Efficacy of geraniol but not of β-ionone or their combination for the chemoprevention of rat colon carcinogenesis

β-ionone (βI), a cyclic isoprenoid, and geraniol (GO), an acyclic monoterpene, represent a promising class of dietary chemopreventive agents against cancer, whose combination could result in synergistic anticarcinogenic effects. The chemopreventive activities of βI and GO were evaluated individually or in combination during colon carcinogenesis induced by dimethylhydrazine in 48 3-week-old male Wistar rats (12 per group) weighing 40-50 g. Animals were treated for 9 consecutive weeks with βI (16 mg/100 g body weight), GO (25 mg/100 g body weight), βI combined with GO or corn oil (control). Number of total aberrant crypt foci (ACF) and of ACF ≥4 crypts in the distal colon was significantly lower in the GO group (66 ± 13 and 9 ± 2, respectively) compared to control (102 ± 9 and 17 ± 3) and without differences in the βI (91 ± 11 and 14 ± 3) and βI+GO groups (96 ± 5 and 19 ± 2). Apoptosis level, identified by classical apoptosis morphological criteria, in the distal colon was significantly higher in the GO group (1.64 ± 0.06 apoptotic cells/mm²) compared to control (0.91 ± 0.07 apoptotic cells/mm²). The GO group presented a 0.7-fold reduction in Bcl-2 protein expression (Western blot) compared to control. Colonic mucosa concentrations of βI and GO (gas chromatography/mass spectrometry) were higher in the βI and GO groups, respectively, compared to the control and βI+GO groups. Therefore, GO, but not βI, represents a potential chemopreventive agent in colon carcinogenesis. Surprisingly, the combination of isoprenoids does not represent an efficient chemopreventive strategy.

Probiotics and cancer: from in vitro to human studies

Studies in cell cultures and animal models provide evidence that probiotics can beneficially influence various stages in development of colon cancer including tumor initiation, promotion and metastasis. For example, oral administration of Lactobacillus and Bifidobacterium strains can prevent genotoxic damage to the colonic epithelium (considered to be an early stage of the carcinogenic process). Administration to rats of probiotics reduced the incidence of carcinogen-induced pre-cancerous lesions (aberrant crypt foci) in the colon. Furthermore a combination of Bifidobacterium longum and inulin (a prebiotic) was more effective than either treatment alone. In this latter study, the dietary treatments were given after exposure to the carcinogen, which suggests that the protective effects were being exerted at the promotional phase of carcinogenesis. L. acidophilus feeding has been shown to decrease the incidence of colon tumors in rats challenged with a carcinogen and B. longum reduced the incidence of carcinogeninduced colon, liver and mammary tumors. There is limited evidence from epidemiological studies for protective effects of products containing probiotics in humans, but a number of recent dietary intervention studies in healthy subjects and in polyp and cancer patients have yielded promising results on the basis of biomarkers of cancer risk and grade of colorectal tumors.

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

Ginger (Zingiber officinale Roscoe) has been proposed as a promising candidate for cancer prevention. Its modifying potential on the process of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) was investigated in male Wistar rats using the aberrant crypt foci (ACF) assay. Five groups were studied: Groups 1-3 were given four s.c. injections of DMH (40 mg/kg b.w.) twice a week, during two weeks, whereas Groups 4 and 5 received similar injections of EDTA solution (DMH vehicle). After DMH-initiation, the animals were fed a ginger extract mixed in the basal diet at 0.5% (Group 2) and 1.0% (Groups 3 and 4) for 10 weeks. All rats were killed after 12 weeks and the colons were analyzed for ACF formation and crypt multiplicity. The rates of cell proliferation and apoptosis were also evaluated in epithelial colonic crypt cells. Dietary consumption of ginger at both dose levels did not induce any toxicity in the rats, but ginger meal at 1% decreased significantly serum cholesterol levels (p < 0.038). Treatment with ginger did not suppress ACF formation or the number of crypts per ACF in the DMH-treated group. Dietary ginger did not significantly change the proliferative or apoptosis indexes of the colonic crypt cells induced by DMH. Thus, the present results did not confirm a chemopreventive activity of ginger on colon carcinogenesis as analyzed by the ACF bioassay and by the growth kinetics of the colonic mucosa. (c) 2005 Elsevier Ltd. All rights reserved.

