Effect of bile acid gavage or vagotomy and pyloroplasty on gastrointestinal carcinogenesis

Carcinogenic potential of duodenal reflux juice from patients with long-standing postgastrectomy

AIM: To determine whether study on the carcinogenic potential of reflux juice from patients with remote gastrectomy could clarify the inherent relationship between duodenal reflux and gastric stump cancer.

METHODS: A total of 37 reflux juice samples (13 Billroth I, 24 Billroth II) were employed in the present study. A two-stage transformation assay using BALB/c 3T3 cells was carried out to test the initiating or promoting activity of these samples.

RESULTS: Two of 18 (11.1%) reflux samples exerted initiating activities, whereas 9/19 (47.4%) samples enhanced the MNNG-initiating cell transformation, suggesting the duodenal reflux juice might more frequently possess the tumor-promoter activity (P = 0.029). In addition, there was no difference in initiating activities of the samples irrespective of surgical procedures (P = 0.488), while Billroth II samples exhibited stronger tumor-promoter activity than Billroth I samples (P = 0.027). Furthermore, the promoter activities were well correlated with the histological changes of the stomas (r_s = 0.625, P = 0.004), but neither their cytotoxicities nor initiating activities had this correlation (Probabilities were 0.523 and 0.085, respectively).

CONCLUSION: The duodenal reflux juice from patients with remote postgastrectomy did have carcinogenic potential, and suggested that tumor-promoting activity should principally account for the high incidence of gastric cancer in gastrectomy patients. In contrast, it is difficult to explain the high stump-cancer incidence with the "N-nitroso compounds" theory-a popular theory for the intact stomach carcinogenesis, and it seemed to be justified to focus chemoprevention of this cancer on the tumor-promoting potential of reflux juice.

Gastric cancer distal to the cardia--prevention or cure?

Adenocarcinoma of the stomach distal to the cardia remains one of the most common cancers in the world. The interest in the aetiology of this disease has been rekindled because of recent epidemiological and molecular studies linking this cancer to H. pylori and certain dietary factors. The authors provide an updated review of the aetiology of gastric cancer. This review seeks to summarize the disease, to propose pathways of carcinogenesis and to suggest ways in which the "traditional" risk factors may be interpreted on the basis of evolving knowledge.

Evidence for dual effect of bile acids on thymidine anabolism and catabolism by the regenerating rat liver

Bile acids have been reported to modify DNA synthesis by rodent livers in regeneration, which may be due in part to their ability to interact with the machinery responsible for deoxyribonucleotide synthesis. The aim of this work was to gain information on the effect of taurocholate (TC) on both anabolic and catabolic pathways accounting for the fate of [methyl-14C]thymidine in the liver of two-third hepatectomized rats. Using high-pressure liquid chromatography, the soluble fraction of liver homogenate was used to measure the ability of TC to modify both the rate of thymidine monophosphate formation from thymidine - i.e., thymidine kinase (TK) activity - and the rate of thymidine release from thymidine, which is the result of at least three different reactions catalyzed by thymidine phosphorylase, nucleosidase and nucleoside deoxyribosyl transferase. TC was found to induce a dose-dependent inhibition of both processes. The nature of this inhibition seems to be in part competitive. Apparent Ki values were 1.5 mM for TK and 4 mM for thymidine release. These inhibitory effects were mimicked by glycocholate but not by taurine. To investigate the relevance of the TC-induced modification of anabolism and catabolism in the whole organ, experiments on regenerating perfused rat livers were carried out. The donors underwent two-third hepatectomy 24 h before liver isolation. They were either fasted during this period (F) or allowed free access to food (NF). DNA synthesis, as measured by [methyl-14C]thymidine incorporation into DNA, was significantly increased in both groups, as compared with control non-hepatectomized animals. However, enhancement in DNA synthesis in group F was only 50% of the value found in the NF group. Intravenous TC administration before and/or during liver perfusions induced a dose-dependent recovery of DNA synthesis in the F group. This effect was accompanied by opposed modifications in the amount of radiolabelled metabolites contained in the non-DNA fraction of liver homogenate, consistent with a marked inhibition of thymidine catabolism. These results suggest that, in addition to the previously reported effects of TC on thymidine anabolism, bile acids are also able to affect the thymidine catabolism. The overall results of this dual effect on the fate of thymidine in the regenerating rat liver depend on the metabolic situation. Under circumstances of no nutrient restriction, the effect of TC is characterized by inhibition of thymidine incorporation into DNA. By contrast, under depressed DNA synthesis due to fasting, the overall effect of TC is a partial recovery of this process.

