Injections Of DMH Research Articles

Aged Garlic Extract Has Chemopreventative Effects On 1,2-Dimethylhydrazine-Induced Colon Tumors in Rats

Garlic has been reported to have chemopreventive effects against a variety of cancers. However, different garlic preparations contain different constituents. We investigated the chemopreventive effect of aged garlic extract (AGE), an odorless product from prolonged extraction of fresh garlic, on colon carcinogenesis and cell proliferation in 1,2-dimethylhydrazine (DMH)-induced colon neoplastic rats. Rats were given weekly subcutaneous injections of DMH (20 mg/kg) for 20 wk, and fed either a basal diet or one containing 4% AGE. Serum from AGE-treated rats contained detectable S-allylcysteine. The AGE diet significantly reduced the number of colon tumors and aberrant crypt foci compared to the basal diet. Cell proliferation of normal-appearing colonic mucosa was assessed by MIB-5 immunohistochemistry. AGE treatment significantly decreased the mean MIB-5-labeling index. These findings suggest AGE has a chemopreventive effect on colon carcinogenesis through suppression of cell proliferation.

Effect of dietary caraway (Carum carvi L.) on aberrant crypt foci development, fecal steroids, and intestinal alkaline phosphatase activities in 1,2-dimethylhydrazine-induced colon carcinogenesis

Colon cancer is one of the most common malignancies in many regions of the world and is thought to arise from the accumulation of mutations in a single epithelial cell of the colon and rectum. Caraway (Carum carvi L. Umbelliferae) is a shrub with a long history as a medicinal plant since ancient times. The effect of different doses of caraway (CC) on the formation of aberrant crypt foci (ACF) and the levels of fecal bile acids, neutral sterols, and alkaline phosphatase (ALP) activities were studied in 1,2-dimethylhydrazine (DMH)-induced colon cancer in rats. Animals were randomized into 6 groups. Group 1 served as control, and group 2 received 90 mg/kg body weight caraway orally everyday. Groups 3-6 rats were given subcutaneous injections of DMH (20 mg/kg body weight) once a week for the first 4 weeks to induce ACF. Rats in groups 4-6, in addition to DMH injections, received caraway at 30, 60, and 90 mg/kg body weight respectively p.o. everyday until the end of whole experimental period of 15 weeks. Caraway supplementation significantly reduced ACF development and also decreased the levels of fecal bile acids, neutral sterols, and tissue ALP activities. The histological alterations induced by DMH were also significantly improved. Overall, our results showed that all 3 doses of caraway inhibited tumorigenesis though the effect of the intermediary dose of 60 mg/kg body weight was more pronounced.

Lack of chemopreventive effects of ginger on colon carcinogenesis induced by 1,2-dimethylhydrazine in rats

Ginger ( Zingiber officinale Roscoe) has been proposed as a promising candidate for cancer prevention. Its modifying potential on the process of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) was investigated in male Wistar rats using the aberrant crypt foci (ACF) assay. Five groups were studied: Groups 1–3 were given four s.c. injections of DMH (40 mg/kg b.w.) twice a week, during two weeks, whereas Groups 4 and 5 received similar injections of EDTA solution (DMH vehicle). After DMH-initiation, the animals were fed a ginger extract mixed in the basal diet at 0.5% (Group 2) and 1.0% (Groups 3 and 4) for 10 weeks. All rats were killed after 12 weeks and the colons were analyzed for ACF formation and crypt multiplicity. The rates of cell proliferation and apoptosis were also evaluated in epithelial colonic crypt cells. Dietary consumption of ginger at both dose levels did not induce any toxicity in the rats, but ginger meal at 1% decreased significantly serum cholesterol levels ( p < 0.038). Treatment with ginger did not suppress ACF formation or the number of crypts per ACF in the DMH-treated group. Dietary ginger did not significantly change the proliferative or apoptosis indexes of the colonic crypt cells induced by DMH. Thus, the present results did not confirm a chemopreventive activity of ginger on colon carcinogenesis as analyzed by the ACF bioassay and by the growth kinetics of the colonic mucosa.

