Resveratrol: a review of preclinical studies for human cancer prevention

The search for novel and effective cancer chemopreventive agents has led to the identification of various naturally occurring compounds one of which is resveratrol (trans-3,4',5-trihydroxystilbene), a phytoalexin derived from the skin of grapes and other fruits. Resveratrol is known to have potent anti-inflammatory and antioxidant effects and to inhibit platelet aggregation and the growth of a variety of cancer cells. Its potential chemopreventive and chemotherapeutic activities have been demonstrated in all three stages of carcinogenesis (initiation, promotion, and progression), in both chemically and UVB-induced skin carcinogenesis in mice, as well as in various murine models of human cancers. Evidence from numerous in vitro and in vivo studies has confirmed its ability to modulate various targets and signaling pathways. This review discusses the current preclinical and mechanistic data available and assesses resveratrol's anticancer effects to support its potential as an anticancer agent in human populations.     

Radiosynthesis of N5‐[18F]fluoroacetylornithine (N5‐[18F]FAO) for PET imaging of ornithine decarboxylase (ODC) in malignant tumors

Polyamines are naturally occurring polycations derived from amino acids via decarboxylation by ornithine decarboxylase (ODC). Ornithine is a substrate for ODC; decarboxylation of ornithine is inhibited by difluoromethylornithine (DFMO) and its derivatives. Polyamine contents are increased in many epithelial cancers, including breast cancer, melanoma, and prostate cancer. In order to image and measure the levels of ODC expression in malignant tumors, we have synthesized a derivative of ornithine, N⁵‐[¹⁸F]fluoroacetylornithine (N⁵‐[¹⁸F]FAO), for use in positron emission tomography. The precursor compound N²‐Boc‐N⁵‐bromoacetylornithine‐t‐butyl ester 2 was synthesized from 5‐amino‐2‐(tert‐butoxycarbonylamino)pentanoic acid, which was reacted with bromoacetyl chloride followed by esterification with tert‐butyl‐2,2,2‐trichloroacetamidate. Fluorination of the precursor produced a fluoro‐derivative, which was hydrolyzed in acid to obtain the desired compound, N⁵‐fluoroacetylornithine. The radiosynthesis of N⁵‐[¹⁸F]FAO was accomplished by radiofluorination of 2 with n‐Bu₄N[¹⁸F], followed by high‐performance liquid chromatography (HPLC) purification and then by acid hydrolysis. The radiochemical yield was 6–10% (decay corrected) with an average of 8% (n=10) at the end of synthesis. The radiochemical purity was >99%, and specific activity was >1500 mCi/µmol. The synthesis time was 95–100 min from the end of bombardment. Copyright © 2010 John Wiley & Sons, Ltd.     

Mechanism of allopurinol-mediated inhibition and stabilization of human orotate phosphoribosyltransferase and orotidine phosphate decarboxylase

Allopurinol ribonucleotide and oxipurinol-7-ribonucleotide appeared to be strong inhibitors of orotidine phosphate decarboxylase in human hemolysates. The enzyme exhibited bimodal kinetics. The ribonucleotides of allopurinol and oxipurinol caused an inhibition of orotate phosphoribosyltransferase, which appeared to be due to accumulation of OMP. Inhibition by OMP was competitive with respect to phosphoribosylpyrophosphate with a K_i value of 11 μM. The inhibition of ODC and OPRT activity may cause the increased urinary excretion of orotidine and orotic acid, respectively, observed after allopurinol therapy. Values measured for OPRT activity in intact erythrocytes and in hemolysates agreed very well. Therefore OPRT activity does not decrease during cell lysis and extraction. Hypoxanthine-guanine phosphoribosyltransferase deficiency as well as allopurinol therapy led to a marked increase in OPRT and ODC activities in human hemolysates. In lysates from leukocytes only a slight increase of ODC activity was observed, while OPRT activity did not differ significantly from the controls. In vitro incubations of hemolysates demonstrated a considerable increase of the stability of OPRT by addition of OMP or PRPP and of ODC by addition of OMP, PRPP, UMP and the ribonucleotides of allopurinol and oxipurinol. These findings suggest that the apparent increase of OPRT and ODC activity after allopurinol therapy is due to stabilization of the enzymes during the life span of the erythrocytes.     

Comparison of the neuritogenic activity of cyclic nucleotides and skeletal muscle-conditioned medium on ciliary ganglia in vitro

The parasympathetic ciliary ganglion (CG) of the embryonic chick in vitro, is unresponsive to Nerve Growth Factor and has been reported to form neurites only in response to neurotrophic factors derived from striated muscle or optic tissues. We investigated a possible role of cyclic adenosine-3',5'-monophosphate (cAMP) in the neurotrophic activity of skeletal muscle-conditioned medium (SCM) on CG explants. We showed that treatment with cAMP or dibutyryl cAMP stimulated neuritogenesis of CG explants in a dose-dependent fashion. SCM and cyclic nucleotide stimulation produced distinctly different types of neuritic growth. The growth cones of SCM-stimulated neurites were observed consistently to contact other cells or processes whereas nucleotide-stimulated neurites were not associated with other cells. These observations suggested that the two neuritogenic agents do not act through identical mechanisms, a conclusion supported by experiments demonstrating that stimulation of the CG with dibutyryl cAMP enhanced ornithine decarboxylase (ODC) activity relative to controls, whereas stimulation with SCM had no effect on ODC activity. We conclude that although cAMP does exhibit neuritogenic activity on the CG in vitro, it does not appear to be involved directly in the neurite formation elicited by SCM. It is feasible that the two types of neuritic growth which we described are representative of the two populations of CG neurons. Because only one of these neuronal populations innervates striated muscle in vivo, SCM and cAMP might act on different neurons.     

