Supplementation with phytoestrogens and insoluble fibers reduces intestinal carcinogenesis and restores ER-ß expression in Apc-driven colorectal carcinogenesis.

Supplementation with phytoestrogens and insoluble fibers has been reported to reduce duodenal polyps in colectomized familial adenomatous polyposis patients, with a mechanism involving, at least in part, upregulation of estrogen receptor-ß subtype, whose expression is lowered during intestinal tumorigenesis. These data suggest a protective effect also in the colon, the main target organ for tumorigenesis in familial adenomatous polyposis and a major cancer type in non-familial (sporadic) cancers. Therefore, we tested whether a similar preparation might reduce tumorigenesis in the colon of Pirc rats (F344/NTac-Apc) mutated in the Apc gene and thus, like familial adenomatous polyposis patients, spontaneously developing multiple tumors in the colon. We first demonstrate that estrogen receptor-ß expression in Pirc rat colon is significantly down-regulated compared to age-matched wt rats. Then, Pirc rats aged 1 month were treated for 3 months with Adipol (Adi), a patented preparation containing phytoestrogens and insoluble fibers. Colon tumorigenesis was significantly reduced by Adi treatment (colon tumors/rat were 5.3 ± 0.8 and 2.9 ± 0.3, Mucin Depleted Foci/rat 127 ± 6.6 and 97.1 ± 8.6 in Controls and Adi-treated rats, respectively, means ± SE, P < 0.01). The treatment also normalized colon proliferation pattern along the crypt and significantly increased apoptosis in colon tumors. Estrogen receptor-ß expression was increased by Adi treatment, especially in the tumors. These positive effects suggest that Adipol may be exploited as a chemopreventive agent to reduce cancer risk in familial adenomatous polyposis patients and to postpone prophylactic colectomy. Moreover, given the similarities between familial adenomatous polyposis and sporadic colorectal cancer, it might also be used as chemopreventive agent in colorectal cancer patients at risk.

A flavonoid-rich extract from bergamot juice prevents carcinogenesis in a genetic model of colorectal cancer, the Pirc rat (F344/NTac-Apcam1137).

PURPOSE: To determine the potential of a flavonoid-rich extract from bergamot juice (BJe) to prevent colorectal carcinogenesis (CRC) in vivo. MAIN METHODS: Pirc rats (F344/NTac-Apcam1137), mutated in Apc, the key gene in CRC, were treated with two different doses of BJe (35 mg/kg or 70 mg/kg body weight, respectively) mixed in the diet for 12 weeks. Then, the entire intestine was surgically removed and dissected for histological, immunohistochemical and molecular analyses. RESULTS: Rats treated with BJe showed a significant dose-related reduction in the colon preneoplastic lesions mucin-depleted foci (MDF). Colon and small intestinal tumours were also significantly reduced in rats supplemented with 70 mg/kg of BJe. To elucidate the involved mechanisms, markers of inflammation and apoptosis were determined. Compared to controls, colon tumours from BJe 70 mg/kg-supplemented rats showed a significant down-regulation of inflammation-related genes (COX-2, iNOS, IL-1ß, IL-6 and IL-10 and Arginase 1). Moreover, in colon tumours from rats fed with 70 mg/kg BJe, apoptosis was significantly higher than in controls. Up-regulation of p53 and down-regulation of survivin and p21 genes was also observed. CONCLUSIONS: These data indicate a strong chemopreventive activity of BJe that, at least in part, is due to its pro-apoptotic and anti-inflammatory actions. This effect could be exploited as a strategy to prevent CRC in high-risk patients.

High Sensitivity to Cholic Acid-induced Colonic Tumorigenesis Makes Female PIRC Rats (F344/NTac-Apcam1137) a Suitable Model for Studying CRC-promoting Agents.

