Protective effects of vanadium against DMH-induced genotoxicity and carcinogenesis in rat colon: Removal of O6-methylguanine DNA adducts, p53 expression, inducible nitric oxide synthase downregulation and apoptotic induction

Doxorubicin-Loaded Tumor-Targeting Peptide-Decorated Polypeptide Nanoparticles for Treating Primary Orthotopic Colon Cancer

Colorectal cancer is the third most common malignant disease worldwide, and chemotherapy has been the standard treatment for colorectal cancer. However, the therapeutic effects of chemotherapy are unsatisfactory for advanced and recurrent colorectal cancers. Thus, increasing the treatment efficacy of chemotherapy in colorectal cancer is a must. In this study, doxorubicin (DOX)-loaded tumor-targeting peptide-decorated mPEG-P(Phe-co-Cys) nanoparticles were developed to treat orthotopic colon cancer in mice. The peptide VATANST (STP) can specifically bind with vimentin highly expressed on the surface of colon cancer cells, thus achieving the tumor-targeting effects. The nanoparticles are core-shell structured, which can protect the loaded DOX while passing through the blood flow and increase the circulation time. The disulfide bonds within the nanoparticles are sensitive to the glutathione-rich microenvironment of tumor tissues. Rupture of disulfide bonds of the nanoparticles leads to the continuous release of DOX, thus resulting in the apoptosis of the tumor cells. The in vivo experiments in mice with orthotopic colon cancer demonstrated that the synthesized DOX-loaded tumor-targeting peptide-decorated polypeptide nanoparticles showed properties of drug delivery systems and exhibited good antitumor properties. The synthesized nanoparticles show appropriate properties as one of the drug delivery systems and exhibit good antitumor properties after encapsulating DOX.

Stability in solution and chemoprotection by octadecavanadates(IV/V) in E. coli cultures

Two mixed-valence octadecavanadates, (NH₄)₂(Me₄N)₅[V^IV₁₂V^V₆O₄₂I]·Me₄NI·5H₂O (V₁₈I) and [{K₆(OH₂)₁₂V^IV₁₁V^V₇O₄₁(PO₄)·4H₂O}_n] (V₁₈P), were synthesized and characterized by single-crystal X-ray diffraction analysis and FTIR, Raman, ⁵¹V NMR, EPR and UV/Vis/NIR spectroscopies. The chemoprotective activity of V₁₈I and V₁₈P towards the alkylating agent diethyl sulfate was assessed in E. coli cultures. The complex V₁₈I was nontoxic in concentrations up to 5.0 mmol L^-1, while V₁₈P presented moderate toxicity in the concentration range 0.10 - 10 mmol L^-1. Conversely, a ca. 35% enhancement in culture growth as compared to cells treated only with diethyl sulfate was observed upon addition of V₁₈I (0.10 to 2.5 mmol L^-1), while the combination of diethyl sulfate with V₁₈P increased the cytotoxicity presented by diethyl sulfate alone. ⁵¹V NMR and EPR speciation studies showed that V₁₈I is stable in solution, while V₁₈P suffers partial breakage to give low nuclearity oxidometalates of vanadium(V) and (IV). According to the results, the chemoprotective effect depends strongly on the direct reactivity of the polyoxidovanadates (POV) towards the alkylating agent. The reaction of diethyl sulfate with V₁₈I apparently produces a new, rearranged POV instead of poorly-reactive breakage products, while V₁₈P shows the formation and subsequent consumption of low-nuclearity species. The correlation of this chemistry with that of other mixed-valence polyoxidovanadates, [H₆V^IV₂V^V₁₂O₃₈PO₄]^5- (V₁₄) and [V^IV₈V^V₇O₃₆Cl]^6- (V₁₅), suggests a relationship between stability in solution and chemoprotective performance.

