Attenuation by all-trans-retinoic acid of sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

Metabolomics Analysis in Serum from Patients with Colorectal Polyp and Colorectal Cancer by 1H-NMR Spectrometry

Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. Colorectal adenomatous polyps are at high risk for the development of CRC. In this report, we described the metabolic changes in the sera from patients with colorectal polyps and CRC by using the NMR-based metabolomics. 110 serum samples were collected from patients and healthy controls, including 40 CRC patients, 32 colorectal polyp patients, and 38 healthy controls. The metabolic profiles and differential metabolites of sera were analyzed by multivariate statistical analysis (MSA), including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least squares discriminant analysis (OPLS-DA) methods. A total of 23 differential metabolites were identified from MSA. According to the pathway analysis and multivariate ROC curve-based exploratory analysis by using the relative concentrations of differential metabolites, we found abnormal metabolic pathways and potential biomarkers involved with the colorectal polyp and CRC. The results showed that the pyruvate metabolism and glycerolipid metabolism were activated in colorectal polyps. And the glycolysis and glycine, serine, and threonine metabolism were activated in CRC. The changed metabolism may promote cellular proliferation. In addition, we found that the rates of acetate/glycerol and lactate/citrate could be the potential biomarkers in colorectal polyp and CRC, respectively. The application of ¹H-NMR metabolomics analysis in serum has interesting potential as a new detection and diagnostic tool for early diagnosis of CRC.

Metabolomic analysis reveals altered metabolic pathways in a rat model of gastric carcinogenesis

Gastric cancer (GC) is one of the most malignant tumors with a poor prognosis. Alterations in metabolic pathways are inextricably linked to GC progression. However, the underlying molecular mechanisms remain elusive. We performed NMR-based metabolomic analysis of sera derived from a rat model of gastric carcinogenesis, revealed significantly altered metabolic pathways correlated with the progression of gastric carcinogenesis. Rats were histologically classified into four pathological groups (gastritis, GS; low-grade gastric dysplasia, LGD; high-grade gastric dysplasia, HGD; GC) and the normal control group (CON). The metabolic profiles of the five groups were clearly distinguished from each other. Furthermore, significant inter-metabolite correlations were extracted and used to reconstruct perturbed metabolic networks associated with the four pathological stages compared with the normal stage. Then, significantly altered metabolic pathways were identified by pathway analysis. Our results showed that oxidative stress-related metabolic pathways, choline phosphorylation and fatty acid degradation were continually disturbed during gastric carcinogenesis. Moreover, amino acid metabolism was perturbed dramatically in gastric dysplasia and GC. The GC stage showed more changed metabolite levels and more altered metabolic pathways. Two activated pathways (glycolysis; glycine, serine and threonine metabolism) substantially contributed to the metabolic alterations in GC. These results lay the basis for addressing the molecular mechanisms underlying gastric carcinogenesis and extend our understanding of GC progression.

Vitamin A, retinol, and carotenoids and the risk of gastric cancer: a prospective cohort study

BACKGROUND

Vitamin A may influence gastric carcinogenesis through its essential role in controlling cell proliferation and differentiation. However, epidemiologic studies of vitamin A, retinol (preformed vitamin A), and provitamin A carotenoids in relation to the risk of gastric cancer have documented inconsistent results.

OBJECTIVE

The objective of the study was to examine the associations between intakes of vitamin A, retinol, and specific carotenoids and the risk of gastric cancer in a prospective population-based cohort study of Swedish adults.

DESIGN

The study cohort consisted of 82 002 Swedish adults aged 45-83 y who had completed a food-frequency questionnaire in 1997. The participants were followed through June 2005.

RESULTS

During a mean 7.2-y follow-up, 139 incident cases of gastric cancer were diagnosed. High intakes of vitamin A and retinol from foods only (dietary intake) and from foods and supplements combined (total intake) and of dietary alpha-carotene and beta-carotene were associated with a lower risk of gastric cancer. The multivariate relative risks for the highest versus lowest quartiles of intake were 0.53 (95% CI: 0.32, 0.89; P for trend = 0.02) for total vitamin A, 0.56 (95% CI: 0.33, 0.95; P for trend = 0.05) for total retinol, 0.50 (95% CI: 0.30, 0.83; P for trend = 0.03) for alpha-carotene, and 0.55 (95% CI: 0.32, 0.94; P for trend = 0.07) for beta-carotene. No significant associations were found for beta-cryptoxanthin, lutein and zeaxanthin, or lycopene intake.

CONCLUSION

High intakes of vitamin A, retinol, and provitamin A carotenoids may reduce the risk of gastric cancer.

