Cox-2 is needed but not sufficient for apoptosis induced by Cox-2 selective inhibitors in colon cancer cells

The role of Cox-2 in NSAID-induced apoptosis is debated. We studied the role of Cox-2 inhibition in apoptosis induced by a selective Cox-2 inhibitor, SC236 (a structural analogue of celecoxib) in two colon cancer cell lines, HT29 (expressing Cox-2 protein) and HCT116 (not expressing Cox-2 protein). Apoptosis was quantified by flow cytometry. SC236 0-75 microM decreased cell numbers and induced apoptosis to identical levels in HT29 and HCT116 cells. However, SC236, concentrations >75 microM reduced Cox-2 protein expression in HT29 cells and induced greater levels of apoptosis in HT29 than in HCT116 cells. In contrast, sulindac sulfide (SSD) (which inhibits Cox-1 and Cox-2) 0-200 microM or sulindac sulfone (SSN) 0-500 microM (without significant activity against Cox-1 or Cox-2) caused identical decreases in cell number and increases in apoptosis in HT29 and HCT116 cells. Neither SSD nor SSN altered the expression of Cox-2 in HT29 cells. To determine that the higher levels of apoptosis in HT29 cells with SC236 >75 microM were related to decreased Cox-2 protein levels, we decreased Cox-2 protein expression in HT29 cells with curcumin (diferuloylmethane) and studied its effect on SC236-induced apoptosis. Curcumin augmented apoptosis induced by SC236 in HT29 cells but not in Cox-2 lacking HCT116 cells. In conclusion, selective Cox-2 inhibitors can induce apoptosis independent of Cox-2 expression. However they may selectively target cells that express Cox-2 by decreasing their Cox-2 protein expression.

Comparison of calcium supplementation or low-fat dairy foods on epithelial cell proliferation and differentiation

Epidemiological evidence suggests that dietary calcium and vitamin D intake are inversely related to incidence of colon cancer. Previous studies have demonstrated that supplementation of the diet with calcium in the form of calcium tablets or low-fat dairy foods alters colonic epithelial cell proliferation from a higher- to a lower-risk pattern. The present study compared relative effects of administration of calcium carbonate at approximately 900 mg/day (calcium) with those of a low-fat dairy food diet providing about the same amount of calcium (dairy) in a cross-over "head-to-head" study of 40 subjects at risk for colonic neoplasia. Dietary intake of macronutrients was similar in the two study periods, except for a slight increase in protein intake during dairy calcium supplementation. Rectal epithelial cell proliferation was studied in flat endoscopically normal-appearing mucosa at baseline and at the end of each of the two study periods and showed a significant reduction in epithelial crypt cell labeling index from 12.5% to 9.1% (calcium) or 9.3% (dairy) as well as in proliferating cells in the upper 40% of the crypt from 0.09 to 0.03 in the calcium- and low-fat dairy-supplemented intervention groups. No significant changes in two epithelial cell differentiation markers, cytokeratin AE1 and acidic mucins, were found. Furthermore, there were no differences in epithelial cell apoptosis or expression of the proapoptotic gene product BAK. These data indicate that increased dietary calcium given as supplements or in the diet in low-fat dairy foods lowers epithelial cell proliferation indexes from a higher- to a lower-risk pattern. Because supplemental calcium has been shown to reduce the recurrence of colonic adenomatous polyps in patients at increased risk for colonic neoplasia, our data suggest that supplemental low-fat dairy foods may also be effective.

p21(WAF1/cip1) is an important determinant of intestinal cell response to sulindac in vitro and in vivo

Sulindac, a nonsteroidal anti-inflammatory drug, inhibits intestinal tumorigenesis in humans and rodents. Sulindac induced complex alterations in gene expression, but only 0.1% of 8063 sequences assayed were altered similarly by the drug in rectal biopsies of patients treated for 1 month and during response of colonic cells in culture. Among these changes was induction of the cyclin-dependent kinase inhibitor, p21(WAF1/cip1). In Apc1638(+/-) mice, targeted inactivation of p21 increased intestinal tumor formation in a gene-dose-dependent manner, but inactivation of p21 completely eliminated the ability of sulindac to both inhibit mitotic activity in the duodenal mucosa and to inhibit Apc-initiated tumor formation. Thus, p21 is essential for tumor inhibition by this drug. The array data can be accessed on the Internet at http://sequence.aecom.yu.edu/genome/.

Diarrhea and malabsorption in the elderly

Physicians who care for elderly patients should be alert to the possible presence of diarrhea and malabsorption. Older patients may not admit to having chronic diarrhea, particularly if they also are incontinent. If diarrhea is of short duration, an infectious cause is at least as common as in the young. Institutionalized elderly are particularly prone to gastrointestinal infections, but the manifestations may not be overt. When an intestinal infection and potential medication-induced gastrointestinal disturbances have been excluded, the differential diagnosis of diarrhea in the elderly is the same as in the young. Causes include intestinal malabsorption, even though diarrhea is a less common manifestation of malabsorption in the old than in younger patients. In the elderly, micronutrient deficiency is a common presenting clinical picture; because the symptoms of malabsorption are covert, the diagnosis often is delayed, and nutritional deficiencies are more common and more severe than in the young. Because the elderly have less nutritional reserve than the young, these deficiencies are clinically much more devastating in the elderly. Although the causes of malabsorption, as a whole, are similar in older and younger patients, chronic pancreatic insufficiency of unknown cause and intestinal bacterial overgrowth without an anatomic abnormality of the small intestine are syndromes that are specific to the elderly and must be considered in any older patient with unexplained weight loss or failure to thrive. Often, therapeutic trials are necessary to establish a potential diagnosis.

25-hydroxyvitamin D-1alpha-hydroxylase in normal and malignant colon tissue

Vitamin D affects calcium metabolism and prevents proliferation of colon cells in vitro. In human beings the main circulating form of vitamin D is 25-hydroxyvitamin D; to regulate calcium homoeostasis, this form must be converted to 1alpha, 25-dihydroxyvitamin D by 1alpha-hydroxylation in the kidney with 25-hydroxyvitamin D-1alpha-hydroxylase. Cultured transformed colon cancer cells can convert 25-hydroxyvitamin D(3) to 1alpha,25-dihydroxyvitamin D(3). We identified messenger RNA (mRNA) for 25-hydroxyvitamin D-1alpha-hydroxylase in normal colon tissue and in malignant and adjacent normal colon tissue. These findings support the notion that vitamin D might have a role in cell growth regulation and cancer protection, and might be the explanation for why the risk of dying from colorectal cancer is highest in areas with the least amount of sunlight.

Gastrin-mediated alterations in gastric epithelial apoptosis and proliferation in a mastomys rodent model of gastric neoplasia

BACKGROUND/AIMS

Hypergastrinemia secondary to low acid secretion is associated with gastric carcinoid formation in Mastomys. We investigated the effect of gastrin on oxyntic epithelial apoptosis and proliferation in this model.

METHODS

Hypergastrinemia and mucosal hyperplasia were induced by irreversible H(2) receptor blockade with loxtidine. Gastrin levels were normalised in some animals by 10 days' loxtidine withdrawal. Serum gastrin was determined by radioimmunoassay, proliferative, enterochromaffin-like cells and Bcl-2 protein family expression by immunohistochemistry, and apoptotic cells by terminal deoxyuridine nucleotide nick end labeling (TUNEL).

RESULTS

Proliferating cells were increased 4-fold in loxtidine-treated animals, and returned to normal upon loxtidine withdrawal. Enterochromaffin-like cell number increased 2-fold with loxtidine, and did not decrease after withdrawal. Apoptotic epithelial cells were located at the luminal surface and increased 1.8-fold with loxtidine, returning to control levels upon withdrawal. The ratio of proliferative to apoptotic cells was lower in the control and withdrawn groups than in the loxtidine group (0.26+/-0.05 and 0.26+/-0.08 vs. 0.77+/-0.12). With hypergastrinemia, the expression of Bcl-2 and Bak was increased and Bax decreased in the middle of the gland.