The associations of multiple metals mixture with accelerated DNA methylation aging

Aging is a leading cause of mortality for the elderly and DNA methylation age is reported to be predictive of biological aging. However, few studies have investigated the associations between multiple metals exposure and accelerated aging in the elderly. We performed a pilot study of 288 elderly participants aged 50-115 years and measured genome-wide DNA methylation and 22 blood metals concentrations. Measures of DNA methylation age were estimated using CpGs from Illumina HumanMethylation EPIC BeadChip. Linear mixed regression and Bayesian kernel machine regression (BKMR) models were used to estimate the individual and overall associations between multiple metals and accelerated methylation aging. Single metal models revealed that each 1-standard deviance (SD) increase in log-transformed vanadium, cobalt, nickel, zinc, arsenic, and barium was associated with a -2.256, -1.318, 1.004, -1.926, 1.910 and -1.356 changes in ΔAge, respectively; meanwhile, for aging rate, the change was -0.019, -0.013, 0.010, -0.018, 0.023, and -0.012, respectively (all P < 0.05). The BKMR models showed reverse U-shaped associations of the overall metals mixture with ΔAge and aging rate. Downward trends of ΔAge and aging rate were observed for increasing quantiles of essential metals mixture, but upward trends were observed for non-essential metals mixture. Further individual analysis of the BKMR revealed that the 95% confidence interval of ΔAge and aging rate associated with vanadium, zinc, and arsenic did not cross 0, when other metals concentrations set at 25th, 50th, and 75th percentile. Our findings suggest reverse U-shaped associations of the overall metals mixture with accelerated methylation aging for the first time, and vanadium, zinc, and arsenic may be major contributors driving the associations.

Therapeutic potential of vanadium complexes with 1,10-phenanthroline ligands, quo vadis? Fate of complexes in cell media and cancer cells

V^IVO-complexes formulated as [V^IVO(OSO₃)(phen)₂] (1) (phen = 1,10-phenanthroline), [V^IVO(OSO₃)(Me₂phen)₂] (2) (Me₂phen = 4,7-dimethyl-1,10-phenanthroline) and [V^IVO(OSO₃)(amphen)₂] (3) (amphen = 5-amino-1,10-phenanthroline) were prepared and stability in cell incubation media evaluated. Their cytotoxicity was determined against the A2780 (ovarian), MCF7 (breast) and PC3 (prostate) human cancer cells at different incubation times. While at 3 and 24 h the cytotoxicity differs for complexes and corresponding free ligands, at 72 h incubation all compounds are equally active presenting low IC₅₀ values. Upon incubation of A2780 cells with 1-3, cellular distribution of vanadium in cytosol, membranes, nucleus and cytoskeleton, indicate that the uptake of V is low, particularly for 1, and that the uptake pattern depends on the ligand. Nuclear microscopic techniques are used for imaging and elemental quantification in whole PC3 cells incubated with 1. Once complexes are added to cell culture media, they decompose, and with time most V^IV oxidizes to V^V-species. Modeling of speciation when [V^IVO(OSO₃)(phen)₂] (1) is added to cell media is presented. At lower concentrations of 1, V^IVO- and phen-containing species are mainly bound to bovine serum albumin, while at higher concentrations [V^IVO(phen)_n]²⁺-complexes become relevant, being predicted that the species taken up and mechanisms of action operating depend on the total concentration of complex. This study emphasizes that for these V^IVO-systems, and probably for many others involving oxidovanadium or other labile metal complexes, it is not possible to identify active species or propose mechanisms of cytotoxic action without evaluating speciation occurring in cell media.

A Short-Lived but Highly Cytotoxic Vanadium(V) Complex as a Potential Drug Lead for Brain Cancer Treatment by Intratumoral Injections

The chemistry and short lifetimes of metal-based anti-cancer drugs can be turned into an advantage for direct injections into tumors, which then allow the use of highly cytotoxic drugs. The release of their less toxic decomposition products into the blood will lead to decreased toxicity and can even have beneficial effects. We present a ternary V^V complex, 1 ([VOL¹ L² ], where L¹ is N-(salicylideneaminato)-N'-(2-hydroxyethyl)ethane-1,2-diamine and L² is 3,5-di-tert-butylcatechol), which enters cells intact to induce high cytotoxicity in a range of human cancer cells, including T98g (glioma multiforme), while its decomposition products in cell culture medium were ≈8-fold less toxic. 1 was 12-fold more toxic than cisplatin in T98g cells and 6-fold more toxic in T98g cells than in a non-cancer human cell line, HFF-1. Its high toxicity in T98g cells was retained in the presence of physiological concentrations of the two main metal-binding serum proteins, albumin and transferrin. These properties favor further development of 1 for brain cancer treatment by intratumoral injections.

