Kazusamycin A

CI-940, PD 114,721, and PD 118,607 are structurally novel antibiotics, which were isolated from fermentation beers of a previously unknown actinomycete. They are highly lipophilic acids characterized by unsaturated lactone and branched, polyunsaturated aliphatic side-chain moieties. All three agents demonstrated significant cytotoxic activity in vitro against a number of human and mouse tumor lines which encompassed a wide range of tissue types. CI-940 retained full activity in vitro against lines of P388 leukemia that are resistant to Adriamycin, amsacrine, and mitoxantrone. Activity was confirmed for both CI-940 and PD 114,721 against a number of murine experimental tumor systems in vivo, which included the P388 and L1210 leukemias and also B16 melanoma, Ridgway osteogenic and M5076 sarcomas, and mammary adenocarcinoma 16/C. PD 118,607 was also highly active against B16 melanoma. All three agents demonstrated anticancer activity at very low dosages compared with current clinically useful anticancer agents. No significant activity was seen against the MX-1 human mammary xenograft or pancreas 02 tumor models. The primary target for host toxicity of CI-940 and PD 114,721 appeared to be gastrointestinal in nature. Neither CI-940 nor PD 114,721 caused delayed lethality when given either IP or IV. In schedule studies, the toxicities of both CI-940 and PD 114,721 were moderately dependent on the regimen used, with total maximum tolerated dosages for intermittent (q4dx2), daily (qdx5), and divided daily (q4hx3, qdx5) dosing schedules of 1, 0.25, and 0.12 mg/kg, respectively. CI-940 is being developed for clinical trial on the basis of its potent activity against seven different tumor models, its novel structure, and its apparently novel mechanism of action.

A new antibiotic kazusamycin, was isolated from the culture broth of Streptomyces sp. No. 81-484, which shows antitumor activity against experimental murine tumors. This antibiotic did not possess antibacterial activity against Gram-positive and Gram-negative bacteria, but showed strong cytotoxic activity against HeLa cells in vitro. The chemical and physico-chemical properties of kazusamycin suggest that the molecular formula of this antibiotic is C33H48O7 (MW 556).

Kazusamycin A (KZMA) is a new anticancer antibiotic, which has been proven to have strong anticancer effect and several characteristic features different from currently available anticancer antibiotics. However, there has as yet been no report which had concerned itself with the effect of KZMA on urological cancer. This study was undertaken to determine the inhibitory effects of KZMA on transitional cancer cells in vitro, the augmentation of the inhibitory effect by combining thermal treatment and the effect of KZMA upon DNA distribution. Human transitional cancer cells, KU-1, and T-24 were used as targets. Fifty % inhibitory concentration of KZMA was determined after these cells were exposed to graded concentrations of KZMA for 2 to 48 hours, and to the concentration of KZMA for 2 hours at the temperature of 42 degrees C. Viable cells were counted by dye exclusion assay (DEA) and by tetrazolium-based colorimetric assay (MTT-assay) exposure. KZMA inhibited the growth of the three transitional cancer cells strongly and this inhibitory effect appeared to be depend upon the exposure time and the concentration of KZMA. IC50s after 2-hour exposure at the temperature of 42 degrees C was shown to be decreased to 23 to 87% of that at the temperature of 37 degrees, indicating an augmentation of the inhibitory effect of KZMA by combining thermal treatment. MGH-U1 was the most sensitive to the combination of KZMA and hyperthermia. The cell cycle analysis showed that KZMA had G2-arresting and M-retarding effects, which were different compared with currently available anticancer antibiotics.(ABSTRACT TRUNCATED AT 250 WORDS)