Inhibitory effect of dietary monoglucosylceramide 1‐O‐β‐glucosyl‐N‐2′‐hydroxyarachidoyl‐4,8‐sphingadienine on two different categories of colon preneoplastic lesions induced by 1,2‐dimethylhydrazine in F344 rats

Sphingolipids display a wide spectrum of biological activities, including cell growth, differentiation and apoptosis. However, precise mechanisms by which these compounds exert anticancer or cancer-preventive effects are not known. In the present study, we evaluated the preventive efficacy of enriched dietary monoglucosylceramide 1-O-beta-glucosyl-N-2'-hydroxyarachidoyl-4,8-sphingadienine (G(1)CM) on 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) and beta-catenin-accumulated crypt (BCAC) formation in F344 rats during initiation stage. We also examined whether G(1)CM affects cell proliferation and apoptosis in these lesions. Pure G(1)CM was isolated from rice bran. Forty-two rats were divided randomly into five experimental groups. Rats in groups 1-3 were given subcutaneous injections of DMH (40 mg/kg body weight) once a week for 2 weeks. One week before the first injection of DMH, rats in groups 2 and 3 were fed a diet containing 200 and 1,000 p.p.m. G(1)CM, respectively, for 5 weeks. Rats in group 4 were fed a diet containing 1,000 p.p.m. G(1)CM. Rats in group 5 were given the basal diet alone and served as untreated controls. The experiment was terminated 5 weeks after the start. Dietary G(1)CM at both doses (groups 2 and 3) significantly inhibited the induction of ACF and BCAC (P<0.001) when compared to group 1 treated with DMH alone. In groups 2 and 3, the proliferating cell nuclear antigen labeling indices of epithelial cells in ACF and BCAC were also lower than in group 1 (P<0.0001 for ACF, P<0.05 for BCAC). These results, that dietary G(1)CM has possible chemopreventive effects in the present short-term colon carcinogenesis bioassays, suggest that longer exposure may cause suppression of tumor development.

The cables gene on chromosome 18Q regulates colon cancer progression in vivo

Early events involved in the pathogenesis of colorectal cancer include mutations in the Adenomatous Polyposis Coli tumor-suppressor gene and oncogenic KRAS mutations. Later events include deletions on chromosome 18q, which are observed in a high proportion of colorectal cancers. However, the important tumor suppressor genes targeted by these deletions have not been fully defined. A previous study found Cables is located on human chromosome 18q11-12. Loss of Cables expression as determined by immunohistochemical staining (IHC) occurred in 60-70% of sporadic colorectal cancers that were usually correlated to loss of heterozygosity at 18q. To determine if Cables is an important target for the chromosome 18q deletions, the susceptibility of Cables-/- mice to develop colon tumors was studied. A well characterized colonic carcinogen, 1,2-dimethylhydrazine (DMH) was used as a tumor initiator. Cables-/- mice (n=25) and the Cables+/+ littermates (n=25) were treated with subcutaneous DMH injections over 20 weeks to initiate tumorigenesis. The median survival after DMH injections was significantly shorter for the Cables-/- mice compared to Cables+/+ littermates. The total number of colorectal tumors that developed in the Cables-/- mice was 46 tumors versus 21 tumors. The increased numbers of colorectal tumors, as well as shorter survival of the Cables-/- mice provides compelling evidence that Cables could play an important role in the pathogenesis and progression of colon cancer in mice. These data coupled with previous observations support the hypothesis that Cables is a relevant target of the chromosome 18q deletions frequently seen in human colorectal cancer.

A new medium-term rat colon bioassay applying neoplastic lesions as endpoints for detection of carcinogenesis modifiers–validation with known modifiers

We have established a medium-term colorectal carcinogenesis rat model initiated with 1,2-dimethylhydrazine (DMH) followed by dextran sodium sulfate (DSS) treatment, featuring induction of neoplastic lesions within 10 weeks. In the present study, we examined its ability to detect modification of colon lesion development with 10- or 20-week experimental periods. F344 male rats were given three subcutaneous injections of DMH (40 mg/kg b.w.) in a week followed by free access to drinking water containing 1% DSS for a week. One week after this regimen, basal diet alone, basal diet containing 0.04% nimesulide or 2% lactoferrin as known inhibitors, 0.3% deoxycholic acid (DCA) as a promoter or 1.5% 1-hydroxyanthraquinone (1-HA) as a carcinogen were supplied. At week 10, the incidence and multiplicity of combined adenomas and adenocarcinomas were significantly ( P<0.05 or 0.01) decreased by nimesulide and lactoferrin, and values for adenomas were significantly ( P<0.01) increased in the 1-HA group. There was no clear change in the DCA group. At week 20, multiplicity and volume of the tumors were significantly ( P<0.01 or 0.05) decreased by nimesulide, but no effect was now evident with lactoferrin. Multiplicity and volume of tumors were significantly ( P<0.01) increased in 1-HA group and a similar tendency was apparent ( P=0.08) with DCA. It is concluded that this system offers a useful tool for detection of colorectal carcinogenesis modifiers within 10–20 weeks, pending further studies for verification employing other model chemicals.

