Vanadium inhibits DNA-protein cross-links and ameliorates surface level changes of aberrant crypt foci during 1,2-dimethylhydrazine induced rat colon carcinogenesis

The trace mineral vanadium inhibits cancer development in a variety of experimental animal models. The present study was to gain insight into a putative anticancer effect of vanadium in a rat model of colon carcinogenesis. The in vivo study was intended to clarify the effect of vanadium on DNA-protein cross-links (DPC), surface level changes of aberrant crypt foci (ACF) and biotransformation status during 1,2-dimethylhydrazine (1,2-DMH) induced preneoplastic rat colon carcinogenesis. The comet assay showed statistically higher mean base values of DNA-protein mass (p<0.01) and mean frequencies of tailed cells (p<0.001) in the carcinogen-induced group after treatment with proteinase K. Treatment with vanadium in the form of ammonium monovanadate supplemented ad libitum in drinking water for the entire experimental period caused a significant (p<0.02) reduction (40%) in DNA-protein cross-links in colon cells. Further, the biotransformation status of vanadium was ascertained measuring the drug metabolising enzymes, glutathione S-transferase (GST) and cytochrome P-450 (Cyt P-450). Significantly, there was an increase in glutathione S-transferase and cytochrome P-450 levels (p<0.01 and p<0.02, respectively) in rats supplemented with vanadium as compared to their carcinogen controls. As an endpoint marker, we also evaluated the effect of vanadium on surface level changes of aberrant crypt foci induced by 1,2-DMH by scanning electron microscopy. Animals induced with 1,2-DMH and supplemented with vanadium showed a marked improvement in colonic architecture with less number of aberrant crypt foci in contrast to the animals induced with 1,2-DMH alone, thereby exhibiting its anticarcinogenicity by modulating the markers studied herein.     

Modulatory influence of dietary resveratrol during different phases of 1,2-dimethylhydrazine induced mucosal lipid-peroxidation, antioxidant status and aberrant crypt foci development in rat colon carcinogenesis

To shed light on the association of lipid peroxidation and antioxidant status with the development of aberrant crypt foci (ACF), we studied the modulatory influence of resveratrol, supplemented in three dietary regimens (initiation, post-initiation and entire period) on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis. Rats were administered DMH (20 mg/kg body weight, s.c.) for 15 weeks and were supplemented with resveratrol (8 mg/kg body weight, p.o. everyday) in three dietary regimens. Intestines and colons were analyzed for the levels of diene conjugates (DC), lipid hydroperoxides (LOOHs) and thiobarbituric acid reactive substances (TBARS). Enzymic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX; glutathione S-transferase, GST; and glutathione reductase, GR) and non-enzymic reserve (reduced glutathione, GSH; ascorbate; and alpha-tocopherol) were also assessed in the intestine and colon. Unsupplemented DMH exposed rats showed significantly decreased levels/activities of tissue DC, LOOHs, TBARS, SOD, CAT, GSH, GR and significantly elevated (P<0.05) GPX, GST, alpha-tocopherol and ascorbate as compared to control rats. Resveratrol supplementation during the entire period of the study resulted in significant (P<0.01) modulation of lipid peroxidation markers and antioxidants status, which were paralleled with ACF suppression, as compared to DMH-alone treated rats. These results indicate that resveratrol effectively inhibits DMH-induced ACF and colonic tumor development.     

