Sonoko Atsumi

Inhibition of glucocerebrosidase and induction of neural abnormality by cyclophellitol in mice

Cyclophellitol, a cyclitol with an epoxide, is a novel microbial secondary metabolite that inhibits beta-glucosidase and beta-glucocerebrosidase. Daily administration of cyclophellitol induces a severe abnormality of the nervous system in mice while it has no toxicity in various cultured cells. It was shown to inhibit glucocerebrosidase in vivo significantly in mice and the content of glucocerebroside in liver, spleen, and brain was increased markedly. The enzyme activity was completely suppressed in brain, liver, spleen, kidney, and muscle. On the other hand hexosaminidase activity was not affected in all tissues. After a single administration of cyclophellitol the maximal inhibition of glucocerebrosidase was observed within 30 min in brain and liver, and the inhibition lasted for 2-4 days. A single administration of cyclophellitol also induced a severe abnormality of the nervous system known as Gauchers-like disease in mice. Conduritol B epoxide is also known to inhibit glucocerebrosidase and induce Gauchers like-disease in mice by repetitive injection. Cyclophellitol was shown to be more potent than conduritol B epoxide in inhibition of glucocerebrosidase and in induction of the neural abnormality.

Enhancement of fibronectin expression by herbimycin A

Herbimycin A specifically inrreased the level of fibronectin mRNA in Rous sarcoma virus-infected rat kidney cells, and the time course of fibronectin expression was found to be closely related to that of morphological change induced by herbimycin A.

New anti-cancer chemicals Ertredin and its derivatives, regulate oxidative phosphorylation and glycolysis and suppress sphere formation in vitro and tumor growth in EGFRvIII-transformed cells.

BackgroundEGFRvIII is a mutant form of the epidermal growth factor receptor gene (EGFR) that lacks exons 2–7. The resulting protein does not bind to ligands and is constitutively activated. The expression of EGFRvIII is likely confined to various types of cancer, particularly glioblastomas. Although an anti-EGFRvIII vaccine is of great interest, low-molecular-weight substances are needed to obtain better therapeutic efficacy. Thus, the purpose of this study is to identify low molecular weight substances that can suppress EGFRvIII-dependent transformation.MethodsWe constructed a new throughput screening system and searched for substances that decreased cell survival of NIH3T3/EGFRvIII spheres under 3-dimensional (3D)-culture conditions, but retained normal NIH3T3 cell growth under 2D-culture conditions. In vivo activity was examined using a mouse transplantation model, and derivatives were chemically synthesized. Functional characterization of the candidate molecules was investigated using an EGFR kinase assay, immunoprecipitation, western blotting, microarray analysis, quantitative polymerase chain reaction analysis, and measurement of lactate and ATP synthesis.ResultsIn the course of screening 30,000 substances, a reagent, “Ertredin” was found to inhibit anchorage-independent 3D growth of sphere-forming cells transfected with EGFRvIII cDNA. Ertredin also inhibited sphere formation in cells expressing wild-type EGFR in the presence of EGF. However, it did not affect anchorage-dependent 2D growth of parental NIH3T3 cells. The 3D-growth-inhibitory activity of some derivatives, including those with new structures, was similar to Ertredin. Furthermore, we demonstrated that Ertredin suppressed tumor growth in an allograft transplantation mouse model injected with EGFRvIII- or wild-type EGFR-expressing cells; a clear toxicity to host animals was not observed. Functional characterization of Ertredin in cells expressing EGFRvIII indicated that it stimulated EGFRvIII ubiquitination, suppressed both oxidative phosphorylation and glycolysis under 3D conditions, and promoted cell apoptosis.ConclusionWe developed a high throughput screening method based on anchorage-independent sphere formation induced by EGFRvIII-dependent transformation. In the course of screening, we identified Ertredin, which inhibited anchorage-independent 3D growth and tumor formation in nude mice. Functional analysis suggests that Ertredin suppresses both mitochondrial oxidative phosphorylation and cytosolic glycolysis in addition to promoting EGFRvIII degradation, and stimulates apoptosis in sphere-forming, EGFRvIII-overexpressing cells.

Novel approaches for identification of anti-tumor drugs and new bioactive compounds

Thanks to the pioneering work done by Professor Hamao Umezawa, bioactive compounds have been used in treatment of several diseases including cancer. In this review, we discuss our work, which focuses on developing new candidates for anti-tumor drugs by screening for bioactive natural compounds in microbial cultures using unique experimental systems. We summarize our recent progress including the following: (1) small-molecule modulators of tumor–stromal cell interactions, (2) inhibitors of three-dimensional spheroid formation of cancer cells, (3) multi-cancer cell panel screening and (4) new experimental animal models for cancer metastasis.

Vegfrecine, an inhibitor of VEGF receptor tyrosine kinases isolated from the culture broth of Streptomyces sp.

A new inhibitor of VEGF receptor tyrosine kinases, vegfrecine (1), was isolated from the culture broth of Streptomyces sp. MK931-CF8. The molecular structure of 1 was determined by NMR and MS analysis combined with synthesis. Compound 1 showed potent inhibitory activity against vascular endothelial growth factor receptor (VEGFR) tyrosine kinases in in vitro enzyme assays, but platelet-derived growth factor receptors (PDGFRs), fibroblast growth factor receptor (FGFR), and epidermal growth factor receptor (EGFR) responded only weakly. Compound 1 is a promising new selective VEGFR inhibitor for investigating new treatments of cancer and inflammatory diseases.

Microbial metabolites and derivatives targeted at inflammation and bone diseases therapy: chemistry, biological activity and pharmacology

Microbial metabolites have attracted increasing interest as a source of therapeutics and as probes for biological mechanisms. New microbial metabolites and derivatives targeted at inflammation and bone disease therapy have been identified by focusing on prostaglandin release, osteoblast differentiation and immune cell functions. These modulators of inflammatory processes and bone disease contribute to our understanding of biological mechanisms and support identification of the therapeutic potential of drug lead candidates. The present review describes recent advances in the chemistry and analysis of inhibitors of prostaglandin release or other functional molecules of immune cells, as well as inducers of osteoblast differentiation, including biological and pharmacological activities.