Prevention by retinoids of azoxymethane-induced tumors and aberrant crypt foci and their modulation of cell proliferation in the colon of rats

Retinoids are proposed chemopreventive agents that inhibit cell proliferation and induce differentiation. Their ability to prevent azoxymethane (AOM)-induced aberrant crypt foci (ACF) and tumors and to modulate cell proliferation was investigated in the colon of male F344 rats. Thirteen retinoids were evaluated for prevention of ACF and two of them, 9-cis-retinoic acid (RA) and 4-(hydroxyphenyl)retinamide (4- HPR), were also evaluated for prevention of colon cancer. The retinoids were administered continuously in the diet starting 1 week prior to the first of two weekly 15 mg/kg i.p. injections of AOM and for a total of either 5 or 36 weeks in order to evaluate their effect on colonic ACF and tumors. At a concentration of 1 mmol/kg diet, 2- (carboxyphenyl)retinamide caused the greatest reduction (57.7%) in the yield of ACF. 9-cis-RA was toxic at 1 mmol/kg so that it was evaluated at 0.1 mmol/kg, resulting in a 41.6% reduction in ACF. The ability of the retinoids to reduce the proliferating cell nuclear antigen (PCNA) labeling index in ACF and in non-involved crypts correlated with their ability to prevent ACF. Both 9-cis-RA (0.1 and 0.2 mmol/kg diet) and 4- HPR (1 and 2 mmol/kg diet) were highly effective in decreasing the yield of AOM-induced colon tumors. In summary, retinoids were demonstrated to reduce cell proliferation and to prevent ACF and tumors in the colon, suggesting promise as preventive agents for colon cancer.      

Colonic cell proliferation, apoptosis and aberrant crypt foci development in rats given 2-amino-3-methylimidaz.

Sodium-copper chlorophyllin (CHL) inhibits the formation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)- and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced colonic aberrant crypt foci (ACF) and tumours in the F344 rat when it is given simultaneously with either carcinogen. However, CHL reportedly increased the incidence of dimethylhydrazine (DMH)-induced colon tumours in the same species when administered post-initiation. In the present study, rats were given IQ (130 mg/kg body weight, by oral gavages on alternating days) for 2 weeks, starting in experiment week 3, and one week after the final IQ dose rats received CHL treatment until the study was terminated at 16 weeks. Compared with animals given carcinogen alone, the mean number of IQ-induced ACF per colon was reduced significantly by 1% (w/v) CHL in the drinking water (P < 0.05), whereas 0.1% and 0.01% CHL had no effect. These CHL concentrations increased in a dose-related manner both the terminal deoxynucleotidyl transferase-mediated nick end labelling (TUNEL) and bromodeoxyuridine (BrdU) labelling indices in the distal colon. However, the lowest concentration tested, 0.001% CHL, increased the mean number of IQ-induced ACF per colon (P < 0.05), and increased the BrdU labelling index without a concomitant change in TUNEL. These studies indicated that 0.001% CHL promoted IQ-ACF due to deregulation of the homeostatic balance between cell birth and apoptosis in the colonic mucosa, whereas higher concentrations of CHL had either no effect or protected against IQ-induced ACF by causing dose-related increases in the overall rate of cell turnover in the colon.     

SHORT COMMUNICATION: Piroxicam-induced regression of azoxymethane-induced aberrant crypt foci and prevention of colon cancer in rats

