Characterization of stereomicroscopically identified preneoplastic lesions during dimethylhydrazine-induced colonic carcinogenesis

Hesperetin alleviates DMH induced toxicity via suppressing oxidative stress and inflammation in the colon of Wistar rats

1,2-Dimethylhydrazine (DMH), a colon-specific environmental toxicant is one among the carcinogen responsible for the cause of colon cancer. The present study was designed to evaluate the protective effect of Hesperetin (HST) against colon toxicity induced by DMH in Wistar rats. HST, a flavonoid widely found in citrus fruits possesses several biological activities including anti-microbial, anti-oxidant properties among others. A single dose of DMH (40 mg/kg body weight) was administered subcutaneously on 1st day for induction of colon toxicity followed by oral treatment with HST at a dose of 20 mg/kg bodyweight for 14 consecutive days. DMH administration leads to excessive ROS generation, resulting in an imbalance in redox homeostasis and causing membrane lipid peroxidation, which is also partly due to the decrease in the level of tissue antioxidant machinery. Our result showed HST significantly ameliorates DMH-induced lipid peroxidation and also substantially increases the activity/level of various anti-oxidant proteins (GR, GPx, GST, GSH, and SOD). HST was also found to reduce the expression of inflammatory proteins (TNF-α, IL-6, i-NOS, COX-2, NF-kB-p65), goblet cell disintegration as well as mucin depletion (sulfo and sialomucin) in the colon that was found to be elevated upon administration of DMH. Our histological results further provide confirmation of the protective role of HST against DMH-induced pathological alterations. The results of the present study demonstrate supplementation of HST is beneficial in ameliorating DMH-induced toxicity by suppressing oxidative stress, inflammation, goblet cell disintegration as well mucin depletion in the colon of Wistar rats.

Quercetin ameliorates reactive oxygen species generation, inflammation, mucus depletion, goblet disintegration, and tumor multiplicity in colon cancer: Probable role of adenomatous polyposis coli, β-catenin

1,2 Dimethyl hydrazine (DMH), a cogent environmental toxicant, targets the colon. Previous reports suggest that DMH-mediated dysregulation of the Wnt/β-catenin pathway plays a vital role in the initial events of colon carcinogenesis. Our study was designed to investigate the effect of quercetin on DMH-mediated colon cancer by targeting adenomatous polyposis coli (APC) and β-catenin in Wistar rats. Animals were pretreated orally with quercetin at doses of either 25 or 50 mg/kg bodyweight (bw) and DMH at a dose of 20 mg/kg bw subcutaneously up to the 15th week and sacrificed after the 30th week. DMH administration leads to reactive oxygen species generation, resulting in an imbalance in redox homeostasis and causing membrane lipid peroxidation, which is also partly due to the decrease in the level of tissue antioxidant machinery. Increased inflammatory and proliferative proteins were observed in DMH-induced colon cancerous rats. DMH treatment also led to dysregulation in the apoptotic pathway with decreased Bax:Bcl-2 ratio. Quercetin pretreatment ameliorates DMH-induced proliferation, activities of detoxifying enzymes, and putative early markers (mucin depletion and goblet cell disintegration) in colonic tissue. It also significantly regulates APC and β-catenin expression and inhibits tumor incidence and multiplicity. Histological results further confirm the beneficial role of quercetin in averting DMH-induced pathological alterations.

Glycyrrhizic acid suppresses the development of precancerous lesions via regulating the hyperproliferation, inflammation, angiogenesis and apoptosis in the colon of Wistar rats

Background

Colon carcinogenesis is a multistep process and it emanates from a series of molecular and histopathological alterations. Glycyrrhizic acid (GA) is a natural and major pentacyclic triterpenoid glycoside of licorice roots extracts. It has several pharmacological and biological properties such as anti-inflammatory, anti-viral, and anti-cancer. In the present study, we investigated the chemopreventive potential of GA against 1,2-dimethyhydrazine (DMH)-induced precancerous lesions i.e., aberrant crypt foci (ACF) and mucin depleted foci (MDF), and its role in regulating the hyperproliferation, inflammation, angiogenesis and apoptosis in the colon of Wistar rats.

Methods

Animals were divided into 5 groups. In group III, IV and V, GA was administered at the dose of 15 mg/kg b. wt. orally while in group II, III and IV, DMH was administered subcutaneously in the groin at the dose of 20 mg/kg b.wt once a week for first 5 weeks and animals were euthanized after 9 weeks.