A radiometric microassay for ornithine decarboxylase

A simple method for purifying [³H]l-ornithine and incubation conditions suitable for estimatingl-ornithine decarboxylase activity are described. Routine and recycled cation exchange procedures for separating putrescine from ornithine are outlined. Blanks using the routine cation exchange method average approx. 0.04% of the radioactivity contained in the substrate; product recovery is approx. 94%. Thel-ornithine decarboxylase assay is proportional to time for at least 8 h. The relationship between substrate purity and the sensitivity of the cation exchange procedures is assessed. Radiochemical purity is the critical determinant of sensitivity for recycled assays. The cation exchange method is compared with the commonly used CO₂-trapping method. The cation exchange method is more specific and approximately three orders of magnitude more sensitive than the CO₂-trapping method.l-Ornithine decarboxylase activity can be measured reliably in samples of embryonic neural tissue having wet-weights of approx. 1 μgl-ornithine decarboxylase activity in the lumbar spinal cord of the chick embryo decreases 25–30 fold from day 5 to day 18 of embryonic development.A cation exchange procedure for estimatingl-lysine decarboxylase activity is also described. Failure to detectl-lysine decarboxylase activity in the chick embryo lumbar spinal cord is contrasted with the previous report of high cadaverine levels in chick embryos.     

鸟氨酸脱羧酶对人滋养细胞分泌绒毛膜促性腺激素的调控作用

应用人细胞滋养细胞的无血清短周期培养方法，研究了这些培养细胞分泌人绒毛膜促性腺激素（ＨＣＧ）的调节机制。结果表明：细胞经８小时培养具有良好的ＨＣＧ分泌功能。这些培养细胞的匀浆制品具有鸟酸脱羧酶（ＯＤＣ）的活性，对二丁酰ｃＡＭＰ、多胺物质和放绒菌素Ｄ呈现不同的应答。ＯＤＣ的活性与培养细胞的数量明显相关，与各种试剂的剂量也有密切的相关性。该酶活性的改变又与细胞ＨＣＧ分泌功能相联系。实验结果提示，细胞滋养细胞内分泌功能的表达与ＯＤＣ的活性，与内源性多胺和ｃＡＭＰ的水平相关。它们在细胞滋养细胞分泌ＨＣＧ的调控中可能是一个决定的因素。     

Ornithine decarboxylase and S-adenosylmethionine decarboxylase activity in the accessory sex organs of intact, castrated, and androgen-stimulated castrated rats

We have studied the activities of ornithine decarboxylase and adenosylmethionine decarboxylase in the 10(6)-m/s2 supernatants of the different lobes of the prostate and the seminal vesicles of castrates, androgen-stimulated castrates, and intact controls. After castration L-ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (AMDC) activities fell in all tissues examined. The induction of kinetics was followed for 72 h after administration of testosterone propionate to castrated rats. AMDC activities increased more rapidly than ODC activities in every tissue studied. Peak activities were reached more rapidly in the dorsal lobe than in the other tissues. ODC activity of the ventral lobe increased linearly for 48 h after stimulation. In the other tissues studied, ODC activity reached a maximum after 24 h and thereafter leveled off or decreased. In conclusion we have found distinct differences in ODC and AMDC activity in various tissues and major differences between treatment groups, with near extinction of activity at castration. In castrates stimulated with testosterone, the between-group differences prevailed but with different patterns of ODC versus AMDC activity. AMDC is seemingly rate-limiting in polyamine synthesis in stimulated tissues, while ODC controls synthesis in tissues from castrated rats.     

Prostanoids, ornithine decarboxylase, and polyamines in primary chemoprevention of familial adenomatous polyposis

BACKGROUND & AIMS: Familial adenomatous polyposis because of germline mutation of the adenomatous polyposis coli gene is characterized by development of colorectal adenomas and, ultimately, colorectal cancer. The usefulness of colorectal mucosal compounds to predict the effect on adenoma development of primary chemoprevention with the nonsteroidal anti-inflammatory drug sulindac was evaluated. METHODS: A randomized, double-blind, placebo-controlled study of 41 subjects genotypically affected with familial adenomatous polyposis but phenotypically unaffected was conducted. Patients received either sulindac or placebo for 48 months, and development of new adenomas was evaluated. The levels of 5 prostanoids, ornithine decarboxylase, and polyamines were measured serially in normal-appearing rectal mucosa. RESULTS: There were no statistically significant differences between treatment groups in baseline levels of prostanoids, ornithine decarboxylase, or polyamines. At conclusion of the study, 4 of 5 prostaglandin levels were statistically significantly lower in the sulindac group than in the placebo group. Among the subset of patients taking sulindac, 3 of 5 prostaglandin levels were statistically significantly lower in patients who were polyp free than in those who developed polyps. By contrast, there were no statistically significant differences in ornithine decarboxylase or polyamines between treatment groups or in those on sulindac who were polyp free compared with those who developed polyps. CONCLUSIONS: Colorectal mucosal prostaglandin levels, but not ornithine decarboxylase or polyamines, may be valuable biomarkers to assess appropriate drug dosage and medication compliance in patients undergoing primary chemoprevention therapy with sulindac. Reduction of mucosal prostaglandin levels may be necessary to achieve chemopreventive benefit from this agent.