Ornithine decarboxylase assay in human colorectal mucosa. Methodologic issues of importance to quality control

Antioxidant Agents and Colorectal Carcinogenesis: Role of β-Carotene, Vitamin E and Vitamin C

In consideration of findings reported in the literature and of our study, we examined the correlation between antioxidants (β-carotene, vitamin C, vitamin E) and colorectal carcinogenesis. Although diagnostic progress has been made in the last decades, no significant improvements in death rates have been achieved in the western world. Exogenous factors might be responsible for a complex alteration process of normal colonic mucosa into adenoma and carcinoma. Free radicals and reactive oxygen metabolites, due to increased production or to reduced inactivation, following a decrease in the antioxidant burden in the mucosa, might cause damage to DNA, thereby resulting in genetic alterations. This might represent the cause of the transformation process: normal mucosa→ adenoma→ carcinoma. In a prospective study, we observed a reduction of β-carotene levels in normal colonic mucosa in patients with polyps and colorectal cancer. We also showed that β-carotene supplementation raises levels of this micronutrient in the colonic mucosa of these patients. Findings from the literature and our trials show a significant decrease in the antioxidant capacity of colorectal mucosa in patients affected by colorectal cancer, although there is a significant interindividual variability. Such results suggest a possible chemopreventive role of antioxidant agents in colorectal cancer.

Vitamin K1 exerts antiproliferative effects and induces apoptosis in three differently graded human colon cancer cell lines

Vitamin K1 has been demonstrated as having anticancer potentiality mainly in liver cancer cells. Beyond the reported mechanisms of cancer inhibition (cell cycle arrest and induction of apoptosis), a possible control by vitamin K1 on molecules affecting cell growth could be hypothesized. In the literature, few (if any) data are available on its antitumor effects on colon cancer cells. Therefore, the aims of the study were to investigate in three differently graded human colon cancer cell lines (Caco-2, HT-29, and SW480) the effects of increasing concentrations of vitamin K1 (from 10 μM to 200 μM) administered up to 72 h on (1) cell proliferation, (2) apoptosis with the possible involvement of the MAPK pathway, and (3) polyamine biosynthesis. Vitamin K1 treatment caused a significant antiproliferative effect and induced apoptosis in all the cell lines, with the involvement of the MAPK pathway. A concomitant and significant decrease in the polyamine biosynthesis occurred. This is the first study demonstrating a significant polyamine decrease in addition to the antiproliferative and proapoptotic effects following vitamin K1 administration to colon cancer cell lines. Therapeutically, combinations of vitamin K1 with polyamine inhibitors and/or analogues may represent a suitable option for chemoprevention and/or treatment in future strategies for colorectal cancer management.

Effects of Lactobacillus rhamnosus GG on proliferation and polyamine metabolism in HGC-27 human gastric and DLD-1 colonic cancer cell lines

Previous in vitro and in vivo studies have suggested that lactobacilli can exert antiproliferative effects on the gastrointestinal epithelium. However, their role in affecting the cellular proliferative mechanisms is not completely clear. The aim of this study was to investigate the effects of increasing concentrations of Lactobacillus rhamnosus strain GG (L. GG) homogenate on cell growth and proliferation (by MTT, [3H]-thymidine incorporation and polyamine biosynthesis) in neoplasms originating from different gastrointestinal tracts. Thus, HGC-27 human gastric cancer cells and DLD-1 human colonic adenocarcinoma cells were evaluated. Besides, in order to verify which bacterial fraction was involved in the antiproliferative effects, the cytoplasm and cell wall extracts were tested separately. Gastric HGC-27 and colonic DLD-1 cells showed significant differences in their proliferative behavior, in particular in their polyamine profile and biosynthesis. Notwithstanding, one and the other proved to be sensitive to the growth inhibition by the highest concentrations of bacterial homogenate. Both HGC-27 and DLD-1 cells were resistant to the bacterial cell wall fractions, whereas increasing cytoplasm fraction concentrations induced an evident antiproliferative effect. These data suggest that cytoplasm extracts could be the responsible for L. GG action on proliferation in these two cell lines from gastric and colonic neoplasms.

