The antiproliferative action of a melphalan hexapeptide with collagenase-cleavable site.
OBJECTIVE
The objective of the present study was to examine the relevance of collagenase in the antitumor action of a melphalan peptide (MHP) with a collagenase-cleavable sequence. The question was addressed as to whether collagenase may act as an activator or a target in the antiproliferative mechanism of MHP.


METHODS
Melphalan was inserted into peptides representing the sequence Pro-Gln-Gly-Ile-Ala.Gly of the collagenase-cleavable site in collagens. Changes in growth and collagenase IV activities of HT-1080, HT-29, HT-168, and MCF-7 cell cultures were investigated.


RESULTS
The present investigations provide data indicating that Pro-Gln-Gly-Ile-Mel-Gly (melphalan hexapeptide, MHP) is a substrate for both bacterial and 72-kDa type IV collagenases and that in this way it can generate Ile-Mel-Gly (melphalan tripeptide, MTP) of higher cytotoxic potency. Indeed, the formation of MTP was detected in the conditioned medium of HT-1080, a collagenase IV-producing human fibrosarcoma. In a comparison of equimolar concentrations of melphalan and its two peptide derivatives (MHP and MTP), superior antiproliferative action of MTP was seen in HT-29, HT-1080, and HT-168 tumor cell cultures. However, the relatively modest cytostatic actions of MHP were increased when bacterial collagenase was added to the cell cultures. After melphalan treatment, reduced levels of both 92 and 72-kDa type IV collagenases were seen in the HT-1080 cell cultures. However, the reduction of collagenase activity and the cell counts did not run parallel in the MTP- or MHP-treated cultures; indeed, collagenase activity related to cell numbers showed an elevated level.


CONCLUSIONS
As the conversion of MHP to the more toxic MTP was detected in the presence of collagenases, it is possible that collagenase-directed activation of prodrugs may be a promising approach for the development of more selective cytostatic drugs against malignant tumors with high collagenase activities.
Timár
F
F
First Institute of Pathology and Experimental Cancer Research, Semmelweis University of Medicine, Budapest, Hungary.
Botyánszki
J
J
Süli-Vargha
H
H
Babó
I
I
Oláh
J
J
Pogány
G
G
Jeney
A
A
D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D017364:Collagenases / Q000187:drug effects / Q000378:metabolism*; D015195:Drug Design; D006801:Humans; D066298:In Vitro Techniques; D008558:Melphalan / Q000031:analogs & derivatives* / Q000494:pharmacology*; D010446:Peptide Fragments; D011355:Prodrugs / Q000494:pharmacology*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D018906:Antineoplastic Agents, Alkylating; D010446:Peptide Fragments; D011355:Prodrugs; D017364:Collagenases; D008558:Melphalan