Piroxicam has been shown to prevent azoxymethane (AOM)-inducedaberrant crypt foci and colon cancer in rats. In this communicationwe evaluate whether piroxicam can also cause regression of precancerouslesions identified as aberrant crypt foci, thus preventing theoccurrence of cancer. Male Fischer-344 rats were administered0.125g/kg piroxicam in theirdiet starting either 1 week priorto or 12 weeks after a single subcutaneous injection of AOM(30 mg/kg body wt). The yield of aberrant crypt foci and ofcolon adenomas and adenocarcinomas was determined at 5, 12,27 and 37 weeks after administering the AOM respectively. Whenpiroxicam was administered starting 1 week prior to AOM theyield of aberrant crypt foci at the three initial time pointswas reduced. When the administration of piroxicam was delayeduntil 12 weeks afterAOM the yield of aberrant crypt foci wasreduced from 53.8±8.1 foci/colon at 12 weeks to 11.1±2.0at 27 weeks. At 37 weeks after administering AOM the yield ofcolon tumors was 0.59±0.11 tumors/animal, while in ratsadministered piroxicam beginning either 1 week prior to or 12weeks after AOM the yield was similarly reduced to 0.14±0.07and 0.17±0.07 tumors/animal respectively. Thus piroxicamwas demonstrated not only to prevent, but also to cause regressionof aberrant crypt foci, both of which were associated with theprevention of colon tumors.     

Polyethylene-glycol suppresses colon cancer and causes dose-dependent regression of azoxymethane-induced aberrant crypt foci in rats.

Dietary polyethylene-glycol (PEG) 8000, a nonfermented polymer laxative, strongly suppresses azoxymethane-induced aberrant crypt foci (ACF) in the colon of rats, as shown in a previous study (D. E. Corpet et al., Carcinogenesis (Lond.), 20: 915-918, 1999). In the present study, we tested the effect of PEG administered during either initiation or postinitiation, the dose-response effect of PEG, the regressive effect of PEG on established ACF, and the preventive effect of PEG on colon cancers in rats. The general design was to initiate carcinogenesis in F344 rats by a single injection of azoxymethane (20 mg/kg) and to randomize the animals 7 days later to AIN-76 diets containing 5% PEG or no PEG (control). At termination, ACF and tumors were scored blindly by a single observer. The administration of 5% PEG for 32 days to groups of 10 female rats in either food or drinking water reduced the number of ACF by a factor of 8 (P = 0.0002) and reduced the number of large ACF by a factor of 20-30 (P = 0.002). No protection was afforded when PEG was given only during the initiation phase. Diets containing 0%, 0.5%, 2%, or 5% PEG fed for 35 days to four groups of male rats inhibited ACF in a dose-dependent manner (P < 0.0001). The administration of a 5% PEG diet for 41 days, starting 42 days after carcinogen injection, led to a 73% decrease in the number of ACF (P < 0.0001). Dietary PEG thus caused the regression of established ACF. Macroscopic tumors were evaluated by histology in rats that had been fed a high-fat diet containing cooked casein to promote tumor growth for 81 days. In this accelerated model of carcinogenesis, dietary PEG suppressed the occurrence of colon adenomas and carcinomas: the incidence of tumors decreased from 70% to 10% (P = 0.005); and the multiplicity decreased from 2.1 to 0.1 tumor(s)/rat (P = 0.003). No cancer was detected in the PEG-fed rats. Taken together, these results suggest that PEG could be a potent anticancer agent in the postinitiation phase of carcinogenesis. Because PEG is a substance that is generally recognized as safe (GRAS list, Food and Drug Administration), its cancer-preventive features could be tested in humans.     

Microsatellite instability in aberrant crypt foci from patients without concurrent colon cancer

Aberrant crypt foci (ACF) are microscopic surface abnormalities that are putative precursors to colorectal cancer (CRC). ACF exhibit similar histological and molecular abnormalities to adenomas and CRC and potentially represent useful biomarkers of cancer risk. Microsatellite instability (MSI) is one molecular abnormality identified in concurrent ACF from CRC patients that may indicate a risk for progression. To determine if MSI can be detected in ACF from cancer-free subjects, we examined 45 ACF from 20 subjects undergoing colonoscopies. The group included 12 patients at elevated risk for CRC based on family history of CRC or personal history of CRC or advanced adenoma and 8 patients with no known risk factors. ACF were identified using close-focus magnifying chromendoscopy and collected by biopsy in situ. Genomic DNA was prepared from ACF and adjacent normal colonic epithelium isolated by laser capture microdissection and analyzed for MSI. MSI was identified in at least one marker from 9 of 30 (30%) lesions from patients at elevated risk for CRC and in 2 of 15 (13%) lesions from average risk patients. Using methylation-specific PCR analysis, we also examined the ACF for promoter hypermethylation of the DNA repair genes hMLH1 and MGMT and found moderate changes (8/39 and 3/32, respectively). Although we found only a limited relationship between hMLH1 hypermethylation and MSI, all the lesions with MGMT hypermethylation displayed an MSI-low phenotype. These lesions may be precursors to MSI-low CRC, providing a potential early biomarker to assess the effects of cancer prevention strategies.     

