Methylthioadenosine phosphorylase deficiency in human non-small cell lung cancers.

Methylthioadenosine (MeSAdo) phosphorylase, a purine metabolic enzyme, is present in all normal mammalian tissues. A deficiency of this enzyme has been reported in some human leukemias and lymphomas and in a few solid tumors. In the present study, a specific immunoassay was used to assess the enzyme levels in human non-small cell lung cancer cell lines and primary tumors. We also tested the effects of MeSAdo phosphorylase-selective chemotherapy on the in vitro growth of enzyme-positive and enzyme-negative lung cancer cell lines. Of 29 non-small cell lung cancers, 9 (6 cell lines and 3 primary tumors, 31%) lacked detectable immunoreactive enzyme protein. Both 5,10-dideazatetrahydrofolate, an inhibitor of de novo purine synthesis, and methionine depletion, combined with MeSAdo, prevented the growth of the enzyme-negative non-small cell lung cancer cells under conditions in which enzyme-positive cells utilized MeSAdo to endogenously synthesize purine nucleotides and methionine. Our data suggest that MeSAdo phosphorylase deficiency is frequently found in non-small cell lung cancers and can be exploited in designing enzyme-selective chemotherapy.

Metabolism of anti-herpes agent 5-(2-chloroethyl)-2'-deoxyuridine in mice and rats.

The enzymatic splitting and metabolic elimination of anti-viral agent 5-(2-chloroethyl)-2'-deoxyuridine [CEDU] have been studied. For elucidation of structures of metabolites, several different kinds of extraction, purification and spectroscopic methods were used (Extrelut LC, TLC, HPLC, MS, NMR, IR, UV and CD). For mass spectral analysis, various ionization techniques (EI, CI and FAB-MS) were performed as complementary methods. After oral administration of [14C]-CEDU to mice and rats, the parent compound, 5-(2chloroethyl) uracil [CEU] and hydroxylated CEU metabolites were isolated and identified from urine and faeces by the above mentioned methods. The CEDU showed rapid phosphorolysis in vitro with thymidine phosphorylase Km 41.0 +/- 5.0; and uridine phosphorylase Km 10.0 +/- 1.5. The cleavage of the N-glycosidic bond of the nucleoside analogue and a new metabolic pathway of CEDU [stereoselective oxidation of 5-(2-chloroethyl) uracil] was observed in both species.

cis-trans-isomerization of [E]-5-(2-bromovinyl)-2,2'-anhydrouridine in vivo in rats.

1. [E]-5-(2-bromovinyl)-2,2'-anhydrouridine [( E]BVANUR) has considerable antiviral activity against herpes simplex virus type 1 (HSV-1). 2. [E]BVANUR is not a substrate of pyrimidine nucleoside phosphorylases, but it is an inhibitor of uridine phosphorylase (Ki = 450 nM). 3. [E]BVANUR (trans-isomer, parent compound) undergoes isomerization to [Z]BVANUR (cis-isomer), the only metabolite in rat, which was identified by h.p.l.c., mass spectra and n.m.r. spectroscopy. 4. Absorption of the drug from the gastrointestinal tract after oral administration is minimal. Absorption of [E]BVANUR from the abdominal cavity after i.p. administration was slow.

Effective sample preparation method for extracting biologically active compounds from different matrices by a microwave technique.

A method is described for extracting lupin alkaloid (sparteine) and drug metabolites from different matrices (seeds and rat faeces) using microwave energy and for checking the homogeneity of the electric field in the microwave oven. The high-performance liquid chromatographic separation and determination of the extracted compounds showed that the microwave extraction method is more advantageous than other traditional extraction methods with regard to the yield of extraction and the time and cost of the procedure. The potential degradation of the extracted compounds may be considerably reduced.

Demonstration of stereoselective disposition of warfarin enantiomers by whole-body autoradiography.

The oral anticoagulant warfarin and its 14C-labelled derivative are commercially available in racemic forms. Two methods for the chromatographic resolution of the radiolabel were used to investigate the distribution of radioactivity of radioactivity of individual enantiomers in the rat by whole-body autoradiography. Computer-assisted quantification of autoradiograms indicated the average disappearance of levo-warfarin and its metabolites to be substantially slower than that of dextro-warfarin and its metabolites from the following organs: liver, pancreas, kidney, lung, blood, intestines.

Differential effects of 2,2'-anhydro-5-ethyluridine, a uridine phosphorylase inhibitor, on the antitumor activity of 5-fluorouridine and 5-fluoro-2'-deoxyuridine.

