Histology of aberrant crypt foci in the human colon

Dietary Xenobiotics Derived from Food Processing: Association with Fecal Mutagenicity and Gut Mucosal Damage

Whereas the mechanisms underlying the association of toxic dietary xenobiotics and cancer risk are not well established, it is plausible that dietary pattern may affect the colon environment by enhancing or reducing exposure to mutagens. This work aimed to investigate the association between xenobiotics intake and different stages of intestinal mucosal damage and colorectal cancer (CRC) screening and examine whether these associations may be mediated by altered intestinal mutagenicity. This was a case control study with 37 control subjects, 49 patients diagnosed with intestinal polyps, and 7 diagnosed with CRC. Lifestyle, dietary, and clinical information was registered after colonoscopy. For xenobiotics intake estimation the European Prospective Investigation into Cancer (EPIC) and the Computerized Heterocyclic Amines Resource for Research in Epidemiology of Disease (CHARRED) databases were used. The mutagenicity of fecal supernatants was assayed by the Ames test and light microscopy was used for the presence of aberrant crypt formation. Among all the potential carcinogens studied, the polyp group showed higher intakes of ethanol and dibenzo (a) anthracene (DiB(a)A). Besides, intakes between 0.75 and 1.29 µg/d of total polycyclic aromatic hydrocarbons (PAHs) were related with a higher risk of belonging to the polyp group. On the contrary, an intake of wholegrain cereals greater than 50 g/d was associated with a reduction in the relative risk of belonging to the polyp group. Heterocyclic amines (HAs) such as 2-amino-1-methyl-6-phenylimidazo (4,5,b) pyridine (PhIP) were associated with an increased level of mutagenicity in polyps. This study is of great interest for the identification of possible therapeutic targets for the early prevention of colon cancer through diet.

Deep learning techniques for detecting preneoplastic and neoplastic lesions in human colorectal histological images

Trained pathologists base colorectal cancer identification on the visual interpretation of microscope images. However, image labeling is not always straightforward and this repetitive task is prone to mistakes due to human distraction. Significant efforts are underway to develop informative tools to assist pathologists and decrease the burden and frequency of errors. The present study proposes a deep learning approach to recognize four different stages of cancerous tissue development, including normal mucosa, early preneoplastic lesion, adenoma and cancer. A dataset of human colon tissue images collected and labeled over a 10-year period by a team of pathologists was partitioned into three sets. These were used to train, validate and test the neural network, comprising several convolutional and a few linear layers. The approach used in the present study is 'direct'; it labels raw images and bypasses the segmentation step. An overall accuracy of >95% was achieved, with the majority of mislabeling referring to a near category. Tests on an external dataset with a different resolution yielded accuracies >80%. The present study demonstrated that the neural network, when properly trained, can provide fast, accurate and reproducible labeling for colon cancer images, with the potential to significantly improve the quality and speed of medical diagnoses.

Notabi M, El-Houri RB, Pipó-Ollé E, Christensen Arnspang E, Christensen LP. Dietary Polyacetylenic Oxylipins Falcarinol and Falcarindiol Prevent Inflammation and Colorectal Neoplastic Transformation: A Mechanistic and Dose-Response Study in A Rat Model

Falcarinol (FaOH) and falcarindiol (FaDOH) are cytotoxic and anti-inflammatory polyacetylenic oxylipins, which are commonly found in the carrot family (Apiaceae). FaOH and FaDOH have previously demonstrated a chemopreventive effect on precursor lesions of colorectal cancer (CRC) in azoxymethane (AOM)-induced rats. The purpose of the present study was to elucidate possible mechanisms of action for the preventive effect of FaOH and FaDOH on colorectal precancerous lesions and to determine how this effect was dependent on dose. Gene expression studies performed by RT-qPCR of selected cancer biomarkers in tissue from biopsies of neoplastic tissue revealed that FaOH and FaDOH downregulated NF-κβ and its downstream inflammatory markers TNFα, IL-6, and COX-2. The dose-dependent anti-neoplastic effect of FaOH and FaDOH in AOM-induced rats was investigated in groups of 20 rats receiving a standard rat diet (SRD) supplemented with 0.16, 0.48, 1.4, 7 or 35 µg FaOH and FaDOH g⁻¹ feed in the ratio 1:1 and 20 rats were controls receiving only SRD. Analysis of aberrant crypt foci (ACF) showed that the average number of small ACF (<7 crypts) and large ACF (>7 crypts) decreased with increasing dose of FaOH and FaDOH and that this inhibitory effect on early neoplastic formation of ACF was dose-dependent, which was also the case for the total number of macroscopic neoplasms. The CRC protective effects of apiaceous vegetables are mainly due to the inhibitory effect of FaOH and FaDOH on NF-κB and its downstream inflammatory markers, especially COX-2.

Mapping insoluble indole metabolites in the gastrointestinal environment of a murine colorectal cancer model using desorption/ionisation on porous silicon imaging

Indole derivatives are a structurally diverse group of compounds found in food, toxins, medicines, and produced by commensal microbiota. On contact with acidic stomach conditions, indoles undergo condensation to generate metabolites that vary in solubility, activity and toxicity as they move through the gut. Here, using halogenated ions, we map promising chemo-preventative indoles, i) 6-bromoisatin (6Br), ii) the mixed indole natural extract (NE) 6Br is found in, and iii) the highly insoluble metabolites formed in vivo using desorption/ionisation on porous silicon-mass spectrometry imaging (DIOS-MSI). The functionalised porous silicon architecture allowed insoluble metabolites to be detected that would otherwise evade most analytical platforms, providing direct evidence for identifying the therapeutic component, 6Br, from the mixed indole NE. As a therapeutic lead, 0.025 mg/g 6Br acts as a chemo-preventative compound in a 12 week genotoxic mouse model; at this dose 6Br significantly reduces epithelial cell proliferation, tumour precursors (aberrant crypt foci; ACF); and tumour numbers while having minimal effects on liver, blood biochemistry and weight parameters compared to controls. The same could not be said for the NE where 6Br originates, which significantly increased liver damage markers. DIOS-MSI revealed a large range of previously unknown insoluble metabolites that could contribute to reduced efficacy and increased toxicity.

Proximal Aberrant Crypt Foci Associate with Synchronous Neoplasia and Are Primed for Neoplastic Progression

Aberrant crypt foci (ACF) are the earliest morphologically identifiable lesion found within the human colon. Despite their relatively high frequency in the distal colon, few studies have examined the molecular characteristics of ACF within the proximal colon. In the following study, clinical participants (n = 184) were screened for ACF using high-definition chromoendoscopy with contrast dye-spray. Following pathologic confirmation, ACF biopsies were subjected to laser capture microdissection (LCM), and epithelial cells were evaluated for somatic mutations with a customized colorectal cancer mutation panel using DNA-mass spectrometry. Samples were further characterized for microsatellite instability (MSI). Logistic models were used to associate proximal ACF with synchronous (detected during the same procedure) neoplasia. Thirty-nine percent of participants had at least one histologically confirmed proximal ACF. Individuals with a proximal ACF were significantly more likely to present with a synchronous neoplasm (P = 0.001), and specifically, a proximal, tubular, or tubulovillous adenoma (multivariable OR = 2.69; 95% confidence interval, 1.12-6.47; P = 0.027). Proximal ACF were more likely to be dysplastic (52%) compared with distal ACF (13%; P < 0.0001). Somatic mutations to APC, BRAF, KRAS, NRAS, and ERBB2 were detected in 37% of proximal ACF. Hyperplastic ACF were more often MSI-high, but there were no differences in MSI status observed by colonic location. In summary, ACF are identified in the proximal colons of approximately 40% of individuals undergoing chromoendoscopy and more often in patients with synchronous proximal adenomas.Implications: This study provides the most complete set of data, to date, that ACF represent the earliest step in the adenoma-carcinoma sequence but remain below the detection limit of conventional endoscopy.Visual Overview: http//mcr.accrjournals.org/content/molcanres/16/3/486/F1.large.jpg Mol Cancer Res; 16(3); 486-95. ©2017 AACR.

