Polyamine levels, ornithine decarboxylase (ODC) activity, and ODC-mRNA expression in normal and cancerous human colonocytes

Metformin May Alter the Metabolic Reprogramming in Cancer Cells by Disrupting the L-Arginine Metabolism: A Preliminary Computational Study

Metabolic reprogramming in cancer is considered to be one of the most important hallmarks to drive proliferation, angiogenesis, and invasion. AMP-activated protein kinase activation is one of the established mechanisms for metformin’s anti-cancer actions. However, it has been suggested that metformin may exert antitumoral effects by the modulation of other master regulators of cellular energy. Here, based on structural and physicochemical criteria, we tested the hypothesis that metformin may act as an antagonist of L-arginine metabolism and other related metabolic pathways. First, we created a database containing different L-arginine-related metabolites and biguanides. After that, comparisons of structural and physicochemical properties were performed employing different cheminformatic tools. Finally, we performed molecular docking simulations using AutoDock 4.2 to compare the affinities and binding modes of biguanides and L-arginine-related metabolites against their corresponding targets. Our results showed that biguanides, especially metformin and buformin, exhibited a moderate-to-high similarity to the metabolites belonging to the urea cycle, polyamine metabolism, and creatine biosynthesis. The predicted affinities and binding modes for biguanides displayed good concordance with those obtained for some L-arginine-related metabolites, including L-arginine and creatine. In conclusion, metabolic reprogramming in cancer cells by metformin and biguanides may be also driven by metabolic disruption of L-arginine and structurally related compounds.

A new 68Ga-labeled ornithine derivative for PET imaging of ornithine metabolism in tumors

Ornithine metabolism plays a vital role in tumorigenesis. For cancer cells, ornithine is mainly used as a substrate for ornithine decarboxylase (ODC) for the synthesis of polyamines. The ODC as a key enzyme of polyamine metabolism has become an important target for cancer diagnosis and treatment. To non-invasively detect the levels of ODC expression in malignant tumors, we have synthesized a novel ⁶⁸Ga-labeled ornithine derivative ([⁶⁸Ga]Ga-NOTA-Orn). The synthesis time of [⁶⁸Ga]Ga-NOTA-Orn was about 30 min with a radiochemical yield of 45-50% (uncorrected), and the radiochemical purity was > 98%. [⁶⁸Ga]Ga-NOTA-Orn was stable in saline and rat serum. Cellular uptake and competitive inhibition assays using DU145 and AR42J cells demonstrated that the transport pathway of [⁶⁸Ga]Ga-NOTA-Orn was similar to that of L-ornithine, and it could interact with the ODC after transporting into the cell. Biodistribution and micro-positron emission tomography (Micro-PET) imaging studies showed that [⁶⁸Ga]Ga-NOTA-Orn exhibited rapid tumor uptake and was rapidly excreted through the urinary system. All above results suggested that [⁶⁸Ga]Ga-NOTA-Orn is a novel amino acid metabolic imaging agent with great potential of tumor diagnosis.

Biochemical Markers of Colorectal Cancer - Present and Future

According to a report by the National Cancer Institute, colorectal cancer (CRC) is one of the most common types of cancer worldwide. CRC is often recognized too late for successful therapy. Tumor markers have been sought for a number of years to detect the transformation of malignant cells at the earliest possible stage. They are usually proteins associated with a malignancy and might be clinically useful in patients with cancer. Several classical markers have been used to recognize colorectal cancer, including carcinoembryonic antigen (CEA), carbohydrate antigen (CA 19.9), tissue polypeptide specific antigen (TPS) and tumor-associated glycoprotein-72 (TAG-72). None of these tests, however, have excellent diagnostic accuracy. Recent studies have been conducted on the use of hematopoietic growth factors (HGFs) and various enzymes in the diagnosis and prognosis of colorectal cancer. These include macrophage-colony stimulating factor (M-CSF) and granulocyte-macrophage-colony stimulating factor (GM-CSF), interleukin-3, interleukin-6 and enzymes (alcohol dehydrogenase and lysosomal exoglycosidases). Significantly, most cancer deaths are not caused by the primary tumor itself but by its spread. Analysis of circulating cancer cells (CTCs), ie, factors responsible for metastasis, may be a source of information useful in the treatment of patients with colorectal cancer. Currently available markers have significant limitations.

Metabolic models predict bacterial passengers in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a complex multifactorial disease. Increasing evidence suggests that the microbiome is involved in different stages of CRC initiation and progression. Beyond specific pro-oncogenic mechanisms found in pathogens, metagenomic studies indicate the existence of a microbiome signature, where particular bacterial taxa are enriched in the metagenomes of CRC patients. Here, we investigate to what extent the abundance of bacterial taxa in CRC metagenomes can be explained by the growth advantage resulting from the presence of specific CRC metabolites in the tumor microenvironment.

METHODS

We composed lists of metabolites and bacteria that are enriched on CRC samples by reviewing metabolomics experimental literature and integrating data from metagenomic case-control studies. We computationally evaluated the growth effect of CRC enriched metabolites on over 1500 genome-based metabolic models of human microbiome bacteria. We integrated the metabolomics data and the mechanistic models by using scores that quantify the response of bacterial biomass production to CRC-enriched metabolites and used these scores to rank bacteria as potential CRC passengers.

