Epiderstain, a new inhibitor of the mitogenic activity induced by epidermal growth factor. I. Taxonomy, fermentation, isolation and characterization.

Inhibitors of mitogenic activity induced by epidermal growth factor (EGF) were screened from culture broths of soil microorganisms.A strain of actinomycetes has been found to produce a new glutarimide antibiotic namedepiderstatin which inhibits the incorporation of [3H]thymidine into quiescent animal cells stimulated by EGF.Taxonomicstudies have revealed that the producing strain belongs to a subspecies of Streptomyces pulveraceus, thus the name, Streptomyces pulveraceus subsp.epiderstagenes was given to this strain.The molecular formula (C15H20N2O4)and UVprofile (Amax 295 nm) of the antibiotic are distinct from other known antibiotics.It inhibited the incorporation of [3H]thymidine into quiescent cells stronger than into growing cells.1599 Recently, there have been a number of arguments concerning the relationship between growth factors and oncogenesis1'2*.Specific inhibitors of growth factors should be useful to elucidate the mechanism of action and relationship between growth factors and oncogenesis.In addition, they are expected to have a new type of antitumor activity.We have chosen epidermal growth factor (EGF) as a screening target, because EGF is one of the best characterized growth factors3).EGF is a homologous protein to transforming growth factor alpha (TGF-a) and both growth factors share the same receptor40.Therefore, the inhibitor of EGFis expected as a growth inhibitor of tumor cells.During the screening, we found that a new inhibitor named epiderstatin was produced by a streptomycete, strain RK-441.Taxonomy, fermentation of the producing strain and isolation, physico-chemical properties, and biological activity of epiderstatin are described in this paper. Materials and Methods Taxonomic StudiesMethods and media recommendedby International Streptomyces Project (ISP)5) were used to examine the taxonomic characterization of strain RK-441.Morphologyon ISP media was observed after incubation at 28°C for 14 days.The Color Harmony Manual (4th Ed., 1958, Container Corporation of America, Chicago, Illinois) was used to identify the color of mycelial and soluble pigments.A scanning electron microscope (SEM) was used to study morphology of the spore chains.Whole-cell sugars were identified by the method of Lechevalier and Lechevalier6) and diaminopinielic acid (DAP) isomers were analyzed by the method of Becker et al?).Bacterial Strain The strain RK-441 has been deposited at the Fermentation Research Institute, Agency of Industrial Science and Technology, Japan, under the accession No. FERM-P10306.Streptomyces bobili JCM4012 and JCM4627 were obtained from Japan Collection of^Microorganisms (JCM), RIKENInstitute, and Streptomyces pulveraceus IFO 3855 and IFO 3857 from Institute for Fermentation, Osaka (IFO).