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N Prajda

Publications and source records attributed to N Prajda.

50 records · Page 3Linked to original sources
PubMed1975

Malignant transformation-linked imbalance: decreased xanthine oxidase activity in hepatomas.

Xanthine oxidase was decreased 2- to 10-fold in all examined rat hepatomas irrespective of the malignancy; growth rate and degrees of histological differentiation of the neoplasms. The affinity to substrate (KM=6-8 muM) and the pH optimum (8.0) of the liver and hepatoma enzymes were the same. The reprogramming of gene expression, as manifested in the decreased activity of this key purine metabolizing enzyme, appears to be specific to neoplastic transformation. Since glutamine PRPP amidotransferase activity was increased but the opposing enzyme, xanthine oxidase, was decreased in all the hepatomas, the reprogramming of gene expression results in an imbalance that favors synthesis against catabolism. This enzymatic imbalance should confer selective advantages to the cancer cells.

Age Factors↗
PubMed1975

Investigation of 17-ketosteriod excretion in mastopathia and premenopausal breast cancer.

Measurement of the excretion of total 17-ketosteroids, androsterone, etiocholanolone, and dehydroepiandrosterone demonstrate in contrast to the well known age dependency of normal women in cases of both mastopathia and breast cancer the following results: 1. the age dependence of the 17-ketosteriod excretion is not marked; 2. the total 17-ketosteroid excretion is lower than that of normal controls, 3. the values of the etiocholanolone excretions and that of the dehydroepiandrosterone excretions are similarly lower.

17-Ketosteroids↗
PubMed1975

Imbalance of purine metabolism in hepatomas of different growth rates as expressed in behavior of glutamine-phosphoribosylpyrophosphate amidotransferase (amidophosphoribosyltransferase, EC 2.4.2.14).

The behavior of glutamine-phosphoribosylpyrophosphate amidotransferase (amidophosphoribosyltransferase, EC 2.4.2.14) was determined in normal, differentiating, and regenerating liver and in a spectrum of hepatomas of widely different growth rates. The liver and tumor enzymes were measured in 100,000 x g supernatants prepared from 20% tissue homogenates containing 0.25 M sucrose and 1 mM MgC12. Kinetic studies were carried out on the amidotransferase in the curde supernatant from liver and rapidly growing hepatoma 3924A so that under optimum standard assay conditions only the enzyme amount would be the limiting factor. The kinetic results showed that certain properties of the amidotransferase from liver and hepatoma were similar. The liver and hepatoma enzyme exhibited apparent Km's for: glutamine, 1.7 and 2.3 mM; MgC12, 0.7 and 1.1 mM, and phosphoribosylpyrophosphate. S0.5 for 0.9 and 0.4 mM, respectively...

Amidophosphoribosyltransferase↗
PubMedDate not supplied

Biochemical behavior of MC-29 virus-induced transplantable chicken hepatoma.

Studies were performed to test the applicability of the molecular correlation concept developed in chemically induced transplantable rat hepatomas to virally induced transplantable hepatoma in chicken. In a comparison of the activities of carbohydrate, purine, and pyrimidine key enzymes in rat and chicken hepatomas, similar patterns were observed in rodent and avian tumors. These results show that the enzymatic imbalance elucidated in chemically induced rat hepatomas is applicable to the virus-induced hepatoma in chicken, independent of the nature of the carcinogenic agent and the species.

Animals↗
PubMedDate not supplied

Regulation of signal transduction activity in normal and cancer cells.

UNLABELLED: The purpose of this investigation is to clarify critical aspects of the behavior and regulation of signal transduction activity in normal and cancer cells. MATERIALS AND METHODS: Signal transduction activity was determined by measuring the steady-state activity of the three synthetic enzymes involved in the conversion of 1-phosphatidylinositol to IP3, PI 4-kinase, PI 4-phosphate 5-kinase and phospholipase C. These enzymic activities were opposed by the activities of the degradative enzymes, 4-phosphatase and 5-phosphatase. RESULTS: We observed in hepatocellular carcinomas the operation of an integrated imbalance in signal transduction which was manifested in the up-regulation of the steady-state activities of the three synthetic enzymes and in the reduction of the activities of the two catabolic phosphatases. As a consequence of this enzyme imbalance there was an increase in the concentration of IP3 in hepatomas. Increased IP3 levels were also observed in numerous human carcinomas in clinical samples and in tissue culture cells. The signal transduction activity was subject to nutritional regulation and to drug action. The elevated signal transduction activity, as measured by the IP3 concentration, was down-regulated in a time- and dose-dependent fashion by the anticancer drug, tiazofurin, by the flavonoids, quercetin and genistein, and by the anti-estrogen receptor, tamoxifen. CONCLUSIONS: Our studies show that signal transduction activity is stringently linked with transformation and progression in rat and human carcinomas. Down-regulation of signal transduction activity by various drugs led to a marked reduction of IP3 concentration and then to apoptosis and induced differentiation.