Vanadium inhibits placental glutathione S-transferase (GST-P) positive foci in 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Vanadium (V) has recently been found to possess potent anti-neoplastic activity in rat colon carcinogenesis. In the present study attempts have been made to investigate the expression of the number and area of aberrant crypt foci positive for placental glutathione S-transferase (GST-P) during 1,2-dimethyl hydrazine (DMH)-induced rat colon carcinogenesis. Male Sprague Dawley rats were randomly divided into four groups. Rats in group A were designed as normal controls. Group B animals received DMH once a week (20 mg/kg body wt.) intraperitoneally for 16 weeks. Group C rats received the same treatment of DMH as in group B, along with 0.5-ppm vanadium as ammonium monovanadate ad libitum in drinking water throughout the experiment. Vanadium alone was given to Group D rats without any DMH injection. The expression of the number and the area of aberrant crypt foci (ACF) positive for GST-P was maximum in DMH-treated group. Vanadium-treated rats significantly reduced (P < 0.001) the expression of GST-P positive ACF cells (by 71.13%) for the entire period of the study. Moreover the histopathological examination also showed that vanadium action could minimize the aberrant crypt foci (P < 0.001). Furthermore, vanadium supplementation also elevated SOD activities in both liver and colon (P < 0.01, P < 0.02 and P < 0.01, P < 0.02 respectively) when compared to their carcinogen counterparts. Our results confirm that vanadium is particularly effective in limiting the action of the carcinogen, thereby establishing its anticarcinogenicity in chemically induced rat colon carcinogenesis.     

Knockout of the 15 kDa Selenoprotein Protects against Chemically-Induced Aberrant Crypt Formation in Mice

Evidence suggests that selenium has cancer preventive properties that are largely mediated through selenoproteins. Our previous observations demonstrated that targeted down-regulation of the 15 kDa selenoprotein (Sep15) in murine colon cancer cells resulted in the reversal of the cancer phenotype. The present study investigated the effect of Sep15 knockout in mice using a chemically-induced colon cancer model. Homozygous Sep15 knockout mice, and wild type littermate controls were given four weekly subcutaneous injections of azoxymethane (10 mg/kg). Sep15 knockout mice developed significantly (p<0.001) fewer aberrant crypt foci than controls demonstrating that loss of Sep15 protects against aberrant crypt foci formation. Dietary selenium above adequate levels did not significantly affect aberrant crypt foci formation in Sep15 knockout mice. To investigate molecular targets affected by loss of Sep15, gene expression patterns in colonic mucosal cells of knockout and wild type mice were examined using microarray analysis. Subsequent analyses verified that guanylate binding protein-1 (GBP-1) mRNA and protein expression were strongly upregulated in Sep15 knockout mice. GBP-1, which is expressed in response to interferon-γ, is considered to be an activation marker during inflammatory diseases, and up-regulation of GBP-1 in humans has been associated with a highly significant, increased five-year survival rate in colorectal cancer patients. In agreement with these studies, we observed a higher level of interferon-γ in plasma of Sep15 knockout mice. Overall, our results demonstrate for the first time, that Sep15 knockout mice are protected against chemically-induced aberrant crypt foci formation and that Sep15 appears to have oncogenic properties in colon carcinogenesis in vivo.     

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.     

The modulatory influence of p-methoxycinnamic acid, an active rice bran phenolic acid, against 1,2-dimethylhydrazine-induced lipid peroxidation, antioxidant status and aberrant crypt foci in rat colon carcinogenesis

We investigated the chemopreventive effect of p-methoxycinnamic acid (p-MCA), an active phenolic acid of rice bran, turmeric, and Kaemperfia galanga against 1,2-dimethylhydrazine-induced rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 consisted of control rats that received a modified pellet diet and 0.1% carboxymethyl cellulose. The rats in Group 2 received a modified pellet diet supplemented with p-MCA [80 mg/kg body weight (b.wt.) post-orally (p.o.)] everyday. The rats in Groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) via subcutaneous injections once a week for the first 4 weeks; additionally, the rats in Groups 4, 5 and 6 received p-MCA at doses of 20, 40 and 80 mg/kg b.wt./day p.o., respectively, everyday for 16 weeks. The rats were sacrificed at the end of the experimental period of 16 weeks. The DMH-treated rats exhibited an increased incidence of aberrant crypt foci (ACF) development; an increased crypt multiplicity; decreased concentrations of tissue lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and lipid hydroperoxides (LOOH); decreased levels of tissue enzymic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR); and decreased levels of non-enzymic antioxidants such as reduced glutathione (GSH) and vitamins C, E and A in the colon. Supplementation with p-MCA significantly reversed these changes and significantly inhibited the formation of ACF and its multiplicity. Thus, our findings demonstrate that p-MCA exerts a strong chemopreventive activity against 1,2-dimethylhydrazine-induced colon carcinogenesis by virtue of its ability to prevent the alterations in DMH-induced circulatory and tissue oxidative stress and preneoplastic changes. p-MCA was more effective when administered at a dose of 40 mg/kg b.wt. than at the other two doses tested.     