Vanadium in Biosphere and Its Role in Biological Processes

Ultra-trace elements or occasionally beneficial elements (OBE) are the new categories of minerals including vanadium (V). The importance of V is attributed due to its multifaceted biological roles, i.e., glucose and lipid metabolism as an insulin-mimetic, antilipemic and a potent stress alleviating agent in diabetes when vanadium is administered at lower doses. It competes with iron for transferrin (binding site for transportation) and with lactoferrin as it is secreted in milk also. The intracellular enzyme protein tyrosine phosphatase, causing the dephosphorylation at beta subunit of the insulin receptor, is inhibited by vanadium, thus facilitating the uptake of glucose inside the cell but only in the presence of insulin. Vanadium could be useful as a potential immune-stimulating agent and also as an antiinflammatory therapeutic metallodrug targeting various diseases. Physiological state and dose of vanadium compounds hold importance in causing toxicity also. Research has been carried out mostly on laboratory animals but evidence for vanadium importance as a therapeutic agent are available in humans and large animals also. This review examines the potential biochemical and molecular role, possible kinetics and distribution, essentiality, immunity, and toxicity-related study of vanadium in a biological system.

Vanadium Compounds as PTP Inhibitors

Phosphotyrosine signaling is regulated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Here we discuss the potential of vanadium derivatives as PTP enzyme inhibitors and metallotherapeutics. We describe how vanadate in the V oxidized state is thought to inhibit PTPs, thus acting as a pan-inhibitor of this enzyme superfamily. We discuss recent developments in the biological and biochemical actions of more complex vanadium derivatives, including decavanadate and in particular the growing number of oxidovanadium compounds with organic ligands. Pre-clinical studies involving these compounds are discussed in the anti-diabetic and anti-cancer contexts. Although in many cases PTP inhibition has been implicated, it is also clear that many such compounds have further biochemical effects in cells. There also remain concerns surrounding off-target toxicities and long-term use of vanadium compounds in vivo in humans, hindering their progress through clinical trials. Despite these current misgivings, interest in these chemicals continues and many believe they could still have therapeutic potential. If so, we argue that this field would benefit from greater focus on improving the delivery and tissue targeting of vanadium compounds in order to minimize off-target toxicities. This may then harness their full therapeutic potential.

In vitro and in vivo antitumor effects of the VO-chrysin complex on a new three-dimensional osteosarcoma spheroids model and a xenograft tumor in mice

Osteosarcoma (OS) is the most common primary tumor of bone, occurring predominantly in the second decade of life. High-dose cytotoxic chemotherapy and surgical resection have improved prognosis, with long-term survival for patients with localized disease. Vanadium is an ultra-trace element that after being absorbed accumulates in bone. Besides, vanadium compounds have been studied during recent years to be considered as representative of a new class of non-platinum antitumor agents. Moreover, flavonoids are a wide family of polyphenolic compounds that display many interesting biological effects. Since coordination of ligands to metals can improve the pharmacological properties, we report herein, for the first time, the in vitro and in vivo effects of an oxidovanadium(IV) complex with the flavonoid chrysin on the new 3D human osteosarcoma and xenograft osteosarcoma mice models. The pharmacological results show that VOchrys inhibited the cell viability affecting the shape and volume of the spheroids and VOchrys suppressed MG-63 tumor growth in the nude mice without inducing toxicity and side effects. As a whole, the results presented herein demonstrate that the antitumor action of the complex was very promissory on human osteosarcoma models, whereby suggesting that VOchrys is a potentially good candidate for future use in alternative antitumor treatments.

