Shuji Kanayama

Peroxisome Proliferator-activated Receptor γ Induces Growth Arrest and Differentiation Markers of Human Colon Cancer Cells

Peroxisome proliferator‐activated receptor γ (PPARγ), one of the nuclear receptors expressed in adipose tissue, plays an important role in adipocyte differentiation. In this study, we investigated the expression of PPARγ and its role in cellular growth and differentiation in six colon cancer cell lines: HT‐29, CaCo‐2, SW‐480, DLD‐1, LoVo, and T‐84. All six expressed PPARγ mRNA and protein, shown respectively on northern and western blot analyses. Luciferase assay in HT‐29 cells, which strongly express PPARγ showed that troglitazone, a selective ligand for PPAR?, transacti‐vated the transcription of a peroxisome proliferator response element (PPRE)‐driven promoter. Furthermore, troglitazone caused a marked decrease in [3H] thymidine incorporation and G1 cell‐cycle arrest determined by flow cytometry. Finally, troglitazone induced expression of mRNAs for villin and intestinal alkaline phosphatase, markers for enterocyte differentiation. In conclusion, human colon cancer cells express PPARγ, the ligands of which inhibit cell growth and induce differentiation markers.

Effects of a novel cholecystokinin (CCK) receptor antagonist, MK-329, on gallbladder contraction and gastric emptying in humans. Implications for the physiology of CCK.

To explore the physiology of cholecystokinin (CCK) in humans, we investigated the effect on gallbladder contraction and gastric emptying of a recently developed CCK receptor antagonist, MK-329. In a double-blind, four-period crossover study eight subjects received single doses of 0.5, 2, or 10 mg MK-329, or placebo, followed by an intravenous infusion of CCK-8 (30 pmol/kg.h). In placebo-treated subjects gallbladder volumes decreased on average to 43% of initial volumes after 2 h of CCK infusion. MK-329 caused a dose-dependent inhibition of CCK-stimulated gallbladder contraction with 10 mg producing complete blockade (P less than 0.01, cf. placebo). Gallbladder contraction and gastric emptying rates after a mixed meal were then measured in a two-period crossover study. Subjects received placebo or 10 mg of MK-329 2 h before eating. Gastric emptying of both solids and liquids was measured simultaneously by gamma scintigraphy. In placebo-treated subjects plasma CCK levels increased postprandially to 2.3 pM, gallbladder volumes decreased 68.4 +/- 3.8% (SE), and the times for 50% emptying of liquids and solids from the stomach were 58 +/- 10 and 128 +/- 8 min, respectively. In MK-329-treated subjects there was a marked elevation in peak CCK levels to 13.8 pM (P less than 0.01, cf. placebo), and gallbladder contraction was completely inhibited. Solid and liquid emptying rates were unaffected. These findings demonstrate that (a) MK-329 is a potent, orally active antagonist of CCK in humans, and (b) CCK is the major regulator of postprandial gallbladder contraction. These data also support the concept of negative feedback regulation of CCK secretion and suggest that mechanisms other than CCK play a dominant role in the regulation of postprandial gastric emptying rates.

STAT3 mediates the survival signal in oncogenic ras-transfected intestinal epithelial cells.

The oncogenic ras mutation is a common and critical step in gastrointestinal carcinogenesis. In a previous study, we demonstrated that oncogenic ras activated the EGF‐related peptide autocrine loop and that the apoptosis resistance observed in the oncogenic ras‐stimulated cell (IEC‐ras cell) was dependent on this activated EGF‐related peptide autocrine loop. STATs (signal transducers and activators of transcription), first identified as intracellular signal transducers stimulated by cytokines, are known to also be activated by EGF. However, the role of STATs in the survival signal of IEC‐ras cells is not clear. In the present study, we demonstrate that STAT3 is constitutively activated in ras‐stimulated cells and that STAT3 activation is considerably suppressed by the EGF‐specific receptor kinase inhibitor AG1478. We also show that disruption of the STAT3 pathway by introduction of a dominant‐negative STAT3 mutant abolishes the apoptosis resistance against UVC and MMC treatment observed in IEC‐ras cells without affecting proliferation. Moreover, the expression of Bcl‐2 and Bcl‐xL, apoptosis‐suppressive proteins, is reduced in dominant‐negative STAT3‐transfected cells. Thus, STAT3 appears to be an important mediator of the anti‐apoptotic signal in IEC‐ras cells. Int. J. Cancer 78:326–330, 1998.© 1998 Wiley‐Liss, Inc.