RESULTS

We found that metabolic networks of bacteria that are significantly enriched in CRC metagenomic samples either depend on metabolites that are more abundant in CRC samples or specifically benefit from these metabolites for biomass production. This suggests that metabolic alterations in the cancer environment are a major component shaping the CRC microbiome.

CONCLUSION

Here, we show with in sillico models that supplementing the intestinal environment with CRC metabolites specifically predicts the outgrowth of CRC-associated bacteria. We thus mechanistically explain why a range of CRC passenger bacteria are associated with CRC, enhancing our understanding of this disease. Our methods are applicable to other microbial communities, since it allows the systematic investigation of how shifts in the microbiome can be explained from changes in the metabolome.

Cadaverine, a metabolite of the microbiome, reduces breast cancer aggressiveness through trace amino acid receptors

Recent studies showed that changes to the gut microbiome alters the microbiome-derived metabolome, potentially promoting carcinogenesis in organs that are distal to the gut. In this study, we assessed the relationship between breast cancer and cadaverine biosynthesis. Cadaverine treatment of Balb/c female mice (500 nmol/kg p.o. q.d.) grafted with 4T1 breast cancer cells ameliorated the disease (lower mass and infiltration of the primary tumor, fewer metastases, and lower grade tumors). Cadaverine treatment of breast cancer cell lines corresponding to its serum reference range (100–800 nM) reverted endothelial-to-mesenchymal transition, inhibited cellular movement and invasion, moreover, rendered cells less stem cell-like through reducing mitochondrial oxidation. Trace amino acid receptors (TAARs), namely, TAAR1, TAAR8 and TAAR9 were instrumental in provoking the cadaverine-evoked effects. Early stage breast cancer patients, versus control women, had reduced abundance of the CadA and LdcC genes in fecal DNA, both responsible for bacterial cadaverine production. Moreover, we found low protein expression of E. coli LdcC in the feces of stage 1 breast cancer patients. In addition, higher expression of lysine decarboxylase resulted in a prolonged survival among early-stage breast cancer patients. Taken together, cadaverine production seems to be a regulator of early breast cancer.

In vitro development and validation of a non-invasive (13)C-stable isotope assay for ornithine decarboxylase

Oesophageal cancer is a significant cause of cancer related mortality, with increasing incidence worldwide. Ornithine decarboxylase (ODC) is an enzyme involved in polyamine synthesis and cellular proliferation, and ODC expression and activity has been implicated as a prognostic marker of oesophageal cancer. This study aimed to develop and optimise an in vitro (13)C-stable isotope assay for ODC activity as a non-invasive marker of oesophageal cancer. Experiments were performed in triplicate (n  =  3/group/cell line) using Caco2, HeLa, Flo-1, OE33, TE7 and OE21 cell lines (colorectal, cervical, oesophageal adenocarcinoma and oesophageal squamous carcinoma respectively). Following addition of 2mM (13)C-ornithine to cells, 10 ml gas samples were collected from the headspace every 20 min for a total of five hours. Gas samples were analysed using isotope ratio mass spectrometry to quantify (13)CO2. Assay specificity was determined using the selective ODC inhibitor, N-(4'-Pyridoxil)-Ornithine(BOC)-OMe (POB). All data is expressed as δ (13)CO2 from baseline. High ODC activity was detected by (13)C-ornithine assay in Caco2 (32.00  ±  1.12 δ (13)CO2) in contrast to HeLa cells (5.44  ±  0.14 δ (13)CO2) cells. POB inhibited activity in Caco2 cells to 12.87  ±  1.10 δ (13)CO2. Differential ODC activity was detected in all oesophageal cancer cells, and 53 h incubation of cell lines with POB reduced activity by 72%, 56%, 64% and 69% in the Flo-1, OE33, OE21 and TE7 cell lines respectively. We have shown that ODC activity can be selectively detected by a non-invasive, stable-isotope (13)C-ornithine assay. ODC activity was detected in all oesophageal cancer cell lines in vitro. Further studies are indicated to quantify ODC activity in oesophageal cancer patients.

Characterizing metabolic changes in human colorectal cancer

Colorectal cancer (CRC) remains a leading cause of cancer death worldwide, despite the fact that it is a curable disease when diagnosed early. The development of new screening methods to aid in early diagnosis or identify precursor lesions at risk for progressing to CRC will be vital to improving the survival rate of individuals predisposed to CRC. Metabolomics is an advancing area that has recently seen numerous applications to the field of cancer research. Altered metabolism has been studied for many years as a means to understand and characterize cancer. However, further work is required to establish standard procedures and improve our ability to identify distinct metabolomic profiles that can be used to diagnose CRC or predict disease progression. The present study demonstrates the use of direct infusion traveling wave ion mobility mass spectrometry to distinguish metabolic profiles from CRC samples and matched non-neoplastic epithelium as well as metastatic and primary tumors at different stages of disease (T1-T4). By directly infusing our samples, the analysis time was reduced significantly, thus increasing the speed and efficiency of this method compared to traditional metabolomics platforms. Partial least squares discriminant analysis was used to visualize differences between the metabolic profiles of sample types and to identify the specific m/z features that led to this differentiation. Identification of the distinct m/z features was made using the human metabolome database. We discovered alterations in fatty acid biosynthesis and oxidative, glycolytic, and polyamine pathways that distinguish tumors from non-malignant colonic epithelium as well as various stages of CRC. Although further studies are needed, our results indicate that colonic epithelial cells undergo metabolic reprogramming during their evolution to CRC, and the distinct metabolites could serve as diagnostic tools or potential targets in therapy or primary prevention. Graphical Abstract Colon tissue biopsy samples were collected from patients after which metabolites were extracted via sonication. Two-dimensional data were collected via IMS in tandem with MS (IMMS). Data were then interpreted statistically via PLS-DA. Scores plots provided a visualization of statistical separation and groupings of sample types. Loading plots allowed identification of influential ion features. Lists of these features were exported and analyzed for specific differences. Direct comparisons of the ion features led to the identification and comparative analyses of candidate biomarkers. These differences were then expressed visually in charts and tables.

