Anti-glioblastoma activity of monensin and its analogs in an organoid model of cancer

Glioblastoma (GBM) remains the most frequently diagnosed primary malignant brain cancer in adults. Despite recent progress in understanding the biology of GBM, the clinical outcome for patients remains poor, with a median survival of approximately one year after diagnosis. One factor contributing to failure in clinical trials is the fact that traditional models used in GBM drug discovery poorly recapitulate patient tumors. Previous studies have shown that monensin (MON) analogs, namely esters and amides on C-26 were potent towards various types of cancer cell lines. In the present study we have investigated the activity of these molecules in GBM organoids, as well as in a host:tumor organoid model. Using a mini-ring cell viability assay we have identified seven analogs (IC₅₀ = 91.5 ± 54.4–291.7 ± 68.8 nM) more potent than parent MON (IC₅₀ = 612.6 ± 184.4 nM). Five of these compounds induced substantial DNA fragmentation in GBM organoids, suggestive of apoptotic cell death. The most active analog, compound 1, significantly reduced GBM cell migration, induced PARP degradation, diminished phosphorylation of STAT3, Akt and GSK3β, increased ɣH2AX signaling and upregulated expression of the autophagy associated marker LC3-II. To investigate the activity of MON and compound 1 in a tumor microenvironment, we developed human cerebral organoids (COs) from human induced pluripotent stem cells (iPSCs). The COs showed features of early developing brain such as multiple neural rosettes with a proliferative zone of neural stem cells (Nestin+), neurons (TUJ1 +), primitive ventricular system (SOX2 +/Ki67 +), intermediate zone (TBR2 +) and cortical plate (MAP2 +). In order to generate host:tumor organoids, we co-cultured RFP-labeled U87MG cells with fully formed COs. Compound 1 and MON reduced U87MG tumor size in the COs after four days of treatment and induced a significant reduction of PARP expression. These findings highlight the therapeutic potential of MON analogs towards GBM and support the application of organoid models in anti-cancer drug discovery.

Synthesis and evaluation of antibacterial and trypanocidal activity of derivatives of monensin A

The synthesis and biological evaluation of eleven derivatives of the natural polyether ionophore monensin A (MON), modified at the C-26 position, is presented. Eight urethane and three ester derivatives were tested for their antimicrobial activity against different strains of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa. In addition, their antiparasitic activity was also evaluated with bloodstream forms of Trypanosoma brucei. The majority of the modified ionophores were active against a variety of Gram-positive bacterial strains, including methicillin-resistant S. epidermidis, and showed better antibacterial activity than the unmodified MON. The phenyl urethane derivative of MON exhibited the most promising antibacterial activity of all tested compounds, with minimal inhibitory concentration values of 0.25-0.50 μg/ml. In contrast, none of the MON derivatives displayed higher antitrypanosomal activity than the unmodified ionophore.

Antiproliferative activity of ester derivatives of monensin A at the C-1 and C-26 positions

Monensin A (MON) is a polyether ionophore antibiotic, which shows a wide spectrum of biological activity, including anticancer activity. A series of structurally diverse monensin esters including its C-1 esters (1-9), C-26-O-acetylated derivatives (10-15), and lactone (16) was synthesized and for the first time evaluated for their antiproliferative activity against four human cancer cell lines with different drug-sensitivity level. All of the MON derivatives exhibited in vitro antiproliferative activity against cancer cells at micromolar concentrations. The majority of the compounds was able to overcome the drug resistance of LoVo/DX and MES-SA/DX5 cell lines. The most active compounds proved to be MON C-26-O-acetylated derivatives (10-15) which exhibited very good resistance index and high selectivity index.

Titania-Supported Catalysts for Levulinic Acid Hydrogenation: Influence of Support and its Impact on γ-Valerolactone Yield

A series of titania-supported ruthenium and platinum catalysts was investigated in the levulinic acid hydrogenation towards γ-valerolactone, a key reaction for the catalytic transformation of biomass. It was shown that various morphologies and phases of titania strongly influence the physicochemical and catalytic properties of supported Ru and Pt catalysts in different ways. In the case of the catalyst supported on mixed TiO2 phases, Ru particles are exclusively located on the minority rutile crystallites, whereas such an effect was not observed for platinum. The platinum catalyst activity could be increased when the metal was dispersed on the large surface-area anatase, which was not the case for ruthenium as a result of its agglomeration on this support. The activity of ruthenium on anatase could be increased in two ways: a) when RuO2 formation during catalyst preparation was avoided; b) when pure anatase support material was modified so that it exhibited no microporosity. The obtained results allow a better understanding of the role of the support for Ru and Pt catalysts.