Detection of aberrant crypt foci by magnifying colonoscopy

Unveiling antioxidant and anti-cancer potentials of characterized Annona reticulata leaf extract in 1,2-dimethylhydrazine-induced colorectal cancer in Wistar rats

BACKGROUND

Colorectal cancer (CC) is the third most common cancer in the world. Annona reticulata (AR) also known as bullock's heart, is a traditional herb. AR leaf extract was initially investigated for its anti-bacterial, anti-inflammatory, anti-malarial, anti-helminthic, anti-stress, and wound healing properties. Only a few in vitro cancer studies have been conducted on AR. Although few studies have linked AR leaf extract to many cancers, comprehensive studies addressing regulation, biological functions, and molecular mechanisms leading to CC pathogenesis are clearly lacking.

OBJECTIVES

The present study aimed to explore the antioxidant and anti-cancer potentials of AR leaf extract in CC.

MATERIALS AND METHODS

The MTT assay was used to test the anti-proliferative activity of AR leaf extract in vitro on the HCT116 cell line. Qualitative and quantitative phytochemical characterization was carried out using gas chromatography: mass spectrometry (GC-MS). 1,2-dimethylhydrazine (DMH) was used to establish CC model in female Wistar rats. The acute toxicity of AR leaf extract was tested in accordance with OECD guidelines. Aberrant Crypt Foci (ACF) count, organ index, and hematological estimations were used to screen for in vivo anti-cancer potential. The antioxidant activity of colon homogenate was determined.

RESULTS

The alcoholic leaf extract (IC50, 0.55 μg/ml) was found to be more potent than the aqueous extract. Using GC-MS, a total of 108 compounds were quantified in the alcoholic leaf extract. The LD 50 value was found to be safe at a dose of 98.11 mg/kg of body weight. AR alcoholic leaf extract significantly (p < 0.05) decreased ACF count and normalized colon length/weight ratio. AR leaf extract increased RBC, hemoglobin and platelets levels. The AR alcoholic leaf extract reduced the DMH-induced tumors and significantly (p < 0.05) increased the activity of endogenous antioxidant enzymes such as catalase, reduced glutathione, superoxide dismutase, and decreased the lipid peroxidase activity. AR leaf extract reduced the inflammation caused by DMH and helped to repair the colon's damaged muscle layers.

CONCLUSION

Based on the findings from the present study, it can be concluded that the alcoholic leaf extract of AR has antioxidant and anti-proliferative properties and can aid in the prevention of CC development and dysplasia caused by DMH.

Randomized Phase II Trial of Polyphenon E versus Placebo in Patients at High Risk of Recurrent Colonic Neoplasia

Polyphenon E (Poly E) is a green tea polyphenol preparation whose most active component is epigallocatechin gallate (EGCG). We studied the cancer preventive efficacy and safety of Poly E in subjects with rectal aberrant crypt foci (ACF), which represent putative precursors of colorectal cancers. Eligible subjects had prior colorectal advanced adenomas or cancers, and had ≥5 rectal ACF at a preregistration chromoendoscopy. Subjects (N = 39) were randomized to 6 months of oral Poly E (780 mg EGCG) daily or placebo. Baseline characteristics were similar by treatment arm (all P >0.41); 32 of 39 (82%) subjects completed 6 months of treatment. The primary endpoint was percent reduction in rectal ACF at chromoendoscopy comparing before and after treatment. Among 32 subjects (15 Poly E, 17 placebo), percent change in rectal ACF number (baseline vs. 6 months) did not differ significantly between study arms (3.7% difference of means; P = 0.28); total ACF burden was also similar (-2.3% difference of means; P = 0.83). Adenoma recurrence rates at 6 months were similar by arm (P > 0.35). Total drug received did not differ significantly by study arm; 31 (79%) subjects received ≥70% of prescribed Poly E. Poly E was well tolerated and adverse events (AE) did not differ significantly by arm. One subject on placebo had two grade 3 AEs; one subject had grade 2 hepatic transaminase elevations attributed to treatment. In conclusion, Poly E for 6 months did not significantly reduce rectal ACF number relative to placebo. Poly E was well tolerated and without significant toxicity at the dose studied. PREVENTION RELEVANCE: We report a chemoprevention trial of polyphenon E in subjects at high risk of colorectal cancer. The results show that polyphenon E was well tolerated, but did not significantly reduce the number of rectal aberrant crypt foci, a surrogate endpoint biomarker of colorectal cancer.

