected compounds showed inhibition of human topo IIα comparable to that of the etoposide topo II drug, revealing a new class of inhibitors targeting this molecular motor. Further investigations showed that compounds act as catalytic inhibitors via competitive ATP inhibition. We also confirmed binding to the truncated ATPase domain of topo IIα and modeled the inhibitor molecular recognition with molecular simulations and dynophore models. The compounds also displayed promising cytotoxicity against HepG2 and MCF-7 cell lines comparable to that of etoposide. In a more detailed study with the HepG2 cell line, there was no induction of DNA double-strand breaks (DSBs), and the compounds were able to reduce cell proliferation and stop the cell cycle mainly in the G1 phase. This confirms the mechanism of action of these compounds, which differs from topo II poisons also at the cellular level. Substituted 4,5′-bithiazoles appear to be a promising class for further development toward efficient and potentially safer cancer therapies exploiting the alternative topo II inhibition paradigm.

Catalytic Mechanism of ATP Hydrolysis in the ATPase Domain of Human DNA Topoisomerase IIα

“… 30 , 31 These molecules include a class that targets the ATP binding site of htIIα and predominantly mimics the adenine moiety of ATP, with a variety of scaffolds already discovered and validated. 32 − 35 Such inhibition of topo II would, in principle, not result in an induction of excessive DNA damage, characterized by the DNA double strand breaks that are one of the main triggers of severe adverse effects observed when administering topo II poisons (e.g., etoposide and doxorubicin). These harmful effects comprise incidences of secondary malignancies after chemotherapy and cardiotoxicity.…”

“…The ATPase domain of htIIα is also a promising new target site for an emerging class of potential anticancer drugs, called catalytic topo II inhibitors. , These molecules include a class that targets the ATP binding site of htIIα and predominantly mimics the adenine moiety of ATP, with a variety of scaffolds already discovered and validated. − Such inhibition of topo II would, in principle, not result in an induction of excessive DNA damage, characterized by the DNA double strand breaks that are one of the main triggers of severe adverse effects observed when administering topo II poisons (e.g., etoposide and doxorubicin). These harmful effects comprise incidences of secondary malignancies after chemotherapy and cardiotoxicity. − Furthermore, the increased occurrence drug resistance to clinically used topo II poisons further fuels the need for revisiting this established anticancer target …”

Dynophore-Based Approach in Virtual Screening: A Case of Human DNA Topoisomerase IIα

“…They were included in docking because previous studies suggest they play an important role in binding of the native molecule [46,66]. The AMP-PNP molecule was docked into the defined active site by applying the following parameters of the GOLD genetic algorithm (GA): population size = 100, selection pressure = 1.1, No.…”

Phenotypic Discovery of Thiocarbohydrazone with Anticancer Properties and Catalytic Inhibition of Human DNA Topoisomerase IIα

“…To avoid these side effects, an emerging group of catalytic topo II inhibitors was extensively studied [ 12 ]. These compounds interfere with the catalytic cycle of topo II without inducing DNA damage, acting through several mechanisms such as preventing DNA cleavage, competing with ATP for the same binding site [ 13 , 14 , 15 ] to prevent ATP hydrolysis, and interfering with DNA–topo II binding [ 16 ].…”