Animals↗
PubMedDate not supplied

Evaluation of side effects of platinum complexes (CDDP, CBDCA, CHIP) on rat bone marrow.

The in vivo toxic actions of cis-dichloro-1, 1-cyclo-butane-dicarboxylate platinum (II): carboplatin (CBDCA), cis-diisopropyl-ammine-transdihydroxy-dichloro platinum (IV) and iproplatin (CHIP) were compared with those of cis-diamminedichloroplatinum (II): cisplatin (CDDP) on rat bone marrow. To elucidate the biochemical basis of side effects of platinum analogs, the protein and DNA content, thymidine kinase (TK) EC 2.7.1.21 activity and cellularity (MNC) were measured from the femoral bone marrow at 48 hours after i.v. single injection of these three compounds using equitoxic doses as fraction of LD50 (CDDP: 9, CHIP: 50, CBDCA: 80 mg/kg). Dose response studies showed that each drug depressed in dose dependent fashion the cellularity, DNA content and TK activity. As the I50 values indicated, the CHIP caused the most toxic effect in the bone marrow and the influence of CBDCA was the least. The nadir of biochemical alterations was observed 24-48 hours after drug administration. The recovery of bone marrow was completed 96 hours after the treatment.

Animals↗
PubMedDate not supplied

Comparison of tumor growth inhibitory and toxic effects of a new fluorouracil--nitrosourea derivative (B-3839).

The toxic effect and anti-tumor activity of B-3839, a new molecular combination of pyrimidine antimetabolite 5-fluorouracil (5-FU) with the alkylating agent N-Chloroethyl-N-nitrosourea (BCNU), was compared to that of BCNU and 5-FU given alone and in physical combination. The tumor inhibitory effect of B-3839 was similar to that of BCNU given alone or combined with a low dose of 5-FU in the i.m. Walker tumor model. Furthermore, the bone marrow toxicity of BCNU was not significantly altered by either form of combination with 5-FU. The intestinal side effects, evaluated by measuring the decrease of marker enzyme (thymidine kinase, xanthine oxidase, alkaline phosphatase, sucrase, maltase) activities in isolated enterocytes, were dose-dependent and moderate. A significant, more than 30%, decrease occurred only if BCNU and 5-FU were given simultaneously or as B-3839. The molecular combination of the two drugs does not provide any additional advantage over their physical combination.

Animals↗
PubMedDate not supplied

Enzymological and morphological changes in rat intestinal mucosa following treatment with alkylating sugar alcohol derivatives.

Wistar rats were treated with alkylating sugar alcohol derivatives, dianhydrogalactitol (DAG) and diacetyldyanhydrogalactitol (Diac-DAG), respectively. The drugs were intravenously administered as a single, bolus injection. The applied doses 2.5, 5, 10, 17 mg/kg DAG and 5, 10, 20, 40 mg/kg Diac-DAG were roughly equitoxic. The effect of these cytostatic agents was studied on the different marker enzymes (thymidine kinase, xanthine oxidase, alkaline phosphatase, sucrase, maltase) of the separated mucosa cells derived from the functional and proliferating zone of the small intestine. Both DAG and Diac-DAG inhibited the enzyme activities of the proliferating and mature enterocytes in a dose dependent fashion, primarily acting on the crypt specific thymidine kinase. The time dependent sequence in the biochemical alterations correlated well with the cytomorphological changes. The drug-induced damage was most pronounced 48 hours after a single treatment. The regeneration of the intestinal mucosa began on days 3 and 4 and was completed by day 7. Diac-DAG at equimolar concentration proved to be more toxic than DAG on the intestine as judged by the significantly higher decrease of protein content and xanthine oxidase activity.

