Search Results (51)

Background/Objectives: DNA damage response (DDR) is a highly conserved and complex signal transduction network required for preserving genome integrity. DNA repair pathways downstream of DDR include the tyrosyl-DNA phosphodiesterase1 (TDP1) enzyme that hydrolyses the phosphodiester bond between the tyrosine residue of topoisomerase I (TopI) and 3′-phosphate end of DNA. A small TDP1 subfamily, composed of TDP1α and TDP1β, is present in plants. The aim of this work was to investigate the role of the two TDP1 genes in the DDR context. Methods: A series of Arabidopsis thaliana DDR single and double mutants defective in the sog1, e2fb, pol2A, atm, and atr genes, treated with the genotoxic agents camptothecin (CPT, inhibitor of TopI) and NSC120686 (NSC, inhibitor of TDP1), were used. These compounds were specifically used due to their known impact on the TDP1 function. The effect of the treatments was assessed via phenotypic analyses that included germination percentage, speed, and seedling growth. Subsequently, the expression of the TDP1α and TDP1β genes was monitored through qRT-PCR. Results: Overall, the gathered data indicate that the atm mutant was highly sensitive to NSC120686, both phenotypically and concerning the TDP1α gene expression profiles. Alternatively, the upregulation of TDP1β in e2fb, pol2a, and atr supports its implication in the replication stress response. Conclusions: The current study demonstrates that genotoxic stress induced by CPT and NSC has a genotype-dependent effect reflected by a differential expression of TDP1 genes and early phenotypic development. Full article

Tyrosyl-DNA phosphodiesterases 1 and 2 (TDP1 and TDP2) are important DNA repair enzymes that remove various adducts from the 3′- and 5′-ends of DNA, respectively. The suppression of the activity of these enzymes is considered as a promising adjuvant therapy for oncological diseases in combination with topoisomerase inhibitors. The simultaneous inhibition of TDP1 and TDP2 may result in greater antitumor effects, as these enzymes can mimic each other’s functions. We have previously shown that usnic acid-based sulfides can act as dual inhibitors, with TDP1 activity in the low micromolar range and their TDP2 at 1 mM. The oxidation of their sulfide moieties to sulfoxides led to an order of magnitude decrease in their cytotoxicity potential, while their TDP1 and TDP2 activity was preserved. In this work, we synthesized new series of usnic acid-based sulfides and their oxidized analogues, i.e., sulfoxides and sulfones, to systematically study these irregularities. The new compounds inhibit TDP1 with IC₅₀ values (the concentration of inhibitor required to reduce enzyme activity by half) in the 0.33–25 μM range. Most sulfides and some sulfoxides and sulfones inhibit TDP2 with an IC₅₀ = 138−421 μM. In addition, the most active compounds synergized (×4) with topotecan on the HeLa cell line as well as causing dose-dependent DNA damage, as confirmed by Comet assay. Sulfides with the 6-methylbenzoimidazol-2-yl substituent (8f, IC₅₀ = 0.33/138 μM, TDP1/2) and sulfones containing a pyridine-2-yl fragment (12k, IC₅₀ = 2/228 μM, TDP1/2) are the most potent derivatives and, therefore, are promising for further development. Full article

Cationic antimicrobial peptides (AMPs), also called host defence peptides, have established antimicrobial and anticancer activities. Conjugation of an AMP to a bioactive molecule with complementary activity can address some of the clinical limitations of the peptide candidate. This approach has been particularly applied in antimicrobial applications of AMPs, but it remains relatively less explored in the generation of anticancer candidates. In this study, two usnic acid derivatives, based on hydrazinothiazole and benzylidenefuranone pharmacophore moieties, respectively, were conjugated to L-K6, a lysine/leucine-rich AMP, through a new pyrazole ligation intrinsically driven by the cargo molecule. Both components, the usnic acid derivative and the peptide, are selectively active against cancer cells, by targeting the human DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 (TDP1) and through DNA damage, respectively. The two conjugates, based on a hydrazone linkage, exhibited pleiotropic effects, ranging from reduction in the activity of the parent drugs to their conservation or even enhancement. Notably, the conjugates retained some anti-TDP1 activity and displayed intermediate, or even higher, cytotoxicities against glioblastoma cells, compared to their individual components. Full article

