The impact of Thiopeptide antibiotics on inflammatory responses in periodontal tissues through the regulation of the MAPK pathway

Periodontitis is a bacteria-induced inflammatory disease that damages the tissues supporting the teeth, gums, periodontal ligaments, and alveolar bone. Conventional treatments such as surgical procedures, anti-inflammatory drugs, and antibiotics, are somewhat effective; however, these may lead to discomfort and adverse events, thereby affecting patient outcomes. Therefore, this study aimed to find an effective method to prevent the onset of periodontal disease and explore the specific mechanisms of their action.The impact of thiostrepton on Porphyromonas gingivalis and periodontal ligament stem cells was evaluated in an inflammatory microenvironment. In vivo experiments were performed using a mouse periodontitis model to assess the effectiveness of locally applied thiostrepton combined with a silk fibroin hydrogel in impeding periodontitis progression. Thiostrepton exhibited significant antimicrobial effects against Porphyromonas gingivalis and anti-inflammatory properties by regulating the MAPK pathway through DUSP2. Locally applied thiostrepton effectively impeded the progression of periodontitis and reduced tissue damage. Thiostrepton treatment is a promising and tolerable preventive strategy for periodontitis, offering antimicrobial and anti-inflammatory benefits. These findings suggest the potential of thiostrepton as a valuable addition to periodontitis management, warranting further research and clinical exploration to improve patient outcomes.

Thiostrepton suppresses triple-negative breast cancer through downregulating c-FLIP/SMAD2/3 signaling pathway

Triple-negative breast cancer (TNBC) is an aggressive subtype with poor prognosis of breast cancer. Thiostrepton exerts anti-tumor activities against several cancers including TNBC. Herein we discussed the new molecular mechanisms of thiostrepton in TNBC. Thiostrepton inhibited MDA-MB-231 cell viability, accompanied by a decrease of c-FLIP and p-SMAD2/3. c-FLIP overexpression reduced the sensitivity of MDA-MB-231 cells to thiostrepton, while SMAD2/3 knockdown increased the sensitivity of MDA-MB-231 cells to thiostrepton. Moreover, c-FLIP overexpression significantly increased the expression and phosphorylation of SMAD2/3 proteins and vice versa. In conclusion, our study reveals c-FLIP/SMAD2/3 signaling pathway as a novel mechanism of antitumor activity of thiostrepton.

Selective Aza-Michael Addition to Dehydrated Amino Acids in Natural Antimicrobial Peptides

We report the efficient and site selective modification of non-canonical dehydroamino acids in ribosomally synthesized and post-transationally modified peptides (RiPPs) by β-amination. The singly modified thiopeptide Thiostrepton showed an up to 35-fold increase in water solubility, and minimum inhibitory concentration (MIC) assays showed that antimicrobial activity remained good, albeit lower than the unmodified peptide. Also the lanthipeptide nisin could be modified using this method.

FOXM1: a new therapeutic target of extramammary Paget disease

Extramammary Paget disease (EMPD) is a rare skin cancer that primarily affects older individuals predominantly in areas with apocrine sweat glands. Although most early EMPD lesions are indolent, patients with metastatic EMPD have a poor prognosis due to the lack of effective systemic treatment. In this study, we investigated the role of forkhead box M1 (FOXM1), a potent transcription factor, in EMPD and assessed the potential of FOXM1 as a therapeutic target. Immunohistochemistry of 112 primary and 17 metastatic EMPD samples revealed that FOXM1 expression increased with tumor progression. Patients in whom FOXM1 was expressed in more than 10% of tumor cells had significantly shorter disease-specific survival than the other patients (p = 0.0397). In in vitro studies using our newly established EMPD cell line, KS-EMPD-1, we found high expression of FOXM1. Knockdown of FOXM1 impaired tumor cell viability, migration, and invasion. Inhibition of FOXM1 using thiostrepton also reduced tumor cell viability in a dose-dependent manner. These findings suggest that FOXM1 is a promising therapeutic target for patients with EMPD.

