A group of antibiotics produced by a strain of Streptomyces verticillus was named bleomycin, by Umezawa, Maeda, Takeuchi and Okami1) and it was differentiated from phleomycin2l by the stability on acid and alkaline reactions. By these authors, bleomycin was separated into bleomycins A and B. As reported in another paper by Umezawa, Suhara, Takita and Maeda8), bleomycins A and B were purified in their forms chelated with cupric ion by alumina chromatography, and a gradient chromatography on CM-Sephadex C-25. Each bleomycin thus purified was designated Cu-At 1, Cu-At 2, Cu-At 3, Cu-At 4, CuAt 5, Cu-At 6, Cu-Bt 1, Cu-Bt 2, Cu-Bt 3, Cu-Bt 4 and Cu-Bt 5. All bleomycins except Cu-Bt 2 and Cu-Bt 5 were differentiated from all phleomycins. After separation of bleomycin A into each component, the therapeutic index of each bleomycin was not higher than bleomycin A complex which was obtained by a cation resin process and Sephadex G-25 chromatography without addition of cupric ion, and therefore, such designations, Cu-At 1, Cu-At 2, etc., Cu indicating a form chelated with added cupric ion, A indicating bleomycin A, t indicating toxicity were employed. The same designations such as Cu-Bt 1, etc. were applied also to B. The toxicity, the absorption, the excretion, the distribution among organs and the antitumor effect in detail, were studied on bleomycin A complex and each of bleomycins Cu-At and Cu-Bt was studied on the antitumor and the antibacterial activities. These results are presented in this paper.
Though sporadic clinical accounts are available on the effect of some of the antibiotics as chloramphenicol on the liver, little work has been advanced on their action on liver regeneration in partially hepatectomized animals, a rather sensitive criterion for delineating hepatic alterations. Garattini et al1). reported an inhibition of liver regeneration over a period of 48~144 hours in mice and rats administered actinomycin D at 16~24 mcg/kg; no definite changes were discerned in the liver and blood lipids and proteins of such animals. The dosage was in the range of that which inhibited tumor growth or provoked a leukopenia. More recently, electron microscopic and enzymatic data have been presented for regenerating liver of animals treated with the latter antibiotic2, 3). An inhibitory effect on regeneration has also been reported for actinomycin C4). According to Calet5), chlortetracycline depresses liver regeneration in adult rats and chickens although body weight increases occur, findings which could not be attributed to greater proteinogenesis. The rats received a basic diet with the antibiotic at 100 mg/kg and were sarcificed on the fourth day. Calet also reported elevation in weight and a decrease in DNA with very low levels in intact rats.
In the present study, a number of antibiotics up to very high levels were screened as to their effect on liver regeneration in operated rats over an interval of 10.5 days. The antibacterial agents, sulfanilamide and the sodium salt of p-aminosalicylic acid (PAS) were also investigated.
Although surgical operations and radiotherapy are still playing important roles in the treatment of malignant tumors, the chemotherapy has also made a remarkable progress. As is generally known, a number of antitumor substances have been published, and establishments of better screening methods are expected in future. The present authors have carried out the fundamental investigations on antitumor substances for more than ten years, and recognized that the suitability of screening method is an important key especially for the discovery of new antitumor substance.
In the primary screening using Ehrlich ascites carcinoma, the present authors found that the culture broth of a new Streptomyces, S. phaeoverticillatus, isolated from a soil sample collected in Ehime Prefecture in 19592), prolonged the lives of tumor-bearing mice more than one month, whereas all the untreated mice died within 3 weeks. The active agents extracted and purified from the culture broth were named iyomycin complex, A, B1, B2, B3, B4, and B5. Among these agents, complex and B1 were studied in detail on their anticancer activities on various transplantable tumors, as reported in the present paper. A part of the experimental results was reported at the International Congress of Chemotherapy, in Stuttgart, Germany, in 1963.
Mikamycin1), an antibiotic complex, consists of mikamycins A and B which are quite different in chemical structure each other. Mikamycin A has been demonstrated to possess a N-containing macrolide-like structure which is similar to ostreogrycin A2), PA 114 A and staphylomycin M1. In contrast, mikamycin B3, 4) is a cyclic peptidic lactone probably identical with ostreogrycin B5), PA 114 B6) and vernamycin Bα7). At appropriate combinations of mikamycins A and B a marked synergism was observed in the inhibitory effect on the bacterial protein biosynthesis8) as well as in the bacteriostatic activity9.
In our earlier work with E. coli subcellular systems, it was demonstrated that mikamycin A strongly inhibited the poly U-directed polyphenylalanine synthesis from phenylalanyl-sRNA and that the mikamycin A inhibition was enhanced in the presence of mikamycin B which had no effect on the poly U-system10). Vazquez11, 12 reported that streptogramin and streptogramin A which are closely related with mikamycin and mikamycin A, respectively, significantly reduced the binding of 14C-chloramphenicol to ribosomes. It indicates that the site of action of the antibiotics of this group may be on the ribosomes. In the ribosomal phase of protein biosynthesis three steps of macromolecular interactions are now distinguished: the formation of messenger RNA-ribosome complex13, the binding of aminoacyl-sRNA to messenger RNA-ribosome complex14) and the transfer of carboxylactivated peptide from peptidyl-sRNA to incoming aminoacyl-sRNA with the formation of peptide bond15). It is, therefore, suggested that mikamycin A and probably mikamycin B interact with either of macromolecular components such as ribosome, enzyme, messenger and aminoacyl-sRNA required in these sequential reactions.
The present paper describes the results of the investigations carried out to examine the effects of each biopolymers on the mikamycin A inhibition of poly U-directing polyphenylalanine synthesis and the synergistic activity between mikamycins A and B in this poly U-system. Mikamycins activities were also examined systematically at various Mg++ concentrations, because the inhibitory or stimulatory effects of several antibiotics or chemical compounds on the subcellular polypeptide synthesis are known to be considerably dependent upon the Mg++ concentration used the ribosomal systems16~20).