Cost-effectiveness model for colon cancer screening

The relative efficacy and effectiveness of different colon screening programs has not been assessed. The purpose of this analysis was to provide a model for comparing several colon screening programs and to determine the key variables that impact program effectiveness. Five screening programs were compared: annual fecal occult blood test (FOBT) alone, flexible sigmoidoscopy, flexible sigmoidoscopy and FOBT combined, one-time colonoscopy, and air-contrast barium enema. Key variables were adjusted for sensitivity analyses. Cost-effectiveness was defined as the cost per cancer death prevented. FOBT alone prevents fewer cancer deaths than the other programs. The addition of flexible sigmoidoscopy to the FOBT increases the rate of cancer prevention. One-time colonoscopy has the greatest impact on colorectal cancer mortality, largely because of assumptions that cancer would be prevented in most patients who undergo polypectomy. FOBT alone is the most cost-effective of the programs, but the cost is sensitive to several key variables. The model shows key variables that impact the cost-effectiveness of colon screening programs. Compliance is an important determinant of effectiveness of all of the screening programs. Future study should be focused on methods of patient education that improve patient compliance with screening.     

The effects of and interactions between fermentable dietary fiber and lipid in germfree and conventional mice

Dietary fiber can stimulate intestinal epithelial cell proliferation. The aim of this study was to resolve the different roles of fermentation and intraluminal viscosity on this trophic action and to investigate reported interactions between fiber and dietary fat. Conventional and germfree mice were fed guar gum in combination with low- or high-lipid diets for 2 weeks, and crypt cell production rates were determined. Guar gum significantly stimulated proliferation in the small intestine, especially when combined with fat. Lipid itself also stimulated proliferation in the small intestine and had a direct trophic effect in the cecum and colon of the germfree mice. Fiber markedly stimulated proliferation in the cecum and colon but only in the conventional group. Interactions between lipid and bacteria and between guar gum and bacteria were also observed in the small intestine. Guar gum has a trophic effect in the small bowel, probably related to viscosity, in addition to its fermentation-related actions in the colon. Positive interaction with lipid may be associated with delayed absorption. Lipid also has its own direct actions on small bowel mucosal proliferation, which are attenuated by the presence of bacteria.     

Microsatellite instability in human colonic cancer is not a useful clinical indicator of familial colorectal cancer

Microsatellite instability is a property of most tumors occurring in the context of hereditary nonpolyposis colon cancer. Instability also occurs in 10%–15% of apparently sporadic colorectal cancers, and it has been hypothesized that this instability may indicate a genetic predisposition to colonic cancer. This study evaluated whether there is a clinically useful association between colon cancer instability and a family history of cancer. Colon cancer cases (n = 188) from a population-based study were evaluated for microsatellite instability with 10 polymerase chain reaction primer sets. Instability results were compared with family history and other clinical and biological characteristics. Microsatellite instability was found in 16.5% of tumors. It was predominantly a feature of right-sided tumors (P = 0.003) and was associated with the youngest and oldest ages at diagnosis (P = 0.01). Instability was not associated with family history of cancer, sex of the individual, or the glutathione-S-transferase mu 1 null genotype. Although some very small, and as yet undefined, proportion of colon cancer may be caused by inherited mutations leading to microsatellite instability, tumoral instability by itself is not a marker for familiality and should not be considered as evidence for an inherited syndrome.     

Subcellular localization of hepatitis B core antigen in relation to hepatocyte regeneration in chronic hepatitis B