Development of a thiostrepton-free system for stable production of PLD in Streptomyces lividans SBT5

BACKGROUND

Phospholipase D (PLD) is highly valuable in the food and medicine industries, where it is used to convert low-cost phosphatidylcholine into high-value phospholipids (PLs). Despite being overexpressed in Streptomyces, PLD production requires expensive thiostrepton feeding during fermentation, limiting its industrialization. To address this issue, we propose a new thiostrepton-free system.

RESULTS

We developed a system using a combinatorial strategy containing the constitutive promoter kasOp* and PLD G215S mutation fused to a signal peptide sigcin of Streptoverticillium cinnamoneum pld. To find a candidate vector, we first expressed PLD using the integrative vector pSET152 and then built three autonomously replicating vectors by substituting Streptomyces replicons to increase PLD expression. According to our findings, replicon 3 with stability gene (sta) inserted had an ideal result. The retention rate of the plasmid pOJ260-rep3-pld* was 99% after five passages under non-resistance conditions. In addition, the strain SK-3 harboring plasmid pOJ260-rep3-pld* produced 62 U/mL (3.48 mg/g) of PLD, which further improved to 86.8 U/mL (7.51 mg/g) at 32 °C in the optimized medium, which is the highest activity achieved in the PLD secretory expression to date.

CONCLUSIONS

This is the first time that a thiostrepton-free PLD production system has been reported in Streptomyces. The new system produced stable PLD secretion and lays the groundwork for the production of PLs from fermentation stock. Meanwhile, in the Streptomyces expression system, we present a highly promising solution for producing other complex proteins.

Effects of thiostrepton alone or in combination with selumetinib on triple-negative breast cancer metastasis

OBJECTIVE

FoxM1 transcription factor contributes to tumor metastasis and poor prognosis in many cancers including triple-negative breast cancer (TNBC). In this study, we examined the effects of FoxM1 inhibitor Thiostrepton (THIO) alone or in combination with MEK inhibitor Selumetinib (SEL) on metastatic parameters in vitro and in vivo.

METHODS

Cell viability was determined by MTT assay. Immunoblotting and immunohistochemistry was used to assess metastasis-related protein expressions in 4T1 cells and its allograft tumor model in BALB/c mice. In vivo uPA activity was determined by enzymatic methods.

RESULTS

Both inhibitors were effective on the expressions of FoxM1, ERK, p-ERK, Twist, E-cadherin, and Vimentin alone or in combination in vitro. THIO significantly decreased 4T1 cell migration and changed the cell morphology from mesenchymal-like to epithelial-like structure. THIO was more effective than in combination with SEL in terms of metastatic protein expressions in vivo. THIO alone significantly inhibited mean tumor growth, decreased lung metastasis rate and tumor foci, however, no significant changes in these parameters were observed in the combined group. Immunohistochemically, FoxM1 expression intensity was decreased with THIO and its combination with SEL in the tumors.

CONCLUSIONS

This study suggests that inhibiting FoxM1 as a single target is more effective than combined treatment with MEK in theTNBC allograft model. The therapeutic efficacy of THIO should be investigated with further studies on appropriate drug delivery systems.

Structural characterization of cobalamin-dependent radical S-adenosylmethionine methylases

Cobalamin-dependent radical S-adenosylmethionine (SAM) methylases catalyze key steps in the biosynthesis of numerous biomolecules, including protein cofactors, antibiotics, herbicides, and other natural products, but have remained a relatively understudied subclass of radical SAM enzymes due to their inherent insolubility upon overproduction in Escherichia coli. These enzymes contain two cofactors: a [4Fe-4S] cluster that is ligated by three cysteine residues, and a cobalamin cofactor typically bound by residues in the N-terminal portion of the enzyme. Recent advances in the expression and purification of these enzymes in their active states and with both cofactors present has allowed for more detailed biochemical studies as well as structure determination by X-ray crystallography. Herein, we use KsTsrM and TokK to highlight methods for the structural characterization of cobalamin-dependent radical SAM (RS) enzymes and describe recent advances in in the overproduction and purification of these enzymes.