Chemoprevention of aberrant crypt foci in the colon of rats by dietary onion

Onion intake might reduce the risk of colorectal cancer, according to epidemiology. However, Femia showed in 2003 that diets with a 20% onion intake increase carcinogenesis in rats. We speculated this dose was too high. Prevention of initiation was thus tested in 60 rats given a 5% dried onion diet or AIN76 diet, and initiated 12 days later with azoxymethane (AOM, 1x20 mg/kg i.p.), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ, 2x200 mg/kg p.o.), or N-nitroso-N-methylurea (2x50 mg/kg p.o.). Prevention of promotion was tested in 38 rats given AOM, then randomised to: AIN76 diet; 5% onion diet; phytochemicals diet (supplemented with propyl-disulfide, quercetine-glycosides and oligofructose); 1% pluronic F68 diet (a potent chemopreventive PEG-like block-polymer, used as a positive control). Aberrant crypt foci (ACF) were scored 30 days (initiation) or 100 days (promotion) after carcinogen injection. The onion diet given during initiation reduced the number of AOM-induced ACF (60 versus 86, p=0.03), and the size of IQ-induced ACF (1.33 versus 1.97, p=0.02). Given post-initiation, the onion diet reduced the number of ACF (34 versus 59, p=0.008) and of large ACF (6 versus 15, p=0.02). Phytochemicals diet and pluronic diet reduced ACF growth similarly. Data show that a 5% onion diet reduced carcinogenesis during initiation and promotion stages, and suggest this chemoprevention is due to known phytochemicals.     

Reovirus decreases azoxymethane-induced aberrant crypt foci and colon cancer in a rodent model

Reovirus type 3 Dearing has demonstrated oncolytic efficacy in vitro and in vivo against a variety of cancer cell lines, tumor xenografts and syngeneic cancer models. In this study, we investigated the effectiveness of reovirus against aberrant crypt foci (ACF) and colon cancer induced by the carcinogen azoxymethane (AOM) in an immunocompetent rat model. Sprague-Dawley rats received 15 mg/kg AOM intraperitoneally once per week for 4 weeks and reovirus was administered rectally once a week for 5 weeks starting 20 weeks after the last dose of AOM. Two weeks after completion of reovirus therapy, animals were examined for tumor burden in the colon and other tissues. Reovirus-treated animals showed a decrease in total ACF numbers (P=0.014), in large ACFs (P=0.0069) and in tumor number (P=0.03) compared to vehicle-treated animals. Fewer obstructing tumors in the colon (P=0.07) and duodenum (P=0.03) and reduced hepatic metastases were also noted. In addition, a tumor cell line derived from hepatic metastases was found to be susceptible to reovirus in vitro. Our results show that repeated rectal reovirus administration had some efficacy in the treatment and prevention of AOM-induced ACFs, colon cancers and metastases.     

Effect of selenomethionine on N-methylnitronitrosoguanidine-induced colonic aberrant crypt foci in rats.

An association between low selenium intake and the incidence or prevalence of cancers is well known. Selenium in the form of selenomethionine supplemented in drinking water has been found to be highly effective in reducing tumour incidence and preneoplastic foci during the development of hepatocarcinogenesis in rats in our previous studies. Here, an attempt has been made to investigate whether the dose and form of selenium found to be effective during hepatocarcinogenesis is equally effective in N-methylnitronitrosoguanidine-induced colorectal carcinogenesis in terms of antioxidant defence enzyme systems, DNA chain breaks and incidences of aberrant crypt foci. Treatment with selenomethionine either on initiation or on selection/promotion, or during the entire experiment showed that selenomethionine was most effective in regulating the cellular antioxidant defence systems, DNA chain break control and reducing aberrant crypt foci in the colorectal tissues of rats. Our results also confirm that selenium is particularly effective in limiting the action of the carcinogen during the initiation phase of this colorectal carcinogenesis, just as we found with hepatocarcinogenesis in our previous studies.     

