Antitumour antibiotics and their producing microorganisms

Abstract

Antitumour antibiotics have been studied for more than 40 years. During this period, many types have been discovered and among these, actinomycin, mitomycin, bleomycin, adriamycin, neocarzinostatin, some antimetabolites and their derivatives have been used clinically. These antibiotics were purified from fermentation broth of microorganisms isolated from soil samples obtained on land. Recently, some antibiotics have been discovered from microorganisms isolated from soil samples, sponges, etc., in the sea. Thus, microorganisms have served as a rich source of novel drugs. About 66% of microorganisms producing antitumour antibiotics isolated in the I980s belong to the genus Streptomyces , followed by Act inornadu]a and M i c r o m o n o s p o r a (Table 1). Therefore, Strep tomyces is still the main producer of new antitumour antibiotics. In the discovery of new antibiotics, isolation of microorganisms and their fermentation, as well as screening methods are all important. New isolation procedures have been devised by many researchers, and they are still trying to develop techniques for isolation of useful strains of actinomycetes. Williams & Vickers (1988) discussed current and future approaches for the detection of actinomycetes in the natural environment. Nonomura & Hayakawa (1988) developed new methods for selective isolation of soil actinomycetes, i.e. pretreatment of samples with heat, chemical treatment, and use of selective isolation media. Weland & Helmke (1988) also reported actinomycetes in the marine environment. In a recent study of new antitumour antibiotics, substances exremely potent in vitro against a panel of human and mouse tumour cell lines were isolated from fermentation broth of actinomycetes and marine materials. The cytotoxic activities of these antibiotics differ in accordance with the experimental procedures; the ICs0 values are shown in Table 2. These new cytocidal