Results

GA supplementation suppressed the development of precancerous lesions and it also reduced the infiltration of mast cells, suppressed the immunostaining of Ki-67, NF-kB-p65, COX-2, iNOS and VEGF while enhanced the immunostaining of p53, connexin-43, caspase-9 and cleaved caspase-3. GA treatment significantly attenuated the level of TNF-α and it also reduced the depletion of the mucous layer as well as attenuated the shifting of sialomucin to sulphomucin.

Conclusion

Our findings suggest that GA has strong chemopreventive potential against DMH-induced colon carcinogenesis but further studies are warranted to elucidate the precise mechanism of action of GA.

Egg yolk proteins suppress azoxymethane-induced aberrant crypt foci formation and cell proliferation in the colon of rats

Dietary proteins can influence colonic carcinogenesis; some proteins have a promotional effect, whereas others exhibit a preventive effect. Dietary egg yolk proteins have been reported to suppress the expression of colon tumors in rats. In this study, we investigated the effect of consumption egg yolk proteins on cell proliferation in a rat model of azoxymethane (AOM)-induced colon cancer. We hypothesize, based on the literature of egg yolk protein actions, that they protect against colon tumor development. Therefore, male F344 rats were fed a purified AIN-93G diet containing either 20% casein (control) or 20% egg yolk proteins for 5 weeks. After 1 week on the experimental diet, the rats were administered weekly subcutaneous injections of saline or AOM for 2 weeks to induce aberrant crypt foci. Rats were administered an intraperitoneal injection of 5-bromo-2'-deoxyuridine 1 hour before being euthanized for examination of DNA synthesis in the colonic mucosa. The contents of the cecum were analyzed for the presence of short-chain fatty acids (SCFAs). In the AOM-injected rats, the yolk protein diet suppressed aberrant crypt foci formation and reduced the proliferative 5-bromo-2'-deoxyuridine-labeling index in the proximal colon when compared with the control diet. A significant increase in cecal SCFAs was observed in the rats that were fed egg yolk proteins. These results indicate that dietary egg yolk proteins have a preventive effect on AOM-induced large bowel carcinogenesis in rats; it exerts this effect by altering cell proliferation through SCFA production. This study suggests that the consumption of egg yolk proteins might be protective against colon carcinogenesis.

Tissue zinc levels in precancerous tissue in the gastrointestinal tract of azoxymethane (AOM)-treated rats

Alterations in tissue zinc levels have been documented in patients with gastrointestinal tract malignancies and more frequently, in those with colonic cancer. However, the precise role of tissue zinc in carcinogenesis is not well elucidated. This study, using a well-established colon cancer model in rats, was designed to investigate the relationship of tissue zinc to the carcinogenic process. The aim was to examine tissue zinc levels in the preneoplastic tissues and to study the changes that occur during transition of mucosa from normal to preneoplastic state. Six-week old rats were given a single dose subcutaneous injection of azoxymethane (AOM) (30mg/kg body weight) and sacrificed after 1, 2, 5, and 9 months of the treatment. Plasma zinc levels showed a significant decrease (p<0.05) at 9 months compared with controls. Tissue zinc levels showed a significant decrease in the large intestine at 1 and 2 months (p<0.05) and at 5 and 9 months (p<0.01), in the small intestine at 2, 5, and 9 months (p<0.05), and in the stomach at 5 and 9 months (p<0.05). The maximum percent decrease (45%) in tissue zinc was observed in the large intestine at 9 months. Tissue copper zinc super oxide dismutase (CuZnSOD) activity was assessed in the body of the stomach, small intestine, and large intestine and compared with the control group. There was a significant fall in CuZnSOD levels in the small intestine at 9 months (p<0.05) and in the large intestine at 5 and 9 months (p<0.01). Two of these six rats showed histological evidence of precancerous lesions in the mucosa of the colon. This study suggests that the decrease in plasma zinc, tissue zinc and activity of CuZnSOD is associated with development of preneoplastic lesions in the colonic mucosa.

