Cytotoxicity and DNA cross-linking induced by peptide conjugated m-L-sarcolysin in human melanoma cells.

Peptichemio is a complex of six peptides containing m-L-sarcolysin which is used in cancer chemotherapy. One of the peptides, L-propyl-m-sarcolysyl-L-p-fluorophenylalanine (PSF), is highly toxic to melanoma cells. We have compared the effects of melphalan, m-L-sarcolysin and PSF on human melanoma cell lines. PSF was 35-fold and 28-fold more toxic to RPMI 8322 melanoma cells than melphalan and m-L-sarcolysin, respectively. Similar differences in the cytotoxic effects of PSF and m-L-sarcolysin were also seen with two other melanoma cell lines. The cytotoxicity of both PSF and m-L-sarcolysin to RPMI 8322 melanoma cells was potentiated by depletion of cellular glutathione. Both PSF and m-L-sarcolysin caused a protracted induction of DNA cross-links in RPMI 8322 cells, with maximum at 24 hours after drug exposure. PSF induced 9-fold higher levels of DNA interstrand cross-links than m-L-sarcolysin, indicating that the increased cytotoxicity of this drug is associated with a more efficient induction of DNA damage.