Differential effect of interferon on ornithine decarboxylase activation in quiescent Swiss 3T3 cells

Mechanism of synergistic action of all-trans- or 9-cis-retinoic acid and interferons in breast cancer cells

Combination of all-trans-retinoic acid (RA) with either interferon-alpha or -gamma resulted in a synergistic amplification of the anti-proliferative effect on cultured breast cancer cells. RA could be replaced by other biologically active retinoids. The synergism was also observed for the induction of 2'-5'-oligoadenylate synthetase, an enzyme which is involved in anti-viral activity of interferons and possibly in growth regulation of tumor cells. Combination of RA with interferon-gamma increased the down-regulation of specific binding sites for [125I]interferon-gamma. On the other hand interferons had no effect on the cytoplasmic binding protein for RA. Comparing all-trans- with 9-cis-RA, the latter was more effective in inhibiting tumor cell growth and in inducing synergism with interferon-gamma. This would indicate that retinoic X receptors are more important in mediating these effects than the RA receptors (RARs). This assumption is also supported by the failure of Ro-415253, a specific RAR-alpha antagonist, to reduce the synergistic interaction of RA with interferon with respect to growth inhibition.

Effects of retinoids and interferon-gamma on cultured breast cancer cells in comparison with tumor necrosis factor alpha

The combination of retinoic acid or tumor necrosis factor alpha (TNF-alpha) with interferon gamma (IFN-gamma) resulted in a synergistic amplification of the anti-proliferative effect of IFN-gamma on cultured breast cancer cells. Retinoic acid could be replaced by other biologically active retinoids. This synergism was also observed for the induction of 2'-5'-oligoadenylate-synthetase, an enzyme which is not expressed constitutively on BT-20 human breast cancer cells and not inducible by retinoic acid or TNF-alpha alone. However, both substances augmented the IFN-gamma-mediated expression. On the other hand, only TNF-alpha and not retinoic acid was able to increase the IFN-gamma induced expression of HLA-DR on the cell surface. Both cytokines antagonized the IFN-gamma effect on detachability of cultured BT-20 cells. The combinations of retinoic acid with IFN-gamma increased the down-regulation of specific binding sites for 125I-IFN-gamma. On the other hand, IFN-gamma exerted no effect on the concentration of the cytoplasmic binding protein for retinoic acid. Data obtained in this study demonstrate a different pattern of action between retinoic acid and TNF-alpha regarding their synergism in combination with IFN-gamma.

Hyperthermia and polyamine biosynthesis: decreased ornithine decarboxylase induction in skin and kidney after heat shock

The effect of hyperthermia treatments on ornithine decarboxylase (ODC) induction in mouse tissue was determined both in vitro and in vivo. In vitro, the addition of 12-0-tetradecanoylphorbol-13-acetate (TPA) to adult mouse skin pieces incubated at 37 degrees C in serum-free MEM led to a dramatic increase in epidermal ODC activity 5 hours following treatment. In contrast, incubation temperatures of 40 degrees C for the entire 5 hour incubation period rendered the skin pieces unresponsive to TPA for ODC induction. This inhibition of ODC induction was not the result of thermal skin kill, inactivation of TPA, or a general effect on epidermal protein synthesis. The inhibition of ODC induction could be reversed by switching the incubation temperature back to 37 degrees C. In vivo, raising the core body temperature in male mice to 41 degrees C for 1 hour resulted in a 78% decrease in kidney ODC activity. The kidney DNA synthesis and protein synthesis remained unaltered following the whole body hyperthermia treatments.

The effects of treatment with human beta-interferon on the stimulation of thymidine uptake and DNA synthesis by colchicine in human fibroblasts

The marked inhibition by beta-interferon (IFN) of colchicine-induced incorporation of [3H]-thymidine into DNA of human fetal lung fibroblasts reflects inhibition of uptake of labeled precursor, rather than an effect on DNA synthesis per se. The percent of cells in S phase as measured with flow cytometry was unchanged by a concentration of IFN that reduced the uptake of labeled thymidine by 50% at 30 h after treatment.

