Effects of the alpha-D-anomer of 5-aza-2'-deoxycytidine on L1210 mouse leukemic cells in vitro and in vivo.

The alpha-D-anomer of 5-aza-2'-deoxycytidine inhibited cell growth in vitro in L1210 mouse leukemic cells (concentration causing 50% inhibition about 1 X 10(-6) M) and was also active in vivo in increasing the life span of mice with L1210 leukemia by 100% after a single i.p. injection (800 to 1000 mg/kg). This effect could be reversed by 2'-deoxycytidine. The alpha-D-anomer produced approximately 100-fold less host toxicity than did 5-aza-2'-deoxycytidine. It was observed that alpha-D-anomer, when kept at 23 degrees for 72 hr, inhibited the uptake of radioactive 2'-deoxycytidine by L1210 cells in vitro as well as the phosphorylation of 2'-deoxycytidine by a cell-free extract from L1210 cells. These effects could not be obtained with the fresh solution of the drug. It is proposed that the action of alpha-D-anomer is due to its conversion to 5-aza-2'-deoxycytidine as shown by high-performance liquid chromatography performed on water solutions of both anomers.

Mechanism of action of 1-beta-D-arabinofuranosyl-5-azacytosine and its effects in L1210 mouse leukemia cells.

Ara-5AC depresses the growth of L1210 cells in vivo in a manner that is schedule-independent and at the dose levels which are similar to those of ara-C. The 50% inhibitory concentration for ara-5AC in L1210 system is about 0.75 microM. In distinction to ara-C the drug does not elicit the proliferation of proerythroblasts in the mouse bone marrow. It is phosphorylated by dCyd kinase, and the respective Km value is 70 microM. Ara-5AC is incorporated into DNA and almost completely blocks the incorporation of thymidine at a concentration of 10 microM.

Potential carcinogenicity of the synthetic 1,3,6-triazine (6-azapyrimidine) nucleic acid analogues determined by DC polarography. II. Nucleosides of 6-azauracil.

The polarographic reduction of six synthetic 1,3,6-triazine (6-aza) nucleosides with 6-azauracil as the nucleoside base in the strictly anhydrous solutions was studied in the absence and presence of alpha-lipoic acid. The values of the half-wave potentials E1/2 and the parameter of potential carcinogenicity tg alpha were compared for six nucleosides of 6-azauracil and two nucleosides of 4-thio-6-azauracil. The current value of the first diffuse polarographic wave or a new diffuse polarographic wave belonging to the nucleoside-alpha-lipoic acid complex increased with the increase of the alpha-lipoic acid concentration for the all compounds only marginally. Although this diffuse current increase was linear and dependent on the alpha-lipoic acid concentration in anhydrous solutions, the determined index tg alpha values ranged between 0.027 and 0.114. This is an indication of a very low potential carcinogenicity of the all nucleoside analogues investigated.

Polarographic reduction and carcinogenic index tg alpha of 5-aza nucleosides possessing antileukemic activity.

Polarographic behavior of arabinosyl-5-azacytosine (ara-AC) and 5-azacytidine in anhydrous dimethylformamide and in Britton Robinson buffer is described. 5-Azacytidine and ara-AC underwent two-electron reduction under the polarographic conditions used. Carcinogenic index tg alpha estimated in the presence of alpha-lipoic acid was 0.295 for 5-azacytidine and 0.275 for ara-AC.

Potential carcinogenicity of the synthetic 1,3,6-triazine (6-aza) nucleic acid analogues determined by DC polarography. I. Nucleobases.

The polarographic reduction of several synthetic 1,3,6-triazine (6-aza) nucleobases in the strictly anhydrous solution was studied in the absence and presence of alpha-lipoic acid. The values of the half-wave potentials E1/2 and the parameter of potential carcinogenicity tg alpha were determined for one natural and 5 synthetic nucleobases. The current value of the first diffuse polarographic wave or a new diffuse polarographic wave belonging to the nucleobase-alpha-lipoic acid complex increased with the increased alpha-lipoic acid concentration for the all compounds only marginally. Although this diffuse current increase was linearly depended on the alpha-lipoic acid concentration in anhydrous solutions, the determined index tg alpha values ranging between 0.029 and 0.108 indicated a very low potential carcinogenicity of the all nucleobases investigated.

Improved synthesis, antibacterial activity and potential carcinogenicity of 5-amino-1 ,2,4-thiadiazol-3(2H)-one.

