Duodenal and gastric ulcer prevention with misoprostol in arthritis patients taking NSAIDs. Misoprostol Study Group

OBJECTIVES

To determine the efficacy of misoprostol for the prevention of nonsteroidal anti-inflammatory drug (NSAID)-induced duodenal and gastric ulcers in arthritis patients receiving NSAID therapy.

DESIGN

A randomized, double-blind, multicenter, placebo-controlled trial.

SETTING

Six hundred thirty-eight private, Veterans Affairs, health maintenance, and academic practices.

PATIENTS

Six hundred thirty-eight patients with chronic inflammatory or noninflammatory arthritis who were taking an NSAID but who did not have a gastric or duodenal ulcer on screening endoscopy received treatment with ibuprofen, piroxicam, naproxen, sulindac, tolmetin, indomethacin, or diclofenac daily for 3 months. Four hundred fifty-five (71%) patients completed the trial.

INTERVENTIONS

Patients meeting the entry criteria were randomized to receive either misoprostol, 200 micrograms, or placebo, four times a day for 12 weeks.

MAIN OUTCOME MEASURES

The endoscopy was repeated at 4, 8, and 12 weeks. The development of a duodenal or gastric ulcer (defined as a circumscribed mucosal defect > or = 0.5 cm in diameter and with perceptible depth) was regarded as prophylactic failure.

RESULTS

By 12 weeks, a duodenal ulcer developed in 2 of 320 (0.6%; 95% CI, 0.2% to 3.9%) patients randomized to receive misoprostol, compared with 15 of 323 (4.6%; CI, 2.8% to 8%) patients receiving placebo (P = 0.002). A gastric ulcer developed in 6 of 320 (1.9%; (CI, 0.8% to 4.4%) patients, compared with in 25 of 323 (7.7%; CI, 5.1% to 11.4%), respectively.

CONCLUSION

Misoprostol significantly lowers the frequency of both duodenal and gastric ulcer development in patients who require long-term therapy with NSAIDS.

Increased colonic mucosal angiotensin I and II concentrations in Crohn's colitis

To define a potential role for the angiotensin system in Crohn's colitis, the colonic mucosal levels of angiotensin I and II were measured in endoscopic biopsy samples from patients with active Crohn's colitis (n = 20), ulcerative colitis (n = 13), other forms of colitis (n = 3), and normal controls (n = 17). Colonic mucosal levels of angiotensin I and II were greater in patients with Crohn's colitis than in normal subjects (p less than 0.001 and p less than 0.001, respectively). Mucosal levels of angiotensin I and II were also higher in Crohn's colitis than in ulcerative colitis (p less than 0.001 and p less than 0.001, respectively), and levels of angiotensin II were higher in Crohn's than in other forms of colitis (p = 0.014). Mucosal levels of angiotensin I and II correlated well with the degree of macroscopic inflammation in Crohn's colitis (r = 0.86, p less than 0.001 and r = 0.68, p less than 0.001, respectively). Mucosal levels of angiotensin I correlated fairly well with the Crohn's Disease Activity Index (r = 0.46, p less than 0.05) while angiotensin II levels correlated poorly. These studies suggest that angiotensin I and II may have a role in the inflammation associated with Crohn's colitis.

Aging is associated with increased proliferation and decreased apoptosis in the colonic mucosa

Although the incidence of colon cancer increases with advancing age, reasons for this increase are not fully understood. Earlier studies have demonstrated that in Fischer-344 rats, aging is associated with increased crypt cell production in the colon, an event considered to be central to the initiation of carcinogenesis. Apoptosis also plays a critical role in the development and progression of colon cancer. Therefore, we have examined the age-related changes in proliferation and apoptosis in the colonic mucosa of 4-5, 12-14, and 22-24 month-old Fischer-344 rats. We have observed that proliferative activity in the colon, as assessed by proliferating cell nuclear antigen immunoreactivity, is higher (50-80%) in 12-14 and 22-24 month-old rats than in their 4-6 month-old counterparts. In contrast, the number of apoptotic cells, (as determined by TdT-mediated dUTP nick-end labeling assay) in the colonic mucosa of 12-14 and 22-24 month-old rats are considerably lower (50-60%) than in 4-6 month-old animals. These changes are accompanied by a concomitant reduction (75%) in pro-apoptotic Bak and stimulation (200%) of anti-apoptotic Bcl-xL levels. Since activation of caspases is associated with initiation and maintenance of apoptosis, we also analyzed the levels of pro and active forms of caspase-3, 8 and 9. The levels of active forms of caspase-3, 8 and 9 are found to be considerably (60-80%) lower in the colonic mucosa of 22-24 month-old rats, compared to their younger counterparts. This is accompanied by decreased cleavage of poly(ADP-ribose) polymerase, a substrate for caspases. In conclusion, our data show that aging enhances proliferation, but attenuates apoptosis in the colonic mucosa. These changes may partly be responsible for the age-related rise in colorectal cancer.

