Activation of methotrexate-phenylalanine by monoclonal antibody--carboxypeptidase A conjugate for the specific treatment of ovarian cancer in vitro.
Monoclonal antibody 4E3 directed against a glycosylated surface protein on human ovarian teratocarcinoma cells (CRL-1572 cell line) was conjugated to bovine carboxypeptidase A (CPA) using a 3400 Da polyethylene glycol chain bearing an N-hydroxysuccinimide group at both ends. The conjugate preparation was purified by fast protein liquid chromatography on a Superose 12/30 HR column. The 4E3-CPA conjugate was recovered in the third fraction by SDS-PAGE analysis. The specific binding of the 4E3-CPA conjugate to CRL-1572 cells was confirmed by a FACS analysis and the enzymatic activity of the conjugate remained while tested with hippuryl-L-phenylalanine. In vitro cytotoxic assays on CRL-1572 cells showed that the prodrug methotrexate-phenylalanine (MTX-Phe) alone was non-toxic (ID50 > 1000 ng ml-1) but was selectively converted to MTX when the cells were pretreated with 50 micrograms ml-1 4E3-CPA conjugate, which enhanced considerably the pharmacological activity of the prodrug with an ID50 of 70 ng ml-1. The co-culture assays with CRL-1572 and MRC-5 cells (human normal lung diploid fibroblast cell lines) demonstrated the specificity of the 4E3-CPA conjugate for the CRL-1572 cells since no cytotoxicity was observed on the MRC-5 cells. When both cell lines were mixed in ratios ranging from 1:10,000 to 1:5 (CRL-1572:MRC-5), the significant increase in the ID25 was correlated with the proportion of tumoral cells present in the cell inoculum. These results suggest that MTX-Phe combined with 4E3-CPA conjugate is a promising model for a more selective and localised anti-cancer chemotherapy based on the ADEPT concept.
Perron
M J
MJ
Department of Biochemistry, Faculty of Medicine, Université Laval, Sainte-Foy, Québec, Canada.
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D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D000912:Antibodies, Neoplasm / Q000627:therapeutic use*; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage*; D002268:Carboxypeptidases / Q000008:administration & dosage*; D043422:Carboxypeptidases A; D005260:Female; D006801:Humans; D008727:Methotrexate / Q000008:administration & dosage / Q000031:analogs & derivatives*; D010051:Ovarian Neoplasms / Q000188:drug therapy*; D010649:Phenylalanine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D011355:Prodrugs / Q000008:administration & dosage*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000964:Antimetabolites, Antineoplastic; D011355:Prodrugs; C091716:methotrexate-alpha-phenylalanine; D010649:Phenylalanine; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D008727:Methotrexate