Expression of retinoid receptors in multiple cell lineages in the gastric mucosae of mice and humans

BACKGROUND AND AIM

In mice and humans, the gastric epithelial progenitors undergo proliferation and bipolar migration from the isthmus associated with their differentiation into mucus-, acid- and pepsinogen-secreting cell lineages. Little is known about factors that control the dynamics of these isthmal progenitor cells. Retinoids have long been known as chemopreventive agents against gastric mucosal damage and carcinogenesis. The aim of the present study was to examine the cellular localization of the various retinoid receptors proteins (RAR and RXR) in the gastric epithelium of mice and humans.

METHODS

Gastric antral biopsies of normal individuals and the oxyntic and antral regions of the mouse stomach were processed for immunohistochemistry using anti-RAR and anti-RXR antibodies. To label the progenitor cell zone, some sections were also probed with antibodies specific for proliferating cell nuclear antigen.

RESULTS

The immunoprobed oxyntic mucosal sections of the mice showed that RXRbeta protein was present in the epithelial isthmal cells, neck cells, zymogenic cells and some pit and parietal cells. In addition, RARbeta was found in isthmal and neck cells, and RARgamma was mainly found in neck cells. In the mouse antrum, only RXRbeta was detected in the isthmal cells and their pit and gland cell descendents. In humans, immunoprobed antral sections showed that RARbeta, RARgamma, RXRalpha and RXRgamma proteins are expressed in the isthmal, pit and gland cells.

CONCLUSIONS

Retinoid receptors are expressed in multiple cell lineages of the mouse and human gastric epithelium and may, therefore, account for the possible effects of retinoids on gastric epithelial cell proliferation and differentiation.

Differential expression of genes related to levels of mucosal cell proliferation among multiple rat strains by using oligonucleotide microarrays

Induction levels of cell proliferation, in response to gastric mucosal damage by N-methyl- N'-nitro- N-nitrosoguanidine (MNNG), are different among rat strains and correlate with susceptibility to MNNG-induced gastric carcinogenesis. Here, we used oligonucleotide microarrays to search for genes that show expression levels accordant with the extents of cell proliferation among six rat strains. Expression levels of 8,800 probe sets were analyzed in the pylorus of ACI, LEW, WKY (strains with strong cell proliferation), F344, (ACI x BUF)F1, and BUF rats (strains with weak cell proliferation) after 2-week MNNG treatment. No genes showed complete accordance, and 22 genes showed accordance with one or two exceptions. After confirmation by quantitative RT-PCR, four genes--cellular retinoic acid-binding protein II ( Crabp2), fatty acid binding protein 1 ( Fabp1), progastricsin (pepsinogen C, Pgc), and UDP-glucuronosyltransferase 2 family member 5 ( Ugt2b5)--were found to show good accordance with only one exception. Crabp2, Fabp1, and Ugt2b5 were differentially expressed between ACI and BUF rats both before and after MNNG treatment. Although Crabp2 had been identified as one of the 16 genes differentially expressed between ACI and BUF rats with cDNA-RDA, Fabp1 and Ugt2b5 were newly identified in this study. All three genes are known to be involved in retinoic acid-mediated signaling and could be involved in the control of differential induction of cell proliferation.

Retinoic acid increases expression of the calcium-binding protein S100P in human gastric cancer cells

Retinoids mediate a wide spectrum of antitumor activities through induction of growth arrest, differentiation or apoptosis. To determine whether the effects of retinoids are mediated by specific gene activation or repression, one-day treatments of SC-M1 CL23 gastric cancer cells with vehicle alone or all-TRANS retinoic acid (tRA) (10 microM) were compared using differential display analysis. A 432-bp cDNA fragment from the tRA-treated cells was differentially amplified and its sequence analysis indicated homology with the calcium-binding protein S100P. Levels of S100P mRNA were increased 3.5-fold in SC-M1 CL23 gastric cancer cells treated with 10 microM tRA for 1 day, and the regulation was time- and concentration-dependent. Treatment with tRA (10 microM) also increased S100P mRNA levels in tRA-sensitive HtTA cells but not in inherent RA-resistant TMC-1 cells. However, the tRA-mediated increase in S100P expression was maintained in SC-M1/R cells that were established long-term in tRA-containing medium and had acquired partial RA resistance to tRA-induced growth suppression. In conclusion, tRA increases S100P expression, and the regulation remains intact in cells which develop acquired RA resistance.

