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Gene targeting in embryonic stem cells has allowed the creation of several new mouse strains carrying mutations in the murine homologs of human tumor suppressor genes. The phenotypes of these mutant strains are reviewed. In addition, recent experiments utilizing the ApcMin and p53 mutant animals to address specific mechanisms of carcinogenesis are discussed.
BACKGROUND & AIMS: Familial adenomatous polyposis because of germline mutation of the adenomatous polyposis coli gene is characterized by development of colorectal adenomas and, ultimately, colorectal cancer. The usefulness of colorectal mucosal compounds to predict the effect on adenoma development of primary chemoprevention with the nonsteroidal anti-inflammatory drug sulindac was evaluated. METHODS: A randomized, double-blind, placebo-controlled study of 41 subjects genotypically affected with familial adenomatous polyposis but phenotypically unaffected was conducted. Patients received either sulindac or placebo for 48 months, and development of new adenomas was evaluated. The levels of 5 prostanoids, ornithine decarboxylase, and polyamines were measured serially in normal-appearing rectal mucosa. RESULTS: There were no statistically significant differences between treatment groups in baseline levels of prostanoids, ornithine decarboxylase, or polyamines. At conclusion of the study, 4 of 5 prostaglandin levels were statistically significantly lower in the sulindac group than in the placebo group. Among the subset of patients taking sulindac, 3 of 5 prostaglandin levels were statistically significantly lower in patients who were polyp free than in those who developed polyps. By contrast, there were no statistically significant differences in ornithine decarboxylase or polyamines between treatment groups or in those on sulindac who were polyp free compared with those who developed polyps. CONCLUSIONS: Colorectal mucosal prostaglandin levels, but not ornithine decarboxylase or polyamines, may be valuable biomarkers to assess appropriate drug dosage and medication compliance in patients undergoing primary chemoprevention therapy with sulindac. Reduction of mucosal prostaglandin levels may be necessary to achieve chemopreventive benefit from this agent.
INTRODUCTION: It is uncertain whether patients with duodenal adenomas without familial adenomatous polyposis (FAP) are at greater risk for small bowel neoplasia. We therefore conducted a study to determine the frequency of small bowel polyps in patients with non-papillary duodenal adenomas using capsule endoscopy for small bowel examination. PATIENTS AND METHODS: 14 patients (8 women, 6 men; mean age 67 +/- 10 years; range: 49 - 77 years) with non-papillary duodenal adenomas without FAP were included. All patients underwent wireless capsule endoscopy. The results were compared with an age- and sex-matched cohort of patients undergoing capsule endoscopy for suspected small bowel disease. RESULTS: Overall, 15 polyps ranging between 1 and 8 mm in diameter were detected in eight patients of the study group, whereas no polyps could be identified in the control group. Natural excretion of the capsule within 24 hours was always reported and no complications were reported by any of the patients. Other pathological findings were multiple angiodysplasias in two patients of the study group. In the control group capsule endoscopy detected angiodysplasias in 5 patients with the indication obscure gastrointestinal bleeding, and inflammatory lesions in 2 patients with suspected Crohn's disease. CONCLUSIONS: Based on the results of this prospective study, the frequency of small bowel polyps in patients with duodenal adenomas without familial adenomatous polyposis appears to be increased compared with a control group undergoing capsule endoscopy for other reasons. In none of the patients was the management altered. Follow-up data of these patients will be needed.
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We have used a computer-driven scanning and image-processing system to identify a panel of 30 cDNA clones whose pattern of expression in individual biopsy specimens distinguishes the flat, normal-appearing colonic mucosa of patients in two genetic groups at high risk for development of colorectal cancer from that of normal colonic mucosa in low-risk individuals. The two high-risk groups, familial adenomatous polyposis and hereditary nonpolyposis colon cancer, are indistinguishable based on the pattern of expression of the 30 selected clones. This suggests that the extensive pleiotropic effects of the inherited loci, which may play an important role in the mechanism of increased risk and early onset of the disease, are similar in these populations.
Thymidine kinase (TK) activity of polyp tissue from patients with familial adenomatous polyposis (FAP) was measured and compared with that of non-tumorous colon, sporadic polyp and colorectal carcinoma tissues. Total TK activity in colonic carcinoma was 3-fold that of non-tumorous colon; its increase seems attributable mainly to increased activity of cytosolic TK isozyme activity. By using DEAE-cellulose column chromatography, the colorectal TK isozymes were separated into two types, i.e. two isozymes, referred to as the fetal (predominantly cytosolic) and adult (predominantly mitochondrial) types. However, FAP polyp samples from 15 patients showed an average elevation of only 1.8-fold over non-tumorous region of colon. Examined individually, only 5 of the 15 FAP samples showed significant elevations in total TK activity. Furthermore, TK isozyme analysis revealed variable patterns of the cytosolic isozyme activity, which was elevated in some cases (8/15) and remained low in others. Thus FAP polyps seem to be a heterogeneous population with respect to DNA replicative activity, and cytosolic TK isozyme activity may constitute a biochemical marker for the subsequent development of colorectal carcinoma in FAP.
