Caffeic acid 3,4-dihydroxyphenethyl ester prevents colorectal cancer through inhibition of multiple cancer-promoting signal pathways in 1,2-Dimethylhydrazine/dextran sodium sulphate mouse model

OBJECTIVE

To elucidate the potential feature and mechanism of the caffeic acid 3,4-dihydroxyphenethyl ester (CADPE) molecule, which can prevent colorectal cancer (CRC) in the 1,2-Dimethylhydrazine (DMH)/dextran sodium sulphate (DSS)-induced mouse model.

METHODS

Institute of cancer research (ICR) male mice were injected with 20 mg/kg DMH for a week. After that, 2% DSS was administered in the drinking water for another 7 d. The CADPE treatment was given to the DMH/DSS induced male mice at three different periods until their sacrifice. Histopathological examination was used for observing the CRC development at colonic mucosa. Immunohistochemistry (IHC), blood cells smearing and crypt damage scoring methods were used for investigating the anti-inflammation feature of CADPE related to CRC. The reversing targets searching method was applied with artificial intelligence (AI), computer-aided drug designing (CADD) and Ingenuity Pathway Analysis (IPA) techniques for predicting the potential targets and mechanism of CADPE highly related to CRC.

RESULTS

The data indicated that CADPE inhibited CRC tumor development in the colitis-associated DMH/DSS induced mouse model after giving the early treatment. CADPE also impeded the acute inflammation by decreasing the infiltration of neutrophils significantly during the initial stage of CRC development. Finally, our data showed that CADPE prevented CRC by blocking active sites of three pivotal protein targets including epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR) in two major cancer development pathways.

CONCLUSIONS

CADPE effectively prevented CRC at early stage of tumor germination in the DMH/DSS mouse model highly likely due to its anti-acute inflammation characteristic and the ability of blocking EGFR, ERK and mTOR activities in two highly related CRC developing pathways.

Therapeutic role of biogenic silver and gold nanoparticles against a DMH-induced colon cancer model

Colorectal cancer (CRC) ranks third among fatal diseases afflicting mankind globally due to the shortage of primary detection methods and appropriate choice of drugs. Moreover, current treatments such as chemo drugs and radiotherapies create adverse effects and lead to drug resistance. In this context, recent advances in nanomedicine offer novel clinical solutions for colon cancer therapy. The current study denotes the therapeutic roles of biogenic Abutilon indicum silver and gold nanoparticles (AIAgNPs and AIAuNPs) against a 1, 2-dimethyl hydrazine (DMH)-induced CRC in Wistar rats. Following treatment of nanoparticles (NPs), the CRC rats showed great localization of AIAgNPs and AIAuNPs in colon tumors shown by ICP-OES, indicating their bioavailability. The AIAgNPs and AIAuNPs significantly enhanced cellular antioxidant enzyme levels including catalase, SOD, GSH, GPx and reduced lipid peroxidation (LPO) compared to the standard drug paclitaxel. AIAgNPs and AIAuNPs revealed significant protection against metastasis compared to paclitaxel shown in the histopathological study. The important CRC signaling molecules of the Wnt pathway, the β-catenin and Tcf-4 levels were significantly downregulated in AIAgNPs and AIAuNPs treated CRC rats compared to paclitaxel. Furthermore, the expression levels of cleaved apoptotic caspase-9, -8, and - 3 and lamins were significantly upregulated in AIAgNPs and AIAuNPs treated CRC rats compared to paclitaxel. This preclinical study provides substantial insights into the anti-colon cancer roles of biogenic NPs and gives an idea for targeting different cancers.

Effect of Diacerein on HOTAIR/IL-6/STAT3, Wnt/β-Catenin and TLR-4/NF-κB/TNF-α axes in colon carcinogenesis

Colorectal cancer (CRC) is a common malignancy with high mortality and poor prognosis. Diacerein (DIA) is an anti-inflammatory used for treatment of osteoarthritis. We delineated some underlying molecular mechanisms of DIA's anti-carcinogenic effect in CRC using in vivo and in vitro models. Human Caco-2 cells were treated with DIA followed by MTT and Annexin V assays and CRC was experimentally induced using 1,2-dimethylhydrazine. DIA (50 mg/kg/day, orally) was administrated for 8 weeks. The MTT assay confirmed cytotoxic effect of DIA in vitro and Annexin V confirmed its apoptotic effect. DIA resulted in regression of tumour lesions with reduced colonic TLR4, NF-κB and TNF-α protein levels and down-regulated VEGF expression, confirming anti-angiogenic impact. DIA triggered caspase-3 expression and regulated Wnt/β-Catenin pathway, by apparently interrupting the IL-6/STAT3/ lncRNA HOTAIR axis. In conclusion, DIA disrupted IL-6/STAT3/ lncRNA HOTAIR axis which could offer an effective therapeutic strategy for the management of CRC.

Evaluation of immunologic and intestinal effects in rats administered an E 171-containing diet, a food grade titanium dioxide (TiO2)

The toxicity of dietary E 171, a food grade titanium dioxide was evaluated. A recent study reported rats receiving E 171 in water developed inflammation and aberrant crypt foci (ACF) in the gastrointestinal tract. Here, rats received food containing E 171 (7 or 100 days). The 100-day study included feeding E 171 after dimethylhydrazine (DMH) or vehicle only pretreatment. Food consumption was similar between treatment groups with maximum total cumulative E 171 exposure being 2617 mg/kg in 7 days and 29,400 mg/kg in 100 days. No differences were observed due to E 171 in the percentage of dendritic, CD4+ T or Treg cells within Peyer's patches or the periphery, or in cytokine production in plasma, sections of jejunum, and colon in 7- or 100-day E 171 alone fed rats. Differences were observed for IL-17A in colon (400 ppm E 171 + DMH) and IL-12p70 in plasma (40 ppm E 171 + DMH). E 171 had no effect on histopathologic evaluations of small and large intestines, liver, spleen, lungs, or testes, and no effects on ACF, goblet cell numbers, or colonic gland length. Dietary E 171 administration (7- or 100-day), even at high doses, produced no effect on the immune parameters or tissue morphology.

Chemopreventive effects of (-)-hinokinin against 1,2-dimethylhydrazine-induced genotoxicity and preneoplastic lesions in rat colon

(-)-Hinokinin (1) is a dibenzylbutyrolactone lignan obtained by the partial synthesis of (-)-cubebin. This study reports the antigenotoxic and anticarcinogenic potential of 1 by the comet and aberrant crypt focus assays in the peripheral blood and colon of 4-5-week-old Wistar rats, respectively. The rats were exposed to 1,2-dimethylhydrazine (40 mg/kg) and were treated by gavage with doses of 10, 20, and 40 mg/kg of 1. The results showed that the dose of 40 mg/kg was neither genotoxic nor carcinogenic. In the comet assay, all 1 doses displayed antigenotoxic effects. In addition, this compound (20 and 40 mg/kg) exhibited an anticarcinogenic effect in the aberrant crypt focus assay.