Metabolomics of colorectal cancer: past and current analytical platforms

Metabolomics is coming of age as an important area of investigation which may help reveal answers to questions left unanswered or only partially understood from proteomic or genomic approaches. Increased knowledge of the relationship of genes and proteins to smaller biomolecules (metabolites) will advance our ability to diagnose, treat, and perhaps prevent cancer and other diseases that have eluded scientists for generations. Colorectal tumors are the second leading cause of cancer mortality in the USA, and the incidence is rising. Many patients present late, after the onset of symptoms, when the tumor has spread from the primary site. Once metastases have occurred, the prognosis is significantly worse. Understanding alterations in metabolic profiles that occur with tumor onset and progression could lead to better diagnostic tests as well as uncover new approaches to treat or even prevent colorectal cancer (CRC). In this review, we explore the various analytical technologies that have been applied in CRC metabolomics research and summarize all metabolites measured in CRC and integrate them into metabolic pathways. Early studies with nuclear magnetic resonance and gas-chromatographic mass spectrometry suggest that tumor cells are characterized by aerobic glycolysis, increased purine metabolism for DNA synthesis, and protein synthesis. Liquid chromatography, capillary electrophoresis, and ion mobility, each coupled with mass spectrometry, promise to advance the field and provide new insight into metabolic pathways used by cancer cells. Studies with improved technology are needed to identify better biomarkers and targets for treatment or prevention of CRC.

DFMO: targeted risk reduction therapy for colorectal neoplasia

Strategies to decrease intracellular polyamine levels have been studied for their efficacy in reducing colorectal cancer (CRC) risk. A successful strategy combined agents that decreased polyamine synthesis by inhibiting ornithine decarboxylase with difluoromethylornithine (DFMO), and increased cellular export of polyamines by activating the spermidine/spermine acetyl transferase with non-steroidal anti-inflammatory drugs (NSAIDs). A Phase III trial treating resected adenoma patients with DFMO plus sulindac demonstrated marked reduction of metachronous adenomas, advanced adenomas and multiple adenomas compared to placebo. This combination regimen was well-tolerated, however there was a non-significant excess of cardiovascular events in the treatment arm compared to placebo as well as modest ototoxicity. Targeting this therapy to people at elevated risk of CRC, and employing clinical and genetic predictors, should improve patient benefit and reduce the risk of side effects to improve the acceptability of this strategy.

Targeting polyamines and inflammation for cancer prevention

Increased polyamine synthesis and inflammation have long been associated with intraepithelial neoplasia, which are risk factors for cancer development in humans. Targeting polyamine metabolism (by use of polyamine synthesis inhibitors or polyamine catabolism activators) and inflammation (by use of nonsteroidal anti-inflammatory drugs) has been studied for many cancers, including colon, prostate, and skin. Genetic epidemiology results indicate that a genetic variant associated with the expression of a polyamine biosynthetic gene is associated with risk of colon and prostate cancers. A clinical trial of difluoromethylornithine (DFMO), a selective inhibitor of polyamine synthesis, showed that the 1 year treatment duration reduced prostate volume and serum prostate-specific antigen doubling time in men with a family history of prostate cancer. A second, clinical trial of DFMO in combination with sulindac, a NSAID in patients with prior colon polyps found that the 3-year treatment was associated with a 70% reduction of all, and over a 90% reduction of advanced and/or multiple metachronous colon adenomas. In this chapter, we discuss that similar combination prevention strategies of targeting polyamines and inflammation can be effective in reducing risk factors associated with the development of human cancers.

Tip60 protein isoforms and altered function in skin and tumors that overexpress ornithine decarboxylase

Elevated expression of ornithine decarboxylase (ODC) and increased synthesis of polyamines are hallmarks of epithelial tumorigenesis. The skin and tumors of K6/ODC and ODC/Ras transgenic mice, in which overexpression of ODC has been targeted to hair follicles, were found to exhibit intrinsically high histone acetyltransferase (HAT) activity. We identified Tip60 as a candidate enzyme for contributing significantly to this abnormally high HAT activity. Compared with normal littermate controls, the levels of Tip60 protein and an alternative splice variant Tip53 were found to be greater in K6/ODC mouse skin. Furthermore, skin tumors that spontaneously develop in ODC/Ras bigenic mice typically have substantially more Tip60 protein than adjacent non-tumor-bearing skin and exhibit a unique pattern of Tip60 size variants and chemically modified protein isoforms. Steady-state Tip60 and Tip53 mRNA levels were not affected in ODC-overexpressing skin and tumors, implying novel posttranscriptional regulation by polyamines. Given the diverse roles of Tip60, the overabundance of Tip60 protein is predicted to have biological consequences. Compared with normal littermate skin, we detected altered association of Tip60 with E2F1 and a subset of newly identified Tip60-interacting transcription factors in ODC transgenic mouse skin and tumors. E2F1 was shown to be bound in greater amounts to up-regulated target genes in ODC-overexpressing skin. Thus, up-regulation of Tip60 protein, influencing the expression of Tip60-regulated genes, could play a contributing role in polyamine-mediated tumor promotion. (