Regular exercise reduces colon tumorigenesis associated with suppression of iNOS

Several epidemiological studies have shown that regular exercise can prevent the onset of colon cancer, although the mechanism involved is unclear. Expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) is often elevated in an initial step of tumorigenesis and promotes colorectal cancer. We investigated the effect of exercise on colon tumorigenesis associated with iNOS and COX-2 in azoxymethan (AOM)-injected mice. Balb/c mice (8 weeks old) were divided into three groups of 20 animals each, consisting of a sedentary control group, an AOM group, and an exercise plus AOM group. Mice in the groups receiving AOM were injected intraperitoneally with AOM weekly for 2 weeks. Six weeks of regular exercise suppressed the generation of aberrant crypt foci (ACF) in the colon by AOM. Expression of iNOS was decreased by exercise compared with that in sedentary mice along with lower nitrotyrosine level while COX-2 was not changed by either AOM or exercise. Additionally, tumor necrosis factor α (TNFα) was decreased by exercise in the colon and plasma. There was no effect of exercise on the expression of antioxidant enzymes and chaperon protein in the colon. Our results suggest that regular exercise prevents colon tumorigenesis, at least partly via the suppression of iNOS expression associated with anti-inflammation.     

Dietary arsenic affects dimethylhydrazine-induced aberrant crypt formation and hepatic global DNA methylation and DNA methyltransferase activity in rats

Cell culture studies have suggested that arsenic exposure results in decreased S-adenosylmethionine (SAM), causing DNA hypomethylation. Previously, we have shown that hepatic SAM is decreased and/or S-adenosylhomocysteine increased in arsenic-deprived rats; these rats tended to have hypomethylated DNA. To determine, the effect of dietary arsenic on dimethylhydrazine (DMH)-induced aberrant crypt formation in the colon, Fisher 344 weanling male rats were fed diets containing 0,05, or 50 μg As (as NaAsO₂)/g. After 12 wk, dietary arsenic affected the number of aberrant crypts (p<0.02) and aberrant crypt foci (p<0.007) in the colon and the amount of global DNA methylation (p<0.04) and activity of DNA methyltransferase (DNMT) (p<0.003) in the liver. In each case, there were more aberrant crypts and aberrant crypt foci, a relative DNA hypomethylation, and increased activity of DNMT in the rats fed 50 μg As/g compared to those fed 0.5 μg As/g. The same phenomenon, an increased number of aberrant crypts and aberrant crypt foci, DNA hypomethylation, and increased DNMT tended to hold when comparing rats fed the diet containing no supplemental arsenic compared to rats fed 0.5 μg As/g. The data suggest that there is a threshold for As toxicity and that possibly too little dietary As could also be detrimental. The U.S. Department of Agriculture, Agricultural Research Service. Northern Plains Area is an equal opportunity/affirmative action employer and all agency services are available without discrimination.     

DNA damage and aberrant crypt foci as putative biomarkers to evaluate the chemopreventive effect of annatto (Bixa orellana L.) in rat colon carcinogenesis