CONCLUSION

Hypergastrinemia is associated with alterations in both proliferation and apoptosis in Mastomys gastric mucosa. This may contribute to the pathogenesis of mucosal hyperplasia in this model.

Increased gastric epithelial cell apoptosis associated with colonization with cagA + Helicobacter pylori strains

Gastric colonization by Helicobacter pylori is a risk factor for noncardia gastric cancer. The association between H. pylori and cancer may be attributable to increased epithelial cell turnover, possibly related to antigastric antibodies. Two previous studies reported a disproportionate increase in proliferation relative to apoptosis in patients with H. pylori strains expressing the virulence-related cagA gene. This has led to the hypothesis that an abrogation of apoptosis by cagA-positive strains may promote neoplasia. We, therefore, examined the effect of H. pylori on gastric epithelial proliferation, apoptosis, and the presence of serum antiparietal cell antibodies in a large prospective study. Proliferation and apoptosis were evaluated "blindly" using validated immunohistochemical methods in two antral and two gastric corpus biopsies from 60 patients with nonulcer dyspepsia, and results were correlated with the presence of serum antiparietal cell antibodies. H. pylori colonization was assessed by histology, biopsy urease test, and serology. Proliferation was increased 2-fold in both antrum and corpus in H. pylori-positive patients, was not related to H. pylori cagA status, and was positively correlated with histological gastritis. Apoptosis was increased in the antrum and body only in patients with cagA-positive H. pylori strains. Antiparietal cell antibodies were not more prevalent in H. pylori colonization, and their presence was inversely related to epithelial apoptosis scores we therefore conclude that in patients with nonulcer dyspepsia, H. pylori carriage is associated with increased proliferation. Futhermore the cag pathogenicity island is associated with increased apoptosis. Our results do not support the hypothesis that there is a relative deficiency of gastric epithelial cell apoptosis associated with the carriage of cagA-positive strains. Host factors may be more important than bacterial products in determining the long-term outcome of H. pylori colonization.

Antiproliferative effects of S-allylmercaptocysteine on colon cancer cells when tested alone or in combination with sulindac sulfide

Epidemiological studies link increased garlic (Allium sativum) consumption with a reduced incidence of colon cancer in various human populations. Experimental carcinogenesis studies in animal models and in cell culture systems indicate that several allium-derived compounds exhibit inhibitory effects and that the underlying mechanisms may involve both the initiation and promotion phases of carcinogenesis. To provide a better understanding of the effects of allium derivatives on the prevention of colon cancer, we examined two water-soluble derivatives of garlic, S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC), for their effects on proliferation and cell cycle progression in two human colon cancer cell lines, SW-480 and HT-29. For comparison, we included the compound sulindac sulfide (SS), because sulindac compounds are well-established colon cancer chemopreventive agents. We found that SAMC, but not SAC, inhibited the growth of both cell lines at doses similar to that of SS. SAMC also induced apoptosis, and this was associated with an increase in caspase3-like activity. These affects of SAMC were accompanied by induction of jun kinase activity and a marked increase in endogenous levels of reduced glutathione. Although SS caused inhibition of cell cycle progression from G1 to S, SAMC inhibited progression at G2-M, and a fraction of the SW-480 and HT-29 cells were specifically arrested in mitosis. Coadministration of SS with SAMC enhanced the growth inhibitory and apoptotic effects of SS. These findings suggest that SAMC may be useful in colon cancer prevention when used alone or in combination with SS or other chemopreventive agents.

Peptic disease in elderly patients

The increase in life expectancy demands that more attention be given to gastrointestinal problems, such as peptic ulcer disease, in elderly people. This review summarizes many of the physiological changes that have a role in peptic ulcer disease in elderly patients. How Helicobacter pylori infection modifies the course of peptic disease is also reviewed. The clinical presentation of peptic diseases often differs in elderly people, and atypical symptoms are common. Accurate diagnosis requires aggressive endoscopic evaluation. Treatment regimens using H2 receptor antagonists, proton pump inhibitors and regimens to eradicate H pylori may also need to be altered in elderly patients.

Studies of calcium in food supplements in humans

Colon cancer is one of the commonest cancers in the Western world. Environmental factors appear to predominate as exemplified by a change in incidence in colon cancer within 20 years when people emigrate from a low- to a high-incidence country. It had been suggested that a diet high in energy, fat, and meat content and low in fiber content is most likely responsible. Epidemiologic observations have pointed to a potential effect of calcium or/and vitamin D in reducing the incidence of colon cancer. Other studies have shown a reduction in preneoplastic colon adenomas with increased calcium or/and vitamin D intake. High fat diets were shown to be accompanied by an increase in fecal fatty acids and bile acids or a change in bile acid composition. Soluble fatty acids and bile acids then could interact with the colonic epithelium inducing cell damage and increased proliferation. A hypothesis was developed suggesting that calcium supplementation and increased calcium in the colonic lumen would precipitate these bile acids and fatty acids. Examination of the effect of supplemental calcium or calcium in dairy foods showed a major reduction in fecal bile acids and fatty acids in solution in volunteers and accompanied by a reduction in cytolytic activity. Studies then were performed in patients at risk for colon cancer seeking a change in proliferative biomarkers of risk from a high-risk to a low-risk pattern with supplemental calcium administration. These studies generally have shown a beneficial effect of the addition of calcium at 1.2-2 gm per day in addition to a regular diet for periods of 2 to 6 months. A recently published study also demonstrated that a diet, in which low-fat dairy foods containing an average of about 825 mg of calcium, significantly improved proliferative biomarkers as well as two differentiation bio-markers of risk for colon cancer from a high- to a low-risk pattern. These observations, together with recent studies showing reduced adenomatous polyp recurrence when supplemental calcium was provided, demonstrate the potential of calcium and perhaps vitamin D as chemopreventive agents for colorectal neoplasia.

Ziprasidone and the pharmacokinetics of a combined oral contraceptive

AIMS

To determine whether multiple doses of ziprasidone alter the steady-state pharmacokinetics of the component steroids, ethinyloestradiol and levonorgestrel, of an oral contraceptive; to evaluate the tolerability of a co-administered combined oral contraceptive and ziprasidone; and to compare plasma concentrations of prolactin in subjects taking a combined oral contraceptive with placebo or ziprasidone.

METHODS

Nineteen women taking a combined oral contraceptive (ethinyloestradiol 30 microg day(-1) and levonorgestrel 150 microg day(-1)) were enrolled into a double-blind, placebo-controlled, two-way crossover study. They received ziprasidone 40 mg day- 1 in two divided daily doses or placebo for 8 days (days 8-15) in one of two 21 day treatment periods separated by a 7 day washout period. Venous blood samples were collected immediately before and up to 24 h after the morning dose of oral contraceptive and ziprasidone or placebo on day 15 of each 21 day treatment period. These were assayed for ethinyloestradiol and levonorgestrel and the resulting data used to derive pharmacokinetic data for these steroids. Additional samples were collected immediately before and 4 h after the morning dose of oral contraceptive and ziprasidone or placebo on day 15 of each 21 day treatment period for prolactin assay. All observed and volunteered adverse events were recorded throughout the study.

RESULTS

The mean AUC(0,24 h), Cmax and tmax for ethinyloestradiol and the mean AUC(0, 24 h) and Cmax for levonorgestrel during ziprasidone co-administration were not statistically significantly different from corresponding values occurring during placebo co-administration. The tmax for levonorgestrel was approximately 0.5 h longer. Concomitant therapy with a combined oral contraceptive and ziprasidone did not result in adverse events not previously seen with either preparation alone.