Occurrence of colorectal aberrant crypt foci depending on age and dietary patterns of patients

Background

Aberrant crypt foci (ACF) are commonly considered the early pre-cancerous lesions that can progress to colorectal cancer (CRC). The available literature data reveal that age, dietary factors and lifestyle can affect the development of several dozen percentages of malignant tumours, including CRC. In the present study, an attempt was made to assess the incidence and growth dynamics of ACF and to determine whether the type of diet affected the development and number of AFC.

Methods

Colonoscopy combined with rectal mucosa staining with 0.25% methylene blue was performed in 131 patients. On the day of examination, each patient completed a questionnaire regarding epidemiological data. According to their numbers, colorectal ACF were divided into three groups. The findings were analysed statistically. The Student’s t test and the U test were applied in order to determine the significance of differences of means and frequency of events in both groups. Statistica 7.1 and Excel 2010 were used.

Results

The single ACF occur in the youngest individuals (ACF < 5). Since the age of 38 years, the number of ACF gradually increases to show a decreasing tendency since the age of 60 years. The number of 5 < ACF < 10 occurs slightly later, since the age of 50 years, and dynamically increases reaching the maximum at the age of 62 years, subsequently the increase is proportional. ACF > 10 occur at a more advanced age (55 years) and their number gradually increases with age. The maximum number is observed at the age of 77 years.

In individuals not using high-fibre diets and with high intake of red meat, the probability of higher numbers of ACF increases. The probability of higher numbers of ACF (5 < ACF10) was observed in patients with colon diverticula. In patients with higher BMI, the number of ACF is higher.

Conclusion

Age significantly affects the number of colorectal ACF. The types of foods consumed can considerably increase the risk of colorectal ACF, which is particularly visible in individuals who do not regularly use high-fibre diets, those obese and with colon diverticula.

A phase IIa randomized, double-blind trial of erlotinib in inhibiting epidermal growth factor receptor signaling in aberrant crypt foci of the colorectum

Colorectal cancer progresses through multiple distinct stages that are potentially amenable to chemopreventative intervention. Epidermal growth factor receptor (EGFR) inhibitors are efficacious in advanced tumors including colorectal cancer. There is significant evidence that EGFR also plays important roles in colorectal cancer initiation, and that EGFR inhibitors block tumorigenesis. We performed a double-blind randomized clinical trial to test whether the EGFR inhibitor erlotinib given for up to 30 days had an acceptable safety and efficacy profile to reduce EGFR signaling biomarkers in colorectal aberrant crypt foci (ACF), a subset of which progress to colorectal cancer, and normal rectal tissue. A total of 45 patients were randomized to one of three erlotinib doses (25, 50, and 100 mg) with randomization stratified by nonsteroidal anti-inflammatory drug (NSAID) use. There were no unanticipated adverse events with erlotinib therapy. Erlotinib was detected in both normal rectal mucosa and ACFs. Colorectal ACF phosphorylated ERK (pERK), phosphorylated EGFR (pEGFR), and total EGFR signaling changes from baseline were modest and there was no dose response. Overall, this trial did not meet is primary efficacy endpoint. Colorectal EGFR signaling inhibition by erlotinib is therefore likely insufficient to merit further studies without additional prescreening stratification or potentially longer duration of use.

Predictive value of rectal aberrant crypt foci for intraepithelial neoplasia in ulcerative colitis - a cross-sectional study

BACKGROUND

Ulcerative colitis (UC) is associated with an increased risk of colorectal cancer (CRC). Aberrant crypt foci (ACF) are important biomarkers of sporadic CRC risk. Their correlation with the risk of intraepithelial neoplasia (IN) in UC remains unclear.