Rapidly cycling Lgr5+ stem cells are exquisitely sensitive to extrinsic dietary factors that modulate colon cancer risk

The majority of colon tumors are driven by aberrant Wnt signaling in intestinal stem cells, which mediates an efficient route toward initiating intestinal cancer. Natural lipophilic polyphenols and long-chain polyunsaturated fatty acids (PUFAs) generally suppress Wnt- and NF-κB- (nuclear factor-κ light-chain enhancer of activated B-cell) related pathways. However, the effects of these extrinsic agents on colonic leucine-rich repeat-containing G-protein-coupled receptor 5-positive (Lgr5⁺) stem cells, the cells of origin of colon cancer, have not been documented to date. Therefore, we examined the effect of n-3 PUFA and polyphenol (curcumin) combination on Lgr5⁺ stem cells during tumor initiation and progression in the colon compared with an n-6 PUFA-enriched control diet. Lgr5-EGFP-IRES-^creERT2 knock-in mice were fed diets containing n-6 PUFA (control), n-3 PUFA, n-6 PUFA+curcumin or n-3 PUFA+curcumin for 3 weeks, followed by 6 azoxymethane (AOM) injections, and terminated 17 weeks after the last injection. To further elucidate the effects of the dietary bioactives at the tumor initiation stage, Lgr5⁺ stem cells were also assessed at 12 and 24 h post AOM injection. Only n-3 PUFA+curcumin feeding reduced nuclear β-catenin in aberrant crypt foci (by threefold) compared with control at the progression time point. n-3 PUFA+curcumin synergistically increased targeted apoptosis in DNA-damaged Lgr5⁺ stem cells by 4.5-fold compared with control at 12 h and maximally reduced damaged Lgr5⁺ stem cells at 24 h, down to the level observed in saline-treated mice. Finally, RNAseq analysis indicated that p53 signaling in Lgr5⁺ stem cells from mice exposed to AOM was uniquely upregulated only following n-3 PUFA+curcumin cotreatment. These novel findings demonstrate that Lgr5⁺ stem cells are uniquely responsive to external dietary cues following the induction of DNA damage, providing a therapeutic strategy for eliminating damaged Lgr5⁺ stem cells to reduce colon cancer initiation.

Chromoendoscopy with a Standard-Resolution Colonoscope for Evaluation of Rectal Aberrant Crypt Foci

Colorectal cancer (CRC) is the second most common cause of death worldwide. According to the theory by Vogelstein, colorectal carcinogenesis involves a series of successive changes in the normal colonic mucosa, starting with excessive proliferation and focal disorders of intestinal crypts, followed by adenoma and its subsequent malignant transformation. The first identifiable changes in CRC carcinogenesis are aberrant crypt foci (ACF). ACF are invisible during routine colonoscopy yet are well identifiable in chromoendoscopy using methylene blue or indigo carmine. High-resolution colonoscopes are used for assessment of ACF. The aim of the present study was to evaluate the usefulness of standard-resolution colonoscopy for identification of rectal ACF. The following parameters were evaluated: duration of chromoendoscopy of a given rectal segment, type of ACF, sensitivity and specificity of endoscopy combined with histopathological evaluation. The mean duration of colonoscopy and chromoendoscopy was 26.8 min. In the study population, typical ACF were found in 73 patients (p = 0.489), hyperplastic ACF in 49 (p = 0.328), and dysplastic ACF in 16 patients (p = 0.107). Mixed ACF were observed in 11 individuals (p = 0.073). The sensitivity of the method was found to be 0.96 whereas its specificity 0.99. Identification of rectal ACF using standard-resolution colonoscopy combined with rectal mucosa staining with 0.25% methylene blue is characterised by high sensitivity and specificity.

Wheat Type (Class) Influences Development and Regression of Colon Cancer Risk Markers in Rats

We previously found red wheat more effective than white wheat in reducing colon cancer risk in rats when fed during initiation and postinitiation stages. Here we examine the effect of wheat on colon cancer risk in early and late postinitiation stages in carcinogen-treated rats. Four groups were fed a basal diet, 1 group a red wheat diet, and 1 group a white wheat diet. After 6 wk, 1 basal, the red and white groups were killed (early postinitiation stage). Of the remaining basal groups, 1 continued on the basal diet, 1 was switched to red and another to white wheat for 8 more wk (late postinitiation stage). Red and white wheat significantly reduced morphological [aberrant crypt foci (ACF)] and biochemical (β-catenin accumulated crypts) markers in both early and late postinitiation stages. Both wheat diets reduced dysplasia markers (sialomucin-expressing ACF and mucin depleted foci), compared to the basal diet, during the late postinitiation stage, but red wheat more so. Only red wheat significantly reduced the number of metallothionein-positive crypts, a stem cell mutation marker, in both stages. Overall, red wheat flour reduced risk markers more than white wheat flour, and this was more pronounced in the late post-initiation stage.

Colon preneoplastic lesions in animal models

The animal model is a powerful and fundamental tool in the field of biochemical research including toxicology, carcinogenesis, cancer therapeutics and prevention. In the carcinogenesis animal model system, numerous examples of preneoplastic lesions have been isolated and investigated from various perspectives. This may indicate that several options of endpoints to evaluate carcinogenesis effect or therapeutic outcome are presently available; however, classification of preneoplastic lesions has become complicated. For instance, these lesions include aberrant crypt foci (ACF), dysplastic ACF, flat ACF, β-catenin accumulated crypts, and mucin-depleted foci. These lesions have been induced by commonly used chemical carcinogens such as azoxymethane (AOM), 1,2-dimethylhydrazine (DMH), methylnitrosourea (MUN), or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Investigators can choose any procedures or methods to examine colonic preneoplastic lesions according to their interests and the objectives of their experiments. Based on topographical, histopathological, and biological features of colon cancer preneoplastic lesions in the animal model, we summarize and discuss the character and implications of these lesions.

Th inducing POZ-Kruppel Factor (ThPOK) is a key regulator of the immune response since the early steps of colorectal carcinogenesis

We purposed to evaluate the role of Th inducing POZ-Kruppel Factor (ThPOK), a transcriptional regulator of T cell fate, in tumour-induced immune system plasticity in colorectal carcinogenesis. The amounts of CD4+, CD8+ and CD56+ and ThPOK+ cells infiltrate in normal colorectal mucosa (NM), in dysplastic aberrant crypt foci (microadenomas, MA), the earliest detectable lesions in colorectal carcinogenesis, and in colorectal carcinomas (CRC), were measured, and the colocalization of ThPOK with the above-mentioned markers of immune cells was evaluated using confocal microscopy. Interestingly, ThPOK showed a prominent increase since MA. A strong colocalization of ThPOK with CD4 both in NM and in MA was observed, weaker in carcinomas. Surprisingly, there was a peak in the colocalization levels of ThPOK with CD8 in MA, which was evident, although to a lesser extent, in carcinomas, too. In conclusion, according to the data of the present study, ThPOK may be considered a central regulator of the earliest events in the immune system during colorectal cancer development, decreasing the immune response against cancer cells.

Loss of expression of DNA mismatch repair proteins in aberrant crypt foci identified in vivo by magnifying colonoscopy in subjects with hereditary nonpolyposic and sporadic colon rectal cancer

PURPOSE

The aims of this study are to characterize the frequency, density, and distribution of aberrant crypt foci (ACF) and its histological features and to determine the frequency of loss of expression of DNA mismatch repair (MMR) proteins of subjects with hereditary nonpolyposic colorectal cancer (HNPCC) and sporadic colon rectal cancer (CRC).

