Influence of Gastric pH Modifiers on Development of Intestinal Metaplasia Induced by X-Irradiation in Rats

The influence of gastric pH on intestinal metaplasia was examined in male Crj:CD(SD) rats. At the age of 5 weeks, animals were irradiated with two 10 Gy doses of X-rays to the gastric region at a 3-day interval (total 20 Gy), and 6 months after irradiation, received either secretin or histamine in silicon tubes for 2 months or had their bilateral submandibular salivary glands removed. The incidences of intestinal metaplasia in the fundus of animals after administration of secretin or histamine, or removal of the salivary glands were reduced, along with the pH values, as compared with values for rats given X-rays alone. In both the pyloric and the fundic gland mucosae, the numbers of alkaline phosphatase (ALP)-positive foci and type B metaplasias (intestinal crypts without Paneth cells) were also significantly decreased (P<0.01). In a second experiment, started six months after irradiation, rats were kept on 1% sodium chloride (NaCl) diet for 6 months. Subsequent removal of salivary glands along with histamine treatment brought about a marked drop in pH and in numbers of ALP-positive foci after three and five days. The present results thus indicated that development and maintenance of intestinal metaplasia can be influenced by a decrease of pH value.     

Relationship between gastric tumorigenesis and intestinal metaplasia in rats given x-radiation and/or N-methyl-N'-nitro-N-nitrosoguanidine

The influence of x-radiation and N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] on intestinal metaplasia and gastric tumorigenesis was examined in 5-week-old male Crj:CD(SD) rats. The animals were treated either with two 10-Gy fractions of x-rays separated by 3 days for a total of 20 Gy to the gastric region and/or with MNNG orally for 4 months. Simultaneous treatment with x-rays and MNNG (group II) and MNNG only (group IV) induced gastric tumors in the majority of the animals. Sequential treatment with x-radiation and MNNG, either x-ray 2 months prior to MNNG (group I) or MNNG 2 months prior to x-ray (group III), resulted in a lower incidence of gastric tumors as compared with the incidence after treatment with MNNG alone. The frequencies of intestinal metaplasia in the x-irradiated groups (groups I and V) were significantly higher than those in group II, III, or IV. The incidence of intestinal metaplasia and of gastric tumor was inversely proportional. These results indicate that intestinal metaplasia does not play a role in the induction of gastric tumors by MNNG.     

The Effects of Sodium Chloride, Miso or Ethanol on Development of Intestinal Metaplasia after X-Irradiation of the Rat Glandular Stomach

The influence of sodium chloride (NaCl), miso (Japanese soybean paste) and ethanol on development of intestinal metaplasia was examined. Five-week-old male CD(SD): Crj rats were treated with two 10 Gy doses of X-rays to the gastric region at a 3-day interval (total 20 Gy). After irradiation, the rats received supplementation with NaCl (1% or 10% in diet), miso (10% in diet) or ethanol (10% in drinking water) for 12 months. The number of alkaline phosphatase-positive foci of intestinal metaplasia in rats given 1% NaCl diet (Group 3) after X-rays was significantly elevated as compared to that in rats given X-rays alone (Group 1) ( P < 0.01) or X-rays with 10% NaCl (Group 2) ( P < 0.01). In the pyloric gland mucosae, the total numbers of metaplastic foci in rats of Group 3 were much higher than in Group 2, or after miso diet (Group 4) or ethanol supplementation (Group 5) ( P < 0.01), but no difference was found between Group 2, 4 or 5 and Group 1. Atypical hyperplasia only appeared at incidences of less than 6% in Groups 1–3 and no promoting effect on gastric tumorigenesis was evident in Group 2. The present results thus showed that the occurrence of intestinal metaplasia induced by X-irradiation can be significantly increased by administration of 1% NaCl and decreased by 10% NaCl and ethanol, but this is not associated with any influence on gastric neoplasia.     

The effects of sodium chloride, miso or ethanol on development of intestinal metaplasia after X-irradiation of the rat glandular stomach.