Chemoprevention opens new perspectives in the prevention of cancer and other degenerative diseases. Use of target-organ biological models at the histological and genetic levels can markedly facilitate the identification of such potential chemopreventive agents. Colon cancer is one of the highest incidence rates throughout the world and some evidences have indicated carotenoids as possible agents that decrease the risk of colorectal cancer. In the present study, we evaluate the activity of annatto (Bixa orellana L.), a natural food colorant rich in carotenoid, on the formation of aberrant crypt foci (ACF) induced by dimethylhydrazine (DMH) in rat colon. Further, we investigate, the effect of annatto on DMH-induced DNA damage, by the comet assay. Male Wistar rats were given s.c. injections of DMH (40 mg/kg body wt.) twice a week for 2 weeks to induce ACF. They also received experimental diets containing annatto at 20, 200 or 1000 ppm for five 5 weeks before (pre-treatment), or 10 weeks after (post-treatment) DMH treatment. In both protocols the rats were sacrificed on week 15th. For the comet assay, the animals were fed with the same experimental diets for 2 weeks. Four hours before the sacrifice, the animals received an s.c. injection of DMH (40 mg/kg body wt.). Under such conditions, dietary administration of 1000 ppm annatto neither induce DNA damage in blood and colon cells nor aberrant crypt foci in rat distal colon. Conversely, annatto was successful in inhibiting the number of crypts/colon (animal), but not in the incidence of DMH-induced ACF, mainly when administered after DMH. However, no antigenotoxic effect was observed in colon cells. These findings suggest possible chemopreventive effects of annatto through their modulation of the cryptal cell proliferation but not at the initiation stage of colon carcinogenesis.     

Effects of quercetin and beta-carotene supplementation on azoxymethane-induced colon carcinogenesis and inflammatory responses in rats fed with high-fat diet rich in omega-6 fatty acids

Chronic inflammation in gastrointestinal tract has been suggested as a risk factor for tumor formation. The effect of dietary supplementation of quercetin or beta-carotene on colon carcinogenesis and inflammatory response in rats fed with high-fat diet rich in omega-6 fatty acids was assessed. Animals were exposed to two weekly subcutaneous injections of AOM (azoxymethane) at a single dose of 15 mg/kg body weight. A portion of rats from each group was sacrificed at 8 weeks after the last AOM treatment to determine ACF (aberrant crypt foci) formation. Colonic mucosa expression of iNOS (inducible nitric oxide) and COX-2 (cyclooxygenase-2) protein, and blood PGE2 (prostaglandin E2) level were measured. The remaining groups of animals were sacrificed at 33 weeks after the last AOM treatment to examine colon tumor formation. Rats on high-fat diet developed more aberrant crypt foci (P<0.05) compared with those of rats on regular diet. In the same vein, but in contrast to the effect seen with regular diet, the high-fat diet induced a significant up-regulation of iNOS expression. There was no significant change in the extent of COX-2 expression or in the PGE2 levels. Quercetin or beta-carotene supplementation reduced the number of ACF only in animals fed high-fat diet (p<0.05), however, no significant difference in tumor incidence was found. At week 33, the expression of iNOS was reduced by quercetin without a statistical significance, and COX-2 expression was slightly reduced in rats on beta-carotene supplementation. No change in PGE2 levels was observed. Whilst dietary antioxidants are considered as effective suppressors for precancerous lesion formation in colons exposed to high-risk diet, it is clear that elucidating the role of individual antioxidants in colon tumor formation coupled with an understanding of the molecular mechanisms involved would benefit colon cancer prevention strategies.     

Protective Effect of <Emphasis Type="Italic">Lactobacillus casei</Emphasis> on DMH-Induced Colon Carcinogenesis in Mice

The administration of probiotics is a promising approach to reduce the prevalence of colon cancer, a multifactorial disease, with hereditary factors, as well as environmental lifestyle-related risk factors. Biogenic polyamines, putrescine, spermidine, and spermine are small cationic molecules with great roles in cell proliferation and differentiation as well as regulation of gene expression. Ornithine decarboxylase is the first rate-limiting enzyme for polyamine synthesis, and upregulation of ornithine decarboxylase activity and polyamine metabolism has been associated with abnormal cell proliferation. This paper is focused on studying the protective role of Lactobacillus casei ATCC 393 in a chemically induced mouse model of colon carcinogenesis, directing our attention on aberrant crypt foci as preneoplastic markers, and on polyamine metabolism as a possible key player in carcinogenesis. BALB/c mice were administered 1,2-dimethylhydrazine dihydrochloride (DMH) to induce colon cancer (20 mg/kg body weight, subcutaneous, twice a week for 24 weeks). L. casei ATCC 393 was given orally (10⁶ CFU, twice a week), 2 weeks before DMH administration. Hematoxylin and eosin staining, high-performance liquid chromatography, and Western blotting were used to evaluate aberrant crypt foci, urinary polyamines, and ornithine decarboxylase expression in the colon. The experimental data showed that the preventive administration of L. casei ATCC 393 may delay the onset of cancer as it significantly reduced the number of DMH-induced aberrant crypt foci, the levels of putrescine, and the expression of ornithine decarboxylase. Hence, this probiotic strain has a prospective role in protection against colon carcinogenesis, and its antimutagenic activity may be associated with the maintenance of polyamine metabolism.     