Nitrogen-associated protein 50 (NAP50) is an abundant plastid protein with an unknown function identified in Alexandrium affine (Dinophyceae). No progress has been made in discovering the function of NAP50 since its first characterization in 2009. The present study is a continuation of work on the predicted function of NAP50. The results show that the NAP50 gene lacks introns but contains abundant base substitutions, consistent with the characteristics of dinoflagellate nuclear genes. The NAP50 protein is found to be widely expressed in dinoflagellate lineages through bioinformatics analysis and Western blotting, suggesting that NAP50 is not exclusive to Alexandrium, which differs from previous understandings. Phylogenetic analysis reveals that NAP50 belongs to the tyrosyl–DNA phosphodiesterase (TDP) family; however, it is structurally distinct from the TDP2 that is present in some dinoflagellate species. The three-dimensional structure and biological functions of NAP50 are predicted using deep learning algorithms. Based on evolutionary relationships and functional predictions, NAP50 may play a role in repairing plastid DNA damage and potentially contribute to the transcription of plastid genes in dinoflagellates. Full article

Background: Tyrosyl-DNA phosphodiesterase 1 (Tdp1) repairs damages in DNA induced by abortive topoisomerase 1 activity; however, maintenance of genetic integrity may sustain cellular division of neoplastic cells. It follows that Tdp1-targeting chemical inhibitors could synergize well with existing chemotherapy drugs to deny cancer growth; therefore, identification of Tdp1 inhibitors may advance precision medicine in oncology. Objective: Current computational research efforts focus primarily on molecular docking simulations, though datasets involving three-dimensional molecular structures are often hard to curate and computationally expensive to store and process. We propose the use of simplified molecular input line entry system (SMILES) chemical representations to train supervised machine learning (ML) models, aiming to predict potential Tdp1 inhibitors. Methods: An open-sourced consensus dataset containing the inhibitory activity of numerous chemicals against Tdp1 was obtained from Kaggle. Various ML algorithms were trained, ranging from simple algorithms to ensemble methods and deep neural networks. For algorithms requiring numerical data, SMILES were converted to chemical descriptors using RDKit, an open-sourced Python cheminformatics library. Results: Out of 13 optimized ML models with rigorously tuned hyperparameters, the random forest model gave the best results, yielding a receiver operating characteristics-area under curve of 0.7421, testing accuracy of 0.6815, sensitivity of 0.6444, specificity of 0.7156, precision of 0.6753, and F1 score of 0.6595. Conclusions: Ensemble methods, especially the bootstrap aggregation mechanism adopted by random forest, outperformed other ML algorithms in classifying Tdp1 inhibitors from non-inhibitors using SMILES. The discovery of Tdp1 inhibitors could unlock more treatment regimens for cancer patients, allowing for therapies tailored to the patient’s condition. Full article

Deoxycholic acid derivatives containing various heterocyclic functional groups at C-3 on the steroid scaffold were designed and synthesized as promising dual tyrosyl-DNA phosphodiesterase 1 and 2 (TDP1 and TDP2) inhibitors, which are potential targets to potentiate topoisomerase poison antitumor therapy. The methyl esters of DCA derivatives with benzothiazole or benzimidazole moieties at C-3 demonstrated promising inhibitory activity in vitro against TDP1 with IC₅₀ values in the submicromolar range. Furthermore, methyl esters 4d–e, as well as their acid counterparts 3d–e, inhibited the phosphodiesterase activity of both TDP1 and TDP2. The combinations of compounds 3d–e and 4d–e with low-toxic concentrations of antitumor drugs topotecan and etoposide showed significantly greater cytotoxicity than the compounds alone. The docking of the derivatives into the binding sites of TDP1 and TDP2 predicted plausible binding modes of the DCA derivatives. Full article

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an important DNA repair enzyme and one of the causes of tumor resistance to topoisomerase 1 inhibitors such as topotecan. Inhibitors of this Tdp1 in combination with topotecan may improve the effectiveness of therapy. In this work, we synthesized usnic acid derivatives, which are hybrids of its known derivatives: tumor sensitizers to topotecan. New compounds inhibit Tdp1 in the micromolar and submicromolar concentration range; some of them enhance the effect of topotecan on the metabolic activity of cells of various lines according to the MTT test. One of the new compounds (compound 7) not only sensitizes Krebs-2 and Lewis carcinomas of mice to the action of topotecan, but also normalizes the state of the peripheral blood of mice, which is disturbed in the presence of a tumor. Thus, the synthesized substances may be the prototype of a new class of additional therapy for cancer. Full article