Effects of amino acid-derived luminal metabolites on the colonic epithelium and physiopathological consequences

Depending on the amount of alimentary proteins, between 6 and 18 g nitrogenous material per day enter the large intestine lumen through the ileocaecal junction. This material is used as substrates by the flora resulting eventually in the presence of a complex mixture of metabolites including ammonia, hydrogen sulfide, short and branched-chain fatty acids, amines; phenolic, indolic and N-nitroso compounds. The beneficial versus deleterious effects of these compounds on the colonic epithelium depend on parameters such as their luminal concentrations, the duration of the colonic stasis, the detoxication capacity of epithelial cells in response to increase of metabolite concentrations, the cellular metabolic utilization of these metabolites as well as their effects on colonocyte intermediary and oxidative metabolism. Furthermore, the effects of metabolites on electrolyte movements through the colonic epithelium must as well be taken into consideration for such an evaluation. The situation is further complicated by the fact that other non-nitrogenous compounds are believed to interfere with these various phenomenons. Finally, the pathological consequences of the presence of excessive concentrations of these compounds are related to the short- and, most important, long-term effects of these compounds on the rapid colonic epithelium renewing and homeostasis.

Ornithine decarboxylase activity in tumor cell lines correlates with sensitivity to cell death induced by histone deacetylase inhibitors

Inhibitors of histone deacetylases (HDAC) show significant promise as targeted anticancer agents against a variety of hematologic and solid tumors. HDAC inhibitors arrest the growth of primary cells, but they induce apoptosis or differentiation of tumor cells. Although the precise mechanism is unknown, differences in cell cycle checkpoints and chromatin structure may be responsible. Cellular polyamines regulate both cell cycle progression and chromatin structure. In tumors, polyamines are abundantly produced because of increased activity of the rate-limiting enzyme in polyamine synthesis, ornithine decarboxylase (ODC). To determine if polyamines contribute to the cellular response to HDAC inhibitors, we inhibited ODC activity with alpha-difluoromethylornithine. Polyamine depletion increased resistance to apoptosis induced by HDAC inhibitors. In addition, we found that ODC activity levels correlated with sensitivity to HDAC inhibitors in a panel of tumor cell lines. We conclude that polyamines participate in the cellular response to HDAC inhibitors and that ODC activity correlates with sensitivity to HDAC inhibitor-induced apoptosis. Thus, elevated polyamine levels might be a biomarker for tumor sensitivity to HDAC inhibitor-induced apoptosis. These findings warrant clinical evaluation of tumor samples to determine if high ODC activity levels predict sensitivity to HDAC inhibitors.

Molecular mechanisms of the chemopreventive effects of resveratrol and its analogs in colorectal cancer: key role of polyamines?

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a phytoalexin found in grape skins, peanuts, and red wine, has been reported to exhibit a wide range of biological and pharmacological properties. It has been speculated that dietary resveratrol may act as an antioxidant, promote nitric oxide production, inhibit platelet aggregation, and increase high-density lipoprotein cholesterol and thereby serve as a cardioprotective agent (the so-called "French paradox"). Recently, it was demonstrated that resveratrol can function as a cancer chemopreventive agent, and there has been a great deal of experimental effort directed toward defining this effect. It has been shown that resveratrol and some of its analogues 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. This review summarizes the recent advances that have provided new insights into the molecular mechanisms underlying the promising properties of resveratrol focusing on the key role of the polyamine metabolism in colorectal cancer cells.

Estrogen-dependent regulation of ornithine decarboxylase in breast cancer cells through activation of nongenomic cAMP-dependent pathways

17beta-estradiol (E2) induces ornithine decarboxylase (ODC) activity in several E2-responsive tissues/cells, and this study investigated the mechanism of hormone-induced transactivation in MCF-7 human breast cancer cells. E2-induced reporter gene (luciferase) activity in MCF-7 cells transfected with a construct (pODC1) containing the -164 to +29 region of the human ODC gene promoter linked to bacterial luciferase. This promoter sequence contains GC-rich Sp1 binding sites, CAAT, LSF, cAMP response element (CRE), and TATA motifs. Deletion and mutational analysis of the ODC promoter showed that both CAAT and LSF sites were required for hormone-induced transactivation. Gel mobility shift and DNA footprinting assays indicated that NFYA and LSF bound the CAAT and LSF motifs, respectively, and GAL4-NFYA/GAL4-LSF chimeras were also activated by E2, 8-bromo-cAMP, and protein kinase A (PKA) expression plasmid. However, E2-induced transactivation of GAL4-NFYA and GAL4-LSF was blocked by the PKA inhibitor SQ22356 indicating that the mechanism of ODC induction by E2 involves upregulation of cAMP/PKA through nongenomic pathways of estrogen action.

Polyamines in the human gut

Intracellular polyamine concentrations are maintained by endogenous synthesis and uptake of exogenous polyamines from the gastrointestinal lumen. Recently, much attention has been focused on the role of polyamines in tumour pathogenesis and the possible therapeutic value of reducing polyamine concentrations in tumour tissue. Unfortunately, polyamines also appear to be essential for the maintenance of normal gastrointestinal structure and function. The immediate analytical challenge is to make progress in laboratory methods for polyamine class analyses and assessment of polyamine metabolism. An obvious gastroenterological target is to make up for past neglect of the function of these important dietary components.