AIMS

To assess whether ACF are a risk factor for IN in long-standing UC and to investigate any correlation between the clinico-epidemiological characteristics and prevalence/number of ACF in these patients.

METHODS

Seventy-six patients with long-standing UC were prospectively screened by colonoscopy with chromoendoscopy-guided endomicroscopy. ACF were sought in the lower rectum.

RESULTS

Eight INs were detected in seven (9.2%) patients. The ACF prevalence and mean number were 60.5% and 2.4 ± 2.8, respectively. The number of ACF was independently associated with the risk of having IN (odds ratio = 1.338; 95% confidence interval 1.030-1.738). ACF number revealed a good calibration (area under the receiver operating characteristic curve = 0.829) and discriminative ability (p = 0.205, Hosmer-Lemeshow test) for the prediction of synchronous IN. Patients with ≥3 ACF have a significantly higher prevalence of IN than patients with <3 ACF (22.6% vs. 0%, p = 0.001). Using this cut-off value, the performance of ACF in predicting the presence of IN was as follows: sensitivity = 100%, specificity = 65.2%, positive predictive value = 22.6%, and negative predictive value = 100%. Age >40 years, family history of CRC, and increased body mass index (BMI) were associated with a significantly higher number of ACF.

CONCLUSION

Long-standing UC patients with ≥3 ACF have a significantly higher likelihood of having IN. Age >40 years, family history of CRC, and increased BMI have significant positive associations with the number of ACF.

HD chromoendoscopy coupled with DNA mass spectrometry profiling identifies somatic mutations in microdissected human proximal aberrant crypt foci

Despite increased implementation of screening colonoscopy, interval cancers in the proximal colon remain a major public health concern. This fact underscores the limitations of current screening paradigms and the need for developing advanced endoscopic techniques. The density of aberrant crypt foci (ACF), the earliest identifiable mucosal abnormality, may serve as a surrogate marker for colon cancer risk, but has rarely been studied in the proximal colon. To this end, high-definition (HD) chromoendoscopy was conducted to define the relevance of ACF in the proximal colon. In addition, due to limited ACF size, the development of a combinatorial approach was required to maximize data acquisition obtained from individual biopsy samples. Proximal and distal ACF samples were characterized for a total of 105 mutations across 22 known tumor suppressor and proto-oncogenes using high-throughput Sequenom MassARRAY analysis. From this profiling, a discrete number of somatic mutations were identified, including APC(R876*) and FLT3(I836M), as well as a deletion within the EGFR gene. Combined, these data highlight the significance of ACF within the context of colon cancer pathogenesis, particularly in the proximal colon.

IMPLICATIONS

The identification of cancer-related mutations in commonly overlooked mucosal lesions underscores the preventive benefit of implementing advanced endoscopic screening to larger patient populations, particularly in the proximal colon. Visual Overview: http://mcr.aacrjournals.org/content/early/2014/05/22/1541-7786.MCR-13-0624/F1.large.jpg. Mol Cancer Res; 12(6); 823-9. ©2014 AACR.

LINE-1 hypomethylation is neither present in rectal aberrant crypt foci nor associated with field defect in sporadic colorectal neoplasia

Background

Aberrant crypt foci (ACF) are considered the first identifiable preneoplastic lesion in colorectal cancer (CRC), and have been proposed as a potential biomarker for CRC risk. Global DNA hypomethylation is an early event in colorectal carcinogenesis, and long interspersed nuclear element-1 (LINE-1) methylation status is a well-known surrogate marker for genome-wide DNA methylation levels. Despite the gradual increase in DNA hypomethylation in the adenoma–carcinoma sequence, LINE-1 methylation in ACF has never been studied. Moreover, recent studies have reported a field defect for LINE-1 hypomethylation, suggesting that LINE-1 methylation status in normal mucosa could be used to stratify CRC risk and tailor preventive strategies. Thus, we assessed LINE-1 status by pyrosequencing in rectal ACF and paired normal colorectal mucosa from individuals with sporadic colon cancer (CC) (n = 35) or adenoma (n = 42), and from healthy controls (n = 70).