Chemopreventive efficacy of ginger, a naturally occurring anticarcinogen during the initiation, post-initiation stages of 1,2 dimethylhydrazine-induced colon cancer

Background Ginger ( Zingiber officinale Rosc) is a natural dietary component, which has antioxidant and anticarcinogenic properties. We investigated the effect of ginger on the initiation and post-initiation stages of 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in male Wistar rats. Methods Rats were given a weekly subcutaneous injection of DMH (20 mg/kg body weight) in the groin for 15 weeks. Ginger (50 mg/kg body weight/everyday p.o.) was given to the rats at the initiation, post-initiation stages of carcinogenesis. The activity of lipid peroxidation was studied by measuring the formation of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD), and the antioxidant status by measuring superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione- S-transferase (GST), glutathione reductase (GR), reduced glutathione (GSH), vitamins C, E, and A concentrations in the circulation of 1,2-dimethylhydrazine-induced experimental colon cancer. Results In the presence of a known colon carcinogen, DMH, plasma lipid peroxidation (TBARS, lipid hydroperoxides and conjugated dienes) and cancer incidence were significantly increased whereas enzymic (GPx, GST, GR, SOD and CAT) and non-enzymic antioxidant concentrations (GSH, vitamins C, E, and A) were decreased as compared to control rats. The number of tumors as well as the incidence of cancer was significantly decreased on treatment with ginger. In addition, ginger supplementation at the initiation stage and also at the post-initiation stages of carcinogenesis significantly reduced circulating lipid peroxidation and significantly enhanced the enzymic and non-enzymic antioxidants as compared to unsupplemented DMH-treated rats. Conclusions Ginger supplementation suppresses colon carcinogenesis in the presence of the procarcinogen DMH.

Cloudy apple juice decreases DNA damage, hyperproliferation and aberrant crypt foci development in the distal colon of DMH-initiated rats

Clear (CleA) and cloudy (CloA) apple juices containing different amounts of analyzed procyanidins and pectin were investigated for preventive effects of colon cancer and underlying molecular mechanisms in F344 rats given intraperitoneal injections of 1,2-dimethylhydrazine (DMH; 20 mg/kg body wt) once a week for 4 weeks. Rats received either water (Cont), CleA or CloA (ad libitum) for 7 weeks starting 1 week before the first DMH injection. CloA inhibited DMH induced genotoxic damage in mucosa cells of the distal colon compared with Cont as investigated by single-cell microgel electrophoresis assay. The mean tail intensity in mucosa cells of DMH-treated controls (Cont/DMH: 6.1+/-0.9%) was significantly reduced by CloA (2.4+/-0.8%; P<0.01) but not by CleA intervention (4.1+/-1.2%; P>0.05). The crypt cell proliferation index induced by DMH (Cont/NaCl: 10.0+/-0.7%; Cont/DMH: 19.9+/-1.0%; P<0.001) was significantly decreased by CleA (15.7+/-0.7%; P<0.001) and CloA intervention (11.9+/-0.4%; P<0.001). CloA but not CleA significantly reduced the number of large aberrant crypt foci (ACF) consisting of more than four aberrant crypts (AC) (Cont/DMH: 37.4+/-5.4; CleA/DMH: 32.8+/-4.4, P>0.05; CloA/DMH: 18.8+/-2.5 ACF; P<0.05) and the overall mean ACF size in the distal colon (Cont/DMH: 2.31+/-0.09; CleA/DMH: 2.27+/-0.05; CloA/DMH: 2.04+/-0.03 AC/ACF; P<0.05). After treatment with DMH and/or apple juices there were no changes in transcript levels of colonic cyclooxygenase isoforms (COX-1, COX-2) or glutathione-associated enzymes (GST-M2, gamma-GCS, GST-P), the splenocyte natural killer cell activity and plasma antioxidant status. However, CloA but not CleA prevented the DMH-induced reduction of splenocyte CD4/CD8 (T-helper cells to cytotoxic lymphocytes) ratio. Since both formulations contained comparable concentrations and types of monomeric polyphenols, complex polyphenols or non-polyphenolic compounds, such as pectin might be responsible for the stronger cancer-preventive effect by CloA.