ODC mRNA as a prognostic factor for predicting recurrence in meningiomas

In proliferating neoplastic cells, activity of the enzyme ornithine decarboxylase (ODC) increases. Among other brain tumors, ODC activation could also be observed in meningiomas. In the present study, we have investigated ODC gene expression in primary and recurrent meningiomas at the transcriptional level. ODC mRNA (messenger ribonucleic acid), ODC activity, number of mitoses, and Ki-67 index as a marker for nuclear proliferation were quantified in three different groups of meningiomas: tumors without recurrence in a 8.4 years median follow-up period, tumors with recurrence within a median follow-up of 3.0 years, and their corresponding recurrent tumors. ODC mRNA level was significantly higher in meningiomas with later recurrence as compared to meningiomas without recurrence (p < or = 0.01), whereas it declined in the recurrences of the second group (p < or = 0.001). In contrast, ODC activity showed no difference between the two groups of primary tumors, but a significant increase of enzyme activity could be observed in the recurrences as compared to the correponding primary tumors (p < or = 0.001). Likewise, an increase of the Ki-67 index could be detected in the recurrent group (p < or = 0.001). These results suggest that ODC mRNA may represent a prognostic factor for predicting recurrence in meningiomas.

Hydroxylamine-containing inhibitors of polyamine biosynthesis and impairment of colon cancer cell growth

Polyamine synthesis (by the action of ornithine decarboxylase [ODC] and S-adenosylmethionine decarboxylase [SAMDC]) and polyamine content are high in colon cancer. In addition, colonic lumen is rich in polyamines synthesised by colonic microflora; for this reason, polyamine depletion in colon cancer may be a logical approach to impair growth of colon cancer cells. We evaluated highly specific and reportedly non-toxic hydroxylamine-containing inhibitors of ODC (1-aminooxy-3-aminopropane, APA) and SAMDC (S-(5'-deoxy-5'-adenosyl)-methylthioethyl-hydroxylamine, AMA) in human colon cancer cells (Caco-2 and HT-29) in culture. APA depleted ODC activity within 24 hr, more rapidly than did difluoromethylornithine. APA and AMA in combination (100 microM each) reduced ODC and SAMDC activities to undetectable levels within 24 hr and intracellular polyamines to 8-23% of control. The resulting growth arrest could be reversed only by twice as much spermidine as is physiologically present in the colonic lumen. In concentrations sufficient to deplete growth, APA and AMA were not toxic. Simultaneous treatment with APA, AMA, and 5-fluorouracil reduced colon cancer cell survival more potently than treatment with 5-fluorouracil alone. The hydroxylamine-containing ODC and SAMDC inhibitors APA and AMA are potent inhibitors of colon cancer cell proliferation and might be therapeutically promising in colon cancer.

What's new with tumor markers for colorectal cancer?

BACKGROUND/AIMS

Many tumor markers have been utilized in the follow-up care of colorectal cancer patients. No marker, however, has proven reliably accurate in detecting recurrent disease.

METHODS

The strengths and weaknesses of currently available tumor markers are reviewed, with attention to related cost and efficacy.

RESULTS

Tumor antigens, enzymes, and genetic markers have been used as tumor markers. CEA and CA 19.9 are the most widely utilized; however, genetic markers are the most promising for the future.

CONCLUSIONS

Currently available markers have significant limitations. Development of genetic markers may greatly enhance our ability to predict prognosis and the need for adjuvant therapy. Marker-guided therapy may play an increasing role in this disease.

Low-dose deoxycholic acid stimulates putrescine uptake in colon cancer cells (Caco-2)

Deoxycholic acid (DCA) has long been implicated as tumour-promoting agent in the colon. Polyamines are necessary for cell proliferation, they are accumulated in high amounts in colon cancer cells, and their concentrations in the colonic lumen can reach millimolar levels. The aim of this study was to investigate the effects of physiological DCA concentrations on proliferation and polyamine content in human colon cancer cells (Caco-2) in culture. Over an initial 48 h in culture, DCA stimulated Caco-2 cell proliferation rate three-fold, reaching a maximum with 20 microM DCA. DCA-induced increases in ornithine decarboxylase (ODC) activity corresponded to peak proliferation rates, occurring only during the initial 48 h of cell proliferation. Treatment with low-dose DCA resulted in a two-fold increase in putrescine uptake, first noted after 2 days in culture, but persisting until the cells became confluent (day 5). Both basal and DCA-stimulated putrescine uptake in Caco-2 cells were saturable. Kinetic analysis of the uptake data showed that DCA-stimulated putrescine uptake was due to an increase in the capacity of the putative putrescine transporter, without changes in its affinity, therefore implying an increased number of putrescine transporters in the cell membrane, without change in their structure.

EGF-stimulated polyamine accumulation in the colon carcinoma cell line, Caco-2

BACKGROUND

Polyamines (putrescine, spermidine and spermine) are ubiquitous molecules indispensable for cell proliferation. In the intestinal lumen they are present in high amounts. Polyamine accumulation in proliferating cells of the intestinal mucosa is high, and it occurs both by enhanced synthesis and by increased uptake from the lumen.