Probiotic Escherichia coli CFR 16 producing pyrroloquinoline quinone (PQQ) ameliorates 1,2-dimethylhydrazine-induced oxidative damage in colon and liver of rats

Inflammation of the gastrointestinal tract is associated with reactive oxygen species (ROS) genesis. Alleviation of oxidative stress is achieved by using antioxidants and probiotics. Present study investigates a synergistic effect of the probiotic Escherichia coli CFR 16 containing Vitreoscilla haemoglobin gene (vgb), green fluorescent protein (gfp) gene and pyrroloquinoline quinone (pqq) gene cluster on oxidative stress induced by 1,2-dimethylhydrazine (DMH). Adult virgin Charles foster male rats (3-4 months) weighing 200-250 g were administered with DMH (25 mg/kg body weight, s.c.) twice a week for eight consecutive weeks. Rats receiving only DMH dose showed increased lipid peroxidation in liver and intestinal tissues with reduced activity of antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Oral dose of E. coli CFR 16::vgb-gfp harbouring pqq gene cluster increased rat faecal PQQ concentration by twofold, reduced lipid peroxidation and retained SOD, CAT and GPx activities close to normal levels in liver and colonic tissues following DMH treatment. In addition, significant protection was found in colonic histological sections of these rat groups. This study demonstrates a protective efficacy in the following order: E. coli CFR 16 < E. coli CFR 16::vgb-gfp < vitamin C = PQQ < E. coli CFR 16::vgb-gfp (pqq).

[Hematological effects of the protein kinase inhibitor maleimide derivative in dimethylhydrazin E-induced colorectal carcinogenesis of rats]

The effect of the protein kinase inhibitor maleimide derivative (MI-, 1, 1-(4-Cl-benzyl)-3-CI-4-(CF3-phenylamino)- 1H-pyrrole-2,5-dione) on blood cells of rats with 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis has been studied. Administration of MI-I1 at 2.7 mg/kg for 20 weeks on DMH-induced carcinogenesis prevents anemia, which is a consequence of cancer and complicates it. This is confirmed by a reduction in the numberofreticulocytes (0,19(0,15;0,21)x 10(12)/1)and restoration of mean corpuscular hemoglobin (18,02 (17,44;19,03) pg) and mean corpuscular hemoglobin concentration (309,42 (292,38;318,27) g/L) to a control value (0,17 (0,15;0,19), 18,31 (17,95;18,45), 310,78 (306,25;316,18), respectively) in contrast to the group DMH (0,28 (0,24;0,39); 17,50 (17,00;17,96); 288,10 (284,71;303,73), respectively). MI-I normalizes the number of monocytes (1,40 (0,95;2,50)x 10(9)/L) and platelets (646,32 (575,23;700,50)xl10(9)/L) in the blood after 26 weeks ofexperiment; in the DMH group, the values are significantly higher (1,97 (1,52;2,58), 783,90 (687,64;922,27), respectively) as compared to control group (1,23 (0,94; 1,68), 629,34 (590,19;711,48), respectively). MI- 1 reduces the involvement of these cells in the tumors progression and metastasis. Reduction of the monocytosis and thrombocytosis may be mediated by: 1) a decrease in the number and size of tumors and, consequently, the influence of their cytokines on hematopoietic tissue; 2) suppression of proliferation and differentiation of hematopoietic progenitor cells through inhibiting of receptor protein kinases of vascular endothelial and epidermal growth factors and non-receptor PDKI-, Src- and Syk- kinases, that are involved in hematopoiesis and carcinogenesis.

Non steroidal anti-inflammatory drugs modulate the physicochemical properties of plasma membrane in experimental colorectal cancer: a fluorescence spectroscopic study

According to "fluid-mosaic model," plasma membrane is a bilayer constituted by phospholipids which regulates the various cellular activities governed by many proteins and enzymes. Any chemical, biochemical, or physical factor has to interact with the bilayer in order to regulate the cellular metabolism where various physicochemical properties of membrane, i.e., polarization, fluidity, electrostatic potential, and phase state may get affected. In this study, we have observed the in vivo effects of a pro-carcinogen 1,2-dimethylhydrazine dihydrochloride (DMH) and the two non steroidal anti-inflammatory drugs (NSAIDs); sulindac and celecoxib on various properties of the plasma membrane of colonocytes, i.e., electric potential, fluidity, anisotropy, microviscosity, lateral diffusion, and phase state in the experimentally induced colorectal cancer. A number of fluorescence probes were utilized like membrane fluidity and anisotropy by 1,6-diphenyl-1,3,5-hexatriene, membrane microviscosity by Pyrene, membrane electric potential by merocyanine 540, lateral diffusion by N-NBD-PE, and phase state by Laurdan. It is observed that membrane phospholipids are less densely packed and therefore, the membrane is more fluid in case of carcinogenesis produced by DMH than control. But NSAIDs are effective in reverting back the membrane toward normal state when co-administered with DMH. The membrane becomes less fluid, composed of low electric potential phospholipids whose lateral diffusion is being prohibited and the membrane stays mostly in relative gel phase. It may be stated that sulindac and celecoxib, the two NSAIDs may exert their anti-neoplastic role in colorectal cancer via modifying the physicochemical properties of the membranes.

PI3-kinase/Wnt association mediates COX-2/PGE(2) pathway to inhibit apoptosis in early stages of colon carcinogenesis: chemoprevention by diclofenac

In addition to having anti-inflammatory properties, non-steroidal anti-inflammatory drugs (NSAIDs) inhibit neoplastic cell proliferation by inducing apoptosis. Inhibition of cyclooxygenase-2 (COX-2) seemed to be the principal target of NSAIDs, as it is overexpressed in several cancers and catalyzes the synthesis of prostaglandin E₂ (PGE₂), the critical pro-inflammatory molecule. A major role for phosphatidylinositol-3 kinase (PI3-kinase) pathway activation in human tumors has been more recently established. The present study explored the role of PI3-kinase and Wnt molecular pathways in COX-2 and PGE₂ production as well as NSAIDs' chemopreventive effect in colon cancer. 1,2-dimethylhydrazine (DMH) was used for experimental colon cancer model in rat and diclofenac as the preferential COX-2 selective chemopreventive agent. Expression of caspase-3 and caspase-9 was checked in the colonic tissue by immunofluorescence. A decrease was seen in their expressions, indicative of inhibition of apoptosis in the present model. COX-2 mRNA expression as well as PGE₂ levels was elevated after DMH treatment; however, COX-1 mRNA expression was unaltered as seen by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. DMH also activated PI3-kinase, Akt, Wnt, and β-catenin expressions but reduced the glycogen synthase kinase-3β (GSK-3β) levels. Co-administration of diclofenac with DMH increased the mRNA expression of GSK-3β while inactivating PI3-kinase, Akt, Wnt, and β-catenin. The study suggests that activation of PI3-kinase and Wnt signaling is associated with COX-2/PGE₂ production and in turn inhibition of apoptosis in colon cancer, while diclofenac targeted these pathways to restore apoptosis in the present system.

Anti-proliferative and apoptotic effects of etoricoxib, a selective COX-2 inhibitor, on 1,2-dimethylhydrazine dihydrochloride-induced colon carcinogenesis

In the present study, we assessed effects of etoricoxib, a non-steroidal anti-inflammatory drug, on proliferation and apoptosis in 1,2-dimethylhydrazine dihydrochloride (DMH) induced colon lesion development. Male SD rats were divided into four groups: Group 1 controls receiving the vehicle treatment; Group 2 administered DMH weekly (30 mg/kg body weight, subcutaneously) alone; Group 3, DMH weekly plus etoricoxib (0.64 mg/kg body weight, orally) daily; and Group 4, etoricoxib alone. After six weeks of treatment, animals were sacrificed and colons were analysed for morphological and histopathological features. Well characterized pre-neoplastic aberrations such as multiple plaque lesions, hyperplasia and dysplasia were found in the DMH treated group whereas these features were reduced with co-administration of etoricoxib. To study apoptosis, colonocytes were isolated by metal chelation from colonic sacs and studied by fluorescent staining and further confirmed by DNA fragmentation. The DMH treated animals had fewer apoptotic nuclei as compared to the controls, but numbers were higher with DMH+etoricoxib as well as etoricoxib alone. Expression of proliferative cell nuclear antigen (PCNA), assessed by Western blot analysis and immunohistochemistry, was found to be elevated by DMH treatment group and again reduced by etoricoxib. Results for bromodeoxyuridine incorporation (BrdU) were in agreement. It may be concluded that the drug, etoricoxib, has the potential to act as an anti-apoptotic and anti- proliferative agent in the colon.