Alterations in DNA proliferation in gastric stump mucosa with special reference to topography

BACKGROUND

Gastric stump carcinoma occurs more frequently at the anastomotic site than at other areas of the gastric remnant. This study was conducted to determine whether alterations in cell dynamics could be detected in the normal-looking gastric remnant mucosa and to ascertain any difference in cell dynamics between the anastomotic site and other area.

METHODS

Sixty-three patients who underwent curative subtotal gastrectomy for gastric adenocarcinoma were examined 8 to 130 months after operation. Mucosa at the anastomotic site and at the greater curvature were endoscopically biopsied. Cell dynamic changes were examined by flow cytometry, bromodeoxyuridine in vitro labeling, and oncogene (K-ras and c-myc) amplification and translocation by Southern blot analyses.

RESULTS

Inflammatory changes were observed in more than 60% of the cases both at the anastomotic site and at the greater curvature both macroscopically and microscopically. Blood flow, measured by laser Doppler flowmeter, was significantly decreased at the anastomotic site compared with the greater curvature (25.0 +/- 8.1 and 32.2 +/- 9.4 mg/min/100 mg tissue, respectively; p < 0.05). Analysis of DNA histograms obtained by flow cytometry revealed a small peak at the right shoulder of 2N peak in 33% of the specimens obtained from the anastomosis site and in 15% of those from the greater curvature (p < 0.05). The number of cells at S phase measured by bromodeoxyuridine in vitro labeling was also significantly greater at the anastomotic site than at the greater curvature. None of the five patients with aneuploid DNA histograms at the anastomotic site had detectable amplification or translocation of K-ras or c-myc gene in mucosal tissue.

CONCLUSIONS

More marked changes in the mucosal cell dynamics observed at the anastomotic site may partially explain the higher incidence of gastric stump carcinoma at the anastomotic site.

Etiology of gastric remnant cancer with special reference to the effects of denervation of the gastric mucosa

BACKGROUND

Gastric mucosal blood flow, secretion of mucin, and renewal of the gastric mucosal cells are considered to be defensive factors against gastric mucosal injuries. These factors are regulated by the nervous system and neuropeptides. Gastrectomy may affect this regulation and induce gastric mucosal changes, such as atrophic gastritis and carcinoma. The effects of denervation of the gastric mucosa on tumorigenesis of the remnant stomach were investigated.

METHODS

Using male Wistar rats, four groups of Billroth I (B-I)gastrectomy, Billroth II (B-II) gastrectomy, and those with denervation were conducted. Subdiaphragmatic truncal vagotomy was performed in the denervated group. Thirty weeks after the operations, histologic examination and periodic acid-Schiff--Alcian blue (PAS-AB) staining of the gastric mucosa, analysis of cell kinetics of the gastric mucosa by immunohistochemistry of proliferating cell nuclear antigen, and measurement of intragastric pH, intragastric bile acid concentration, and serum gastrin levels were performed. No carcinogenic agents were given.

RESULTS

The B-I group showed no remarkable gastric mucosal changes, but B-I with denervation showed a significant increase in the development of tumor (67%) and carcinoma (42%). In the B-II groups, the denervation induced a significant increase in tumorigenesis, from 22% to 58%. Analysis of cell kinetics revealed a significant increase of labeling index in those groups that developed tumors. PAS-AB staining showed a decrease of PAS positive mucin but an increase of acidic mucin-producing cells in the denervated groups, suggesting an increase in the number of immature cells that are more susceptible to atrophic gastritis and carcinoma. There was no close relationship between tumorigenesis and intragastric pH, intragastric bile acid concentration, or serum gastrin levels.

CONCLUSIONS

After gastrectomy, not only duodenogastric reflux, but also the denervation of the gastric mucosa play an important role in the etiology of gastric remnant cancer.