The influence of sodium chloride (NaCl), miso (Japanese soybean paste) and ethanol on development of intestinal metaplasia was examined. Five-week-old male CD(SD): Crj rats were treated with two 10 Gy doses of X-rays to the gastric region at a 3-day interval (total 20 Gy). After irradiation, the rats received supplementation with NaCl (1% or 10% in diet), miso (10% in diet) or ethanol (10% in drinking water) for 12 months. The number of alkaline phosphatase-positive foci of intestinal metaplasia in rats given 1% NaCl diet (Group 3) after X-rays was significantly elevated as compared to that in rats given X-rays alone (Group 1) (P < 0.01) or X-rays with 10% NaCl (Group 2) (P < 0.01). In the pyloric gland mucosae, the total numbers of metaplastic foci in rats of Group 3 were much higher than in Group 2, or after miso diet (Group 4) or ethanol supplementation (Group 5) (P < 0.01), but no difference was found between Group 2, 4 or 5 and Group 1. Atypical hyperplasia only appeared at incidences of less than 6% in Groups 1-3 and no promoting effect on gastric tumorigenesis was evident in Group 2. The present results thus showed that the occurrence of intestinal metaplasia induced by X-irradiation can be significantly increased by administration of 1% NaCl and decreased by 10% NaCl and ethanol, but this is not associated with any influence on gastric neoplasia.     

Gastric Tumorigenicity of 1,2-Dimethylhydrazine on the Background of Gastric Intestinal Metaplasia Induced by X-Irradiation in CD (SD) Rats

Five-week-old male CD (SD) rats were X-irradiated with a total of 20 Gy in 2 equal fractions with a 3-day interval. After the second irradiation, rats were fed normal diet supplemented with 1% sodium chloride, which is known to increase intestinal metaplasia. 1,2-Dimethylhydrazine (DMH) solution was injected i.m. into the back musculature at a dose of 20 mg/kg body weight weekly for 10 weeks, beginning 20 weeks after the final irradiation. Twelve months after the initial carcinogen treatment, gastric tumors in the glandular stomach were observed in 2 (3 lesions) of 30 animals in the X-irradiated and DMH-treated group fed diet supplemented with 1% sodium chloride. No gastric tumors were observed in the group which excluded X-irradiation from the experimental protocol.     

Pyloric gland phenotypic expression of gastric cancers developing in the rat fundic glandular stomach

Mucin histochemistry of experimental gastric cancers induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine or 4-nitroquinoline 1-oxide was analysed by labelled lectin staining for concanavalin A (Con A) after prior periodate oxidation (paradoxical Con A staining) or Arachis hypogarea agglutinin (peanut lectin, PNA) with or without prior periodate oxidation. In the digestive tracts of control-group rats the mucins were classified into class II or III by paradoxical Con A staining. Class II mucins were found in surface mucous cells, goblet cells and the surface coat of intestinal absorptive cells, while class III mucins were present in mucous neck cells, pyloric gland cells and Brunner's gland cells. Although class III mucins showed PNA reactivity, those in pyloric gland cells selectively lost positive staining after 1-4 h oxidation with periodate. Thus phenotypic expression of class III mucin-positive cells in the gastric mucosa could be further classified into mucous-neck-cell type and pyloric-gland-cell type on the basis of this sensitivity to periodate oxidation. Metaplastic cells in fundic mucosa and almost all class III mucin-positive cells in adenomatous hyperplasias, well-differentiated adenocarcinomas and signet-ring cell carcinomas, which developed in both fundic and pyloric mucosae, showed pyloric gland phenotypic expression.     

Effect of X-irradiation on the stomach of the rat

A model for localized 300 kV X-irradiation of the rat stomach was developed. After irradiation with single doses, three distinct gastric disorders were observed which occurred at different latency times. Acute death 2-3 weeks after irradiation was caused by an erosive and ulcerative gastritis and occurred in all animals given 28.5 Gy without diet, in 17% of the animals given 28.5 Gy plus diet, and in 13% of the animals given 23 Gy. Subacute to chronic fatal disorders 4 weeks to 7 months after irradiation were seen as stomach dilatation and gastroparesis, associated with the replacement of the normal gastric mucosa by a hyperkeratinized multilayered squamous epithelium. These disorders occurred in 40-100% of the animals after doses between 16 Gy and 28.5 Gy (+diet). An ED 50 value of 19.2 Gy (16.5-21.2 Gy, 95% confidence interval) was calculated for this gastroparesis. Late gastric obstruction exceeding 7 months after irradiation was seen in the rats because of profound changes in the gastric wall in 13-18% of the animals after doses between 23 Gy and 14 Gy. In animals surviving these three periods, an atrophic mucosa and intestinal metaplasia developed. From functional and morphohistological studies, it can be concluded that there are differences in the pathogenesis of the fatal radiation damage for each of these periods after irradiation.     

