This proposal is a continuation of our investigative activities desinged to explore and develop the field of microbial transformations for application to the study of antineoplastic agents. Our attention is focused primarily on highly active antitumor compounds from nature, and microorganisms will be used to accomplish selective chemical changes in the structures of such compounds under the mild reaction conditions obtainable in fermentations. Where appropriate, derivatives of microbial metabolites will be prepared and tested in suitable tumor test systems. Microbial transformations of natural antitumor agents will continue to be developed as a general means for: a) preparing quantities of potentially active metabolites; b) providing difficult-to-synthesize drug metabolites, the availability of which will facilitate drug metabolism studies in animals and man; c) elucidating new and potentially important pathways of metabolism of structurally complicated antitumor compounds; and d) establishing a working basis for further structure activity relationship studies on complex biologically-active compounds from nature. Specific experiments will be continued and pursued with the Vinca alkaloids including leurosine, vindoline, cataranthine and others; harringtonine alkaloids; selected diterpenes; podophyllotoxin and its derivatives; selected quassinoids; and other alkaloids. Growing cultures, resting cells, and isolated enzymes will be used to prepare metabolites whose structures will be determined by chemical and spectral methods. All metabolites will be submitted for antitumor evaluation. We will continue to elaborate enzymatic methods by which metabolites are formed by working with appropriate biochemical systems. In vitro mammalian metabolism studies have been initiated using available microbial metabolites as analytical standards for possible mammalian metabolites in an extension of our concept of Microbial Models for Mammalian Drug Metabolism.