CONCLUSIONS

The findings of this study suggest that, based on pharmacokinetic and tolerability data, ziprasidone may be co-administered with ethinyloestradiol and levonorgestrel without loss of contraceptive efficacy or increased risk of adverse events.

Abnormalities in the expression of cell cycle-related proteins in tumors of the small bowel

Tumors of the small bowel are quite rare for unknown reasons, although they resemble colorectal tumors in many respects. The purpose of this study was to determine whether abnormalities in the expression of several cell cycle control genes are of importance in small bowel tumorigenesis by comparing a series of samples of normal mucosa, adenomatous polyps, and adenocarcinomas. The levels of cyclin D1, cyclin E, p16, p21, p27, and p53 proteins were determined by immunohistochemistry in samples of normal small bowel (n = 16), small bowel adenomas (n = 20), and small bowel adenocarcinomas (n = 24). Normal small bowel mucosa expressed p27 protein, but not the other cell cycle-related proteins. About 20% of the tumors displayed a decrease in the expression of this protein. The most frequent alteration in the tumors was an increase in the p16 protein. Increased expression of p53 was associated with tumor progression because it was overexpressed in 45% of the adenomas and 65% of the adenocarcinomas (P<0.05). Advanced age and increased detection of cyclin D1 and p53 were associated with a decreased 3-year survival (P<0.05). Cell cycle abnormalities are early and important events in the multistep process of small bowel tumorigenesis, thus resembling colorectal carcinogenesis. As in colon cancer, deregulated expression of G1 proteins may perturb cell cycle control in benign adenomas of the small bowel and thereby enhance tumor progression. Increased expression of cell cycle inhibitors in tumors may serve as a defense mechanism for tumor progression.

Decreased and aberrant nuclear lamin expression in gastrointestinal tract neoplasms

BACKGROUND

Altered expression of lamins A/C and B1, constituent proteins of the nuclear lamina, may occur during differentiation and has also been reported in primary lung cancer.

AIMS

To examine the expression of these proteins in gastrointestinal neoplasms.

PATIENTS

Archival human paraffin wax blocks and frozen tissue from patients undergoing surgical resection or endoscopic biopsy.

METHODS

Immunohistochemistry and western blotting using polyclonal antisera against A type lamins and lamin B1.

RESULTS

The expression of lamin A/C was reduced and was frequently undetectable by immunohistochemistry in all primary colon carcinomas and adenomas, and in 7/8 primary gastric cancers. Lamin B1 expression was reduced in all colon cancers, 16/18 colonic adenomas, and 6/8 gastric cancers. Aberrant, cytoplasmic labelling with both antibodies occurred in some colonic cancers and around one third of colonic adenomas. Cytoplasmic lamin A/C expression was detected in 3/8 gastric cancers. Lamin expression was reduced in gastric dysplasia, but not intestinal metaplasia, atrophy, or chronic gastritis. Lamin expression was low in carcinomas of oesophagus, prostate, breast, and uterus, but not pancreas.

CONCLUSIONS

Reduced expression of nuclear lamins, sometimes together with aberrant, cytoplasmic immunoreactivity is common in gastrointestinal neoplasms. Altered lamin expression may be a biomarker of malignancy in the gastrointestinal tract.

Lovastatin augments sulindac-induced apoptosis in colon cancer cells and potentiates chemopreventive effects of sulindac

BACKGROUND & AIMS

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (HRIs) were found incidentally to reduce new cases of colon cancer in 2 large clinical trials evaluating coronary events, although most patients in both treatment and control group were taking nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs are associated with reduced colon cancer incidence, predominantly by increasing apoptosis. We showed previously that lovastatin induces apoptosis in colon cancer cells. In the present study we evaluated the potential of combining lovastatin with sulindac for colon cancer chemoprevention.

RESULTS

Lovastatin, 10-30 micromol/L, augmented sulindac-induced apoptosis up to 5-fold in 3 colon cancer cell lines. This was prevented by mevalonate (100 micromol/L) or geranylgeranylpyrophosphate (10 micromol/L) but not farnesylpyrophosphate (100 micromol/L), suggesting inhibition of geranylgeranylation of target protein(s) as the predominant mechanism. In an azoxymethane rat model of chemical-induced carcinogenesis, the total number of colonic aberrant crypt foci per animal (control, 161 +/- 11) and the number of foci with 4+ crypts (control, 40 +/- 4.5) decreased to 142 +/- 14 (NS) and 43 +/- 2.9 (NS), respectively, with 50 ppm lovastatin alone; to 137 +/- 5.4 (P = 0.053) and 36 +/- 2.1 (NS) with 80 ppm sulindac alone; and to 116 +/- 8.1 (P = 0.004) and 28 +/- 3.4 (P = 0.02) when 50 ppm lovastatin and 80 ppm sulindac were combined.

CONCLUSIONS

Addition of an HRI such as lovastatin may augment chemopreventive effects of NSAIDs or/and may allow lower, less toxic doses of these drugs to be used.

Dairy foods and prevention of colon cancer: human studies

Colon cancer is the commonest gastrointestinal cancer and the second leading cause of cancer deaths in the United States. Recent approaches to lowering the incidence of colon cancer have included attempts at dietary prevention and chemoprevention. International and national incidence rates for colon cancer suggest an inverse relationship with dietary calcium and/or vitamin D intake (or sun exposure). Several human intervention studies have suggested that supplemental calcium administration will change proliferative indices of risk for colon cancer from high to lower risk patterns. The principal current hypothesis for the action of calcium implies that calcium may precipitate or bring out of solution fatty acids and bile acids that are potentially toxic to the colorectal epithelium. Both calcium administration and dairy food administration are associated with lowering aqueous fecal concentrations of bile acids and fatty acids accompanied by a highly significant lowering of cytotoxicity in studies in vitro. There is biochemical and biological evidence in cell culture systems that exposure to calcium and/or vitamin D reduces the oncogenic properties of colon cancer cells. A recent blinded study of the administration of low-fat dairy foods demonstrated a significant improvement in several parameters of proliferation as well as in two differentiation markers from a high to a lower risk pattern. Furthermore, administration of calcium also has been shown to reduce the incidence of recurrent adenomatous polyps in individuals at increased risk for colon polyp formation because of the presence of prior colon adenomata. These combined data suggest that administration of supplemental calcium or low-fat dairy foods may have a significant effect upon colonic polyp and perhaps colon cancer incidence.

Role of thyroid hormone in stimulating liver repopulation in the rat by transplanted hepatocytes

Recently, we reported near-complete repopulation of the rat liver by transplanted hepatocytes using retrorsine (RS), a pyrrolizidine alkaloid that alkylates cellular DNA and blocks proliferation of resident hepatocytes, followed by transplantation of normal hepatocytes in conjunction with two-thirds partial hepatectomy (PH). Because two-thirds PH is not feasible for use in humans, in the present study, we evaluated the ability of thyroid hormone (triiodothyronine [T(3)]), a known hepatic mitogen, to stimulate liver repopulation in the retrorsine model. Because T(3) initiates morphogenesis in amphibians through a process involving both cell proliferation and apoptosis, we also determined whether apoptosis might play a role in the mechanism of hepatocyte proliferation induced by T(3). Following hepatocyte transplantation and repeated injections of T(3), the number of transplanted hepatocytes in the liver of RS-pretreated animals increased progressively to repopulate 60% to 80% of parenchymal cell mass in 60 days. We show further that T(3) treatment augments proliferation of normal hepatocytes, as evidenced by increased histone 3 mRNA and cyclin-dependent kinase 2 (cdk2) expression, and this is followed by apoptosis. These combined effects of T(3) lead to selective proliferation of transplanted hepatocytes in RS-pretreated rats, while endogenous hepatocytes, which are blocked in their proliferative capacity by RS, mainly undergo apoptosis. Thus, T(3) can replace PH in the RS-based rat liver repopulation model and therefore represents a significant advance in developing methods for hepatocyte transplantation.