To test whether the dominant cytoplasmic expression of hepatitis B core antigen (HBcAg) in active chronic hepatitis B is secondary to liver damage and regeneration, the relationship between subcellular localization of HBcAg, liver inflammatory activity, and hepatocyte regeneration in chronic hepatitis B was studied. Correlation of the clinical and laboratory data with the topographical distribution of HBcAg was studied in 30 patients. The subcellular localization of HBcAg in relation to hepatocyte cell cycles was studied by double immunostaining of HBcAg and proliferating cell nuclear antigen. Patients with predominant cytoplasmic HBcAg had significantly higher levels of biochemical and histological activities and proliferating cell nuclear antigen expression than patients with predominant nuclear HBcAg. The levels of proliferating cell nuclear antigen expression correlated positively with biochemical and histological activities and degrees of cytoplasmic HBcAg expression but negatively with degrees of nuclear HBcAg expression. Proliferating cell nuclear antigen expression was shown in 49% of hepatocytes with cytoplasmic HBcAg but in only 2% of hepatocytes with nuclear HBcAg. These findings suggested that, following liver damage, the regeneration of surviving hepatocytes might cause the shift of intracellular HBcAg from nucleus to cytoplasm. As a result, the extent of nuclear HBcAg expression reduces with concomitant increase in cytoplasmic HBcAg expression.     

Absence of human papillomavirus DNA detected by polymerase chain reaction in French patients with esophageal carcinoma

Recent studies have suggested that esophageal human papillomavirus infection could be a risk factor for esophageal squamous cell carcinoma. The aim of this study was to evaluate the prevalence of human papillomavirus DNA sequences in the esophagus of French patients with esophageal squamous cell carcinoma. Multiplex polymerase chain reactions with consensus primers directed to the L1 gene or specific primers for human papillomavirus types 6, 11, 16, 18, 31, and 33 directed to E6 gene (40 cycles followed by restriction mapping of the amplified products) were used to determine the presence of human papillomavirus DNA sequences in esophageal squamous cell carcinoma (n = 75), normal adjacent mucosa (n = 49), and metastatic lymphadenopathies (n = 5). As an internal control, a target located in the embryonic myosin heavy-chain gene was used in each reaction. Human papillomavirus DNA sequences could not be detected in any of the tumoral samples, the normal adjacent mucosa, or the metastatic lymphadenopathies. Human papillomavirus seems not to be implicated in esophageal carcinogenesis, at least in French patients, because the viral genomes are not associated with esophageal squamous cell carcinomas.     

Antibody-targeted lymphokine-activated killer cells inhibit liver micrometastases in severe combined immunodeficient mice

Animal models for hepatic metastases can facilitate the investigation of lymphokine-activated killer (LAK) cell-based immunotherapy. The aim of this study was to investigate the efficacy of ccM4 antibody-targeted LAK cells in inhibiting hepatic micrometastases. Hepatic micrometastases were generated after the intrasplenic injection of HM7 colon carcinoma cells. TAG72 expression was detected in these hepatic micrometastases using ccM4 antibody. The ccM4 antibody was conjugated onto LAK cells by treatment with 17.5% polyethylene glycol 8000. After the intrasplenic injection of HM7 cells, severe combined immunodeficient mice were randomized into five groups (i–v) and received either 10⁷ ccM4-LAK cells plus 1000 U interleukin 2 (IL-2; group i), LAK cells plus 50 μg ccM4 and IL-2 (group ii), LAK cells plus IL-2 (group iii), IL-2 alone (group iv), or only phosphate-buffered saline (group v). The ccM4-LAK cells retained cytolytic activity and acquired TAG72-binding reactivity. The results showed that group i had significantly fewer hepatic metastases compared with group ii or group iii (P < 0.05) and even fewer hepatic metastases compared with group iv or group v (P < 0.001). These results show that ccM4 antibody-targeted LAK cells significantly inhibited tumor growth in vivo; thus, they can be potentially useful in treatment of hepatic micrometastases.     

Beneficial effect of fructose-1,6-bisphosphate on mitochondrial function during ischemia-reperfusion of rat liver

Several groups have reported that administration of fructose-1,6-bisphosphate (FBP) reduces ischemic injury. The aim of this study was to determine the protective effect of FBP on the impairment of mitochondrial oxidative phosphorylation by ischemia-reperfusion injury in the rat liver. The respiratory control ratio (RCR) and the adenine nucleotide content of mitochondria isolated from ischemic and reperfused livers with or without FBP treatment were measured. In FBP-treated livers, the cellular adenosine triphosphate level was restored to more than 50% of normal after 120 minutes of reperfusion following 120 minutes of ischemia, whereas that of control livers only reached 15% of normal. The RCR and the adenine nucleotide content of mitochondria isolated from FBP-treated livers were significantly higher than those of mitochondria from control livers after ischemia and reperfusion. FBP strongly suppressed the formation of lipid peroxides during reperfusion. In vitamin E-deficient rats, the RCR decreased markedly during reperfusion, but FBP protected the mitochondria against reperfusion injury. FBP has a protective effect against ischemia-reperfusion injury on the liver and especially preserves the oxidative phosphorylation capacity of hepatic mitochondria.     