Effects of Lactobacillus rhamnosus GG on the cell growth and polyamine metabolism in HGC-27 human gastric cancer cells

Previous in vivo studies have suggested that lactobacilli can exert anti-proliferative effects on the gastric epithelium. However, few data are available on their mechanisms of action. The aim of this study was to investigate the effects of increasing concentrations of Lactobacillus rhamnosus strain GG (L. GG) homogenate on cell growth and proliferation [by 3-(4,5 di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, [(3)H]-thymidine incorporation and polyamine biosynthesis] and apoptosis processes (by Bax/Bcl-2 mRNA expression) in HGC-27 human gastric cancer cells. To verify which bacterial fraction was involved in the antiproliferative and proapoptotic effects, the cytoplasm and cell wall extracts were tested separately. HGC-27 cells were sensitive to the apoptotic induction and growth inhibition by increased concentrations of bacterial homogenate. HGC-27 cells were resistant to the bacterial cell wall fractions, whereas increasing cytoplasm fraction concentrations induced evident antiproliferative and proapoptotic actions. These data suggest that cytoplasm extracts could be responsible for L. GG action on HGC-27 cell proliferation.

Effects of genistein on the polyamine metabolism and cell growth in DLD-1 human colon cancer cells

Polyamines and their rate-limiting enzyme, ornithine decarboxylase (ODC), are actively involved in cell growth and differentiation. The phytoestrogen genistein has been demonstrated to possess antitumor properties by influencing proliferation, differentiation, and apoptosis. The aim of this study was to investigate the effects of genistein at concentrations ranging from 0.01 to 100 microM on the polyamine biosynthesis, cell proliferation, and apoptosis in the estrogen receptor-positive DLD-1 human colon cancer cell line. Polyamine levels and ODC activity were evaluated by high performance liquid chromatography and radiometric technique, respectively. The proliferative response was estimated by [3H]-thymidine incorporation and the colorimetric 3-(4,5 di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test. Apoptosis was investigated by DNA fragmentation. Bax and Bcl-2 gene expressions were evaluated by multiplex-polymerase chain reaction. At concentration >or=1 microM, genistein decreased significantly the ODC activity and the polyamine levels. At the same concentration, genistein also increased significantly Bax mRNA expression, but not Bcl-2 mRNA expression. Higher concentrations (>or=10 microM) were needed to obtain a significant inhibition of cell proliferation and DNA fragmentation. The results of this study suggest that genistein can affect growth of DLD-1 cells by both decreasing polyamine biosynthesis and inducing apoptosis. However, further studies are required to assess the true ability of a soy rich diet in modifying colon cancer risk.

Polyamines as clinical laboratory tools

Since their discovery by Antoni van Leeuwenhoek in 1678 until the recent development of transgenic mice expressing proteins altering polyamine levels in a tissue-specific manner, polyamines have been the object of intense research efforts which have shed light on several biological and pathological processes. From the discovery of a particular form of proteasome regulation of the catabolism of the key regulatory enzyme in their synthetic pathway, to the experimental cancer treatment or prevention with polyamine antagonists or inhibitors of the latter enzyme, a whole spectrum of interests can be revealed. Still, many aspects of their functions remain elusive and difficulties inherent in their analysis, which relies on sophisticated high-performance liquid chromatographic (HPLC) methods, and the lack of standardization; have hampered the transit from the research realm to the standard clinical laboratory domain. Their assay in biological fluids has been used for cancer diagnosis and for monitoring anticancer treatment. In this article, we attempt to provide an overview of polyamine structure, nutritional value, metabolism, and physiological roles. Next, we will summarize the main analytical methods on which we count, and finally we will address their role in diagnosis of cancer as well their proposed role as antioxidant and antiglycation agents.