Rofecoxib does not inhibit aberrant crypt foci formation but inhibits later steps in the development of experimental colorectal cancer: Rofecoxib in experimental colon cancer

ObjectiveCyclooxygenase-2 (COX-2) has been shown to have an important role in carcinogenesis. Elevated COX-2 expression has been reported in several human tumours, including colorectal cancer (CRC) and appears to correlate with survival inversely. Regular use of non-steroidal anti-inflammatory drugs (NSAIDs) can decrease the incidence of CRC, but prolonged administration may cause side effects. Selective COX-2 inhibitors have comparable effects to NSAIDs with reduced side effects. The aim of the present study was to analyse the potential therapeutic role of rofecoxib, a selective COX-2 inhibitor, in experimentally induced rat colorectal tumours.Material and methodsSixty-three Wistar male rats (33 in the experimental group and 30 in the control group) received subcutaneous injections of 1,2-dimethylhydrazine (DMH). Synchronal with the first injection of DMH in the experimental group, rats were given rofecoxib orally for 6 months, when autopsy was done. Colorectal tumours were evaluated quantitatively and histopathologically for the presence of aberrant crypt foci (ACF), adenomas and adenocarcinomas.ResultsNo statistically significant differences were found in the number of dysplastic ACF between the experimental and control groups (p>0.05). However, a significant lower incidence of adenomas (p<0.05), adenocarcinomas (p<0.05) and decreased volume of macroscopically visible tumours (by 42%) was found in the experimental group. Furthermore, no significant differences were evaluated between the groups according to the degree of dysplasia and Dukes stage. In the experimental group, chronic ulcerations were found in the upper gastrointestinal tract in 9% of the rats.ConclusionOur data suggest that rofecoxib effectively inhibits tumour growth and progression but not tumour initiation.

Chemoprevention of Colon Cancer by a Synthetic Curcumin Analog Involves Amelioration of Oxidative Stress

The modulating effects of a bisdemethoxycurcumin analog (BDMC-A) on 1,2-dimethylhydrazine (DMH)-induced oxidative stress during colon carcinogenesis was investigated in male Wistar rats. The effects were compared with those of curcumin, a known anticarcinogen. All the animals given a weekly subcutaneous injection of DMH (20 mg/kg body wt.) for 15 weeks developed colon tumors. The colon and intestine administered DMH showed a decrease in lipid peroxidation with a concomitant increase in the activities of GSH-dependent enzymes (glutathione peroxidase, glutathione S-transferase) when compared to untreated control rats. In groups of animals given DMH and BDMC-A no tumors were observed, and the lipid peroxidation as well as the GSH-dependent enzymes showed a pattern similar to that of untreated control rats. We speculate that BDMC-A modulates DMH-induced oxidative stress and offers chemoprevention against colon carcinogenesis, and the modulatory effect is comparable with that of curcumin. Thus, lipid peroxidation and antioxidant status together could be used as markers of colon cancer chemoprevention by BDMC-A.

JTE-522, a selective cyclooxygenase-2 inhibitor, inhibits induction but not growth and invasion of 1,2-dimethylhydrazine-induced tubular adenocarcinomas of colon in rats.

