Biomedical subjects

U Bachrach

Publications and source records attributed to U Bachrach.

At least 19 recordsLinked to original sources

PubMed2004

Polyamines and cancer: minireview article.

The naturally occurring polyamines, spermine, spermidine and the diamine putrescine are widespread in nature. They have been implicated in growth and differentiation processes. Polyamines accumulate in cancerous tissues and their concentration is elevated in body fluids of cancer patients. Assays of urinary and blood polyamines have been used to detect cancer and to determine the success of therapy. Drugs which inhibit the synthesis of polyamines can prevent cancer and may also be used for therapeutic purposes. Ornithine decarboxylase, which catalyzes the rate limiting step in polyamine synthesis, can serve as a marker of proliferation. Recently, a new in vitro chemosensitivity test, based on the disappearance of ornithine decarboxylase in drug-treated cancer cells has been developed. The increasing interest in polyamines and their physiological functions may lead to a more extensive application of these compounds or their derivatives in cancer diagnosis and treatment.

Antineoplastic Agents↗

PubMed2002

The specific anti-cancer activity of green tea (-)-epigallocatechin-3-gallate (EGCG).

The effect of the green tea polyphenol-(-)epigallocatechin-3-gallate (EGCG) was tested in cultures of normal and transformed NIH-pATM ras fibroblasts. In this system transformation can be induced at will by the addition of dexamethasone, which induces the expression of H- ras by activating the mammary tumor virus long terminal repeat (MMTV-LTR) promoter. This facilitates a reliable comparison of the susceptibility of normal and transformed cells to EGCG. It has been shown that EGCG inhibited the growth of transformed but not of the normal fibroblasts. In an attempt to elucidate the mode of the preferential inhibitory activity of EGCG, its effect on growth promoting factors has been examined. The level of ornithine decarboxylase (ODC, EC 4.1.1.17), which is a signal for cellular proliferation, was reduced by EGCG in the transformed but not in the normal cells. EGCG also showed strong inhibition of tyrosine kinase and mitogen-activated protein kinase (MAPK) activities, without affecting the kinases in the normal cells. Similarly, EGCG also preferentially decreased the levels of the oncogenes Ras and Jun in transformed cell. EGCG preferentially induced apoptosis in the transformed fibroblasts. In vitro chemosensitivity tests demonstrated that EGCG inhibited the proliferation of leukemic cells. These findings suggest that EGCG has a therapeutic potential in the combat against cancer.

3T3 Cells↗

PubMed2002

Cancer therapy and prevention by green tea: role of ornithine decarboxylase.

Green tea which is widely consumed in China, Japan and India, contains polyphenolic compounds, which account for 30% of the dry weight of the leaves. Most of the polyphenols are flavanols, of which (-)-epigallocatechin-3-gallate (EGCG) is most abundant. Epidemiological studies revealed that the incidences of stomach and prostate cancers are the lowest in the world among a population that consumes green tea on a regular basis. It has also been reported that the quantity of green tea consumed, plays an important role in reducing cancer risk and in delaying cancer outbreak and recurrence. Various systems were used to confirm anti-cancer activities of green tea and/or EGCG. These included experimental animals in which cancer was induced chemically. Cultured cells transformed chemically or by oncogenes were also used. These studies clearly demonstrated that green tea or EGCG have anticancer and cancer preventive properties. The mechanisms of these activities have also been studied in details. It has been shown that green tea and its active components interfere with signal transduction pathways. Thus the activities of various protein kinases are inhibited, the expression of nuclear proto-oncogenes declines and the activity of ornithine decarboxylase (ODC) is reduced. ODC, which catalyzes the rate-limiting step in the biosynthesis of polyamines is closely linked with cellular proliferation and carcinogenesis. Inhibitors of ODC, like alpha-difluoromethylornithine (DFMO) have long been used for cancer prevention and therapy. It has been suggested that polyamine depletion by green tea could offer one explanation for its anti-cancer activities.

