UCE6, a new antitumor antibiotic with topoisomerase I-mediated DNA cleavage activity produced by actinomycetes: Producing organism, fermentation, isolation and biological activity

A novel antitumor antibiotic, UCE6 (1,3,8,10,11-pentahydroxy-2-methyl-10-(2-oxo-4-hydroxypentyl)naphthacene-5, 12-dione) with topoisomerase I-mediated DNA cleavage activity, was isolated from the culture broth of actinomycetes strain UOE6. Addition of silicone oil antifoam agent, KS69 (2%), to the fermentation enhanced the production of UCE6 by similar to 3 fold. A total of 1.15 g of UCE6 was recovered as reddish orange crystals from a 100 liter fermentation supplemented with 2% KS69. UCE6 exhibited growth inhibitory activity against HeLa S3, HCT116 and Lu-65 cells comparable to that of camptothecin.