Suppression by iron chelator phenanthroline of sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

The effect of prolonged administration of iron chelator phenanthroline on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labeling and apoptotic indices in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and intraperitoneal injections of phenanthroline at doses of 15 or 30 mg/kg body weight every other day. At week 52, feeding of sodium chloride significantly increased the incidence of gastric cancers, as compared with the control group. Prolonged injections of phenanthroline at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral supplementation with sodium chloride. Phenanthroline at both doses significantly decreased the labeling index of gastric cancers, which was enhanced by sodium chloride, and significantly increased the apoptotic index of gastric cancers, which was lowered by sodium chloride. In vitro examination using electron spin resonance revealed that sodium chloride promotes the production of hydroxyl radical during Fe(2+) oxidation by Fenton's reaction. These findings suggest that enhancement by sodium chloride of gastric carcinogenesis may be mediated by hydroxyl radicals.

Apoptosis induced by ischemia-reperfusion and fasting in gastric mucosa compared to small intestinal mucosa in rats

The effect of ischemia-reperfusion and 48-hr fasting on apoptosis was characterized in rat gastric mucosa and compared to small intestinal mucosa. Under halothane anesthesia, the celiac artery or superior mesenteric artery in the rat was occluded for 60 min followed by reperfusion. Occlusion of the celiac artery reduced blood flow in the stomach and occlusion of the mesenteric artery reduced blood flow in the small intestine. Additional rats were fasted for 48 hr to evaluate the effect of fasting on mucosal apoptosis. The ratios of fragmented DNA to total DNA, electrophoresis, and immunohistochemical staining were examined after ischemia-reperfusion or fasting. Apoptosis was not induced significantly in the gastric mucosa after ischemia-reperfusion, although it increased dramatically in the intestinal mucosa after ischemia-reperfusion. Further, after 48 fasting, apoptosis was induced in the small intestine, but not in the stomach. These results indicate that rat gastric mucosa is not as sensitive as small intestinal mucosa to ischemia-reperfusion or fasting-induced apoptosis.

K-ras point mutation is associated with enhancement by deoxycholic acid of colon carcinogenesis induced by azoxymethane, but not with its attenuation by all-trans-retinoic acid

The effects of deoxycholic acid (DCA) with and without all-trans-retinoic acid (ATRA) on the incidence of colon tumors induced by azoxymethane, the incidence of K-ras point mutation in colon tumors and the labeling index of colon mucosa were investigated in male Wistar rats. Rats received 5 weekly injections of 7.4 mg/kg body weight of azoxymethane. From the start of the experiment, all rats in 3 groups also received chow pellets containing 0.3% DCA with and without s.c. injections of 0.75 or 1.5 mg/kg body weight of ATRA every other day until the end of week 45. Oral administration of DCA significantly increased the incidence of colon tumors in week 45. Concomitant use of DCA and ATRA at either dose significantly attenuated the enhancement by DCA of colon tumorigenesis. Administration of DCA significantly increased the incidence of K-ras point mutation in colon tumors and the labeling index in the colon mucosa. Combined administration of DCA and ATRA significantly reduced the labeling index of colon mucosa, which was increased by DCA, but did not affect the incidence of K-ras point mutation in colon tumors. These findings suggest that DCA enhances development of colon tumors and that this enhancement is attenuated by ATRA. A possible mechanism of this enhancement is induction of K-ras point mutation. However, decreased cell proliferation in the colon mucosa may be closely related to the attenuation of DCA-enhanced colon tumorigenesis, but not suppression of K-ras point mutation.

Suppression by Chai-hu-gui-zhi-tang of the development of liver lesions induced by N-nitrosomorpholine in Sprague-Dawley rats

The effects of Chai-hu-gui-zhi-tang (TJ-10) on the development of liver lesions induced by N-nitrosomorpholine and on labeling and apoptotic indices were investigated in male Sprague-Dawley rats. Rats were given chow pellets containing 0.5 or 1.0% TJ-10 and, from the beginning of the experiment, were given drinking water containing N-nitrosomorpholine for 8 weeks. Visible white liver nodules, cellular alteration foci, and hepatic foci staining positively for glutathione-S-transferase, placental type, were examined macroscopically or histochemically. In week 16, TJ-10 at both dosages significantly reduced the incidence, and/or number of visible white nodules and hepatic lesions. Quantitative histologic analysis also showed that prolonged feeding of TJ-10 at both dosages significantly reduced the number of hepatic foci positive for glutathione-S-transferase, placental type. Administration of TJ-10 at both dosages also significantly decreased the labeling index of adjacent liver and significantly increased the apoptotic index of adjacent liver but had no significant effect on those of neoplastic lesions. These findings indicate that TJ-10 suppresses the development of liver lesions and suggest that this effect might be related to TJ-10's inhibition of cell proliferation and induction of apoptosis in adjacent hepatocytes.