Mitogenic effects of both amidated and glycine-extended gastrin-releasing peptide in defunctioned and azoxymethane-treated rat colon in vivo

Although there is abundant evidence that gastrin-releasing peptide acts as a mitogen in various carcinoma cell lines, the effect of administration of gastrin-releasing peptide on the colorectal mucosa in vivo has not been reported. The aims of this study were to determine whether continuous infusion of gastrin-releasing peptide stimulated proliferation or accelerated carcinogenesis in the rat gastrointestinal tract and other organs. The possible requirement for C-terminal amidation for mitogenic activity in vivo was also investigated. Proliferation was measured in the colon by metaphase index and by immunostaining for the proliferation marker Ki-67, and in other tissues by immunostaining alone. Acceleration of colorectal carcinogenesis was assessed by counting aberrant crypt foci after treatment with the carcinogen azoxymethane. Defunctioning of the rectum reduced both the proliferative index and the crypt height of the rectal mucosa of untreated rats. Treatment with amidated or glycine-extended gastrin-releasing peptide for 4 weeks using implanted mini-osmotic pumps resulted in a two- to three-fold increase in proliferation, and an increase in crypt height, in the defunctioned rectal mucosa (p<0.001), with smaller but significant increases in the caecum and distal colon. No changes in proliferation were detected in lung, pancreas or gastric mucosa. The numbers of aberrant crypt foci in the mid-colon, distal colon and rectum following treatment with azoxymethane were also significantly increased by infusion with amidated or glycine-extended gastrin-releasing peptide. We conclude that administration of gastrin-releasing peptide to mature rats stimulates proliferation and accelerates carcinogenesis in the colorectal mucosa, and that C-terminal amidation is not essential for either effect. Gastrin-releasing peptides could thus potentially act as promoters of colorectal carcinogenesis.

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.

Screening of stimulatory effects of dietary risk factors on mouse intestinal cell kinetics

AIM

Although epidemiological and experimental studies validate influence of genetic, environmental and dietary factors in the causation of various types of cancers including colon, results from all these sources are inconclusive. Hypothesizing that high fat diet and obesity are among the major predisposing factors in the incidence of colon cancer, we evaluated the role of diet constituted with food material derived from a tropical plant, Tamarindus indica Linn (TI).

METHODS

A two part randomized double-blind study was conducted employing inbred Swiss albino mice from a single generation for the whole investigation. One day-old neonates (n = 12) were subcutaneously administered with monosodium glutamate (MSG) to induce obesity (OB). At weaning these animals were maintained on modified AIN-76 diet supplemented with 10% TI and 10% fat bolus (w/w, TIFB) for 8 wk. Subsequently, in the second part of study, four groups of animals belonging to the same generation, age and gender (n = 12 per group), were maintained on: AIN-76 control diet (CD); AIN-76 mixed with 10% TI extract (TI); and, mixed with 10% TI and 10% FB (TIFB) for 8 wk, to determine intestinal crypt cell proliferation, functionally-specific enzyme activities, fermentation profile, and energy preferences.

RESULTS

We observed a significant increase in the crypt cell production rate in distal colonic segment of experimental animals when compared with the controls. This segment also contained significantly low butyrate levels compared to control and TIFB groups. All the experimental groups showed a gross decrease in the enzyme activities viz., succinate dehydrogenase, acid-galactosidase and dipeptidyl amino peptidase IV demonstrating pathological stress caused by the test regimens, and an altered metabolic flux in the cellular environment.

CONCLUSION

We have demonstrated a cumulative response to the three dietary factors, one of which (TI) is reported, herein, for the first time to modulate kinetics of large intestinal mucosa, contributing to total risk posed by these test agents.

Histological and immunohistochemical observations of mucin-depleted foci (MDF) stained with Alcian blue, in rat colon carcinogenesis induced with 1,2-dimethylhydrazine dihydrochloride

The usefulness of mucin-depleted foci (MDF), which have recently been proposed as a new preneoplastic biomarker in rat colon carcinogenesis, was histologically investigated in rat colonic tissues treated with 1,2-dimethylhydrazine dihydrochloride (DMH). The relationship among aberrant crypt foci (ACF), MDF and beta-catenin accumulated crypts (BCAC) was examined by comparing the corresponding computer-captured images. Twelve male F344 rats were given DMH s.c. at a dose of 40 mg/kg body weight, once a week for 2 weeks, and randomly divided into two groups. Rats in group 1 were given normal drinking water, while those in group 2 were given drinking water containing indomethacin (IND) at 16 ppm for 6 weeks. All animals were sacrificed 8 weeks after the first DMH treatment. The resected colons were fixed in 10% formalin, and stained with Alcian blue for observation of ACF and MDF. Histological and immunohistochemical analysis revealed that the numbers of ACF, MDF and overlapping lesions in group 2 (treated with IND) were significantly decreased, compared with those in group 1. The number of BCAC in group 2 was also significantly lower than that in group 1. The reduction (61.5%) of MDF by IND was much greater than that (29.3%) of ACF. Analyses of the computer-captured images indicated that MDF had more frequent dysplastic changes and overexpression of beta-catenin than did ACF. MDF having over 4 crypts or MDF with the appearance of ACF corresponded well to BCAC. These results suggest that MDF may be useful as an early biomarker in colon carcinogenesis.