Clinicopathological analysis of synchronous multiple gastric carcinoma

Clinicopathological analysis was performed on 839 cases surgically resected for gastric carcinoma. The incidence of multiple gastric carcinoma was 4.8% (40 cases, 97 lesions). Multiple carcinoma was more frequently observed in early than in advanced carcinoma (P less than 0.01). The rate of intestinal type lesions was significantly (P less than 0.01) higher in multiple than in single gastric carcinoma, and all of the intestinal type carcinoma correlated with intestinal metaplasia, which is assumed to be closely related to pyloric and atrophic fundic gland area. Eight cases (20.0%) of multiple carcinoma were both in the upper one-third and lower one-third of the stomach. Twenty-nine (51.9%) of the accessory lesions were not detected pre-operatively; 12 (21.1%) of them were detected only by postoperative histology. Twelve (48.0%) of 25 early cancerous foci located in the anterior wall and greater curvature were overlooked before operation. These results indicate that the whole stomach must be carefully examined to detect accessory carcinoma before gastric surgery, especially for intestinal type carcinoma, with greater attention paid to the anterior wall and greater curvature, and that complete removal of the pyloric and atrophic fundic gland area would be required for distal gastrectomy.     

Gastric tumor induction by 1,2-dimethylhydrazine in Wistar rats with intestinal metaplasia caused by X-irradiation.

Five-week-old male Wistar rats were X-irradiated with a total of 20 Gy in 2 equal fractions at a 3-day interval. 1,2-Dimethylhydrazine (DMH) solution was injected i.m. into the back musculature at a dose of 20 mg/kg body weight weekly for 10 weeks, beginning 20 weeks after the final irradiation. Twelve months after the initial carcinogen treatment, tumors in the fundus of the glandular stomach were observed in 5 of 23 animals receiving both X-irradiation and DMH treatment. No tumors of the glandular stomach were observed in the DMH and X-ray alone or nontreatment groups. It is concluded that the presence of intestinal metaplasia may increase sensitivity to the induction of gastric tumors by carcinogens like DMH.     

Gastric Tumor Induction by 1,2-Dimethylhydrazine in Wistar Rats with Intestinal Metaplasia Caused by X-Irradiation

Five-week-old male Wistar rats were X-irradiated with a total of 20 Gy in 2 equal fractions at a 3-day interval. 1,2-Dimethylhydrazine (DMH) solution was injected i.m. into the back musculature at a dose of 20 mg/kg body weight weekly for 10 weeks, beginning 20 weeks after the final irradiation. Twelve months after the initial carcinogen treatment, tumors in the fundus of the glandular stomach were observed in 5 of 23 animals receiving both X-irradiation and DMH treatment. No tumors of the glandular stomach were observed in the DMH and X-ray alone or nontreatment groups. It is concluded that the presence of intestinal metaplasia may increase sensitivity to the induction of gastric tumors by carcinogens like DMH.     

Atrophic gastritis, Epstein–Barr virus infection, and Epstein–Barr virus-associated gastric carcinoma

Background. The developmental process of Epstein–Barr virus (EBV)-associated gastric carcinoma (EBVaGC) has not been clearly demonstrated, especially in its relation to intestinal metaplasia and epithelial EBV infection. Methods. Gastritis and intestinal metaplasia was histologically evaluated in non-neoplastic gastric mucosa that surrounded early carcinoma of EBVaGCs (n = 23) and EBV-negative gastric carcinomas (GCs) (intestinal type, n = 139; diffuse type, n = 44). Helicobacter pylori infection was evaluated by immunohistochemistry. EBV infection in the gastric mucosa was examined by both RNA probe in situ hybridization (ISH) and polymerase chain reaction (PCR) for the BamHI-W region of EBV DNA, the latter of which was applied to the microdissected mucosa. Results. Marked grade of atrophy and moderate to marked grade of lymphocytic infiltration were significantly more frequent in EBVaGCs (74% and 78%, respectively), compared to intestinal-type (49% and 12%)and diffuse-type (27% and 12%) of EBV-negative GCs. Only 13% of EBVaGCs were surrounded by intestinal metaplasia, in contrast to 41% of intestinal-type EBV-negative GCs. Immunohistochemistry revealed nearly the same frequencies of H. pylori infection (70%) in three types of GCs. RNA probe ISH for EBV-DNA failed to identify any positive cells in nonneoplastic mucosa, including intestinal metaplasia. Two of 118 microdissected samples of EBVaGC and 5 of 62 samples of EBV-negative GCs showed amplification of EBV-DNA, consisting of 3 pyloric and 4 fundic but no metaplastic gland samples. Conclusions. EBVaGC may develop from rare EBV-infected epithelial cells with severe atrophic gastritis, but the process is not directly related to intestinal metaplasia or H. pylori infection. Received for publication on Sept. 22, 1998; accepted on April 27, 1999     