Overexpression of cyclin D1 occurs in both squamous carcinomas and adenocarcinomas of the esophagus and in adenocarcinomas of the stomach

Increased expression of the cyclin D1 gene frequently occurs in human squamous carcinomas of the esophagus. However, the expression of cyclin D1 has not been previously examined in detail in adenocarcinomas of the esophagus or stomach. Therefore, we examined, in parallel, the expression of cyclin D1 in both squamous and adenocarcinomas of the esophagus and in adenocarcinomas of the stomach. The level of expression of the cyclin D1 protein was assessed by immunohistochemistry in 39 esophageal and 34 gastric carcinomas and correlated with clinical and pathology parameters. Within the esophagus, 71% of the squamous carcinomas and 64% of the adenocarcinomas were positive for increased cyclin D1 nuclear staining. For adenocarcinomas of the stomach, the overall positive rate was 47%; in the gastric cardia, the rate was 44%, and in other regions of the stomach, it was 50%. In esophageal and gastric adenocarcinomas of the intestinal type, increased expression of cyclin D1 was seen in 70% of the samples, whereas with the diffuse type only 13% were positive (P < .01). Tumors from patients older than the median age of 67 years were more frequently positive than tumors from patients younger than 67 years (74% v 42%, respectively) (P < .01). Positive staining was also seen more frequently in well and moderately differentiated tumors than in poorly differentiated tumors (74% v 49%, respectively) (P < .05). Cytoplasmic staining for cyclin D1 was noted in 22% of the tumors, of various types. Therefore, increased expression of cyclin D1 frequently occurs in both adenocarcinomas and squamous carcinomas of the esophagus, and in adenocarcinomas of the stomach. The increased expression in adenocarcinomas is especially frequent in the intestinal-type lesions.

Lovastatin augments apoptosis induced by chemotherapeutic agents in colon cancer cells

Beta-hydroxy-beta-methylglutaryl coA reductase inhibitors (HRIs) inhibit isoprenylation of several members of the Ras superfamily of proteins and therefore have important cellular effects, including the reduction of proliferation and increasing apoptosis. Significant toxicity at high doses has precluded the use of HRIs as a monotherapy for cancers. We therefore studied whether combinations of the HRI lovastatin with standard chemotherapeutic agents would augment apoptosis in colon cancer cells. In the colon cancer cell lines SW480, HCT116, LoVo, and HT29, lovastatin induced apoptosis with differing sensitivity. Pretreatment with lovastatin significantly increased apoptosis induced by 5-fluorouracil (5-FU) or cisplatin in all four cell lines. Lovastatin treatment resulted in decreased expression of the antiapoptotic protein bcl-2 and increased the expression of the proapoptotic protein bax. The addition of geranylgeranylpyrophospate (10 microM) prevented lovastatin-induced augmentation of 5-FU and cisplatin-induced apoptosis; mevalonate (100 microM) was partially effective, whereas cotreatment with farnesyl pyrophosphate (100 microM) had no effect. These data imply that lovastatin acts by inhibiting geranylgeranylation and not farnesylation of target protein(s). Our data suggest that lovastatin may potentially be combined with 5-FU or cisplatin as chemotherapy for colon cancers.

Human right and left colon differ in epithelial cell apoptosis and in expression of Bak, a pro-apoptotic Bcl-2 homologue

BACKGROUND

Propensity to colonic neoplasia differs between the right and left colon.

AIMS

To examine whether this difference may be related to regional differences in epithelial apoptosis, in expression of a proapoptotic regulatory protein, Bak, and in proliferation.

PATIENTS

Individuals with no history of colorectal neoplasia.

METHODS

Archival blocks of colorectal tissues were immunostained for proliferating cells (antibody to Ki-67 antigen), and Bak expression (polyclonal antiserum). Cells containing DNA strand breaks, a marker of apoptosis, were identified by terminal deoxyuridine nucleotidyl nick end labelling (TUNEL).

RESULTS

There were fewer TUNEL positive epithelial cells in the right colon (mean 1.2 (SE 0.1)% of all epithelial cells) than the left colon (2.2 (0.1)%, p<0.0001) or rectum (2.2 (0.3)%, p<0.05). Bak expression was less common in the right colon (mean 46 (2.3)% of epithelial cells immunoreactive) than the left colon (66 (2.7)%, p<0.0001), or rectum (67 (2.3)%, p<0.001). Bak expression and TUNEL positivity were highly positively correlated (p<0.0001). In contrast to apoptosis, mean whole crypt proliferation labelling index was similar throughout the colorectum (right colon: 15.6 (3.2)%; left colon: 13. 5 (1.2)%; rectum: 13.3 (2.3)%).

CONCLUSION

The percentage of proliferating colonic epithelial cells is constant throughout the colon, but fewer epithelial cells undergo Bak mediated apoptosis in the right than in the left colon or rectum. This suggests that colonocytes may be lost by methods other than apoptosis in the right colon.

Association of K-ras mutations with p16 methylation in human colon cancer

BACKGROUND & AIMS

K-ras mutations are early genetic changes in colon cancer. p16, a tumor-suppressor gene, is inactivated in neoplasms by mutation, deletion, or methylation. The aims of this study were to determine p16 methylation status and its possible association with K-ras mutations in human colon cancer.

METHODS

DNA isolated from 8 colon cancer cell lines and 41 microdissected human colon tissue samples was analyzed. p16 methylation status was determined using two analytical methods. The level of p16 expression was determined by reverse-transcription polymerase chain reaction and Northern blot. K-ras mutations were determined by DNA sequence analysis. The DNA methyltransferase activity was determined by microassay. Parental and K-ras-transformed IEC-18 cells were used to determine the potential association between K-ras mutations and p16 methylation.

RESULTS

Methylated p16 was found in 100% of colon cancer cell lines, 55% of colon cancers, 54% of adenomas, and 25% of transitional mucosa but not in normal colonic epithelium. Forty-five percent of cancers and 38% of adenomas showed both K-ras mutations and p16 methylation. Of 11 cancers and adenomas with K-ras mutation, 10 specimens showed methylated p16. In contrast, of 13 adenomas and cancers with wild-type K-ras, only 3 specimens showed methylated p16 (P = 0.001). Stable transformation of IEC-18 cells with K-ras increased the DNA methyltransferase activity, methylated the p16 gene, and suppressed the expression of p16. Treatment with a DNA methylation inhibitor (azadeoxycytidine) resulted in reexpression of p16 in K-ras-transformed IEC-18 cells, suggesting that the expression of p16 was suppressed by DNA methylation.

CONCLUSIONS

p16 methylation occurs frequently in human colonic adenomas and cancers and is closely associated with K-ras mutations.

Modulation of abnormal colonic epithelial cell proliferation and differentiation by low-fat dairy foods: a randomized controlled trial

CONTEXT

Before the development of human colonic neoplasms, colonic epithelial cells showed altered growth and differentiation. These alterations characterized mucosa at risk for cancer formation and were termed intermediate biomarkers of risk. Modifications of the mucosa toward more normal features by nutrients or drugs are putative approaches to chemoprevention of colon cancer.

OBJECTIVE

To determine whether increasing calcium intake via dairy products alters colonic biomarkers toward normal.

DESIGN

Randomized, single-blind, controlled study.

SETTING

Outpatient clinic.