AIMS

To study mitogen-induced polyamine accumulation in the gut, we treated proliferating Caco-2 cells with epidermal growth factor (EGF) and measured the activity of ornithine decarboxylase (ODC) and putrescine uptake. Furthermore, we investigated whether EGF-induced changes in the apical membrane could be responsible for the effect of EGF on polyamine uptake in Caco-2 cells.

METHODS

Putrescine uptake, ODC activity and intracellular polyamine content were evaluated in the presence of 100 ng/ml EGF. To study the mechanisms of EGF-stimulated polyamine uptake, apical membrane vesicles were isolated, and putrescine uptake into the vesicles measured. Possible enrichment in brush border membrane cytoskeleton proteins (ezrin and villin) was assessed by Western blot.

RESULTS

Treatment with EGF induced an increase in ODC activity, which occurred within the first minutes of treatment and reached peak values after 3 h. In contrast, an increase in putrescine uptake was more sustained, with peak levels at 12 h. Both synthesis and uptake contributed to an over 60% increase in intracellular putrescine and spermidine after EGF treatment. There were no detectable changes in apical membrane cytoskeleton (as concluded by the absence of ezrin and villin enrichment in EGF-treated Caco-2 cells). However, in apical membrane vesicles isolated from EGF-pretreated cells, putrescine uptake was enhanced twofold.

CONCLUSIONS

EGF stimulates both synthesis and uptake of polyamines in Caco-2 cells. Enhanced synthesis seems to ensure rapid supply with polyamines in the earliest stages of growth, while the uptake is responsible for the maintenance of high polyamine intracellular levels during late growth phases. EGF-stimulated polyamine uptake is apparently not a consequence of structural changes in the apical membrane, but is likely to occur by a distinct EGF-induced alteration of the polyamine transporter itself.

Dietary prevention of azoxymethane-induced colon carcinogenesis with rice-germ in F344 rats

The modifying effect of dietary administration of defatted rice-germ and gamma-aminobutyric acid (GABA)-enriched defatted rice-germ on azoxymethane (AOM)-induced colon carcinogenesis was investigated in two experiments with male F344 rats. In the first experiment (the pilot study), the effects of the defatted rice-germ, the GABA-enriched defatted rice-germ and rice-germ on AOM-induced (15 mg/kg body wt once a week for 3 weeks) formation of aberrant crypt foci (ACF) were examined. The latter two preparations (2.5% in the diet) significantly inhibited ACF formation (P < 0.005). In the second experiment, a long-term study of the effects of rice-germ was done. One group was treated with AOM alone, four groups received the carcinogen and were fed the diets containing 2.5% rice-germ or 2.5% GABA-enriched defatted rice-germ for 5 (initiation phase) or 30 weeks (post-initiation phase), two groups were treated with rice-germ or GABA-enriched defatted rice-germ alone and one group was kept on the basal diet. At the termination of the study, dietary exposure to rice-germ during the initiation phase significantly reduced the incidence of colonic adenocarcinoma (71 versus 29%, P < 0.01). GABA-enriched defatted rice-germ or rice-germ during the post-initiation phase also decreased the frequency of colonic adenocarcinoma (71 versus 20%, GABA-enriched defatted rice-germ feeding, P < 0.01; 27%, rice-germ feeding, P < 0.01). These data suggest that constituents of rice-germ are possible dietary preventatives for human colon cancers.

Tryosine kinase and ornithine decarboxylase activation in children with Helicobactor pylori gastritis

H. pylori infection has been considered a risk factor for the development of gastric malignancy. Ornithine decarboxylase and tyrosine kinases activities are increased in patients with colon or esophageal cancer. In this study we compared the ODC and tyrosine kinases activities in the gastric mucosa of children with H. pylori infection and normal mucosa. Gastric biopsies were prospectively collected from children during routine upper endoscopic procedure. H. pylori infection was determined histologically. Biopsies were analyzed for ODC activity, total tyrosine kinases activities, and for the activity of protooncogene tyrosine kinase pp60(c-src). The mean ODC activity (pmol 14CO2/mg. protein/hr) and total tyrosine kinases activity (pmol 32P/mg. protein) were 186 and 5877 for H. pylori infected mucosa; and 229 and 4300, for normal mucosa, respectively (p> 0.05). Tyrosine kinase pp60(c-src) protein levels were similar between H. pylori infected mucosa and normal mucosa (3.12 and 2.15 pmol 32P/mg. protein, respectively; p>0.05). There was no correlation between gastric inflammation and the level of ODC or tyrosine kinase activities. ODC and tyrosine kinase activities in the gastric mucosa are similar in children with H. pylori infection compared to normal mucosa. The data suggest that these enzymes cannot be used as markers for future cancer development in children.

Inhibition of Shigella flexneri-induced transepithelial migration of polymorphonuclear leucocytes by cadaverine

Dysentery caused by Shigella species is characterized by infiltration of polymorphonuclear leucocytes (PMNs) into the colonic mucosa. Shigella spp. evolved into pathogens by the acquisition of virulence genes and by the deletion of 'antivirulence' genes detrimental to its pathogenic lifestyle. An example is cadA (encoding lysine decarboxylase), which is uniformly absent in Shigella spp., whereas it is present in nearly all isolates of the closely related non-pathogen Escherichia coli. Here, using monolayers of T84 cells to model the human intestinal epithelium, we determined that the introduction of cadA into S. flexneri and the expression of lysine decarboxylase attenuated the bacteria's ability to induce PMN influx across model intestinal epithelium. Such inhibition was caused by cadaverine generated from the decarboxylation of lysine. Cadaverine treatment of model intestinal epithelia specifically inhibited S. flexneri induction of PMN transepithelial migration, while having no effect on the ability of Salmonella or enteropathogenic E. coli (EPEC) to induce PMN migration. These observations not only provide insight into mechanisms of S. flexneri pathogen evolution and pathogenesis, but also suggest a potential for the use of cadaverine in the treatment of dysentery.

