Natural and artificial bleomycins: chemistry and antitumor activities.

The bleomycins are a group of antibiotics produced by Streptomyces verticillus and their therapeutic effect against the squamous cell carcinoma has been proved by clinical studies. In our laboratory, eight products, viz. bleomycin A1, demethyl-A2, A-a, A-b, B2, A5 and B4 have been isolated in the pure state. Structures of the various bleomycins have been elucidated and it has been observed that they differ from each other in the amine moiety. The addition of an amine, especially diamines and triamines, during fermentation, induced the production of the bleomycin containing the amine added and suppressed the production of other bleomycins. Thus, 42 artificial bleomycins were synthesized and their biological activities studied. The selective effect against squamous cell carcinoma and the mechanism of the selective activity that was shown by an enzymatic inactivation will be discussed. A partial purification of the inactivating enzyme has been achieved. In the study started from phleomycin1'2 we found a group of antibiotics which were produced by Strepto,nyces verticillus and were differentiated from phleomycin by paper chromatography and stability in aqueous solution. Phleomycin caused irreversible renal damage but this antibiotic did not, and we named this antibiotic bleomycin3' '. Bleomycin has been confirmed to be effective against squamous cell carcinoma and it is used for treatment of this type of human cancer. Bleomycins which are obtained from the culture filtrate by cation exchange resin process, carbon chromatography and alumina chromatography are in their copper-chelated forms. Both the copper-chelated and the copper-free bleomycins are equally active and copper-free bleomycin mixture is used clinically. In the second paper, we reported bleomycins A1, A2, A3, A4, A5, A6, B1, B2, B3, B4 and B5. Later, we found demethyl-A2, A'-a, A'2-b, B'1 and B6. These bleomycins were separated by CM-Sephadex C-25 column chromatography raising the concentration of ammonium formate from 0.05M to 1.OM. An example of the chromatography is shown in Figure 1. All bleomycins have the maximum at 292 mt and the absorption of the eluate at this wavelength was determined. A1 and demethyl-A2 which appeared in peaks I and II respectively were separated by column chromatography of Dowex 50 resin treated with 02M pyridine acetate buffer at pH 4.4. The elution was carried out by raising the pH of the same buffer from pH 4.4 to 5.5. The separation of A-a and A-b, both of which appeared in the peak V, was accomplished by repetition of CM-Sephadex C-25 chromatography, raising the concentration of 665