Shc is a substrate of the rat intestinal epidermal growth factor receptor tyrosine kinase

Epidermal growth factor (EGF) has been shown to induce intestinal proliferation and maturation; however, little information is available regarding substrates of the intestinal EGF receptor tyrosine kinase. The purpose of this study was to determine if src homologous collagen-like protein (Shc) was an in vivo substrate of the intestinal EGF receptor. Ten-day-old rats were treated with EGF or were breast-fed. In some experiments, IEC-6 cells were treated with EGF. Intestinal tissue and cell fractions were studied by immunodetection to compare the tyrosine phosphorylation state and the subcellular localization of intestinal proteins. The total tyrosine phosphorylation state of intestinal proteins was increased threefold by EGF. Tyrosine phosphorylation of the EGF receptor and Shc were rapidly increased by EGF. The association of Grb2 with Shc increased fourfold and fivefold. Plasma membrane translocation of Shc and associated phosphotyrosyl proteins was increased within 30 seconds of EGF treatment. Shc is a substrate of the intestinal EGF receptor in vivo. EGF-induced association of Shc with the adapter protein Grb2 may have implications for activation of the p21^ras signaling pathway in the intestine. The EGF-induced membrane association of Shc with two other phosphotyrosyl proteins suggests involvement of Shc in additional aspects of EGF-receptor signaling in the intestine.     

An intravenous loading dose of azathioprine decreases the time to response in patients with Crohn's disease

Azathioprine, an effective therapy for Crohn's disease, is limited by a prolonged time to response. The aim of this study was to determine the safety and utility of a loading dose of azathioprine to decrease the time to response in patients with Crohn's disease. Twelve patients were studied: 6 with 13 fistulae and 6 with inflammatory disease. All patients received an intravenous infusion of azathioprine (50 mg/h for 36 hours). Response was determined by physical and radiographic examination for fistulae and by the Crohn's Disease Activity Index for inflammatory disease. Erythrocyte concentrations of azathioprine metabolites were measured by chromatography. Seven of 13 fistulae closed by week 4, and three had a temporary decrease in drainage. One fistula improved at week 16. Two fistulae failed to improve. Four of 6 patients with inflammatory disease achieved remission, and 1 improved temporarily. Improvement was rapid (≤4 weeks). Peak concentrations of azathioprine metabolites occurred within 3 days. Clinical response did not correlate with azathioprine metabolite concentrations at the azathioprine dose studied. No adverse events occurred. An 1800-mg intravenous loading dose of azathioprine is safe and may decrease the time to response to ≤4 weeks in patients with Crohn's disease. Correlation between clinical response and azathioprine metabolite concentrations at larger azathioprine doses should be determined.     

Changes in the site- and histology-specific incidence of gastric cancer during a 50-year period

In contrast to the dramatic decrease in the overall incidence of gastric cancer, there has been a reported increase in the incidence of cases located in the gastric cardia. The aim of this study was to identify changes in site- and histology-specific incidence rates of gastric adenocarcinoma during a 50-year period. The Rochester Epidemiology Project medical records linkage system was used to identify all cases of gastric adenocarcinoma among residents of Olmsted County, Minnesota, between 1941 and 1990 (n = 342). Each patient's complete (inpatient and outpatient) medical records were reviewed and tumor location determined from pathological, surgical, endoscopic, and radiological reports. All available histological specimens (n = 246) were reviewed independently. The overall incidence of gastric cancer decreased from 48.8 per 100,000 person-years in the 1940s to 11.6 per 100,000 in the 1980s, whereas the incidence of adenocarcinoma of the cardia did not change significantly during the 50-year period. The incidence of adenocarcinoma of the esophagogastric junction increased from 0.0 to 1.9 per 100,000 person-years, but the number of cases was small. The incidence of adenocarcinoma of the gastric cardia has not increased in this population. The reported increase in cardia cancer in other populations may be due to an increasing incidence of adenocarcinoma of the esophagogastric junction.     