Dietary butyrylated high-amylose starch reduces azoxymethane-induced colonic O(6)-methylguanine adducts in rats as measured by immunohistochemistry and high-pressure liquid chromatography

O(6)-methyl guanine (O(6)MeG) adducts are major toxic, promutagenic, and procarcinogenic adducts involved in colorectal carcinogenesis. Resistant starch and its colonic metabolite butyrate are known to protect against oncogenesis in the colon. In this study, we hypothesized that a dietary intervention that specifically delivers butyrate to the large bowel (notably butyrylated high-amylose maize starch [HAMSB]) would reduce colonic levels of O(6)MeG in rats shortly after exposure to the deoxyribonucleic acid (DNA) alkylating agent azoxymethane (AOM) when compared with a low-amylose maize starch (LAMS). A further objective was to validate an immunohistochemistry (IHC) method for quantifying O(6)MeG against a high-performance liquid chromatography method using fluorescence and diode array detection. Rats were fed either LAMS or HAMSB diets for 4 weeks followed by a single injection of AOM or saline and killed 6 hours later. After AOM exposure, both IHC and high-performance liquid chromatography method using fluorescence and diode array detection measured a substantially increased quantity of DNA adducts in the colon (P<.001). Both techniques demonstrated equally that consumption of HAMSB provided a protective effect by reducing colonic adduct load compared with the LAMS diet (P<.05). In addition, IHC allowed visualization of the O(6)MeG distribution, where adduct load was reduced in the lower third of the crypt compartment in HAMSB-fed rats (P=.036). The apoptotic response to AOM was higher in the HAMSB-fed rats (P=.002). In conclusion, the reduction in O(6)MeG levels and enhancement of the apoptotic response to DNA damage in the colonic epithelium through consumption of HAMSB provide mechanistic insights into how HAMSB protects against colorectal tumorigenesis.

Radioprotection of 1,2-dimethylhydrazine-initiated colon cancer in rats using low-dose γ rays by modulating multidrug resistance-1, cytokeratin 20, and β-catenin expression

Ionizing radiation is a widely used therapy for solid tumors. However, high-dose ionizing radiation causes apoptosis, transforms normal cells into tumor cells, and impairs immune functions, leading to the defects in the removal of damaged or tumor cells. In contrast, low-dose radiation has been reported to exert various beneficial effects in cells. This experimental study investigated the effect of γ rays at low dose on the development of colorectal tumor in a 1,2-dimethylhydrazine (DMH)-induced colon cancer. Colorectal tumor model was induced in Wistar rats by subcutaneous injection of DMH (20 mg/kg) once a week for 15 weeks. Starting from zero day of DMH injection, a single low dose of whole-body γ irradiation of 0.5 Gy/week was applied to the rats. A significant reduction in lipid peroxidation, nitric oxide, and elevation in the glutathione content and antioxidant enzyme activity (superoxide dismutase and catalase) were observed after γ irradiation comparing with DMH group. Moreover, γ ray reduced the expressions of multidrug resistance 1 (MDR1), β-catenin, and cytokeratin 20 (CK20) those increased in DMH-treated rats. However, survivin did not change with γ ray treatment. A histopathological examination of the DMH-injected rats revealed ulcerative colitis, dysplasia, anaplasia, and hyperchromasia. An improvement in the histopathological picture was seen in the colon of rats exposed to γ rays. In conclusion, the present results showed that low-dose γ ray significantly inhibited DMH-induced colon carcinogenesis in rats by modulating CK20, MDR1, and β-catenin expression but not survivin expression.

Chemoprotective activity of mixed valence polyoxovanadates against diethylsulphate in E. coli cultures: insights from solution speciation studies

Cell survival after treatment with dimethylsulphate in the presence of polyoxovanadates.