New imidazolidine-2,4,5-triones with norabietic, nordehydroabietic, and adamantane substituents were synthesized by reacting oxalyl chloride and the corresponding ureas, providing good yields. Bioisosteric replacement of the ureide group with a parabanic acid fragment made it possible to increase the solubility of compounds and conduct biological studies. The compounds inhibit the DNA repair enzyme tyrosyl-DNA phosphodiesterase 1 in submicromolar concentrations. Cytotoxic concentrations were also studied on the glioblastoma cell line SNB19. Full article

Tyrosyl-DNA phosphodiesterase 1 and 2 (Tdp1 and Tdp2) are DNA repair enzymes that repair DNA damage caused by various agents, including anticancer drugs. Thus, these enzymes resist anticancer therapy and could be the reason for resistance to such widely used drugs such as topotecan and etoposide. In the present work, we found compounds capable of inhibiting both enzymes among derivatives of (−)-usnic acid. Both (+)- and (−)-enantiomers of compounds act equally effectively against Tdp1 with IC₅₀ values in the range of 0.02–0.2 μM; only (−)-enantiomers inhibited Tdp2 with IC₅₀ values in the range of 6–9 μM. Surprisingly, the compounds protect HEK293FT wild type cells from the cytotoxic effect of etoposide (CC₅₀ 3.0–3.9 μM in the presence of compounds and 2.4 μM the presence of DMSO) but potentiate it against Tdp2 knockout cells (CC₅₀ 1.2–1.6 μM in the presence of compounds against 2.3 μM in the presence of DMSO). We assume that the sensitizing effect of the compounds in the absence of Tdp2 is associated with the effective inhibition of Tdp1, which could take over the functions of Tdp2. Full article

Tyrosyl-DNA-phosphodiesterase 1 (TDP1) is an important enzyme in the DNA repair system. The ability of the enzyme to repair DNA damage induced by a topoisomerase 1 poison such as the anticancer drug topotecan makes TDP1 a promising target for complex antitumor therapy. In this work, a set of new 5-hydroxycoumarin derivatives containing monoterpene moieties was synthesized. It was shown that most of the conjugates synthesized demonstrated high inhibitory properties against TDP1 with an IC₅₀ in low micromolar or nanomolar ranges. Geraniol derivative 33a was the most potent inhibitor with IC₅₀ 130 nM. Docking the ligands to TDP1 predicted a good fit with the catalytic pocket blocking access to it. The conjugates used in non-toxic concentration increased cytotoxicity of topotecan against HeLa cancer cell line but not against conditionally normal HEK 293A cells. Thus, a new structural series of TDP1 inhibitors, which are able to sensitize cancer cells to the topotecan cytotoxic effect has been discovered. Full article

The tyrosyl-DNA phosphodiesterase 1 (TDP1) enzyme hydrolyzes the phosphodiester bond between a tyrosine residue and the 3′-phosphate of DNA in the DNA–topoisomerase I (TopI) complex, being involved in different DNA repair pathways. A small TDP1 gene subfamily is present in plants, where TDP1α has been linked to genome stability maintenance, while TDP1β has unknown functions. This work aimed to comparatively investigate the function of the TDP1 genes by taking advantage of the rich transcriptomics databases available for the Arabidopsis thaliana model plant. A data mining approach was carried out to collect information regarding gene expression in different tissues, genetic backgrounds, and stress conditions, using platforms where RNA-seq and microarray data are deposited. The gathered data allowed us to distinguish between common and divergent functions of the two genes. Namely, TDP1β seems to be involved in root development and associated with gibberellin and brassinosteroid phytohormones, whereas TDP1α is more responsive to light and abscisic acid. During stress conditions, both genes are highly responsive to biotic and abiotic treatments in a time- and stress-dependent manner. Data validation using gamma-ray treatments applied to Arabidopsis seedlings indicated the accumulation of DNA damage and extensive cell death associated with the observed changes in the TDP1 genes expression profiles. Full article