Inhibition of 1, 2-dimethylhydrazine-induced mucin-depleted foci and O⁶-methylguanine DNA adducts in the rat colorectum by boiled garlic powder

The scavenging capacity of reactive oxygen species, such as hydroxyl radicals, is reported not to decrease in boiled garlic (an odorless garlic preparation). We therefore examined the modifying effect of boiled garlic powder (BGP) on 1,2-dimethylhydrazine-induced mucin-depleted foci (MDF) and aberrant crypt foci (ACF), preneoplastic lesions, in the rat colorectum. Male F344 rats (5 weeks old) were fed a basal diet, or experimental diets containing 5% or 1% BGP for 5 weeks. One week later, all rats were injected s.c. with DMH (40 mg/kg, once weekly for 2 weeks). At 10 weeks of age, all the rats were sacrificed, and the colorectum was evaluated for MDF and ACF. In rats given DMH and the 5% or 1% BGP diets (Groups 2 and 3), the numbers of MDF decreased significantly in a dose-dependent manner, compared with the DMH and basal diet value (Group 1) (p<0.01). The numbers of ACF in Group 2, but not Group 3, showed a non-significant tendency to decrease. Next, the effects of BGP on the formation of DMH-induced O6-methylguanine (O6-MeG) DNA adducts in rats were studied. Male F344 rats (5 weeks old) were fed the basal diet, or 10% BGP diet for 5 weeks. All rats were injected i.p. once with 40 mg/kg DMH at the end of week 5. The animals were sacrificed 6 hours after DMH injection to analyze the O6-MeG DNA adducts in the colorectal mucosa. Dietary administration of BGP significantly inhibited the O6-MeG DNA adduct levels in the colorectal mucosa, compared with the controls (p<0.01). These results suggested that BGP may exert chemopreventive effects against colon carcinogenesis at least in the initiation stage.

Glycine- and proline-rich glycoprotein regulates the balance between cell proliferation and apoptosis for ACF formation in 1,2-dimethylhydrazine-treated A/J mice

The objective of this study was to investigate the chemopreventive potentials of glycine- and proline-rich glycoprotein (SNL glycoprotein, 150-kDa) isolated from Solanum nigrum Linne on formation of colonic aberrant crypt foci (ACF) induced by 1,2-dimethylhydrazine (DMH, 20 mg/kg) in A/J mice. Administration of SNL glycoprotein inhibited phosphorylation of extracellular signal-regulated kinase (ERK), expression of colonic proliferating cell nuclear antigen (PCNA), and frequency of colonic ACF in DMH-stimulated mice colon carcinogenesis. In addition, SNL glycoprotein increased expression of cyclin-dependent kinase inhibitors (p21(WAF/Cip1) and p27(Kip1)), whereas reduced expression of precursor form of apoptosis-related proteins [pro-caspase-3 and pro-poly(ADP-ribose)polymerase (PARP)] in the mice. Interestingly, the results in this study revealed that SNL glycoprotein has suppressive effects on activity of nuclear factor-kappa B (NF-kappaB), whereas it has stimulatory effect on the expression of p53, accompanying inhibitory effects on expression of NF-kappaBp50, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha in DMH-stimulated ACF formation. Also, SNL glycoprotein has inhibitory effects on the formation of thiobarbituric acid reactive substances (TBARS), on the production of inducible nitric oxide (NO), and on the release of lactate dehydrogenase (LDH) in the mice plasma. Collectively, our findings in this study suggest that SNL glycoprotein has chemopreventive activity via modulation of cell proliferation and apoptosis in DMH-treated A/J mice.

Inhibitory effects of high temperature- and pressure-treated garlic on formation of 1,2-dimethylhydrazine-induced mucin-depleted foci and O(6)-methylguanine DNA adducts in the rat colorectum

High temperature- and pressure-treated garlic (HTPG) has been reported to have enhanced antioxidative and cytotoxic activities. However, there have been no reports on chemopreventive effects using animal cancer models. This study first examined the modifying effects of HTPG on 1,2-dimethylhydrazine (DMH)-induced mucin-depleted foci (MDF) and aberrant crypt foci (ACF), preneoplastic lesions in the rat colorectum. Male F344 rats (5 weeks old) were fed basal diet, or experimental diets containing 1% or 3% HTPG for 5 weeks. One week later, all rats were injected s.c.with DMH (40 mg/kg, once weekly for 2 weeks). At 10 weeks of age, all the rats were sacrificed, and the colorectum was evaluated for MDF and ACF. In rats given DMH and 3% HTPG, the numbers of MDF were decreased significantly as compared with those of rats given DMH alone (p< 0.01), and the numbers of ACF showed a tendency to decrease, although not significantly. Next, the effects of HTPG on the formation of DMH-induced O6-methylguanine (O6-MeG) DNA adducts in rats were studied. Male F344 rats (5 weeks old) were fed the basal diet or 10% HTPG diet for 5 weeks. All rats were injected i.p. once with 40 mg/kg DMH at the end of week 5. The animals were sacrificed 6 hours after DMH injection to analyze the O6-MeG DNA adducts in the colorectal mucosa and liver. Dietary administration of HTPG significantly reduced the adduct levels in the colorectal mucosa and liver, compared with the controls (both p< 0.01). The activities of some detoxification enzymes in the liver of DMH-treated rats were also measured. HTPG significantly reduced the activity of cytochrome P450 (CYP) 2E1, known to be responsible for activation of DMH in rat liver (p< 0.05). In contrast, HTPG significantly enhanced the activities of phase 2 enzymes, quinone reductase (QR) and glutathione S-transferase (GST), in rat liver (both p< 0.05). These results suggested that HTPG might have chemopreventive effects against colon carcinogenesis, at least in the initiation stage.

Effect of non-steroidal anti-inflammatory drugs and the pro-carcinogen 1,2 dimethylhydrazine on the rat intestinal membrane structure and function

The present study was designed to evaluate the effects of three non-steroidal anti-inflammatory drugs (NSAIDs) with varying cycloxygenase selectivities on the small intestinal biochemical composition, function and histology during 1, 2-dimethylhydrazine (DMH) administration. Sprague Dawley male rats were divided into five different groups viz: Group 1 (control, vehicle treated), Group 2 (DMH-treated, 30 mg/kg body weight/week in 1 mM EDTA-saline, subcutaneously), Group 3 (DMH + aspirin-60 mg/kg body weight), Group 4 (DMH + celecoxib-6 mg/kg body weight), Group 5 (DMH + etoricoxib-0.64 mg/kg body weight). After six weeks of treatment, brush border membrane was isolated from the jejunum segment of all the groups and changes in the associated enzymes such as sucrase, lactase, maltase, alkaline phosphatase, membrane lipid composition, fluorescence polarizations of diphenylhexatriene, pyrene excimer formation, histological changes and surface characteristics were studied. The results indicated a significant alteration in the enzyme activity as well as changes in the structure and function of the intestine in the presence of the pro-carcinogen, DMH, which suggests the possible chemopreventive efficacy of NSAIDs against the intestinal cancer.