Folic acid supplementation inhibits recurrence of colorectal adenomas: A randomized chemoprevention trial

AIM: To determine whether folic acid supplementation will reduce the recurrence of colorectal adenomas, the precursors of colorectal cancer, we performed a double-blind placebo-controlled trial in patients with adenomatous polyps.

METHODS: In the current double-blind, placebo-controlled trial at this VA Medical Center, patients with colorectal adenomas were randomly assigned to receive either a daily 5 mg dose of folic acid or a matched identical placebo for 3 years. All polyps were removed at baseline colonoscopy and each patient had a follow up colonoscopy at 3 years. The primary endpoint was a reduction in the number of recurrent adenomas at 3 years.

RESULTS: Of 137 subjects, who were eligible after confirmation of polyp histology and run-in period to conform compliance, 94 completed the study; 49 in folic acid group and 45 in placebo group. Recurrence of adenomas at 3-year was compared between the two groups. The mean number of recurrent polyps at 3-year was 0.36 (SD, 0.69) for folic acid treated patients compared to 0.82 (SD, 1.17) for placebo treated subjects, resulting in a 3-fold increase in polyp recurrence in the placebo group. Patients below 70 years of age and those with left-sided colonic adenomas or advanced adenomas responded better to folic acid supplementation.

CONCLUSION: High dose folic acid supplementation is associated with a significant reduction in the recurrence of colonic adenomas suggesting that folic acid may be an effective chemopreventive agent for colorectal neoplasia.

Effect of aging on the gastrointestinal tract and the pancreas

With estimates that about 14% of the U.S. population will be over 65 years old by the end of this century, scientific research has attempted to achieve a better understanding of the aging process and of diseases that are expressed in higher incidence with advancing age. Because of its high rate of cell turnover and continual renewal, the mucosa of the gastrointestinal (GI) tract appears particularly susceptible to age-related disruptions in the normal cell proliferative process. This may translate into altered function that may result in the induction of malnutrition or malabsorption of particular nutrients, or a greater incidence of GI diseases, such as neoplasia. This review will examine the evidence for age-related alterations in the structural and functional properties of different regions of the GI tract and the pancreas, and how they may relate to malnutrition or disease processes.

Folic acid inhibition of EGFR-mediated proliferation in human colon cancer cell lines

Although accumulating evidence suggests a chemopreventive role for folic acid in colon cancer, the regulation of this process in unknown. We hypothesize that supplemental folic acid exerts its chemopreventive role by inhibiting mucosal hyperproliferation, an event considered to be central to the initiation of carcinogenesis in the gastrointestinal tract. The present investigation examines the effect of supplemental folic acid on proliferation of Caco-2 and HCT-116 colon cancer cell lines. Furthermore, because certain tyrosine kinases, particularly epidermal growth factor receptor (EGFR), play a role in regulating cell proliferation, we also examined the folic acid-induced changes in tyrosine kinase activity and expression of EGFR. In Caco-2 and HCT-116 cells, maintained in RPMI 1640 medium containing 1 microg/ml folic acid, we observed that the supplemental folic acid inhibited proliferation in a dose-dependent manner. Pretreatment of HCT-116 and Caco-2 cell lines with supplemental folic acid (1.25 microg/ml) completely abrogated transforming growth factor-alpha (TGF-alpha)-induced proliferation in both cell lines. Tyrosine kinase activity and the relative concentration of EGFR were markedly diminished in both cell lines following a 24-h exposure to supplemental folic acid. The folic acid-induced inhibition of EGFR tyrosine kinase activity in colon cancer cell lines was also associated with a concomitant reduction in the relative concentration of the 14-kDa membrane-bound precursor form of TGF-alpha. In conclusion, our data suggest that supplemental folic acid is effective in reducing proliferation in two unrelated colon cancer cell lines and that EGFR tyrosine kinase appears to be involved in regulating this process.