Findings

Compared with normal mucosa, LINE-1 in ACF were hypermethylated across all groups (P < 0.0001). Furthermore, LINE-1 methylation status in normal colorectal mucosa was independent of the presence of adenoma or CC (P = 0.1072), and did not differ depending on the distance to the adenoma or CC. Interestingly, when we compared the LINE-1 methylation status in normal mucosa from different segments of the colorectum, we found higher hypomethylation in the rectum compared with the descending colon (P < 0.0001).

Conclusions

Overall, our results suggest that global hypomethylation is not present in rectal ACF and argues against the existence of LINE-1 methylation field defect in sporadic colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1868-7083-6-24) contains supplementary material, which is available to authorized users.

Nanoproteomic analysis of extracellular receptor kinase-1/2 post-translational activation in microdissected human hyperplastic colon lesions

Oncogenic activation resulting in hyperproliferative lesions within the colonic mucosa has been identified in putative precancerous lesions, aberrant crypt foci (ACF). KRAS and BRAF mutation status was determined in 172 ACF identified in the colorectum of screening subjects by in situ high-definition, magnifying chromoendoscopy. Lesions were stratified according to histology (serrated vs. distended). Due to their limiting size, however, it was not technically feasible to examine downstream signaling consequences of these oncogenic mutations. We have combined ultraviolet-infrared (UV/IR) microdissection with an ultrasensitive nanofluidic proteomic immunoassay (NIA) to enable accurate quantification of posttranslational modifications to mitogen-activated protein kinase (MAPK) in total protein lysates isolated from hyperproliferative crypts and adjacent normal mucosa. Using this approach, levels of singly and dually (activated) phosphorylated isoforms of extracellular receptor kinase(ERK)-1 and ERK-2 were quantified in samples containing as little as 16 ng of total protein recovered from <200 cells. ERK activation is responsible for observed hyperplasia found in these early lesions, but is not directly dependent on KRAS and/or BRAF mutation status. This study describes the novel use of a sensitive nanofluidic platform to measure oncogene-driven proteomic changes in diminutive lesions and highlights the advantage of this approach over classical immunohistochemistry-based analyses.

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.

Biology and diagnosis of aberrant crypt foci

AIM

Aberrant crypt foci (ACFs) are clusters of colonic crypts that can be identified after staining and that have a different behaviour than the surrounding crypts. They have been hypothesized to be the potential precursors of colonic neoplastic lesions. Since they are detectable in vivo with endoscopic stains, they have been proposed as early biomarkers for colonic carcinogenesis. Our aim was to examine the literature regarding the role of ACFs in the pathogenesis of colorectal cancer (CRC).

METHOD

An intensive PubMed search was performed with the following terms: aberrant crypt foci, colorectal cancer, biomarker, carcinogenesis.

RESULTS

  Aberrant crypt foci have a variable prevalence and little is known about their natural history. They can be classified as hyperplastic or dysplastic. There is evidence that supports their role as preneoplastic lesions and features detectable by chromoendoscopy have been related to CRC risk. Moreover, ACFs have been shown to harbour genetic and epigenetic alterations common in adenomas and CRC. However, contradictory results have been obtained and difficulties in endoscopic detection and characterization have been described in large-scale studies.

CONCLUSION

  Despite the inconsistencies in ACF detection and characterization, several genetic and epigenetic changes common in both ACFs and CRC have been verified throughout the studies. This evidence is increasingly strong and it grows along with progress in the knowledge of carcinogenesis molecular pathways. Clinical application of ACFs as an intermediate endpoint for colorectal carcinogenesis is under development and a deeper knowledge of cancer mechanisms is needed before it can be applied or discarded.

Pathophysiological Roles of PPARgamma in Gastrointestinal Epithelial Cells

Although the highest levels of PPARγ expression in the body have been reported in the gastrointestinal epithelium, little is known about the physiological functions of that receptor in the gut. Moreover, there is considerable controversy concerning the effects of thiazolidinedione PPARγ agonists on the two major diseases of the gastrointestinal track: colorectal cancer and inflammatory bowel disease. We will undertake to review both historical and recently published data with a view toward summarizing what is presently known about the roles of PPARγ in both physiological and pathological processes in the gastrointestinal epithelium.