We have previously demonstrated that JTE-522, a selective cyclooxygenase-2 (COX-2) inhibitor, inhibited development of aberrant crypt foci (ACF) in rats, a putative preneoplastic lesion in colon, and suggested its inhibitory potential in rat colon carcinogenesis. To evaluate the chemopreventive properties of JTE-522, the present study was design to evaluate the inhibitory effects of JTE-522 on rat colon tumorigenesis induced by 1,2-dimethylhydrazine (DMH). Rats at 6 weeks of age were divided into 4 groups. One week after the start of the experiment, all rats received DMH by s.c. injection at a dose of 40 mg/kg body weight once a week for 4 successive weeks. As the initiation and postinitiation treatment groups, groups 1-3 were fed diets containing 0, 50, or 150 ppm JTE-522, respectively, from the start of the study to the end. As the postinitiation treatment group, group 4 was given 150 ppm JTE-522 from 1 week after the last DMH injection to the end of the study. Forty weeks after the start of the experiment, administration of 150 ppm JTE-522 during both initiation and postinitiation stages significantly inhibited the incidences of tubular adenocarcinomas and total carcinomas, as well as total tumors in the colon. The inhibitory effect of JTE-522 was most prominent for tubular adenocarcinomas, but was not observed in the nontubular carcinomas (signet-ring cell and mucinous carcinomas). Almost equal inhibitory effects on tubular adenocarcinomas were also observed in the rats given 150 ppm JTE-522 during the postinitiation stage, suggesting that its major anticancer action is at the postinitiation phase. However, JTE-522 had no effect on the size or invasive extent of tubular adenocarcinomas. Furthermore, microarray analyses revealed that JTE-522 had no effect on gene expression levels in DMH-induced tubular adenocarcinomas. These findings suggest that JTE-522 possesses chemopreventive activity against induction but not progression of tubular adenocarcinomas in rat colon. In view of the significant inhibitory effects of JTE-522 on ACF, its major anticancer action may occur in the postinitiation stage but before the malignant conversion stage of DMH-induced colon carcinogenesis.

The potent colon carcinogen, 1,2-dimethylhydrazine induces mutations primarily in the colon

1,2-Dimethylhydrazine (DMH) is a potent colon carcinogen that is commonly used as an initiator in studies of the effects of diet on colon cancer. Previous studies have shown that although this compound produces multiple tumors in the colons in most individuals of every species tested, it is, at best, marginally mutagenic in the bone marrow (micronuclei) and small intestine (Dlb-1 mutations). Here we report its mutagenicity in the primary target tissue, the colonic epithelium, by means of the Muta™Mouse cII assay, an assay for intragenic mutations in a lambda shuttle vector that is integrated into the genome of these mice. Animals were treated with 0, 10, 20, or 30 mg/ml of DMH, either as a single injection or as multiple weekly injections, and mutations were measured in both the small intestine and colon. In the small intestine, there was an increase in mutant frequency following a single injection of DMH, but this was significant only at 30 mg/kg [induced mutant frequency (MF) = 18 × 10 −5 mutants/plaque]. In the colon, following a single treatment of DMH, there was a significant increase in mutant frequency at doses of 20 and 30 mg/kg (induced MF = 17 × 10 −5 and 23 × 10 −5 mutants/plaque, respectively). Following ten injections of 20 mg/kg of DMH, there was a greater than ten-fold increase in mutations in the colon (MF = 275 × 10 −5 mutants/plaque) than the small intestine (MF = 25 × 10 −5 mutants/plaque). These results show that DMH, under the conditions typically used for dietary studies, induces large numbers of mutations in the tissue in which it induces most cancers.

Effect of polyphenolic extracts from red wine and 4-OH-coumaric acid on 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

Total polyphenolic extracts from red wine protect against azoxymethane (AOM)-induced colon carcinogenesis in rats. Since red wine contains more than 200 different polyphenolic compounds, it is still unclear which substances are responsible for this effect. We investigated the effect of high molecular weight polyphenols (HMWP), low molecular weight polyphenols (LMWP) and total polyphenolic extracts from red wine (WE) on colon carcinogenesis. We also tested the effect of 4-OH-coumaric acid, a potent phenolic antioxidant present in wine and fruit. F344 rats were treated weekly with 1,2-dimethylhydrazine (DMH) (30 mg/kg b.w. subcutaneously x 10 times). One week after the final DMH injection rats were divided into five groups and fed: a) a high fat (HF) diet containing 23% corn oil (w/w), as control or the same basal diet supplemented with b) 0.11 % (w/w) WE; c) 0.027% (w/w) HMWP d) 0.083% (w/w) LMWP or e) 0.1 % (w/w) 4-OH-coumaric acid. The dietary treatments continued until sacrifice, 16 weeks after the last DMH injection. WE treated rats had significantly fewer (p < 0.05) colorectal adenomas than controls, while rats in other treatment groups did not differ significantly from controls (colorectal adenomas/rat were: 2.2 +/- 0.3; 1.4 +/- 0.2; 2.9 +/- 0.5; 2.6 +/- 0.4; 2.3 +/- 0.3; in controls, WE, HMWP, LMWP and 4-OH-coumaric acid groups, respectively; means +/- SE). The mean number of colorectal carcinomas per rat was similar among all experimental groups. Proliferative activity in the normal colon mucosa did not vary among experimental groups. Total polyphenolic extracts (WE) from red wine, but neither the HMWP nor the LMWP, have some inhibitory effect on the process of colon carcinogenesis by DMH reducing the number of adenomas.