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Restorative proctocolectomy with ileal pouch anal anastomosis has become the most commonly used procedure for elective treatment of patients with mucosal ulcerative colitis and familial adenomatous polyposis. Since its original description, the procedure has been modified in an attempt to obtain optimal functional results with low morbidity and mortality, and yet provide a cure for the disease. These modifications of the technique are discussed in this review, limited to the current points of controversy. We reviewed the current literature describing restorative proctocolectomy with ileal pouch anal anastomosis. The current "hot topics" for debate are transanal mucosectomy with hand-sewn anastomosis versus the double-stapled technique, the use of diverting ileostomy, indeterminate colitis, the role of laparoscopy, and indications for pouch surgery in the elderly. Longer follow-up of patients and increased knowledge and experience with pouch surgery, coupled with active prospective evaluation of the procedure are required to settle these issues. Patients must be fully informed to understand inherent risks of each choice.
BACKGROUND: Ileostomy carcinoma after colectomy for ulcerative colitis and familial adenomatous polyposis is rare. METHODS: Forty-three case reports from the literature and a case of ours are reviewed. RESULTS: The risk of malignancy following ileostomy formation appears to be increased compared to the very low incidence of primary small bowel carcinoma. Chronic physical or chemical irritation of the stoma may predispose the ileal mucosa to colonic metaplasia with subsequent adenoma formation, dysplasia and invasive malignant change. This is particularly so where ileostomies are fashioned for familial adenomatous polyposis and ulcerative colitis. CONCLUSION: Routine surveillance of patients who have had an ileostomy for 15 years or longer may lead to earlier detection of this complication.
OBJECTIVES: At present, surveillance of premalignant small bowel polyps in hereditary polyposis syndromes has a number of limitations. Capsule endoscopy (CE) is a promising new method to endoscopically assess the entire length of the small bowel. METHODS: We prospectively examined 40 patients with hereditary polyposis syndromes (29 familial adenomatous polyposis (FAP), 11 Peutz-Jeghers syndrome (PJS)). Results were compared with push-enteroscopy (PE) results in FAP and with esophagogastroduodenoscopy, PE, (MR)-enteroclysis, and surgical specimen in PJS patients. RESULTS: A total of 76% of the patients with FAP with duodenal adenomas (n = 21) had additional adenomas in the proximal jejunum that could be detected by CE and PE. Moreover, 24% of these FAP patients had further polyps in the distal jejunum or ileum that could only be detected by CE. In contrast, in FAP patients without duodenal polyps (n = 8), jejunal or ileal polyps occurred rarely (12%). CE detected polyps in 10 of 11 patients with PJS, a rate superior to all other reference procedures employed. Importantly, the findings of CE had immediate impact on further clinical management in all PJS patients. CONCLUSIONS: Our results suggest that CE may be of clinical value in selected patients with FAP, whereas in PJS, CE could be used as first line surveillance procedure.
Like calcium, vitamin D may protect against colorectal neoplasia as it reduces epithelial cell proliferation and induces differentiation. Although its therapeutic use is limited by its effects on calcium metabolism, analogues such as calcipotriol produce little hypercalcaemia. Stathmokinetic and immunohistochemical techniques were used to study the effect of 1,25 (OH)2 D3 and its analogues on cell proliferation in human rectal mucosa and a colon cancer cell line. Paired sigmoidoscopic biopsy specimens were obtained from 17 control patients and five patients with familial adenomatous polyposis. Explants were established in organ culture, with or without the addition of vitamin D. Proliferation was assessed using (1) metaphase arrest to determine the crypt cell production rate (CCPR) and (2) Ki-67 monoclonal antibody directed against an antigen present in proliferating cells. 1,25 (OH)2 D3 in concentrations of 1 microM-100 pM (10(-6)-10(-10) M) reduced the CCPR (cells/crypt/hour) from 4.74 to 2.15-2.67 (p < 0.001), and the Ki-67 labelling index from 7.28-3.74 (p < 0.01). Likewise, vitamin D2, 10 nM (10(-8) M) reduced the CCPR from 4.74-2.74 (p < 0.05) and calcipotriol from 4.86-2.38 (p < 0.05). In familial adenomatous polyposis patients 1,25 (OH)2 D3 100 pM (10(-10) M) halved the CCPR from 8.75-4.22. Calcipotriol (10(-5) M to 10(-9) M) produced a clearcut dose response inhibition of HT-29 cell growth. Thus, vitamin D and its metabolites inhibit proliferation in normal and premalignant rectal epithelium and suppress growth in a colorectal cancer cell line.
