tetrahydrouridine and Sarcoma-180

Extracts of solid mouse tumors were examined for deoxycytidine kinase and deaminase activities. 1beta-D-Arabinofuranosylcytosine nucleotide was formed at a rate of 45 nmoles/hr by Glioma 26/57 and only 14 nmoles/hr by Ridgway osteogenic sarcoma. Deaminase activity was highest in Lewis lung (114 nmoles of 1-Beta-D-arabinofurano-syluridine formed per hr) and in CaD2 (104 nmoles of u-beta-D-arabinofuranosyluridine formed per hr). Deaminase activity in tumor extracts is sensitive to freezing, while deaminase activity in monkey serum is not. It was observed that kinase activity varies by as much as 50% in different cell lines of the same tumor. In the presence of tetrahydrouridine, kinase activity was significantly increased in most of the tumors studied.

Topics: Adenocarcinoma; Aminohydrolases; Animals; Cell Line; Chick Embryo; Cytarabine; Freezing; Glioma; Lung Neoplasms; Mammary Neoplasms, Experimental; Melanoma; Mice; Mice, Inbred AKR; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Inbred DBA; Neoplasms, Experimental; Osteosarcoma; Phosphotransferases; Pyrimidine Nucleotides; Sarcoma 180; Tetrahydrouridine; Uridine

The phosphorylation of 1-beta-D-arabinofuranosylcytosine (ara-C) was studied in cell-free extracts from a variety of solid mouse tumors, L1210 ascites and in normal liver and spleen. Two apparent Michaelis constants were observed for kinase activity in Lewis lung (Km1, 4.15 muM; Km2 58.1 muM), sarcoma 180 (Km1 6.66 muM; Km2 56.18 muM), adenocarcinoma 755 (Km1 4.34 muM; Km2 50.0 muM) and l1210 (Km1 29.41 muM; Km2 41.67 muM). The Km1 values generally ranged from 5 to 20 muM 3H-ara-C while the Km2 values ranged from 20 to 60 muM 3H-ara-C. Normal spleen (Km 47.6 muM), normal liver (Km 10.0 muM) and Ridgway osteogenic sarcoma (Km 31.2 muM) had single Km values. In the presence of tetrahydrouridine (H4U), the in vitro phosphorylation of ara-C was increased as much as 91% in cell-free extracts from adenocarcinoma 755; lesser increases were observed in other tumor extracts. At low substrate concentrations, the apparent Km decreased or did not change in the presence of H4U, while at higher substrate concentrations the apparent Km was increased or did not change in the presence of H4U. In the presence of H4U, Vmax for kinase activity increased most in those tumors possessing deaminase activity.

Topics: Adenocarcinoma; Animals; Bone Neoplasms; Cytarabine; Cytidine Deaminase; Deoxycytidine; Female; In Vitro Techniques; Kinetics; L Cells; Liver; Lung Neoplasms; Male; Mice; Neoplasm Transplantation; Neoplasms, Experimental; Osteosarcoma; Phosphorus; Phosphotransferases; Sarcoma 180; Spleen; Tetrahydrouridine; Uridine