Antitumor components from an actinomycete strain 6011W

Three bioactive compounds that inhibited nucleoside transport were isolated from the cultured broth of Streptoverticillium sp. 6011W. The structures of those compounds were characterized as cinnamamide, N-(tetrahydro-2-oxo-3-thienyl)-acetamide and benzamide, respectively. They all inhibited radiolabeled thymidine transport into Ehrlich carcinoma cells, with IC50 values of 30.4, 97.2 and 85.4 microM, respectively. When administered i.p., cinnamamide not only inhibited the growth of transplanted tumors but also reduced the number of lung metastases in mice bearing Lewis lung carcinoma. The results suggest that nucleoside transport inhibition assay is a valuable model to search for antitumor agents of natural origin.