Insulin, leptin, and adiponectin receptors in colon: regulation relative to differing body adiposity independent of diet and in response to dimethylhydrazine

Obesity has recently become a focus of research to elucidate diet and lifestyle factors as important risk factors for colon cancer. Altered levels of insulin, leptin, and adiponectin have been identified as potential candidates increasing colon cancer risk within the prevailing obesogenic environment. There has been considerable research to characterize signaling via these hormones in the brain, liver, and adipose tissue; however, very little is known of their emerging role in peripheral signaling, particularly in epithelial tissues. This study profiles insulin, leptin, and adipokine receptors in the rat colon, revealing novel microanatomical location of these receptors and thereby supporting a potential role in regulating colonic tissue. Potential involvement of insulin, leptin, and adiponectin receptors in increased risk of colon cancer was investigated using Sprague-Dawley rats, either resistant or susceptible to diet-induced obesity. Regulation of insulin, leptin, and adiponectin receptors as a consequence of differing levels of adiposity was assessed regionally in the colon in response to treatment with the chemical carcinogen 1,2-dimethylhydrazine (DMH). However, significantly increased fat mass, increased levels of plasma insulin, leptin, and triglycerides, previously associated with an increased risk of colon cancer, were not associated with promotion of precancerous lesions in the experimental rats or deregulation of insulin, leptin, or adiponectin receptors. These findings do not support a direct link between the deregulation of insulin and adipokine levels observed in obese rats and an increased risk of colon carcinogenesis.

Survivin and Cyclooxygenase-2 are co-expressed in human and mouse colon carcinoma and in terminally differentiated colonocytes

In the evolution of colon rectal cancer (CRC) the imbalance between cell proliferation and apoptosis is considered one of the prominent causes of tumor induction and/or progression. In order to establish the role of anti apoptotic proteins in colon cancer development, we studied with immunohistochemical techniques the expression of Survivin in a mouse model of colon carcinogenesis induced by 1,2-dimethyl-hydrazine treatment. In this mouse model Survivin was over-expressed during tumor development, showing a distribution mimicking that described in the correspondent human malignancies. We also correlated Survivin distribution with COX-2 and beta-Catenin expression patterns. The co-localization of COX-2/beta-Catenin/Survivin in the same epithelial cells in tumor samples lends credence to possible in vivo regulatory effects of COX-2 and beta-Catenin on the intracellular Survivin levels in mouse and human colon cancer.

Inhibition of large intestinal cancers by celecoxib using a serial sacrifice technique

In this serial sacrifice experiment, celecoxib (C) was administered at a 0.1% dose level, in the diet of female Swiss Webster CFW outbred mice. The animals also received either 1,2-dimethylhydrazine dihydrochloride (1,2-DMH) as ten weekly subcutaneous (s.c.) injections at 20 microg/g body weight or physiological saline (PS) as ten weekly s.c. injections at 0.01 ml/g body weight. Subsequently, the mice were sacrificed at 26 weeks or 35 weeks after the first injection of 1,2-DMH or PS. The number of mice with large intestinal tumors and the total number of these tumors were: Group 1 (1,2-DMH), 29 and 438; Group 2 (C + 1,2-DMH), 18 and 64; and Group 3 (PS), 1 and 1, in the mice sacrificed at 26 weeks. The corresponding tumor incidences in the mice sacrificed at 35 weeks were: Group 1 (1,2-DMH), 30 and 323; Group 2 (C + 1,2-DMH), 23 and 134; and Group 3 (PS), 0 and 0. Histopathologically, the tumors were diagnosed as polypoid adenomas and adenocarcinomas of the cecum, colon and rectum. Celecoxib treatment inhibited the development of large intestinal cancers in mice sacrificed at 26 or 35 weeks after the first injection of the carcinogen.

Effects of VPS extract of Coriolus versicolor on cancer of the large intestine using a serial sacrifice technique

VPS, a hot water extract of the Coriolus versicolor mushroom, was given at a 2% dose level in the diet of female Swiss Webster CFW outbred mice in a serial sacrifice experiment. The mice were also administered either 1,2-dimethylhydrazine dihydrochloride (1,2-DMH) as ten weekly subcutaneous (s.c) injections of 20 microg/g body weight or physiological saline (PS) as ten weekly (s.c) injections of 0.01 ml/g body weight. The animals were sacrificed at 26 weeks or 35 weeks after the first injection of 1,2-DMH or PS. The number of mice with large intestinal tumors and the total number of these tumors were: Group I (1,2-DMH), 29 and 438; Group 2 (VPS + 1,2-DMH), 29 and 344; Group 3 (VPS + PS), 0 and 0; and Group 4 (PS), I and 1, in the mice sacrificed at 26 weeks. The corresponding tumor incidences in mice sacrificed at 35 weeks were: Group 1 (1,2-DMH), 30 and 323; Group 2 (VPS + 1,2-DMH), 29 and 521; Group 3 (VPS + PS), 1 and 2; and Group 4 (PS), 0 and 0. Histopathologically, the tumors were diagnosed as polypoid adenomas and adenocarcinomas of the cecum, colon and rectum. Contrary to expectations, the VPS treatment enhanced the development of large intestinal tumors induced by 1,2-DMH in animals sacrificed at 35 weeks after the first injection of the carcinogen.

Prevention of 1,2-dimethylhydrazine-induced circulatory oxidative stress by bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione during colon carcinogenesis

We have performed this study to investigate the modulatory effect of bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione, a bisdemethoxy curcumin analog (BDMCA) on circulatory lipid peroxidation (LPO) and antioxidant status during 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in male Wistar rats. The effects were compared with that of the reference drug, curcumin. Increased tumor incidence as well as enhanced LPO in the circulation of tumor bearing rats was accompanied by a significant decrease in the level of reduced glutathione and activities of glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). Intragastric administration of BDMCA or curcumin to DMH-treated rats significantly decreased colon tumor incidence and the circulatory LPO, with simultaneous enhancement of GSH content and GPx, GST, SOD and CAT activities. We report that BDMCA exert its chemopreventive effect by decreasing the colon tumor incidence as well as by modulating circulatory oxidative stress in DMH-treated rats through its influence on LPO and antioxidant status. The effects of BDMCA were comparable with that of the reference compound curcumin, a well known anticarcinogen and antioxidant. Thus, it would be suggested that the methoxy group is not responsible for the beneficial effects, however, the terminal phenolic moieties or the central 7-carbon chain may play a role.

A high-fat diet generates alterations in nuclear receptor expression: prevention by vitamin A and links with cyclooxygenase-2 and beta-catenin

Epidemiologic studies suggest that intake of high energy from fat, inducing overweight, increases the risk of cancer development and promotes colon carcinogenesis. It is therefore important to understand which parameters are affected early on by a high-fat diet in order to devise and improve protective nutritional strategies. We investigated the effect of high energy/fat intake on colon mucosa of male Wistar rats induced by a single 1,2-dimethylhydrazine (DMH) injection. Aberrant crypt foci (ACF) were numbered and modifications in cyclooxygenase-2 (COX-2) and beta-catenin levels assessed. Peroxisome proliferator- and retinoic acid-activated receptors (PPAR and RAR, RXR) are key transcription factors regulating gene expression in response to nutrient-activated signals. A short-term study was designed to evaluate whether alterations in mRNA expression of nuclear receptors can be detected at the beginning of the weight gain phase induced by an appetizing hyperlipidic diet (HLD). HLD consumption induced early downregulation of PPARgamma (-33.1%) and RARbeta (-53.1%) mRNA expression concomitant with an increase in levels of COX-2 (+45.5%) and beta-catenin (+84.56%) and in the number of ACF (191.56 +/- 88.60 vs. 21.14 +/- 11.64, p < 0.05). These findings suggest that HLD increases ACF occurrence, possibly through alterations in the mRNA expression profile of nuclear receptors. Moreover, the use HLD rich in retinyl esters or supplemented with all-trans retinoic acid led to a reduction in the number of ACF. Vitamin A also prevented HLD-induced alterations and the increase in levels of COX-2 and beta-catenin. The present observations show a protective role for vitamin A against disturbances associated with HLD exposure in induced colon carcinogenesis.