Frequency of gastroduodenal lesions in asymptomatic patients on chronic aspirin or nonsteroidal antiinflammatory drug therapy

Endoscopy in 49 patients without upper gastrointestinal symptoms and who were receiving chronic aspirin or nonsteroidal antiinflammatory drug therapy showed the frequency of gastric and duodenal mucosal lesions to be 76 and 27%, respectively. Fifteen (31%) had gastric ulcers, 31 (63%) had gastric erosions, and 10 (20%) had gastric mucosal hemorrhages. Gastric mucosal lesions were noted in 9 (90%) patients taking plain aspirin, in 25 (74%) receiving nonsteroidal antiinflammatory agents, and in 3 (60%) patients taking enteric-coated aspirin. Duodenal lesions were noted in 30 and 26% of patients taking plain aspirin and nonsteroidal antiinflammatory drugs, respectively. Patients taking enteric-coated aspirin had less severe duodenal injury than patients receiving ibuprofen or indomethacin, but the difference was not statistically significant. Endoscopy in 20 normal subjects not taking aspirin or nonsteroidal antiinflammatory drugs showed no gastroduodenal ulcers, erosions, or hemorrhage. Patients chronically taking antiarthritic drugs, including enteric-coated aspirin, have a high frequency of asymptomatic gastroduodenal lesions.

Neutrophil chemotaxis in gastric mucosa. A signal-to-response comparison

This prospective study compares levels of neutrophil chemotactic activity (NCA) in gastric juice to the neutrophil count in gastric biopsies. Sixty-three male patients enrolled in the study and had antral biopsies following collection of gastric juice during esophagogastroduodenoscopy. Biopsies were examined for the magnitude of gastritis, tissue PMN count, and presence of Helicobacter pylori. Secretions were assayed for neutrophil chemotactic activity. Results show an increase in NCA and in tissue PMN counts with increasing severity of gastritis. H. pylori-positive patients had higher levels of NCA and PMN than H. pylori-negative patients. Wide variability in NCA levels preclude a direct correlation between NCA and PMN counts.

Inhibition of gastric mucosal regeneration by tyrphostin: evaluation of the role of epidermal growth factor receptor tyrosine kinase

Although induction of mucosal cell proliferation is a crucial event in gastric mucosal regeneration after injury, intracellular regulatory processes have not been fully elucidated. We hypothesize that tyrosine kinases (Tyr-k)--specifically the enzyme associated with epidermal growth factor receptor (EGF-R)--play an important role in mucosal regeneration. Utilizing tyrphostin--a Tyr-k inhibitor with a greater specificity for EGF-R Tyr-k than for other Tyr-ks--we have examined the role of EGF-R Tyr-k in gastric mucosal regeneration after injury. Gastric mucosal injury in 3-to 4-month-old rats was induced by orogastric administration of 2 mol/L NaCl, whereas the control animals received an equivalent volume of water. The animals were killed 24 hours later. During this 24-hour experimental period (reparative phase), one of the groups was also injected (IP) with tyrphostin-51 (0.65 mg/kg in 30% dimethyl sulfoxide), whereas the control group received the vehicle. In the absence of tyrphostin, the gastric mucosa showed signs of extensive regeneration, whereas in its presence the degree of regeneration was greatly attenuated. These changes were accompanied by parallel alterations in the number of proliferating cell nuclear antigen-immunoreactive cells and the Tyr-k activity of EGF-R. In water-fed control animals, tyrphostin also caused a significant 30% reduction in proliferating cell nuclear antigen-immunoreactive cells. In these animals, the Tyr-k activity of EGF-R was also decreased by 30%. At 24 hours after injury, EGF-R mRNA levels were increased 36-fold over the water-fed controls, and this increase was not significantly affected by tyrphostin. Our current data suggest that activation of EGF-R is an important event in mucosal regeneration.

