Lipopeptides from an isolate of Bacillus subtilis complex have inhibitory and antibiofilm effects on Fusarium solani

Bacillus subtilis species complex is known as lipopeptide-producer with biotechnological potential for pharmaceutical developments. This study aimed to identify lipopeptides from a bacterial isolate and evaluate their antifungal effects. Here, we isolated and identified a lipopeptide-producing bacterium as a species of Bacillus subtilis complex (strain UL-1). Twenty lipopeptides (six iturins, six fengycins, and eight surfactins) were identified in the crude extract (CE) and fractions (F1, F2, F3, and F4), and the highest content of total lipopeptides was observed in CE and F2. The chemical quantification data corroborate with the hemolytic and antifungal activities that CE and F2 were the most hemolytic and inhibited the fungal growth at lower concentrations against Fusarium spp. In addition, they caused morphological changes such as shortening and/or atypical branching of hyphae and induction of chlamydospore-like structure formation, especially in Fusarium solani. CE was the most effective in inhibiting the biofilm formation and in disrupting the mature biofilm of F. solani reducing the total biomass and the metabolic activity at concentrations ≥ 2 µg/mL. Moreover, CE significantly inhibited the adherence of F. solani conidia on contact lenses and nails as well as disrupted the pre-formed biofilms on nails. CE at 100 mg/kg was nontoxic on Galleria mellonella larvae, and it reduced the fungal burden in larvae previously infected by F. solani. Taken together, the lipopeptides obtained from strain UL-1 demonstrated a potent anti-Fusarium effect inducing morphological alterations and antibiofilm activities. Our data open further studies for the biotechnological application of these lipopeptides as potential antifungal agents. KEY POINTS: • Lipopeptides inhibit Fusarium growth and induce chlamydospore-like structures. • Lipopeptides hamper the adherence of conidia and biofilms of Fusarium solani. • Iturins, fengycins, and surfactins were associated with antifungal effects.

Exploring pradimicin-IRD antineoplastic mechanisms and related DNA repair pathways

DNA-targeting agents have a significant clinical use, although toxicity remains an issue that plays against their widespread application. Understanding the mechanism of action and DNA damage response elicited by such compounds might contribute to the improvement of their use in anticancer chemotherapy. In a previous study, our research group characterized a new DNA-targeting agent - pradimicin-IRD. Since DNA-targeting agents and DNA repair are close-related subjects, the present study used in silico-modelling and a transcriptomic approach seeking to characterize the DNA repair pathways activated in HCT 116 cells following pradimicin-IRD treatment. Molecular docking analysis showed pradimicin-IRD as a DNA intercalating agent and a potential inhibitor of DNA-binding proteins. Furthermore, the transcriptomic study highlighted DNA repair functions related to genes modulated by pradimicin-IRD, such as nucleotide excision repair, telomeres maintenance and double-strand break repair. When validating these functions, PCNA protein levels decreased after exposure to pradimicin. Furthermore, molecular docking analysis suggested DNA-pradimicin-PCNA interaction. In addition, hTERT and POLH showed reduced mRNA levels after 6 h of treatment with pradimicin-IRD. Moreover, POLH-deficient cells displayed higher resistance to pradimicin-IRD than POLH-proficient cells and the compound prevented formation of the POLH/DNA complex (molecular docking). Since the modulation of DNA repair genes by pradimicin-IRD is TP53-independent, unlike doxorubicin, dissimilarities between the mechanism of action and the DNA damage response of pradimicin-IRD and doxorubicin open new insights for further studies of pradimicin-IRD as a new antineoplastic compound.

Cytotoxic Cyclotides from Anchietea pyrifolia, a South American Plant Species

Cyclotides are mini-proteins with potent bioactivities and outstanding potential for agricultural and pharmaceutical applications. More than 450 different plant cyclotides have been isolated from six angiosperm families. In Brazil, studies involving this class of natural products are still scarce, despite its rich floristic diversity. Herein were investigated the cyclotides from Anchietea pyrifolia roots, a South American medicinal plant from the family Violaceae. Fourteen putative cyclotides were annotated by LC-MS. Among these, three new bracelet cyclotides, anpy A-C, and the known cycloviolacins O4 (cyO4) and O17 (cyO17) were sequenced through a combination of chemical and enzymatic reactions followed by MALDI-MS/MS analysis. Their cytotoxic activity was evaluated by a cytotoxicity assay against three human cancer cell lines (colorectal carcinoma cells: HCT 116 and HCT 116 TP53^-/- and breast adenocarcinoma, MCF 7). For all assays, the IC₅₀ values of isolated compounds ranged between 0.8 and 7.3 μM. CyO17 was the most potent cyclotide for the colorectal cancer cell lines (IC₅₀, 0.8 and 1.2 μM). Furthermore, the hemolytic activity of anpy A and B, cyO4, and cyO17 was assessed, and the cycloviolacins were the least hemolytic (HD₅₀ > 156 μM). This work sheds light on the cytotoxic effects of the anpy cyclotides against cancer cells. Moreover, this study expands the number of cyclotides obtained to date from Brazilian plant biodiversity and adds one more genus containing these molecules to the list of the Violaceae family.