METHODS

Patients with HNPCC, first-degree relatives of subjects with HNPCC, sporadic CRC, and average risk subjects of sporadic CRC were included prospectively. Total colonoscopy with chromoendoscopy using methylene blue 0.5% and magnification in the right colon (cecum and 20 cm of the ascending colon) and in the left colon (rectum) was performed; loss of expression of MLH1 and MSH2 was evaluated by immunohistochemistry in confirmed ACF.

RESULTS

Fifty-two subjects were included. Thirty-eight of the 119 ACF detected by endoscopy were biopsied. In 14 of the 38 specimens (36.8%), ACF were confirmed by histology (Cohen's kappa, 0.44). In subjects with HNPCC, ACF were identified more frequently in the right segment of the colon than in the left (73.1% vs. 26%); in contrast, ACF predominated in the left segment of the colon (89.3% vs. 10.6%) in subjects with sporadic CRC. There was a loss of MLH1 expression in ACF in subjects with HNPCC.

CONCLUSIONS

In HNPCC, we found a greater density of ACF in the right colon, and in sporadic CRC, greater density in the left. ACF present loss in the expression of DNA MMR protein and can be used as an early marker in patients with a risk of HNPCC in whom carcinogenesis appears to be accelerated.

Probe-based confocal laser endomicroscopy evaluation of colon preneoplastic lesions, with particular attention to the aberrant crypt foci, and comparative assessment with histological features obtained by conventional endoscopy

The colorectal carcinoma represents one of the most common and aggressive malignancies, still characterized by an unacceptable mortality rate, mainly due to the high metastatic potential and to a late diagnosis. In the last years, the research community focused on the chance of improving the endoscopic screening to detect neoplastic lesions in a very early stage. Several studies proposed aberrant colonic crypt foci as the earliest recognizable step of transformation in colonic multiphase carcinogenesis. We previously demonstrated the clinical applicability and predictive power of probe-based confocal laser endoscopy (pCLE) in superficial colorectal neoplastic lesions and also characterized in vivo a case of dysplasia-associated lesional mass (DALM) in ulcerative colitis. Now, we aim to evaluate the accuracy of pCLE in the detection of ACF comparing in double-blind manner the microendoscopic and histopathological features resulting from colonic biopsy. By pCLE, we identified specific crypt architecture modifications associated with changes in cellular infiltration and vessels architecture, highlighting a good correspondence between pCLE features and histology.

Effects of Ficus carica paste on constipation induced by a high-protein feed and movement restriction in beagles

Constipation is one of the most common functional digestive complaints worldwide. We investigated the laxative effects of figs (Ficus carica L) in a beagle model of constipation induced by high protein diet and movement restriction. The experiments were consecutively conducted over 9 weeks divided into 3 periods of 3 weeks each. All 15 beagles were subjected to a non-treatment (control) period, a constipation induction period, and a fig paste treatment period. We administered fig paste (12 g/kg daily, by gavage) for 3 weeks following a 3-week period of constipation induction in dogs. Segmental colonic transit time (CTT) was measured by counting radiopaque markers (Kolomark) using a radiograph performed every 6 h after feeding Kolomark capsules, until capsules were no longer observed. Fig paste significantly increased fecal quantity in constipated dogs, and segmental CTT was also reduced following fig paste administration. There were no significant differences in feed intake, water intake, body weight, or blood test results, between the constipation and fig paste administration periods. Our results demonstrate that fig is an effective treatment for constipation in beagles. Specifically, stool weight increased and segmental CTT decreased. Fig pastes may be useful as a complementary medicine in humans suffering from chronic constipation.

Early lesion formation in colorectal carcinogenesis is associated with adiponectin status whereas neoplastic lesions are associated with diet and sex in C57BL/6J mice

Adiponectin is an antiinflammatory and insulin-sensitizing hormone that is decreased in obesity. Although controversial, it has been suggested that decreased adiponectin contributes to colorectal cancer risk in obesity. To further investigate the role of adiponectin in obesity-linked colorectal carcinogenesis, we used male and female adiponectin knockout (KO) and wild-type (Wt) C57BL/6J mice. Tumorigenesis was induced in all mice with the combined treatment of azoxymethane (AOM) and dextran sodium sulfate (DSS). Following AOM/DSS treatment, mice were fed a low-fat control (LFC), or high-fat lard (HFL) diet for 7 1/2 wk. KO mice developed fewer total lesions than Wt mice, males developed fewer lesions than females, and mice fed the HFL diet developed fewer lesions than those fed the LFC diet. Early lesion multiplicity was influenced by genotype, whereas advanced lesion development was influenced by sex and diet. Moreover, lesion types were differentially correlated with serum adipokines and colon gene expression of adiponectin receptors, insulin receptor, and toll-like receptor 4. These data suggest that in the AOM/DSS model of carcinogenesis, adiponectin functions to promote early lesion development whereas sex and diet are important regulators of advanced lesion development through pathways involved in inflammation and insulin signaling.

Low-dose dietary resveratrol has differential effects on colorectal tumorigenesis in adiponectin knockout and wild-type mice

Obesity is associated with a decrease in the antiinflammatory hormone, adiponectin, and increases in the circulating concentrations of multiple proinflammatory cytokines. These changes contribute to colon tumorigenesis. Resveratrol increases adiponectin production in adipocytes and attenuates the development of colon cancer. Thus, we hypothesized that adiponectin is an integral component of the mechanism by which resveratrol antagonizes colorectal tumorigenesis. To investigate this, we induced tumorigenesis in adiponectin knockout (KO) and wild-type (Wt) C57BL/6 mice through combined azoxymethane and dextran sodium sulfate treatment during which mice were fed a high-fat, lard-based diet, or the same diet containing 20 mg/kg resveratrol. After 14 wk on diet, Wt mice gained more weight and, on a percentage basis, had higher fat mass and lower lean mass than KO mice. Resveratrol tended to attenuate this response in male Wt mice. Resveratrol also tended to reduce aberrant crypt foci development and decrease circulating interleukin 6 and insulin concentrations in male but not female Wt mice. Taken together, resveratrol improved overall health of obese Wt but not KO mice as hypothesized with a differential sex response.

Light and moderate doses of ethanol in chemical carcinogenesis of the colon in rats

The aberrant crypt foci (ACF), cyclooxygenase 2 (COX-2), and the proliferating cell nuclear antigen (PCNA) are putative biomarkers for colon cancer. To study the association between light (1 g of ethanol/kg bw) and moderate (3 g of ethanol/kg bw) doses of ethanol with the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), Wistar rats were divided into 6 groups. The colon fragments were collected for histochemical and immunohistochemical analyses, and the liver samples were collected for oxidative stress analysis, with products of lipid peroxidation (malondialdehyde), antioxidant enzymes (glutathione), and vitamin E. The association of light and moderate doses of ethanol with MNNG did not present differences in the oxidative parameters. However, a reduction in vitamin E levels in the carcinogen groups was observed. The association induced a reduction of the COX-2 and PCNA expression. The number of ACF in the group that received a light dose of ethanol had lower rates, while the group that received a moderate dose had the highest rates compared to the control MNNG, demonstrating that the light dose of ethanol could have a protective effect, while the moderate dose could represent a risk during chemical carcinogenesis in rats.

