Biochemical studies on cell growth stimulating substances of low molecular weight produced by microorganisms

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None proteinous microbial metabolites with low molecular weight are expected to be useful for studying cell growth mechanisms as well as for reducing production cost of proteins such as growth factors and hormones produced by animal cells. Our screening for such compounds resulted in isolation of four unique metabolites; lavanducyanin from Streptomyces aeriouvifer, exfoliazone from Streptomyces exfoliatus, resorcinin from a gliding bacterium, Cytophaga johnsonae and misakimycin from Streptomyces misakiensis. All of these metabolites were lipophilic and purified by solvent extraction followed by appropriate chromatographies. Their structures were determined mainly based on NMR spectral analysis to be as follows; lavanducyanin, a phenazine derivative with an alkyl substituent; exfoliazone, a substituted phenoxazinone; resorcinin, 2-isoundecy1-5-isohexyl-resorcinol; misakimycin, 5-hydroxy-2,7-dimethoxy-6-methyl-1,4-naphthoquinone.These derivatives showed strong growth promoting activities to some kind of animal cell lines at lower serum concentrations. However, no effect was observed under serum-free conditions. Their activities were analyzed by MTT assay and by the increases of cell number and DNA synthesis, and their effective doses were determined at the range of nanogram to microgram/ml.Since the growth stimulating effect were observed with same kinds of cell lines including RLN-8, NIH 3T3 and T601, their action mechanisms seem to be identical. Since the famous tumor promoter TPA was inactive under the same condition, the action mechanisms of the compounds isolated by this work are concluded to be different from that of TPA.