PARTICIPANTS

Seventy subjects with a history of polypectomy for colonic adenomatous polyps.

INTERVENTION

Low-fat dairy products containing up to 1200 mg/d of calcium. Subjects were randomized to 4 strata by diet (control vs higher calcium) and age (<60 vs > or = 60 years).

MAIN OUTCOME MEASURES

Changes in total colonic epithelial cells and number and position of thymidine-labeled epithelial cells and changes in the ratio of sulfomucins (predominantly secreted by distal colorectal epithelial cells) to sialomucins and expression of cytokeratin AE1, 2 markers of colonic cell differentiation.

RESULTS

During 6 and 12 months of treatment, reduction of colonic epithelial cell proliferative activity (P<.05), reduction in size of the proliferative compartment (P<.05), and restoration of acidic mucin (P<.02), cytokeratin AE1 distribution (P<.05), and nuclear size (P<.05) toward that of normal cells occurred. Control subjects showed no differences from baseline proliferative values at 6 and 12 months (P>.05).

CONCLUSION

Increasing the daily intake of calcium by up to 1200 mg via low-fat dairy food in subjects at risk for colonic neoplasia reduces proliferative activity of colonic epithelial cells and restores markers of normal cellular differentiation.

Diet restriction increases apoptosis in the gut of aging rats

Previous studies have shown that epithelial cell production rates are increased throughout the gastrointestinal tract in aging rats. We tested the hypothesis that alteration in cell death (apoptosis) might be involved. Fischer 344 rats aged 4-5 months and 24-25 months fed ad libitum (AL) or calorie restricted (CR) to 60% of the AL intake were studied. Epithelial cell apoptosis was determined by a terminal deoxyuridine nucleotidyl nick end labeling (TUNEL) technique validated in our laboratory, and the expression of four members of the Bcl-2 family was evaluated by Western blotting in the small intestine and colon. The apoptotic index was low in young and aging AL and young CR rats. However, CR in aging rats was associated with a significantly higher apoptotic index in the jejunum and colon. The expression of the Bcl-2 family of genes was unchanged. Enhanced apoptosis in CR may protect the gastrointestinal tract from accumulation of DNA-altered cells during the aging process.

Amaranthin lectin binding in the rat colon: response to dietary manipulation

BACKGROUND

In human colon, binding of the lectin Amaranthus caudatus has been considered to be a marker of cellular proliferation and malignant progression. We studied regional amaranthin binding in rat colon and correlated this with physiologic manipulations of proliferation.

METHODS

Binding of amaranthin in segments of proximal and distal colon was studied in starved, refed, and control Wistar rats and was compared to tritiated thymidine labeling and proliferating cell nuclear-antigen expression.

RESULTS

Amaranthin bound mainly to cells in the lower crypt of distal colon and midcrypt of proximal colon, paralleling the distribution of proliferative markers. Binding occurred in the supranuclear region in distal colon and the pericellular membrane in proximal colon. Starvation/refeeding was associated with a change in amaranthin binding intensity in distal colon, but not in proximal colon.

CONCLUSION

The pattern of amaranthin binding during starvation/refeeding seems to reflect physiologic changes in several areas of the colon.

A K-ras oncogene increases resistance to sulindac-induced apoptosis in rat enterocytes

BACKGROUND & AIMS

Mutations of c-K-ras occur commonly in colonic neoplasms. The aim of this study was to determine how c-K-ras mutations alter the responses to the chemopreventive agent sulindac.

METHODS

The parental rat intestinal cell line IEC-18 and c-K-ras-transformed derivatives were treated with sulindac sulfide. Cell cycle distribution was determined by flow-cytometric analysis (fluorescence-activated cell sorter), apoptosis by DNA fragmentation (laddering), flow cytometry, and microscopy, and changes in gene expression by immunoblotting.

RESULTS

Sulindac sulfide inhibited cell growth and induced apoptosis in a time- and dose-dependent manner more rapidly in and at lower concentrations in parental cells than ras-transformed cells. Expression of the sulindac sulfide arrested cells in G0/G1, but cells entered apoptosis throughout the cell cycle. Proapoptotic protein Bak was relatively high in untreated parental cells and increased markedly after sulindac sulfide but was low in untreated ras-transformed cells and did not increase after sulindac sulfide. Expression of other Bcl-2 family members was unchanged after sulindac sulfide. However, sulindac sulfide reduced levels of cyclin D1 protein and cyclin E- and cyclin D1-associated kinase activity.

CONCLUSIONS

c-K-ras-transformed enterocytes are relatively resistant to sulindac sulfide-induced growth inhibition and apoptosis, which may result from specific reduction of bak expression.

Apoptosis in gastric epithelial cells is induced by Helicobacter pylori and accompanied by increased expression of BAK

Carriage of the bacterium H. pylori in the human stomach is associated with evidence of increased epithelial cell apoptosis. This may be of significance in the etiology of gastritis, peptic ulcers, and neoplasia. The ability of H. pylori to directly induce epithelial apoptosis was examined in vitro by fluorescence and electron microscopy, flow cytometry, and DNA fragmentation ELISA. The induction of apoptosis by H. pylori was time and concentration-dependent and inhibited by preventing direct bacterial-epithelial cell contact. Apoptosis was accompanied by increased expression of Bak, with little change in expression of other Bcl-2 family proteins. The expression of Bak was also increased in gastric biopsies from patients colonized by H. pylori. Thus, H. pylori induces gastric epithelial cell apoptosis, by a Bak-dependent pathway.

Are right- and left-sided colon neoplasms distinct tumors?

Cancer of left and right colon has a differing prevalence at varying ages, in high- and low-incidence nations, as well as in men and in women. There also is a difference in clinical presentation, in prognosis, and possibly in genetic and environmental epidemiology. This review proposes that cancers of proximal and distal colon are different tumors because of their embryologic origin, genetic changes, and biologic identity. These factors are important in understanding the 'shift of tumors from more distal to more proximal sites in the colon' and in evaluating potential suggestions for instituting advances in diagnosis and prevention.

Helicobacter pylori cagA+ strains and dissociation of gastric epithelial cell proliferation from apoptosis

BACKGROUND

Infection with Helicobacter pylori induces chronic gastritis in virtually all infected persons, and such gastritis has been associated with an increased risk of developing gastric cancer. This risk is further enhanced with cagA+ (positive for cytotoxin-associated gene A) H. pylori strains and may be a consequence of induced gastric cell proliferation and/or alteration in apoptosis (programmed cell death) in the gastric epithelium.

PURPOSE

To determine whether the H. pylori cagA genotype and another virulence-related characteristic, the vacA (vacuolating cytotoxin A) s1a genotype, differentially affect epithelial cell proliferation, apoptosis, and the histologic parameters of inflammation and injury, we quantitated these characteristics in infected and uninfected persons.

METHODS

Fifty patients underwent upper gastrointestinal endoscopy, and biopsy specimens were taken. Apoptotic cells in the specimens were quantitated after terminal deoxynucleotidyl transferase labeling of DNA fragments with digoxigenin-deoxyuridine triphosphate; epithelial cell proliferation was scored by immunohistochemical analysis of the proliferation-associated antigen Ki-67. Antibodies directed against H. pylori and CagA protein were measured in the serum of patients by means of enzyme-linked immunosorbent assays. Analysis of H. pylori genomic DNA, by use of the polymerase chain reaction, was performed to determine the cagA and vacA genotypes. Acute and chronic inflammation, epithelial cell degeneration, mucin depletion, intestinal metaplasia, glandular atrophy, and vacuolation were each scored in a blinded manner. Reported P values are two-sided.