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.

Aberrant crypt foci: endoscopic assessment and cell kinetics characterization

BACKGROUND AND AIMS

Aberrant crypt foci (ACF) are preneoplastic lesions in animal models of colorectal cancer. The aim of the study is to investigate if ACF are involved in human colorectal carcinogenic process and if they can be helpful in predicting the presence of a colorectal neoplasia.

METHODS

The study included, between 2003 and 2005, 182 patients, 62 with adenoma, 55 with colorectal carcinoma, 53 without colorectal lesions, and 12 with nonneoplastic mucosal polyps. The number of rectal ACF was determined by colonoscopy. Proliferation and apoptosis indexes were evaluated by immunohistochemistry in rectal ACF, in normal rectal mucosa, and in carcinomatous tissue.

RESULTS

The mean number of rectal ACF in patients with rectal neoplasia was 12.64, significantly higher than in patients with neoplastic lesions elsewhere in the colon (p=0.01). The apoptosis index in ACF of patients with colorectal carcinoma or adenoma aged 50 years or older was significantly lower than in younger patients (1.3% vs 2.7%, p=0.01) and, in patients with carcinoma, lower than in normal mucosa (1.1% vs 2.1%, p=0.002). The proliferation index was significantly higher in ACF of patients with colorectal neoplasia aged less than 50 years than in normal mucosa (10.9% vs 7.7%, p=0.02). The apoptosis index in ACF foci of patients with carcinoma (1.1%) was significantly lower than in patients without lesions (2.2%) and than in normal mucosa (2%). The mean number of ACF is significantly higher in patients with polyps larger than 1 cm (11.28 vs 6.27, p=0.02).

CONCLUSION

Aberrant crypt foci probably precede the appearance of neoplasia and may be helpful in predicting the presence of a colorectal neoplastic lesion.

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: are they intermediate endpoints of colon carcinogenesis in humans?

PURPOSE OF REVIEW

There is a wealth of literature, both from epidemiological and molecular studies, which support the role of aberrant crypt foci (ACF) as a putative precursor to colorectal adenomas and a potential biomarker for colorectal carcinoma. In this review, we critically examine the evidence on employing ACF as an intermediate endpoint.

RECENT FINDINGS

Recent, larger-scale, multicenter studies of ACF have raised questions about ACF. The prevalence of ACF has not correlated with colorectal adenomas, and the technique for ACF detection using high-magnification chromoendoscopy has demonstrated considerable variability across endoscopists and over time. Dysplastic ACF, once postulated as the ACF destined for adenomatous transformation, have been rarely identified in US individuals, in contrast to European and Japanese investigations. A substantial percentage of purported, endoscopically detected ACF have not been confirmed on histologic review. Finally, molecular characterization of ACF has been studied on only a limited basis.

SUMMARY

ACF remain a potential biomarker for colorectal cancer, but similar to other biomarkers under development, additional study of ACF is needed before reliable, clinical application can be assured.

Aberrant crypt focus size predicts distal polyp histopathology

Aberrant crypt foci (ACF) are the earliest histopathologic lesion associated with colorectal cancer. ACFs are commonly used as a surrogate marker for colorectal cancer chemoprevention studies in rodents and, more recently, in humans. However, ACF prevalence in unselected populations is not known, nor which ACF features are important for predicting polyp histopathology. To address these questions, we did magnification chromo-colonoscopy on all patients undergoing routine colorectal cancer screening over a 31-month period. ACFs were classified by location, size (small, <20 crypts/ACF; medium, 20-100 crypts/ACF; large, >100 crypts/ACF), and whether they were elevated above the tissue plane. Overall, 802 magnification chromo-colonoscopies with ACF enumeration were done. Mean patient age was 58.6 +/- 8.5 years, of whom 56% were female, 58% were African American, 21% were Caucasian, and 16% were Latino. Total ACF number, along with increasing ACF size and elevation, correlated with the presence of distal hyperplastic polyps and were higher in African Americans. In contrast, ever-smaller ACFs correlated with the presence of distal adenomas and were independent of age and race. The odds ratio for patients with >or=6 small ACFs and adenomas was 6.02 (95% confidence interval, 2.64-13.70) compared with patients with <or=5 small ACFs, whereas the odds ratio for patients with >or=1 large ACF and hyperplastic polyps was 5.88 (95% confidence interval, 3.00-11.67) compared with patients with none. Small flat ACFs correlate with the presence of distal adenomas, whereas large raised ACFs correlate with the presence of hyperplastic polyps.