Etoposide (ETO) is an anticancer drug that targets topoisomerase II (TOP2). It stabilizes a normally transient TOP2–DNA covalent complex (TOP2cc), thus leading to DNA double-strand breaks (DSBs). Tyrosyl-DNA phosphodiesterases two (TDP2) is directly involved in the repair of TOP2cc by removing phosphotyrosyl peptides from 5′-termini of DSBs. Recent studies suggest that additional factors are required for TOP2cc repair, which include the proteasome and the zinc finger protein associated with TDP2 and TOP2, named ZATT. ZATT may alter the conformation of TOP2cc in a way that renders the accessibility of TDP2 for TOP2cc removal. In this study, our genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) screens revealed that ZATT also has a TDP2-independent role in promoting cell survival following ETO treatment. ZATT KO cells showed relatively higher ETO sensitivity than TDP2-KO cells, and ZATT/TDP2 DKO cells displayed additive hypersensitivity to ETO treatment. The study using a series of deletion mutants of ZATT determined that the N-terminal 1–168 residues of ZATT are required for interaction with TOP2 and this interaction is critical to ETO sensitivity. Moreover, depletion of ZATT resulted in accelerated TOP2 degradation after ETO or cycloheximide (CHX) treatment, suggesting that ZATT may increase TOP2 stability and likely participate in TOP2 turnover. Taken together, this study suggests that ZATT is a critical determinant that dictates responses to ETO treatment and targeting. ZATT is a promising strategy to increase ETO efficacy for cancer therapy. Full article

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is an important repair enzyme that removes various covalent adducts from the 3′ end of DNA. Particularly, covalent complexes of topoisomerase 1 (TOP1) with DNA stabilized by DNA damage or by various chemical agents are an examples of such adducts. Anticancer drugs such as the TOP1 poisons topotecan and irinotecan are responsible for the stabilization of these complexes. TDP1 neutralizes the effect of these anticancer drugs, eliminating the DNA adducts. Therefore, the inhibition of TDP1 can sensitize tumor cells to the action of TOP1 poisons. This review contains information about methods for determining the TDP1 activity, as well as describing the inhibitors of these enzyme derivatives of natural biologically active substances, such as aminoglycosides, nucleosides, polyphenolic compounds, and terpenoids. Data on the efficiency of combined inhibition of TOP1 and TDP1 in vitro and in vivo are presented. Full article

Topoisomerase 1 (TOP1) is an enzyme that regulates DNA topology and is essential for replication, recombination, and other processes. The normal TOP1 catalytic cycle involves the formation of a short-lived covalent complex with the 3′ end of DNA (TOP1 cleavage complex, TOP1cc), which can be stabilized, resulting in cell death. This fact substantiates the effectiveness of anticancer drugs—TOP1 poisons, such as topotecan, that block the relegation of DNA and fix TOP1cc. Tyrosyl-DNA phosphodiesterase 1 (TDP1) is able to eliminate TOP1cc. Thus, TDP1 interferes with the action of topotecan. Poly(ADP-ribose) polymerase 1 (PARP1) is a key regulator of many processes in the cell, such as maintaining the integrity of the genome, regulation of the cell cycle, cell death, and others. PARP1 also controls the repair of TOP1cc. We performed a transcriptomic analysis of wild type and PARP1 knockout HEK293A cells treated with topotecan and TDP1 inhibitor OL9-119 alone and in combination. The largest number of differentially expressed genes (DEGs, about 4000 both up- and down-regulated genes) was found in knockout cells. Topotecan and OL9-119 treatment elicited significantly fewer DEGs in WT cells and negligible DEGs in PARP1-KO cells. A significant part of the changes caused by PARP1-KO affected the synthesis and processing of proteins. Differences under the action of treatment with TOP1 or TDP1 inhibitors alone were found in the signaling pathways for the development of cancer, DNA repair, and the proteasome. The drug combination resulted in DEGs in the ribosome, proteasome, spliceosome, and oxidative phosphorylation pathways. Full article

Tyrosyl-DNA-phosphodiesterase 1 (TDP1) is a promising target for antitumor therapy; the use of TDP1 inhibitors with a topoisomerase 1 poison such as topotecan is a potential combination therapy. In this work, a novel series of 3,5-disubstituted thiazolidine-2,4-diones was synthesized and tested against TDP1. The screening revealed some active compounds with IC₅₀ values less than 5 μM. Interestingly, compounds 20d and 21d were the most active, with IC₅₀ values in the submicromolar concentration range. None of the compounds showed cytotoxicity against HCT-116 (colon carcinoma) and MRC-5 (human lung fibroblasts) cell lines in the 1–100 μM concentration range. Finally, this class of compounds did not sensitize cancer cells to the cytotoxic effect of topotecan. Full article