RESULTS

Persons harboring cagA+ strains (n = 20) had significantly higher gastric epithelial proliferation scores than persons infected with cagA-strains (n = 9) or uninfected persons (n = 21) (P = .025 and P<.001, respectively), but the difference in cell proliferation between the latter two groups was not statistically significant. The number of apoptotic cells per 100 epithelial cells (apoptotic index) in persons infected with cagA+ strains was lower than in persons infected with cagA-strains (P = .05). Apoptotic indices in the cagA+ group were similar to those in the uninfected group (P = .2). Epithelial cell proliferation was significantly correlated with acute gastric inflammation, but only in the cagA+ group (r = .44; P = .006). The cagA+ and vacA s1a genotypes were found to be concordant, confirming the close relationship between these virulence-related genotypes.

CONCLUSIONS

Gastric mucosal proliferation was significantly correlated with the severity of acute gastritis in persons infected with cagA+ vacA s1a strains of H. pylori. This increased proliferation was not accompanied by a parallel increase in apoptosis.

IMPLICATIONS

Increased cell proliferation in the absence of a corresponding increase in apoptosis may explain the heightened risk for gastric carcinoma that is associated with infection by cagA+ vacA s1a strains of H. pylori.

Antisense to cyclin D1 inhibits the growth and tumorigenicity of human colon cancer cells

Cyclin D1 plays an important role in regulating the progression of cells through the G1 phase of the cell cycle. This gene is frequently overexpressed in human colon cancer. To address the role of cyclin D1 in growth control and tumorigenesis in this disease, we have overexpressed an antisense cyclin D1 cDNA construct in the human colon cancer cell line SW480E8, which expresses high levels of cyclin D1. The integration and expression of the antisense construct was verified by Southern and Northern blot analyses, respectively, and resulted in decreased expression of the cyclin D1 protein. This was associated with decreased levels of the Rb and p27Kip1 proteins. In addition, the hypophosphorylated form of Rb was increased in these cells. The SW480E8 antisense cyclin D1 cells displayed an increased doubling time, a decrease in saturation density, decreased plating efficiency and anchorage-independent growth, and a loss of tumorigenicity in nude mice. These findings provide direct evidence that increased expression of cyclin D1 in colon tumor cells contributes to their abnormal growth and tumorigenicity. The ability to revert the transformed phenotype of these cells with antisense cyclin D1 suggests that cyclin D1 or its associated cyclin-dependent kinase 4 may be useful targets in the therapy of colon cancer.

Is Ki-67 a better proliferative marker in the colon than proliferating cell nuclear antigen?

Endogenous markers of proliferating cells have increasingly supplanted the use of incubation of biopsy tissues in vitro with tritiated thymidine or with bromodeoxyuridine, thus avoiding the potential variation resulting from the incubation procedure. Antibodies to proliferating cell nuclear antigen (PCNA) such as PC10 have been promoted as optimal for this purpose, although considerable variation in colonic proliferating cells with this antibody has been reported. We have compared the detection of colonic proliferating cells in normal mucosa and adenomata using the PC10 monoclonal antibody (mAb) to PCNA and the Mib-1 mAb to Ki-67 in formalin-fixed tissues using antigen retrieval solutions with microwaving. The PC10 antibody showed variable immunostaining of proliferating and nonproliferating cells with minor changes in primary antibody concentration or microwave conditions and between normal and adenomatous tissue. In contrast, Mib-1 immunostaining was quite constant with differing antigen retrieval and antibody conditions and similar staining of proliferating cells in colonic adenomas. Some loss of immunoreactivity occurred if the cut sections were not immunostained within approximately 1 week. These data suggest that whereas PCNA immunohistochemistry is satisfactory when carefully controlled in large chemopreventive studies, the Mib-1 mAb to Ki-67 is superior to PCNA antibodies in immunostaining proliferating cells in the formalin-fixed human colon.

Inward growth of colonic adenomatous polyps

BACKGROUND & AIMS

Most colon cancers arise from polypoid adenomas, but how these benign lesions develop into malignant neoplasms is not understood. This study examined the migration of epithelial cells within human adenomatous polyps by determining the distribution of proliferating and apoptotic cells and immunoreactivity to transforming growth factor beta (TGF-beta).

METHODS

Sections of surgically resected normal (n = 10) and adenomatous (n = 22) formalin-fixed tissue were examined for proliferating cells and TGF-beta isoenzymes 1-3 by immunohistochemistry and apoptotic cells by terminal deoxyuridine nick end-labeling.

RESULTS

The distribution of proliferating, apoptotic, and TGF-beta immunoreactive cells was strikingly reversed in adenomatous polyps compared with normal mucosa. Proliferating cells were located in the base of normal colonic crypts and TGF-beta immunoreactive and apoptotic cells near or at the luminal surface, corresponding to the normal migration of colonocytes. In adenomas, increased numbers of proliferating cells were mainly located at the luminal surface and TGF-beta immunoreactive and apoptotic cells were located principally at the crypt base.

CONCLUSIONS

This distribution suggests that cell migration in adenomas is not toward the lumen but instead inward toward the polyp base.

Increased small intestinal apoptosis in coeliac disease

BACKGROUND

Coeliac disease (CD) mucosa is flattened despite epithelial hyperproliferation.

AIMS

To establish mechanisms of cell loss in CD.

PATIENTS

14 controls, 17 active CD patients, and 16 maintained with gluten free diet.

METHODS

Programmed cell death was examined in small intestinal biopsy specimens by staining fragmented DNA using terminal uridine deoxynucleotidyl nick end labelling (TUNEL), in comparison with haematoxylin and eosin stained adjacent sections. Double staining with anti-CD45 antibodies determined the origin of apoptotic cells. Apoptosis was graded from 1-3 (< 5, 5-20, > 20% respectively). Proliferating cells, immunostained by Ki-67 (MIB-1) antibody, were counted.

RESULTS

Apoptotic cells were seen rarely by haematoxylin and eosin but more readily by TUNEL. In controls, 1.4 +/- 0.2% of epithelial cells were apoptotic (mean grade 1.1), mainly located in the upper villus. In active CD, frequent apoptotic cells were distributed throughout the crypt-villus unit (mean grade 2.4), decreasing after treatment to 1.1 (p < 0.001) even when still histologically abnormal. CD45 antibodies rarely stained apoptotic cells in active CD. The number of TUNEL positive cells correlated with proliferating cell number (p < 0.001).

CONCLUSION

Enterocyte apoptosis is greatly increased in untreated CD, correlates with proliferation, and falls to normal with a gluten free diet, before histological improvement. Increased apoptosis may be responsible for villous atrophy in CD.

Fecal and rectal mucosal diacylglycerol concentrations and epithelial proliferative kinetics

Fecal diacylglycerol (DAG) concentrations have been suggested as biomarkers for colonic neoplasia because of their potential to be absorbed in the colon and to stimulate epithelial cell proliferation. The interrelationships among nutrient intake, fecal and mucosal DAG, and colonic proliferative markers have not previously been studied. We designed a pilot study to evaluate the feasibility of evaluating these interrelationships in 12 volunteers who had a history of colonic adenomatous polyposis. Total mucosal DAG concentrations were not related to fecal DAG concentrations, but mucosal DAG correlated inversely with the whole crypt labeling index. Dietary intake did not alter fecal DAG concentrations. However, the percentage of calories from dietary fat correlated positively with the whole crypt labeling index. Fiber and calcium intake showed a positive correlation with the labeling index in the upper 40% of the crypt. The present pilot study failed to demonstrate a correlation between dietary components and fecal and total mucosal DAG. Additional studies relating fecal DAG with mucosal proliferation will require the evaluation of DAG concentrations in subcellular compartments of mucosal cells and/or measurement of fecal DAG fatty acid composition.