This paper reports on the preparation of 5-amino-1,2,4-thiadiazol-3(2H)-one, a sulfur-containing analogue of cytosine with the -CH=CH- group between the positions 5 and 6 of the pyrimidine ring replaced by the divalent sulfur (-S-). Improved procedures for the preparation of thiobiuret, some of its methyl derivatives and 5-amino-1,2,4-thiadiazol-3(2H)-one are documented. Thiobiuret and its N-methyl derivatives were obtained by addition of hydrogen sulfide to the respective 1-cyanoureas. Subsequent oxidation of thiobiuret with hydrogen peroxide in alkaline medium produced 5-amino-1,2,4-thiadiazol-3(2H)-one. This substance was traced back converted to the starting thiobiuret by reaction with cysteine hydrochloride. Alkaline degradation of thiadiazol led to the formation of 1-cyanourea isolated as its silver salt. An investigation of the thiadiazol biological activities has shown that it inhibits the growth of E. coil by 10% at 8.5 microM concentrations, but exhibited no cytostatic activity in L1210, HeLa S3 and HL-60 cell lines. Potential carcinogenicity of the prepared compounds was determined by a DC polarographic method. While the values of the parameter of carcinogenicity for all intermediates indicate only marginal carcinogenic potential, the value of the parameter of carcinogenicity for the thiadiazole indicates possible carcinogenicity of this compound.

Polarographic properties and potential carcinogenicity of some natural nucleosides and their synthetic analogues.

The polarographic reduction and the index of potential carcinogenicity tg alpha determined polarographically in aprotic conditions and in the presence of alpha-lipoic acid of nine naturally occurring and synthetic pyrimidine and six synthetic 1,3,5-triazine (5-aza) nucleosides was compared to the reduction of eight synthetic 1,3,6-triazine (6-aza) nucleosides. Nucleosides are of interest because of their key role in the nucleic acid structure and because of the antimetabolite and cytotoxic/antileukemia properties of their synthetic analogues. It was shown that polarographic reduction of the studied compounds is achieved at gradually increased potentials in the order of 6-aza < 5-aza < pyrimidine nucleosides. On other hand, the potential carcinogenicity of studied compounds increases usually in the order of pyrimidine < 6-aza << 5-aza nucleoside. The only compounds with remarkable potential carcinogenicity identified at this study were those ones from the 5-aza (1,3,5-triazine) antimetabolite series-arabinosyl-5-azacytosine (0.275), 5-aza-cytidine (0.295) and 5-aza-uracil (0.400)-and 2,2'-anhydrouridine (0.260). The relation of the data obtained to biological activity of nucleosides included in the study is discussed.

Preparation and biological activity of 5,6-dihydro-5-azapyrimidine nucleosides.

The reaction of 5-azapyrimidine nucleosides Ia-IXa with zinc powder in acetic acid afforded the respective 5,6-dihydro derivatives Ib-IXb in high yields. This procedure represents a convenient and general method for preparation of the title compounds. The effects of some dihydro-5-azapyrimidine nucleosides on the growth in vitro of L1210 mouse leukemic cells were estimated.

Synthesis and biological activity of 2'-deoxy-6-methyl-5-azacytidine and its alpha-D-anomer.

The stannic chloride catalyzed glycosylation of bis-tri-methylsilyl-6-methyl-5-azacytosine 2 with the halogenose 3 leading to the protected anomeric nucleosides 4a and 4b was investigated. Methanolysis of 4a and 4b afforded the corresponding free nucleosides 1a and 1b. Compounds 4a and 4b were also prepared by the isocyanate method via acetylamidinourea derivatives 6. Antileukemic activity in vitro and inhibition of growth of E. coli by the title compounds are reported.

Depression of experimental gastric ulcers and acute pancreatitis in rats treated by 5-azacytosine, 5-azacytidine and their N-methyl derivatives.

5-Azacytosine, 1-methyl-5-azacytosine and 5-azacytidine administered to rats with a ligated pylorus block gastric secretion, gastric acidity, the extent of hemorrhage and the number and size of gastric defects. The same drugs also depress the development of experimental acute pancreatitis mediated in rats by interstitial administration of 7.5% natrium cholate into the pancreas in vivo. The drugs affected the amount of abdominal fluid and 6 h after the treatment the pathological changes were significantly decreased.