Animals↗
PubMedDate not supplied

Molecular mechanisms in the antiproliferative action of taxol and tiazofurin.

The molecular antiproliferative effects of taxol and tiazofurin were studied in human K562 leukemia, and in MCF-7 breast and OVCAR-5 ovarian carcinoma cell cultures. A single treatment with taxol (2 to 100 nM) or tiazofurin (5 to 20 microM) on K562 leukemia cells resulted in both a differentiation program and apoptosis in the same cell culture. Tiazofurin proved to be the most potent inducer of differentiation among the inducers, however, taxol had a major impact on induction of the alterations characteristic of apoptosis. The antiproliferative effect of tiazofurin was mediated by 37 to 85% inhibition of IMP dehydrogenase activity. Both the differentiation and apoptosis induced by tiazofurin were dependent on GTP supply. The induction of differentiation and/or apoptosis was mediated by downregulation of c-myc and Ki-ras oncogenes in all three cell lines treated with tiazofurin (by 2 hr) or taxol (by 24 hr). Combined treatments with tiazofurin and taxol exerted a schedule-dependent, antiproliferative interaction in the cell lines studied. Synergistic inhibition of cell proliferation was observed when cells were pretreated with tiazofurin (10 to 15 microM) for at least 12 hr, then taxol (5 to 15 nM) was added.

Antineoplastic Agents↗
PubMedDate not supplied

Increased signal transduction activity and down-regulation in human cancer cells.

The purpose of this study was to elucidate the behavior of signal transduction activity in rat and human carcinoma cells. Signal transduction activity was measured by the steady-state activity of the three enzymes involved in the conversion of 1-phosphatidylinositol (PI) to IP3, PI 4-kinase, PI 4-phosphate 5-kinase, and phospholipase C activities were measured by our methods. The results indicate that the steady-state activities of the three signal transduction enzymes and the end-product, IP3, were up-regulated in a transformation- and progression-linked fashion. In rat liver PI kinase, PIP kinase and PLC activities were 0.4, O.04, and 800 nmol/hour/mg protein, respectively. PI and PIP kinase and PLC activities were increased 2- to 8-fold in five rat hepatomas and 29-, 45-, and 4-fold, respectively, in rapidly growing hepatoma 3924A. PI and PIP kinase activities as compared to normal ovary were elevated in human ovarian epithelial carcinomas (4- and 3-fold) and in OVCAR-5 cells in culture (31- and 11-fold). Compared to normal breast parenchymal cells, PI and PIP kinase activities were increased in human breast carcinoma cells (96- and 16-fold). When breast carcinoma cells were plated and expressed their neoplastic proliferative program. IP3 concentration increased 20-fold in early log phase: PI and PIP kinase activities increased 11-fold in mid log phase: PLC activity did not change throughout. PI and PIP kinase activities in bone marrow had short half-lives (t1/2 = 8 minutes) but PLC had a long one (t1/2 > 6 hours). The elevated signal transduction activity was down-regulated by the anti-cancer drug, tiazofurin, and also by quercetin, an inhibitor of PI kinase. The addition of these drugs to cultured carcinoma cells reduced the IP3 concentration, and the cells were killed. These integrated studies are the first showing that signal transduction activity is stringently linked with transformation and progression in rat and human solid tumors and carcinoma cells. Down-regulation (by tiazofurin) or inhibition of PI and PIP kinase activities (by quercetin) in human carcinoma cells led to a marked reduction of IP3 concentration and to cell death. Tiazofurin and quercetin may be useful in the treatment of carcinomas with increased signal transduction capacity.

1-Phosphatidylinositol 4-Kinase↗
PubMedDate not supplied

Tiazofurin: molecular and clinical action.