Humans↗

PubMed2001

Polyamines: new cues in cellular signal transduction.

The naturally occurring polyamines putrescine, spermidine, and spermine are involved in signal transduction. This has been demonstrated by using inhibitors for polyamine biosynthesis (such as alpha-difluoromethylornithine) or adding polyamines to cultured cells. Different polyamines, preferentially activated protein kinases (tyrosine kinases and MAP kinases), stimulated the expression of nuclear protooncogenes (myc, jun, and fos).

Animals↗

PubMed2000

A luminescence-based test for determining ornithine decarboxylase activity.

A sensitive chemiluminescence-based method for the assay of ornithine decarboxylase (ODC) has been developed. This method, which permits the detection of putrescine (the product of ODC) at a picomolar range, can be used to determine ODC activity in cellular extracts. Extracts are incubated with ornithine and spotted onto p81 phosphocellulose paper strips. After drying, the papers are washed with ammonium hydroxide to remove contaminants, which may interfere with the assay. Putrescine is next eluted from the paper by shaking in an elution buffer containing magnesium sulfate. Partially purified hog kidney diamine oxidase is then used to oxidize putrescine in the eluate. The hydrogen peroxide formed during the oxidation is determined by chemiluminescence using luminol and peroxidase. This simple analytical method has the sensitivity of conventional assays based on the use of radioactive ornithine.

3T3 Cells↗

PubMed2000

Effects of testosterone and 17, beta-estradiol on the polyamine metabolism in cultivated normal rat kidney epithelial cells.

Ornithine decarboxylase (ODC) and diamine oxidase (DAO) are important enzymes involved in the metabolism of polyamines (putrescine, spermidine and spermine). The influence of testosterone (T) and 17, beta-estradiol (E2) on the activity of ODC and DAO was examined in cultivated normal rat kidney (NRK) epithelial cells. The results showed an increase in enzyme activities 4 hours or 12 hours after hormonal treatment. Both T and E2 led to a significant increase (1.6-fold) in ODC protein level as compared to the controls. Cellular concentration of spermidine and spermine increased (2.2- and 2.6-fold respectively) 4 hours after T addition. A higher levels in concentrations of putrescine (1.4-fold) and spermine (1.5-fold) 12 hours after E2 treatment were observed. These results suggest that the biosynthesis and terminal oxidation of the polyamines in NRK epithelial cells are androgen- and estrogen-mediated and depend on the hormonal sensitivity of the cells.

Amine Oxidase (Copper-Containing)↗

PubMed1999

Developmental aspects of polyamine-oxidizing enzyme activities in the mouse kidney. Effects of testosterone.

In the present study developmental patterns of renal polyamine-oxidizing enzymes polyamine oxidase (PAO) and diamine oxidase (DAO) in male and female ICR mice were demonstrated. The effects of testosterone (10 micrograms/100g body weight) on renal PAO and DAO activities were also studied. The differences between sexes in both PAO and DAO activities were most clearly expressed in the immature kidney. At the age of 20 days PAO and DAO activities were 1.52 fold (p < 0.01) and 1.75 (p < 0.02) respectively higher in male mouse kidney than in female. Maturational processes reflected in significant increases in polyamine-oxidizing enzyme activities mainly in female mouse kidney, comparable with the gain in the kidney wet weight. Our data show that testosterone is able to influence renal PAO and DAO activities in addition to the well-known stimulation of polyamine biosynthesis. The hormonal effects were sex and age dependent. The influence of testosterone on renal PAO activity was mainly age dependent. The slight stimulation of renal PAO activity observed in 20- and 50-day old mice, 24 h after testosterone administration, change with a decrease in the enzyme activity at the age of 70 days. The effects of testosterone on renal DAO activity were mainly sex dependent. Testosterone caused stimulation of DAO activity with a very close magnitude (nearly twice) in female mouse kidney, independently of the age of mice. In contrast, in male mice the hormone treatment resulted in a statistically significant increase in renal DAO activity at the age of 70 days (1.3 fold, p < 0.05) only. It could be suggested that our data indicate the different contribution of renal PAO and DAO in androgen regulation of polyamine levels, depending on sex and the stage of the postnatal development.