Immunosuppressive effect of budesonide on human lamina propria lymphocytes

Budesonide, a beta-adreno-receptor agonist, is comparable to corticosteroid in the treatment of patients with inflammatory bowel disease with the advantage of minimal side effect. Although the immunomodulatory effects of budesonide on the circulatory and respiratory mucosal immune system have been reported, its effect on the human gut immune system has not been published. In this study, the effect of budesonide on the human gut immune system was compared to methyl-prednisolone. The cellular immune function was measured in-vitro by DNA synthesis, ornithine decarboxylase (ODC) activity and TNFalpha secretion. We found that both drugs have a comparable inhibitory effect on DNA synthesis, ODC activity and suppression of TNFalpha secretion. Exogenous addition of IL-2, did not restore the antiproliferative effect of both drugs. We conclude that budesonide has a comparative suppressive effect to methyl-prednisolone on the gut immune system which is not related to IL-2 secretion. The antiproliferative response may explain the therapeutic effect of budesonide on patients with inflammatory bowel disease.

Polyamine uptake across the basolateral membrane of the enterocyte is mediated by a high-affinity carrier: a study using isolated basolateral membrane vesicles

BACKGROUND/AIMS

Polyamine uptake from the circulation plays an important role in the maintenance of the intracellular polyamine content during extensive proliferation in intestinal mucosal cells.

METHODS

Isolated basolateral membrane vesicles of the rabbit enterocyte were used to characterize polyamine transport across the basolateral side of the intestinal epithelium. Incorporation of spermidine and spermine into the basolateral membrane was rapid, although 30-60% of polyamines were initially bound to the basolateral membrane. In order to avoid the influence of binding on the actual uptake into the vesicles, polyamine incorporation was measured at 37 and 4 degrees C, and kinetic parameters were calculated from the difference in polyamine incorporation rates at these temperatures.

RESULTS

Uptake kinetics was saturable, with Km values of 13.34 and 12.35 micromol/l and Vmax of 159 and 105 pmol/mg protein/ min for spermidine and spermine, respectively. It was also temperature dependent, with Q10 values (calculated between uptake velocities at 37 and 25 degrees C) of 2.56 for spermidine and 1.90 for spermine. At physiological pH, polyamine uptake was at its highest. Since at this pH polyamines are fully charged, charge might be essential for polyamines to be taken up across the basolateral membrane. Polyamine uptake was inhibited by di-, tri- and tetracations, and there was no evidence for sodium cotransport. Transport of putrescine was not inhibited by spermine and spermidine, although spermidine inhibited spermine uptake in a competitive manner, with Ki of 127 micromol/l.

CONCLUSION

These results imply that a saturable high-affinity transport system for polyamine does exist at the basolateral side of the enterocyte. Such a transport system may be responsible for the active transport of polyamine into rapidly proliferating enterocytes.

Quantitative and qualitative characterization of 1H NMR spectra of colon tumors, normal mucosa and their perchloric acid extracts: decreased levels of myo-inositol in tumours can be detected in intact biopsies

Sixteen colonic tumours and 10 normal mucosa biopsies have been examined by 1H NMR spectroscopy at 9.4 T. A complete characterization and quantification of the aliphatic region of PCA extract spectra and the analysis of the two-dimensional COSY spectra of five pairs of intact biopsies (tumor and control mucosa) has been carried out. The analysis of the PCA extracts demonstrated a significant increase in the concentration of the endogenous compounds: lactate, glutamate, aspartate, taurine, spermine, glutathione and glycerophosphoethanolamine, and a significant decrease of myo- and scyllo-inositol, in tumours with respect to mucosae. Among these metabolites, the high myo-inositol and taurine levels and the reciprocal changes found between them in tumours and mucosae make their resonances interesting as possible malignancy markers if they are detectable in vivo. In contrast to the easy observation of taurine in one-dimensional spectra of intact biopsies, the difficulty of observing myo-inositol prompted us to use two-dimensional COSY spectra for the detection and quantification of both these metabolites. In the two-dimensional spectra, the use of a ratio between the cross-peak volumes of both metabolites permits an excellent differentiation between tumours and normal mucosa and suggests its potential to detect malignant changes in the healthy tissue, provided a two-dimensional approach is used.

Neuropeptide Y (NPY) enhances proliferation of human colonic lamina propria lymphocytes

Neuropeptide Y (NPY) is one member of a family of peptides with a wide range of physiological effects on the CNS, cardiovascular, and respiratory systems. NPY is widely distributed throughout the peripheral and central nervous systems. It has also been found within the colon, liver and gallbladder in close anatomic proximity to the mucosal immune system. In this study, we investigated the effect of NPY on human gut mucosal immune function. We examined colonic lamina propria lymphocyte (LPL) proliferation by measuring DNA synthesis, ornithine decarboxylase (ODC) activity, and polyamine biosynthesis. NPY enhanced ODC activity and polyamine biosynthesis in Con A-stimulated LPL, and enhanced thymidine incorporation into Con A-stimulated LPL but not into monocyte-depleted LPL. Moreover, exogenous IL1-beta partially restored NPY's stimulatory effect on monocyte-depleted LPL DNA synthesis. Our results demonstrate that NPY enhances human colonic LPL proliferation and that this effect is partially IL1-beta dependent. Our data also suggest that NPY's effect may be mediated via polyamine biosynthesis. We postulate that the NPY may have an important impact on human mucosal immune function.

