[Antitumor activity of the clavam peptide antibiotic G0069A].

Antibiotic G0069A, produced by a Streptomyces strain isolated from a soil sample collected in Yunnan Province, China, has been verified as a clavam peptide. Determined by MTT assay, G0069A showed highly potent cytotoxicity to cancer cells with multidrug resistance. The IC50 values of G0069A to KB and KB/VCR cells were 0.60 and 0.46 mumol.L-1, and to MCF-7 and MCF-7/ADM cells were 1.4 and 1.2 mumol.L-1, respectively. G0069A displayed equally potent cytotoxicity to the parent cell lines and their resistant sublines. When administered by i.v. or i.p. route at tolerable doses, G0069A exhibited markedly inhibitory effect on the growth of sarcoma 180 and hepatoma 22 in mice. At dose level of 3 mg.kg-1, i.v., x3, sarcoma 180 and hepatoma 22 were suppressed by 87%(P < 0.01) and 72%(P < 0.01), respectively. The results indicate that G0069A is a beta-lactam antibiotic showing antitumor activity.

Antibiotic C3368-A, a fungus-derived nucleoside transport inhibitor, potentiates the activity of antitumor drugs.

Antibiotic C3368-A (CA) is produced by a fungus strain from a soil sample collected in Antarctica. CA markedly inhibited radiolabeled thymidine and uridine transport in mouse Ehrlich carcinoma cells, its 50% inhibitory concentration (IC50) being 4.6 and 7.7 microM, respectively. In clonogenic assay, CA displayed a synergistic effect with methotrexate (MTX), mitomycin C (MMC), 5-fluorouracil (5FU), and Adriamycin (ADR) against human oral epidermoid carcinoma KB cells. CA also markedly enhanced the inhibitory effect of 5FU and ADR on the proliferation of human hepatoma BEL-7402 cells as determined by the p-nitrophenyl-N-acetyl-beta-D-glucosaminide (NAG) enzyme-reaction assay. 5FU or ADR cytotoxicity was not augmented by CA in human fetal lung 2BS cells. In vivo, CA significantly potentiated the inhibitory effect of MMC against colon carcinoma 26 in mice. No significant augmentation of toxicity by the combination was found in treated mice. The results suggest that CA, the newly found nucleoside-transport inhibitor, may be useful in potentiation of the effect of antitumor drugs.

[A fungus-derived novel nucleoside transport inhibitor potentiates the activity of antitumor drugs].

Antibiotic C3368-B (CB), identified as 3,9-dihydroxy-1-methoxy-7-methylanthraquinone, is produced by a fungus strain, Chrysosporium verrucosum Tubaki, isolated from a soil sample collected from Antarctica. CB was found to be a highly-active nucleoside transport inhibitor. By radiolabelled nucleoside assay, CB was shown to markedly inhibit thymidine and uridine transport in Ehrlich carcinoma cells, with IC50 values of 7.5 and 9.6 mumol.L-1 respectively. CB showed fairly low cytotoxicity to tumor cells. The IC50 values for epidermoid cancer KB cells and hepatoma BEL-7402 cells in clonogenic assay was 77 and 69 mumol.L-1. At relatively noncytotoxic concentrations, CB markedly enhanced the cytotoxicity of methotrexate, 5-fluorouracil, mitomycin C against KB cells and BEL-7402 cells. CB was also found to partly reverse the multi-drug resistance to vincristine and actinomycin D in leukemia L1210/MDR cells. The IC50 values were reduced by 4.9-fold (1.75 to 0.36 mumol.L-1) for vincristine and 3.3-fold (0.39 to 0.12 mumol.L-1) for actinomycin D. These results suggest that CB, as a newly-found nucleoside transport inhibitor, may be potentially useful in cancer chemotherapy.

New antibiotics 4181-A and B from Streptomyces griseus; taxonomy, fermentation, isolation and characterization.

The new antibiotics 4181-A and B were isolated from the fermentation broth of Streptomyces griseus, a soil isolate. Their molecular formulae were determined as C29H21NO9 and C28H19NO9, respectively. The UV, IR and NMR spectra suggest that they possess a quinone moiety in their structures. They were found to have antibacterial, antifungal and antitumor activity.