Chromium-containing biomimetic cation triaqua-mu3-oxo-mu-hexapropionatotrichromium(III) inhibits colorectal tumor formation in rats

The cation [Cr(3)O(propionate)(6)(H(2)O)(3)](+) has recently been found by oral or intravenous administration to increase insulin sensitivity and improve serum lipids in healthy and type 2 diabetic model rats. Serum insulin concentrations and, hence, insulin sensitivity are in part responsible for the relationship between diet and the incidence of colorectal cancer. This strongly suggested that the synthetic cation, which in vitro is able to stimulate insulin receptor tyrosine kinase activity in a fashion similar to the oligopeptide chromodulin, could influence the incidence of colorectal cancer. Consequently, the effects of the cation on the inhibition of colon tumorigenesis induced by 1,2-dimethylhydrazine in male Sprague Dawley rats were examined. Gavage administration of aqueous solutions of the complex (1000 microg Cr/kg body mass daily for 6 months) resulted in significantly decreased colon tumor incidence (P<0.003).

Insulin in aging and cancer: antidiabetic drug Diabenol as geroprotector and anticarcinogen

The effects of new antidiabetic drug Diabenol (9-beta-diethylaminoethyl-2,3-dihydroimidazo-(1,2-alpha)benzimidazol dihydrochloride) on life span and spontaneous tumor incidence in NMRI and transgenic HER-2/neu mice as well as on colon carcinogenesis induced by 1,2-dimethylhydrazine in rats are studied. It is shown that treatment with the drug failed influence body weight gain dynamics, food and water consumption and the body temperature, slowed down age-related disturbances in estrous function and increased life span of all and 10% most long-living NMRI mice. The treatment with Diabenol inhibited spontaneous tumor incidence and increased the mammary tumor latency in these mice. Diabenol treatment slowed down age-related changes in estrous function in HER-2/neu mice, failed influence survival of these mice and slightly inhibited the incidence and decreased the size of mammary adenocarcinoma metastases into the lung. In rats exposed to 1,2-dimethylhydrazine, treatment with Diabenol significantly inhibited multiplicity of all colon tumors, decreased by 2.2 times the incidence of carcinomas in ascending colon and by 3.1 times their multiplicity. Treatment with Diabenol was followed by higher incidence of exophytic and well-differentiated colon tumors as compared with the control rats exposed to the carcinogen alone (76.3% and 50%, and 47.4% and 14.7%, respectively). Thus, the drug increases survival and inhibits spontaneous carcinogenesis in mice and inhibits colon carcinogenesis in rats.

Targeting normal and neoplastic tissues in the rat jejunum and colon with boronated, cationic acrylamide copolymers

A series of boronated cationic copolymers, composed of different ratios of acrylamide, N-acryloyl-3-aminophenylboronic acid and N-acryloyl-diaminoethane (the cationic moiety), were prepared with the intention of localizing boron neutron capture therapy (BNCT) in experimentally induced polyps on the luminal side of the gut of the rat. The goals of this study were to: (a) test the effect of cationization of the boronated copolymers on their uptake by polyps and normal adjacent epithelium; (b) compare the whole rat body distribution of aminophenylboronic acid (APB) and polymeric APB after local application; (c) measure the effect of micro-environmental parameters such as pH, the presence of mucin and cations on the interaction between the APB-copolymers and the epithelium of the rat intestines. Direct analysis of tissue boron levels showed that polymeric APB-uptake was higher in the colonic polyps than in the surrounding normal tissues. Free APB, however, was found in similar quantities in both. When tested in the normal jejunum and colon of the rat, polymeric APB uptake was directly proportional to the molar content of the cationic monomer in the copolymers. The presence of magnesium ions, free boron cationic monomer and mucin interfered with this uptake in a concentration-dependent manner. The uptake was pH-independent at pH 5, 7 and 10. APB accumulation in the colon polyps was inversely proportional to the cationic monomer content in the copolymers, suggesting an increased amount of mucus around the polyps, which probably impeded the electrostatic attachment of the polymer to the malignant tissue. The use polymeric APB for targeting BNCT in perioperative treatment of colorectal carcinoma is suggested, especially in the cases of microscopic residual disease after curative resection.

Age-related loss of EGF-receptor related protein (ERRP) in the aging colon is a potential risk factor for colon cancer

Although in Fischer-344 rats, aging is associated with increased activation of EGF-receptor (EGFR) in mucosa of much of the gastrointestinal tract, including the colon, regulation of this process is poorly understood. We hypothesize that loss of suppressor of EGFR may partly be responsible for this process. To test this hypothesis, we examined the expression of EGFR related protein (ERRP), a recently identified negative regulator of EGFR, in the colonic mucosa during aging and following administration of the colonic carcinogen dimethylhydrazine (DMH) that resulted in the formation of aberrant crypt foci (ACF), which are considered to be precursor of adenoma and carcinoma. In Fischer-344 rats, aging is associated with increased activation of EGFR in the colonic mucosa, as evidenced by 30-35% increase in the levels of tyrosine phosphorylated EGFR in the proximal and distal colon of aged (20-22 months old) than in young (4-6 months old) rats. In contrast, the levels of ERRP in both regions of the colon of aged rats were decreased by 50-60%, compared to their younger counterparts. Administration of DMH, which induced a greater number of ACF in the colon of aged rats than in young animals, resulted in a corresponding reduction in ERRP in the colon. These results suggest that loss of ERRP expression is a common event during aging and early stages of chemically induced colon cancer. We also suggest that loss of ERRP could be a risk factor for developing colorectal cancer in the older population.

Effects of feeding and body weight loss on the 1H-NMR-based urine metabolic profiles of male Wistar Han rats: implications for biomarker discovery

For almost two decades, 1H-NMR spectroscopy has been used as an 'open' system to study the temporal changes in the biochemical composition of biofluids, including urine, in response to adverse toxic events. Many of these in vivo studies have reported changes in individual metabolites and patterns of metabolites that correlated with toxicological changes. However, many of the proposed novel biomarkers are common to a number of different types of toxicity. These may therefore reflect non-specific effects of toxicity, such as weight loss, rather than a specific pathology. A study was carried out to investigate the non-specific effects on urinary metabolite profiles by administering four hepatotoxic compounds, as a single dose, to rats at two dose levels: hydrazine hydrate (0.06 or 0.08 g kg (1)), 1,2-dimethylhydrazine (0.1 or 0.3 g kg (-1)), alpha-napthylisothiocyanate (0.1 or 0.15 g kg(-1)) and carbon tetrachloride (1.58 or 3.16 g kg(-1)). The study included weight-matched control animals along with those that were dosed, which were then 'pair-fed' with the treated animals so they achieved a similar weight loss. The urinary metabolite profiles were investigated over time using 1H-NMR spectroscopy and compared with the pathology from the same animals. The temporal changes were analysed statistically using multivariate statistical data analysis including principal component analysis, partial least squares, parallel factor analysis and Fisher's criteria. A number of metabolites associated with energy metabolism or which are partially dietary in origin, such as creatine, creatinine, tricarboxylic acid (TCA) cycle intermediates, phenylacetylglycine, fumarate, glucose, taurine, fatty acids and N-methylnicotinamide, showed altered levels in the urine of treated and pair-fed animals. Many of these changes correlated well with weight loss. Interestingly, there was no increase in ketone bodies (acetate and beta-hydroxybutyrate), which might be expected if energy metabolism was switched from glycolysis to fatty acid beta-oxidation. In some instances, the metabolites that changed were considered to be non-specific markers of toxicity, but were also identified as markers of a specific type of toxicity. For example, taurine was raised significantly in carbon tetrachloride-treated animals but reduced in the pair-fed group. However, raised urinary bile acid levels were only seen after alpha-napthylisothiocyanate treatment. The methodology, statistical analysis used and the data generated will help improve the identification of specific markers or patterns of urinary markers of specific toxic effects.