Abnormalities of epithelial apoptosis in multistep colorectal neoplasia demonstrated by terminal deoxyuridine nick end labeling

Colonic carcinogenesis is accompanied by progressive genetic changes and alterations in growth control. To examine whether abnormalities of apoptosis are involved in carcinogenesis, we examined epithelial apoptosis in formalin-fixed normal and neoplastic colon by terminal uridine deoxynucleotide nick end-labeling (TUNEL) histochemistry. In normal colon, resection margins, and hyperplastic polyps, TUNEL-positive cells comprised around 3% of total colonocytes, with over 85% of these cells located in surface epithelium between crypts. In adenomas, there were significantly fewer TUNEL-positive cells at the luminal surface than normal (1.82 +/- 0.51% of epithelial cells, compared with 12.1 +/- 2.3%, P < 0.05) and a trend to increased numbers at the crypt base (2.70 +/- 0.98% compared with 0.65 +/- 0.15%). Carcinomas contained fewer TUNEL-positive cells than normal (1.7 +/- 0.27%), and they are randomly distributed. Transitional mucosa had significantly more TUNEL-positive colonocytes than normal (11.0 +/- 3.0%, P < 0.005), both at the surface and crypt base. These results show that colonocyte apoptosis normally occurs mainly in luminal cells but that early during carcinogenesis the distribution and quantity of apoptotic cells changes.

Effects of acarbose on fecal nutrients, colonic pH, and short-chain fatty acids and rectal proliferative indices

Acarbose, an alpha-glycosidase inhibitor, treats diabetes mellitus by delaying the digestion and intestinal absorption of dietary carbohydrates. In effective doses, acarbose induces some passage of carbohydrates into the colon. The effect of such chronic carbohydrate transfer on colonic structure and function is unknown. We studied the effects of 1 year of acarbose administration in diabetes mellitus on fecal energy, protein, and fat, including short-chain fatty acids (SCFA) output, fecal pH, and several metabolizing bacterial species. Changes in colonic histology and epithelial cell proliferation were investigated in rectal biopsies. Fecal macronutrient output was unaffected by acarbose, but pH decreased and total SCFA, butyrate, and acetate output were markedly greater. Breath hydrogen output increased after acarbose, but digoxin-metabolizing bacteria and diacylglycerol (DAG) production were unaltered. Compared with the control, acarbose did not induce hyperplasia or change rectal proliferation. However, total fecal SCFA and butyrate output correlated inversely with proliferation in the rectal upper crypt-a biomarker of risk for colonic neoplasia. In conclusion, long-term acarbose administration does not adversely affect colonic function or fecal nutrient output. If increased fecal SCFA and butyrate reduces upper-crypt proliferation, then acarbose may reduce the risk of colonic neoplasia.

30 KDa phosphorylated form of Bcl-2 protein in human colon

Bcl-2 expression was studied in a human colon cell line (HT-29) and in human colonic biopsies by Western and Northern blotting. Polyclonal antibodies raised against the Bcl-2 protein detected the expected 26 KDa protein in human colon. However, although Bcl-2 mRNA was present, the 26 KDa Bcl-2 protein was absent in HT-29 cells. Instead, a 30 KDa protein band strongly reacting with anti-Bcl-2 antibodies was found in HT-29 cells, and also in human colon, tonsil, and some other tissues. Alkaline phosphatase shifted the 30 KDa protein to the 26 KDa position in a time-dependent manner. 32P-labeling of HT-29 cells showed that the 30 KDa protein was phosphorylated. A 27 KDa phosphorylated protein was also immunoprecipitated by anti-Bcl-2 antibody. Phosphopeptide mapping showed that the 27 KDa protein contained a minimum of 3 and the 30 KDa protein at least an additional four phosphorylation sites. Phosphoamino acid analysis revealed that both the 30 KDa and 27 KDa proteins were phosphorylated on serine residues. These findings strongly suggest that the 30 KDa protein is a phosphorylated form of Bcl-2, which is widely distributed in human tissues.

Increased intestinal Bak expression results in apoptosis

Cells in the human intestinal epithelium have a life-span of around 5 days before being lost by apoptosis at the luminal surface. We examined changes in expression of the Bcl-2 gene family which may be responsible for epithelial cell loss. In the normal and neoplastic colon, mucosal expression of immunoreactive Bak co-localized with sites of epithelial cell apoptosis. Inducing apoptosis in the human colon cancer cell line HT29 and the rat normal small intestinal cell line IEC 18 in culture was accompanied by increased Bak expression without consistent changes in expression of other Bcl-2 homologous proteins. Bak appears to be the endogenous Bcl-2 family member best correlated with intestinal cell apoptosis.

Increased expression of the cyclin D1 gene in Barrett's esophagus

Previous studies have found a 3-10-fold amplification and overexpression of the cyclin D1 gene in about 32% of human esophageal squamous cell carcinoma. The purpose of this study was to evaluate the prevalence of increased expression of the cyclin D1 protein in Barrett's esophagus. Using 69 formalin-fixed and paraffin-embedded human esophageal specimens, which had been removed endoscopically or obtained at surgery during 1993 and 1994, all immunohistochemical analyses were performed using an avidin-biotin complex immunoperoxidase technique. Increased nuclear expression of the cyclin D1 protein was noted in 32 of 69 samples (46%; 44% of the samples from males and 50% of the samples from females). Positive nuclear staining for the cyclin D1 protein in Barrett's disease with intestinal metaplasia was found in 38% of the male cases and 25% of the female cases, whereas in gastric metaplasia it was positive in 33% of men and 48% of women. Nuclear accumulation of the cyclin D1 protein was also found in both dysplastic and nondysplastic lesions, and it was not associated with sex, age, or cigarette or alcohol consumption. Samples from patients taking proton pump inhibitors tended to be less frequently positive (32%) for cyclin D1 nuclear staining when compared to patients taking H2 antagonists (45%) or antacids (55%). These studies suggest that increased expression of cyclin D1 is an early event in the tumorigenic process of esophageal adenocarcinomas and that the increased expression of this gene might predispose the epithelium to malignant transformation.

Calcium carbonate treatment of diarrhoea in intestinal bypass patients

OBJECTIVE

To study the effect of supplemental calcium carbonate on faecal water, calcium, bile acid and lipid concentration and output in intestinal bypass subjects with diarrhoea.

DESIGN

Prospective, single-arm treatment trial of oral calcium carbonate, 2400 or 3600 mg Ca2+ per day, given for 12 weeks.

METHODS

Faecal constituents were determined in wet or lyophilized stool of 24-h collections at baseline and at 12 weeks of study. Calcium was measured by absorption spectrophotometry. Bile acids, long-chain fatty acids and short-chain fatty acids were analysed by gas chromatography.

RESULTS

In 15 subjects, calcium supplementation reduced bowel frequency by a mean of 49%, faecal wet weight by a mean of 50% (1292 to 646 g per day), and dry weight by a mean of 36%, P < 0.001. Faecal water concentration was reduced from 76.4 +/- 1% to 70.2 +/- 2%, P < 0.01. Faecal water concentration was inversely correlated with dry faecal calcium concentration (r = -0.75 P = 0.00001).

CONCLUSION

Calcium reduces the diarrhoea of intestinal bypass patients. It is suggested that the constipating effect of calcium may be related to reduction in faecal water.

