Novel peptide derivatives of bleomycin A5: synthesis, antitumor activity and interaction with DNA

A series of novel amino acid and peptide derivatives of bleomycin (BLM) A(5) were synthesized. All the compounds possessed significant antitumor activities in vitro against HL-60, BGC-823, PC-3MIE8, and MDA-MB-435 cell lines. Their antitumor activities against MDA-MB-435 were 10-fold higher than BLM A5. The DNA cleavage studies indicated that the hydrophobic amino acid or peptide derivatives of BLM A5 could induce higher cleavage ratio of double to single strand DNA than BLM A5. From the DNA binding studies, we found that the derivatives containing either D-conformation amino acid or basic amino acid could facilitate DNA binding of BLM.