MELASTIN, A NOVEL PRODUCT OF STREPTOMYCES THAT SELECTIVELY INHIBITS LEUKEMIA-CELL GROWTH

In the course of our screening for new immunomodulators, a novel compo und, melastin, was purified from the culture broth of Streptomyces. Me lastin was purified through adsorption to Diaion HP-20, ethanol precip itation, and anion exchange column as a brown powder. The molecular we ight was estimated as 5000 +/- 3000 by gel filtration HPLC. Melastin s uppressed lipopolysaccharide (LPS)-induced blastogenesis of B cells mo re profoundly than concanavalin A (con A)- or phytohemagglutinin (PHA) -induced blastogenesis of T cells. Moreover, it selectively inhibited the growth of several leukemia cells as compared with interleukin-depe ndent nontransformed leukocytes. No selectivity was observed between n ontransformed fibroblasts and their oncogene-transformed variants. Mel astin did not selectively inhibit macromolecule synthesis of leukemia cells.