BACKGROUND/AIM: Rats of the adenomatous polyposis coli (Apc)-mutated female polyposis in rat (PIRC) (F344/NTac-Apcam1137) model exhibit a low level of intestinal tumorigenesis and are thus potentially exploitable as a model for identifying substances increasing colorectal cancer (CRC). MATERIALS AND METHODS: To test this possibility, we treated such rats with the bile acid (BA) cholic acid (CA) (0.3% w/w in the diet), known to promote CRC, and assessed tumorigenesis. RESULTS: Precancerous colonic lesions (mucin-depleted foci) and intestinal tumors were dramatically increased in CA-treated rats compared to controls (p<0.01). Colon mucosa proliferation was higher and apoptosis lower than those in controls. Expression of nuclear receptor 1h4 (Nr1h4) gene [encoding for BA receptor farnesoid X receptor (FXR)], organic solute transporter beta (Ostb) and fatty acid-binding protein 6 (Fabp6), FXR-dependent BA transporters, were dramatically down-regulated in CA-treated rats. CONCLUSION: CA-increased tumorigenesis in female PIRC rats, with mechanisms involving increased proliferation, reduced apoptosis and marked down-regulation of genes controlling BA homeostasis. Since BAs have been implicated in CRC, we suggest that female PIRC rats can be used to identify CRC-promoting agents.

Morin-dependent inhibition of low molecular weight protein tyrosine phosphatase (LMW-PTP) restores sensitivity to apoptosis during colon carcinogenesis: Studies in vitro and in vivo, in an Apc-driven model of colon cancer.

LMW-PTP has been associated with the development of colorectal cancer (CRC) and with the resistance to chemotherapy in cancer cells. To clarify its role in vivo, we studied LMW-PTP expression in Pirc rats (F344/NTac-Apc am1137 ), genetically prone to CRC and resistant to apoptosis. In the morphologically normal mucosa (NM) of Pirc rats, a dramatic over-expression of LMW-PTP was found compared to wt rats (about 60 times higher). Moreover, LMW-PTP levels further increase in spontaneously developed Pirc colon tumors. To understand if and how LMW-PTP affects resistance to apoptosis, we studied CRC cell lines, sensitive (HT29 and HCT-116), or resistant (HT29R, HCT116R) to 5-Fluorouracil (5-FU): resistant cells over-express LMW-PTP. When resistant cells were challenged with morin, a polyphenol inhibiting LMW-PTP, a fast and dose-related down-regulation of LMW-PTP was observed. 5-FU and morin co-treatment dramatically decreased cell viability, increased apoptosis, and significantly impaired self-renewal ability of all the cancer cell lines we have studied. Similarly, we observed that, in Pirc rats, one-week morin administration (50 mg/kg) down-regulated LMW-PTP and restored the apoptotic response to 5-FU in the NM. Finally, administration of morin for a longer period led to a significant reduction in colon precancerous lesions, together with a down-regulation of LMW-PTP. Taken together, these results document the involvement of LMW-PTP in the process of CRC in vitro and in vivo. Morin treatment may be envisaged as a system to increase the sensitivity to chemotherapy and to prevent carcinogenesis.

Aging related changes in circulating reactive oxygen species (ROS) and protein carbonyls are indicative of liver oxidative injury.

Oxidative stress, defined as an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense mechanisms, plays a major role in inducing oxidative damage and cellular impairment, resulting in a general decline of the physiological functions. The aim of this work was to evaluate age-related changes in circulating ROS levels and plasma protein carbonyls, in very young (2 months aged), young (8 months aged) and in middle age (15 months aged) F344 rats. In addition, the DNA oxidative marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) and the expression of the DNA repair enzymes APE1, OGG1 and UNG genes were also measured in the liver of these animals. We also determined whether systemic oxidative stress reflects oxidative injury at organ level. Our results demonstrate that the increase in circulating ROS and protein carbonyl content occurs as early as middle age. Moreover, increased 8-OHdG in the liver of 15-month-old rats was at least in part associated with a reduced DNA damage repairing capacity as suggested by the down-regulation of APE1 gene expression. In addition, we demonstrated for the first time, that plasma carbonyls and liver 8-OHdG are well correlated, suggesting that plasma protein carbonyls may be used as a surrogate marker of oxidative injury in target organs.

Pomegranate By-Products in Colorectal Cancer Chemoprevention: Effects in Apc-Mutated Pirc Rats and Mechanistic Studies In Vitro and Ex Vivo.