Dietary conjugated linoleic acid increases the mRNA ratio of Bax/Bcl-2 in the colonic mucosa of rats

Previously we have shown that dietary conjugated linoleic acid (CLA) significantly decreased colon tumor incidence in rats injected with 1,2-dimenthylhydrazine (DMH). The present study was performed to explore the mechanisms responsible for the anticarcinogenic effect of CLA. Four groups of rats received either vehicle or intramuscular injections of DMH at the dose of 15 mg/kg body weight twice per week for 6 weeks and were fed a diet containing either 0% or 1.0% CLA ad libitum for 14 weeks. Dietary CLA decreased cellular proliferation and induced apoptosis in the colonic mucosa of both vehicle and DMH-treated rats. Mucosal levels of prostaglandin (PG) E 2, thromboxane B 2, and 1,2-diacylglycerol decreased in rats fed the 1% CLA diet, whereas cyclooxygenase-2 levels were not affected. Arachidonate content of mucosal phospholipids decreased significantly in rats fed the 1% CLA diet. Reverse transcriptase–polymer chain reaction analysis revealed that the Bax/Bcl-2 transcript ratio was significantly increased in rats fed 1% CLA. To examine whether the 1% CLA diet reduces tumor incidence, the DMH-treated rats were continuously fed the assigned diets for 30 weeks. Tumor incidence was significantly decreased in the CLA-fed group. In conclusion, our findings are consistent with the hypothesis that CLA decreases the incidence of colon cancer by decreasing cellular proliferation and inducing apoptosis of the colonic mucosa. These effects may be due in part to decreased PGE 2 levels and increased Bax/Bcl-2 ratios.

Effect of coconut cake on the bacterial enzyme activity in 1,2-dimethyl hydrazine induced colon cancer

Background: Colon cancer is one of the most common forms of malignant tumors in humans, and its incidence is increasing. Since the intestinal microflora is directly in contact with the colonic cells, the enzymes of the bacterial microflora may also play a role in colon carcinogenesis. We studied the activity of bacterial enzymes in experimental colon cancer. Methods: Twenty milligrams per kilogram body weight of 1,2-dimethyl hydrazine (DMH) was administered subcutaneously once a week for first 15 weeks and then discontinued. Coconut cake (25%) was mixed in the diet and given to 30 rats to study the diet effect throughout the experimental period. After 30 weeks, the macroscopic findings in the colon as well as the incidence of tumors in 30 rats was recorded in each group and the activity of β-glucuronidase and mucinase was estimated in the tissues, colon and fecal contents of 10 rats per group . Results: Average number of tumors in the colon as well as the incidence of cancer was significantly increased in DMH-treated rats which was markedly reduced on supplementing coconut cake. DMH injections significantly elevated both the activities of β-glucuronidase (distal colon, distal intestine, liver and colon contents) and mucinase (colon and fecal contents) as compared to the control rats. The increase in β-glucuronidase activity may augment the hydrolysis of glucuronide conjugates, liberating the toxins, while the increase in mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Coconut cake supplementation to DMH-treated rats significantly decreased the incidence and number of tumors as well as the activity of β-glucuronidase and mucinase. Conclusions: Coconut cake has a protective effect against DMH induced colon cancer by virtue of its ability to lower the activities of the microbial enzymes β-glucuronidase and mucinase.