Effect of dietary galacto-oligosaccharides on azoxymethane-induced aberrant crypt foci and colorectal cancer in Fischer 344 rats

The aim of the present study was to investigate the effects of galacto-oligosaccharides (GOS, Elix'or) on the development of aberrant crypt foci (ACF) and colorectal tumours in rats treated with azoxymethane (AOM). Two groups of 102 male Fischer 344 rats were injected twice with AOM to induce colorectal tumours, and fed diets containing either a low [5% (w/w); LGOS] or a high [20% (w/w); HGOS] concentration of GOS. Four weeks after the last AOM injection, 18 animals from each group were killed and their colon was removed for scoring ACF. Half of the animals in the LGOS group were switched to an HGOS diet (L/HGOS) and half of those in the HGOS group to an LGOS diet (H/LGOS). Six weeks after the change in diet, nine animals per group were killed for scoring ACF. Ten months after the start of the study the remaining animals were killed for scoring colorectal tumours. The aberrant crypt multiplicity scored after 13 weeks and the colorectal tumour incidence in rats fed an HGOS diet were significantly lower than those in rats fed an LGOS diet. However, the induction of ACF by AOM, the proliferation rate and apoptotic index of the adenomas, and the size and multiplicity of colorectal tumours were not influenced by the amount of GOS in the diet. The aberrant crypt multiplicity, scored after 13 weeks, was predictive for the tumour outcome at the end of the study. It was concluded that an HGOS diet has a protective effect against the development of colorectal tumours in rats and that this protective effect is exerted during the promotion phase rather than the initiation phase of carcinogenesis.     

Promotion of aberrant crypt foci and cancer in rat colon by thermolyzed protein.

BACKGROUND: We have previously shown that thermolyzed protein (casein) cooked with fat in the diet of the rat promotes the growth of aberrant crypt foci (putative precursors of colon cancer) assessed at 100 days. PURPOSE: To determine how thermolysis affects this promotion, we examined thermolysis conditions, quantity of thermolyzed protein in the diet, and duration of thermolysis. To determine whether the previous finding of promotion of aberrant crypt foci corresponds to promotion of cancers assessed much later, we carried out promotion studies until colon cancers appeared. METHODS: F344 rats were given an initiating dose of azoxymethane and were then randomly allocated to groups receiving diets differing in their quantity and quality of casein. The groups were examined for aberrant crypt foci and tumors in the colon. RESULTS: Aberrant crypt foci were promoted by diets containing thermolyzed casein (180 degrees C, 2 hours). Promotion increased with increasing level of thermolyzed casein in the diet (to 20%) and with increasing thermolysis time (to 4 hours). The number of animals with polyps and cancers was higher in the animals receiving thermolyzed protein (2 hours), 16/23 versus 9/26 (P less than .05) and 10/26 versus 3/27 (P less than .05), respectively. The number of aberrant crypts per focus and the number of large aberrant crypt foci were higher in the tumor-bearing animals. CONCLUSIONS: Thermolyzed casein promotes early colonic precursor lesions in a dose-dependent and thermolysis time-dependent manner; thermolyzed casein also promotes colon cancer. IMPLICATIONS: The promoter formed on thermolysis could be involved in colon cancers associated with diets cooked at elevated temperatures, such as can occur with high-fat diets.     