AD80, a multikinase inhibitor, as a potential drug candidate for colorectal cancer therapy

AIMS

Colorectal cancer (CRC) is a very heterogeneous disease. One of its hallmarks is the dysregulation of protein kinases, which leads to molecular events related to carcinogenesis. Hence, kinase inhibitors have been developed and are a new strategy with promising potential for CRC therapy. This study aims to explore AD80, a multikinase inhibitor, as a drug option for CRC, with evaluation of the PI3K/AKT/mTOR and MAPK (ERK1/2) status of CRC cells' panel and the cytotoxicity of AD80 in those cells, as well as in normal colon cells.

MAIN METHODS

Cellular and molecular mechanisms, such as clonogenicity, cell cycle, morphology, protein, and mRNA expression, were investigated in CRC cells after AD80 exposure.

KEY FINDINGS

Results show that PI3K/AKT/mTOR and MAPK signaling pathways are upregulated in CRC cellular models, with increased phosphorylation of mTOR, P70S6K, S6RP, 4EBP1, and ERK1/2. Hence, AD80 selectively reduces cell viability of CRC cells. Therefore, the antitumor mechanisms of AD80, such as clonogenicity inhibition (reduction of colony number and size), G₂/M arrest (increased G₂/M population, and CDKN1B mRNA expression), DNA damage (increased H2AX and ERK1/2 phosphorylation, and CDKN1A, GADD45A mRNA expression), apoptosis (increased PARP1 cleavage, and BAX, PMAIP1, BBC3 mRNA expression) and inhibition of S6RP phosphorylation were validated in CRC model.

SIGNIFICANCE

Our findings reinforce kinases as promising cancer therapeutic targets for the treatment of colorectal cancer, suggesting AD80 as a drug candidate.

Structure-activity relationship and mechanistic studies for a series of cinnamyl hydroxamate histone deacetylase inhibitors

Histone deacetylases (HDACs) are a family of enzymes that modulate the acetylation status histones and non-histone proteins. Histone deacetylase inhibitors (HDACis) have emerged as an alternative therapeutic approach for the treatment of several malignancies. Herein, a series of urea-based cinnamyl hydroxamate derivatives is presented as potential anticancer HDACis. In addition, structure-activity relationship (SAR) studies have been performed in order to verify the influence of the linker on the biological profile of the compounds. All tested compounds demonstrated significant antiproliferative effects against solid and hematological human tumor cell lines. Among them, 11b exhibited nanomolar potency against hematological tumor cells including Jurkat and Namalwa, with IC₅₀ values of 40 and 200 nM, respectively. Cellular and molecular proliferation studies, in presence of compounds 11a-d, showed significant cell growth arrest, apoptosis induction, and up to 43-fold selective cytotoxicity for leukemia cells versus non-tumorigenic cells. Moreover, compounds 11a-d increased acetylated α-tubulin expression levels, which is phenotypically consistent with HDAC inhibition, and indirectly induced DNA damage. In vitro enzymatic assays performed for 11b revealed a potent HDAC6 inhibitory activity (IC₅₀: 8.1 nM) and 402-fold selectivity over HDAC1. Regarding SAR analysis, the distance between the hydroxamate moiety and the aromatic ring as well as the presence of the double bond in the cinnamyl linker were the most relevant chemical feature for the antiproliferative activity of the series. Molecular modeling studies suggest that cinnamyl hydroxamate is the best moiety of the series for binding HDAC6 catalytic pocket whereas exploration of Ser568 by the urea connecting unity (CU) might be related with the selectivity observed for the cinnamyl derivatives. In summary, cinnamyl hydroxamate derived compounds with HDAC6 inhibitory activity exhibited cell growth arrest and increased apoptosis, as well as selectivity to acute lymphoblastic leukemia cells. This study explores interesting compounds to fight against neoplastic hematological cells.

