Glucagon-like peptide-1 (GLP-1) receptor agonism or DPP-4 inhibition does not accelerate neoplasia in carcinogen treated mice

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) are secreted in parallel from the intestinal endocrine cells after nutrient intake. GLP-1 is an incretin hormone and analogues are available for the treatment of type 2 diabetes mellitus (T2DM). GLP-2 is an intestinal growth hormone and is shown to promote growth of colonic adenomas in carcinogen treated mice. Both peptides are degraded by dipeptidyl peptidase-4 (DPP-4) into inactive metabolites. DPP-4 inhibitors are therefore also in use for treatment of T2DM. It is possible that DPP-4 inhibition by enhancing the exposure of endogenous GLP-2 to the intestinal epithelia also might mediate growth and promote neoplasia. We investigated the intestinal growth effect of the GLP-1 receptor agonists (GLP-1 RAs) (liraglutide and exenatide) and DPP-4 inhibition (sitagliptin) in healthy mice. We also investigated the potential tumour promoting effect of liraglutide and sitaglitin in the colon of carcinogen treated mice. We used GLP-2 as a positive control.

METHODS

For the growth study we treated healthy CD1 mice with liraglutide (300 μg×2), exenatide (12.5 μg×2) or vehicle subcutaneously and sitagliptin (8mg×2) or water by oral gavage for 10 or 30 days. We measured intestinal weight, cross sectional area, villus height and crypt depth. For the tumour study we treated carcinogen treated mice (1,2 dimethylhydrazine 21 mg/kg/week for 12 weeks) with liraglutide (300 μg×2), Gly2-GLP-2 (25 μg×2) or vehicle subcutaneously and sitagliptin (8 mg×2) or water by oral gavage for 45 days. We counted aberrant crypt foci (ACF), mucin depleted foci (MDF) and adenomas in the colon. Using COS-7 cells transfected with a GLP-2 receptor, we tested if liraglutide or exenatide could activate the receptor.

RESULTS

In the 10 days experiment the relative small intestinal weight was increased with 56% in the liraglutide group (p<0.001) and 26% in the exenatide group (p<01) compared with vehicle treated mice. After 30 days of treatment, liraglutide did also increase the colonic weight (p<0.01). By morphometry the growth pattern mimicked that of GLP-2. Sitagliptin treatment had only a minor effect. In the carcinogen treated mice we found no increase of ACF in any of the groups, the numbers of MDF and adenomas after liraglutide and sitagliptin treatments were similar to their respective control groups. Neither liraglutide nor exenatide stimulated cAMP release from GLP-2 receptor transfected cells.

CONCLUSION

Both GLP-1 analogues were potent growth stimulators of the healthy mouse intestine. No agonism was found for GLP-1 RAs at the GLP-2 receptor. Despite of the growth effect, liraglutide did not promote dysplasia in the colon. Sitagliptin did not show any tumour promoting effects, and non considerable growth effects.

Effect of complex polyphenols and tannins from red wine (WCPT) on chemically induced oxidative DNA damage in the rat

BACKGROUND

Flavonoids are polyphenolic antioxidants occurring in vegetables and fruits as well as beverages such as tea and wine which have been thought to influence oxidative damage.

AIM OF THE STUDY

We wanted to verify whether a complex mixture of wine tannins (wine complex polyphenols and tannins, WCPT) prevent chemically-induced oxidative DNA damage in vivo.

METHODS

Oxidative DNA damage was evaluated by measuring the ratio of 8-hydroxy-2'-deoxyguanosine (80HdG)/ 2-deoxyguanosine (2dG) x 10(-6) in hydrolyzed DNA using HPLC coupled with electrochemical and UV detectors.

RESULTS

We treated rats with WCPT (57 mg/kg p.o.) for 14 d, a dose 10-fold higher than what a moderate wine drinker would be exposed to. WCPT administration significantly reduced the ratio of 80HdG/2dG x 10(-6) in liver DNA obtained from rats treated with 2-nitropropane (2NP) relative to controls administered 2NP only (33. 3 +/- 2.5 vs. 44.9 +/- 3.2 x 10(-6) 2dG; micro +/- SE; p<0.05). On the contrary, pretreatment with WCPT for 10 d did not protect the colon mucosa from oxidative DNA damage induced by 1, 2-dimethylhydrazine (DMH). 2NP and DMH are hepatic and colon carcinogens, respectively, capable of inducing oxidative DNA damage.