Study of the antineoplastic action of Tabebuia avellanedae in carcinogenesis induced by azoxymethane in mice

PURPOSE: To study the antitumor action of Tabebuia avellanedae in experimentally induced colon carcinogenesis by azoxymethane in mice. METHODS: Fifty (n=50) mice were divided into five groups: in group I azoxymethane (AOM) was administered, in Group II - β-lapachone, in group III - vehicle (diluent) and in group IV - vehicle + AOM and finally in group V - β-lapachone + AOM. RESULTS: It was observed the presence of aberrant crypt foci in all animals of groups I and IV, 50% in group II and 90% in group V. CONCLUSION: The β-lapachone extracted from the Tabebuia avellanedae showed no protective effect of lesions induced by azoxymethane in colon of mice.

Altered expression of apoptosis biomarkers in human colorectal microadenomas

Human colorectal microadenomas are considered the earliest detectable premalignant lesions in the colon. They can be identified as aggregates of enlarged crypts with thicker epithelial linings and elongated luminal openings on the colonic mucosal surface after methylene blue staining and observation under a dissecting microscope. Multiple lines of evidence suggest that a central role in neoplastic development is played by the inhibition of apoptosis, followed by disruption of DNA repair. Understanding the early mechanisms of colorectal carcinogenesis may help develop new approaches of colorectal cancer prevention and treatment. The aim of the present study was to quantify poly-ADP ribose polymerase 1 (PARP-1)-positive cells and to evaluate apoptotic control mechanisms through Caspase-3 active and Bcl-2 protein expression in human microadenomas and in normal colorectal mucosa using immunofluorescence techniques coupled with confocal microscopy and immunoblot experiments. The mean percentage of PARP-1-positive epithelial cells was 3.0 +/- 0.37% (SD) and 15.67 +/- 0.40% in microadenoma and in normal mucosa, respectively. Proteins involved in programmed cell death were differently expressed in microadenoma and in normal mucosa. Indeed, by semiquantitative immunofluorescence analysis, confirmed by Western blot, microadenoma showed low levels of Caspase-3 active and high levels of Bcl-2 expression, whereas the opposite was true for normal colorectal mucosa [corrected]. In the stroma of normal colorectal mucosa, fibroblast-like cells and neutrophils were the cells that underwent apoptosis to a greater extent. In conclusion, malfunction of the control mechanisms of programmed cell death seems present in the early stages of colorectal cancer development.

Beta-catenin expression is altered in dysplastic and nondysplastic aberrant crypt foci of human colon

PURPOSE

Aberrant crypt foci (ACF) of the colon are possible precursors of adenoma and cancer. beta-catenin alterations are early events in human colorectal carcinogenesis. beta-catenin expression is altered in colorectal cancer, adenoma, and ACF with dysplasia. Here, we describe the expression of beta-catenin in ACF, especially nondysplastic ACF.

METHODS

Rectal chromoscopy with 4% indigo carmine was performed on 418 subjects and 146 biopsy specimens, including 10 dysplastic ACF, 106 nondysplastic ACF, and 30 normal colonic mucosal controls taken under endoscopy. The expression and subcellular distribution of beta-catenin were assessed by immunohistochemistry.

RESULTS

beta-catenin expression was altered in 1 of 30 (3.3%) normal mucosa, 30 of 106 (28.3%) nondysplastic ACF, and 10 of 10 (100%) dysplastic ACF (P<0.001). Notably, most cells with altered beta-catenin expression in nondysplastic ACF were limited to the bottom of the crypt, where stem cells are located.

CONCLUSIONS

Both dysplastic and nondysplastic ACF have altered beta-catenin expression and play a role in colon tumorigenesis.

Reliability and accuracy of the endoscopic appearance in the identification of aberrant crypt foci

BACKGROUND

Aberrant crypt foci (ACF) have emerged as a putative precursor to colorectal adenoma, with potential use as a biomarker of colorectal cancer. However, there are wide differences in ACF prevalence, dysplasia, and histologic confirmation rates across studies. These differences may, in part, be because of variability in identification of endoscopic criteria.

OBJECTIVE

To systematically evaluate the accuracy and reliability of various endoscopic criteria used to identify ACF when using magnification chromoendoscopy (MCE).

DESIGN

Images obtained via MCE were shown to participating endoscopists who diagnosed them as ACF or not and who assessed them for the endoscopic characteristics used to identify ACF in the literature.

MAIN OUTCOME MEASUREMENTS

The predictive ability of the endoscopic criteria (crypt number, staining, margin, crypt size, epithelial thickness, and lumen shape) for histologic confirmation of ACF, and their reliability across endoscopists. The accuracy of the examiners in identifying ACF that were histologically confirmed was also assessed.

RESULTS

The interrater agreement rate for all except one of the endoscopic criteria (crypt number) was low and did not improve with training. None of the criteria could significantly predict histologic confirmation of ACF. Despite training exercises, accuracy of endoscopists to correctly identify a histologically proven ACF remained low.

LIMITATIONS

Still images with x40 optical magnification were analyzed rather than real-time endoscopy. All ACF samples were hyperplastic; none were dysplastic.

CONCLUSIONS

No endoscopic criteria evaluated by our study predicted histologic confirmation of ACF. MCE had low accuracy and poor reliability.

Iron and exercise induced alterations in antioxidant status. Protection by dietary milk proteins

Lipid peroxidation stress induced by iron supplementation can contribute to the induction of gut lesions. Intensive sports lead to ischemia reperfusion, which increases free radical production. Athletes frequently use heavy iron supplementation, whose effects are unknown. On the other hand, milk proteins have in vitro antioxidant properties, which could counteract these potential side effects. The main aims of the study were: (1) to demonstrate the effects of combined exercise training (ET) and iron overload on antioxidant status; (2) to assess the protective properties of casein in vivo; (3) to study the mechanisms involved in an in vitro model. Antioxidant status was assessed by measuring the activity of antioxidant enzymes (superoxide dismutase (SOD); glutathione peroxidase (GSH-Px)), and on the onset of aberrant crypts (AC) in colon, which can be induced by lipid peroxidation. At day 30, all ET animals showed an increase in the activity of antioxidant enzymes, in iron concentration in colon mucosa and liver and in the number of AC compared to untrained rats. It was found that Casein's milk protein supplementation significantly reduced these parameters. Additional information on protective effect of casein was provided by measuring the extent of TBARS formation during iron/ascorbate-induced oxidation of liposomes. Free casein and casein bound to iron were found to significantly reduce iron-induced lipid peroxidation. The results of the overall study suggest that Iron supplementation during intensive sport training would decrease anti-oxidant status. Dietary milk protein supplementation could at least partly prevent occurrence of deleterious effects to tissue induced by iron overload.

Identification of mucin depleted foci in the human colon

Aberrant crypt foci (ACF) originally described in rodents treated with colon-specific carcinogens have been identified also in humans at high risk of colon cancer (CRC) and are extensively used as cancer biomarkers. However, studies documenting the heterogeneity of ACF have questioned their precancerous nature. Recently, we described dysplastic foci depleted of mucins (MDF) in the colon of rats treated with colon-specific carcinogens. Like colon tumors, MDFs show activation of Wnt signaling driven by mutations in the beta-catenin gene and Apc, a key gene in colorectal carcinogenesis. Because MDFs have been identified thus far only in rodents, we wanted to search for similar lesions in humans. Familial adenomatous polyposis (FAP) subjects, carrying germ-line mutations in the APC gene, are at high risk of CRC. Therefore, we first searched for MDF-like lesions in unsectioned colon samples from FAP patients and then in patients with sporadic CRC. MDFs were present in the colon of FAP patients (average of 0.0577 lesions/cm(2)) and at a much lower density in CRC patients (average of 0.0006 lesions/cm(2)). ACFs were also observed in all patients. Histologic preparations of all the MDFs identified in FAP and CRC consisted of microadenomas at variable grades of dysplasia. The occurrence of MDF-like lesions in high-risk patients provides evidence that these lesions have a counterpart in human pathology and, as observed in rodents, may represent the very early stages of CRC.