Increased expression of EGFR in gastric mucosa of aged rats

Although in Fischer-344 rats aging is found to be associated with increased gastric mucosal proliferative activity, little is known about the intracellular events that regulate this process. The present investigation examines the age-related changes in gastric mucosal tyrosine kinase activity and expression of epidermal growth factor receptor(EGFR) and its structural and functional analog p185c-erbB-2, the protein product of c-erbB-2/c-neu protooncogene. We observed a significantly higher intrinsic tyrosine kinase activity and tyrosine phosphorylation of EGFR and p185c-erbB-2 in the gastric mucosa of 24-mo-old (aged) rats than in that of their 4- or 12-mo-old counterparts. This was associated with increased levels of EGFR protein and steady-state mRNA levels of EGFR and p185c-erbB-2. In addition, we also observed threefold higher steady-state mRNA levels of transforming growth factor-alpha (TGF-alpha; one of the primary ligands of EGFR) in the gastric mucosa of aged rats than in that of 4-mo-old (young) animals. This was accompanied by a fivefold increase in the relative concentration of the 18-kDa precursor form of TGF-alpha in gastric mucosal membranes but not in the cytosol. In conclusion, our data demonstrate that aging is associated with increased tyrosine kinase activity of EGFR and p185c-erbB-2 in the gastric mucosa. Moreover, the observation that aging results in increased accumulation of TGF-alpha in gastric mucosal membranes raises the possibility that the membrane-bound TGF-alpha could partly be responsible for the constitutively active EGFR-induced signaling pathway in the gastric mucosa of aged rats and, in turn, for stimulation of mucosal proliferative activity.

Differential responsiveness of proximal and distal colonic mucosa to gastrin

In vivo and in vitro experiments were performed to examine the responsiveness of the proximal and distal colonic mucosa to the growth-promoting action of gastrin. Infusion (osmotic minipump) of gastrin G-17-I (250 ng/kg/h) for 5 days to 4-month-old male Fischer-344 rats resulted in a significant (90-150%) increase in proliferative activity (as assessed by BrdU or PCNA immunoreactivity) in the distal colonic mucosa. In contrast, gastrin caused no apparent change in proliferative activity in the proximal colon. Because tyrosine kinases (Tyr-ks) are thought to be critically involved in regulating the trophic action of gastrin, responsiveness of isolated colonocytes from both segments of the colon to gastrin (1 x 10(-9) M) was also examined. Exposure of isolated colonocytes from the distal, but not from the proximal, colon to gastrin for 2 min resulted in a significant (73%) stimulation in Tyr-k activity. This was also accompanied by a marked rise in phosphorylation of at least six membrane proteins with M, of 55, 60, 70, 94, and 170 kDa. Tyr-k activity induced by gastrin in colonocytes from the distal colon was inhibited by tyrphostin (3.2 microM) but not by staurosporine (20 nM). In colonocytes from the distal colon, gastrin also stimulated phospholipase C (PLC) activity, which could also be inhibited by tyrphostin, but not by staurosporine. We conclude that mucosa of the distal, but not the proximal, colon responds to the trophic action of gastrin. Tyr-ks are thought to be involved in the regulation of this process.

Reassessment of the association between gastrointestinal arteriovenous malformations and aortic stenosis

PURPOSE AND PATIENTS AND METHODS

The purported association between aortic stenosis and gastrointestinal arteriovenous malformations (AVMs) has not been rigorously evaluated. The diagnosis of aortic stenosis in most the prior studies has been based on clinical examination. We therefore utilized two-dimensional and Doppler echocardiography to document the presence or absence of aortic stenosis in 29 men with gastrointestinal AVMs documented by endoscopy.

RESULTS

Of the 29 patients studied, 22 (76 percent) had ejection systolic murmurs and 18 (62 percent) had echocardiographic evidence of aortic sclerosis. However, none of the patients had any evidence of aortic stenosis as assessed by Doppler echocardiography.

CONCLUSION

Although previous case reports and retrospective studies have suggested an association between gastrointestinal AVMs and aortic stenosis, our study does not support this association and suggests the need for a prospective trial.

