EGCG Disrupts the LIN28B/Let-7 Interaction and Reduces Neuroblastoma Aggressiveness

Neuroblastoma (NB) is the most commonly diagnosed extracranial solid tumor in children, accounting for 15% of all childhood cancer deaths. Although the 5-year survival rate of patients with a high-risk disease has increased in recent decades, NB remains a challenge in pediatric oncology, and the identification of novel potential therapeutic targets and agents is an urgent clinical need. The RNA-binding protein LIN28B has been identified as an oncogene in NB and is associated with a poor prognosis. Given that LIN28B acts by negatively regulating the biogenesis of the tumor suppressor let-7 miRNAs, we reasoned that selective interference with the LIN28B/let-7 miRNA interaction would increase let-7 miRNA levels, ultimately leading to reduced NB aggressiveness. Here, we selected (−)-epigallocatechin 3-gallate (EGCG) out of 4959 molecules screened as the molecule with the best inhibitory activity on LIN28B/let-7 miRNA interaction and showed that treatment with PLC/PLGA-PEG nanoparticles containing EGCG (EGCG-NPs) led to an increase in mature let-7 miRNAs and a consequent inhibition of NB cell growth. In addition, EGCG-NP pretreatment reduced the tumorigenic potential of NB cells in vivo. These experiments suggest that the LIN28B/let-7 miRNA axis is a good therapeutic target in NB and that EGCG, which can interfere with this interaction, deserves further preclinical evaluation

Inhibition of mitochondrial translation as a novel strategy to eradicate glioblastoma stem cells

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults. The search for new effective chemotherapeutic agents to treat GBM has proven challenging throughout the last few decades. As a result, very limited pharmacological treatment is currently available. GBM aggressiveness is associated with its glioblastoma stem cells (GSCs) component, which is responsible for resistance to therapy. Therefore, new specific pharmacological approaches directed to eradicate GSCs are endowed with a great therapeutic potential. GSCs have been shown to rely on mitochondrial respiration for their high energy demand. In order to have a functional mitochondrial respiration process, the five complexes forming the oxidative phosphorylation (OXPHOS) chain have to be built by the coordinate assembly of proteins translated by either the cytosolic or the mitochondrial ribosomes. Given their endosymbiotic origin and despite the evolutionary changes occurred the mitochondrial ribosomes (mitoribosomes) still share structural and functional similarities with the bacterial ones, particularly considering the functional ribosomal core. In the light of these similarities, we hypothesized that antibiotics targeting bacterial ribosomes could be exploited to inhibit mitoribosomes, affecting mitochondrial translation and OXPHOS assembly, and hence leading to detrimental effect on GSCs viability. We performed a high-content imaging driven screening of several bacterial ribosome targeting antibiotics and identified Drug A as the most promising compound due to its cytotoxic and mitotoxic effects on GSCs. We demonstrated that Drug A effectively prevents GSCs expansion, resulting to be over an order of magnitude more effective in GSCs growth inhibition than temozolomide, the only drug used in first line GBM therapy. We then investigated the mechanism of action of Drug A, proving that it inhibits mitochondrial translation and, as a consequence, it decreases the functionality of the OXPHOS complexes reducing mitochondrial respiration capacity. Moreover, we obtained the structure of this compound bound to the human mitoribosome using cryo-electron microscopy, which provides the basis for further development of more potent analogs. Finally we proved the efficacy of Drug A in vivo using a xenograft mouse model of GBM. Our results suggest that mitochondrial translation represents a therapeutic target for GBM and show that Drug A, acting via inhibition of mitochondrial translation, is extremely effective against GSCs. Given the urgent medical need for novel therapeutic approaches in GBM treatment, Drug A represents a promising therapeutic solution that is worth further preclinical and clinical investigations

Hybrid Molecules Containing Naphthoquinone and Quinolinedione Scaffolds as Antineoplastic Agents