Evaluation of co-stimulatory effects of Tamarindus indica L. on MNU-induced colonic cell proliferation

Colonic cell proliferation is the prerequisite for the genesis of cancer. Experimental and epidemiologic evidence indicate dietary factors to be one of the commonest predisposing factors in the development of several types of cancers including large intestine. Here we have investigated the role of the fruit pulp of Tamarindus indica L. (TI), a tropical plant-derived food material, on the proliferating colonic mucosa using Swiss albino mice. Crypt cell proliferation rate (CCPR), on histological basis and [3H]-thymidine incorporation assay were chosen to evaluate the modulating potential of TI per se and in response to a subacute dose of N-nitroso N'-methyl urea (MNU). Descending colonic segment showed greater rate of cell proliferation than the ascending colon and cecum tissues isolated from the group 2 (TI-per se) when compared with group 1 (negative controls). It also revealed a positive correlation with the incorporation studies. Significant increase in the CCPR and radiolabeled precursor incorporation (p <0.001) was observed in MNU-induced+TI fed group of animals (group 4) in all the three segments when compared with control diet fed normal (group 1) as well as MNU-induced (group 3) animals. This study therefore indicates a co-stimulatory effect of TI on MNU-induced colonic cell kinetics.

Different effects of short- and long-chained fructans on large intestinal physiology and carcinogen-induced aberrant crypt foci in rats

Inulin-type fructans, which are nondigestible carbohydrates, have been shown to modulate the number of induced preneoplastic lesions in the colon as well as the colonic microflora in laboratory animals. The present study was designed to investigate the effect of a short- and long-chained inulin-type fructan on 1,2-dimethylhydrazine dihydrochloride-induced aberrant crypt foci (ACF) in the rat colon. In addition, the present study investigated the influence of chain length, dietary level (5% or 15%), and duration of feeding (5 or 10 wk) on the following intestinal parameters supposed to be involved in the development of ACF: microflora, short-chain fatty acids, pH, and cell proliferation. A 3-wk pretreatment period with both fructans was included. Feeding the long-chained fructan (5% or 15%) significantly inhibited the numbers of small and total ACF after 5 and 10 wk. The short-chained fructan (15%) inhibited the number of small and total ACF after 5 and 10 wk but significantly increased the numbers of medium and large ACF after 10 wk. In conclusion, the effect on ACF outcome was influenced by the chain length of the fructans.

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.

Short term infusion of glycine-extended gastrin(17) stimulates both proliferation and formation of aberrant crypt foci in rat colonic mucosa

Evidence is accumulating that gastrin precursors may act as growth factors for the colonic mucosa in vivo and for colorectal carcinoma cell lines in vitro. The effect of short term administration of synthetic gastrins on the colonic mucosa in vivo, however, has not been reported. The aim of our study was to determine whether continuous systemic infusion of glycine-extended gastrin(17) stimulated proliferation and accelerated carcinogenesis in the colorectal mucosa. A significant increase in colonic mucosal proliferation as assessed by metaphase index was seen in the caecum (23%, p < 0.02) and distal colon (27%, p < 0.001), but not the rectum, after treatment of intact rats with glycine-extended gastrin(17) for 1 week using implanted miniosmotic pumps. Defunctioning of the rectum reduced both the proliferative index and crypt height of the rectal mucosa of untreated rats. Treatment of rectally defunctioned animals with glycine-extended gastrin(17) for either 1 or 4 weeks resulted in a significant increase in both the proliferative index (40% and 93%, respectively) and crypt height (11% and 19%, respectively) of the rectal mucosa. The total number of aberrant crypt foci in intact rats treated with the procarcinogen azoxymethane plus glycine-extended gastrin(17) was increased by 48% compared to the value in controls treated with azoxymethane only (p = 0.01). We conclude that short term administration of glycine-extended gastrin(17) to mature rats not only has a proliferative effect upon colonic mucosa, but also increases the number of aberrant crypt foci formed in the colorectal mucosa after treatment with azoxymethane. Glycine-extended gastrin(17) could thus potentially act as a promoter of carcinogenesis.