Efficacy of geraniol but not of β-ionone or their combination for the chemoprevention of rat colon carcinogenesis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Protective effects of yacon (Smallanthus sonchifolius) intake on experimental colon carcinogenesis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lack of protective effects of zinc gluconate against rat colon carcinogenesis

Zinc has been proposed as a promising chemopreventive candidate against colon cancer. However, few studies on the potential beneficial effects of this trace element on cancer chemoprevention are available. The present study was designed to investigate the potential modifying influence of zinc gluconate (ZnGly) on the initiation step of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Male Wistar rats received orally ZnGly (15 mg elemental zinc/kg, 3 times per wk) 2 wk before and during DMH treatment (3 × 40 mg/kg, once a wk). The animals were euthanized at the end of 4th and 16th wk. Colons were analyzed for aberrant crypt foci (ACF) and tumor development. Blood and colon zinc levels, cell proliferation, and apoptosis indexes in colonic crypts were analyzed 24 h after the last DMH administration. Oral treatment with ZnGly did neither alter the number of ACF nor the indexes of cell proliferation and apoptosis in the colonic mucosa. The incidence and multiplicity of colon tumors induced by DMH and their histopathological patterns were not modified by previous treatment with ZnGly. These findings indicate a lack of chemopreventive action of zinc gluconate supplementation on the initiation step of rat colon carcinogenesis induced by DMH. © 2013 Copyright Taylor and Francis Group, LLC.

Efeitos da polpa do fruto de annona crassiflora mart., nos parâmetros bioquímicos e na carcinogênese de colon de ratos

A. crassiflora Mart. a Brazilian savannah fruit, is a source of phytochemical compounds that possess a wide array of biological activities, including free radical scavenging. This native fruit proved to potentialize the mutagenic process in previous in vivo investigations. The aim of the present study was to investigate the effects of A. crassiflora Mart. pulp intake on colonic cell proliferation and on the development of Aberrant Crypt Foci (ACF) in male Wistar rats. The animals were fed with either a commercial diet or a diet supplemented with A. crassiflora Mart. pulp mixed in 1%, 10% or 20% (w/w) for 4 weeks or 20 weeks. The carcinogen 1,2-dimethylhydrazine dihydrochloride (4 doses, 40 mg kg-1 each) was used to induce colonic ACF. After euthanasia, the blood, liver and colon samples were collected for biochemical determinations, oxidative stress or ACF development analysis, respectively. Immunohistochemical analyses of the colonic mucosa were performed using antibodies against proliferating cell nuclear antigen (PCNA) in normal-appearing colonic crypt and β-catenin in ACF. There was no ACF development in the colon from groups treated with A. crassiflora Mart. pulp. Also, the biochemical and oxidative stress analysis, PCNA labeling and ACF development (number, multiplicity or cellular localization of β-catenin) were unchanged as a result of marolo pulp intake. Thus, the present results suggest that A. crassiflora Mart. pulp intake did not exert any protective effect in the colon carcinogenesis induced by DMH in rats.

Efeitos da ingestão de Yacon (Smallanthus sonchifolius) sobre o processo de carcinogênese de cólon induzido pela 1, 2-dimetilhidrazina em ratos wistar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Modulação da carcinogênese do cólon pelo cogumelo Agaricus Blazei no rato

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chemopreventive effects of mate against mouse mammary and colon carcinogenesis

The present study evaluated the chemopreventive potential of mate tea-like intake on mammary and colon carcinogenesis initiated by 7,12-dimethylbenz(a)antracene (DMBA) and 1,2-dimethylhydrazine (DMH) in female Swiss mice. After the initiation period, the animals received basal diet and organic mate tea-like, conventional mate tea-like, or green tea (positive control) at 2.0% as the drinking fluid during 15 weeks. At week 20, colon and mammary gland were analyzed for preneoplastic and neoplastic lesions development. Colon and mammary gland complexes were processed for cell proliferation analysis, estimated by proliferating cell nuclear antigen labeling index (PCNA-LI%). Specially, organic mate tea-like reduced the values of PCNA-LI% in colonic crypts (p < .003) and in mammary glands (p < .05) in DMBA/DMH-initiated groups. A lower incidence of aberrant crypt foci (ACF) in colon (p = .03) and of hyperplastic and neoplastic lesions in mammary gland (p < .05 and p < .02, respectively) was observed in DMBA/DMH-initiated groups treated with organic mate tea-like. These results suggest that post-initiation treatment with organic mate tea-like inhibited the development of colon and mammary carcinogenesis in a two-step medium-term mouse carcinogenesis model.

Chemoprevention of rat hepatocarcinogenesis with histone deacetylase inhibitors: Efficacy of tributyrin, a butyric acid prodrug