In recent decades, molecular hybridization has proven to be an efficient tool for obtaining new synthetic molecules to treat different diseases. Based on the core idea of covalently combining at least two pharmacophore fragments present in different drugs and/or bioactive molecules, the new hybrids have shown advantages when compared with the compounds of origin. Hybridization could be successfully applied to anticancer drug discovery, where efforts are underway to develop novel therapeutics which are safer and more effective than those currently in use. Molecules presenting naphthoquinone moieties are involved in redox processes and in other molecular mechanisms affecting cancer cells. Naphthoquinones have been shown to inhibit cancer cell growth and are considered privileged structures and useful templates in the design of hybrids. The present work aims at summarizing the current knowledge on antitumor hybrids built using 1,4- and 1,2-naphthoquinone (present in natural compounds as lawsone, napabucasin, plumbagin, lapachol, α-lapachone, and β -lapachone), and the related quinolone- and isoquinolinedione scaffolds reported in the literature up to 2021. In detail, the design and synthetic approaches adopted to produce the reported compounds are highlighted, the structural fragments considered in hybridization and their biological activities are described, and the structure–activity relationships and the computational analyses applied are underlined

Enhanced Production and Quantitative Evaluation of Nigericin from the Algerian Soil-Living Streptomyces youssoufiensis SF10 Strain

Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated from a semi-arid soil sample collected at Chélia Mountain, in Khenchela (Northeastern Algeria) and identified as Streptomyces youssoufiensis. The extracts from the strain, cultured in a solid state or submerged fermentation conditions, using several carbon sources at different pH values, in the presence or absence of iron (II) sulfate and in co-culture with other Streptomyces species, were analyzed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). The best culture conditions provided a concentration of nigericin of 0.490 ± 0.001 mg/mL in the extract. The HPLC-ELSD method, optimized here for the quantitative detection of nigericin, can find wider applications in the analysis of several other metabolites characterized by a similar polycyclic polyether structure or, more generally, by the lack of significant chromophores in their molecular structure

Synthesis of 2,6-Diamino-Substituted Purine Derivatives and Evaluation of Cell Cycle Arrest in Breast and Colorectal Cancer Cells

Reversine is a potent antitumor 2,6-diamino-substituted purine acting as an Aurora kinases inhibitor and interfering with cancer cell cycle progression. In this study we describe three reversine-related molecules, designed by docking calculation, that present structural modifications in the diamino units at positions 2 and 6. We investigated the conformations of the most stable prototropic tautomers of one of these molecules, the N6-cyclohexyl-N6-methyl-N2-phenyl-7H-purine-2,6-diamine (3), by Density Functional Theory (DFT) calculation in the gas phase, water and chloroform, the last solvent considered to give insights into the detection of broad signals in NMR analysis. In all cases the HN(9) tautomer resulted more stable than the HN(7) form, but the most stable conformations changed in different solvents. Molecules 1–3 were evaluated on MCF-7 breast and HCT116 colorectal cancer cell lines showing that, while being less cytotoxic than reversine, they still caused cell cycle arrest in G2/M phase and polyploidy. Unlike reversine, which produced a pronounced cell cycle arrest in G2/M phase in all the cell lines used, similar concentrations of 1–3 were effective only in cells where p53 was deleted or down-regulated. Therefore, our findings support a potential selective role of these structurally simplified, reversine-related molecules in p53-defective cancer cells

Inhibition of mitochondrial translation suppresses glioblastoma stem cell growth

International audienceGlioblastoma stem cells (GSCs) resist current glioblastoma (GBM) therapies. GSCs rely highly on oxidative phosphorylation (OXPHOS), whose function requires mitochondrial translation. Here we explore the therapeutic potential of targeting mitochondrial translation and report the results of high-content screening with putative blockers of mitochondrial ribosomes. We identify the bacterial antibiotic quinupristin/dalfopristin (Q/D) as an effective suppressor of GSC growth. Q/D also decreases the clonogenicity of GSCs in vitro, consequently dysregulating the cell cycle and inducing apoptosis. Cryoelectron microscopy (cryo-EM) reveals that Q/D binds to the large mitoribosomal subunit, inhibiting mitochondrial protein synthesis and functionally dysregulating OXPHOS complexes. These data suggest that targeting mitochondrial translation could be explored to therapeutically suppress GSC growth in GBM and that Q/D could potentially be repurposed for cancer treatment