SCOPE: To investigate the effect of pomegranate mesocarp, a polyphenol-rich by-product of juice production, in colorectal cancer (CRC) chemoprevention. METHODS AND RESULTS: A mesocarp decoction (PMD) is administered for 6 weeks in the diet to Pirc rats, mutated in Apc, a key-gene in CRC. Mucin-depleted foci (MDFs), as CRC biomarkers, are reduced in PMD-fed rats compared to controls (MDF/colon: 34 ± 4 versus 47 ± 3, p = 0.02). There is an increase in apoptosis in MDFs from PMD-treated rats compared to controls (2.5 ± 0.2 versus 1.6 ± 0.2, p < 0.01). To elucidate the involved mechanisms, two colon-relevant metabolites of the polyphenolic and fiber PMD components, urolithin-A (u-A) and sodium butyrate (SB), are tested alone or in combination in vitro (colon cancer cells), and ex vivo in adenoma (AD) and normal mucosa (NM) from Pirc rats. u-A 25 µm plus SB 2.5 mm (USB) causes a significant reduction in COX-2 protein expression compared to untreated controls (about -70% in cancer cell cultures, AD, and NM), and a strong increase in C-CASP-3 expression in cells (about ten times), in AD and NM (+74 and +69%). CONCLUSION: These data indicate a chemopreventive activity of PMD due, at least in part, to pro-apoptotic and anti-inflammatory action of its metabolites that could be exploited in high-risk patients.

Astragali radix: could it be an adjuvant for oxaliplatin-induced neuropathy?

Neurotoxicity is a major side effect of platinum derivatives both during and after treatment. In the absence of effective pharmacological compounds, the opportunity to identify safe adjuvant treatments among medicinal plants seems appropriate. Astragali radix is an adaptogenic herbal product recently analyzed in platinum-treated cancer patients. With the aim of evaluating the anti-neuropathic profile of Astragali radix, a previously characterized aqueous (Aqu) and two hydroalcoholic (20%HA and 50%HA) extracts were tested in a rat model of oxaliplatin-induced neuropathy. Repeated administrations significantly reduced oxaliplatin-dependent hypersensitivity with 50%HA, the most effective, fully preventing mechanical and thermal hypersensitivity. Ex vivo, 50%HA reduced morphometric and molecular alterations induced by oxaliplatin in peripheral nerve and dorsal-root-ganglia. In the spinal cord and in brain areas, 50%HA significantly decreased activation of microglia and astrocytes. Furthermore, 50%HA prevented the nephro- and hepato-toxicity induced by the anticancer drug. The protective effect of 50%HA did not alter oxaliplatin-induced apoptosis in colon tumors of Pirc rats, an Apc-driven model of colon carcinogenesis. The hydroalcoholic extract (50%HA) of Astragali radix relieves pain and promotes the rescue mechanisms that protect nervous tissue from the damages triggering chronic pain. A safe profile strongly suggests the usefulness of this natural product in oxaliplatin-induced neuropathy.

Gene Expression Profile of Colon Mucosa after Cytotoxic Insult in wt and Apc-Mutated Pirc Rats: Possible Relation to Resistance to Apoptosis during Carcinogenesis.

Apc-mutated Pirc rats, spontaneously developing intestinal tumours, are resistant to 1,2-dimethylhydrazine- (DMH-) induced colon apoptosis. To understand this phenomenon, we analyzed the expression of genotoxic stress-related genes Mgmt, Gsta1, and Gstp1 in the colon of wt and Pirc rats in basal conditions and 24 h after DMH; plasmatic oxidant/antioxidant status was also evaluated. After DMH, Mgmt expression was increased in both genotypes but significantly only in wt rats; Gsta1 expression was significantly increased in both genotypes. Gstp1 expression did not vary after DMH but was lower in Pirc rats. Moreover, for each genotype, we studied by microarray technique whole gene expression profile after DMH. By unsupervised cluster analysis, 28 genes were differentially modulated between the two genotypes. Among them were interferon-induced genes Irf7, Oas1a, Oasl2, and Isg15 and the transcription factor Taf6l, overexpressed in DMH-treated wt rats and unchanged in Pirc rats. RT-PCR confirmed their overexpression in DMH-treated wt rats and showed a slighter variation in DMH-treated Pirc rats. Taken together, despite a blunted induction of Irf7, Oas1a, and Mgmt, defective apoptosis in Pirc rats 24 h after DMH is not mirrored by major differences in gene expression compared with wt rats.