Scanning electron microscopy of aberrant crypt foci in rat colon

The surface of the colon mucosa of 1,2-dimethylhydrazinetreatedF344 rats was examined with the scanning electron microscope.A detailed examination of the mucosal topography revealed fociwith one to several aberrant crypts. These were seen as structureselevated from the background mucosa. The shape of the luminalopenings of the aberrant crypts varied from elongated or tortuousto circular. However, we found no ultrastructural variationsbetween the different aberrant crypt foci (ACF) or between theACF and the background mucosa. There was no direct relationshipbetween the size of ACF and the number of aberrant crypts perfocus, which may be explained by the mechanism of crypt fission;in two aberrant crypts we discovered the formation of a transverseepithelial septum, dividing the large crypt into two smallercrypts. The gross morphology of the ACF observed by scanningelectron microscopy and light microscopy was in principle thesame.     

Chemopreventive effect of trans-resveratrol--a phytoalexin against colonic aberrant crypt foci and cell proliferation in 1,2-dimethylhydrazine induced colon carcinogenesis

Prevention of cancer remains a primary need and new chemopreventive agents must be developed for this purpose. Towards this goal, a chemoprevention study was conducted to evaluate the activity of resveratrol (Res), a phytoalexin, as an inhibitor of colon carcinogenesis. Wistar male rats were divided into six groups, group 1 were control rats, group 2 were control rats that received Res (8 mg/kg body wt p.o. everyday), rats in groups 3-6 were treated weekly with 1,2-dimethylhydrazine (DMH, 20 mg/kg body wt, s.c. x 15 times). In addition, groups 4, 5 and 6 received Res as in group 2. Modifying effects were assessed using aberrant crypt foci (ACF) and the extent of histopathological lesions as end point markers. At the end of 30 weeks, Res markedly reduced tumor incidence, the degree of histological lesions and also the size of tumors significantly (P < 0.05) as compared with the rats treated with unsupplemented DMH. The number of ACF consisting of more than six aberrant crypts per rat was observed in group 6 (6.2 +/- 1.4), group 5 (7.7 +/- 1.0) and group 4 (8.2 +/- 1.4) which were significantly lower than that of group 3 (22.3 +/- 2.4) (P < 0.05). The most pronounced inhibition of ACF development was noted in rats fed Res for the entire period and also during the post-initiation period. Also, Res administration lowered the number of argyrophilic nucleolar organizing region-associated proteins (AgNORs) per nucleus in non-lesional colonic crypts, which reflects the cell proliferation activity. Oxidative imbalance in DMH-treatment was significantly (P < 0.01) modulated on Res supplementation as indicated by optimal concentration of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH). The results of our study suggest Res to be an effective chemopreventive agent, which suppresses DMH-induced colon carcinogenesis at various stages.     

Anti-carcinogenic properties of omeprazole against human colon cancer cells and azoxymethane-induced colonic aberrant crypt foci formation in rats

Omeprazole is a proton pump inhibitor, a widely used drug to treat ulcers and gastroesophageal refluxdisease. We have evaluated colon cancer chemopreventive properties of omeprazole using azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in male F344 rats and analyzed cell growth inhibition and apoptosis induction in human colon cancer cells. Five-week-old male F344 rats were fed a control or experimental diet containing two doses of omeprazole (200 and 400?ppm). After one week, all animals were s.c. injected with AOM (15?mg/kg body weight, once weekly for two weeks). Rats continued on experimental diets for seven more weeks before being sacrificed. Colons were histopathologically evaluated for ACF. Human colon cancer HCT-116 and HCA-7 cells treated with omeprazole were evaluated for different markers associated with proliferation and apoptotic markers using Western blot technique. Rats fed with 200 and 400?ppm of omeprazole significantly suppressed total colonic ACF formation (~30%, P<0.001) and showed significant suppression of multi-crypt foci (~30-50%, P<0.05-0.001). Omeprazole produced significant dose-response effects on inhibition of multi-crypt foci (≥4). Omeprazole treatment in human colon cancer cell lines HCT-116 and HCA-7 cells resulted in induction of p21waf1/cip1 and decreased the expression of anti-apoptotic proteins Bcl-2, Bcl-XL and survivin in a dose-dependent manner. Anticancer properties observed in colon cancer cell lines suggest that omeprazole may induce key signaling molecules of antiproliferation and inhibition of anti-apoptotic proteins.     