Folic acid-mediated inhibition of serum-induced activation of EGFR promoter in colon cancer cells

Although accumulating evidence suggests a chemopreventive role for folic acid (FA) in colorectal carcinogenesis, the underlying mechanisms are largely unknown. Previously, we reported that supplemental FA inhibits the expression and activation of epidermal growth factor receptor (EGFR) in colon cancer cell lines. To determine the mechanism(s) by which FA affects EGFR function, we have examined whether and to what extent supplemental FA or its metabolites 5-methyltetrahydrofolate (MTF), dihydrofolate (DF), and tetrahydrofolate (TF) will modulate basal and serum-induced activation of the EGFR promoter in the HCT-116 colon cancer cell line. HCT-116 cells were preincubated with or without (control) FA or one of its metabolites (10 microg/ml) for 48 h, transfected with the EGFR promoter luciferase reporter construct, and incubated for 48 h with FA, DF, TF, or 5-MTF in the absence or presence of 10% FBS. Supplemental FA as well as its metabolites markedly inhibited EGFR promoter activity and its methylation status. Exposure of the cells to 10% FBS caused a marked stimulation of EGFR promoter activity and its expression, both of which were greatly abrogated by supplemental FA and 5-MTF. In contrast, serum-induced activation of c-fos promoter activity was unaffected by 5-MTF. The 5-MTF-induced inhibition of serum-mediated stimulation of EGFR promoter activity and EGFR expression was reversed when methylation was inhibited by 5-aza-2'-deoxycytidine. Our data suggest that FA and its metabolite 5-MTF inhibit EGFR promoter activity in colon cancer cells by enhancing methylation. This could partly be responsible for FA-mediated inhibition of growth-related processes in colorectal neoplasia.

Chemopreventive role of folic acid in colorectal cancer

Mortality from colorectal cancer, a leading cause of death in the U.S.A. and other western countries, has remained unchanged over the past 45 years. Therefore, the search for strategies to prevent the development and progression of colorectal cancer has markedly intensified. Chemoprevention is one such strategy. Accumulating evidence suggests that folic acid, a water soluble vitamin, could be an effective chemopreventive agent for colorectal cancer. Results from several studies have demonstrated that a diet deficient in folic acid may be associated with an increased risk of colonic neoplasia, whereas dietary supplementation of this nutrient may be chemopreventive. Although the mechanisms by which folic acid exerts its chemopreventive role in colorectal carcinogenesis remain to be fully elucidated, supplemental folic acid has been shown to arrest the loss of heterozygosity (LOH) of the tumor suppressor gene DCC (deleted in colorectal cancer) and to stabilize its protein in normal appearing rectal mucosa of patients with colorectal adenomas. Data from in vitro studies utilizing colon cancer cell lines suggest that supplemental folic acid or its metabolite 5-methyltetrahydrofolate (5-MTF) attenuates the expression and activation of EGF-receptor (EGFR) as well as proliferation of cells. The folic acid mediated reduction of EGFR function could partly be the result of suppression of EGFR gene through increased methylation of CpG sequences within its promoter.

Folic acid mediated attenuation of loss of heterozygosity of DCC tumor suppressor gene in the colonic mucosa of patients with colorectal adenomas

Loss of heterozygosity (LOH) and/or inactivation of tumor suppressor genes are implicated in the initiation and progression of many malignancies, including colorectal cancer. Although accumulating evidence suggests a chemopreventive role for folate in colorectal cancer, regulatory mechanisms are poorly understood. The primary objective of the current investigation was to determine whether folic acid would prevent LOH of the three tumor suppressor genes, deleted in colorectal cancer (DCC), adenomatous polyposis coli (APC) and p53 in macroscopically normal appearing rectal mucosa of patients with adenomatous polyps. In addition, the effect of folic acid on rectal mucosal proliferation was determined. Twenty patients were randomized in a double-blind study to receive either folic acid 5mg once daily or identical placebo tablets for 1 year. Genomic DNA and total protein were extracted from the rectal mucosa at baseline and after 1 year of treatment and analyzed for LOH and protein levels of APC, DCC and p53 genes. In addition, paraffin-embedded mucosal specimens were analyzed for proliferating cell nuclear antigen (PCNA) immunoreactivity, as a measure of cellular proliferative activity. Folate supplementation prevented LOH of DCC gene in five out of five (100%) patients who demonstrated baseline heterozygosity, whereas two out of four (50%) placebo-treated patients with baseline heterozygosity demonstrated allelic loss. Mucosal protein levels of DCC were also reduced in 7 of 10 (70%) placebo-treated patients compared to only 2 of 10 (20%) of patients treated with folate. Levels increased, however, in eight and three patients in the folic acid and placebo groups, respectively (P<0.02). Folic acid caused no change in allelic status of either APC or p53 gene. Folate supplementation caused a small, but not statistically significant, 16% reduction in mucosal proliferation, whereas placebo treatment resulted in a 88% (P<0.05) increase in this parameter, when compared with the corresponding baseline values. Our results indicate that folic acid prevents an increase in proliferation and arrests LOH of DCC gene and also stabilizes its protein in normal appearing rectal mucosa of patients with colorectal adenomas. Taken together, our data suggest that one of the ways folate may exert its chemopreventive effect is by stabilizing certain tumor suppressor gene(s) and preventing further increases in proliferation.