Effect of butyrate enemas on gene expression profiles and endoscopic/histopathological scores of diverted colorectal mucosa: A randomized trial.

BACKGROUND: A temporary stoma is often created to protect a distal anastomosis in colorectal surgery. Short-chain fatty acids, mainly butyrate, are the major fuel source for the epithelium and their absence in the diverted tract may produce mucosal atrophy and inflammation. AIMS: To investigate whether the administration of sodium butyrate enemas (Naburen(©), Promefarm, Italy) could prevent mucosal inflammation and atrophy and affect gene expression profiles after ileo/colostomy. METHODS: We performed a randomized, double-blind, placebo-controlled clinical trial, in patients with enterostomy performed for inflammatory bowel disease, colorectal cancer or diverticulitis. Twenty patients were randomly allocated to receive 30ml of sodium butyrate 600mmol/L (group A) or saline (group B), b.i.d. for 30 days. RESULTS: In group A endoscopic scores were significantly improved (p<0.01) while mucosal atrophy was reduced or unchanged; in group B mucosal atrophy was increased in 42.8% of patients. Despite the high dose of butyrate used, no short-chain fatty acids were detectable by gas chromatography-mass spectrometry in colorectal biopsies. Group A patients showed up-regulation of genes associated with mucosal repair such as Wnt signalling, cytoskeleton regulation and bone morphogenetic protein-antagonists. CONCLUSION: Butyrate enemas may prevent the atrophy of the diverted colon/rectum, thus improving the recovery of tissue integrity.

Sulindac, 3,3'-diindolylmethane and curcumin reduce carcinogenesis in the Pirc rat, an Apc-driven model of colon carcinogenesis.

BACKGROUND: Recently, we showed that Sulindac (SU; 320 ppm) reduces precancerous lesions in the colon of Pirc rats, mutated in the Apc gene. Surprisingly, previous data in Apc-mutated mice showed that SU, with reported efficacy in Familial Adenomatous Polyposis (FAP), increases colon carcinogenesis. Therefore, we assessed the effect of SU 320 ppm in a long-term carcinogenesis experiment in Pirc rats. Moreover, since side effects of SU hamper its chronic use and a combination of drugs could be more effective and less toxic than single agents, we also studied whether two natural compounds, 3,3'-diindolylmethane (DIM; 250 ppm) and curcumin (CUR; 2000 ppm), with or without lower doses of SU could affect carcinogenesis METHODS: Pirc rats were fed an AIN76 diet containing SU, DIM and CUR and sacrificed at 8 months of age to measure intestinal tumours. Apoptosis and proliferation in the normal colon mucosa, as well as gene expression profile were studied RESULTS: Colon tumours were significantly reduced by SU 320 ppm (62 % reduction over Controls), by DIM and CUR without or with SU 80 and 160 ppm (50, 53 and 58 % reduction, respectively) but not by SU 80 ppm alone. Total tumours (colon and small intestine) were reduced by SU (80 and 320 ppm) and by DIM and CUR. Apoptosis in the normal mucosa was significantly increased by SU 320 ppm, and slightly increased by DIM and CUR with or without SU. A slight reduction in Survivin-Birc5 expression was observed with all the treatments compared to Controls. Proliferative activity was not varied CONCLUSIONS: The results on SU reinforce the validity of Pirc rats to identify chemopreventive products. Moreover, the efficacy of the DIM and CUR combination to lower colon tumours, suggests an alternative strategy to be exploited in patients at risk.

Apc-driven colon carcinogenesis in Pirc rat is strongly reduced by polyethylene glycol.