Novel [6]-gingerol Triazole Derivatives and their Antiproliferative Potential against Tumor Cells

BACKGROUND

Effective cancer treatment is a major public health challenge. The limitations of current therapies and their adverse effects reduce the efficacy of treatment, leading to significant mortality rates worldwide. Moreover, natural product chemistry occupies a prominent role in the search for new treatment alternatives, by contributing a spectrum of chemical structures that may potentially yield new bioactive compounds. The compound [6]-gingerol (1) is the main active substance in ginger (Zingiber officinale) and several studies have shown it to produce beneficial effects, including antitumor activity.

OBJECTIVE

This work aims to obtain new gingerol derivatives with cytotoxic activity.

METHODS

[6]-gingerol was isolated and its derivatives were produced using click chemistry, obtaining eight new compounds. All chemical structures were determined by means of IR, NMR and HRMS data, and cytotoxicity was evaluated in the HCT 116 (colon carcinoma) and MCF-7 (breast carcinoma) cell lines at concentrations of 5 µmol L-1 and 50 µmol L-1.

RESULTS

At 50 µmol L-1, more than 70% inhibition of cell growth was achieved with compounds 2e, 2g against HCT 116, and 2b, 2d, 2e, 2f and 2g against MCF-7.

CONCLUSION

The obtained compounds showed only moderate cytotoxic activity. However, the products with substituents occupying the meta position in relation to the triazole ring showed increased cytotoxic properties. The brominated compound (2g) showed the strongest activity, inhibiting cell proliferation by 87%.

Pradimicin-IRD exhibits antineoplastic effects by inducing DNA damage in colon cancer cells

DNA-damaging agents are widely used in cancer therapy; however, their use is limited by dose-related toxicities, as well as the development of drug resistance. Drug discovery is essential to overcome these limitations and offer novel therapeutic options. In a previous study by our research group, pradimicin-IRD-a new polycyclic antibiotic produced by the actinobacteria Amycolatopsis sp.-displayed antimicrobial and potential anticancer activities. In the present study, cytotoxic activity was further confirmed in a panel of five colon cancer, including those with mutation in TP53 and KRAS, the most common ones observed in cancer colon patients. While all tested colon cancer cells were sensitive to pradimicin-IRD treatment with IC₅₀ in micromolar range, non-tumor fibroblasts were significantly less sensitive (p < 0.05). The cellular and molecular mechanism of action of pradimicin-IRD was then investigated in the colorectal cancer cell line HCT 116. Pradimicin-IRD presented antitumor effects occurring after at least 6 h of exposure. Pradimicin-IRD induced statistically significant DNA damage (γH2AX and p21), apoptosis (PARP1 and caspase 3 cleavage) and cell cycle arrest (reduced Rb phosphorylation, cyclin A and cyclin B expression) markers. In accordance with these results, pradimicin-IRD increased cell populations in the subG₁ and G₀/G₁ phases of the cell cycle. Additionally, mass spectrometry analysis indicated that pradimicin-IRD interacted with the DNA double strand. In summary, pradimicin-IRD exhibits multiple antineoplastic activities-including DNA damage, cell cycle arrest, reduction of clonal growth and apoptosis-in the HCT 116 cell line. Furthermore, pradimicin-IRD displays a TP53-independent regulation of p21 expression in HCT 116 TP53^-/-, HT-29, SW480, and Caco-2 cells. This exploratory study identified novel targets for pradimicin-IRD and provided insights for its potential anticancer activity as a DNA-damaging agent.

Oxidative functionalization of a halimane diterpenoid achieved by fungal transformation

Regio and stereoselective activation of sp³ CH bonds remain one of the major advantages of biocatalysis over traditional chemocatalytic methods. Herein, we describe the oxy-functionalization of halimane diterpenoid 1 by whole cells of three filamentous fungi, aiming to obtain derivatives with desirable biological properties. After incubating 1 with Fusarium oxysporum, Myrothecium verrucaria, and Rhinocladiella similis at different concentrations and incubation times, four known (3, 5, 6, and 7) and three new (2, 4, and 8) halimane derivatives were obtained and characterized. F. oxysporum catalyzed the hydroxylation of positions C-2 (2) and C-7 (4), while R. similis simultaneously mediated the 2-oxo-functionalization and the hydration of 13,14-(CC)double bond belonging to an α,β-unsaturated carbonyl system (8). Compounds 1-7 were non-cytotoxic against HCT-116 and MCF-7 cancer cell lines at tested concentrations. However, substrate 1 displayed moderate reduction ability against biofilm produced by Staphylococcus epidermidis ATCC35984 (84% at 1.6 mM), and this effect was retained to some extent by derivatives 4 and 7. These results emphasize the prominent potential of filamentous fungi associated with the microbiota of medicinal plants as versatile catalysts for singularly useful reactions through their complex enzymatic machinery, as well as the high susceptibility of halimane-diterpenoid substrates.