Multivitamin and mineral supplementation in 1,2-dimethylhydrazine induced experimental colon carcinogenesis and evaluation of free radical status, antioxidant potential, and incidence of ACF

This study was performed to determine the chemopreventive and antioxidant status of multivitamin and mineral (0.01% in drinking water, ad libitum) supplements in 1,2-dimethylhydrazine (DMH)-induced experimental colon carcinogenesis. Experimental colon carcinogenesis was induced in male albino Wistar rats by injecting DMH (20 mg·(kg body mass)(-1)) once weekly for 15 consecutive weeks, and administering a multivitamin supplement in 3 regimes (initiation, post-initiation, and entire experimental period) for 32 weeks. We studied lipid peroxidation products (thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes) in the circulation and in the tissues, antioxidant status (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and non-enzymatic antioxidant-reduced glutathione) of the tissues, aberrant crypt foci (ACF), and histopathological alterations. DMH-induced rats had an increase in lipid peroxidation products and a lower antioxidant status compared with control animals. Multivitamin and mineral supplementation during the initiation, post-initiation, and the entire study period significantly decreased the levels of lipid peroxidation products in circulation and colonic tissues, significantly elevated the activities of the antioxidant enzymes and reduced glutathione to near normalcy in DMH-induced rats. The incidence of ACF was reduced by [corrected] 84.1% in rats supplemented with multivitamin and minerals for the entire study and prevented the colonic tissue from histopathological alterations induced by DMH.     

Chemopreventive effects of coffee bean and rice constituents on colorectal carcinogenesis

Polyphenolic compound chlorogenic acid (CGA) known to be much contained in coffee beans was found to have a regressive effect on induced aberrant crypt foci (ACF) as well as on development of ACF in azoxymethane (AOM)-induced colorectal carcinogenesis in rats. Rice germ and gamma-aminobutyric acid-enriched defatted rice germ inhibited AOM-induced ACF formation and colorectal carcinogenesis in rats. Ferulic acid (FA) also known to be contained in coffee beans and rice prevented AOM-induced ACF formation and intestinal carcinogenesis in rats. Both of food factors, coffee and rice may be of benefit to prevention of human colorectal cancers.     

Antiserum detection of reactive carbonyl species-modified DNA in human colonocytes

Polyunsaturated fats have been linked to occurrences of sporadic colon cancer. One possible cause may be degradation of polyunsaturated fats during cooking, resulting in multiple reactive carbonyl species (RCS) that can damage nuclear DNA and proteins, particularly in rapidly dividing colon crypt cells. This study describes a novel antiserum against RCS-modified DNA, with apparent order of reactivity to DNA modified with 4-hydroxy-trans-2-nonenal > glyoxal > acrolein > crotonaldehyde > malondialdehyde; some reactivity was also observed against conjugated Schiff base-type structures. Anti-(RCS-DNA) antiserum was successfully utilised to demonstrate formation of RCS-DNA in a human colon cell model, exposed to RCS insult derived from endogenous and exogenous lipid peroxidation sources. Further utilisation of the antiserum for immunohistochemical analysis confirmed RCS-modified DNA in crypt areas of ‘normal’ colon tissue. These results fully support a potential role for dietary lipid peroxidation products in the development of sporadic colon cancer.     