The influence of simple sugars and starch given during pre- or post-initiation on aberrant crypt foci in rat colon

The aim of the present study was to investigate the enhancing effect of dietary sugar on the development of aberrant crypt foci (ACF) in male F344 rats initiated with azoxymethane (AOM). The potential role of sugar as either a co-initiator or a promoter was investigated by giving diets high in sucrose and dextrin (61%) during either the pre-initiation, the initiation, and/or the post-initiation stage of the ACF development. The colonic cell proliferation, activity of colonic phase II enzymes, and a biomarker of lipid peroxidation were additionally examined in order to obtain information on the specific mechanisms involved in the suggested effect of sucrose and dextrin on ACF development. The number of large sized and the total number of ACF were significantly increased by feeding sucrose and dextrin in the post-initiation period. No positive association between colonic cell proliferation and ACF was seen. The level of oxidative stress in the cytosol from the proximal colon and colonic glutathione transferase and quinone reductase was not affected by the sugar treatments. The overall results from this study show that sucrose and dextrin enhance the number of preneoplastic lesions in AOM-initiated rats, and act primarily as promoters in the development of ACF.

Sialomucin production in aberrant crypt foci relates to degree of dysplasia and rate of cell proliferation

Aberrant crypt foci (ACF) are putative early preneoplastic lesions of colon cancer. To date, many different ACF parameters have been measured as indicators of degree of colon cancer risk. It has been suggested that ACF producing sialomucins (SIM) may be more advanced types of ACF than those producing sulphomucins (SUM), but little data are available to support this. The objective of this experiment was to see if SIM ACF, as observed in whole mount colons, are different from other ACF and surrounding normal colonic crypts in terms of their rate of cell proliferation and degree of dysplasia. Results showed that all ACF had a higher rate of cell proliferation than normal crypts and that SIM ACF had higher cell proliferation in the top regions of the crypt, higher phih index of cell proliferation, higher degree of dysplasia, greater size and increased degree of luminal alterations than SUM ACF. We conclude that SIM ACF, as observed in whole mount colons, have more alterations and are more advanced towards tumorigenesis than SUM ACF and may be a better predictor of colon cancer risk than other measures of ACF.

A mucinous histochemical study on malignancy of aberrant crypt foci (ACF) in rat colon

The relationship between malignancy and number of crypts (crypt multiplicity) comprising aberrant crypt foci (ACF) was investigated, by studying changes in the mucous nature of ACF with 5 crypts or less, ACF with 6-13 crypts, adenomas and invasive adenocarcinomas induced by 1,2-dimethylhydrazine in distal colon of rats. A paradoxical Con A-staining was performed for goblet cell mucins. Of the sulfomucin-dominant ACF with 1-3 crypts, 82.6% had labile class III mucin, similar to the distal colon in the normal rats. However, in most of the goblet cell mucin produced by the ACF with 4-5 crypts with an indicated relation to colorectal carcinoma or the sialomucin (SiM) -dominant ACF with 1-3 crypts, mucin types other than class I were rarely present. The incidence of class I mucin decreased with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the lowest incidence of 40% in adenocarcinomas. In contrast, the incidence of class II mucin increased markedly with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the highest incidence in adenocarcinomas (95%). The ACF with 6-13 crypts had a mucous profile similar to that of adenomas. These results suggested that malignancy of ACF related to the crypt multiplicity. In the ACF with 1-3 crypts, SiM-dominant ACF had the potential to progress to malignant lesions.

