Chem. Rev. 2005, 105, 739−758 739 Antitumor Antibiotics: Bleomycin, Enediynes, and Mitomycin Ute Galm,† Martin H. Hager,† Steven G. Van Lanen,† Jianhua Ju,† Jon S. Thorson,*,† and Ben Shen*,†,‡ Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53705 Received July 19, 2004 Contents their clinical utilities and shortcomings, a comparison of resistance mechanisms within producing organ- 1. Introduction 739 isms to those predominant among tumor cells reveals 2. Bleomycin 739 remarkable potential for continued development of 2.1. Discovery and Biological Activities 739 these essential anticancer agents. 2.2. Clinical Resistance 740 2.2.1. Bleomycin Hydrolase 741 2. Bleomycin 2.2.2. Enhanced DNA Repair 742 2.2.3. Bleomycin Binding Protein 742 2.1. Discovery and Biological Activities 2.2.4. Other Mechanisms 743 The bleomycins (BLMs), such as bleomycinic acid 2.3. Resistance by the Producing Organisms 743 (1), BLM A2 (2), or BLM B2 (3), are a family of 2.3.1. Bleomycin N-Acetyltranferase (BlmB) 743 glycopeptide-derived antibiotics originally isolated 2.3.2. Bleomycin Binding Protein (BlmA) 743 from several Streptomyces species.2,3 Several struc- 2.3.3. Transport Proteins 744 ture variations of the naturally occurring BLMs have 3. EnediynessNine-Membered Enediyne Core 744 been identified from fermentation broths, primarily Subfamily differing at the C-terminus of the glycopeptide. The 3.1. Discovery and Biological Activities 745 BLM structure was revised in 19784 and confirmed 3.2. Resistance by the Producing Organisms 746 by total synthesis in 1982.5,6 Structurally and bio- 3.2.1. Apo-Protein 746 synthetically related to the BLMs are the phleomy- 7-10 3.2.2. DNA Repair 747 cins (PLMs), such as PLM 12 (4) or PLM D1 (5), 3.2.3. Transport 747 and tallysomycins (TLMs), such as TLM S2B(6) and TLM S B(7)11,12 (Figure 1). 4. EnediynessTen-Membered Enediyne Core 748 10 Subfamily BLMs are thought to exert their biological effects 4.1. Discovery and Biological Activities 748 through a sequence-selective, metal-dependent oxi- dative cleavage of DNA and RNA in the presence of 4.2. Clinical Resistance 750 - oxygen.13 16 The BLMs can be dissected into four 4.3. Resistance by the Producing Organisms 751 functional domains: (i) the pyrimidoblamic acid 5. Mitomycin 752 (PBA) subunit along with the adjacent â-hydroxyl 5.1. Discovery and Biological Activities 752 histidine constitutes the metal-binding domain that 5.2. Clinical Resistance 754 provides the coordination sites required for Fe(II) 5.3. Resistance by the Producing Organisms 754 complexation and molecular oxygen activation re- 6. Perspective 754 sponsible for DNA cleavage; (ii) the bithiazole and 7. Abbreviations 755 C-terminal amine provide the majority of the BLM- 8. Acknowledgment 755 DNA affinity and may contribute to polynucleotide 9. References 755 recognition and the DNA cleavage selectivity; (iii) the (2S,3S,4R)-4-amino-3-hydroxy-2-methylpentanoic acid (AHM) subunit not only provides the connectivity between the metal-binding and DNA-binding sites 1. Introduction but also plays an important role in the efficiency of Natural-product-derived cytotoxics remain a main- DNA cleavage by BLMs; (iv) the sugar moiety is stay in current chemotherapy.1 This review focuses likely to participate in cell recognition by BLMs and on the current level of understanding and emerging possibly in cellular uptake and metal-ion coordina- trends relevant to the DNA-damaging metabolite tion. Consequently, there have been continuing at- families of the bleomycins, 9- and 10-membered tempts to develop new BLM congeners to define the enediynes, and mitomycins. Within the context of fundamental functional roles of the individual do- mains and search for anticancer drugs with better * To whom correspondence should be addressed. J.S.T.: phone, clinical efficacy and lower toxicity. However, the 608-262-3829; fax, 608-262-5345; e-mail, jsthorson@ structural complexity of BLMs has limited most of pharmacy.wisc.edu. B.S.: phone, (608) 263-2673; fax, (608) 262- the modifications at either the C-terminal amine or 5345.; e-mail, [email protected]. † Division of Pharmaceutical Sciences. the N-terminal â-aminoalaninamide moiety by either ‡ Department of Chemistry. directed biosynthesis or semisynthesis. Total chemi- 10.1021/cr030117g CCC: $53.50 © 2005 American Chemical Society Published on Web 01/21/2005 740 Chemical Reviews, 2005, Vol. 105, No. 2 Galm et al. Ute Galm studied pharmacy at the University of Tuebingen, Germany. In Steven G. Van Lanen received his B.S. (1998) degree in Molecular Biology 2003 she finished her doctoral research on aminocoumarin antibiotics from the University of WisconsinsMadison. In 2003 he received his Ph.D. under Professor Lutz Heide and received