A crude cell-free extract is isolated from LI 210 cells in culture by suspension of the cells in a given volume of 0.05mol/LTris-HCl buffer, pH 7.4, and sonic extraction with a Biosonik at 70% maximal output for 30 sec. The supernatant is collected after centrifugation at 105,000 × g for 60 min (4°C) in a Model L Spinco ultracentrifuge. The final protein concentration of the cell-free extracts is approximately 3 mg/mL. The extracts are used as the source of enzymes. Ribonucleotide reductase activity is measured. A unit of enzyme is defined as the amount that catalyzed dCMP synthesis at a rate of 1 mμmole/hr. The assay systems for the measurement of pyrimidine nucleoside (CR) and deoxynucleoside (TdR, CdR) kinases are essentially those described by Chu and Fischer. However, reactions are terminated by heating for 2 min in a boiling water bath, and the phosphorylated derivatives are isolated according to the method of Bach. Fifty-jul aliquots are applied to 1-inch discs of diethylaminoethyl paper, which are then placed in counting vials and eluted with 0.5 mL of 0.5 mol/LPCA. After 1 hr, 12 mL of Diotol are added, and the radioactivity is determined.

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Twenty mL of cells (circa 1×10⁴ cells/mL) are pipetted into sterilized culture tubes with screw caps and incubated at 37°C overnight. The experiment is initiated by the addition of 1 mL of 5-Azacytidine (5-azaCR) or medium for a given period (from 0 to 240 min) prior to the addition of 1 mL of metabolite (or medium). Cell growth is determined twice a day for 3 days by means of a Model A Coulter counter. To determine IDSO and ID90 values, 5 mL of L1210 cells (5×10³ cells/mL) are incubated with the drug at 37°C for 3 days, and cell growth is determined.

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

For the in vivo experiments, leukemic mice (bearing circa 1×10³ cells/animal) are given injections i.p. with 0.2 mL of 5-Azacytidine (5-azaCR) of a given concentration. Two hr later, the reaction is started by injecting 0.5 mL of labeled metabolite (TdR-³H or UR-³H, 10 /μCi/12.5 μg). After 1 hr, animals (3 mice/group) are killed by cervical fracture, and the ascites are treated with heparin, collected, pooled, and then centrifuged immediately in a Sorvall refrigerated centrifuge Model R2C-B at 800×g for 10 min (4°C).

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

• [1]. Christman JK. 5-Azacytidine and 5-aza-2'-deoxycytidine as inhibitors of DNA methylation: mechanistic studies and their implications for cancer therapy. Oncogene. 2002 Aug 12;21(35):5483-95.

  [2]. Creusot F, et al. Inhibition of DNA methyltransferase and induction of Friend erythroleukemia cell differentiation by 5-azacytidineand 5-aza-2'-deoxycytidine. J Biol Chem. 1982 Feb 25;257(4):2041-8.

  [3]. Li LH,et al. Cytotoxicity and mode of action of 5-azacytidine on L1210 leukemia. Cancer Res. 1970 Nov;30(11):2760-9.

244.20

C₈H₁₂N₄O₅

320-67-2

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Room temperature in continental US; may vary elsewhere