The effect of synbiotics on colon carcinogenesis in rats

Evidence indicates that consumption of probiotic microorganisms such as bifidobacteria reduces the risk of colon cancer in animal models. Feeding certain fructans such as oligofructose and inulin, which are thought to selectively increase the growth of intestinal bifidobacteria (i.e., a prebiotic effect), also has been shown to reduce colon cancer risk. The objective of our study was twofold, i. e., to determine whether the combination of bifidobacteria and oligofructose would have an additive effect (i.e., synbiotic) in reducing colon cancer risk in rats, and to determine whether other oligosaccharides would also be effective as part of a synbiotic combination. The development of colonic preneoplastic lesions (aberrant crypts) was used as an index of colon cancer risk. In one series of experiments, rats were given the carcinogen 1, 2-dimethylhydrazine (DMH) and administered one of the following treatments: skim milk (control), bifidobacteria (bifido), oligofructose (OF) or bifido + OF. Neither bifido nor OF alone significantly reduced aberrant crypt number. Bifido + OF reduced aberrant crypt number in five of six experiments, although the reduction was significant in only one. However, a paired comparison of the six experiments indicated a significant overall reduction in aberrant crypts by bifido + OF (P = 0.039). Soybean oligosaccharide (SBO) and wheat bran oligosaccharide (WBO) were also fed in combination with bifidobacteria. In two other experiments, SBO did not alter the number of aberrant crypts compared with the control, whereas WBO reduced aberrant crypt number in one experiment but not in another. Of OF, SBO and WBO, only SBO reduced the colonic mucosa proliferation compared with the control. These results suggest that the combination of bifidobacteria and oligofructose reduces colon cancer risk in carcinogen-treated rats, but the effect of other oligosaccharides is uncertain.

Relationship between the nature of mucus and crypt multiplicity in aberrant crypt foci in the rat colon

Aberrant crypt foci (ACF) induced in the distal colon of F344 male rats, 4, 8, 12 and 35 weeks after the first administration of 1, 2-dimethylhydrazine-2HCl (DMH) were examined to determine whether a correlation exists between the nature of goblet cell mucin and the number of crypts (crypt multiplicity) comprising the ACF. According to the ACF score calculated from the results of the qualitative observation of sulfomucins (SuMs) and sialomucins (SiMs), the ACF in the 4th week showed a weak correlation between the nature of the mucus and crypt multiplicity, and the ACF of each class showed similar mucous profiles. From the 8th week, a significant difference (P < 0.01) was recognized between the ACF consisting of 3 crypts or less and those consisting of 4 crypts or more. The proportion of crypts with SiM predominance showed a decrease in the 8th week in the ACF consisting of 1 crypt and in the 12th week in the ACF consisting of 2 or 3 crypts, implying a recovery tendency. The ACF consisting of more than 4 crypts showed little change over time, retaining the tendency of SiM predominance. Ulex europaeus agglutinin-I (UEA-I) lectin-positive crypts appeared in the ACF. This finding was significantly more prominent (P < 0.001) in the ACF with SiM predominance than in the ACF with SuM predominance at each experimental period, and in the 12th week after the first administration of DMH, the incidence of ACF with UEA-I-reactive mucin was decreased in the ACF groups consisting of 3 crypts or less, compared with the ACF groups consisting of 4 or more crypts. These results suggest that the biological quality of mucus in ACF consisting of 4 or more crypts is different from that in ACF consisting of 3 crypts or less. This difference should be considered when ACF are used as an intermediate biomarker of colon cancer.

Sulindac and indomethacin inhibit formation of aberrant crypt foci in the colons of dimethyl hydrazine treated rats

Aberrant crypt foci are microscopic lesions found in the colons of rodents treated with carcinogens, and in patients with premalignant colorectal conditions. They consist of single or multiple abnormal crypts and show cellular changes ranging from dysplasia to microscopic adenomacarcinoma. It is thought that these lesions represent the initial stages of the adenomacarcinoma path that results in the development of colorectal neoplasia. We have examined the effect of sulindac and indomethacin on the formation of aberrant crypt foci in rats treated with dimethylhydrazine (DMH). Aberrant crypt foci were induced in male Sprague-Dawley rats with two oral doses of dimethyl hydrazine at 25 mg/kg per dose. Rats were randomized to receive sulindac at 3 mg/kg (n = 20) or 10 mg/kg (n = 18) b.d., indomethacin at 1 mg/kg per day (n = 18) or 2 mg/kg per day (n = 19) or control (n = 37). Drug treatment was started on the day following the first dose of carcinogen and continued for 3 weeks. Colons were fixed flat overnight in 10% formalin and stained with 0.2%. Methylene Blue solution before being studied. There was a significant reduction in the number of aberrant crypt foci in rats treated with 10 mg/kg b.d., sulindac (P = 0.001) and indomethacin at 2 mg/kg per day (P = 0.0002). Sulindac, at 3 mg/kg b.d., and indomethacin, at 1 mg/kg per day, did not have a statistically significant effect (P = 0.089 and P = 0.052, respectively). None of the drug treatments affected the relative frequency of single crypt vs multiple crypt foci. Previous studies have shown that sulindac and indomethacin will significantly inhibit the growth and development of tumours in DMH treated rats. The current data suggest that one of the pathways of action of NSAID is to inhibit the formation of early preneoplastic lesions.