Elevated expression of Bcl-X and reduced Bak in primary colorectal adenocarcinomas

Expression of several members of the BCL-2 family of genes was investigated by immunohistochemical methods in 30 primary colorectal adenocarcinomas and 24 adenomatous polyps. When compared to the intensity observed in adjacent normal mucosal epithelial cells, the intensity of Bcl-X immunostaining was elevated in 18 of 30 (60%) carcinomas (P = 0.0001) and 12 of 24 (50%) adenomatous polyps (P = 0.0001). Immunoblot analysis of five pairs of tumors and adjacent normal colonic tissue indicated marked elevations in the relative levels of the anti-apoptotic Bcl-XL, protein in all cases. In contrast to the increased Bcl-X expression, the intensity of Bcl-2 immunostaining was greater than that of normal colonic mucosa in only 3 of 30 (10%) carcinomas and, in fact, was lower than that of adjacent normal epithelia] cells in 25 (83%) cases (P = 0.0001). Furthermore, the percentage of Bcl-2 immunopositive cells was generally lower in carcinomas than in adenomas (mean +/- SE, 44 +/- 6% versus 73 +/- 5%, respectively; P = 0.001) and in moderately or poorly differentiated tumors than in well-differentiated tumors (39 +/- 6% versus 70 +/- 11%, respectively; P = 0.045). In addition, the proportion of tumors in which the Bcl-2 immunointensity was more than or equal to that of normal colonic mucosa was significantly lower in carcinomas than adenomas (5 of 30 versus 15 of 24, respectively; P < 0.001), suggesting that decreases in Bcl-2 expression represent a later event associated with the progression of colorectal cancers. When compared to that of normal adjacent colonic epithelium, the intensity of Mcl-1 immunostaining was reduced in 20 of 30 (67%) of carcinomas (P = 0.0001) compared to only 1 of 24 adenomas, suggesting that decreases in Mcl-1 expression represent a later event associated with progression from a benign to a malignant phenotype or with transition to a less-differentiated state, because most of the carcinomas evaluated here (25 of 30; 83%) were not well differentiated. The intensity of immunostaining for the pro-apoptotic protein Bak was reduced compared to that of normal mucosal epithelial cells in 27 of 30 (90%) carcinomas and 22 of 24 (92%) adenomas, suggesting that reductions in Bak expression occur early in colorectal tumor progression (P = 0.0001). In contrast, the intensity of immunostaining for the pro-apoptotic protein Bax was not significantly altered in carcinomas; compared to that of normal colonic mucosa, Bax immunointensity was reduced in only 7 of 30 (23%) carcinomas and 3 of 24 (13%) adenomas, and the percentage of Bax immunopositive cells was also not significantly different in any of the histological subgroups. Taken together, these results suggest that expression of Bcl-XL is increased in undifferentiated primary colorectal cancers, often with accompanying reciprocal decreases in the anti-apoptotic proteins Bcl-2 and Mcl-1 and the pro-apoptotic protein Bak, whereas Bax expression is relatively constant. Thus, a shift from expression of the anti-apoptotic proteins Bcl-2 and Mcl-1 to the Bcl-XL protein may occur during progression of colorectal tumors.

Increased expression of cyclin D1 and the Rb tumor suppressor gene in c-K-ras transformed rat enterocytes

Activating mutations in the c-K-ras gene occur in about 40% of human colorectal carcinomas, yet the role of this oncogene in tumorigenesis is not known. We have developed a model cell culture system to study this problem, utilizing the immortalized but non-tumorigenic epithelial cell line IEC18, originally derived from normal rat intestine epithelium. These cells were cotransfected with the drug resistance selectable marker tk-neo and the plasmid pMIKcys, which encodes a mini human c-K-ras gene (15 kb) containing a cysteine mutation at codon 12. Drug resistant clones were isolated. Clones which also expressed the activated c-K-ras gene displayed a transformed morphology, decreased doubling time, increased level of diacylglycerol, anchorage independent growth in soft agar and an aneuploid karyotype and they were also tumorigenic when injected into nude mice. These clones also displayed increased expression, at both the mRNA and protein levels, of cyclin D1 and Rb. These findings may be of clinical relevance since human colorectal tumors also frequently display increased expression of both cyclin D1 and Rb. This model system may be useful for understanding the role and interrelationship between activation of the c-K-ras oncogene and increased expression of cyclin D1 and Rb in colorectal tumorigenesis.

Induction of gastric epithelial apoptosis by Helicobacter pylori

BACKGROUND

Helicobacter pylori may promote gastric carcinogenesis through increasing gastric epithelial cell proliferation. How H pylori does so is unknown. Programmed, non-necrotic, cell death (apoptosis) occurs throughout the gut and is linked to proliferation. It was hypothesised that H pylori may induce hyper-proliferation through increasing apoptosis.

AIM

To measure the effect of H pylori infection on gastric epithelial apoptosis in situ.

PATIENTS

Patients with duodenal ulcers treated to eradicate H pylori and patients with H pylori negative non-ulcer dyspepsia.

METHODS

Retrospective quantification of apoptotic epithelial cells in situ from formalin fixed biopsy specimens, counted after staining by terminal uridine deoxynucleotidyl nick end-labelling.

RESULTS

In the uninfected stomach, apoptotic cells were rare and situated in the most superficial portion of gastric glands (mean 2.9% of epithelial cells). In H pylori infection, they were more numerous and were located throughout the depth of gastric glands, comprising 16.8% of epithelial cells, falling to 3.1% after H pylori eradication, p = 0.017. Apoptotic cell number did not correlate with the degree of histological gastritis.

CONCLUSIONS

These results suggest that H pylori induces epithelial apoptosis in vivo. Increased apoptosis may be the stimulus for a compensatory hyperproliferative and potentially preneoplastic response in chronic H pylori infection.

Increased expression of cyclin D1 is an early event in multistage colorectal carcinogenesis

BACKGROUND & AIMS

Cyclin D1 gene amplification and/or overexpression occurs in several human cancers. The level of expression of cyclin D1 protein during the multistage process of human colon carcinogenesis was determined.

METHODS

Cyclin D1 protein abundance was determined by immunostaining samples of normal colonic mucosa(n=23), transitional normal mucosa adjacent to adenomas or adenocarcinomas (n=41), hyperplastic polyps (n=8), adenomatous polyps (=35), and adenocarcinomas (n=27), using a polyclonal anti-human cyclin D1 antibody.

RESULTS

Cyclin D1 nuclear staining occurred in 30% of adenocarcinomas and 34% of adenomatous polyps but not in hyperplastic polyps or normal or transitional mucosa. Nuclear staining did not correlate with sex, age, size, or dysplasia of the adenomatous polyps or with differentiation and Dukes' staging of the adenocarcinomas. Left-sided colon neoplasms showed nuclear staining more frequently than those right-sided lesions. Diffuse or supranuclear cytoplasmic staining occurred in about one third of hyperplastic polyps, adenomas, and adenocarcinomas and in transitional mucosa adjacent to adenocarcinoma.

CONCLUSIONS

Increased nuclear expression of cyclin D1 occurs in around one third of colonic tumors as an early event during multistage process of colon carcinogenesis. Increased expression of cyclin D1 may perturb cell-cycle control in benign adenomas and thereby enhance tumor progression.

Frequent K-ras mutations in small bowel adenocarcinomas

The reasons for the relatively rare occurrence of small bowel adenocarcinomas when compared to the high frequency of colonic adenocarcinomas are unknown. Activating mutations in the K-ras oncogene occur in about 40% of colonic adenocarcinomas, possibly reflecting the consequences of carcinogenic exposure. To study whether the low incidence of small bowel adenocarcinomas might be due to the absence of activation of cellular oncogenes in small bowel adenocarcinomas, we examined the frequency of K-ras mutations in small bowel adenocarcinomas. K-ras mutations were determined using a polymerase chain reaction (PCR)-based method to detect codon 12 mutations by restriction fragment length polymorphism. PCR amplification was successful in six of nine small bowel adenocarcinoma samples, and revealed point mutations of K-ras at codon 12 in five of these six cases. We conclude that the small bowel might be exposed to carcinogens similar to those responsible for colorectal cancer, but may have developed protective mechanisms against cancer formation.