Treatment of nonsteroidal antiinflammatory drug-induced gastric ulcers with misoprostol. A double-blind multicenter study

One hundred sixty-two patients chronically ingesting ibuprofen, piroxicam, or naproxen for osteoarthritis, who had abdominal pain and an endoscopically proven gastric ulcer were evaluated for eight weeks in a randomized, double-blind trial comparing misoprostol (200 micrograms four times daily with meals and at bedtime) (N = 77) with placebo (N = 85). Patients discontinued their usual daily dose of antiarthritic medication throughout the study period, and an endoscopy was performed at four weeks and eight weeks (if necessary) to assess ulcer healing. Gastric ulcers were defined as circumscribed breaks in the gastric mucosa of 0.3 cm in diameter or greater. Misoprostol therapy significantly accelerated the rate of gastric ulcer healing compared to placebo (P = 0.033). The cumulative percent healed after four and eight weeks of therapy for misoprostol versus placebo were: 83% vs 61% at four weeks and 96% vs 90% at eight weeks (P = 0.0028 and P = 0.0977, respectively by lifetable analysis). Relief of abdominal pain did not differ significantly between the treatment groups. Misoprostol significantly accelerates the healing of ibuprofen-, piroxicam-, or naproxen-induced gastric ulcers.

Persistence of gastric ulcers caused by plain aspirin or nonsteroidal antiinflammatory agents in patients treated with a combination of cimetidine, antacids, and enteric-coated aspirin

Twenty-three patients chronically ingesting plain aspirin or nonsteroidal antiinflammatory drugs, who had endoscopically proven solitary or multiple gastric ulcers, were treated for eight weeks with cimetidine and antacids. Plain aspirin and nonsteroidal antiinflammatory drugs were discontinued in all patients. Seven patients received enteric-coated aspirin throughout the treatment phase and continuously for the entire study period (2.5-12 months). The remainder of patients (N = 16) did not receive enteric-coated aspirin. An endoscopy was performed to assess ulcer healing. None of seven patients receiving enteric-coated aspirin had complete healing of their ulcer(s) while 15 of 16 patients not receiving enteric-coated aspirin demonstrated complete healing of their ulcer(s) (P less than 0.001). An eight-week course of cimetidine and antacids is ineffective in completely healing gastric ulcers caused by plain aspirin or nonsteroidal antiinflammatory drugs while enteric-coated aspirin is continued.

Aging enhances G(1) phase in the colonic mucosa of rats

Although in Fischer-344 rats, aging has been shown to be associated with increased crypt cell production in the colonic mucosa, no information is available about the responsible intracellular mechanisms for the age-related rise in colonic mucosal cell proliferation. To determine whether cell cycling events are affected by aging, the present investigation examines the age-related changes in Cdk2 activity and the regulation of this process in the colonic mucosa. Colonic mucosae from 4-, 13- and 24-month-old Fischer-344 rats were assayed for Cdk2 activity and protein expression of Cdk2, cyclin D1 and E, as well as p21(Waf1/Cip1) (total and the fraction bound to Cdk2), p53 and phosphorylated Rb. Kinase activity and protein levels of Cdk2, as well as cyclin D1 concentration in the colonic mucosa, rose steadily with advancing age. However, the levels of cyclin E in the colonic mucosa were found to be higher in 24-month-old than 13-month-old rats, compared to their 4-month-old counterparts. On the other hand, levels of mucosal p21(Waf1/Cip1) (total and the fraction bound to Cdk2), one of the universal inhibitors of Cdks, were found to be lower in aged than in young rats. This was accompanied by a parallel decrease in mucosal p53, a tumor suppressor protein that is known to regulate p21(Waf1/Cip1). Additionally, we observed that the levels of phosphorylated Rb protein, a form which is involved in regulating progression of cells through the S phase, are increased in the colonic mucosa of 24-month-old rats, but not in 13-month-old animals, when compared with their 4-month-old counterparts. Our data suggest that, G(1) to S phase transition, as well as progression through the S phase of the cell cycle are accelerated in the colonic mucosa of aged rats.

