title: Enhancement of antitumor activity of 2,4-diamino-5-(3',4'-dichlorophenyl)-6-methylpyrimidine and Baker's antifol (triazinate) with carboxypeptidase G1.
abstract: Carboxypeptidase G1 (CPDG1), an enzyme that degrades folates but not the nonclassical folate antagonists triazinate (TZT, Baker's antifol) and 2,4-diamino-5-(3',4'-dichlorophenyl)-6-methylpyrimidine (DDMP), enhanced the antineoplastic activity of these antifolates. In 6-day cell culture experiments with Walker 256 carcinosarcoma, CPDG1 at levels up to 0.54 unit/ml showed very little inhibitory effect on growth. In the presence of 10(-7) M DDMP, the grown of Walker 256 cells was similar to that of controls, but in combination with CPDG1 (0.1 unit/ml) 80% growth inhibition was observed. TZT at a concentration of 10(-8) M did not affect the growth of Walker 256 cells. The combination of 10(-8) M TZT with CPDG1 (0.1 unit/ml), however, strongly inhibited cell growth. In experiments with rats bearing Walker 256 carcinosarcoma, the administration of CPDG1 (800 units/kg/day) from Day 1 to Day 6 resulted in no significant increase in life span. Administration of TZT in doses up to 0.05 mg/kg on Day 1 or that of DDMP up to 15 mg/kg on Days 1, 3, and 5 had no antitumor effects as measured by survival of the animals. However, CPDG1 (800 units/kg/day) from Day 1 to Day 6 in combination with TZT (0.05 mg/kg on Day 1) or DDMP (15 mg/kg on Days 1, 3, and 5) resulted in increases of 50 and 30%, respectively, in the survival of the tumor-bearing animals. These results demonstrate that CPDG1 enhances the antitumor effects of TZT or DDMP.
mesh_terms: D000818:Animals; D002268:Carboxypeptidases / Q000008:administration & dosage* / Q000494:pharmacology; D002279:Carcinoma 256, Walker / Q000188:drug therapy*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005493:Folic Acid Antagonists / Q000008:administration & dosage*; D008297:Male; D011739:Pyrimethamine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D051381:Rats; D013997:Time Factors; D014227:Triazines / Q000008:administration & dosage*
chemical_list: D005493:Folic Acid Antagonists; D014227:Triazines; C006308:metoprine; C012071:triazinate; D002268:Carboxypeptidases; D011739:Pyrimethamine