The chemopreventive activity of the histone deacetylase inhibitor tributyrin in colon carcinogenesis involves the induction of apoptosis and reduction of DNA damage

The chemopreventive activity of the histone deacetylase inhibitor (HDACi) tributyrin (TB), a prodrug of butyric acid (BA), was evaluated in a rat model of colon carcinogenesis. The animals were treated with TB (TB group: 200mg/100g of body weight, b.w.) or maltodextrin (MD isocaloric control group: 300 mg/100g b.w.) daily for 9 consecutive weeks. In the 3rd and 4th weeks of treatment, the rats in the TB and MD groups were given DMH (40 mg/kg b.w.) twice a week. After 9 weeks, the animals were euthanized, and the distal colon was examined. Compared with the control group (MD group), TB treatment reduced the total number of aberrant crypt foci (ACF; p<0.05) as well as the ACF with ≥4 crypts (p<0.05), which are considered more aggressive, but not inhibited the formation of DMH-induced O6-methyldeoxyguanosine DNA adducts. The TB group also showed a higher apoptotic index (p<0.05) and reduced DNA damage (p<0.05) compared with MD group. TB acted as a HDACi, as rats treated with the prodrug of BA had higher levels of histone H3K9 acetylation compared with the MD group (p<0.05). TB administration resulted in increased colonic tissue concentrations of BA (p<0.05) compared with the control animals. These results suggest that TB can be considered a promising chemopreventive agent for colon carcinogenesis because it reduced the number of ACF, including those that were more aggressive. Induction of apoptosis and reduction of DNA damage are cellular mechanisms that appear to be involved in the chemopreventive activity of TB.

Effects of curcumin on apoptosis and oxidoinflammatory regulation in a rat model of acetic acid-induced colitis: the roles of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase

The present study evaluated the effects of curcumin on epithelial cell apoptosis, the immunoreactivity of the phospho-c-Jun N-terminal kinase (JNK) and phospho-p38 mitogen-activated protein kinases (MAPKs) in inflamed colon mucosa, and oxidative stress in a rat model of ulcerative colitis induced by acetic acid. Rats were randomly divided into three groups: control, acetic acid, and acetic acid+curcumin. Curcumin (100 mg/kg per day, intragastrically) was administered 10 days before the induction of colitis and was continued for two additional days. Acetic acid-induced colitis caused a significant increase in the macroscopic and microscopic tissue ranking scores as well as an elevation in colonic myeloperoxidase (MPO) activity, malondialdehyde (MDA) levels, and the number of apoptotic epithelial cells in colon tissue compared to controls. In the rat colon, immunoreactivity of phospho-p38 MAPK was increased, whereas the phospho-JNK activity was decreased following the induction of colitis. Curcumin treatment was associated with amelioration of macroscopic and microscopic colitis sores, decreased MPO activity, and decreased MDA levels in acetic acid-induced colitis. Furthermore, oral curcumin supplementation clearly prevented programmed cell death and restored immunreactivity of MAPKs in the colons of colitic rats. The results of this study suggest that oral curcumin treatment decreases colon injury and is associated with decreased inflammatory reactions, lipid peroxidation, apoptotic cell death, and modulating p38- and JNK-MAPK pathways.

Chemopreventive effects of aloin against 1,2-dimethylhydrazine-induced preneoplastic lesions in the colon of Wistar rats

Chemoprevention opens new window in the prevention of all types of cancers including colon cancer. Aloin, an anthracycline in plant pigment, can be utilized as a protective agent in cancer induction. In the present study, we have evaluated the chemopreventive efficacy of aloin against 1,2-dimethylhydrazine (DMH)-induced preneoplastic lesions in the colon of Wistar rats. DMH-induced aberrant crypt foci (ACF) and mucin-depleted foci (MDF) have been used as biomarkers of colon cancer. Efficacy of aloin against the colon toxicity was evaluated in terms of biochemical estimation of antioxidant enzyme activities, lipid peroxidation, ACF, MDF, histopathological changes, and expression levels of molecular markers of inflammation and tumor promotion. Aloin pretreatment ameliorates the damaging effects induced by DMH through a protective mechanism that involved reduction in increased oxidative stress enzymes (p < 0.001), ACF, MDF, cyclooxygenase-2, inducible nitric oxide synthase, interleukin-6, proliferating cell nuclear antigen protein expression, and tumor necrosis factor-α (p < 0.001) release. From the results, it could be concluded that aloin clearly protects against chemically induced colon toxicity and acts reasonably by inducing antioxidant level, anti-inflammatory and antiproliferative markers.