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.

The high affinity peroxisome proliferator-activated receptor-gamma agonist RS5444 inhibits both initiation and progression of colon tumors in azoxymethane-treated mice

We evaluated RS5444, a thiazolidinedione high affinity PPARgamma agonist, for the ability to inhibit colon carcinogenesis in azoxymethane (AOM)-treated mice. In our initial experiment, mice were treated with RS5444 during AOM treatment, and the drug was withdrawn 12 weeks after the last injection of AOM. RS5444 significantly inhibited aberrant crypt focus formation under these circumstances. Furthermore, exposure to RS5444 during the course of AOM treatment effectively blocked colon tumor formation after withdrawal of the agonist. PPARgamma expression and nuclear localization were reduced in adenomas. RS5444 did not inhibit DNA synthesis in tumor cells, suggesting that PPARgamma activity was impaired in adenomas. To test this hypothesis, pre-existing adenomas were treated with RS5444 for 16 weeks. We observed a slight, albeit not statistically significant, reduction in tumor incidence in RS5444-treated mice. However, histological examination revealed that tumors from RS5444-treated mice were of significantly lower grade, as evaluated by the extent of dysplasia. Furthermore, carcinoma in situ was observed in about one-third of control tumors, but was never observed in RS5444-treated tumors. We conclude that RS5444 inhibits both initiation and progression of colon tumors in the AOM model of sporadic colon carcinogenesis.

The natural history of aberrant crypt foci

BACKGROUND

Aberrant crypt foci (ACF) are the putative precursors to colorectal adenomas and may be useful as biomarkers. Knowledge of their natural history is essential to understanding their potential utility.

OBJECTIVE

Our purpose was to examine ACF detection 1 year after initial observation.

DESIGN

We conducted a multicenter study of ACF by using a standardized protocol. ACF in the rectum were assessed and subjects returned 1 year later to evaluate the natural history of the lesions.

SETTING

Ancillary study to the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.

RESULTS

Of 78 subjects enrolled, 64 (82%) returned for a repeat examination 1 year later. The mean age was 71 years, 70% were male, and 54% had a history of adenomatous polyps. At the initial examination, 66% of subjects had at least 1 ACF detected in the rectum, with a mean of 2.1 +/- 2.3 per person. One year later, 60% of these subjects had at least 1 of the original ACF reidentified, but only 43% of all ACF were reidentified. A total of 56% of subjects had new ACF identified.

LIMITATIONS

These results are generated from the pilot phase. Improvements or change in technique over time could have influenced the results.

CONCLUSIONS

A total of 60% of subjects who had ACF continued to have at least one ACF 1 year later, but less than half the specific ACF could be reidentified, and more than 50% of subjects had new ACF. These results imply a considerable dynamic to ACF detection over a 1-year period of observation.

CYP27A1 and CYP24 expression as a function of malignant transformation in the colon

Vitamin D deficiency is strongly associated with the risk of developing colorectal cancer (CRC). Because of the propensity of bioactive 1,25-dihydroxyvitamin D3 to cause toxic hypercalcemia, considerable effort has been directed to identifying safer drugs while retaining the efficacy of the parent compound. However, vitamin D precursors do not present toxicity concerns and may be sufficient for CRC chemoprevention or chemotherapy, providing the appropriate enzymes are present in colonic epithelia. We previously showed that CYP27B1 is present at equally high levels in the colon and CRC irrespective of differentiation but was not present in metastases. In this study we used quantitative immunohistochemistry to show that CYP27A1, converting D3 to 25-hydroxycholecalciferol, is present in increasing concentrations in the nuclei of normal colonic epithelia, aberrant crypt foci (ACF), and adenomatous polyps. Whereas total cellular CYP27A1 remains high in CRC and lymph node metastases, the amount of enzyme present in the nuclei decreases with tumor cell dedifferentiation while rising in the cytoplasm. Similarly, increasing amounts of the deactivating enzyme CYP24 are present in the nuclei of normal colonic epithelia, ACFs, and adenomatous polyps. Although the amount of total CYP24 decreases slightly in CRC as a function of tumor cell dedifferentiation and metastasis, location of this enzyme shifts almost entirely from the nuclear compartment to the cytoplasmic compartment. These data indicate that non-toxic vitamin D precursors should be sufficient for CRC chemoprevention, but that neither vitamin D nor its precursors may be sufficient for CRC chemotherapy.