The influence of Lactobacillus brevis on ornithine decarboxylase activity and polyamine profiles in Helicobacter pylori-infected gastric mucosa

BACKGROUND

Functional probiotics may prevent Helicobacter pylori infection, and some evidence suggests that they also possess antitumor properties. Lactobacillus brevis (CD2) is a functional Lactobacillus strain with peculiar biochemical features, essentially related to the activity of arginine deiminase. This enzyme catalyzes the catabolism of arginine and affects the biosynthesis of polyamines (putrescine, spermidine, and spermine). Polyamines are polycations found in high concentrations in both normal and neoplastic cells. Our aims were: 1, to assess whether oral administration of L. brevis (CD2) affects H. pylori survival in the human gastric mucosa; 2, to evaluate the effects of L. brevis (CD2) on polyamine biosynthesis in gastric biopsies from H. pylori-positive patients.

MATERIALS AND METHODS

For 3 weeks before endoscopy, 22 H. pylori-positive dyspeptic patients randomly received (ratio 1 : 1) high oral doses of L. brevis (CD2) or placebo. Before and after treatment, H. pylori infection was determined by urea breath test (UBT). In gastric biopsies, ornithine decarboxylase activity and polyamine levels were, respectively, evaluated by a radiometric technique and high-pressure liquid chromatography (HPLC).

RESULTS

L. brevis (CD2) treatment did not eradicate H. pylori. However, a reduction in the UBT delta values occurred, suggesting a decrease in intragastric bacterial load. Significantly, L. brevis (CD2) induced a decrease in gastric ornithine decarboxylase activity and polyamine levels.

CONCLUSIONS

Our data support the hypothesis that L. brevis (CD2) treatment decreases H. pylori colonization, thus reducing polyamine biosynthesis. Alternatively, the arginine deiminase activity following L. brevis (CD2) administration might cause arginine deficiency, preventing polyamine generation from gastric cells.

Biomarker studies in reversed Barrett's esophagus

OBJECTIVE

The purpose of this study was to use biomarkers to assess for cancer risk in Barrett's esophagus patients with either squamous islands or complete reversal of their intestinal metaplasia to squamous epithelium.

METHODS

The biomarkers included proliferation characteristic using Ki-67, p53 abnormalities using immunohistochemical methods with two antibodies, DO-1 and DO-7, and ornithine decarboxylase (ODC) activity.

RESULTS

Eleven patients had complete reversal produced by a combination of acid suppression and thermal injury (multipolar electrocoagulation). Ki-67 staining was indistinguishable from that of normal squamous esophageal epithelium, i.e., basal layer staining only. All 11 cases were negative for p53. ODC activity was low and in the range for normal squamous epithelium. Fourteen patients had squamous islands (partial reversal) after prolonged proton pump inhibitor therapy. Multilayer Ki-67 staining occurred in nine cases (64%), and six (43%) had areas of positive p53 staining.

CONCLUSIONS

Initial biomarker studies suggest that completely reversed squamous epithelium is biologically similar to normal squamous epithelium and of low cancer risk. In contrast, partial reversal, manifest as squamous islands, is accompanied by biomarker abnormalities.

NG-hydroxy-L-arginine and nitric oxide inhibit Caco-2 tumor cell proliferation by distinct mechanisms

