The antitumor antibiotic pingyangmycin (PYM; bleomycin A�N) is produced by Streptomyces pingyangensisn. The chemical structure or PYM is similar to that of bleomycin (BLM), but their terminal amine moieties are different, and the mechanism of PYM inhibition of tumor growth has not been well studied. In this article, we used the multiwell / cell growth curve method to assess the inhibition KB cell growth by PYM; we also investigated the mechanism of tumor cell growth as well as the morphological variations of drug-treated cells. DNA synthesis inhibition assay was used to evaluate the antitumor mechanism of PYM. Treatment with 5 μ g/ml PYM for 24 hours significantly inhibited cell growth and synthesis of DNA (p<0.05). Therefore, it appears PYM exerts its inhibitory effect on KB cell growth by inhibiting synthesis of DNA.