Amine Oxidase (Copper-Containing)↗

PubMed1999

Role of polyamines in mediating malignant transformation and oncogene expression.

3T3 Cells↗

PubMed1999

In vitro chemosensitivity testing of hematological cancers: immunohistochemical detection of ornithine decarboxylase.

A new method for in vitro chemosensitivity testing of human lymphoma and leukemia patients has been developed. The method is based on the use of ornithine decarboxylase (ODC), a universal marker of proliferation, which is expressed early during the cell cycle and has a short half-life. This marker was detected by a quantitative immunohistochemical analysis, using an ODC antibody and a FITC-linked second antibody. The in vitro chemosensitivity of lymphocytes from four normal individuals was tested by the immunohistochemical method. Lymphocytes from 25 cancer patients were also examined. In drug-sensitive cells, the intensity of the marker declined in the presence of the drug, whereas resistance to the drug was demonstrated by the presence of the marker. A good correlation was found between the predicted chemosensitivity and the outcome of the therapy. It has been suggested that this approach could be used for in vitro chemosensitivity testing of hematological cancers and most likely also for other malignancies.

Adult↗

PubMed1998

Polyamines induce malignant transformation in cultured NIH 3T3 fibroblasts.

Previous studies have demonstrated that polyamines accumulate in cancer cells and that overproduction of ornithine decarboxylase (ODC), which catalyzes polyamine synthesis, elicits the acquisition of the transformed phenotype. However, it was not clear whether the overexpression of ODC and the accumulation of polyamines are only innocent by-products of the transformation process. In this study we demonstrate that polyamines as such, may play a crucial role in malignant transformation. The system used consisted of NIH 3T3 fibroblasts transfected with a construct (pATMras) in which Ha-ras was under the transcriptional control of the mouse mammary tumor virus long terminal repeat (MMTV-LTR) promoter (MMTVras cells). Dexamethasone, which activates the promoter, triggered phenotypic transformation. This was accompanied by an increase in ODC activity and polyamine accumulation. Cells, thus transformed, grew in soft agar and formed typical foci. alpha-Difluoromethylornithine (DFMO), which blocks polyamine synthesis, inhibited the dexamethasone-enhanced transformation. This inhibition was reversed by polyamines. Polyamines caused transformation of MMTVras cells in the absence of dexamethasone. Under these conditions, cells became anchorage independent. This phenomenon is not explained by the leakiness of ras, since normal, immortalized NIH 3T3 fibroblasts, also grew in soft agar in the presence of polyamines. Taken together, these observations suggest that polyamines may stimulate malignant transformation of immortalized cells, in cooperation with other factors, such as oncogenes or genetic defects.

3T3 Cells↗

PubMed1995

Ornithine decarboxylase: an indicator for growth of NIH 3T3 fibroblasts and their c-Ha-ras transformants.

Growth rates of different clones, all derived from NIH 3T3 mouse fibroblasts, were determined. Four different types of cells were studied: (1) Normal NIH 3T3 fibroblasts; (2) a fast-growing NIH 3T3 clone obtained by repeated passages; (3) transformed clones (obtained by transfecting NIH 3T3 with the oncogene c-Ha-ras); (4) a slow-growing revertant obtained by repeated passages of the transformed line. Growth rates were determined by the following markers of proliferation: thymidine incorporation, protein accumulation and cell number. In parallel experiments growth rates were determined by a new approach based on measuring ornithine decarboxylase (ODC) activity. Transformed cells, which were characterized by phase-contrast microscopy and by electron microscopy grew rapidly and showed high ODC activity. Similarly, a high-passage NIH 3T3 variant, which grew rapidly, also possessed high ODC activity. On the other hand, high-passage of a transformed clone revealed phenotypic changes confirmed by electron microscopy. These cells exhibited reduced growth rates and their ODC activities were similar to those of the normal NIH 3T3 cells. A confident correlation was found among each of the three conventional parameters of growth and between them and ODC activity. However, in all the cases studied ODC activity appeared early in the cell cycle before the expression of the other markers of proliferation. It has been suggested that ODC is a reliable early marker of cell proliferation and might also serve as an important tool for determining the arrest of growth.