Gastric cancer risk after vagotomy

The risk of gastric cancer after vagotomy for benign gastric and duodenal disease was examined in a population based cohort of 7198 patients operated on during 1971-79 and followed up until 1988. After exclusion of the first year of follow up there were 34 cases of gastric cancer compared with 25.6 expected (standardised incidence ratio (SIR) = 1.33; 95% confidence intervals (CI) 0.92 to 1.86). Separate analyses by duration of follow up, sex, age at operation, underlying diagnosis, and operative procedures did not show any significant increased or decreased risk of gastric cancer in any of the subgroups. In conclusion, decreased gastric acid secretion after vagotomy does not increase the risk of gastric cancer in the first 10 years after operation or in the subgroup followed up for 10-18 years. A longer follow-up is needed before an excess risk can be excluded.

The aetiology of gastric stump carcinoma in the rat

This study investigated the aetiology of gastric stump carcinoma in the rat. These carcinomas were induced by duodenogastric reflux without the need to administer carcinogens. Carcinoma was only detected when pancreatic exocrine secretions were present in the reflux. Malignant change was associated with dysplasia but not intestinal metaplasia or adenocystic proliferation of glands. The extent of resection increased tumour yield, but a truncal vagotomy did not. No difference was detected in intragastric pH, bacterial flora, or bile acid concentration between animals with and without carcinoma.

Effects of bilateral and unilateral vagotomy on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

After administration of N-methyl-N'-nitro-N-nitrosoguanidine for 15 weeks, the effects of bilateral, anterior and posterior vagotomy on the incidence, number and location of gastric adenocarcinomas, gastric acid secretion and cell proliferation of the gastric mucosa were investigated in inbred Wistar rats. Bilateral or anterior vagotomy, but not posterior vagotomy, significantly increased the incidence and number of adenocarcinomas at experimental week 52. In sham-operated control rats and rats subjected to bilateral vagotomy, there was no significant difference between the incidence or number of gastric tumors in the anterior and posterior walls. After anterior and posterior vagal denervation, however, there were significantly more gastric cancers on the denervated side than on the other. Bilateral and unilateral vagotomy resulted in significantly reduced gastric acid secretion by experimental weeks 25 and 52. Bilateral vagotomy significantly increased the labelling indices of both the fundic and antral mucosa at both times, but did not cause any significant difference between those of the anterior and posterior wall. Anterior or posterior vagotomy resulted in a significant increase in the labelling indices of both the fundic and antral mucosa on the denervated side. These findings indicate that the vagal nerve exerts a trophic action on the gastric mucosa, and that the promoting effect of vagotomy on gastric carcinogenesis may be related to its effect in increasing proliferation of cells in the antral mucosa.

Gastric drainage procedures: effects in normal dogs. II. Clinical observations and gastric emptying

Complete gastric emptying time using barium sulfate mixed with commercial canned dog food was measured radiographically in 29 mature mixed breed dogs before and 3 to 4 weeks after Fredet-Ramstedt pyloromyotomy (FRP) (6 dogs), Heineke-Mikulicz pyloroplasty (HMP) (6 dogs), Finney pyloroplasty (FP) (6 dogs), Jaboulay's gastroduodenostomy (JG) (6 dogs), and antral gastrojejunostomy (AG) (5 dogs). The dogs were observed for clinical evidence of side effects. Postoperative endoscopic examination and double contrast gastrography were performed to subjectively evaluate the diameter of the gastrointestinal communication and the amount of enterogastric reflux. Although none of the procedures significantly (p less than 0.05) altered gastric emptying time, the overall tendency was toward slowing down gastric emptying time. The severity of gastrointestinal side effects and enterogastric reflux appeared to be related to the size and/or location of the gastrointestinal opening.

