Proline prodrug of melphalan targeted to prolidase, a prodrug activating enzyme overexpressed in melanoma.
OBJECTIVE
To determine the bioactivation and uptake of prolidase-targeted proline prodrugs of melphalan in six cancer cell lines with variable prolidase expression and to evaluate prolidase-dependence of prodrug cytotoxicity in the cell lines compared to that of the parent drug, melphalan.


METHODS
Hydrolysis, cell uptake, and cell proliferation studies of melphalan and the L: - and D: -proline prodrugs of melphalan, prophalan-L: and prophalan-D: , respectively, were conducted in the cancer cell lines using established procedures.


RESULTS
The bioactivation of prophalan-L: in the cancer cell lines exhibited high correlation with their prolidase expression levels (r (2) = 0.86). There were no significant differences in uptake of melphalan and its prodrugs. The cytotoxicity of prophalan-L: (GI(50)) in cancer cells also showed high correlation with prolidase expression (r (2) = 0.88), while prophalan-D: was ineffective at comparable concentrations. A prolidase targeting index (ratio of melphalan to prophalan-L: cytotoxicity normalized to their uptake) was computed and showed high correlation with prolidase expression (r (2) = 0.82).


CONCLUSIONS
The data corroborates the specificity of prophalan-L: activation by prolidase as well as prolidase-targeted cytotoxicity of prophalan-L: in cancer cell lines. Hence, prophalan-L: , a stable prodrug of melphalan, exhibits potential for efficiently targeting melanoma with reduced systemic toxicity.
Mittal
Sachin
S
Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, USA.
Song
Xueqin
X
Vig
Balvinder S
BS
Amidon
Gordon L
GL
D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D001692:Biological Transport; D001711:Biotransformation; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002699:Chlorambucil / Q000378:metabolism; D004150:Dipeptidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D006868:Hydrolysis; D020128:Inhibitory Concentration 50; D008545:Melanoma / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008558:Melphalan / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011392:Proline / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013237:Stereoisomerism
D018906:Antineoplastic Agents, Alkylating; D011355:Prodrugs; D011480:Protease Inhibitors; D012333:RNA, Messenger; C074949:carbobenzoxyproline; D002699:Chlorambucil; D011392:Proline; D004150:Dipeptidases; C022449:proline dipeptidase; D008558:Melphalan