her Ph.D. degree from the degree in Chemistry at Portland State University under the guidance of University of Tuebingen. She was appointed as a postdoctoral associate Professor Dirk Iwata-Reuyl. He currently is a postdoctoral fellow in the at the University of WisconsinsMadison in 2004, where she works with laboratory of Professor Ben Shen, studying the biosynthesis of C-1027 Professor Ben Shen. Her current research interests are focused on and other enediyne natural products. biosynthetic studies of the bleomycin family of compounds in different Streptomyces strains. Jianhua Ju was born in 1972 in Shandong, China. He received his B.S. degree in Pharmacy from Shandong University in 1995 and obtained his Martin Hager, born in 1972 in Muenster, Germany, began his studies in Ph.D. degree in Medicinal and Natural Product Chemistry at Peking Union Biology in 1993 at the University of Tuebingen. He received his diploma Medical College in 2000. Then he worked as a faculty member at the in 1998 and his Ph.D. degree in 2002 with Professor Ralph Bock at the Institute of Medicinal Plant Development, Chinese Academy of Medical University of Freiburg for his work on the functional analyses of open Sciences in Beijing, where he was engaged in new natural products reading frames by reverse genetics. He then joined the laboratory of discovery research. He received the Servier Young Investigator Award in Professor Albrecht E. Sippel to investigate EGF-receptor inhibitors and Medicinal Chemistry in 2002 issued by the Chinese Pharmaceutical new approaches to tumor targeting by exploiting antibody avidity. In 2003 Association & Institut de Recherches Internatinales Servier. In 2003 he he joined the laboratory of Professor Jon S. Thorson. His current research joined the research group of Professor Ben Shen as a postdoctoral objective is the directed evolution of glycosyltransferases and structural research associate at the School of Pharmacy, University of Wisconsins analysis of resistance proteins. Martin Hager is a postdoctoral fellow of Madison working in the field of natural product biosynthesis. the German Academy of Scientists Leopoldina. He also received grants from the German Research Foundation and the German Ministry of Education and Research. do not cause myelosuppression, promoting its wide application in combination chemotherapy. Early de- cal synthesis of BLMs is expensive, thus limiting the velopment of drug resistance and cumulative pulmo- practicality in pharmaceutical applications. While nary toxicity are the major limitations of BLMs in numerous BLM analogues have been synthesized in chemotherapy.18 the past two decades, none has improved proper- ties.13,14,17 Therefore, the development of methods to 2.2. Clinical Resistance manufacture novel BLMs, particularly those unavail- able or extremely difficult to prepare by chemical Thus far there is no proof of a mechanism that synthesis, remains an important research goal. explains the development of BLM resistance in some BLMs exhibit strong antitumor activity and are tumor cells, although alteration of drug uptake and currently used clinically in combination with a num- efflux, enhanced repair of BLM-induced DNA lesions, ber of other agents for the treatment of several types and increased inactivation of BLM might be possible of tumors, notably squamous cell carcinomas and mechanisms.19-24 Several pathogenic microorganisms malignant lymphomas.13,14,18 The commercial prod- have been found to exhibit BLM resistance, seem- uct, Blenoxane, contains 2 and 3 as the principal ingly caused by the existence of a BLM-binding constituents. Unique to most anticancer drugs, BLMs protein in the respective organisms.25-28 Antitumor Antibiotics Chemical Reviews, 2005, Vol. 105, No. 2 741 Jon Thorson received his B.A. degree in Chemistry (1986) from Augsburg Ben Shen received his B.S. degree from Hangzhou University (1982), College and his Ph.D. degree in Organic Chemistry (1993) from the M.S. degree from the Chinese Academy of Sciences (1984), and Ph.D. University of Minnesota with Professor Hung-wen (Ben) Liu. He held a degree from Oregon State University (1991, with Professor Steven J. postdoctoral appointment as a Merck Postdoctoral Fellow of the Helen Gould) and carried out postdoctoral research in Professor C. Richard Hay Whitney Foundation (1993−1996) at the University of California, Hutchinson’s laboratory at the University of WisconsinsMadison (1991− Berkeley, with Professor Peter Schultz. From 1996 to 2001 Jon held 1995). He started his independent career at the Department of Chemistry, appointments as an assistant member of the Memorial Sloan-Kettering University of California, Davis, in 1995 and moved to the University of Cancer Center