Polyethylene glycol (PEG) is one of the most powerful agents in reducing chemically induced carcinogenesis in rat colon. However, contrasting results in Min mice dampened the enthusiasm on this potentially strong and virtually safe, cancer chemopreventing agent. Pirc (F344/NTac-Apc (am1137) ) rats carrying a germline heterozygous mutation in the Apc gene, spontaneously develop multiple tumours in the colon thus modelling both familial adenomatous polyposis (FAP) and sporadic colorectal cancer (CRC). Given this similarity, we thought that these rats could be appropriate to test the efficacy of PEG 8000 in reducing carcinogenesis. Pirc male rats aged one month were treated with 5% PEG in drinking water for 2 or 6 months. Precancerous lesions were dramatically reduced after 2 months of PEG treatment (Mucin depleted foci (MDF)/colon were 99 ± 17 and 12 ± 8 in Controls and PEG-treated rats, respectively; p < 0.001; mean ± SD). Similarly, colon tumors were significantly reduced after 6 months of treatment (tumors/rat were 8.1 ± 2.3 and 3.6 ± 2.2 in Controls and PEG-treated rats, respectively; p < 0.05; mean ± SD). Colon proliferation, a parameter correlated to cancer risk, was also significantly lower in PEG-treated rats than in Controls, while apoptosis was not significantly affected. In conclusion, PEG markedly reduces colon carcinogenesis in Pirc rats mutated in Apc; we thus suggest that PEG may be used as chemopreventive agent to reduce cancer risk in FAP and CRC patients.

Multiple mucin depleted foci, high proliferation and low apoptotic response in the onset of colon carcinogenesis of the PIRC rat, mutated in Apc.

PIRC rats (F344/NTac-Apc (am1137) ) mutated in the Apc gene spontaneously develop colon tumors thus mimicking familial adenomatous polyposis (FAP) and sporadic colorectal cancer (CRC) more closely than Apc-based rodent models developing tumors mostly in the small intestine. To understand whether microscopic dysplastic lesions precede the development of macroscopic tumors, PIRC rat colon was examined for the presence of mucin depleted foci (MDF), microadenomas of the rodent and human colon. Few MDF (about 4/animal) were already present in 1-month-old rats and their number rapidly increases to about 250 in 8-month-old rats. These lesions showed Wnt signaling activation (nuclear ß-catenin accumulation) and were dramatically decreased by sulindac (320 ppm), a drug with chemopreventive activity (MDF/rat at 4 months: 156 ± 8 and 38 ± 6 in controls and sulindac-treated rats, respectively, means ± SE, p < 0.001). Since altered proliferation and apoptosis could underlie the early phases of carcinogenesis, we studied these processes in the apparently normal colon mucosa (NM) of 1-month-old PIRC and wt rats. Colon proliferation (PCNA expression) was significantly higher in PIRC rats. Notably, PIRC rat NM showed resistance to apoptosis since it sustained proliferation and had lower apoptosis after a cytotoxic insult with 1,2 dimethylhydrazine. Gene expression of Myc, p21, Birc5, Ogg1, Apex1 and Sod2 were significantly up-regulated in the NM of PIRC rat. The overall results put forward PIRC rat as useful model of colon carcinogenesis, either to study the process itself or to test in vivo chemopreventive agents in both short- and long-term studies.

Long-term treatment with Sitagliptin, a dipeptidyl peptidase-4 inhibitor, reduces colon carcinogenesis and reactive oxygen species in 1,2-dimethylhydrazine-induced rats.

Type 2 diabetes mellitus (T2DM) and insulin resistance (IR) increase colon cancer risk. Antidiabetic drugs stabilizing incretin hormones, such as inhibitors of dipeptidyl peptidase-4 activity (DPP4i), may affect colon carcinogenesis; however, the data remain controversial. Therefore, the authors studied whether long-term administration of the DPP4i Sitagliptin (SITA) affects 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis. Male F344 rats fed a high-fat (HF) diet promoting colon carcinogenesis and IR, were induced with DMH (100 mg/kg × 2 times). One week later, the animals were allocated to two groups: one continuing with HF diet (controls; n = 8) and one receiving SITA (n = 8) mixed in the diet (260 ppm). Body weight, food consumption and glycemia were not affected by SITA. Fifteen weeks after DMH, the number of the precancerous lesions mucin-depleted foci (MDF) was significantly lower in rats treated with SITA [MDF/colon: 9.5 ± 0.9 and 6.4 ± 0.9 in controls (n = 8) and SITA groups (n = 8), respectively; means ± SE, p < 0.05]. Reactive oxygen species in the blood were also significantly lower in the SITA group [6.75 ± 0.69 and 5.63 ± 0.75 (H2 O2 in mM) in controls (n = 5) and SITA (n = 6), respectively; means ± SE, p < 0.05]. Rats treated with SITA had a lower DPP4 activity in the intestine but not in the plasma. Intestine growth morphometric parameters and colon proliferation, as proliferating cell nuclear antigen expression, were not affected by SITA. In conclusion, the results suggest a protective effect of DPP4i against colon carcinogenesis that could be exploited in chemoprevention trials.