CONCLUSIONS

WCPT have protective action against some types of chemically-induced oxidative DNA damage in vivo.

Ethyl acetate fraction of adlay bran ethanolic extract inhibits oncogene expression and suppresses DMH-induced preneoplastic lesions of the colon in F344 rats through an anti-inflammatory pathway

Adlay ( Coix lachryma-jobi L. var. ma-yuen Stapf) is a grass crop and was reported to possess anti-inflammatory activity and an antiproliferative effect in cancer cell lines. The purpose of this study was to evaluate the effects of the ethyl acetate fraction of an adlay bran ethanolic extract (ABE-Ea) on colon carcinogenesis in an animal model and investigate its mechanism. Male F344 rats received 1,2-dimethylhydrazine (DMH) and consumed different doses of ABE-Ea. The medium-dose group (17.28 mg of ABE-Ea/day) exhibited the best suppressive effect on colon carcinogenesis and prevented preneoplastic mucin-depleted foci (MDF) formation. Moreover, RAS and Ets2 oncogenes were significantly down-regulated in this group compared to the negative control group, whereas Wee1, a gene involved in the cell cycle, was up-regulated. Cyclooxygenase-2 (COX-2) protein expression was significantly suppressed in all colons receiving the ABE-Ea, indicating that ABE-Ea delayed carcinogenesis by suppressing chronic inflammation. ABE-Ea included considerable a proportion of phenolic compounds, and ferulic acid was the major phenolic acid (5206 microg/g ABE-Ea) on the basis of HPLC analysis. Results from this study suggest that ABE-Ea suppressed DMH-indued preneoplastic lesions of the colon in F344 rats and that ferulic acid may be one of the active compounds.

trans-Resveratrol reduces precancerous colonic lesions in dimethylhydrazine-treated rats

trans-Resveratrol, a natural occurring polyphenol, has been described as an antiproliferative and proapoptotic agent in vitro. Here, we studied the effect of trans-resveratrol administered orally at a dose of 60 mg/kg for 49 days on early preneoplastic markers induced by the intraperitoneal injection of 1,2-dimethylhydrazine (20 mg/kg). We measured trans-resveratrol and its derivates by liquid-liquid extraction followed by high-performance liquid chromatography diode array detection analysis in colon contents. Dihydroresveratrol was the most abundant compound in the colon, followed by trans-resveratrol glucuronide and small amounts of trans-resveratrol and its sulfate. The administration of trans-resveratrol decreased aberrant crypt foci by 52%, and mucin depleted foci by 45% in colon. In conclusion, the correlation between the reduction of precancerous colonic lesions and the availability of trans-resveratrol in the colon provides a new insight into the therapeutical potential of this polyphenol and its metabolites.

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).

Inhibition by ginseng of colon carcinogenesis in rats

The inhibitory effects of ginseng on the development of 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) in the colon were investigated in rats. Male, 6-week-old rats were injected with DMH once a week for 4 weeks. Rats in Groups 1 and 2 were fed diets containing red and white ginseng, respectively, at a dose of 1% for 5 weeks, starting one week before the first treatment of DMH. Animals in Groups 3 and 4 received red or white ginseng for 8 weeks starting after DMH treatment. Group 5 served as a carcinogen control group. Numbers of ACF with at least four crypts were significantly reduced in the colon of Group 2 treated with red ginseng combined with DMH. Moreover, rats were injected with DMH 4 times at one-week intervals. They were also fed diets containing 1% red or white ginseng or the control diet throughout 30 days of the experiment. Treatment with red ginseng resulted in a significant decrease of 5- bromo-2'-deoxyuridine labeling indices in colonic crypts comprising ACF. These findings suggest that dietary administration of red ginseng in combination with DMH suppresses colon carcinogenesis in rats, and the inhibition may be associated, in part, with inhibition of cell proliferation, acting on ACF in the colonic mucosa.