Cyclooxygenase-2 and Hypoxia-Inducible Factor-1alpha protein expression is related to inflammation, and up-regulated since the early steps of colorectal carcinogenesis

Chronic mucosal inflammation is considered a risk factor for colorectal cancer. Neutrophils are a major source of oxidants, whereas cyclooxygenase 2 (COX-2) and Hypoxia Inducible Factor-1alpha (HIF-1alpha) protein expression levels are increased in inflammatory and malignant lesions. The main purpose of the present study was to evaluate myeloperoxidase (MPO) positive cell infiltration, COX-2 and HIF-1alpha protein expression in colorectal carcinogenesis, especially in its early phases, using immunohistochemistry and immunofluorescence confocal microscopy techniques. MPO, COX-2 and HIF-1alpha proteins were expressed at higher rates in the normal colorectal mucosa of patients with inflammatory bowel diseases and colorectal tumours than in patients with normal colonoscopy. A gradual increase in COX-2 and HIF-1alpha protein expression was observed in dysplastic aberrant crypt foci, adenomas and carcinomas, showing a strong relation to dysplasia. In conclusion, the present study supports the hypothesis of a key role of inflammation in malignant transformation of colorectal mucosa. The evaluation of some early markers related to inflammation in the mucosa of the large bowel may serve as potential tool for prognosis and therapeutic strategies.

Aberrant crypt foci in colon cancer epidemiology

Colonic carcinogenesis is characterized by progressive accumulations of genetic and epigenetic derangements. These molecular events are accompanied by histological changes that progress from mild cryptal architectural abnormalities in small adenomas to eventual invasive cancers. The transition steps from normal colonic epithelium to small adenomas are little understood. In experimental models of colonic carcinogenesis aberrant crypt foci (ACF), collections of abnormal appearing colonic crypts, are the earliest detectable abnormality and precede adenomas. Whether in fact ACF are precursors of colon cancer, however, remains controversial. Recent advances in magnification chromoendoscopy now allow these lesions to be identified in vivo and their natural history ascertained. While increasing lines of evidence suggest that dysplastic ACF harbor a malignant potential, there are few prospective studies to confirm causal relationships and supporting epidemiological studies are scarce. It would be very useful, for example, to clarify the relationship of ACF incidence to established risks for colon cancer, including age, smoking, sedentary lifestyle, and Western diets. In experimental animal models, carcinogens dose-dependently increase ACF, whereas most chemopreventive agents reduce ACF incidence or growth. In humans, however, few agents have been validated to be chemopreventive of colon cancer. It remains unproven, therefore, whether human ACF could be used as reliable surrogate markers of efficacy of chemopreventive agents. If these lesions could be used as reliable biomarkers of colon cancer risk and their reductions as predictors of effective chemopreventive agents, metrics to quantify ACF could greatly facilitate the study of colonic carcinogenesis and chemoprevention.

Aberrant crypt foci as precursors in colorectal cancer progression

Colorectal cancer progression originates when accumulated genetic and epigenetic alterations cause genomic instability and a malignant phenotype. Subsequent molecular pathway deregulation leads to histopathologic changes that are clinically evident as aberrant crypt foci (ACF) and visualized by high-magnification chromoscopic colonoscopy. ACF are biomarkers of increased colorectal cancer risk, particularly those with dysplastic features. Genetic profiling using genomic instability, loss of heterozygosity, and methylation analysis has revealed a minority population of ACF genotypically analogous to cancer.

Automated quantification of colonic crypt morphology using integrated microscopy and optical coherence tomography

Colonic crypt morphological patterns have shown a close correlation with histopathological diagnosis. Imaging technologies such as high-magnification chromoendoscopy and endoscopic optical coherence tomography (OCT) are capable of visualizing crypt morphology in vivo. We have imaged colonic tissue in vitro to simulate high-magnification chromoendoscopy and endoscopic OCT and demonstrate quantification of morphological features of colonic crypts using automated image analysis. 2-D microscopic images with methylene blue staining and correlated 3-D OCT volumes were segmented using marker-based watershed segmentation. 2-D and 3-D crypt morphological features were quantified. The accuracy of segmentation was validated, and measured features are in agreement with known crypt morphology. This work can enable studies to determine the clinical utility of high-magnification chromoendoscopy and endoscopic OCT, as well as studies to evaluate crypt morphology as a biomarker for colonic disease progression.

Oncogenic K-ras promotes early carcinogenesis in the mouse proximal colon

Oncogenic K-ras mutations are frequently observed in colon cancers and contribute to transformed growth. Oncogenic K-ras is detected in aberrant crypt foci (ACF), precancerous colonic lesions, demonstrating that acquisition of a K-ras mutation is an early event in colon carcinogenesis. Here, we investigate the role of oncogenic K-ras in neoplastic initiation and progression. Transgenic mice in which an oncogenic K-ras(G12D) allele is activated in the colonic epithelium by sporadic recombination (K-rasLA2 mice) develop spontaneous ACF that are morphologically indistinguishable from those induced by the colon carcinogen azoxymethane (AOM). Similar neoplastic changes involving the entire colon are induced in transgenic mice constitutively expressing K-ras(G12D) throughout the colon (LSL-K-ras(G12D)/Villin-Cre mice). However, the biochemistry and fate of K-ras-induced lesions differ depending upon their location within the colon in these mice. In the proximal colon, K-ras(G12D) induces increased expression of procarcinogenic protein kinase C beta II (PKC beta II), activation of the MEK/ERK signaling axis and increased epithelial cell proliferation. In contrast, in the distal colon, K-ras(G12D) inhibits expression of procarcinogenic PKC beta II and induces apoptosis. Treatment of K-rasLA2 mice with AOM leads to neoplastic progression of small ACF to large, dysplastic microadenomas in the proximal, but not the distal colon. Thus, oncogenic K-ras functions differently in the proximal and distal colon of mice, inducing ACF capable of neoplastic progression in the proximal colon, and ACF with little or no potential for progression in the distal colon. Our data indicate that acquisition of a K-ras mutation is an initiating neoplastic event in proximal colon cancer development in mice.

Colonic aberrant crypts in children with familial adenomatous polyposis

Aberrant crypt foci of the colonic mucosa have been reported in adults. The alteration may be defined macroscopically or histologically and may or may not be combined with adenomatous changes. Aberrant crypt foci have been regarded as precancerous lesions and are more common in patients with familial adenomatous polyposis. The present report describes the presence of many histologically recognizable aberrant crypt foci without adenomatous changes in the colonic mucosa of 3 children with familial adenomatous polyposis. The openings of the aberrant crypt foci contained inspissated granulofilamentous mucus. Additionally, this report documents the presence of a peculiar serrated appearance of the mucosae surface outline of the nonadenomatous areas. This appears to result from elongation of the crypts and dilated openings/micropapillary arrangement of the uppermost part of the walls of the crypts, with a thin intervening stroma. Neither of these findings has been reported previously to occur in children. They may represent the earliest histologically identifiable changes ever recorded in the colon of patients with familial adenomatous polyposis.