UNLABELLED: The purpose is to provide an overview of the molecular and clinical impact of tiazofurin. METHOD: The biochemical and clinical techniques were reported (1, 2). RESULTS: IMP DH activity increased in various animal and human tumors and was particularly high in leukemic blast cells. The increased activity was due to an elevation in the mRNA concentration of type II isozyme. Tiazofurin, a C-nucleoside, was converted in sensitive cells to the active metabolite, TAD, which tightly bound at the NADH site inhibited IMP DH activity. The inhibition led to decreased GTP concentration, down-regulation of ras and myc oncogenes and induced maturation of blast cells. New evidence shows that tiazofurin injection downregulated signal transduction activity due to a reduction of the activities of PI and PIP kinases leading to a decrease in the concentration of the second messenger, IP3. In patients; tiazofurin infusion and allopurinol administration led to reduction of IMP DH activity and GTP concentration. Allopurinol inhibited xanthine oxidase activity leading to a marked rise in hypoxanthine concentration which inhibited the increased guanine salvage pathway. In the clinic, the increase in serum hypoxanthine concentration is essential for the success of tiazofurin treatment. Tiazofurin showed additivity or synergism with ribavirin, retinoic acid, taxol, quercetin, gemcitabin, dipyridamole and brefeldin. Ribavirin which inhibits IMP DH at the IMP site has been shown to prolong the IMP depressing action of tiazofurin in rat bone marrow cells. CONCLUSION: Tiazofurin and allopurinol achieve reduction of GTP concentration in leukemic blast cells through inhibition of IMP DH and GPRT activities. As a result, induced maturation occurs with down-regulation of ras and myc oncogenes and probably reduced signal transduction capacity. Tiazofurin in leukemic patients provides over 75% therapeutic responses and patients can be treated with this combination for many months with good quality of life. These clinical and biochemical results were recently confirmed independently (3).

Allopurinol↗
PubMedDate not supplied

Increased thymidine kinase and thymidylate synthase activities in human epithelial ovarian carcinoma.

BACKGROUND: Thymidylate synthase (dTMP synthase, EC 2.1.1.45) is responsible for the de novo biosynthesis of thymidylate (dTMP) whereas thymidine kinase (TdR kinase, EC 2.7.1.21) is the salvage enzyme which leads to the production of dTMP even in presence of d TMP synthase inhibition. The current study was undertaken to compare the steady-state activities of d TMP synthase and TdR kinase in extracts of human epithelial ovarian carcinoma and normal ovaries. MATERIAL AND METHODS: Tissue extracts of epithelial ovarian carcinomas and normal ovaries were analyzed for activities of d TMP synthase (by a method that measures released 3H2O) and TdR kinase (by polyethyleneimine impregnated (PEI) cellulose plate radioassay), methods established in this laboratory. RESULTS: The dTMP synthase activity (mean +/- S.E.) in extracts of ovarian carcinomas (N = 11) was 0.198 +/- 0.069 and in extracts of normal ovaries (N = 12) it was 0.025 +/- 0.0004 nmol/hr/mg protein. By contrast, TdR kinase activity in extracts of ovarian carcinoma (N = 13) was 27.7 +/- 8.5 compared to 1.0 +/- 0.3 nmol/hr/mg protein in extracts of normal ovaries (N = 15). CONCLUSION: The observed 140-fold higher TdR kinase activity suggests that DNA synthesis may continue despite inhibition of dTMP synthase with current schedules of 5-fluorouracil (5-FU) and leucovorin. The addition of azidothymidine, a competitive inhibitor of TdR kinase, to 5-FU and leucovorin might be a rational biochemical strategy to employ in patients with refractory ovarian carcinoma.

Adult↗
PubMedDate not supplied

Intracellular signalling: phosphatidylinositol lipid metabolism in cancer cells.

Evidence for heightened capacity for signal transduction in rat hepatoma as well as in human breast and ovarian carcinoma cells as reflected by coordinate increases in PI kinase and PIP kinase in the PI phosphorylation sequence leading to the production of second messengers IP3 and DAG is shown. The linkage of signal transduction enzymes with malignant growth is also seen as MDA-MB- 435 human breast carcinoma or ovarian OVCAR-5 cells express their proliferative capacity in tissue culture in the log phase. In both cases, quercetin inhibit cell proliferation with a decline in PI kinase activity and IP3 levels preceding the growth inhibition seen with quercetin. The elevated steady state activities of PI and PIP kinase indicate a metabolic up-regulation in signal transduction capacity of cancer cells which is down-regulated by quercetin. Since the gain in function manifested in the over-expressed capacity for signal transduction confers selective growth advantage to cancer cells, increased activities of PI and PIP kinases may be considered as sensitive targets for cancer chemotherapy. The potential of quercetin as an interceptor of intracellular signal transduction mechanisms needs to be explored.

1-Phosphatidylinositol 4-Kinase↗