Gastrin Induces Heparin-Binding Epidermal Growth Factor-like Growth Factor in Rat Gastric Epithelial Cells Transfected With Gastrin Receptor

BACKGROUND & AIMS Parietal cells express heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF). However, it is unknown whether HB-EGF mediates the trophic action of gastrin. The purpose of this study was to determine whether gastrin modulates the expression of HB-EGF, which mediates the proliferative effects of gastrin on gastric epithelial cells. METHODS RGM1 cells, a rat gastric epithelial cell line, were transfected with a human gastrin receptor complementary DNA. Gastrin induction of messenger RNAs (mRNAs) for EGF-related polypeptides was assayed by Northern blotting. Processing of cell surface-associated proHB-EGF and secretion of HB-EGF were determined by flow cytometry and Western blotting, respectively. Tyrosine phosphorylation of the EGF receptor was assayed by immunoprecipitation and Western blotting with an antiphosphotyrosine antibody. Cell growth was evaluated by [3H]thymidine incorporation. RESULTS Gastrin induced expression of HB-EGF mRNA, processing of proHB-EGF, release of HB-EGF into the medium, and tyrosine phosphorylation of the EGF receptor. The growth-stimulatory effects of gastrin were partly inhibited by anti-rat HB-EGF serum and completely blocked by AG1478, an EGF receptor-specific tyrphostin. CONCLUSIONS The findings suggest that HB-EGF at least partially mediates the proliferative effects of gastrin on gastric epithelial cells.

High Fas ligand expression on lymphocytes in lesions of ulcerative colitis

Background—The pathogenesis of ulcerative colitis is unclear, but cytotoxic T lymphocytes infiltrating the mucosa have been implicated in mucosal damage. The Fas ligand (FasL), expressed on cytotoxic T lymphocytes, induces apoptosis in cells expressing Fas. Aim—To analyse FasL expression in affected colonic mucosa to ascertain Fas-FasL interaction in ulcerative colitis. Methods—FasL mRNA was quantified in colonic mucosal specimens from healthy subjects and patients with ulcerative colitis or Crohn’s disease, using the competitive reverse transcription polymerase chain reaction. FasL mRNA localisation was determined by in situ hybridisation. Expression of Fas in colonic mucosa was analysed immunohistochemically. Phenotypes of lamina propria lymphocytes that expressed FasL were analysed by flow cytometry. Results—FasL mRNA was strongly expressed in active ulcerative colitis lesions, but not in those associated with active Crohn’s disease or active proctitis-type ulcerative colitis. In situ hybridisation showed that FasL mRNA expression occurred in mononuclear cells infiltrating lesions. Fas was expressed in epithelial cells in ulcerative colitis and Crohn’s disease, and in normal subjects. Cytometry showed that FasL was expressed in CD3 lymphocytes infiltrating the lamina propria in active lesions. Conclusions—FasL is expressed in CD3 lymphocytes infiltrating into ulcerative colitis but not Crohn’s disease lesions, suggesting that Fas-FasL induced apoptosis participates in the mucosal damage of ulcerative colitis.

Localization of heparin-binding epidermal growth factor-like growth factor in human gastric mucosa.

BACKGROUND & AIMS Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been recently identified as a member of the EGF family. EGF receptors to which HB-EGF can bind have been detected in some types of gastric epithelial cells. The aim of this study was to investigate whether HB-EGF is produced in gastric epithelial cells to maintain normal gastric mucosa. METHODS Gene expression and production of HB-EGF protein were investigated using Northern hybridization and immunohistochemistry, and the types of cells producing this protein were determined in human gastric mucosa. RESULTS HB-EGF messenger RNA was detected in the body and antrum. Immunohistochemical staining showed that HB-EGF was localized mainly in parietal cells of fundic glands and in gastrin cells of pyloric glands. Also, the immunoreactivity of EGF receptors was observed in parietal cells and gastrin cells and faintly in surface epithelial cells and mucous neck cells of the proliferative zone. CONCLUSIONS The results suggest that HB-EGF is synthesized mainly in parietal cells and gastrin cells and may act in an autocrine and/or paracrine manner in the regulation of proliferation and differentiation of the gastric mucosal cells through their surface EGF receptors.

Improved fold width and increased acid secretion after eradication of the organism in Helicobacter pylori associated enlarged fold gastritis.