Jeju ground water containing vanadium enhances antioxidant systems in human liver cells

Vanadium compounds have shown promise in the treatment of diabetes and in cancer prevention. The aim of this study is to investigate the effects of Jeju ground water, containing the vanadium compounds S1 (8.0 ± 0.9 μg/l) and S3 (26.0 ± 2.0 μg/l), and of vanadyl sulfate (VOSO(4), 26 μg/l) on antioxidant systems in human Chang liver cells. Cells were incubated for ten passages in media containing deionized distilled water, Jeju ground water (S1, S3), or VOSO(4). S1 and S3 increased the gene and protein expression and the enzymatic activities of antioxidant enzymes, including superoxide dismutase, catalase, glutathione peroxidase, and heme oxygenase. VOSO(4) was likewise found to improve mRNA and protein expression as well as the activities of these enzymes. Taken together, these results suggest that the antioxidant properties of Jeju ground water, containing vanadium compounds, and of vanadyl sulfate were due to stimulatory effects on antioxidant enzyme activities and antioxidant enzyme expression.

Increased glutathione synthesis following Nrf2 activation by vanadyl sulfate in human chang liver cells

Jeju ground water, containing vanadium compounds, was shown to increase glutathione (GSH) levels as determined by a colorimetric assay and confocal microscopy. To investigate whether the effects of Jeju ground water on GSH were specifically mediated by vanadium compounds, human Chang liver cells were incubated for 10 passages in media containing deionized distilled water (DDW), Jeju ground water (S1 and S3), and vanadyl sulfate (VOSO(4)). Vanadyl sulfate scavenged superoxide anion, hydroxyl radical and intracellular reactive oxygen species. Vanadyl sulfate effectively increased cellular GSH level and up-regulated mRNA and protein expression of a catalytic subunit of glutamate cysteine ligase (GCLC), which is involved in GSH synthesis. The induction of GCLC expression by vanadyl sulfate was found to be mediated by transcription factor erythroid transcription factor NF-E2 (Nrf2), which critically regulates GCLC by binding to the antioxidant response elements (AREs). Vanadyl sulfate treatment increased the nuclear translocation of Nrf2 and the accumulation of phosphorylated Nrf2. Extracellular regulated kinase (ERK) contributed to ARE-driven GCLC expression via Nrf2 activation. Vanadyl sulfate induced the expression of the active phospho form of ERK. Taken together, these results suggest that the increase in GSH level by Jeju ground water is, at least in part, due to the effects of vanadyl sulfate via the Nrf2-mediated induction of GCLC.

Morphological and molecular alterations in 1,2 dimethylhydrazine and azoxymethane induced colon carcinogenesis in rats

The dimethyhydrazine (DMH) or azoxymethane (AOM) model is a well-established, well-appreciated, and widely used model of experimental colon carcinogenesis. It has many morphological as well as molecular similarities to human sporadic colorectal cancer (CC), which are summarized and discussed in this paper. In addition, the paper combines present knowledge of morphological and molecular features in the multistep development of CC recognized in the DMH/AOM rat model. This understanding is necessary in order to accurately identify and interpret alterations that occur in the colonic mucosa when evaluating natural or pharmacological compounds in DMH/AOM rat colon carcinogenesis. The DMH/AOM model provides a wide range of options for investigating various initiating and environmental factors, the role of specific dietary and genetic factors, and therapeutic options in CC. The limitations of this model and suggested areas in which more research is required are also discussed.