Effects of high molybdenum intake on 1,2-dimethylhydrazine-induced intestinal tumors in rats

Wistar male rats, 3 months of age were given ad-libitum a nutritionally adequate diet and demineralized drinking water. The Molybdenum (Mo) and Tungsten (W) were provided in the drinking water at 200 ppm concentration. Intestinal tumors were induced by 1,2-dimethylhydrazine (DMH) given subcutaneously as 16 weekly doses at 20 mg/kg body weight. Mo in the form of (NH4)6 Mo7O24 4H2O or W in the form of (Na2WO4) were provided in the drinking water two months before the first DMH treatment and were continued during 4 months more until the last DMH treatment. Three months after the last carcinogen injection, all animals were sacrificed and examined for intestinal tumors. The number, size and location of the tumors were recorded and the pathology was examined. The addition of Mo to the drinking water induced an increase of hepatic Mo content. At the end of the second month, the hepatic content of Mo was 5.61 ppm, compared with control and W groups (2.18 and 0.96 ppm, respectively). A significantly lower incidence of tumors was observed in the Mo group (47), compared with the control group given DMH alone (105) and W group (113). On the other hand, the Mo group showed a significant decrease in the numbers of multiple tumors per rat.

Enhancement of circulatory antioxidants by fenugreek during 1,2-dimethylhydrazine-induced rat colon carcinogenesis

We have investigated the modulatory effect of fenugreek seeds (a spice) on circulatory lipid peroxidation (LPO) and antioxidant status during 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in male Wistar rats. Enhanced LPO in the circulation of tumor bearing animals was accompanied by a significant decrease in the levels of ascorbic acid, vitamin E, reduced glutathione, glutathione peroxidase, glutathione S-transferase, superoxide dismutase and catalase. Inclusion of fenugreek in the diet significantly decreased LPO with simultaneous enhancement of circulating antioxidants. We report that fenugreek exert its chemopreventive effect by decreasing circulatory LPO and enhancing antioxidant levels.

Summation of initiation activities in the liver after partial hepatectomy

Summation of initiation activities of different carcinogens in the liver after partial hepatectomy (PH) was investigated with reference to induction of glutathione S-transferase placental form (GST-P) positive foci. Firstly, effects of repeated administration of 1,2-dimethylhydradine (DMH) were compared with the results of a single administration of the same total dose (Expt. I). Subsequently, we studied summation of initiation potential with serial administration of DMH with diethylnitrosamine (DEN) or N-bis (2-hydroxpropyl)-nitrosamine (DHPN). In Expt. I, induction of GST-P-positive foci by multiple low-dose administration was equal to that with the single large-dose treatment. In order to avoid toxicity in hepatectomized rats, the low repeated-dose approach appeared superior. In Expt. II, the numbers of GST-P-positive foci in the groups treated with DMH plus DHPN or DMH plus DEN were significantly higher than those in the groups receiving the carcinogens singly. It is concluded that there is summation of initiation potential with doses of a single or multiple carcinogens. These results suggest that the present initiation assay model is useful to investigate summation of initiation activities of various environmental chemicals.

Chemoprevention of 2-amino-1-methyl-6-phenylimidazo- [4,5-b]pyridine-induced colon carcinogenesis by 1-O-hexyl-2,3,5-trimethylhydroquinone after initiation with 1,2-dimethylhydrazine in F344 rats

The aim of this study is to investigate the chemopreventive effects of the synthetic phenolic antioxidant 1-O-hexyl-2,3, 5-trimethylhydroquinone (HTHQ) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-associated colon carcinogenesis in rats after initiation with 1,2-dimethylhydrazine (DMH) in male F344 rats. Groups of 20-22, 6-week-old male F344 rats were given four subcutaneous injections of 40 mg/kg body wt of DMH during the initial 4 weeks. They were then maintained on powdered basal diet containing 0.03% PhIP alone, PhIP together with 0.5 or 0.125% HTHQ, 0.5 or 0.125% HTHQ alone or basal diet for 32 weeks. A small number (1.1 +/- 1.1/rat) of colon tumors were induced by DMH treatment alone. After initiation with DMH, the number of colon tumors was greatly increased to 8.3 +/- 5.6 by the administration of PhIP. Additional treatment with HTHQ dose-dependently decreased the multiplicity of colon adenocarcinomas to 4.9 +/- 2.8 and 2.6 +/- 1.4 with 0.125 and 0.5%, respectively. This treatment similarly reduced atypical hyperplasias of the ventral prostate. Furthermore, HTHQ significantly reduced the multiplicity of duodenal adenocarcinomas induced by DMH + PhIP or DMH alone. Immunohistochemically, HTHQ was revealed to suppress PhIP-DNA adduct formation in the epithelial cells of the colon and prostate in a separate 2 weeks experiment. The present results clearly showed that HTHQ has chemopreventive potential for PhIP-associated colon and prostate carcinogenesis. The observed inhibition may largely be due to interference with PhIP-DNA adduct formation. In addition, HTHQ has been demonstrated to inhibit duodenal carcinogenesis in the post-initiation stage.

Prevention of development of N,N'-dimethylhydrazine-induced colon tumors by a water-soluble extract from cultured medium of Ganoderma lucidum (Rei-shi) mycelia in male ICR mice

The protective effects of a dietary water-soluble extract from cultured medium of Ganoderma lucidum (Rei-shi or Mannentake) mycelia (designated as MAK) against development of colon tumors were investigated in male ICR mice. The animals were given weekly injections of N,N'-dimethylhydrazine (DMH, 10 mg/kg body weight) for the initial 10 weeks to induce colon carcinogenesis, and then fed on diet with or without 5% MAK for 10 weeks. There were no significant differences in incidence and the total number of colon tumors between the groups. However, the MAK diet group demonstrated significantly reduced sizes of tumors in comparison with the MF diet group. Moreover, this was linked to a lowered PCNA positive index and shortening of the germinal region in the colon. beta-catenin positive tumor cell nuclei were also significantly decreased in the MAK group. The present results thus indicate that dietary MAK could act as a potent chemopreventive agent for colon carcinogenesis.

Disturbances of diurnal rhythms of biogenic amines contents in hypothalamic nuclei as an evidence of neurotropic effects of enterotropic carcinogen 1,2-dimethylhydrazine

OBJECTIVES

Our data on the contents of norepinephrine (NE), dopamine (DA) and the metabolite of serotonin 5-hydroxyindoleacetic acid (5-HIAA) measured in the suprachiasmatic nuclei (SCN), preoptic area (PA) and median eminence (ME) of hypothalamus of rats after single subcutaneous injection of 1,2-dimethylhydrazine (DMH) as well as the effect of this carcinogen on formation of reactive oxygen species (ROS) in the PA are presented in this paper.