Pouchitis may complicate the construction of an ileal pouch after colectomy for ulcerative colitis (UC) but not familial adenomatous polyposis (FAP). To examine whether differences in eicosanoid metabolism might explain why pouchitis is largely confined to UC patients, this study compared arachidonic acid stimulated release of immunoreactive leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) from macroscopically uninflamed pouch mucosal biopsy specimens incubated in vitro from patients with UC and FAP. The study also compared eicosanoid release from inflamed and uninflamed pouches in patients with UC. In uninflamed pouches, median LTB4 release was nearly twice as high in UC as in FAP (p = 0.001), but there was no significant difference in PGE2 production. In UC, stimulated eicosanoid release from uninflamed functioning pouch mucosa was not significantly different from that from either ileostomy or defunctioned pouch mucosa. LTB4 and PGE2 release were significantly greater from inflamed than uninflamed pouch mucosa in UC (p = 0.001 and 0.01, respectively). Leukotriene synthesis inhibition or receptor antagonism, or both merit therapeutic evaluation in pouchitis. Increased release of LTB4 from endoscopically normal pouch mucosa suggests increased 5-lipoxygenase activity in patients with UC and could contribute to their predisposition to pouchitis.
Previous work has shown abnormalities in the proliferative activity of the colorectal mucosa in familial adenomatous polyposis (FAP). Some doubts remain about the validity of these findings because of difficulties in excluding adenomatous crypts, particularly in methods using tritiated thymidine, bromodeoxyuridine, and ornithine decarboxylase. The proliferative activity of the epithelium in colonic resections from 20 FAP patients was compared with that of age, sex, and site matched controls using a new monoclonal antibody MIB1 to assay the expression of Ki-67 antigen in routinely processed tissue. The labelling indices were very similar in the polyposis and control cases (25.5 (1.4)% and 26.7 (1.7)% respectively) but analysis of the distribution of labelled cells showed a significant shift of the proliferative compartment towards the luminal surface in the FAP group. Specifically, the labelling index was lower in the basal fifth of the polyposis crypts and higher in the two fifths at the luminal surface. These results show that analysis of proliferative activity in FAP is now achievable in routine histological material and indicate deregulation of proliferative control in the FAP colonic crypt. This may form a useful diagnostic adjunct to standard clinical and molecular genetic techniques, particularly in view of the current interest in dietary and pharmacological intervention in sporadic colorectal carcinoma.
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A case of gastric polyposis caused by multiple carcinoids with concurrent gastric carcinoma is reported in a 70 year old woman with severe atrophic gastritis and intestinal metaplasia. On microscopic examination, the carcinoids and gastric carcinoma arose separately thus representing "double primaries". Long-standing hypergastrinaemia probably plays a causative role in the development of carcinoma and carcinoids. Carcinoid tumours, although of low malignant potential, may be important as indicators of other unrelated high risk malignancies. Patients with carcinoids should be followed closely, especially as the incidence of these tumours seems to be on the increase.
The Adenomatous Polyposis coli (APC) gene is mutated or lost in most colon cancers, and the APC protein has emerged as a multifunctional protein that is not only involved in the Wnt-regulated degradation of -catenin, but also regulates cytoskeletal proteins and thus plays a role in cell migration, cell adhesion, and mitosis. The gut epithelium is uniquely dependent on an intricate balance between a number of fundamental cellular processes including migration, differentiation, adhesion, apoptosis, and mitosis. In this review, I discuss the molecular mechanisms that govern the various functions of APC and their relationship to the role of APC in colon cancer.
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OBJECTIVE: To investigate the expressions and clinical implications of kruppel-like factor 6(KLF-6) and APC in human colorectal carcinoma. METHODS: The expressions of KLF-6 and APC in tumor and normal tissues from 32 patients with colorectal carcinoma were investigated by RT-PCR and immunohistochemical technique. RESULTS: The expression rates of KLF-6 and APC mRNA were 37.5% and 34.3% in tumor tissue, 96.9% and 93.8% respectively in normal tissues (both P< 0.05). The expression rates of KLF-6 and APC protein were 28.1% and 25.0% in colorectal carcinomas, 81.3% and 84.43% respectively in normal tissues (both P< 0.05). There was a significant correlation between the expressions of KLF-6 and APC in colorectal carcinomas (P < 0.05). The expressions of KLF-6 and APC were significantly correlated with tumor differentiation, depth of infiltration, lymph node metastasis and clinical stage (P< 0.05). CONCLUSION: Down-regulations of KLF-6 and APC might play an important role in the carcinogenesis, development, metastasis of human colorectal carcinoma.