Vanadium in the detection, prevention and treatment of cancer: the in vivo evidence

Vanadium, a dietary micronutrient, is yet to be established as an essential part of the human diet. Over the past century, several biological effects of vanadium, such as insulin-mimetic action as well as amelioration of hyperlipidemia and hypertension, have been discovered. This transition element is known to influence a battery of enzymatic systems, namely phosphatases, ATPases, peroxidases, ribonucleases, protein kinases and oxidoreductases. Multiple biochemical and molecular actions of vanadium have been implicated in its inhibitory effects on various tumor cells of human origin. Successful in vitro studies over the past few decades have advanced the anticancer research on vanadium into the preclinical stage. Vanadium in several animal cancer models provides protection against all stages of carcinogenesis--initiation, promotion, and progression. This review focuses on the current advances in cancer prevention and treatment as well as early detection by vanadium compounds in preclinical animal models while pointing to possible mechanisms of such diverse beneficial effects. Clinical pharmacokinetic and potential toxicity studies on vanadium are also highlighted in this review. Supporting and challenging evidence as well as future directions of vanadium research exploring the possibility of using this dietary agent for detection, prevention and treatment of human cancers are critically discussed.

Effects of lycopene, synbiotic and their association on early biomarkers of rat colon carcinogenesis

This study evaluated whether a synergy exists for the combined treatment with lycopene and synbiotic on early biomarkers of colon carcinogenesis. Male Wistar rats received a diet containing 300 mg/kg of lycopene and/or synbiotic (Bifidobacterium lactisplus oligofructose/inulin) or their combination 2 weeks before and during carcinogen treatment with 1,2-dimethylhydrazine (DMH). Twenty-four hours after the last DMH application, the colons were processed for immunohistochemical analysis of proliferating cell nuclear antigen (PCNA), p53 protein, hematoxylin-eosin staining for apoptosis analysis and genotoxicity of fecal water by comet assay. Eight weeks after the last DMH application, the colons were analyzed for development of classical aberrant crypt foci (ACF) and mucin-negative ACF. Treatment with lycopene, synbiotic or their combination significantly increased apoptosis, reduced the PCNA and p53 labeling indexes and the development of classical ACF and mucin-negative ACF. Furthermore, a lower genotoxicity of fecal water was also detected in the groups treated with the chemopreventive agents. An additive/synergistic effect of the combined treatment with lycopene/synbiotic was observed only for the fecal water genotoxicity and mucin-negative ACF parameters. These results indicate that an additive/synergistic of the combination of chemopreventive agents on the initiation phase of colon carcinogenesis can be detected using selective early biomarkers.

High dietary intake of sodium selenite does not affect gene mutation frequency in rat colon and liver

Our previous studies have shown that selenium (Se) is protective against dimethylhydrazine (DMH)-induced preneoplastic colon cancer lesions, and protection against DNA damage has been hypothesized to be one mechanism for the anticancer effect of Se. The present study was designed to determine whether dietary selenite affects somatic mutation frequency in vivo. We used the Big Blue transgenic model to evaluate the in vivo mutation frequency of the cII gene in rats fed either a Se-deficient (0 microg Se/g diet) or Se-supplemented diet (0.2 or 2 microg Se/g diet; n = 3 rats/diet in experiment 1 and n = 5 rats/group in experiment 2) and injected with DMH (25 mg/kg body weight, i.p.). There were no significant differences in body weight between the Se-deficient and Se-supplemented (0.2 or 2 microg Se/g diet) rats, but the activities of liver glutathione peroxidase and thioredoxin reductase and concentration of liver Se were significantly lower (p < 0.0001) in Se-deficient rats compared to rats supplemented with Se. We found no effect of dietary Se on liver 8-hydroxy-2'-deoxyguanosine. Gene mutation frequency was significantly lower in liver (p < 0.001) than that of colon regardless of dietary Se. However, there were no differences in gene mutation frequency in DNA from colon mucosa or liver from rats fed the Se-deficient diet compared to those fed the Se-supplemented (0.2 or 2 microg Se/g diet) diet. Although gene mutations have been implicated in the etiology of cancer, our data suggest that decreasing gene mutation is not likely a key mechanism through which dietary selenite exerts its anticancer action against DMH-induced preneoplastic colon cancer lesions in a Big Blue transgenic rat model.