The influence of intestinal metaplasia on development of gastric tumors in wistar rats receiving x-rays and mnng, mnu or dmh

Five-week-old male Wistar:Crj rats received two 10 Gy doses of X-rays to the gastric region at a 3-day interval. Two months thereafter the animals were treated with 100 mg/liter of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 4 months in their drinking water, N-methyl-N-nitrosourea (MNU) 2 mg/l ml/weekly/ for a total of 10 times by gastric intubation, or dimethylhydrazine (DMH) 20 mg/kg i.m./weekly/20 times. After 1 year, the animals were sacrificeded. There was thus no direct evidence of a histogenetic link between intestinal metaplasia and gastric carcinogenesis in the present results.     

Immunocytochemical evidence for gastric proteases in adenocarcinoma of the stomach

When anti-sera to bovine pepsinogen and chymosin (rennin) was used, immunoreactive tumor cells were found in 12 of 23 gastric adenocarcinomas irrespective of the tumor subtype, degree of differentiation, or the presence or absence of intestinal metaplasia in the adjacent gastric mucosa. Nine of ten lymph node metastases contained immunoreactive tumor cells. Except for focal positively staining acini in Brunner's glands the antibodies did not stain normal small intestine or areas of intestinal metaplasia. Although intestinal metaplasia is a predisposing factor in gastric carcinoma it may be irrelevant to its histogenesis and differentiation. Instead, the mucus neck cells, being the stem cells of the normal gastric mucosa, may be the target of malignant transformation in gastric carcinoma.     

Distribution of beta-human chorionic gonadotropin-positive cells in noncancerous gastric mucosa and in malignant gastric tumors.

The authors examined the localization and behavior of beta-human chorionic gonadotropin (HCG)-positive cells in human gastric noncancerous mucosa and in gastric malignant tumors, using immunohistochemistry and the anti-beta-HCG antibody. The beta-HCG-positive cells were located mainly in the antral mucosa and were generally restricted to the neck portion of the pyloric glands, although a few were present in fundic glands of the gastric body. The beta-HCG-immunoreactive cells were found in gastric carcinomas in 53% of the 92 cases examined. These cells were observed more often in advanced carcinomas that were histologically poorly differentiated than in early carcinomas or in well-differentiated tumors, but this prevalence had no statistical significance. The presence of the beta-HCG-positive cells in the gastric carcinomas suggested no appreciable prognostic significance, even quantitatively. In the syncytiotrophoblast-like tumor cells seen in four gastric tumor samples with histologic features of a choriocarcinoma, immunoreactivity to the beta-HCG was striking. There was, however, no recognizable dominance in the number of beta-HCG-reactive cells in the noncancerous mucosa around the tumor.     

Enhanced lipid peroxidation in rat gastric mucosa caused by NaCl.

The effects of NaCl on lipid peroxidation levels in gastric mucosa and urine were investigated in male Wistar rats. The animals were fed NaCl-supplemented diet at concentrations of 4.0, 2.0, 1.0, 0.5, 0.25 and 0% (control) for 5 weeks. Further groups were maintained on the 4.0 or 0% NaCl diets and simultaneously administered 20 p.p.m. indomethacin dissolved in the drinking water. When the rats were killed, a dose-related increase of malondialdehyde (MDA) was found in both gastric mucosa and urine, the urinary MDA levels clearly correlating with those for stomach tissue. Cell proliferation of fundic mucosa was also significantly increased in rats fed 4.0 or 2.0% NaCl-supplemented diet. Indomethacin suppressed the 4% NaCl-associated MDA increase in both gastric mucosa and urine as well as the elevation in cell proliferation. The results clearly show that administration of NaCl, a gastric tumor promoter, is associated with enhanced lipid peroxidation in the gastric mucosa.     