The bacterial thiopeptide thiostrepton. An update of its mode of action, pharmacological properties and applications

The bacterial thiopeptide thiostrepton (TS) is used as a veterinary medicine to treat bacterial infections. TS is a protein translation inhibitor, essentially active against Gram-positive bacteria and some Gram-negative bacteria. In procaryotes, TS abrogates binding of GTPase elongation factors to the 70S ribosome, by altering the structure of rRNA-L11 protein complexes. TS exerts also antimalarial effects by disrupting protein synthesis in the apicoplast genome of Plasmodium falciparum. Interestingly, the drug targets both the infectious pathogen (bacteria or parasite) and host cell, by inducing endoplasmic reticulum stress-mediated autophagy which contributes to enhance the host cell defense. In addition, TS has been characterized as a potent chemical inhibitor of the oncogenic transcription factor FoxM1, frequently overexpressed in cancers or other diseases. The capacity of TS to crosslink FoxM1, and a few other proteins such as peroxiredoxin 3 (PRX3) and the 19S proteasome, contributes to the anticancer effects of the thiopeptide. The anticancer activities of TS evidenced using diverse tumor cell lines, in vivo models and drug combinations are reviewed here, together with the implicated targets and mechanisms. The difficulty to formulate TS is a drag on the pharmaceutical development of the natural product. However, the design of hemisynthetic analogues and the use of micellar drug delivery systems should facilitate a broader utilization of the compound in human and veterinary medicines. This review shed light on the many pharmacological properties of TS, with the objective to promote its use as a pharmacological tool and medicinal product.

Thiostrepton inhibits growth and induces apoptosis by targeting FoxM1/SKP2/MTH1 axis in B-precursor acute lymphoblastic leukemia cells

Forkhead box M1 (FoxM1) is a transcription factor that plays an important role in the etiology of many cancers, however, its role has not been elucidated in B-precursor acute lymphoblastic leukemia (B-pre-ALL). In the current study, we showed that the downregulation of FoxM1 by its inhibitor thiostrepton inhibited cell viability and induced caspase-dependent apoptosis in a panel of B-pre-ALL cell lines. Thiostrepton led downregulation of FoxM1 accompanied by decreased expression of Aurora kinase A, B, matrix metalloproteinases, and oncogene SKP2 as well as MTH1. Downregulation of the FoxM1/SKP2/MTH1 axis led to increase in the Bax/Bcl2 ratio and suppression of antiapoptotic proteins. Thiostrepton-mediated apoptosis was prevented by N-acetyl cysteine, a scavenger of reactive oxygen species. Co-treatment of B-pre-ALL with subtoxic doses of thiostrepton and bortezomib potentiated the proapoptotic action. Altogether, our results suggest that targeting FoxM1expression could be an attractive strategy for the treatment of B-pre-ALL.

Liposomal Thiostrepton Formulation and Its Effect on Breast Cancer Growth Inhibition

Forkhead box M1 (FOXM1) is known to play a role in breast cancer progression. FOXM1 inhibition becomes one of the strategies in developing the novel cancer therapy. Recently, thiostrepton has been recognized as a potent FOXM1 inhibitor. To improve its potential, we aimed to develop a nanodelivery system for thiostrepton. Here, liposome-encapsulated thiostrepton (TSLP) was developed. Physiochemical properties were characterized by TEM and dynamic light scattering technique. The biological activities were also evaluated, by cellular internalization, MTT assay, spheroid formation assay and RT-PCR. The result showed that the range sizes of TSLP were 152 ± 2 nm, polydispersity index (PdI) of 0.23 ± 0.02 and zeta potential of -20.2 ± 0.1 mV. As expected, TSLP showed a higher potential in reducing FOXM1 levels in MCF-7 cells than free thiostrepton. Additionally, TSLP significantly improved the efficiently and specificity of thiostrepton in reducing cell viability of MCF-7, but not of the fibroblast (HDFn) cells. Interestingly, TSLP had an ability to induce MCF-7 cell death in both 2D monolayer and 3D spheroid culture. In conclusions, TSLP could possibly be one of the potential developments using nano-delivery system to improve abilities and specificity of thiostrepton in breast cancer cell inhibition and death inducing, with decreasing non-specific toxicity.