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

PURPOSE

The susceptibility of male p53 nullizygote (-/-), heterozygote (+/-), and wild-type (+/+) mice to 1,2-dimethylhydrazine (DMH) induction of colon carcinogenesis was investigated.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Significance of inflammation-associated regenerative mucosa characterized by Paneth cell metaplasia and -catenin accumulation for the onset of colorectal carcinogenesis in rats initiated with 1,2-dimethylhydrazine

Short-term dextran sodium sulfate (DSS) treatment has been shown to notably accelerate colorectal tumor development in rats initiated with 1,2-dimethylhydrazine (DMH). In the present study, to clarify mechanisms underlying the DSS influence, time-course studies of histopathological and immunohistochemical characteristics and beta-catenin gene mutations in colorectal mucosa in early stages of this model were conducted. F344 males were given three subcutaneous injections of DMH (40 mg/kg body wt) within a week, followed by free access to drinking water containing 1% DSS for a week. At weeks 1, 4, 6 and 8 after the DSS treatment, rats were euthanized and colorectal samples were collected. At week 1, the colorectal mucosa demonstrated extensive erosion along with significant inflammatory cell infiltration and neighboring reactive hyperplasia. By week 4, the mucosal damage was repaired and regenerative mucosa, partly characterized by Paneth cell metaplasia and altered subcellular localization of beta-catenin, was apparent. Areas with Paneth cells/beta-catenin accumulation were significantly more likely to be accompanied by interstitial inflammation and 17 of 24 dysplastic foci were found in regenerative mucosa with Paneth cells. Furthermore, adenomas/carcinomas frequently featured various degrees of Paneth cell differentiation. Point mutations mainly in codons 34 and 41 of beta-catenin gene were detected in 6 of 27 samples of regenerative mucosa with Paneth cells and four of nine dysplastic foci/adenomas/carcinomas. These findings indicate that inflammation-associated regenerative mucosa with Paneth cell metaplasia and alteration in the APC/beta-catenin/Tcf signal transduction pathway are possibly involved in the acceleration of colorectal carcinogenesis in this DMH-DSS rat model.

The Antitumor Activity of Ginger against Colorectal Cancer Induced by Dimethylhydrazine in Rats

BACKGROUND

Bowl or colorectal cancer (CRC) is the third most common type of cancer with about two million new cases every year. CRC is the second leading cause of cancer related mortalities.

OBJECTIVE

The study aims to evaluate the anticancer activity of ethanolic Ginger Extract (GE) in HCT-116 colon cells and colorectal tumors induced by dimethylhydrazine (DMH).

METHODS

The antiproliferative activity was measured by MTT assay and the gene expression was assessed by q-RTPCR. For the antitumor study, rats were divided into five groups in random; control, group two was orally treated with 300 mg/kg of GE for 21 weeks, group three was s.c. injected with DMH (20 mg/kg) for 9 weeks, and groups four and five were treated with DMH and then treated with cisplatin (2.5 mg/kg, i.p) or GE, respectively, for 21 weeks.

RESULTS

GE had a significant antiproliferative activity with IC50~ 12.5 µg/ml. GE induced both extrinsic and intrinsic apoptotic pathways. GE induced the expression of FasL, TRAIL, p53, and caspase-8 and downregulated Bcl-2 and survivin genes. Treatment of rats with DMH resulted in 100% tumor incidence and 2.3 tumors/rat. DMH significantly elevated the serum ALT, urea, and creatinine and significantly decreased the body weight gain. DMH also caused significant reductions in the hepatic GSH level, and the activities of catalase, SOD, GST, and GR in the liver as well as the renal GSH content and γ-GT activity. The colon from rats insulted with DMH showed adenomatous polyps with polymorphism and mitosis. The mucosa and submucosa were infested with inflammatory cells while serosa and muscularis were devoid from these cells. However, the muscularis was infiltrated with cystic formation, anaplastic changes, and hemorrhage. GE was able to alleviate all the previous deleterious effects of DMH and it was superior to cisplatin in its ameliorative effects. It did so without eliciting hepatotoxicity or nephrotoxicity which were shown in the group treated with DMH and cisplatin.

CONCLUSION

This study proved that the antitumor activity of GE against the DMH induced-CRC is superior to cisplatin. GE was also safer than cisplatin and did not elicit hepatotoxicity or nephrotoxicity. GE induced apoptosis and has carcinostatic activity.