RESULTS

Diurnal changes of DA in all studied brain structures and of NE in the PA have been observed in the control group. Their morning levels were higher than evening ones. Rhythms of 5-HIAA in the SCN and diurnal changes of ROS formation have been shown to have contrary changes in control. Both the morning (11 a.m.) and evening (11 p.m.) subcutaneous administration of DMH at the dose of 21 mg/kg of body weight resulted in changes of all rhythms observed in control. In some cases a phase shift was found, in others the rhythms of neurotransmitters and ROS formation disappeared entirely.

CONCLUSION

The data obtained confirm the idea of dopaminergic and serotoninergic systems taking part in mechanisms of a response of the hypothalamic nuclei to non-photic stimuli. It is suggested that the effect of DMH on the content and diurnal rhythms of neurotransmitters in the hypothalamic structures under study is due to its affecting activities of the enzymes of biogenic amines synthesis, synaptic transmission, melatonin synthesis and secretion rhythms. The change in ROS formation that is caused by administration of DMH is likely to be due to a disturbance of diurnal rhythms of neurotransmitters that are one of the sources of formation of free radicals in the brain.

Differences in susceptibility to colonic stem cell somatic mutation in three strains of mice

Different species and different strains of animals commonly show very different sensitivities to carcinogenic regimes, which are often unexplained. A major possible contributory factor is variation in susceptibility to mutation, but this has not been directly demonstrated. This study therefore quantified the colonic stem cell mutation frequency in three strains of mice using two carcinogens. Stem cell mutations were identified using loss of function of glucose 6-phosphate dehydrogenase (G6PD) in individual crypts, a technique validated by several previous studies. The carcinogens dimethylhydrazine (DMH) and ethyl nitrosurea (ENU) were given to Balb/C, C57BL/6J, and C3H mice. In response to DMH, Balb/C mice were most susceptible, with approximately double the stem cell mutation frequency found in C3H and more than ten-fold that found in C57BL/6J (3.3+/-0.71 vs. 1.5+/-0.52 vs. 0.28+/-0.8x10(-4)). In response to ENU, Balb/C mice and C3H mice were equally susceptible, showing a stem cell mutation frequency approximately twice that of C57BL/6J (3.1+/-0.4 vs. 3.1+/-0.65 vs. 1.63+/-0.28x10(-4)). The observed differences among the strains with respect to somatic mutation following DMH treatment are likely to be due to the previously documented differences in metabolic conversion to the active metabolite. However, as ENU is a directly acting, rapidly inactivated mutagen, strain differences in response to ENU are unlikely to be due to strain-dependent metabolism of the mutagen and are likely to reflect differences in DNA repair efficiency, or possibly in stem cell kinetics among the strains studied. Susceptibility to the induction of colonic stem cell mutation is an important factor in susceptibility to carcinogens, whether due to differences in DNA repair or to other factors. Direct quantification of stem cell mutation frequency allows the separate identification of this component of the carcinogenic cascade and shows that it can make a major contribution to the differing susceptibility of different mouse strains.

Role of cytochrome P450 in DNA damage produced by treatment of colon cells with 1,2-dimethylhydrazine

Human colon cells (LS174T) were treated with the model colon carcinogen 1,2-dimethylhydrazine (DMH) to determine the production of O(6)-methylguanine DNA adducts. Three known P450 inducers (benzanthracene, pyrazole and phenobarbital) were used to produce different P450 environments in each group of cells prior to treatment with DMH. An increased level of DNA damage of different degrees above uninduced levels was observed in all treated groups. Inhibition of the natural protection systems (glutathione and O(6)-methyltransferase) were also included in the study. Glutathione apparently is not of significant protection against DMH damage in colon cells challenged with DMH. In contrast methyltransferase does exert a protective role in this type of cells by reducing the extent of DNA O(6)-methylguanine adduct formation in colon cells following induction of different panels of cytochrome P450 isoforms.

Melatonin and colon carcinogenesis. IV. Effect of melatonin on proliferative activity and expression of apoptosis-related proteins in the spleen of rats exposed to 1,2-dimethylhydrazine

The suppression of 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis by melatonin was previously demonstrated. The objective of the present work was to evaluate histologically and immunohistochemically the splenic immune response to the induced cancer and to melatonin. Spleens from rats, either untreated, injected with DMH, fed with melatonin or treated with both carcinogen and melatonin, were studied. The exposure to the carcinogen and the consequential carcinogenesis resulted in splenic changes that reflected the insufficiency of the immune response, as manifested in significant reduction of the white pulp and the simultaneous expansion of the red pulp. The effects of melatonin on most splenic components were inverse to those of DMH. The anti-carcinogenic properties of melatonin were evidenced from the reversal of the inhibitory effects of DMH, especially when the densities of lymphocytes in different parts of the spleen were compared. The combined treatment of the rats with DMH and melatonin resulted in the expansion of the splenic zones by 106% to 125%, compared to those from DMH-treated rats, and the numbers of CD8+ lymphocytes and Fas-positive cells increased sharply. Therefore we conclude that anti-carcinogenic effects of melatonin are related to activation of several elements of the host's lymphatic system.

Formation and persistence of O(6)-methylguanine in the mouse colon following treatment with 1,2-dimethylhydrazine as measured by an O(6)-alkylguanine-DNA alkyltransferase inactivation assay

Female SWR mice were treated with 1,2-dimethylhydrazine (DMH: 6.8 mg/kg i.p. injection) once weekly for up to 10 weeks, a dosing regime that produced tumours principally within the distal colon (Jackson et al., 1999. Carcinogenesis 20, 509-513). O(6)-Methylguanine (O(6)-MeG) levels, measured using a simple [3H]-based O(6)-alkylguanine-DNA alkyltransferase (ATase) inactivation assay, ranged from 0.6 to 16.7 fmol/microg DNA with: (i) highest levels in the distal colon; and (ii) higher levels after 68 mg/kg total DMH than 6.8 mg/kg DMH. Basal ATase activity varied between 0.97 and 1.22 fmol/microg DNA within the colon but was not associated with adduct levels or tumour induction. After 6.8 mg/kg DMH, the half life of O(6)-MeG in colonic tissue was 36-42 h whereas after 68 mg/kg DMH, t1/2 was approximately 25, 57 and 96 h in the proximal, mid and distal colon, respectively. Tumour induction was thus associated with the levels and persistence of O(6)-MeG in the distal colon.

Effects of intestinal bacteria on the development of colonic neoplasm II. Changes in the immunological environment

To study the effects of intestinal bacteria on the development of colonic neoplasm, we have established gnotobiotic mice with a single species of intestinal bacteria. In the previous study, the incidence of colonic adenoma induced with 1,2-dimethylhydrazine (DMH) in the gnotobiotic mice with Lactobacillus acidophilus, gnotobiotic mice with Escherichia coli and germ-free mice were 30, 50 and 74%, respectively. In this study, 7-week-old mice in each group were sacrificed without the administration of DMH to examine the constituents of immuno-competent cells in various mouse organs using flow cytometry. In the gnotobiotic mice, CD3 intermediate interleukin (IL)-2Rbeta positive cells were observed predominantly in the liver. In the gnotobiotic mice with L. acidophilus, Mac-1 positive Gr-1 positive cells were observed predominantly in the colonic lamina propria. The activation of extrathymic T cells in the liver and granulocytes in the colonic mucosa may be related to anti-neoplastic effects of L. acidophilus in this experimental model.