Epidemiology of colonic aberrant crypt foci: review and analysis of existing studies

Since first described in a rodent model in 1987, aberrant crypt foci (ACF) in the colon have been shown to exhibit many of the molecular features of the more advanced colonic neoplasms including cancer. Therefore, they may be early lesions with potential for progression, and be valuable biomarkers for reduction of risk of colorectal cancer (CRC). For this review, we searched PubMed, and reference lists of recent publications, for studies which reported on associations of features of ACF in humans, such as number or size, with subject characteristics, such as age or family history of CRC. Over 150 papers have reported on ACF in humans. However, the vast majority of these publications are concerned with molecular and morphological features of biopsied lesions, and not their epidemiology. None of the epidemiological studies were of optimum design, primarily due to their absence of a well-defined subject sampling frame or method. Given their 'first-generation' nature, consistent findings were of increased ACF number with age and with synchronous advanced colonic neoplasia. One study reported a higher mean number of ACF in subjects with a family history of CRC than in those without. The strongest evidence on the ability of ACF to predict a diagnosis of CRC will be from prospective studies with baseline ACF assessment in a large sample of disease-free persons (many thousands) who are followed carefully for many years. In the interim, because ACF are asymptomatic, well-designed cross-sectional studies are feasible and will yield valuable information on the relation of ACF to the known risk factors for CRC. This information can then be used to improve the design of prospective studies, and of clinical intervention trials that use ACF as an intermediate endpoint.

Gene expression patterns distinguish colonoscopically isolated human aberrant crypt foci from normal colonic mucosa

Aberrant crypt foci (ACF) are considered the earliest identifiable preneoplastic colonic lesions; thus, a greater understanding of the nature of genetic changes underlying the transformation of normal colonic mucosa (NM) into ACF may provide insight into the mechanisms of carcinogenesis. ACF were identified by indigo carmine spraying onto colonic mucosa during colonoscopy and isolated as standard pinch biopsies of the mucosal areas containing the ACF. RNAs isolated from ACF and matched NM biopsies from the ascending and descending colons of 13 patients were analyzed on arrays containing 9128 cDNAs. Thirty-four differentially expressed (P < 0.001) genes were found in a paired comparison of the ACF and NM samples, and 25 of 26 matched pairs of ACF and NM could be correctly classified in leave-one-out cross-validation. Differential expression for seven of eight genes was confirmed by real-time reverse transcription-PCR. Furthermore, ACF and NM samples, including six pairs of ACF and NM samples that had not previously been analyzed by array hybridization, can be correctly classified on the basis of the overexpression in ACF of three selected genes (REG4, SRPN-B5, and TRIM29) evaluated by real-time reverse transcription-PCR. In a separate analysis of 13 biopsy pairs from either ascending or descending colon, ACF and NM samples could also be correctly classified by the gene expression patterns. Analysis of gene expression differences in ACF from the ascending and descending colon versus NM samples indicates that ACF from these distinct colonic locations are converging toward similar gene expression profiles and losing differences in gene expression characteristic of NM from the ascending versus descending colon.

Aberrant crypt foci: what we know and what we need to know

Aberrant crypt foci (ACF) have emerged as a putative precursor to colorectal adenomas and are a potential biomarker for colorectal carcinoma. In this review, we describe the histologic and endoscopic characteristics of human ACF, summarize the identified genetic abnormalities, and examine the evidence for using ACF as a biomarker for colorectal carcinoma. The published literature on aberrant crypt foci was identified using a MEDLINE/PubMed search with a secondary review of cited publications. Epidemiologic studies support a role for ACF in the adenoma-carcinoma sequence. Genetic abnormalities that occur in and are characteristic of colorectal carcinoma have been described in ACF. Although chromoendoscopy with magnification colonoscopy can identify human ACF in vivo, standardization of the definition and of the technique for endoscopic identification and classification is needed. Studies of reproducibility, interobserver variability, and continuity over time to validate ACF as a clinical end point are required. ACF hold promise as a biomarker for colorectal carcinoma, but additional study is needed.

Aberrant crypt foci in patients with a positive family history of sporadic colorectal cancer

Early detection is crucial in the prevention of colorectal cancer (CRC) deaths. The earliest detectable neoplastic lesion in the colon is the aberrant crypt foci (ACF). A major question is whether ACF are precursors of CRC, and thus, early biomarkers for CRC risk. If so, we hypothesized that the number of ACF would be higher in patients who had a family history of CRC compared to patients without. We counted ACF in the distal 20cm of colon/rectum during 103 colonoscopic examinations using a prototype Close Focus Colonoscope (Olympus Corp.) with methylene blue chromendoscopy. Each patient was asked whether they had a family history of CRC in a first degree relative, or a personal history of CRC or adenoma. Patients answering 'no' to these questions (n=17) had a mean number of ACF of 4.4; the mean was significantly higher in the patients with a positive family history of CRC (9.0, p<0.01; n=43) or a personal history of advanced adenoma (7.5, p<0.05; n=34).

Assessment of rectal aberrant crypt foci by standard chromoscopy and its predictive value for colonic advanced neoplasms

BACKGROUND AND AIMS

Aberrant crypt foci (ACF) are thought to be preneoplastic lesions and are assessed by magnifying chromoscopy with methylene blue staining. The aim of this study was to evaluate the predictive value of rectal ACF recognized by conventional chromoscopy for colonic advanced neoplasms.

METHODS

Total colonoscopy, involving rectal chromoscopy using indigo carmine with standard colonoscopies, was performed on 386 patients. Patients who showed no ACF were classified as Grade 0, and those who had 1-4, 5-9, and 10+ ACF were classified as Grades 1, 2, or 3, respectively. The correlation between ACF grading and the prevalence of colonic advanced neoplasm, any adenoma>or=1 cm in size and/or with villous or tubulovillous morphology, and/or with high-grade dysplasia or invasive cancer, was assessed.

RESULTS

Sixty-three patients were classified as ACF Grade 0, 119 as Grade 1, 116 as Grade 2, and 88 as Grade 3. Colonic advanced neoplasm was observed in 4 patients (6.3%) for Grade 0, 43 (36.1%) for Grade 1, 61 (52.6%) for Grade 2, and 57 (64.8%) for Grade 3. As the ACF grade increased, the chance of a patient having a colonic advanced neoplasm increased. For multivariate analyses, compared with patients with Grade 0, those with Grades 1, 2, or 3 had a greater risk of colonic advanced neoplasm (odds ratio [OR] 9.18, 95% CI 3.08-27.33, OR 20.44, 95% CI 6.81-61.42, and OR 32.94, 95% CI 10.49-103.41, respectively).

CONCLUSIONS

Chromoscopic assessment of rectal ACF by conventional techniques is useful for predicting colonic advanced neoplasms.

Epigenetic alterations in RASSF1A in human aberrant crypt foci

CpG island methylation (CIM) is an epigenetic mechanism for transcriptional silencing that occurs at various stages of colon tumorigenesis. CIM has been found in serrated adenomas and hyperplastic polyps. There is also evidence for hypermethylation in aberrant crypt foci (ACF) that are found in resected colons from cancer patients. Our study addresses promoter methylation of a tumor suppressor gene, RASSF1A, within the colonic epithelium of subjects undergoing screening colonoscopies in the absence of synchronous tumors. Patients included in this study were at elevated risk for colorectal cancer (CRC) based on family history, but without a previously occurring or synchronous colon carcinoma. ACF were identified using close-focus magnifying chromendoscopy and collected by biopsy in situ. We isolated ACF and adjacent normal colonic epithelium by laser capture microdissection (LCM) and studied methylation of the RASSF1A promoter region in ACF and in adjacent normal mucosa. Expression of RASSF1A was verified using quantitative real-time polymerase chain reaction (QRT-PCR). We found that 8.6% (3 out of 35) of ACF had K-ras mutations and 24% (6 out of 25) had RASSF1A hypermethylation. Our results demonstrate that RASSF1A hypermethylation and K-ras mutations are not mutually exclusive and are present in patients at elevated risk of CRC. Importantly, CIM of RASSF1A is an early epigenetic aberration, occurring in the absence of synchronous colon tumors and is not accompanied by field effects into the surrounding epithelium.