Effect of Hesperidin against Induced Colon Cancer in Rats: Impact of Smad4 and Activin A Signaling Pathway

SCOPE

To evaluate the chemopreventive efficacy of hesperidin (Hsd) in 1,2-dimethylhydrazine (DMH)-induced colorectal cancer (CRC) and demonstrate its role in mothers against decapentaplegic homolog 4(Smad4) and activin A signaling pathways.

METHODS AND RESULTS

A CRC rat model was established by DMH exposure, and the animals were randomly divided into five groups: Control group, Hsd, DMH, DMH + Hsd, and DMH followed by Hsd. The resected colon was subjected to macroscopic, microscopic, molecular, histopathological, and immunohistochemical examination. Activin A, Smad4, malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), and superoxide dismutase (SOD) levels in tissues were also measured. The DMH group exhibited a significant increase in the gene and protein expression of activin A as well as MDA and NO levels in tissues. There was a significant reduction in the gene and protein expression of Smad4 as well as GSH and SOD levels in tissues. Administration of Hsd significantly upregulated Smad4 and activin A gene expressions in both the DMH + Hsd and DMH followed by Hsd groups. Moreover, Hsd improved the antioxidant status of the former two groups.

CONCLUSION

This study demonstrated the chemopreventive effect of Hsd against CRC by modulating Smad4 and activin A signaling in vivo. Further studies are needed to demonstrate its clinical value and explore its possible role in advanced malignancy.

Failure to induce tumors in the large intestine of Capuchin mokeys (Cebus apella) by using 1,2-dimethylhydrazine

The purpose of this study was to produce tumors in the large intestine of Capuchin Monkeys (Cebus apella) by the administration of the colonotropic carcinogen 1,2-dimethylhydrazine (DMH). The subjects were 12 monkeys, all males, age 30 months, with a mean weight of 2.858 kg. The DMH was administered subcutaneously to six of the monkeys at a dosage of 25 mg/kg of body weight once a week for 16 weeks; control monkeys received an equivalent volume of the stock solution without DMH. Twenty months after administration of the first dose, the animals were sacrificed. None of the monkeys showed intestinal tumors. Samples of the gastrointestinal tract were removed, fixed, and stained according to standard histological techniques. Histological changes were seen in all of the DMH-treated animals; these consisted of glandular hyperplasia and hyperplasia of the epithelium overlying the lymphoid nodules. In addition, foci of dysplasia were found in three of the animals. Our results suggest that the DMH induced pre-neoplastic changes, characterized by hyperplasia and dysplasia, in the mucosa of the large intestine.

Cancer chemopreventive potential of the Egyptian flaxseed oil in a rat colon carcinogenesis bioassay--implications for its mechanism of action

The possible chemopreventive effects of natural Egyptian flaxseed oil on preneoplasia and cancer formation were investigated in a rat medium-term colon carcinogenesis bioassay. Male Wistar rats were divided into 6 groups. Groups 1, 3 and 5 were initiated by 1,2-dimethylhydrazine (DMH) 20 mg/kg body weight s.c. 8 times, twice a week to initiate colon carcinogenesis. Groups 1 and 3 received 20% or 5% flaxseed oil respectively in diet in post initiation stage until the end. Groups 2 and 4 served as a flaxseed dose corresponding controls without carcinogen initiation, while rats in group 6 served as negative controls. Distribution and total numbers of aberrant crypt foci (ACF), putative preneoplastic lesions, particularly those with ≥4 aberrant crypts (ACs), and the numbers and sizes of colon tumors (adenoma and carcinoma) were significantly decreased by both treatment doses of flaxseeds as compared to group 5. Histochemical investigation revealed that the numbers of mucus-secreting cells in the colonic mucosa were reduced gradually during progression of colon carcinogenesis. Intriguingly, flaxseed oil caused the numbers and integrity of the mucus-secreting cells to retain close to normal levels and in a dose dependent manner. Moreover, the hematological parameters were almost constant between the groups particularly at the dose of 5% as compared to groups 5 and 6. PCNA-labeled indexes (PCNA-LI) in the DMH-initiated colonic mucosa were found to be decreased by both doses of flaxseeds administration. In conclusion, the present study showed that the post initiation dietary administration of flaxseeds oil suppressed DMH-induced colon carcinogenesis in rats without significant side effects. The mechanism is likely to be through its inhibitory effects on early cellular proliferation and modulation of mucin secretion properties in the initiated colonic mucosa.