3T3 Cells↗

PubMed1994

Activation of the proto-oncogene c-myc and c-fos by c-ras: involvement of polyamines.

Rat kidney cells infected with a temperature-sensitive mutant of Kirsten sarcoma virus (Ki-MSV ts 371) expressed Ki-Ras at 37 degrees C but not at 42 degrees C. This expression of the oncogene was accompanied by an increase in the activity of ornithine decarboxylase (ODC) and the accumulation of putrescine. Elevation of cellular polyamine content triggered the transcription of c-myc and c-fos. alpha-Difluoromethylornithine, a specific inhibitor of ODC, prevented the transcription of c-myc in cells grown at 37 degrees C. Putrescine, at physiological concentrations, triggered the transcription of c-myc and c-fos in cells grown at 42 degrees C, when Ki-ras was not expressed. It has been suggested that polyamines participate in a cascade of events leading to the communication between membrane-bound and nuclear oncogene products. These findings may attribute a new function to the naturally occurring polyamines.

Animals↗

PubMed1994

Determination of multidrug resistance levels in cultured mammalian cells using ornithine decarboxylase activity.

We describe an ornithine decarboxylase (ODC) activity-based assay for the quantitation of multidrug resistance (MDR) and its reversal by MDR modulators in cultured mammalian cells. ODC catalyzes the first and rate-limiting step in polyamine biosynthesis. The activity of this enzyme rises rapidly after growth initiation, such as after addition of serum-containing medium to quiescent mammalian cells. This increase in enzyme activity is prevented when growth is arrested, such as after treatment with cytotoxic drugs. In this assay cultures of drug-sensitive animal and human carcinoma cells as well as their MDR sublines were exposed to various concentrations of different cytotoxic agents for 6-48 h. A dose-dependent decrease in ODC activity was obtained with a variety of chemotherapeutic agents including anthracyclines, vinca alkaloids, epipodophyllotoxins, actinomycin D, antifolates, and cisplatinum. Anticancer drug resistance levels were calculated as the 50% inhibitory concentration of ODC activity obtained with drug-resistant cells divided by that obtained with sensitive cells. These cytotoxicity determinations correlated favorably with those obtained by the well-established colony formation assay. The ODC assay also proved useful in the assessment of MDR reversal with modulators of the MDR phenotype. Therefore, these studies show that the ODC assay could be useful for the reliable determination of drug resistance levels in cultured mammalian cells and for the assessment of drug resistance reversal by various modulators of the MDR phenotype.

Animals↗

PubMed1994

Immunohistochemical detection of ornithine decarboxylase in individual cells: potential application for in vitro chemosensitivity assays.

Ornithine decarboxylase (ODC), which catalyzes the rate-limiting step in the biosynthesis of polyamines, can serve as a marker of proliferation. The presence of ODC protein in individual cells was quantitatively detected by an immunofluorescence assay using an ACAS 570 computerized fluorescence microscope. ODC was detected in KB-3-1 human epithelial carcinoma cells grown in the absence of any drug. Vinblastine, which inhibits cell growth, caused the disappearance of ODC. On the other hand, ODC was detected in multidrug-resistant cells grown in the absence or in the presence of vinblastine. NIH 3T3 fibroblasts transformed by the c-Ha-ras oncogene also contained ODC protein. This protein disappeared when the cells were treated with cycloheximide, which inhibits cell proliferation. These findings suggest that ODC can be detected in individual cells by immunofluorescence. Whether this method can be used for in vitro chemosensitivity tests remains to be studied.