Combined effect of dietary calcium and iron on colonic aberrant crypt foci, cell proliferation and apoptosis, and fecal bile acids in 1,2-dimethylhydrazine-treated rats.

To investigate the combined effect of Ca and Fe on colon carcinogenesis, cell proliferation, apoptosis and fecal bile acids, male Wistar rats were fed the diet containing 5 g Ca/kg (normal Ca) or 15 g Ca/kg (excessive Ca) with 45 mg Fe/kg (normal Fe) or 500 mg Fe/kg (excessive Fe) for 32 days, and given an injection of 1,2-dimethylhydrazine on day 4. Supplemental Ca reduced colonic aberrant crypt foci (ACF), especially in excess Fe group. Excessive Fe elevated the ACF, especially in the normal Ca diet. When the Ca intake was high, excessive Fe caused no influence on the ACF. Alteration of colonic ACF was associated with those of liver and serum Fe concentration. Also, colonic cell proliferation and concentration of deoxycholic acid (DCA) in fecal water-soluble fraction were reduced by supplementation of dietary Ca, but unaffected by that of dietary Fe. Supplementation of Ca and/or Fe elevated colonic cell apoptosis. The results suggest that dietary Ca markedly suppresses colon ACF in the Fe-overloaded rats through altering Fe status, and that supplemental Ca lowers colonic cell proliferation and fecal DCA in the water-soluble fraction and elevates colonic cell apoptosis irrespective of Fe status.     

Classification of aberrant crypt foci and microadenomas in human colon.

Aberrant crypt foci (ACF) can be observed and quantified on the mucosal surface of formalin-fixed human colon resections after staining with methylene blue. To determine whether these ACF could be identified in fresh tissue, 10 colon resections were collected after surgery for colorectal cancer. Unfixed and fixed flat normal colonic mucosa from each colon were scored for ACF under a dissecting microscope after methylene blue staining. The number of ACF per cm2 and the average number of crypts per foci correlated highly in unfixed and fixed mucosa (r = 0.93 and 0.78, respectively). A significantly higher frequency of lesions was found in left-sided compared to right-sided colon resections. To determine whether the topographic features of the ACF gave an indication of the histological appearance, 68 specimens containing ACF or normal mucosa were examined histologically. The presence of slit-like lumen in the crypts of ACF on the mucosal surface correlated with the presence of dysplasia at histology, thus identifying microadenomas. These two observations suggest that the topographic classification of ACF in vivo could be used to distinguish microadenomas, a putative precursor lesion of colon cancer.     

Distribution of lymphoid nodules, aberrant crypt foci and tumours in the colon of carcinogen-treated rats.

Sprague-Dawley rats were given eight weekly subcutaneous injections of 1,2-dimethylhydrazine (DMH) or of vehicle then were sacrificed at 1, 5 or 24 weeks after the last injection of DMH. The locations of pre-existing aggregates of lymphoid nodules (ALNs), the location and multiplicity (size) of aberrant crypt foci (ACF), and the locations of tumours in the colon were determined. A trimodal distribution of pre-existing ALNs along the length of the colon was significantly correlated with the timodal distribution of DMH-induced adenocarcinomas (ACs). A unimodal peak in ACF of all sizes occurred between the sites of two distal ALNs. Thus, the distribution of ACF at 1 or 5 weeks did not correlate with distribution of AC found at 24 weeks. Of the 2640 ACF observed at 1 or at 5 weeks, none were found in the proximal 25% of the colon where ACs eventually occurred. It was concluded that: (1) ALNs play a promotional role in AC formation; (2) the ACs which form in the proximal quarter of the colon seldom if ever form via an ACF precursor; and (3) the location, the number and the size of ACF observed early after DMH exposure did not correlate with the location or predict the incidence of ACs which eventually formed in the colon.     