Role of aberrant crypt foci in understanding the pathogenesis of colon cancer

Aberrant crypt foci (ACF) are present in carcinogen treated rodent colons and in the colons of humans with a high risk for developing the disease. It is proposed that ACF are preneoplastic lesions. Quantification of the number and growth features of ACF has been employed to study modulators of colon carcinogenesis. In this review, examples are presented to support the concept that ACF are preneoplastic lesions and that sequential quantification of their number and growth features (crypt multiplicity) in animal colons may provide further insight into the pathogenesis of colon cancer. It is proposed that cellular and molecular heterogeneity among ACF with different growth and morphologic features will be invaluable in the identification of events critically associated with cancer development.

Characterisation of aberrant crypt foci in carcinogen-treated rats: association with intestinal carcinogenesis

Carcinogen-treated rats develop foci of aberrant crypts in the colon (ACFs) that have been interpreted as preneoplastic lesions. To characterise ACFs further, we studied in the unsectioned colon of rats the number, multiplicity, some morphological characteristics and the type of mucin production in ACFs. In ACFs observed 115 days after the administration of 50 mg kg-1 1,2-dimethylhydrazine (DMH), crypt multiplicity [number of aberrant crypts (AC) per focus] was positively correlated (P < 0.0001) with the reduction of goblet cells, and with luminal and nuclear alterations in the cells surrounding the lumen of the ACs. We studied mucin production in the unsectioned colon, demonstrating that ACFs producing sulphomucins (like the normal distal rat colon) were progressively reduced when ACF multiplicity increased, whereas ACFs containing sialomucins (correlated with an increased risk of colon cancer) or both sulphomucins and sialomucins increased with crypt multiplicity. We also studied ACFs in the colon and the occurrence of intestinal tumours in rats treated with azoxymethane (AOM; 64 mg kg-1). A significant association was found (P = 0.04) between tumours and the presence of 'large' ACFs (AC/ACF > 14 crypts) and a borderline significant association (P = 0.057) between the presence of tumours and sialomucin-producing ACFs. We found no association between the number of ACFs, ACF multiplicity and the presence of tumours.

Aberrant crypt foci and colon tumors in F344 rats have similar increases in proliferative activity

Increased proliferative activity has been described frequently in the colons of animals treated with colon carcinogens and of patients at increased risk of colon cancer; it has been proposed as an intermediate biomarker of colon cancer. Aberrant crypt foci, microscopic lesions identified in whole-mount preparations of colons, are thought to be putative pre-neoplastic lesions. The present studies were carried out to evaluate the proliferative activity of aberrant crypt foci at several different time periods, and of tumors after a single dose of azoxymethane (AOM) in F344 rats. Rats were injected with 5-bromo-2'-deoxyuridine (BUdR) 1 hr before killing. Aberrant crypt foci and tumors were identified and marked in the whole-mount specimens, embedded in glycol methacrylate, and evaluated for histochemically demonstrable hexosaminidase activity. Hexosaminidase is known to be altered in over 95% of aberrant crypt foci. Serial sections were evaluated for BUdR incorporation immunohistochemically with a monoclonal antibody. The mean proliferative activity of aberrant crypt foci in the distal colons was found to be increased 3- to 4-fold over that of the adjacent normal crypts at every time period analyzed (4 to 36 weeks) and was comparable to that seen in benign and malignant colon tumors in the same animals. The observed increase in proliferative activity further supports the hypothesis that aberrant crypt foci are putative pre-neoplastic lesions. Similar aberrant crypt foci, identified in human colons at increased risk of colon cancer, may provide important biomarkers for this common human cancer.

Influence of a dietary fiber on development of dimethylhydrazine-induced aberrant crypt foci and colon tumor incidence in Wistar rats

Formation of aberrant crypt foci (ACF) in archived colon tissue from animals in a previous study was examined. The animals were fed a semisynthetic casein-based diet in which the carbohydrate pool was substituted with a dietary beet fiber (Fibeta) as the only source of fiber. Oral doses of dimethylhydrazine dihydrochloride (DMH-2HCl, 20 mg/kg body wt) once a week for 10 weeks were used as initiator. The rats were fed different levels of the fiber in a preinitiation period, during initiation, or in a postinitiation period. In general, the results showed a statistically significant inverse relation between duration of intake of high-fiber diet and number of animals with ACF, as well as the total number of ACF and number of small ACF (1-3 crypts) per affected animal. The previously reported data showed no protective effect of the dietary fiber at any stage of the colorectal carcinogenic process. The lack of correlation between the outcome of ACF and tumors could be related to the observation that statistically significant differences between groups were seen only in the total number of ACF and number of small ACF. The hypothesis that ACF are preneoplastic lesions needs to be supported by further experimental data. The present state of knowledge could indicate that ACF represent true preneoplastic lesions progressing into colon tumors or that ACF and colon tumors represent two parallel independent events as a consequence of the cancer initiation (i.e., the ACF not being preneoplastic lesions per se).