Hepatocellular carcinoma (HCC) ranks in prevalence and mortality among top 10 cancers worldwide. Butyric acid (BA), a member of histone deacetylase inhibitors (HDACi) has been proposed as an anticareinogenic agent. However, its short half-life is a therapeutical limitation. This problem could be circumvented with tributyrin (TB), a proposed BA prodrug. To investigate TB effectiveness for chemoprevention, rats were treated with the compound during initial phases of ""resistant hepatocyte"" model of hepatocarcinogenesis, and cellular and molecular parameters were evaluated. TB inhibited (p < 0.05) development of hepatic preneoplastic lesions (PNL) including persistent ones considered HCC progression sites. TB increased (p < 0.05) PNL remodeling, a process whereby they tend to disappear. TB did not inhibit cell proliferation in PNL, but induced (p < 0.05) apoptosis in remodeling ones. Compared to controls, rats treated with TB presented increased (P < 0.05) hepatic levels of BA indicating its effectiveness as a prodrug. Molecular mechanisms of TB-induced hepatocarcinogenesis chemoprevention were investigated. TB increased (p < 0.05) hepatic nuclear histone H3K9 hyperacetylation specifically in PNL and p21 protein expression, which could be associated with inhibitory HDAC effects. Moreover, it reduced (p < 0.05) the frequency of persistent PNL with aberrant cytoplasmic p53 accumulation, an alteration associated with increased malignancy. Original data observed in our study support the effectiveness of TB as a prodrug of BA and as an HDACi in hepatocarcinogenesis chemoprevention. Besides histone acetylation and p21 restored expression, molecular mechanisms involved with TB anticarcinogenic actions could also be related to modulation of p53 pathways. (C) 2008 Wiley-Liss, Inc.

Serrated route to colorectal cancer: back street or super highway?

Morphological and molecular studies are beginning to distinguish separate evolutionary pathways for colorectal cancer, The serrated pathway encompassing hyperplastic aberrant crypt foci, hyperplastic polyps. mixed polyps, and serrated adenoma is increasingly being linked with genetic alterations, including DNA methylation, DNA microsatellite instability, Ii-ras mutation, and loss of chromosome Ip, The importance of the serrated pathway has been underestimated in terms of its frequency and potential for rapid progression, Copyright (C) 2001 John Wiley & Sons, Ltd.

Methylation of O-6-methylguanine DNA methyltransferase characterizes a subset of colorectal cancer with low-level DNA microsatellite instability

The significance of low-level DNA microsatellite instability (MSI-L) is not well understood. K-ras mutation is associated with MSI-L colorectal cancer and with the silencing of the DNA repair gene O-6-methylguanine DNA methyltransferase (MGMT) by methylation of its promoter region. MGMT methylation was studied in sporadic colorectal cancers stratified as DNA microsatellite instability-high (n = 23), MSI-L (n = 44), and microsatellite-stable (n = 23). Methylation-specific PCR was used to detect MGMT-promoter hypermethylation in 3 of 23 (13%) microsatellite instability-high, in 28 of 44 (64%) MSI-L, and in 6 of 23 (26%) microsatellite-stable cancers (P = 0.0001). K-ras was mutated in 20 of 29 (69%) methylated MSI-L cancers and in 2 of 15 (13%) unmethylated MSI-L cancers (P = 0.001), indicating a relationship between MGMT-methylation and mutation of K-ras. Loss of nuclear expression of MGMT was demonstrated immunohistochemically in 23 of 31 (74%) cancers with methylated MGMT and in 10 of 49 (20%) cancers with nonmethylated MGMT (P < 0.0001). Loss of expression of MGMT was also demonstrated in 9 of 31 serrated polyps. Silencing of MGMT may predispose to mutation by overwhelming the DNA mismatch repair system and occurs with greatest frequency in MSI-L colorectal cancers.

Molecular and cellular biology of pre-malignancy in the gastrointestinal tract

Important pathogenic alterations within established cancers are acquired during the premalignant stage. These genetic alterations can be grouped into specific neoplastic pathways that differ within and between anatomical sites. By understanding the mechanisms that determine the initiation and progression of each pathway, it will be possible to develop novel approaches to the diagnosis, prevention and treatment of cancer. This chapter outlines the principles underlying the molecular characterization of pre-malignant lesions, taking colorectal neoplasia as the main model.

Emerging concepts in colorectal neoplasia

An understanding of the mechanisms that explain the initiation and early evolution of colorectal cancer should facilitate the development of new approaches to effective prevention and intervention. This review highlights deficiencies in the current model for colorectal neoplasia in which APC mutation is placed at the point of initiation. Other genes implicated in the regulation of apoptosis and DNA repair may underlie the early development of colorectal cancer. Inactivation of these genes may occur not by mutation or loss but through silencing mediated by methylation of the gene's promoter region. hMLH1 and MGMT are examples of DNA repair genes that are silenced by methylation. Loss of expression of hMLH1 and MGMT protein has been demonstrated immunohistochemically in serrated polyps. Multiple lines of evidence point to a serrated pathway of neoplasia that is driven by inhibition of apoptosis and the subsequent inactivation of DNA repair genes by promoter methylation. The earliest lesions in this pathway are aberrant crypt foci (ACF). These may develop Into hyperplastic polyps or transform while still of microscopic size into admixed polyps, serrated adenomas, or traditional adenomas. Cancers developing from these lesions may show high- or low-level microsatellite instability (MSI-H and MSI-L, respectively) or may be microsatellite stable (MSS). The suggested clinical model for this alternative pathway is the condition hyperplastic polyposis. If colorectal cancer is a heterogeneous disease comprising discrete subsets that evolve through different pathways, it is evident that these subsets will need to be studied individually in the future.