Development of co-solvent freeze-drying method for the encapsulation of water-insoluble thiostrepton in sterically stabilized micelles

The purpose of this work was to develop a practical and scalable method to encapsulate the hydrophobic antibiotic thiostrepton (TST) in sterically stabilized micelles (SSM). Using the conventional method of thin-film hydration, we encapsulated up to 5 drug molecules per SSM (diameter ∼ 16 nm). However, since this method is not suitable for large-scale production - a limiting factor for clinical translation - we applied the co-solvent freeze-drying method using tert-butanol (TBA): water co-solvent system. We found that the presence of phosphate-buffered saline (PBS) salts in the lyophilized cake accelerated the reconstitution time and allowed efficient drug encapsulation without the formation of larger drug particles. In addition, TBA proportion of 50% (v/v) was sufficient to maintain both phospholipid and drug in solution prior to the freeze-drying. The increase of drug and phospholipid concentrations in the formulation extended the reconstitution time and led to drug precipitation. Therefore, to increase the strength of the formulation, we prepared lyophilized cakes with lower phospholipid content (5 mM) and reconstituted them in one-third of the fill volume. In conclusion, we found optimum conditions to prepare TST-SSM using the co-solvent freeze-drying method. This scalable production method can facilitate the further clinical development and industrial production of TST-SSM nanomedicine.

Untying the knot of transcription factor druggability: Molecular modeling study of FOXM1 inhibitors

The FOXM1 protein is a relevant transcription factor involved in cancer cell proliferation. The direct or indirect inhibition of this protein's transcriptional activity by small molecule drugs correlates well with a potentially significant anti-cancer profile, making this macro molecule a promising drug target. There are a few drug molecules reported to interact with (and inhibit) the FOXM1 DNA binding domain (FOXM1-BD), causing downregulation of protein expression and cancer cell proliferation inhibition. Among these drug molecules are the proteasome inhibitor thiostrepton, the former antidiabetic drug troglitazone, and the new FDI-6 molecule. Despite their structural differences, these drugs exert a similar inhibitory profile, and this observation prompted us to study a possible similar mechanism of action. Using a series of molecular dynamics simulations and docking protocols, we identified essential binding interactions exerted by all three classes of drugs, among which, a π-sulfur interaction (between a His287 and a sulfur-containing heterocycle) was the most important. In this report, we describe the preliminary evidence suggesting the presence of a drug-binding pocket within FOXM1 DNA binding domain, in which inhibitors fit to dissociate the protein-DNA complex. This finding suggests a common mechanism of action and a basic framework to design new FOXM1 inhibitors.

Prognostic significance of FOXM1 expression and antitumor effect of FOXM1 inhibition in synovial sarcomas

Background

Synovial sarcoma (SS) is a soft tissue sarcoma of unknown histogenesis. Most metastatic or unresectable cases are incurable. Novel antitumor agents and precise prognostication are needed for SS patients. The protein forkhead box M1 (FOXM1), which belongs to the FOX family of transcription factors, is considered to be an independent predictor of poor survival in many cancers and sarcomas, but the prognostic implications and oncogenic roles of FOXM1 in SS are poorly understood. Here we examined the correlation between FOXM1 expression and clinicopathologic and prognostic factors, and we investigated the efficacy of FOXM1 target therapy in SS cases.

Methods

Immunohistochemical study of 106 tumor specimens was conducted to evaluate their immunohistochemical expression of FOXM1. An in vitro study examined the antitumor effect of the FOXM1 inhibitor thiostrepton and small interference RNA (siRNA) on two SS cell lines. We also assessed the efficacy of the combined use of doxorubicin (DOX) and thiostrepton.