The objective of this study was to elucidate the role and mechanism of nitric oxide (NO) synthase (NOS) in modulating the growth of the Caco-2 human colon carcinoma cell line. The two novel observations reported here are, first, that NG-hydroxy-L-arginine (NOHA) inhibits Caco-2 tumor cell proliferation, likely by inhibiting arginase activity, and, second, that NO causes cytostasis by mechanisms that might involve inhibition of ornithine decarboxylase (ODC) activity. Both arginase and ODC are enzymes involved in the conversion of arginine to polyamines required for cell proliferation. Cell growth was monitored by cell count, cell protein analysis, and DNA synthesis. NOHA (1-30 microM) and NO in the form of DETA/NO (1-30 microM) inhibited cell proliferation by 30-85%. The cytostatic effect of NOHA was prevented by addition of excess ornithine, putrescine, spermidine, or spermine to cell cultures, whereas the cytostatic effect of NO (DETA/NO) and alpha-difluoromethylornithine (ODC inhibitor) was unaffected by ornithine but was prevented by putrescine, spermidine, or spermine. The cytostatic effect of NOHA appeared to be independent of its conversion to NO, and the effect of NO appeared to be independent of cGMP. NOHA inhibited urea production by Caco-2 cells and inhibited arginase catalytic activity (85% at 3 microM), whereas NO (DEA/NO and SNAP) inhibited ODC activity (>/=60% at 30 microM) without affecting arginase activity. Coculture of Caco-2 cells with lipopolysaccharide/cytokine-activated rat aortic endothelial cells markedly slowed Caco-2 cell proliferation, and this was blocked by NOS inhibitors. These observations that NOHA and NO may inhibit sequential steps in the arginine-polyamine pathway suggest a novel biological role for NOS in the inhibition of cell proliferation of certain tumor cells and possibly other cell types.

High-resolution reversed-phase high-performance liquid chromatography analysis of polyamines and their monoacetyl conjugates by fluorescence detection after derivatization with N-hydroxysuccinimidyl 6-quinolinyl carbamate

A highly sensitive, accurate, and reproducible HPLC method for the determination of all natural polyamines and their monoacetyl conjugates is described. The presented method is based on precolumn derivatization with N-hydroxysuccinimidyl 6-quinolinyl carbamate (HSQC) followed by C18-HPLC separation using a ternary gradient and fluorescence detection (lambda Ex = 248 nm, lambda Em = 398 nm). The derivatives of the four main polyamines (putrescine, cadaverine, spermidine, and spermine) and the internal standard were synthesized on a preparative scale and characterized, especially with respect to their molar absorptivities and fluorescence quantum yields. The limits of detection of the highly stable derivatives ranged from 30 to 130 fmol (injection volume 10 microliters) for putrescine and N-acetylcadaverine, respectively (signal to noise ratio = 10), with excellent linearity within the range from 1 to 100 microM. High reproducibility for both retention times and peak areas, with coefficients of variation ranging from 0.14 to 0.88% and from 1.83 to 3.80%, respectively, were achieved. Provided that deproteinization of the samples was carried out immediately, recoveries of the analytes from homogenates of pancreatic cancer xenografts were high and reproducible. The optimized method was applied to the determination of the polyamine content of cultured pancreatic cancer cells and of tissue from colorectal adenocarcinoma, proving precise and reproducible quantification in these complex biological matrices.

Biochemical tests in diseases of the intestinal tract: their contributions to diagnosis, management, and understanding the pathophysiology of specific disease states

Biochemical testing plays a major role in the complete evaluation of patients with suspected or established intestinal disease. We have classified these tests according to the medium in which they are performed: breath tests, including isotopic and nonisotopic tests, fecal tests, urine tests, serum tests, tissue tests, and other tests. The principles of various tests are outlined, and the role of each test in the evaluation of particular gastrointestinal disorders is discussed.

Polyamine levels and ODC activity in intestinal-type and diffuse-type gastric carcinoma

Gastric carcinomas are divided into two types according to Lauren's classification: intestinal and diffuse types. Polyamines (putrescine, spermidine, and spermine) are polycations involved in neoplastic growth of gastrointestinal mucosa. A key role is also played by ornithine decarboxylase, the rate limiting enzyme in polyamine metabolism. Our aim was to investigate whether there were differences between the two types of tumor in polyamine metabolism. Twenty-seven patients with gastric carcinoma entered the study. Seventeen carcinomas were classified as diffuse type and 10 as intestinal type. Polyamine levels were evaluated by high-performance liquid chromatography. Ornithine decarboxylase activity was measured by a radiometric technique. Polyamine levels and ornithine decarboxylase activity were significantly higher in intestinal type samples than diffuse type samples. A similarity of polyamine levels in intestinal type samples with levels previously observed in patients with colorectal adenocarcinoma was also found. These findings show a different proliferative behavior of these two types of tumor, and therefore different therapeutic strategies can be hypothesized.