Virion-like structures in HeLa G cells transfected with the full-length sequence of the hepatitis C virus genome

The process and the site of hepatitis C virus (HCV) particle formation in cells after infection remain unknown. The aim of this study was to create an in vitro model for the study of HCV particle formation. HeLa G cells were transfected with the full-length sequence of the HCV genome. Viral protein expression was analyzed using immunoblotting. The cells were examined using immunoelectron and conventional electron microscopy. Core, E2, NS3, NS5a, and NS5b proteins were identified using immunoblotting. Immunoelectron microscopy showed that the core antigen was located along the membrane of the endoplasmic reticulum (ER) and occasionally in its cisternae. Core antigen-positive particles of 30 nm in diameter were found in the cytosol and in the cisternae of the ER. The particles in the cisternae were coated with an outer membrane that was connected to the ER membrane. Conventional electron microscopy revealed particles of 45 nm in diameter with electrondense cores in the cisternae of the ER. The outer membrane of the particles was occasionally connected to the ER membrane. The findings suggest that HCV core proteins are synthesized and assembled into particles in the cytosol and that they bud into the cisternae of the ER to form coated particles.     

Rat Kupffer cell-derived nitric oxide modulates induction of lymphokine-activated killer cell

Nitric oxide is now recognized to regulate immune responses and cell viability in various organs. The present study was designed to clarify whether NO released from Kupffer cells modulates the lymphokine-activated killer (LAK) activity of interleukin 2 (IL-2)-treated splenocytes. Splenocytes and Kupffer cells were isolated from male Wistar rats and cocultured for 48 hours in the presence of lipopolysaccharide (1 μg/mL). The splenocyte LAK activity and expression of IL-2 receptor were determined. Kupffer cells with lipopolysaccharide reduced the IL-2 receptor expression and LAK activity of splenocytes. The addition of either N^G-monomethyl-l-arginine, an inhibitor of NO synthesis, or aminoguanidine, an inhibitor of inducible NO synthase, to the medium reversed the suppression of IL-2 receptor expression and LAK activity by lipopolysaccharide-stimulated Kupffer cells. 8-bromoguanosine 3′,5′-cyclic monophosphate and NO donors decreased the splenocyte LAK activity and IL-2 receptor expression. Treatment with lipopolysaccharide increased the inducible NO synthase activity as well as the nitrite and nitrate levels in the culture medium of Kupffer cells but not in splenocytes. The results of this study suggest that NO produced by the inducible NO synthase of Kupffer cells in response to lipopolysaccharide modulates the IL-2 receptor expression and LAK activity of splenocytes.     

Antioxidant activity of silybin in vivo during long-term iron overload in rats

Hepatic iron toxicity may be mediated by free radical species and lipid peroxidation of biological membranes. The antioxidant property of silybin, a main constituent of natural flavonoids, was investigated in vivo during experimental iron overload. Rats were fed a 2.5% carbonyl-iron diet and 100 mg · kg body wt⁻¹ · day⁻¹ silybin for 4 months and were assayed for accumulation of hepatic lipid peroxidation by-products by immunocytochemistry, mitochondrial energy-dependent functions, and mitochondrial malondialdehyde content. Iron overload caused a dramatic accumulation of malondialdehyde-protein adducts into iron-filled periportal hepatocytes that was decreased appreciably by silybin treatment. The same beneficial effect of silybin was found on the iron-induced accumulation of malondialdehyde in mitochondria. As to the liver functional efficiency, mitochondrial energy wasting and tissue adenosine triphosphate depletion induced by iron overload were successfully counteracted by silybin. Oral administration of silybin protects against iron-induced hepatic toxicity in vivo. This effect seems to be caused by the prominent antioxidant activity of this compound.     