Novel mucilage fraction of Sinapis alba L. (mustard) reduces azoxymethane-induced colonic aberrant crypt foci formation in F344 and Zucker obese rats

Seeds of Sinapis alba Linn. (commonly called yellow or white mustard) and their components have been reported to possess anticancer properties. In this study, we evaluated the efficacy of a novel mucilaginous fraction of mustard seeds in inhibiting colonic preneoplastic changes in animal models of sporadic and obesity-associated colon cancer. In two separate studies, male Sprague-Dawley or female Zucker obese rats, injected with azoxymethane (15 or 10 mg/kg body wt. once a week for 2 weeks, respectively), were fed AIN-93G diets with or without 5% mustard mucilage (MM) (w/w) for 8 weeks. Our aim was to measure the ability to modulate the number of aberrant crypt foci (ACF), putative preneoplastic lesions of the colon. The data were classified into total numbers of ACF and large ACF (crypt multiplicity of 4 or more). We report here that 5% MM significantly (p<0.05) decreased the number of total (approximately 21% inhibition) and large (approximately 50% inhibition) ACF in the colons of Sprague-Dawley rats compared to that in untreated controls. In addition, 5% MM supplemented diet significantly lowered (p<0.05) the number of total (approximately 63% inhibition) and large (approximately 60% inhibition) colonic ACF in Zucker obese rats compared to untreated obese rats, and had no effect on fasting plasma cholesterol or triglyceride levels. These results demonstrate the possible role of MM as a functional food against sporadic and obesity-associated colon cancer, and provide impetus to conduct research to understand the underlying mechanism(s) of action.     

Biphasic response of checkpoint control proteins in hyperoxia: exposure to lower levels of oxygen induces genome maintenance genes in experimental baboon BPD

Objective of the study is to evaluate the modifying potential of p-methoxycinnamic acid (p-MCA), an active rice bran phenolic acid on biotransforming bacterial enzymes and xenobiotic metabolizing enzymes in 1,2-dimethylhydrazine-induced rat colon carcinogenesis. 48 male albino wistar rats were divided into six groups. Group1 (control) received modified pellet diet and 0.1 % carboxymethylcellulose; group2 received modified pellet diet along with p-MCA (80 mg/kg b.wt. p.o.) everyday for 16 weeks; groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) subcutaneous injection once a week for the first 4 weeks, while groups 4–6 received p-MCA at three different doses of 20, 40 and 80 mg/kg b.wt. p.o. everyday for 16 weeks. A significant increase in carcinogen-activating enzymes (cytochrome P450, cytochrome b5, cytochrome P4502E1, NADH-cytochrome-b5-reductase and NADPH-cytochrome-P450 reductase) with concomitant decrease in phaseII enzymes, DT-Diaphorase, glutathione S-transferase, UDP-glucuronyl-transferase and gamma glutamyltransferase were observed in group3 compared to control. DMH treatment significantly increased the activities of feacal and colonic bacterial enzymes (β-glucosidase, β-galactosidase, β-glucuronidase, nitroreductase, sulphatase and mucinase). p-MCA supplementation (40 mg/kg b.wt) to carcinogen exposed rats inhibited these enzymes, which were near those of control rats. The formation of dysplastic aberrant crypt foci in the colon and the histopathological observations of the liver also supports our biochemical findings. p-MCA (40 mg/kg b.wt.) offers remarkable modulating efficacy of biotransforming bacterial and xenobiotic metabolizing enzymes in colon carcinogenesis.     

The Chemopotential Effect of Annona muricata Leaves against Azoxymethane-Induced Colonic Aberrant Crypt Foci in Rats and the Apoptotic Effect of Acetogenin Annomuricin E in HT-29 Cells: A Bioassay-Guided Approach