Subcellular localization of beta-catenin and APC proteins in colorectal preneoplastic and neoplastic lesions

Adenomatous polyposis coli (APC) is a tumor suppressor gene whose main function is the destabilization of beta-catenin, a key effector of the Wnt signaling pathway. This gene is defective in familial adenomatous polyposis (FAP), a dominantly inherited disease, but inactivation of APC has been reported also in most sporadic colorectal tumors and it is considered an early event in colorectal tumorigenesis. The aim of the present study was to evaluate the intracellular ultrastructural distribution of beta-catenin and APC proteins in epithelial cells of normal colorectal mucosa, aberrant crypt foci (ACF, an early premalignant lesion) and cancer. We used the immunogold electron microscopic method to identify both proteins. Normal colonic epithelial cells showed a strong membranous expression of beta-catenin and lacked cytoplasmic and nuclear expression. Normal cells showed APC localization pattern characterized by diffuse nuclear expression and along the plasma membrane. In ACF and in carcinoma an absent or reduced membranous expression of beta-catenin was associated with an increased nuclear and cytoplasmatic expression. In aberrant crypt foci and carcinoma, APC was evident inside the nucleus and at the level of cell-cell junctions, but it was decreased in the cytoplasm. This method allowed the accurate localization of proteins of the Wnt signaling pathway in the early steps of colorectal carcinogenesis. The similar pattern of subcellular distribution of APC and beta-catenin in dysplastic ACF and colorectal cancer suggests that ACF are precursor lesions of sporadic and FAP-associated colorectal carcinoma.

Mutant KRAS in aberrant crypt foci (ACF): initiation of colorectal cancer?

Since aberrant crypt foci (ACF) were first described in 1987, they have been the subjects of hundreds of papers; however, the debate continues about their role in colorectal tumorigenesis. This review focuses on the many phenotypic, genetic and epigenetic alterations in ACF that support the hypothesis that ACF are putative precursors of colorectal cancer in both humans and experimental animals. Human ACF, both with and without dysplasia, are monoclonal and display evidence of chromosomal instability. Both of these characteristics are shared by colorectal cancers. While most ACF do not have APC mutations, a large proportion has KRAS mutations and methylated SFRP1 and SFRP2 genes. This epigenetic inactivation gives rise to constitutive Wnt signaling in these putative precursors of colorectal cancer.

Effect of concomitant polyethylene glycol and celecoxib on colonic aberrant crypt foci and tumors in F344 rats

We investigated whether celecoxib augments the protective effect of polyethylene glycol (PEG) on colonic aberrant crypt foci (ACF) and tumor formation in F344 rats treated with azoxymethane (AOM). Three groups of rats received AOM: I (AOM alone), II (PEG), and III (PEG/celecoxib). PEG reduced the mean number of total ACF per colon from 190 to 141 (P < 0.05; 26% reduction) and > or = 4-crypt ACF from 95 to 58 (P < 0.01; 39%). Group III rats had a greater proportion of their ACF distally; whereas transverse colon ACF were reduced approximately 50%, distal ACF were reduced by only approximately 8% (P < 0.05). Of 13 large bowel tumors, 8 were in Group I, 4 in Group II, and 1 in Group III rats (P = 0.02). Thus in AOM-treated rats celecoxib appeared to enhance the PEG-induced reduction in colonic tumor formation, and in transverse but not distal or whole-colon ACF.

Role of aberrant crypt foci detected using high-magnification-chromoscopic colonoscopy in human colorectal carcinogenesis

Abstract Liaison between gastrointestinal endoscopists and histopathologists is essential to provide the highest standards of diagnostic accuracy and patient management. The histopathologist needs to be aware of the endoscopic findings when interpreting endoscopic biopsies. High-magnification-chromoscopic-colonoscopy (HMCC) is a new technology that provides the endoscopists with much greater resolution and functional staining of the gastrointestinal tract. Using HMCC, the endoscopist is now able to identify subtle changes in the colorectal luminal openings or crypts. Changes in crypt appearances now allow detection of aberrant crypt foci (ACF) in the colon, which might themselves be precancerous lesions but additionally might serve as a valid biomarker of subsequent adenoma and colorectal cancer formation. This article describes the role of the aberrant crypt focus in colorectal carcinogenesis and discusses the clinical impact of HMCC techniques as applicable to ACF.

Aberrant crypt foci as microscopic precursors of colorectal cancer

Since the first detection of aberrant crypt foci (ACF) in carcinogen-treated mice, there have been numerous studies focusing on these microscopically visible lesions both in rodents and in humans. ACF have been generally accepted as precancerous lesions in regard to histopathological characteristics, biochemical and immunohistochemical alterations, and genetic and epigenetic alterations. ACF show variable histological features, ranging from hyperplasia to dysplasia. ACF in human colon are more frequently located in the distal parts than in the proximal parts, which is in accordance with those in colorectal cancer (CRC). The immunohistochemical expressions of carcinoembryonic antigen (CEA), β-catenin, placental cadherin (P-cadherin), epithelial cadherin (E-cadherin), inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and P16^INK4a are found to be altered. Genetic mutations of K-ras, APC and p53, and the epigenetic alterations of CpG island methylation of ACF have also been demonstrated. Genomic instabilities due to the defect of mismatch repair (MMR) system are detectable in ACF. Two hypotheses have been proposed. One is the "dysplasia ACF-adenoma-carcinoma sequence", the other is "heteroplastic ACF-adenoma-carcinoma sequence". The malignant potential of ACF, especially dysplastic ACF, makes it necessary to reveal the nature of these lesions, and to prevent CRC from the earliest possible stage. The technique of magnifying chromoscope makes it possible to detect "in vivo" ACF, which is beneficial to colon cancer research, identifying high-risk populations for CRC, and developing preventive procedures.

Colorectal polyps and other precursor lesions. Need for an expanded view

The traditional understanding of adenomas serving as precursors for a homogeneous group of adenocarcinomas is being assailed from all sides. Clearly, the relationship between precursor lesions and adenocarcinomas with defective DNA mismatch repair is much more complex and appears to include right-sided hyperplastic polyps as precursor lesions in some cases. Additional data will be forthcoming regarding this risk of adenocarcinoma development in right-sided hyperplastic polyps, both through defective DNA mismatch repair and methylation of the MGMT gene. This will likely be accompanied by an attempt to reclassify at least some larger hyperplastic polyps as serrated adenomas either on subtle morphologic or molecular grounds.

Endoscopic identification and quantification of aberrant crypt foci in the human colon

BACKGROUND

Aberrant crypt foci may be precancerous lesions in the human colon. The occurrence of aberrant crypt foci was compared in patients with an endoscopically normal colon, known adenomatous polyps, and known colorectal cancer.

METHODS

In 90 patients (30 colonoscopically normal, 30 with adenomatous polyps, 30 with colorectal cancers) magnification chromoscopy was performed to identify aberrant crypt foci in the distal 10 cm of the rectum. Representative biopsy specimens were obtained for histopathologic assessment.

RESULTS

Aberrant crypt foci were readily identified. Median and (mean) numbers of aberrant crypt foci were as follows: endoscopically normal colon, 3.5 (5.0); adenomatous polyp(s), 4.0 (6.9); and colorectal cancer, 7.5 (9.9). The number of aberrant crypt foci detected was significantly associated (p = 0.02) with an increased odds that a patient would be in the group with known colorectal cancer (odds ratio = 1.11; 95% CI [1.02, 1.21]), but not in any other group.

CONCLUSIONS

Despite a stepwise increase in the number of aberrant crypt foci across the 3 groups, aberrant crypt foci was significantly associated only with comorbid colorectal cancer. Aberrant crypt foci was not associated with adenomatous polyp(s) or normal colon. Additional studies are needed to further elucidate the role of aberrant crypt foci in the development of colorectal neoplasia in humans.