Ornithine decarboxylase (ODC) levels in children with reflux esophagitis

Reflux esophagitis is a common disease in infants and can be diagnosed largely by esophageal biopsy. In adults, chronic esophagitis may lead to Barrett's esophagus, a premalignant condition for esophageal cancer development. Ornithine decarboxylase (ODC) is used as an early marker for colon cancer development. No data are available on the role of ODC in reflux esophagitis in the pediatric population. In this study we retrospectively analyzed ODC activity in esophageal biopsies of children who underwent upper endoscopy. According to the esophageal histology, patients were divided into three groups: normal mucosa, mild, and moderate/severe esophagitis. None of our patients had esophageal metaplasia or cancer. ODC level was significantly higher in the moderate/severe esophagitis group compared to mild and normal mucosa group. We conclude that ODC activity is directly proportional to the severity of the esophageal inflammation/regenerative process in children with reflux esophagitis.

Regulation of ornithine decarboxylase in the kidney of autoimmune mice with the lpr gene

The lymphoproliferative lpr gene confers a lupus-like disease with lymphadenopathy, antinuclear antibody production, and glomerulonephritis in MRL-lpr/lpr mice. Upregulation of ornithine decarboxylase (ODC) activity and polyamine levels have been observed in the kidney and lymphoid organs of this strain. Inhibition of ODC with 0.5-1.5% (w/v) difluoromethylornithine (DFMO) in drinking water prolonged life-span and ameliorated renal disease. Glomerulonephritis is a major cause of morbidity and mortality in human and murine lupus. In order to elucidate the mechanism(s) of ODC regulation in lupus nephritis, we characterized ODC at the protein and mRNA levels in 3 strains of autoimmune mice with the lpr genetic background (MRL-lpr/lpr, C3H-lpr/lpr and C57BL/6J-lpr/lpr) using Western blotting, enzyme kinetics, turnover rate measurements, Northern blot hybridization, and reverse transcription-polymerase chain reaction (RT-PCR). Normal BALB/c mice were used as a control. We found that ODC activity in the kidney of lpr strains was 4- to 6-fold higher than that of BALB/c mice. The intensity of the major ODC protein band at 54 kD in Western blot was 4-fold higher in MRL-lpr/lpr and C3H-lpr/lpr kidney compared to that of BALB/c kidney. Putrescine levels were 2- to 4-fold higher in kidney of lpr strains than that of BALB/c and DFMO-treated MRL-lpr/lpr mice. DFMO treatment significantly reduced ODC activity and polyamine levels. The half-life of ODC enzyme in MRL-lpr/lpr, C3H-lpr/lpr, B6-lpr/lpr and BALB/c mouse kidneys was 15, 5, 8 and 23 min, respectively. There was no significant difference in the Km values of different strains, whereas Vmax values differed significantly. There was no difference in the level of SAMDC, another enzyme involved in the polyamine biosynthetic pathway, in various strain. Steady-state levels of ODC mRNA were lower in lpr strains compared to that of BALB/c mouse. Our results suggest that the basis for up-regulation of ODC is not at the transcriptional level, but may involve post-transcriptional modification(s) in lpr strains. The link between aberrant regulation of ODC and the immunopathogenesis of murine lupus nephritis indicates novel targets for lupus therapy.

Methionine metabolism: a window on carcinogenesis?

Recent experimental evidence links changes in methionine metabolism to the onset and progression of cancer. Aberrant methylation reactions and polyamine synthesis may alter genome stability, gene expression, and cell proliferation.

ODC activity and polyamine levels in isolated human colonocytes

Ornithine decarboxylase (ODC) is the first and often rate-limiting enzyme in polyamine biosynthesis. ODC and polyamines (putrescine, spermidine, spermine, and cadaverine) have an essential role in cell proliferation. In this study, we investigated ODC activity and the polyamine levels of normal human colonocytes isolated from the upper and lower crypt regions. We found no significant differences in ODC activity between upper and lower crypt regions (mean +/- SEM: 105 +/- 60 and 103 +/- 52 pmol CO2/mg protein/hr, respectively). This result was further substantiated by ODC immunoreactive antibody staining technique. Levels of polyamines (putrescine, spermidine, spermine, and cadaverine) were similar in the upper and lower crypt regions (mean +/- SEM; upper/lower: 79 +/- 29/79 +/- 18; 189 +/- 116/ 137 +/- 38; 174 +/- 58/204 +/- 35; and 52 +/- 10/51 +/- 10 nmol/mg protein, respectively). Acetyl-polyamines (acetyl-putrescine, acetyl-spermidine, and acetyl-spermine) levels in human colonocytes showed no significant differences between upper and lower crypt regions (mean +/- SEM; U/L: 368 +/- 109/408 +/- 89, 63 +/- 22/51 +/- 12, and 39 +/- 12/41 +/- 14 nmol/mg protein, respectively). Our results suggest that in isolated normal human colonocytes, ODC activity and polyamine levels are similar in the upper and the lower crypt regions.