K-ras mutations in aberrant crypt foci, adenomas and adenocarcinomas during azoxymethane-induced colon carcinogenesis

Ras mutations are an important early event in a number of carcinogen-inducedrodent tumors. Colon carcinogenesis induced in rats by azoxymethaneis a useful model as it mimics the adenoma-carcinoma sequenceobserved in humans. In addition, aberrant crypt foci developin the rat and these lesions appear to be potentially importantprecursors to adenomas in colorectal cancer. Recent studieshave shown that specific K-ras codon 12 and 13 mutations arepresent in up to 66% of carcinogen-induced rat colon adenocarcinomas.We studied the frequency of these mutations during the aberrantcrypt focus-adenoma-carcinoma sequence in azoxymethane-inducedFisher F344 rats. K-ras codon 12 GAT and codon 13 GAC mutationswere detected with a sensitive assay based on the amplificationof DNA using the polymerase chain reaction. No mutations werepresent in normal mucosa. Of 27 aberrant crypt foci, K-ras mutationswere identified in 2 lesions containing 5 and 10 aberrant crypts,respectively. Mutations were present in 1 of 23 and 10 of 27adenomas and adenocarcinomas, respectively. These data suggestthat K-ras mutations play a role during the stages of carcinogenesisin azoxymethane-induced rat colon cancer. The demonstrationof a genetic mutation in aberrant crypt foci provides furtherevidence for the significance of these lesions as precursormarkers of maligant potential during colorectal tumorigenesis.     

Constipation, anthranoid laxatives, melanosis coli, and colon cancer: a risk assessment using aberrant crypt foci.

The associations between colorectal cancer (CRC) and constipation, anthranoid laxative use, and melanosis coli are controversial. Aberrant crypt foci (ACF) are microscopic lesions of the colonic mucosa suspected of being preneoplastic, and their investigation has been advocated to evaluate the cause-effect relationship between putative risk factors and CRC. To this aim, we investigated the relationship between sigmoid cancer (SC) and constipation, anthranoid laxative use, and melanosis coli using ACF analysis as an additional tool of investigation. Fifty-five surgical patients with SC, 41 surgical patients with diverticular disease (DD), and 96 age- and sex-matched subjects without intestinal disease (controls) were interviewed on their history of constipation and anthranoid laxative use. Melanosis coli and ACF characteristics were investigated on sigmoid mucosa in patients with SC or DD. Constipation and anthranoid laxative use were similar between patients with SC (30.9% and 32.7%, respectively) and those with DD (39% and 26.8%) but higher than among controls (18.8% and 8.3%). Melanosis coli was found in 38.2% of patients with SC and in 39% of those with DD. Mean ACF frequency was higher in patients with SC (0.24/cm(2)) than in those with DD (0.10/cm(2); P < 0.0001), and it did not vary according to constipation, laxative use, or melanosis coli in either group. This study confirms the association of ACF frequency with colon cancer and does not support the hypothesis of a cause-effect relationship of CRC with constipation, anthranoid laxative, use or melanosis coli.     

Spontaneous development of aberrant crypt foci in F344 rats

Aberrant crypt foci (ACF) have been proposed as intermediate biomarkers for colon carcinogenesis on the basis of many rodent studies. Although molecular analyses have indicated that these lesions in experimental animals are related to early events in colon carcinogenesis, their preneoplastic nature has yet to be fully elucidated. In the present study, one hundred and thirty 19-week-old male Fischer 344 rats were examined. The biological characteristics of spontaneous ACF were analyzed histopathologically, immunohistochemically and with molecular biological techniques, and compared with colon tumors found in control groups used for carcinogenicity tests. The incidences of spontaneous ACF consisting of 1, 2, 3 and 4 or more crypts were respectively 27.7%, 32.5%, 16.8% and 22.8%. Most ACF were distributed in the lower middle and upper distal colon, and proximal colon ACF was rare. Likewise, ACF frequently (42.5%) developed in untreated animals, whereas the incidence of spontaneous colorectal tumors was extremely low (0.68%) in control male rats. In addition, spontaneous ACF did not show apparent proliferative activity or c-K-ras point mutations. Our results thus suggest that spontaneous ACF rarely progress to colon tumors although long-term sequential observation might be necessary to conclude the significance 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.