Gastric tumor induction by 1,2-dimethylhydrazine in Wistar rats with intestinal metaplasia caused by X-irradiation

Five-week-old male Wistar rats were X-irradiated with a total of 20 Gy in 2 equal fractions at a 3-day interval. 1,2-Dimethylhydrazine (DMH) solution was injected i.m. into the back musculature at a dose of 20 mg/kg body weight weekly for 10 weeks, beginning 20 weeks after the final irradiation. Twelve months after the initial carcinogen treatment, tumors in the fundus of the glandular stomach were observed in 5 of 23 animals receiving both X-irradiation and DMH treatment. No tumors of the glandular stomach were observed in the DMH and X-ray alone or nontreatment groups. It is concluded that the presence of intestinal metaplasia may increase sensitivity to the induction of gastric tumors by carcinogens like DMH.

Effects of low doses of carcinogen and different antibodies on the splenic lymphoid system of p53 transgenic mice: morphometric and immunohistochemical studies

The role of the splenic immune system in the development of high sensitivity of p53 transgenic mice to low doses of carcinogen and vaccination was investigated immunohistochemically and morphometrically. Spleens were obtained from human p53 promoter-chloramphenicol acetyl transferase transgenic mice, grouped as follows: 1, untreated controls; 2, exposed to dimethylhydrazine (DMH); 3, and 4, vaccinated with polyclonal antibodies to soluble-53 kDa protein (s53); 5, vaccinated with monoclonal PAb DO1; 6, vaccinated with monoclonal PAb 421; 7, vaccinated with polyclonal alphaH-p53 antibody. Mice in groups 4-7 were treated with DMH after the course of vaccination. Six months later all the mice were tumor-free, but effects of the low dose carcinogen were distinct in the splenic immune system. They were mainly manifested in blast transformation: the total number of lymphocytes and lymphoblasts decreased to 56.5% of the controls. The total of lymphoid cells in the follicles (B zone) and periarterial lymph sheath (T zone) declined, reflecting moderate insufficiency of the spleen's lymphoid system. Vaccination of transgenic mice with antibodies to soluble-p53 elicited mainly a B system response, with lesser T system involvement. Only few signs of B system insufficiency were found in these mice. Vaccination of mice with different antibodies, with subsequent carcinogen treatment, caused changes in the spleen that were similar to those described for DMH alone, but varied with different anti-p53 antibodies. Vaccination with polyclonal antibodies to soluble-p53, or with monoclonal antibodies PAb DO1 or PAb 421, stimulated the splenic activity of T system, and therefore can decrease the tumorigenic effect of carcinogens.

Correlation of neomycin, faecal neutral and acid sterols with colon carcinogenesis in rats

High fat diets have been implicated in incidence of colon cancer both in epidemiological and animal studies. Present investigation deals with the incidence, location and numbers of large and small bowel tumours induced by 1,2-dimethyl hydrazine (DMH) in rats fed high fat diets and neomycin. Neomycin was used to modify the faecal sterol metabolism and the relationship of the high fat diet and faecal neutral and acid sterols to the large bowel tumorigenesis was evaluated. DMH administered rats were fed with (a) 20% safflower oil; (b) 20% safflower oil and neomycin; (c) 20% safflower oil, cholesterol and cholic acid; and (d) 20% safflower oil, cholesterol, cholic acid and neomycin. Neomycin was found to be associated with both increase and decrease of tumour numbers. The faecal sterols lithocholic and deoxycholic acids were found to have no participation, while cholesterol and cholic acid were found to decrease with increase in tumour numbers. However, faecal coprostanol has been found to have a significant positive correlation with tumorigenesis in all dietary groups. Therefore coprostanol might possibly be associated with colon carcinogenesis in DMH-fed rats and cholesterol metabolism in gut appears to be related to the development of tumours.

[Histological and histochemical study of hyperplastic and dysplastic lesions of the large intestine in Cebus Apella (primate) treated with 1,2-dimethylhydrazine]

The main objective of this study was to assess the histological changes of colon ephitelium in Cebus apella induced by 1,2-dimethylhydrazine (DMH) administration. Twelve monkeys, males, (aged x: 30 months) with an average body weight of 2,800 g were utilized. The DMH was injected subcutaneously at 25 mg/kg and continued once a week for 16 weeks. The body weight was assessed once a week during the first 4 months and every 30 days until the end of the experience. Histological changes of intestinal ephitelium and mucins were assessed at the end of the experience in specimens sectioned at 5 microns, stained with Haematoxylin and Eosin, PAS and Alcian blue pH 2.5. The histological and histochemical study permitted to characterize the normal morphology, as well as the mucins characteristics in the three regions: caecum, transverse colon and distal colon. The histological changes in the DMH treated animals were hyperplasia, dysplasia and mucins decreasing. The hyperplastic changes were localizated in glandular crypts, and in the epithelio located over the lymphoid nodules. The dysplastic crypts were observed in the transverse colon and in the last portion of distal colon. These lesions were located in the upper portion as well as the bottom of the mucosa. A decrease of neutral and acids mucopolysaccharides were observed in the crypts. The results of this study suggest that the DMH induced hyperplastic changes in the crypts and in the epithelium located over the lymphoid nodules and dysplastic focus, as well as a decrease of neutral and acids mucopolysaccharides.

Supplementation of Bifidobacterium longum to a high-fat, low-calcium diet lowers cytolytic activity of fecal water in rats injected with 1,2-dimethylhydrazine dihydrochloride

The effects of supplementing Bifidobacterium longum SBT 2928 and Lactobacillus acidophilus SBT 2062 to a high-fat, low-calcium diet on bile acid concentration, fatty acid concentration, cytolytic activity and intestinal alkaline phosphatase (ALP) activity of fecal water in rats injected with and without 1,2-dimethylhydrazine dihydrochloride (DMH) were examined. Male Wistar rats at 8 weeks of age were fed a diet containing 18% coconut oil, 2% corn oil and 0.1% calcium for 15 d. Lyophilized cultures were supplemented to test diets at a concentration of 1%. The feeding of a high-fat, low-calcium diet elevated the bile acid concentration, cytolytic activity and ALP activity of fecal water as compared to the AIN-76A diet, whereas the fatty acid concentration was not changed. None of the cultures had any effect on these parameters. Furthermore, 8 week-old rats were given a single subcutaneous injection of DMH at 40 mg/kg body weight, and fed the same diets for 15 d. The DMH injection had no effect on the bile acid concentration but increased the fatty acid concentration and cytolytic activity of fecal water. In contrast, ALP activity was lower in the DMH-treated rats than in the non-treated rats. The ingestion of B. longum lowered cytolytic activity but had no effect on the bile acids, fatty acids and ALP activity of fecal water. L. acidophilus had no effect on these parameters.

Dietary wheat bran modulates proliferating cell nuclear antigen-labeling index of the rat colorectum after treatment with 1,2-dimethylhydrazine

We investigated whether dietary wheat bran (Wb) influences the proliferating cell nuclear antigen (PCNA)-labeling index (LI) of the colorectum of rats after the injection of 1,2-dimethylhydrazine (DMH). Male Wistar/ST rats were divided into four groups and given either a fiber-free diet or diets supplemented with Wb at the expense of the whole diet (5, 10 or 20 g/100 g diet). Then, they were subcutaneously injected with a single dose of DMH (20 mg/kg body weight) or the vehicle. At four weeks after the treatment, frozen sections of the colorectum were immunostained with anti-PCNA antibody (19F4). In the fiber-free group, DMH treatment significantly increased the PCNA-LI of the distal colon and rectum. Among the DMH treatment groups, the PCNA-LI of the distal colon in the Wb 5 g/100 g diet group was significantly lower than that in the fiber-free group. The PCNA-LI of the distal colon tended to increase as the amount of Wb supplemented was increased in the DMH-treated groups except for the fiber-free group. A similar trend was observed for the rectum. In conclusion, the ingestion of Wb diminished the increase in PCNA-LI in rat colorectum induced by DMH injection.