A critical review of the toxicological effects of carrageenan and processed eucheuma seaweed on the gastrointestinal tract

Carrageenan is a high-molecular-weight, strongly anionic polymer derived from several species of red seaweed that is used for the textural stabilization of foods. Processed Eucheuma Seaweed (PES) is a form of carrageenan with a higher cellulose content. Food-grade carrageenan has a weight average molecular weight greater than 100,000 Da, with a low percentage of smaller fragments. Carrageenan is not degraded to any extent in the gastrointestinal tract and is not absorbed from it in species examined, such as rodents, dogs, and non-human primates. Systemically administered carrageenan has been reported to have a variety of effects, particularly on the immune system, but these are not pertinent to orally administered carrageenan. The substance poligeenan (formerly referred to as degraded carrageenan) is not a food additive. It exhibits toxicological properties at high doses that do not occur with the food additive carrageenan. In-long term bioassays, carrageenan has not been found to be carcinogenic, and there is no credible evidence supporting a carcinogenic effect or a tumor-promoting effect on the colon in rodents. Also, like many dietary fibers, there is significant cecal enlargement in rodents when it is administered at high doses, but this does not appear to be associated with any toxicological consequences to the rodent. Many toxicological studies on carrageenan have involved administration at doses in excess of today's standards for dietary feeding levels in bioassays, and they are orders of magnitude in excess of those to which humans are exposed. Previous reviews of carrageenan and PES by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) have recommended a group allowable daily intake (ADI) of "not specified". The lack of carcinogenic, genotoxic, or tumor-promoting activity with carrageenan strongly supports continuing such an ADI, and JECFA, during its most recent review in 2001, continued this recommendation. The various toxicological studies related to orally administered food-grade carrageenan are summarized along with a brief discussion of critical factors in intestinal carcinogenesis.

Deletion of functional gastrin gene markedly increases colon carcinogenesis in response to azoxymethane in mice

BACKGROUND & AIMS

We recently reported that transgenic mice overexpressing progastrin were at a higher risk for developing colon cancers in response to azoxymethane (AOM), whereas mice overexpressing gastrin-17 were at a reduced risk. To examine further the role of gastrins in colon carcinogenesis, we generated gastrin gene knockout mice (GAS-KO).

METHODS

The height and proliferative index (PI) of colonic crypts were similar in GAS-KO and wild-type (WT) mice, suggesting that the absence of gastrins in GAS-KO mice did not significantly affect the growth of colonic mucosa. GAS-KO and WT mice were treated with AOM for 3-4 weeks; control mice received saline.

RESULTS

Colonic proliferation in response to AOM was significantly increased in GAS-KO vs. WT mice. Aberrant crypt foci (ACFs) were similarly increased significantly by approximately 2-5-fold in GAS-KO vs. WT mice after 2 weeks of AOM treatment. Female GAS-KO mice developed adenomas (Ads) and adenocarcinomas (AdCAs) at earlier times ( approximately 10 months) than the male GAS-KO mice and the male and female WT mice ( approximately 12 months). The total numbers of Ads and AdCAs were significantly higher in GAS-KO than in WT mice.

CONCLUSIONS

These results suggest the novel possibility that loss of gastrin expression (and hence amidated gastrins) significantly increases susceptibility to colon carcinogenesis in response to AOM. Previous studies with FVB/N transgenic mice similarly suggested a protective role of amidated gastrins against colon carcinogenesis, which supports the present findings of an increase in colon carcinogenesis in GAS-KO mice lacking normal physiological levels of amidated gastrins.

Histologic precursors of gastrointestinal tract malignancy

Precursor lesions in the GIT include flat dysplasias, adenomas, dysplasia superimposed on nonneoplastic polyps, endocrine cell dysplasia, ACF, and condyloma accuminatum. Interobserver variability can be a problem in reporting dysplasia, and ancillary techniques including flow cytometry, image analysis, proliferation markers, and examination for p53 expression can help in this task. Squamous dysplasia seen in the esophagus and anus is graded on either a two-tiered or three-tiered system largely based on the extent of mucosal involvement. Glandular dysplasia is morphologically similar whether seen as an adenomatous polyp or within the setting of Barrett's esophagus, atrophic gastritis, or idiopathic inflammatory bowel disease. The distinction between LGD and HGD in glandular mucosa is based on the severity of cytologic and architectural distortion. Type I dysplasia is the classic adenomatous pattern seen most commonly and recognized by the presence of elongate hyperchromatic stratified nuclei. Type II, the nonadenomatous variant, contains vesicular nuclei and alteration in nuclear size and shape. Nonantral endocrine dysplasia in the stomach is seen in the setting of corporal predominant atrophic chronic gastritis and Zollinger-Ellison syndrome with Multiple Endocrine Neoplasia syndrome type I. Condyloma accuminatum is a HPV-related lesion most commonly seen in men practicing anal intercourse. Superimposed squamous dysplasia can be seen with HGD most frequently in the HIV-positive population. Recognition of the different classification systems of dysplasia, the most frequent settings in which these lesions are found, and their natural history is important for all practicing gastroenterologists and pathologists.

Aberrant crypt foci in colorectal carcinogenesis. Cell and crypt dynamics

Aberrant crypt foci (ACF) have been identified on the colonic mucosal surface of rodents treated with colon carcinogens and of humans after methylene-blue staining and observation under a light microscope. Several lines of evidence strongly suggest that ACF with certain morphological, histological, cell kinetics, and genetic features are precursor lesions of colon cancer both in rodents and in humans. Thus, ACF represent the earliest step in colorectal carcinogenesis. This paper has the main purpose of reviewing the evidence supporting this view, with particular emphasis on cell and crypt dynamics in ACF. ACF have been used as intermediate biomarkers of cancer development in animal studies aimed at the identification of colon carcinogens and chemopreventive agents. Recently, evidence has also shown that ACF can be effectively employed in chemopreventive studies also in humans.

Analysis of K-ras, APC, and beta-catenin in aberrant crypt foci in sporadic adenoma, cancer, and familial adenomatous polyposis

BACKGROUND & AIMS

We have previously shown that aberrant crypt foci (ACF) are the putative precursor lesions of colorectal adenomas and subsequent cancer in humans using magnifying endoscopy. The present study was designed to investigate these genetic alterations in ACF biopsy specimens from normal subjects, familial adenomatous polyposis (FAP) or sporadic patients.

METHODS

The non-FAP cases included 34 normal subjects, 35 colorectal adenoma patients, and 19 colorectal cancer patients; there were 4 FAP patients. Biopsies were performed on ACF by magnifying endoscopy. K-ras mutations were analyzed by 2-step polymerase chain reaction and restriction fragment length polymorphism, APC mutations by in vitro-synthesized protein assay, and beta-catenin mutations by direct sequencing. Full-length APC and beta-catenin were detected by immunofluorescence.

RESULTS

In non-FAP cases, K-ras mutations were detected in 82% (89/106) of nondysplastic ACF and 63% (17/27) of dysplastic ACF. APC mutation and beta-catenin accumulation were not detected in non-FAP ACF, whereas in adenoma of these patients, positivity of APC mutation and beta-catenin accumulation were 78% (24/31), and that of K-ras mutation was 65% (20/31). FAP patients showed K-ras mutations in only 13% (1/8) of dysplastic ACF, which is the predominant form of ACF found in FAP. In FAP patients, somatic APC mutations were found in 100% of dysplastic ACF, as they are in adenoma. The frequency of K-ras mutations was 73% (8 of 11) in FAP adenoma.

CONCLUSIONS

The data suggest that in sporadic colorectal carcinogenesis, assuming the biological implication of ACF as a precursor of adenomas, there is a route where K-ras mutation mainly occurs during the formation of ACF, which then become adenomas wherein APC mutation occurs. In FAP, however, somatic mutation of APC predominantly occurs during ACF formation, followed by K-ras mutation.