Expression of LGR-5, MSI-1 and DCAMKL-1, putative stem cell markers, in the early phases of 1,2-dimethylhydrazine-induced rat colon carcinogenesis: correlation with nuclear ß-catenin.

BACKGROUND: Colon cancer stem cells may drive carcinogenesis and account for chemotherapeutic failure. Although many markers for these cells have been proposed, there is no complete agreement regarding them, nor has their presence in the early phases of carcinogenesis been characterized in depth. METHODS: The expression of the putative markers LGR-5 (leucine-rich-repeat-containing G-protein-coupled receptor 5), MSI-1 (Musashi-1) and DCAMKL-1 (doublecortin and calcium/calmodulin-dependent protein kinase-like-1) was studied in normal colon mucosa (NM), in the precancerous lesions Mucin Depleted Foci (MDF) and in macroscopic tumours (adenomas) of 1,2-dimethylhydrazine-treated rats. Co-localization between these markers and nuclear ß-catenin (NBC), an attributed feature of cancer stem cells, was also determined. Moreover, since PGE2 could increase NBC, we tested whether short-term treatment with celecoxib, a COX-2 inhibitor (2 weeks, 250 ppm in the diet) could reduce the expression of these markers. RESULTS: LGR-5 expression in NM was low (Labelling Index (LI): 0.22 ± 0.03 (means ± SE)) with positive cells located mainly at the base of the crypts. Compared to NM, LGR-5 was overexpressed in MDF and tumours (LI: 4.7 ± 2.0 and 2.9 ± 1.0 in MDF and tumours, respectively, P<0.01 compared to NM). DCAMKL-1 positive cells, distributed along the length of normal crypts, were reduced in MDF and tumours. Nuclear expression of MSI-1, located mainly at the base of normal crypts, was not observed in MDF or tumours. In both MDF and tumours, few cells co-expressed LGR-5 and NBC (LI: 1.0 ± 0.3 and 0.4 ± 0.2 in MDF and tumours, respectively). Notwithstanding the lower expression of DCAMKL-1 in tumours, the percentage of cells co-expressing DCAMKL-1 and NBC was higher than in NM (LI: 0.5 ± 0.1 and 0.04 ± 0.02 in tumours and NM, respectively). MSI-1 and NBC co-localization was not observed. Celecoxib did not reduce cells co-expressing LGR-5 and NBC. CONCLUSIONS: Based on its prevalent localization at the base of normal crypts, as expected for stem cells, and on the overexpression in precancerous lesions and tumours, we support LGR-5, but not MSI-1 or DCAMKL-1, as putative neoplastic stem cell marker. In both MDF and tumours, we identified LGR-5-positive cells co-expressing NBC which could be a subpopulation with the highest stem cell features.

Marie Ménard apples with high polyphenol content and a low-fat diet reduce 1,2-dimethylhydrazine-induced colon carcinogenesis in rats: effects on inflammation and apoptosis.

Inflammation may increase cancer risk, therefore, we studied whether polyphenol-rich Marie Ménard (MM) apples with reported anti-inflammatory activity prevent 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in rats and, likewise whether high-fat (HF) diet promoting carcinogenesis, may affect inflammation. DMH-induced rats were fed for 15 weeks with: an HF diet (23% corn oil w/w); an HF diet containing 7.6% w/w lyophilized MM (apple diet (AD)); a low-fat (LF) diet and an HF diet containing piroxicam (PXC) (0.01% w/w) as control. Mucin depleted foci (MDF), precancerous lesions in the colon, were dramatically reduced in the AD, LF, and PXC groups compared with the HF. Peritoneal macrophage activation, an index of systemic inflammation, was significantly decreased in the AD, LF, and PXC groups. TNF-α, iNOS, IL-1ß, IL-6 m-RNA expression in the colon, as well as CD68 cells and plasmatic PGE2 were lower in the AD, but not in the LF group. Apoptosis in the MDF of both the AD and LF-fed rats was significantly higher than in HF rats. In conclusion, AD has a strong chemopreventive effect, reducing inflammation, and increasing apoptosis, while the chemopreventive effect of the LF diet seems mediated mainly by increased apoptosis in MDF.