Comparison of stomach cancer induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine or N-propyl-N'-nitro-N-nitrosoguanidine

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and N-propyl-N'-nitro-N-nitrosoguanidine (PNNG) were administered to male F344 rats at a single dose of 200 mg/kg by gavage and the animals were observed for 110 weeks. The results revealed that PNNG was a weaker carcinogen for the stomach than MNNG under these conditions. After MNNG, the mortality of animals was higher and their average survival time was shorter than after PNNG. Neoplasms were induced in both the forestomach and glandular stomach by both agents. The incidence of forestomach tumors was high: 85% with MNNG, 64% with PNNG, but with PNNG a greater proportion of the forestomach neoplasms were benign. The incidence of neoplasms of the glandular stomach was 18% with PNNG as compared to 65% with MNNG. Intestinal metaplasia appeared in the glandular stomach after exposure to either MNNG or PNNG. There was also a high incidence in untreated control rats. Most glandular stomach neoplasms were composed of both gastric-type and intestinal-type epithelial elements. Only 3 cases of adenocarcinomas were composed solely of intestinal-type cells. These findings suggest that intestinal metaplasia may not necessarily be a preneoplastic stage.

Gastric surgery and the risk of subsequent colorectal cancer

A matched case control study has been conducted in order to determine whether an association exists between gastric surgery and the subsequent development of colorectal carcinoma. Two hundred and eighty-nine patients (151 women and 138 men) presenting with large bowel cancer have been studied. Case controls were matched according to age, sex and date of admission. The case notes of each patient in the study were reviewed to determine the prevalence of peptic ulceration and gastric surgery. Significantly more patients with colorectal carcinoma had undergone gastric surgery P less than 0.05, although the prevalence of peptic ulceration was similar in both groups. Colorectal carcinoma is more common in patients who have undergone gastric surgery for benign peptic ulcer disease than in the general population.

Effect of taurocholic acid feeding on methyl-nitro-N-nitroso-guanidine induced gastric tumors

Bile reflux is generally accepted as a causative factor of gastric cancer after partial gastrectomy. The present study was designed to evaluate the promotion, by the per oral administration of taurocholic acid, of methyl-N-nitro-N'-nitrosoguanidine (MNNG)-induced gastric carcinogenesis. MNNG (83 mg/l) was given in the drinking water to half the male Wistar rats during 12 weeks while the other half served as controls. After this treatment half of the MNNG-treated animals and half of the controls were placed under a diet containing 0.2% of taurocholic acid while the other animals received the standard diet. At the 40th week after initiation of MNNG, surviving animals were killed. Their stomachs and their duodenums were observed for macro and microscopic examination. Macroscopically there were 7 animals bearing gastric tumors in the MNNG group and 15 in the MNNG + bile group (P less than 0.05). Microscopically there were 7 animals with severe antral dysplasia in the MNNG group, 7 rats with fundic dysplasia and 18 with severe antral dysplasia in the MNNG + bile group. Both groups developed an identical number of duodenal tumors which were invasive adenocarcinomas or angiosarcomas. In this experiment taurocholic acid significantly promoted gastric carcinogenesis. It is postulated that surgical techniques inducing duodenal reflux in the stomach may produced a 'high risk' group of patients in which a long and careful follow-up is required.

A morphologic and kinetic basis for the more invasive character of N-methyl-N'-nitro-N-nitrosoguanidine induced duodenal tumors following pyloroplasty

Pyloroplasty increased the invasiveness of duodenal tumors in Wistar rats receiving N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 12 weeks (83 mg/l in drinking water) (Arch. Surg., 117, 768-771). To assess morphologic and kinetic alterations, analyses of tritiated thymidine (3HTdR) pulse-labeled fundic, antral and duodenal mucosa were carried out. The normal appearance of MNNG-treated antral and duodenal mucosa was characterized by the appearance of elongated hyperactive columns exhibiting elevated levels of DNA synthesis. Pyloroplasty in carcinogen-treated rats induced both a 3-fold enhancement in the number of these elongated columns and an elevation in the number of proliferating cells within them (P less than 0.001). In the MNNG and pyloroplasty treated duodenal mucosa 26% of columns contained over 130 cells/column rather than an average of 100 cells in normal appearing MNNG-treated mucosa. DNA synthesis was increased by 23% within these hyperactive glands (11.3 proliferative cells/column vs. 9.4/column in normal appearing mucosa). Pyloroplasty creates both an increase of gastric bile reflux and an increase of the gastric evacuation rate, conditions which influence cell proliferation. Such alterations in antro-pyloro-duodenal physiology contribute to the increased cellular activity observed, promote malignant transformation and foster the expression of invasiveness.