Age-associated loss of heterozygosity of tumor suppressor genes in the gastric mucosa of humans

The current study is based on the hypothesis that aging predisposes gastric mucosa to carcinogenesis through altered expression and/or mutations of genes involved in cell growth. To test this hypothesis, we investigated the age-associated changes in mutation of adenomatous polyposis coli (APC), deleted in colorectal cancer (DCC), p53, and K-ras genes in the gastric mucosa of 19 healthy subjects of varying ages (25-91 yr). Specifically, we studied the loss of heterozygosity (LOH) of these genes in cardia, body, and antrum of the stomach. We observed that 3 of 19 subjects (16%) over 60 yr of age show LOH of at least one of the tumor suppressor genes. Among the subjects over 60 yr of age, the incidence of LOH is 38% (3/8). Two of three subjects had mutations in more than one tumor suppressor gene. In all three affected subjects, mutation in APC, DCC, or p53 was located mainly in the body of the stomach, suggesting increased susceptibility of this region to neoplastic changes. However, no LOH of K-ras was observed in these subjects. Our observation that subjects over 60 yr of age show mutation in one or more of the tumor suppressor genes suggests an age-related increase in predisposition of the stomach to neoplasia.

Efficacy of screening flexible sigmoidoscopy for colorectal neoplasia in asymptomatic subjects

PURPOSE

Although flexible sigmoidoscopy is recommended in patients over age 40 to complement fecal occult blood screening for colorectal neoplasia, the yield of this procedure in asymptomatic, average-risk subjects has varied between studies. In addition, the efficacy of flexible sigmoidoscopy in detecting early curable carcinoma has been the subject of debate. We therefore undertook this study to assess the efficacy, safety, and cost of the procedure for early detection of colorectal neoplasia in asymptomatic subjects.

PATIENTS AND METHODS

Flexible sigmoidoscopy with a 60-cm scope was performed in 412 asymptomatic veterans (mean age, 63.2 years). Subjects with positive fecal occult blood and those at increased risk for colorectal neoplasia were excluded. Costs were estimated on the basis of Medicare payments.

RESULTS

A mean length of 56.1 cm of sigmoid and descending colon was examined. A total of 132 polyps were detected in 93 subjects (22.6%). Thirty-five percent of the polyps were located at a distance of greater than 30 cm from the anal verge. Of 122 polyps removed, 26% were 1 cm in size or larger. A total of 77 polyps (63%) were adenomas, and six polyps (5%) were carcinomas. Of the six carcinomas detected (two carcinoma in situ, one Astler Coller stage A, two stage B1, and one stage C1), five were in a localized stage and thus potentially curable. The cost of detecting each potentially curable carcinoma was $47,174. No complications from flexible sigmoidoscopy were noted.

CONCLUSION

In conclusion, 60-cm flexible sigmoidoscopy is a safe, high-yield procedure for the initial screening of colorectal neoplasia in asymptomatic, average-risk subjects over the age of 50. Because the carcinomas detected were still in an early stage, such screening may improve survival.