Epitalon and colon carcinogenesis in rats: Proliferative activity and apoptosis in colon tumors and mucosa

The effect of the synthetic pineal peptide Epitalon (Ala-Glu-Asp-Gly) on proliferative activity in colon tumors, and in mucosal epithelial cells adjacent to and located far from tumors was studied in rats. To evaluate the effect of Epitalon on different stages of carcinogenesis, different treatment regimens were used: during the tumor initiation stage, during the tumor-promotion stage, or during the entire process of tumor development. Eighty 2-month-old male LIO rats were exposed weekly to five subcutaneous injections of 1,2-dimethylhydrazine (DMH) at a single dose of 21 mg/kg body weight. Rats were divided into four groups. Control rats (group 1) received saline at a dose of 0.1 ml during the entire experiment. Rats in group 2 were treated with Epitalon at a dose of 1 micro g, five times a week, for 6 months, from the first injection of DMH till the end of the experiment. Rats in group 3 were treated with Epitalon after termination of the carcinogen injections. Rats in group 4 were treated with Epitalon only during the period of DMH exposure (for the first 5 weeks of the experiment). DMH induced proliferation of the secretory epithelium, and this phenomenon was accompanied by a decrease in the size of the stromal area and the area of lymph infiltration in colon tumors and in the colon mucosa adjacent to the tumors (group 1). Epitalon attenuated this effect, especially when the treatment was continued throughout the experiment (group 2). It increased the stromal areas, as well as that of lymphoid infiltration in the colon mucosa adjacent to the tumors. The intensity of lymphoid infiltration was activated in both the colon mucosa adjacent to a tumor and in the tumor. Mitotic activity of tumor cells was significantly inhibited by Epitalon when the treatment was given throughout the experiment (group 2). In parallel, a high level of apoptosis was seen in the same group. Thus, the strongest inhibitory effect of Epitalon on carcinogenesis in the colon mucosa was manifested when the treatment was continued throughout the experiment.

Rapid induction of colorectal tumors in rats initiated with 1,2-dimethylhydrazine followed by dextran sodium sulfate treatment.

To establish a rapid bioassay system with neoplastic end-points for detection of colorectal carcinogenesis modifiers, we evaluated the effects of dextran sodium sulfate (DSS) treatment on the different stages of carcinogenesis in rats initiated with 1,2-dimethylhydrazine (DMH). F344 male rats were given three subcutaneous injections of DMH (40 mg/kg body weight) in a week, and were administered drinking water containing 1.0% DSS ad libitum either during or after the initiation period for a week, or both during and after initiation periods for 2 weeks. At the 10th week of the experiment, although the numbers of aberrant crypt foci were significantly decreased in all groups treated with DSS and given DMH-initiation as compared with DMH alone, dysplastic foci/adenomas/adenocarcinomas were increased. The incidences and multiplicities of these lesions were highest in rats treated with DSS after DMH-initiation period. At the 26th week, the incidences of adenocarcinomas (100 vs. 20% in DMH alone) and their multiplicities (6.6 +/- 0.8/rat vs. 0.2 +/- 0.4/rat in DMH alone) were also highest in this group. These results indicate that short-term DSS-treatment in the post-initiation period significantly accelerates DMH-induced colorectal tumor development in rats, so that this protocol may effective for establishment of a rapid bioassay system with neoplastic end-points.

High susceptibility of nullizygous p53 knockout mice to colorectal tumor induction by 1,2-dimethylhydrazine.

The susceptibility of male p53 nullizygote (-/-), heterozygote (+/-), and wild-type (+/+) mice to 1,2-dimethylhydrazine (DMH) induction of colon carcinogenesis was investigated. In a preliminary short-term experiment, male mice of three genotypes were given s.c. of 20 mg/kg DMH once weekly for 5 weeks. In a medium-term experiment, mice were given weekly s.c. of DMH for 15 weeks. In a long-term experiment, male p53 (+/-) and (+/+) mice were given weekly injections of DMH for 15 weeks, and killed at week 30. In the medium-term experiment, carcinomas were observed in 70% of p53 (-/-) mice, although there were no carcinomas in p53 (+/+) and (+/-) mice. In the long-term experiment, there was no significant difference in incidences of adenomas and carcinomas between p53 (+/+) and (+/-) mice. PCR-single strand conformation polymorphism analysis of exons 5-8 of p53 gene revealed four mutations in one focal atypia, one adenoma, and two carcinomas, out of 56 colonic proliferative lesions in the medium- and long-term experiments. These results suggest that p53 might not be a direct target of DMH but complete loss of p53 might elevate susceptibility to DMH-induced colorectal carcinogenesis.