Mucin depleted foci, colonic preneoplastic lesions lacking Muc2, show up-regulation of Tlr2 but not bacterial infiltration.

Mucin depleted foci (MDF) are precancerous lesions of the colon in carcinogen-treated rodents and humans at high risk. Since MDF show signs of inflammation we hypothesized that the defective mucous production would expose them to the risk of being penetrated by intestinal bacteria, which can be sensed by Toll-like receptors (Tlrs) and activate inflammatory pathways. To verify this hypothesis we tested the expression of 84 genes coding for Tlrs and associated pathways using RT-qPCR in MDF (n = 7) from 1,2-dimethylhydrazine (DMH)-treated rats. Among the 84 tested genes, 26 were differentially expressed in MDF with 5 genes significantly up-regulated and 21 down-regulated when compared to the normal mucosa. Tlr2, as well as other downstream genes (Map4k4, Hspd1, Irak1, Ube2n), was significantly up-regulated. Among the genes regulating the NFkB pathway, only Map4k4 was significantly up-regulated, while 19 genes were not varied and 6 were down-regulated. Tlr2 protein was weakly expressed both in normal mucosa and MDF. To determine whether inflammation observed in MDF could be caused by bacteria contacting or infiltrating crypts, we performed fluorescence in situ hybridization (FISH) experiments with a rRNA universal bacterial probe. None of the 21 MDF tested, showed bacteria inside the crypts, while among the colonic tumors (n = 15), only one had very few bacteria on the surface and on the surrounding normal mucosa. In conclusion, the up-regulation of Tlr2 in MDF, suggests a link between this receptor and carcinogenesis, possibly related to a defective barrier function of these lesions. The data of FISH experiments do not support the hypothesis that inflammation in MDF and tumors is stimulated by bacterial infiltration.

Sustained proliferation and resistance to apoptosis after a cytotoxic insult are early alterations in rat colon carcinogenesis.

To study the early alterations in carcinogenesis, we determined apoptosis and proliferation in rat mucin depleted foci (MDF), precancerous lesions in the colon under basal conditions and 24 h after treatment with 1,2-dimethylhydrazine (DMH), which induces apoptosis in the colon. Spontaneous apoptosis in MDF was higher than in normal mucosa (Apoptotic Index was 1.61 ± 0.30 and 0.21 ± 0.02 in MDF and normal mucosa, respectively, mean ± SE, p < 0.05). DMH (30 and 75 mg/kg) increased apoptosis in both normal mucosa and MDF (up to 20 times higher compared to basal levels in normal mucosa, but only two times in MDF). MDF had a higher and deregulated pattern of proliferation along the crypt compared to normal mucosa. After DMH, proliferation in normal mucosa was significantly depressed, but it did not vary in MDF. Survivin-Birc5 regulating apoptosis and proliferation was significantly over-expressed (RT-qPCR and immunohistochemistry experiments) in MDF vs. normal mucosa, but did not vary in response to DMH. The expression of the pro-apoptotic protein Bak did not vary in normal mucosa and MDF. Since inflammation is present in MDF, which may hamper apoptosis, we studied the effect of pre-treatment with aspirin (600 ppm in the diet for 10 days). No significant effects of aspirin were observed. In conclusion, MDF had a higher spontaneous apoptosis and proliferation coupled with a reduced response to apoptotic stimuli from cytotoxic compounds. Survivin over-expression in MDF indicates that this is an early event in colon carcinogenesis and suggests that down-regulation of Survivin may represent a strategy for cancer prevention.