Aging and cancer of the stomach and colon

Although the incidence of most human malignancies including cancer of the gastrointestinal tract increases dramatically with advancing age, the precise role of aging in that increase remains a matter of continued controversy. Many probable explanations for the age-related rise in cancer incidence have been offered including altered carcinogen metabolism and the cumulative effects of protracted exposure to cancer-causing agents. Neoplasia of the stomach or colon is a multi-stage process with hyperproliferation being central to the initiation of carcinogenesis. Since aging is associated with increased gastrointestinal mucosal cell proliferation, the possibility that aging itself may render target cells more susceptible to carcinogenic transformation continues to be an area of intense interest and study. This review will examine the evidence for age-related alterations in the structural and functional properties of the gastric and colonic mucosa in an effort to further elucidate the potential mechanisms of carcinogenesis which may be involved during the aging process.

Folic acid reduces nuclear translocation of beta-catenin in rectal mucosal crypts of patients with colorectal adenomas

We have demonstrated that folic acid inhibits cell proliferation and epidermal growth factor receptor (EGFR) activation in colon cancer cell lines. We examined the effect of one year supplemental folic acid (5 mg/day) on the rectal mucosal expression of beta-catenin and pGSK3beta, known to be affected by EGF-R, in patients with colorectal adenomas. Folic acid treatment significantly reduced nuclear expression of beta-catenin (P < 0.05) and cellular expression of pGSK3beta (P < 0.01) when compared to placebo. Folic acid may exert its chemopreventive effect, at least in part, through inhibition of nuclear translocation of beta-catenin.

Aging alters gastric mucosal responses to epidermal growth factor and transforming growth factor-alpha

Administration of pharmacological doses of epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) in young rats stimulates gastric mucosal proliferation, but, in aged rats, the same treatment inhibits proliferation. This may be due to enhanced ligand-induced internalization of EGF receptor (EGFR). In support of this, we demonstrated that although a single injection of EGF (10 microg/kg) or TGF-alpha (5 microg/kg) in young (4-6 mo old) rats greatly increased membrane-associated EGFR tyrosine kinase activity, the same treatment slightly inhibited the enzyme activity in aged (24 mo old) rats. This treatment also produced a greater abundance of punctate cytoplasmic EGFR staining in gastric epithelium of aged rats, consistent with EGFR internalization. In vitro analyses demonstrated that exposure of isolated gastric mucosal cells from aged but not young rats to 100 pM TGF-alpha resulted in marked increases in intracellular EGFR tyrosine kinase activity and that induction of EGFR tyrosine kinase activity in mucosal membranes from aged rats occurred at doses 1,000-fold less than those required in young rats. Our data suggest that aging enhances sensitivity of the gastric mucosa to EGFR ligands. This may partly explain EGFR-mediated inhibition of gastric mucosal proliferation in aged rats.

A report of three multiclinic trials evaluating arbaprostil in arthritic patients with ASA/NSAID gastric mucosal damage. The Upjohn Company Arbaprostil ASA/NSAID Gastric Mucosal Damage Treatment Study Groups

Three randomized, placebo-controlled multiclinic trials involving arbaprostil dosages of (a) 10 micrograms; (b) 25 micrograms; and (c) 10, 25, or 50 micrograms orally for 4 wk in patients older than 18 yr with rheumatoid arthritis or osteoarthritis who had endoscopically documented nonsteroidal antiinflammatory drug-associated gastric mucosal damage were conducted in the United States. All patients continued taking the nonsteroidal antiinflammatory drugs and were reendoscoped after 4 wk of therapy. Success at that time was defined as complete resolution of all gastric mucosal damage. Six hundred fifty-eight patients were enrolled in the three trials. Significantly more patients experienced healing in the arbaprostil treatment groups in all trials compared with those who received placebo. The healing rates in the various trials were 68% and 32% (10 micrograms vs. placebo; p = 0.007); 77% and 23% (25 micrograms vs. placebo; p less than 0.001); and 52%, 46%, 35%, and 16% (50, 25, and 10 micrograms vs. placebo; p less than 0.001, less than 0.001, and 0.002, respectively). Diarrhea, mostly of a mild nature, was the only arbaprostil-associated side effect and was found with the 25- and 50-microgram dosages (33% and 59%, respectively). No exacerbation of arthritis signs or symptoms was found. Arbaprostil at doses with varying effects on gastric acid secretion (25 and 50 micrograms) was documented in these trials to be an effective and safe agent for healing gastric mucosal damage associated with aspirin or other nonsteroidal antiinflammatory drugs in patients with either rheumatoid arthritis or osteoarthritis without adversely affecting joint symptomatology.