Magnitude of ornithine decarboxylase induction by epidermal mitogens: effect of the assay technique

The polyamines, putrescine, spermidine and spermine, as well as ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine biosynthesis, are increased in the blood, urine and skin of psoriasis patients. A study of the association between stimulated epidermal cell proliferation and induction of ODC activity was done using both an intact, living cell ODC assay and the routinely used homogenized cell supernate assay. 10(-6) to 10(-8) mol/l of the tumor promoter, tetradecanoyl phorbol acetate (TPA), 10(-3) mol/l 8-BrcAMP, 10(-6) mol/l cholera toxin and 10(-3) mol/l MIX, which are epidermal cell mitogens, were used to stimulate basal cells in short-term suspension cultures, freshly plated monolayers, or up to 8-day-old cultures. The results showed that the ODC enzyme must be assayed in supernates from disrupted epidermal cells in order for significant ODC induction by hyperplastic agents to be observed.

Inhibition of ornithine decarboxylase in human fibroblast cells by type I and type II interferons

Dilution of human fibroblast GM2767 cell cultures into fresh serum-containing growth medium induces ornithine decarboxylase activity 45-fold over a six-hour interval. When the fibroblast cultures are supplemented with human fibroblast alpha-, beta-, or gamma-interferon at the time of dilution into fresh growth medium, the induction of ornithine decarboxylase is inhibited 61%, 90%, and 65%, respectively. beta-Interferon is the most effective type of interferon to inhibit induction of ornithine decarboxylase.

Detection of ornithine decarboxylase antizyme in mouse brain

Ornithine decarboxylase, the rate-limiting enzyme in polyamine synthesis, is known to be regulated by a macromolecular inhibitor, termed antizyme, in a number of cellular systems. The present results show that the antizyme is also a functional component of polyamine metabolism in the brain. It could be demonstrated both in normal randomly selected mice and in animals which had been subjected either to intracerebroventricular injection of saline, which is known to cause a transient activation of ornithine decarboxylase, or to 1,3-diamino-2-propanol, an antizyme-inducing agent. When compared to tissues or cell systems studied so far, the cytosol fraction from mouse brain homogenate appeared to contain an exceptionally high amount of antizyme, that was bound to some material other than active ornithine decarboxylase. This feature was seen in all the animal groups studied, being most prominent after saline injection, when the amount of dissociable antizyme exceeded 14-fold the corresponding released ornithine decarboxylase activity. In untreated animals the excess was about eightfold and after 1,3-diamino-2-propanol about fivefold.

Phosphorylation of ornithine decarboxylase by a polyamine-dependent protein kinase

This paper presents evidence that a polyamine-dependent protein kinase (EC 2.7.1.37) purified from nuclei of the slime mold Physarum polycephalum catalyzes phosphorylation of ornithine decarboxylase (OrnDCase; L-ornithine carboxy-lyase, EC 4.1.1.17). The protein kinase had properties similar to OrnDCase antizyme. Phosphocellulose chromatography of nuclear preparations from P. polycephalum yielded the polyamine-dependent protein kinase of subunit Mr 26,000 that was resolved from a second fraction in which the protein kinase copurified with a phosphate-acceptor protein of subunit Mr 70,000. At Na+ concentrations less than approximately 150 mM, a complex formed between the protein kinase and the phosphate-acceptor protein. The complex did not demonstrate protein kinase or OrnDCase activity. The complex was dissociated by greater than 150 mM Na+ into its constituent proteins. The dissociated complex catalyzed phosphorylation of the Mr 70,000 component in the presence of spermidine and spermine, and it also demonstrated OrnDCase activity. The purified Mr 70,000 component from the complex and authentic OrnDCase, purified by procedures previously reported, were virtually identical with respect to OrnDCase activity, capacity to be phosphorylated by the polyamine-dependent protein kinase, amino acid composition, and immunological crossreactivity. Phosphorylation of OrnDCase by the polyamine-dependent protein kinase sharply inhibited OrnDCase activity. Thus, this is an example of posttranslational covalent modification of OrnDCase with concurrent alteration of its catalytic function. It is also an unusual example of control of the first enzyme in a biosynthetic pathway by a protein kinase that is, in turn, modulated by the immediate end products of the pathway.