Interruption of a transforming growth factor α autocrine loop in Caco-2 cells by antisense oligodeoxynucleotides

We have previously shown that Caco-2 cell proliferation is driven by basolateral membrane epidermal growth factor receptors. The aim of this study was to investigate whether autocrine production of transforming growth factor α (TGF-α) activates these receptors and stimulates proliferation using antisense oligodeoxynucleotides. Caco-2 cells grown on microporous membranes or Jurkat cells were exposed to conventional or 5′ cholesterol-modified oligodeoxynucleotides synthesized with random, antisense, or missense base sequences. Indices of proliferation were measured, including [³H]thymidine or [³H]uridine uptake for studies of short-term stimulation and the methylthiotetrazole assay as an index of cell number increase over longer periods. Secretion of TGF-α by cells was detected using a soft agar bioassay. Incubation with antisense oligodeoxynucleotides inhibited TGF-α secretion compared with controls. Random and missense oligodeoxynucleotides had no effect on proliferation. The TGF-α antisense oligodeoxynucleotides markedly inhibited proliferation, an effect that was abolished by adding TGF-α to the medium. Oligonucleotides had no effect on Jurkat cells, a lymphocytic cell line lacking epidermal growth factor receptors. Cholesterol-modified oligodeoxynucleotides were more effective and specific than unmodified oligodeoxynucleotides. Caco-2 cell proliferation is driven by autocrine stimulation of epidermal growth factor receptors by TGF-α. This mechanism may be effectively inhibited by antisense oligodeoxynucleotides, particularly those modified by the 5′ attachment of cholesterol.     

Regulation of protein secretion into bile: Studies in mice with a disrupted mdr2 p-glycoprotein gene

Protein is secreted into bile via several independent pathways. The aim of this study was to investigate whether these pathways are influenced by secretion of biliary lipid. Protein secretion and biliary lipid output were studied in wildtype mice (+/+), heterozygotes (+/−), and homozygotes (−/−) for mdr2 gene disruption. Biliary lipid and protein output were varied by infusion with taurocholate (TC) and tauroursodeoxycholate (TUDC). Exocytosis and transcytosis were unaltered in (−/−) mice. Infusion with TC strongly induced secretion of alkaline phosphatase in (−/−) mice but had little effect in (+/−) and (+/+) mice. Infusion with TUDC had little effect on alkaline phosphatase output. In contrast, both TUDC and TC strongly stimulated secretion of aminopeptidase N and lysosomal enzymes in (+/+) mice but had no effect in (−/−) animals. Aminopeptidase N secretion correlated with phospholipid output, but only at high flux. At low flux, aminopeptidase N was secreted independently from both phospholipid and bile salts. The canalicular membrane enzymes alkaline phosphatase and aminopeptidase N are secreted via separate pathways. Part of alkaline phosphatase output is controlled by bile salt hydrophobicity, whereas at high lipid flux, aminopeptidase N secretion seems to be coupled to phospholipid output. Lysosomal enzymes follow the latter pathway.     

Platelet-activating factor acetylhydrolases in Caco-2 cells and epithelium of normal and ulcerative colitis patients

Platelet-activating factor (PAF) is a potent inflammatory mediator implicated in the pathogenesis of inflammatory bowel disease and necrotizing enterocolitis. Metabolism by platelet-activating factor acetylhydrolase (PAF-AH) is the major pathway for platelet-activating factor degradation. The aim of this study was to investigate the possible role of intestinal epithelium as a source of PAF-AH. Intracellular and secreted PAF-AHs were characterized in human colonic epithelial cells isolated from histologically normal mucosa and inflamed mucosa from patients with ulcerative colitis and in the human intestinal epithelial cell line Caco-2 by measuring the metabolism of [³H]-PAF to [³H]lysoPAF. Human colonic epithelial cells and Caco-2 cells synthesize and secrete PAF-AH as shown by in vitro hydrolysis of [³H]PAF to [³H]-lysoPAF in cell lysates and conditioned media. Both intracellular and secreted PAF-AHs are calcium-independent and substrate-specific for phospholipids similar to PAF. Epithelial cells from involved areas of resections for ulcerative colitis had increased levels of secreted PAF-AH and decreased levels of intracellular PAF-AH compared with epithelial cells from histologically normal areas. Human colonic epithelial cells and Caco-2 cells produce intracellular and secreted PAF-AHs, which are distinct proteins. This is the first demonstration of PAF-AH production by epithelial cells.     

