USING RECOMBINANT DNA TECHNOLOGY AND SOLID-PHASE DEOXYRIBONUCLEOTIDE SYNTHESIS, A UNIQUE HYBRID GENE CONSISTING OF A FRAGMENT OF DIPTHERIA TOXIN AND THE SEQUENCEENCODING APLHA-MELANOCYTE-STIMULATING HORMONE (MSH) HAS BEENCONSTRUCTED AND EXPRESSED IN E.

USING RECOMBINANT DNA TECHNOLOGY AND SOLID-PHASE DEOXYRIBONUCLEOTIDE SYNTHESIS, A UNIQUE HYBRID GENE CONSISTING OF A FRAGMENT OF DIPTHERIA TOXIN AND THE SEQUENCEENCODING APLHA-MELANOCYTE-STIMULATING HORMONE (MSH) HAS BEENCONSTRUCTED AND EXPRESSED IN E. COLI K12. PRELIMINARY STUDIES OF THE CYTOTOXIC PROPERTIES OF THIS NOVEL POLYPEP- TIDE (MSH-TOXIN) ON HUMAN MALIGNANT MELANOMA CELLS DEMONSTRATE THAT THE CHIMERIC MOLECULE POSSESSES CHARACTERISTICS INTRINSIC TO THE DIPTHERIA TOXIN (ABILITY TOADP-RIBOSYLATE EF-2 AND BLOCK PROTEIN SYNTHESIS) AND TO MSH (SPECIFICITY FOR MSH-RECEPTOR BEARING CELLS). THE HYBRID TOXIN-GENE PRODUCT HAS BEEN LICENSED BY SERAGEN, INC. THE LONG-RANGE OBJECTIVE OF THIS PROJECT IS TO EVALUATE THE POTENTIAL OF MSH-TOXIN AS A SPECIFIC CHEMOTHERAPEUTIC FOR THE TREATMENT OF HUMAN MALIGNANT MELANOMA. PHASE I OF THE PROJECT WILL (1) COMPLETE ASSESSMENT OF THE MOLECULE'S RECEPTOR-SPECIFC CYTOTOXICITY FOR HUMAN CELL LINES OR PATIENT MATERIAL BEARING MSH-RECEPTORS; () ANALYZE BY DUAL BEAM FLOW CYTOMETRY, DISTRIBUTION OF THE MSH RECEPTOR AS A FUNCTION OF CELL CYCLE ON IN VITRO AND IN VIVO PASSAGED MELANOMA CELLS; AND (3) ESTABLISH A HUMAN MELANOMA XENO- TRANSPLANT MODEL IN THE NUDE MOUSE TO CHARACTERIZE IN VIVO EFFICACY OF PRIMARY TUMOR TREATMENT WIH MSH-TOXIN. PHASE II OF THE PROJECT WILL FOCUS ON (1) EFFICACY OF MSH-TOXIN INA METASTATIC NUDE MOUSE MODEL; (2) DEVELOPMENT OF A BIOASSAYFOR MSH-TOXIN; AND (3) ANIMAL TOXICOLOGY AND INVESTIGATION OF MSH-TOXIN FATE AND DISTRIBUTION IN VIVO, INCLUDING EVALUATION OF IMPACT ON IMMUNE AND RETICULOENDOTHELIAL SYSTEMS.