Annona muricata has been used in folk medicine for the treatment of cancer and tumors. This study evaluated the chemopreventive properties of an ethyl acetate extract of A. muricata leaves (EEAML) on azoxymethane-induced colonic aberrant crypt foci (ACF) in rats. Moreover, the cytotoxic compound of EEAML (Annomuricin E) was isolated, and its apoptosis-inducing effect was investigated against HT-29 colon cancer cell line using a bioassay-guided approach. This experiment was performed on five groups of rats: negative control, cancer control, EEAML (250 mg/kg), EEAML (500 mg/kg) and positive control (5-fluorouracil). Methylene blue staining of colorectal specimens showed that application of EEAML at both doses significantly reduced the colonic ACF formation compared with the cancer control group. Immunohistochemistry analysis showed the down-regulation of PCNA and Bcl-2 proteins and the up-regulation of Bax protein after administration of EEAML compared with the cancer control group. In addition, an increase in the levels of enzymatic antioxidants and a decrease in the malondialdehyde level of the colon tissue homogenates were observed, suggesting the suppression of lipid peroxidation. Annomuricin E inhibited the growth of HT-29 cells with an IC50 value of 1.62 ± 0.24 μg/ml after 48 h. The cytotoxic effect of annomuricin E was further substantiated by G1 cell cycle arrest and early apoptosis induction in HT-29 cells. Annomuricin E triggered mitochondria-initiated events, including the dissipation of the mitochondrial membrane potential and the leakage of cytochrome c from the mitochondria. Prior to these events, annomuricin E activated caspase 3/7 and caspase 9. Upstream, annomuricin E induced a time-dependent upregulation of Bax and downregulation of Bcl-2 at the mRNA and protein levels. In conclusion, these findings substantiate the usage of A. muricata leaves in ethnomedicine against cancer and highlight annomuricin E as one of the contributing compounds in the anticancer activity of A. muricata leaves.     

Haploinsufficiency of SGO1 results in deregulated centrosome dynamics,enhanced chromosomal instability and colon tumorigenesis

Chromosome instability (CIN) is found in 85% of colorectal cancers. Defects in mitotic processes are implicated in high CIN and may be critical events in colorectal tumorigenesis. Shugoshin-1 (SGO1) aids in the maintenance of chromosome cohesion and prevents premature chromosome separation and CIN. In addition, integrity of the centrosome may be compromised due to the deficiency of Cohesin and Sgo1 through the disengagement of centrioles. We report here the generation and characterization of SGO1-mutant mice and show that haploinsufficiency of SGO1 leads to enhanced colonic tumorigenesis. Complete disruption of SGO1 results in embryonic lethality, whereas SGO1^+/- mice are viable and fertile. Haploinsufficiency of SGO1 results in genomic instability manifested as missegregation of chromosomes and formation of extra centrosomal foci in both murine embryonic fibroblasts and adult bone marrow cells. Enhanced CIN observed in SGO1-deficient mice resulted in an increase in formation of aberrant crypt foci (ACF) and accelerated development of tumors after exposure to azoxymethane (AOM), a colon carcinogen. Together, these results suggest that haploinsufficiency of SGO1 causes enhanced CIN, colonic preneoplastic lesions and tumorigenesis in mice. SGO1 is essential for the suppression of CIN and tumor formation.     

Tomato powder impedes the development of azoxymethane-induced colorectal cancer in rats through suppression of COX-2 expression via NF-κB and regulating Nrf2/HO-1 pathway

Cancer is one of the leading causes of death worldwide. Since dietary factors have been connected to a reduced risk of a diversity of human cancers, in this study we investigated the effects of tomato powder (TP) on the development of azoxymethane (AOM)-induced colorectal cancer in Wistar rats, and possible mechanism(s) by which TP shows its chemopreventive activity. Here we show that TP added to feed at 5% rate decreases the rate of aberrant crypt foci (ACF) and reduces the development of adenocarcinoma and growth of AOM-induced colorectal cancer in rats. In addition, we demonstrate that TP supplementation shows its chemopreventive activities through inhibition of cyclooxygenase-2 (COX-2) expression via NF-κB pathway and promotion of apoptosis, as well as regulating Nrf2/HO-1 signaling pathway in colorectal tissue of AOM-treated rats. Our findings identify an intimate connection between dietary supplementation of TP and the decreased risk of colorectal cancer in rats, and suggest that consumption of TP would be a natural candidate for the prevention of colorectal cancer in men.