Anticarcinogenic effect of bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione a curcumin analog on DMH-induced colon cancer model

1,2-Dimethylhydrazine (DMH) is a toxic environmental pollutant which was reported also to be a colon-specific carcinogen. This study was performed to study the effect of bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione, a bisdemethoxycurcumin analog (BDMC-A) on DMH-induced colon carcinogenesis in male Wistar rats and effects were compared with that of the reference drug, curcumin. Rats were given a weekly subcutaneous injection of DMH (20 mg/kg body weight) in the groin, for 15 weeks. After a total experimental period of 32 weeks (including 2 weeks of acclimatization) tumor incidence was 100% in DMH-treated rats. Tumor was identified histologically as adenocarcinoma. Dysplasia, papillary pattern, cellular pleomorphism and carcinomatous glands were also noticed in DMH-treated rats. However, there was no colonic tumor in DMH+BDMC-A- and DMH+curcumin-treated rats but, lymphocyte infiltrations were observed. The levels of total bile acids and cholesterol in 24 h fecal samples were significantly lower in DMH administered rats when compared to control rats, while, the excretion of bile acids and cholesterol were significantly increased and was near normal levels in DMH+BDMC-A- and DMH+curcumin-treated rats. In DMH-induced tumor bearing rats the levels of colonic and intestinal cholesterol was significantly increased whereas, the levels of phospholipid was decreased with a concomitant increase in the activities of phospholipase A (PLA) and phospholipase C (PLC), compared to untreated control rats. Intragastric administration of BDMC-A and curcumin to DMH administered rats significantly lowered the cholesterol content and raised the phospholipid content and lowered the activities of PLA and PLC towards near normal values. Our study shows that the protective effect of BDMC-A during DMH-induced colon carcinogenesis may be due to its modulatory effects on (i) histological changes, (ii) bile acids, (iii) cholesterol, and (iv) phospholipid metabolism in the target organ. Absence of histological changes in the colon of rats treated with BDMC-A, shows that long term administration of BDMC-A is nontoxic to experimental animals. Our study suggest that BDMC-A may emerge as a potent anticarcinogenic agent against colon cancer. As both BDMC-A and curcumin are equipotent in inhibiting the DMH-induced colon tumor incidence and normalizing histological changes, it could be concluded that the terminal phenolic group and the conjugated double bonds in the central seven carbon change may be responsible for the beneficial effects.

Effect of vanadium on colonic aberrant crypt foci induced in rats by 1,2 dimethyl hydrazine.

To investigate the chemo preventive effects of vanadium on rat colorectal carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Male Sprague-Dawley Rats were randomly divided into four groups. Rats in Group A received saline vehicle alone for 16 weeks. Rats in Group B were given DMH injection once a week intraperitoneally for 16 weeks; rats in Group C, with the same DMH treatment as in the Group B, but received 0.5-ppm vanadium in the form ammonium monovanadate ad libitum in drinking water. Rats in the Group D received vanadium alone as in the Group C without DMH injection. Aberrant crypt foci (ACF) were formed in animals in DMH-treated groups at the end of week 16. Compared to DMH group, vanadium treated group had less ACF (P<0.001). At the end of week 32, all rats in DMH group developed large intestinal tumors. Rats treated with vanadium contained significantly few colonic adenomas and carcinomas (P<0.05) compared to rats administered DMH only. In addition, a significant reduction (P<0.05) in colon tumor burden (sum of tumor sizes per animal) was also evident in animals of Group C when compared to those in rats of carcinogen control Group B. The results also showed that vanadium significantly lowered PCNA index in ACF (P<0.005). Furthermore, vanadium supplementation also elevated liver GST and Cyt P-450 activities (P<0.001 and P<0.02, respectively). Vanadium in the form of ammonium monovanadate supplemented in drinking water ad libitum has been found to be highly effective in reducing tumor incidence and preneoplastic foci on DMH-induced colorectal carcinogenesis. These findings suggest that vanadium administration can suppress colon carcinogenesis in rats.