This study examined the effects of eradication of Helicobacter pylori (H pylori) infection on gastric mucosal morphology and acid secretion. Sixteen H pylori positive patients with enlarged gastric body folds were divided into two groups: (a) patients with moderate enlargement (fold width: 6 to 10 mm, n = 8) and (b) patients with severe enlargement (> 10 mm, n = 8). After successful treatment, gastric body fold width was reduced in both groups (p < 0.01) with an associated decrease in inflammatory infiltrates in the body mucosa (p < 0.01 and p < 0.05). Basal acid output and tetragastrin stimulated maximal acid output (mean (SEM)) in all 16 patients significantly increased from 1.1 (0.5) to 2.9 (0.9) mmol/h (p < 0.05) and from 5.4 (1.3) to 18.7 (2.3) mmol/h (p < 0.01), respectively, with a significant decrease in fasting serum gastrin concentrations, from 127.1 (16.1) to 59.6 (3.8) pg/ml (p < 0.01). The increase in acid secretion after eradication of H pylori was more noticeable in the severe group, who had shown lower acid secretion and higher serum gastrin concentrations (p < 0.05) before eradication, than the increase seen in the moderate group. The decreases in ammonia nitrogen content seen after eradication were significant in basal (from 0.91 (0.17) to 0.37 (0.08) mmol/h, p < 0.05) and stimulated gastric secretions (from 1.57 (0.19) to 0.37 (0.13) mmol/h, p < 0.01), although these changes were too small to explain the increases in basal acid output and maximal acid output. These results suggest that inflammation of the gastric body mucosa caused by H pylori infection is associated with enlarged gastric body folds and inhibition of acid secretion in H pylori positive patients with enlarged gastric body folds.

Increased production of interleukin 1 beta and hepatocyte growth factor may contribute to foveolar hyperplasia in enlarged fold gastritis.

BACKGROUND AND AIMS: It has been reported that eradication of Helicobacter pylori improves fold width in H pylori associated enlarged fold gastritis. The aim of this study was to clarify the mechanism of fold thickening in this condition. PATIENTS AND METHODS: In eight patients with enlarged fold gastritis and 13 patients without enlarged folds, the presence of H pylori infection, inflammatory infiltrates, mucosal plasia, and epithelial cell proliferation in the body mucosa were investigated, and production of transforming growth factor alpha (TGF alpha), hepatocyte growth factor (HGF), and interleukin 1 beta (IL 1 beta) was determined by a competitive reverse transcription/polymerase chain reaction method and in vitro short-term culture of biopsy specimens. RESULTS: In the patients with enlarged fold gastritis, inflammatory infiltrates including macrophages increased with H pylori colonisation in the body. Foveolar thickness and proliferating cell nuclear antigen (PCNA) labelling index were increased. Messenger RNA levels of HGF, but not TGF alpha, were increased, and release of HGF and IL 1 beta was increased. HGF release, which was positively correlated with IL 1 beta release and foveolar thickness, decreased in the presence of IL 1 receptor antagonist. After eradication of H pylori, inflammatory infiltrates, IL 1 beta and HGF release decreased with concomitant decreases in PCNA labelling index, foveolar thickness and fold width. CONCLUSIONS: Increased IL 1 beta and HGF production caused by H pylori infection may contribute to fold thickening of the stomach by stimulating epithelial cell proliferation and foveolar hyperplasia in patients with enlarged fold gastritis.

Over-expression of bcl-xL gene in human gastric adenomas and carcinomas

The present study was designed to clarify whether bel‐xL is involved in the development of carcinoma in the stomach. Levels of bel‐xL and bc1‐2 mRNA were determined by a reverse‐transcription/polymerase‐chain reaction in endoscopic gastric biopsy specimens from 10 control subjects, 11 patients with adenomas and 14 patients with carcinomas. In 6 of 11 adenomas, 5 of 8 early carcinomas and 3 of 6 advanced carcinomas, the bel‐xL gene was over‐expressed. In carcinomas, overexpression of the bel‐xL gene was observed in 6 of 9 intestinaltype carcinomas and 2 of 5 diffuse‐type carcinomas. No correlation was observed between bel‐xL and bc1‐2 gene expression. In cases in which the bel‐xL gene was over‐expressed, an apparent increase in the protein level of Bcl‐xL was observed by immunoblot analysis and intense Bcl‐x immunoreactivity was detected immunohistochemically within the tumor cells. In conclusion, we showed that bel‐xL is over‐expressed in gastric carcinomas at both the RNA and protein levels, suggesting that overexpression of bel‐xL may play a role in gastric carcinogenesis.

Helicobacter pylori -induced enlarged-fold gastritis is associated with increased mutagenicity of gastric juice, increased oxidative DNA damage, and an increased risk of gastric carcinoma

Background and Aim:  The severe inflammation, increased cell proliferation and marked acid inhibition observed in subjects with Helicobacter pylori‐associated enlarged‐fold gastritis suggest that enlarged‐fold gastritis may be a risk factor for gastric carcinoma. The purpose of the present study was to determine whether a relationship exists between enlarged‐fold gastritis and gastric carcinoma.