3T3 Cells↗

PubMed1994

Ornithine decarboxylase--a predictor for tumor chemosensitivity.

The activity of ornithine decarboxylase (ODC) was determined in P388 murine leukemia cells treated with adriamycin (ADR) and methotrexate (MTX). Some of the cell lines were resistant to ADR, MTX or their combinations. A similar pattern was found between the cytotoxicity and the suppression of ODC activity in these cell lines in terms of drug concentrations. In a cell line resistant to one drug, a relatively high concentration of that drug was required to inhibit ODC activity. This effect was independent of the sensitivity of the cells to the other drug. A similar correlation between arrest of growth and the inhibition in the induction of ODC was also observed in human epithelial carcinoma cells. In this case too, the growth of multidrug resistant cells was not affected by vinblastine, neither was the induction of ODC. On the other hand, both the growth and the induction of ODC were inhibited by vinblastine in drug-sensitive cells. These findings suggest that ODC measurements might be used for predicting the chemosensitivity of tumor cells.

Animals↗

PubMed1992

Polyamines as markers of malignancy.

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Animals↗

PubMed1992

Changes in brain polyamine levels following head injury.

The changes in polyamines levels in the brain after closed head injury were studied in rats. At 1 and 15 min, 24 and 48 h after closed head injury cortical tissue from the site of injury, from the contralateral region, and from remote areas were taken. The levels of the diamine putrescine and the polyamines spermine and spermidine were assayed by thin layer liquid chromatography of their dansyl derivatives. Head injury induced a significant increase in putrescine at 48 h at the site of injury and in the frontal lobe of the injured hemisphere, respectively. In the contralateral hemisphere only minor changes in putrescine were found. Spermine and spermidine showed minor changes at that time course. We have previously shown that at 24-48 h after injury, severe edema is found at the site injury. In order to study the role of putrescine in edema formation in this model we treated the traumatized rats with alpha-difluoromethyl-ornithine (DFMO), an inhibitor of ornithine-decarboxylase, the rate limiting enzyme in putrescine biosynthesis. This drug did not affect the level of edema 4 or 48 h after injury although it abolished the increase in putrescine. The effect of DFMO on blood-brain barrier function was studied, using Evans blue extravasation, at the early post-traumatic period (15 min-4 h), where a massive amount of dye is taken up by traumatized brain. No changes in the amount of dye extracted was found after DFMO treatment. On the other hand, DFMO had a beneficial effect on the neurological outcome, as evaluated by a set of clinical criteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Effect of polyamines on the activity of malarial alpha-like DNA polymerase.

DNA polymerase from the malarial parasite Plasmodium falciparum required Mg2+ for activity, Putrescine (1 mM) caused a twofold increase in enzyme activity in the presence of a suboptimal concentration of MgCl2 (2 mM). Spermidine (1.5-2.0 mM) or spermine (0.1-0.3 mM) increased the activity of malarial DNA polymerase, in the presence of 2 mM MgCl2, by factors of 6 and 3-5, respectively. The activity of DNA polymerase from calf thymus or from NIH 3T3 cells transformed by the ras oncogene were not stimulated by these polyamines to the same extent. These findings suggest that in malaria-infected erythrocytes, polyamines, at physiological concentrations, serve as a cofactor for the parasitic alpha-like DNA polymerase. Malarial parasites grown in cultured human erythrocytes did not synthesize DNA after treatment with alpha-difluoromethylornithine, which caused polyamine depletion in the infected cells. DNA synthesis was resumed after adding putrescine to the polyamine-depleted cultures. DNA synthesis was also initiated when actinomycin D was added along with putrescine to polyamine-depleted cells. It thus appears that polyamines are essential for the translation of the DNA polymerase mRNA and that polyamines play an important role in regulating the cell cycle of the malarial parasite.

Animals↗