2,2'-Anhydro-5-ethyluridine (ANEUR), a potent inhibitor of uridine phosphorylase, markedly potentiated the antitumor activity of fluorouridine (FUR) against murine mammary adenocarcinoma 755 in BDF1 mice and human colon adenocarcinoma LS174T in athymic-nude mice. Whereas ANEUR annihilated the antitumor activity of 5-fluoro-2'-deoxyuridine (FUdR) and 5'-deoxy-5-fluorouridine (DFUR) in the murine adenocarcinoma 755 system, it did not alter the antitumor activity of FUdR in the human adenocarcinoma LS174T system. In vitro, ANEUR proved inhibitory to the phosphorolytic cleavage of both FUR and FUdR by uridine phosphorylase, and this could explain why in vivo conversion of FUR and FUdR to 5-fluorouracil was suppressed. FUR can be held directly responsible for the antitumor effects observed in the murine adenocarcinoma 755 system, whereas in the activity against human adenocarcinoma LS174T may be mediated by both FUR and FUdR.

Combined treatment of anaplastic astrocytoma (grade 3-4) with diacetyl-dianhydro-galactitol (DADAG).

Autoradiographic studies of labeled diacetyldianhydro-galactitol (DADAG) with tumor bearing animals revealed that the CNS accumulates high amounts of DADAG-derived radioactivity and the elimination from the brain seems to be relatively slow. This observation and the activity of DADAG against murine ependymoblastoma classified the drug as a promising agent for the treatment of malignant brain tumors. In a series of 30 evaluable consecutive patients who were operated on for anaplastic astrocytomas, DADAG has been applied during and subsequent to postoperative radiotherapy. No severe toxicity occurred. Survivals were compared with a group of patients who got irradiation alone. Statistical analysis did not show significantly better survivals in the DADAG treated group: median value was 46.5 weeks, p = 0.232.

Biotransformation of 5-(2-chloroethyl)-2'-deoxyuridine in male NMRI mice.

When the selective anti-herpes agent [2-14C]-5-(2-chloroethyl)-2'-deoxyuridine [( 14C]CEDU) was administered as a single oral dose to mice, 87.9% of the radioactivity was excreted in the urine and 11.2% in the feces within 72 hr. Compounds accounting for 84% of the 14C radioactivity in the 0- to 24-hr urine were isolated by various chromatographic techniques and identified by MS, NMR, IR, and CD analysis. Approximately 25% of the radioactivity found in the urine was the parent compound (CEDU). According to the 14C-metabolites detected in the urine, one may infer that [14C]CEDU is metabolized, first, by cleavage of its N-glycosidic bond, resulting in the formation of 5-(2-chloroethyl)uracil (38.7%) and, second, by stereoselective hydroxylation of the alpha carbon atom of the haloalkyl side chain of 5-(2-chloroethyl)uracil, resulting in the formation of 5-(1-hydroxy-2-chloroethyl)uracil (29.6%). CEDU was absorbed rapidly from the gastrointestinal tract and the bloodstream, and did not show any particular accumulation in mouse tissues, as revealed by whole body autoradiography.

Biological activity of the potent uridine phosphorylase inhibitor 5-ethyl-2,2'-anhydrouridine.

5-Ethyl-2,2'-anhydrouridine (ANEUR) proved to be a potent inhibitor of uridine phosphorylase isolated from sarcoma 180 cells with an apparent Ki (Ki(app) value of 99 nM. Coadministration of ANEUR with 5-fluorouridine (FUR) resulted in increased toxicity of FUR. The LD50 value of FUR alone was 9 mg/kg (when administered for 5 consecutive days) while the LD50 was 3 mg/kg when FUR was administered together with ANEUR in vivo. There was no significant difference in mean tumor weight on day 10 between control animals and animals treated with FUR (5 mg/kg/day for 3 days) or ANEUR (280 mg/kg/day for 3 days). When FUR was coadministered with ANEUR, mean tumor weight was 91% less than that of the untreated controls, showing that ANEUR, the potent URPase inhibitor, increases the antitumor effect of FUR.

5-Substituted-2,2'-anhydrouridines, potent inhibitors of uridine phosphorylase.

5-Substituted-2,2'-anhydrouridines are a new class of competitive inhibitors of uridine phosphorylase. The most potent member of the series is 2,2'-anhydro-5-ethyluridine with an apparent Ki value of 25 nM. These compounds are selective inhibitors of uridine phosphorylase and have no effect on thymidine phosphorylase. 5-Substituted-2,2'-anhydrouridines are no substrates of either uridine phosphorylase or thymidine phosphorylase.

Metabolism of 14C-3-trifluoromethyl-alpha-ethylbenzhydrol in rats.

Metabolism of 3-trifluoromethyl-alpha-ethyl-benzhydrol (I), hepatic enzyme inducer has been studied in rats. Five metabolites in bile and four in urine, as well as minute amounts of the original drug (I) were identified. The only major metabolite in bile and one of the two major metabolites in urine were found to be aromatic hydroxylated products of I, i.e., 3-trifluoro-methyl-4'-hydroxy-alpha-ethylbenzhydrol (II). The results of enzymatic hydrolysis with beta-glucuronidase/arylsulfatase suggest that hydroxyl groups of metabolites are conjugated. Considering the structure of metabolites isolated a probable order of metabolite formation is outlined.