Results

Univariate and multivariate analyses revealed that FOXM1 expression was associated with poor prognosis in SS. The cDNA microarray analysis using clinical samples revealed that the expression of cell cycle-associated genes was correlated with FOXM1 expression. FOXM1 inhibition by thiostrepton showed significant antitumor activity on the SS cell lines in vitro. FOXM1 interruption by siRNA increased the chemosensitivity for DOX in both SS cell lines.

Conclusion

FOXM1 expression is a novel biomarker, and its inhibition is a potential treatment option for SS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2542-4) contains supplementary material, which is available to authorized users.

Functional roles in S-adenosyl-L-methionine binding and catalysis for active site residues of the thiostrepton resistance methyltransferase

Resistance to the antibiotic thiostrepton, in producing Streptomycetes, is conferred by the S-adenosyl-L-methionine (SAM)-dependent SPOUT methyltransferase Tsr. For this and related enzymes, the roles of active site amino acids have been inadequately described. Herein, we have probed SAM interactions in the Tsr active site by investigating the catalytic activity and the thermodynamics of SAM binding by site-directed Tsr mutants. Two arginine residues were demonstrated to be critical for binding, one of which appears to participate in the catalytic reaction. Additionally, evidence consistent with the involvement of an asparagine in the structural organization of the SAM binding site is presented.

Binding induced RNA conformational changes control substrate recognition and catalysis by the thiostrepton resistance methyltransferase (Tsr)

Ribosomal RNA (rRNA) post-transcriptional modifications are essential for ribosome maturation, translational fidelity, and are one mechanism used by both antibiotic-producing and pathogenic bacteria to resist the effects of antibiotics that target the ribosome. The thiostrepton producer Streptomyces azureus prevents self-intoxication by expressing the thiostrepton-resistance methyltransferase (Tsr), which methylates the 2'-hydroxyl of 23 S rRNA nucleotide adenosine 1067 within the thiostrepton binding site. Tsr is a homodimer with each protomer containing an L30e-like amino-terminal domain (NTD) and a SPOUT methyltransferase family catalytic carboxyl-terminal domain (CTD). We show that both enzyme domains are required for high affinity RNA substrate binding. The Tsr-CTD has intrinsic, weak RNA affinity that is necessary to direct the specific high-affinity Tsr-RNA interaction via NTDs, which have no detectable RNA affinity in isolation. RNA structure probing experiments identify the Tsr footprint on the RNA and structural changes in the substrate, induced specifically upon NTD binding, which are necessary for catalysis by the CTD. Additionally, we identify a key amino acid in each domain responsible for CTD-RNA binding and the observed NTD-dependent RNA structural changes. These studies allow us to develop a model for Tsr-RNA interaction in which the coordinated substrate recognition of each Tsr structural domain is an obligatory pre-catalytic recognition event. Our findings underscore the complexity of substrate recognition by RNA modification enzymes and the potential for direct involvement of the RNA substrate in controlling the process of its modification.

The effect of fusidic acid on Plasmodium falciparum elongation factor G (EF-G)

Inhibition of growth of the malaria parasite Plasmodium falciparum by known translation-inhibitory antibiotics has generated interest in understanding their action on the translation apparatus of the two genome containing organelles of the malaria parasite: the mitochondrion and the relic plastid (apicoplast). We report GTPase activity of recombinant EF-G proteins that are targeted to the organelles and further use these to test the effect of the EF-G inhibitor fusidic acid (FA) on the factor-ribosome interface. Our results monitoring locking of EF-G·GDP onto surrogate Escherichia coli ribosomes as well as multi-turnover GTP hydrolysis by the factor indicate that FA has a greater effect on apicoplast EF-G compared to the mitochondrial counterpart. Deletion of a three amino acid (GVG) sequence in the switch I loop that is conserved in proteins of the mitochondrial EF-G1 family and the Plasmodium mitochondrial factor, but is absent in apicoplast EF-G, demonstrated that this motif contributes to differential inhibition of the two EF-Gs by FA. Additionally, the drug thiostrepton, that is known to target the apicoplast and proteasome, enhanced retention of only mitochondrial EF-G on ribosomes providing support for the reported effect of the drug on parasite mitochondrial translation.