Stereomicroscopic examination of surface morphology in colorectal epithelial tumors

The mucosal surface structure of epithelial neoplasms in the large intestine was examined by a stereomicroscope, and the correlation between histologic and macroscopic features was studied. The surface structure of the colonic mucosa could be readily and clearly observed using the stereomicroscope after superficial staining, and neoplastic lesions were identified as well-defined foci of the unique structures that were conspicuously different from those in the normal mucosa. Five hundred two adenomas and 159 carcinomas were examined and divided into five types according to stereomicroscopic appearance: long ellipsoid (359 lesions), cerebriform (141 lesions), leaf-like (16 lesions), dense tiny pits (89 lesions), and devastated (56 lesions). In the first three types benign adenomas predominated in the majority of cases (94.7%, 72.3%, and 68.8%, respectively) and the variation in the surface features correlated well with the histologic types. In the latter two types the frequency of malignancy was strikingly high (49.4% and 92.9%, respectively), with the devastated mucosal appearance being highly indicative of invasive carcinoma. Macroscopically, exophytic polypoid configurations were frequently found in the first three types, whereas flat nonpolypoid configurations predominated in the cases with dense tiny pits. Our results indicate that there is a close relationship between the surface structure of epithelial neoplasms in the large intestine and their histologic features and growth patterns.

Aberrant crypts in human colonic mucosa: putative preneoplastic lesions

Aberrant crypts are recognized in methylene blue-stained, unsectioned, colonic mucosa by their increased size, elliptical lumenal opening, thicker epithelial layer, and increased pericryptal region. Aberrant crypt foci in rodents are observed as early as 2 weeks and for at least 9 months after a single dose of carcinogen, have a distribution that parallels that of tumors, and have an increased number of aberrant crypts per focus with time after the carcinogen dose. The ability to quantify these lesions in the entire colon of rodents in less than an hour suggests that aberrant crypts may provide a highly efficient in vivo bioassay for colon carcinogens. Since aberrant crypt foci appear to be the earliest identifiable putative precursors of colon cancer, they represent lesions that can be characterized further for the earliest genetic and biochemical alterations. In F344 rats, we have demonstrated that aberrant crypts have multiple histochemically-detectable enzyme alterations. Using similar techniques, we were the first to demonstrate aberrant crypts in unsectioned human mucosa. After embedding and sectioning, these microscopic aberrant crypts resemble rare lesions described earlier in the literature after extensive serial sectioning. In rats and humans, aberrant crypts may be histologically normal or display varying degrees of dysplasia and histochemically-detectable altered enzyme activities. These putative, preneoplastic lesions should reveal early changes that precede colon cancer and ways to alter their progression.

Dietary cholesterol enhances preneoplastic aberrant crypt formation and alters cell proliferation in the murine colon treated with azoxymethane

The effect of dietary cholesterol on the development of colonic preneoplastic aberrant crypts, as well as its influence on the proliferative status of the intestinal epithelium, was investigated in mice exposed to the chemical carcinogen azoxymethane. Two strains of mice, C57BL/6J and BALB/cJ, were fed a semisynthetic diet containing 0% (control), 1.25%, or 5.00% cholesterol for eight weeks. During the first four weeks of the experiment, mice were given weekly injections of azoxymethane. Cholesterol supplementation significantly increased the formation of aberrant crypts (p less than 0.0001), enhanced the rate of cell proliferation (p less than 0.0001), altered the cell proliferative pattern, and increased crypt height (p less than 0.05) and the total number of cells per crypt (p less than 0.01) in the colonic epithelium of both mouse strains. C57BL/6J mice developed a greater number of aberrant crypts (p less than 0.0001). However, a diet-strain interaction was not observed. The results of this study indicate that dietary cholesterol enhances colon carcinogenesis in the murine colon and therefore may be an important factor in the etiology of large bowel cancer in humans.