Medical costs in community subjects with irritable bowel syndrome

Costs of management of irritable bowel syndrome (IBS) are unknown. The direct medical charges in community subjects with IBS were estimated. An age- and sex-stratified random sample of residents of Olmsted County, Minnesota, ranging in age from 20 to 95 years, was mailed a valid self-report questionnaire. Subjects were categorized as having IBS, having some symptoms but inadequate criteria for IBS, and controls. All charges (in 1992 U.S. dollars) for health services rendered in the year before completing the survey were obtained (except outpatient medications). A total of 88% of subjects with IBS, 86% of subjects with some symptoms of IBS, and 83% of controls incurred direct medical charges during the study year. The odds of incurring charges were 1.6 times greater in subjects with IBS relative to those without symptoms (P < 0.01) adjusting for age, sex, education, marital status, and employment. Overall median charges incurred by subjects with IBS were $742 compared with $429 for controls and $614 for subjects with some symptoms. Among those subjects with nonzero charges, there were significant positive associations with age, higher education, and symptom groups (all P < 0.01) but not sex. The economic impact of IBS is significant. A better understanding of the determinants of these costs is needed so that cost-saving strategies can be implemented.     

Bacterial translocation to mesenteric lymph nodes is increased in cirrhotic rats with ascites

Cirrhotic patients are predisposed to develop spontaneous bacteremias and/or peritonitis, mainly caused by enteric bacteria. The aim of this study was to investigate if bacterial translocation, which is the passage of bacteria from the intestinal lumen to regional lymph nodes and/or the systemic circulation, is increased in a rat model of cirrhosis. Rats were studied after 12–16 weeks of CCl₄ inhalation, when samples of mesenteric lymph nodes, blood, liver, and spleen for standard bacteriologic cultures and a fragment of colon and liver for histology were obtained. Immunostaining of the cecum was performed using a polyclonal anti-Escherichia coli antibody. A significantly greater proportion of rats with cirrhosis and ascites (5 of 9; 56%) had positive mesenteric lymph node cultures compared with cirrhotics without ascites (0 of 9) and normal controls (0 of 12) (P < 0.01). In one cirrhotic rat, E. coli was isolated from both mesenteric lymph nodes and ascites. Rats with cirrhosis and ascites had significantly greater cecal submucosal edema and inflammation than rats with no ascites and controls. Immunoreactivity with E. coli was present in the cecal wall in 3 of 5 animals with E. coli translocation to mesenteric lymph nodes. In cirrhotic rats, bacterial translocation is increased after the development of ascites and may be a major factor in the development of spontaneous infections in cirrhosis.     

Decreased activity of intestinal and urinary intrinsic factor in Gräsbeck-Imerslund disease

The pathogenesis of inherited intestinal cobalamin malabsorption (Gräsbeck-Imerslund disease) remains unknown. The authors studied whether the disease corresponds to a defective expression and/or function of the intrinsic factor-cobalamin receptor in the ileum. Intrinsic factor-cobalamin receptor activity was measured using radioisotope assay and gel-filtration exclusion chromatography in ileal biopsy specimens and urine concentrates from 4 patients with Gräsbeck-Imerslund disease and 5 controls. Receptor activity was 164 ± 13 fmol/mg of protein in control biopsy specimens and <2.6 fmol/mg protein in specimens from patients. The association constant was estimated to be 3.8 ± 0.4 (nmol/L)⁻¹ in controls. A dramatic decrease in receptor activity was also observed in urine concentrate from patients with an association constant of 1.9 and 3.3 (nmol/L)⁻¹. Isoelectrofocusing of the cross-linked intrinsic factor-cobalamin receptor complex showed an isoelectric point at 4.8 in a patient as well as in control samples. It is concluded that Gräsbeck-Imerslund disease is related to decreased intrinsic factor-receptor activity in intestinal mucosa; the receptor assay in urine can be helpful for diagnosis.