Panx1 knockout promotes preneoplastic aberrant crypt foci development in a chemically induced model of mouse colon carcinogenesis

Colorectal cancer, which is the third leading cause of cancer-related deaths worldwide, is a multistep disease, featuring preneoplastic aberrant crypt foci (ACF) as the early morphological manifestation. The roles of hemichannel-forming transmembrane Pannexin 1 (Panx1) protein have not been investigated in the context of colon carcinogenesis yet, although it has contrasting roles in other cancer types. Thus, this study was conducted to examine the effects of Panx1 knockout (Panx1-/- ) on the early events of chemically induced colon carcinogenesis in mouse. Wild type (WT) and Panx1-/- female C57BL6J mice were submitted to a chemically induced model of colon carcinogenesis by receiving six intraperitoneal administrations of 1,2-dimethylhydrazine (DMH) carcinogen. Animals were euthanized 8 h (week 7) or 30 weeks (week 37) after the last DMH administration in order to evaluate sub-acute colon toxicity outcomes or the burden of ACF, respectively. At week 7, Panx1 genetic ablation increased DMH-induced genotoxicity in peripheral blood cells, malondialdehyde levels in the colon, and apoptosis (cleaved caspase-3) in colonic crypts. Of note, at week 37, Panx1-/- animals showed an increase in aberrant crypts (AC), ACF mean number, and ACF multiplicity (AC per ACF) by 56%, 57% and 20%, respectively. In essence, our findings indicate that Panx1 genetic ablation promotes preneoplastic ACF development during chemically induced mouse colon carcinogenesis, and a protective role of Panx1 is postulated.

EFFECT OF DRY EXTRACT FROM REISHI MUSHROOMS ON THE STATE OF ANTIOXIDANT SYSTEM IN RATS WITH DMH-INDUCED COLON CARCINOGENESIS

OBJECTIVE

The aim: To study pro- and antioxidant systems indicators in rats with chemically induced colon carcinogenesis on the background of the reishi mushrooms dry extract use.

PATIENTS AND METHODS

Materials and methods: The study was performed on 120 white male rats. Chronic oncogenic intoxication was modeled by administering 1,2-dimethyl¬hydrazine (DMH) hydrochloride for 30 weeks (1 time per week). A dry extract from the reishi mushrooms was administered intragastrically daily at a dose of 100 mg/kg of the animal's body weight. Blood and liver samples were taken for research monthly. The state of the pro- and antioxidant systems was studied by the content of oxidative modification of proteins products, superoxide dismutase and catalase activity, contents of reduced glutathione and ceruloplasmin.

RESULTS

Results: An increase in the activity of free radical oxidation processes after DMH-induced colon carcinogenesis in rats is evidenced by a decrease in the super-oxide dismutase activity, catalase activity, content of reduced glutathione, an increase in the content of ceruloplasmin and products of oxidative modification of proteins in the blood serum and liver of animals. The effectiveness of the dry extract of reishi mushrooms and its positive effect on the state of pro- and antioxidant systems was experimentally proved.

CONCLUSION

Conclusions: The use of the dry extract of reishi mushrooms under conditions of DMH-induced colon carcinogenesis in rats led to normalization of the anti¬oxidant protection system state and the reduction of oxidative stress.

NANOPARTICLES AND COLORECTAL CANCER: CAN THE USE OF METAL NANOPARTICLE COMPOSITIONS AFFECT OXIDATIVE STRESS MARKERS AND COLON HISTOLOGICAL CHANGES UNDER DMH-INDUCED CARCINOGENESIS

Colorectal cancer (CRC) - a significant global health challenge. Exploring biological markers of oxidative stress is crucial, as they can play an essential role in initiating the transition from an organ's "healthy state" to a "malignant injury." There is substantial promise in investigating the level of 8-isoprostane (8-isoPGF2α) as a novel and dependable marker of oxidative stress. This paper presents that 8-isoprostane levels have been linked to the development of severe structural changes in the colon wall, accompanied by endogenic intoxication syndrome. The obtained results prove the strong connection between oxidative stress and carcinogenesis progression. Our research further illustrates the favorable and potentially beneficial impact of the Au/Ag/Fe NPs composition, which can find utility in a diverse range of contemporary applications.