Expression of group-II phospholipase A2 in malignant and non-malignant human gastric mucosa.

The expression of Group-II phospholipase A2 (M-PLA2) was analysed immunohistochemically in malignant, non-malignant (including atrophic, hyperplastic, pseudopyloric metaplastic and intestinal metaplastic) and normal human gastric mucosae. M-PLA2 was consistently detected in the stem cell lineage, pseudopyloric metaplasia and the generative cells of hyperplastic foveolar epithelium and intestinal metaplasia (IM). In IM, the appearance of M-PLA2 was found to be closely related to the degree of development of the brush borders on columnar cells and was especially prominent at dense brush borders. Paneth cells of IM, particularly their secretory products, were strongly immunoreactive for M-PLA2. In gastric cancer, the expression of M-PLA2 was detected exclusively in cancer cells with a low grade of differentiation, and seemed to be intensified in the invading zone of the tumour. These observations suggest that the expression of M-PLA2 is associated with the proliferative kinetics and regeneration of human gastric mucosa, and may indicate a physiological relationship between its expression and metaplasia of small intestinal type. Moreover, the appearance of M-PLA2 may be related to the invasive ability of gastric cancer.     

Lack of Any Positive Effect of Intestinal Metaplasia on Induction of Gastric Tumors in Wistar Rats Treated with N-Methyl-N-nitrosourea in Their Drinking Water

The influence of intestinal metaplasia on gastric cancer induction was examined in five-week-old male Wistan:Crj rats. The animals were first treated with two 10 Gy doses of X-rays to the gastric region at a 3-day interval (total 20 Gy) and then, starting two months after the irradiation, received 100 ppm N -methyl- N -nitrosourea (MNU) in their drinking water for 15 weeks. Thereafter they were maintained for 37 weeks with or without a dietary 1% sodium chloride (NaCl) supplement. The incidences of gastric adenocarcinomas in the MNU or MNU plus NaCl groups were significantly higher than in animals receiving X-rays plus MNU with or without NaCl. Intestinal metaplasias and the numbers of alkaline phosphatase(ALP)-positive foci were significantly increased in the X-ray irradiation groups but the numbers of ALP-positive foci were not increased with or without 1% NaCl. An inverse relationship between incidences of gastric tumors and intestinal metaplasias was apparent. The present experiment thus showed that the presence of intestinal metaplasia does not exert a positive influence on induction of gastric neoplasia by MNU in the rat.     

Phenotypic shift in human differentiated gastric cancers from gastric to intestinal epithelial cell type during disease progression

Background. The phenotypic expression of tumor cells is widely thought to resemble that of the tissue of origin. In the present study, to assess phenotypic changes that occur with disease progression, we investigated human differentiated gastric cancers at different depths of invasion for component cancer cell types. Methods. Using a combined mucin histochemical and immunohistochemical approach, we classified surgical specimens of 301 differentiated gastric cancers into three types: gastric epithelial cell (G) type, intestinal epithelial cell (I) type and mixed gastric and intestinal (GI) type, according to the phenotypic differentiation of the component cancer cells. The relation between the phenotypic type of cancer and their depth of invasion was evaluated. Results. The proportion of G type cancers was 41.4% in early (tumor invasion of mucosa or submucosa) cases, decreasing to 22.2% in advanced (tumor invasion of muscularis propia or deeper) cases, whereas the proportion of I type cancers increased with progressive disease from 23.5% to 31.1% (P < 0.01). Cancers invading the subserosa or deeper included more I type cases and fewer G type than cancers limited to the mucosa (P < 0.01). In most cases of each phenotypic type, intestinal metaplasia was recognized in the surrounding background mucosa, but no clear relation was shown between the phenotype of cancers and the degree of intestinal metaplasia in the background mucosa, suggesting that intestinal metaplasia is not always a preneoplastic lesion. Conclusions. A phenotypic shift from G to I type expression was observed with the progression of human differentiated gastric cancers. Intestinalization may occur independently in cancerous and noncancerous gastric mucosa. Received for publication on May 1, 1998; accepted on Oct. 22, 1998