Gene expression profile and genomic alterations in colonic tumours induced by 1,2-dimethylhydrazine (DMH) in rats.

BACKGROUND: Azoxymethane (AOM) or 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in rats shares many phenotypical similarities with human sporadic colon cancer and is a reliable model for identifying chemopreventive agents. Genetic mutations relevant to human colon cancer have been described in this model, but comprehensive gene expression and genomic analysis have not been reported so far. Therefore, we applied genome-wide technologies to study variations in gene expression and genomic alterations in DMH-induced colon cancer in F344 rats. METHODS: For gene expression analysis, 9 tumours (TUM) and their paired normal mucosa (NM) were hybridized on 4 x 44K Whole rat arrays (Agilent) and selected genes were validated by semi-quantitative RT-PCR. Functional analysis on microarray data was performed by GenMAPP/MappFinder analysis. Array-comparative genomic hybridization (a-CGH) was performed on 10 paired TUM-NM samples hybridized on Rat genome arrays 2 x 105K (Agilent) and the results were analyzed by CGH Analytics (Agilent). RESULTS: Microarray gene expression analysis showed that Defcr4, Igfbp5, Mmp7, Nos2, S100A8 and S100A9 were among the most up-regulated genes in tumours (Fold Change (FC) compared with NM: 183, 48, 39, 38, 36 and 32, respectively), while Slc26a3, Mptx, Retlna and Muc2 were strongly down-regulated (FC: -500; -376, -167, -79, respectively). Functional analysis showed that pathways controlling cell cycle, protein synthesis, matrix metalloproteinases, TNFalpha/NFkB, and inflammatory responses were up-regulated in tumours, while Krebs cycle, the electron transport chain, and fatty acid beta oxidation were down-regulated. a-CGH analysis showed that four TUM out of ten had one or two chromosomal aberrations. Importantly, one sample showed a deletion on chromosome 18 including Apc. CONCLUSION: The results showed complex gene expression alterations in adenocarcinomas encompassing many altered pathways. While a-CGH analysis showed a low degree of genomic imbalance, it is interesting to note that one of the alterations concerned Apc, a key gene in colorectal carcinogenesis. The fact that many of the molecular alterations described in this study are documented in human colon tumours confirms the relevance of DMH-induced cancers as a powerful tool for the study of colon carcinogenesis and chemoprevention.

Arabinoxylan-oligosaccharides (AXOS) reduce preneoplastic lesions in the colon of rats treated with 1,2-dimethylhydrazine (DMH).

BACKGROUND: Prebiotics are non-digestible compounds that beneficially affect the host by stimulating the growth and/or activity of one or a limited number of resident colonic bacteria in the gut. Reported beneficial effects of prebiotics include reduced gut infections, better absorption of minerals, and notably, antitumorigenic effects. Arabinoxylan (AX)-oligosaccharides (AXOS) have been suggested to exert prebiotic effects in the gut, but their effect on colon carcinogenesis has not been studied so far. AIM OF THE STUDY: To test the effect of AXOS in a rat colon carcinogenesis model. METHODS: We determined the occurrence of two types of preneoplastic lesions [aberrant crypt foci (ACF) and mucin depleted foci (MDF)] in the colon of rats treated with the colon carcinogen 1,2-dimethylhydrazine (DMH) and fed either a control diet or a diet containing AXOS (4.8% w/w) (15 rats in each group). RESULTS: Thirteen weeks after DMH treatment, MDF counts were significantly lower in the entire colon of AXOS fed rats (MDF/colon were 7.5 +/- 0.6 and 5.5 +/- 0.6, in Control and AXOS groups, respectively, means +/- SE, P < 0.05). Although the number of ACF in the entire colon was not significantly different between Control and AXOS fed rats, AXOS fed rats had significantly fewer ACF in the distal part of the colon than Control group rats (ACF/distal colon were 135.5 +/- 15 and 84.4 +/- 11, in Control and AXOS groups, respectively, means +/- SE, P < 0.05). CONCLUSIONS: The present study shows that dietary intake of AXOS by rats reduces the occurrence of two types of preneoplastic lesions, thus suggesting a chemopreventive effect on colon carcinogenesis that should be confirmed in a long-term carcinogenesis experiment.