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.

Expression of vitamin D receptor and 25-hydroxyvitamin D3-1{alpha}-hydroxylase in normal and malignant human colon

Considerable evidence exists to support the use of vitamin D to prevent and/or treat colorectal cancer. However, the routine use of bioactive vitamin D, 1,25-dihydroxyvitamin D3, is limited by the side effect of toxic hypercalcemia. Recent studies, however, suggest that colonic epithelial cells express 25-hydroxyvitamin D3-1alpha-hydroxylase, an enzyme that converts nontoxic pro-vitamin D, 25-hydroxycholecalciferol [25(OH)D3], to its bioactive form. Yet, nothing is known as to the cellular expression of 1alpha-hydroxylase and the vitamin D receptor (VDR) in the earliest histopathologic structures associated with malignant transformation such as aberrant crypt foci (ACF) and polyps [addressing the possibility of using nontoxic 25(OH)D3 for chemoprevention], nor is anything known as to the expression of these proteins in colorectal cancer as a function of tumor cell differentiation or metastasis [relevant to using 25(OH)D3 for chemotherapy]. In this study, we show that 1alpha-hydroxylase is present at equal high levels in normal colonic epithelium as in ACFs, polyps, and colorectal cancer irrespective of tumor cell differentiation. In contrast, VDR levels were low in normal colonic epithelial cells; were increased in ACFs, polyps, and well-differentiated tumor cells; and then declined as a function of tumor cell de-differentiation. Both 1alpha-hydroxylase and VDR levels were negligible in tumor cells metastasizing to regional lymph nodes. Overall, these data support using 25(OH)D3 for colorectal cancer chemoprevention but suggest that pro-vitamin D is less likely to be useful for colorectal cancer chemotherapy.

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.

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.

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.

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.

In vivo observation of the ileal microadenoma in familial adenomatous polyposis

Microadenomas or aberrant crypt foci (ACFs) are regarded as early neoplastic lesions that precede the development of macroscopic adenomas. The aim of this study was to characterize surface features of ileal microadenomas in patients with familial adenomatous polyposis (FAP). Magnifying ileoscopy was performed in 19 patients with FAP. A histologically verified adenomatous tubule, the existence of which was suggested by magnified observation, was regarded as a microadenoma. Magnifying ileoscopy detected microadenoma in five patients. In four of the five cases, the ileal microadenomas were identified as areas with tiny crypt openings or serrated surfaces, which were distinctive of nonneoplastic, diminutive protrusions. Magnifying ileoscopy seems to be useful in the detection of ileal microadenomas.

Initial experience with a real-time video processor for enhancing endoscopic image contrast

BACKGROUND

An initial experience using a digital video processor to enhance contrast in endoscopic images in real-time is described.

METHODS

Endoscopic images were examined with a system using locally adaptive processing to balance variations in illumination and sharpen fine features in real-time. For comparison, indigo carmine dye, a popular exogenous contrast agent, was applied to one patient.

RESULTS

In general, contrast-enhanced images appeared to contain more mucosal detail, with reduced glare and features in shadowed areas revealed. When used in conjunction with indigo carmine, the enlarged crypt openings in an aberrant crypt focus were visible, the first such detection in vivo without the use of magnifying endoscopy.

CONCLUSIONS

Real-time video contrast enhancement during endoscopic procedures appears to provide excellent mucosal detail and improve contrast in a clinically useful manner.