Ornithine decarboxylase levels in patients with normal colonic mucosa

We describe a systematic examination of ornithine decarboxylase activity in 120 colonic mucosal samples which were obtained from 20 subjects without colonic disease to establish the normal mean and standard deviation from proximal to distal colon. Ornithine decarboxylase activity was determined by releasing CO2 from DL-[1-14C]ornithine. The mean ornithine decarboxylase levels (CO2 liberated) ranged from 0.26 +/- 0.08 nmol/h.mg protein in the caecum to 0.44 +/- 0.16 nmol/h.mg protein in the rectum. There was no difference between sex and age. Ornithine decarboxylase was not stimulated by guanosine 5'-triphosphate. alpha-Difluoromethylornithine showed an ornithine decarboxylase inhibition of 97.1%. Ornithine decarboxylase activity can be measured with reliable precision and reproducibility. The knowledge of the normal range of ornithine decarboxylase activity in normal human colonic mucosa is necessary for the determination of ornithine decarboxylase activity in pathological findings, especially in malignant transformation.

Review article: Barrett's oesophagus--cancer risk, biology and therapeutic management

Barrett's oesophagus is receiving increasing scrutiny as the rates of adenocarcinoma of the oesophagus rise. Because clinical features are not predictive of the presence of Barrett's oesophagus and most individuals with Barrett's oesophagus go undetected, a case can be made for surveillance endoscopy in patients with chronic reflux. Once Barrett's oesophagus is diagnosed patients should be entered into a surveillance programme despite lack of proof of efficacy. Scientific study of putative biological markers of increased risk has added dramatically to the understanding of the biology of the lesion, but currently the finding of high grade dysplasia remains the best marker predicting the presence of greatly increased risk of developing cancer. It is likely that newer molecular biology techniques will become clinically applicable biological markers in the future. Currently there is no effective medical nor surgical therapy to cause regression of the metaplastic Barrett's epithelium, however the application of novel de-differentiating agents or ablation of the metaplastic epithelium while controlling oesophageal acid exposure and other environmental abnormalities offer hope that effective treatment of Barrett's oesophagus may someday be reality.

Clinical experience with the micronucleus assay

Because of the logistical and practical problems that make cancer prevention trials using cancer incidence as an endpoint virtually impossible to conduct for the majority of cancer types, there is a desperate need for valid intermediate markers of cancer risk to serve as surrogate endpoints in chemoprevention trials. A long and continually growing list of potential markers has been developed in the recent past. Unfortunately very few, if any, of them have been subjected to the usual quality control requirements for a laboratory test before being applied to clinical settings. Modulation of micronuclei frequency has been reported in a number of chemoprevention trials involving the oral cavity, esophagus, lung, and lower GI tract; however, we have focused our efforts primarily on applying the assay to exfoliated buccal mucosal cells, since much of the published data deal with this site, and oral cancer prevention is the theme of one of our chemoprevention trials. After standardizing the definition of a micronucleus by literature review and direct exchange of slides and photographs with other investigators active in the field, we obtained smears from normal subjects, smokers with or without leukoplakia, and tobacco chewers with or without leukoplakia. Our summarized findings follow: (1) Micronuclei represent only one of numerous cytological abnormalities in exfoliated buccal cells that are manifest particularly in tobacco chewers. These include a high frequency of anucleate, binucleate, and multinucleated cells, abnormal shapes and sizes of nuclei, etc.(ABSTRACT TRUNCATED AT 250 WORDS)