Yumiko Yasui

Pomegranate seed oil rich in conjugated linolenic acid suppresses chemically induced colon carcinogenesis in rats

Pomegranate (Punica granatum L.) seed oil (PGO) contains more than 70% cis(c)9,frans(f)11,c13–18:3 as conjugated linolenic acids (CLN). Our previous short‐term experiment demonstrated that seed oil from bitter melon (Momordica charantia) (BMO), which is rich in c9,t11,t13‐CLN, inhibited the occurrence of colonic aberrant crypt foci (ACF) induced by azoxymethane (AOM). In this study, we investigated the effect of dietary PGO on the development of AOM‐induced colonic malignancies and compared it with that of conjugated linoleic acid (CLA). To induce colonic tumors, 6‐week old male F344 rats were given subcutaneous injections of AOM (20 mg/kg body weight) once a week for 2 weeks. One week before the AOM treatment they were started on diet containing 0.01%, 0.1%, or 1%±PGO or 1% CLA for 32 weeks. Upon termination of the bioassay (32 weeks) colon tumors were evaluated histopathologically. AOM exposure produced colonic adenocarcinoma with an incidence of 81% and multiplicity of 1.88±1.54 at week 32. Administration of PGO in the diet significantly inhibited the incidence (AOM+0.01% PGO, 44%, P<0.05; AOM+0.1% PGO, 38%, P<0.01; AOM+1% PGO, 56%) and the multiplicity (AOM+0.01% PGO, 0.56±0.73, P<0<01; AOM+0.1% PGO, 0.50±0.73, P<0.005; AOM+1% PGO, 0.88±0.96, P<0.05) of colonic adenocarcinomas, although a clear dose‐response relationship was not observed at these dose levels. CLA feeding also slightly, but not significantly, reduced the incidence and multiplicity of colonic adenocarcinomas. The inhibition of colonic tumors by PGO was associated with an increased content of CLA (c9,t11–18:2) in the lipid fraction of colonic mucosa and liver. Also, administration of PGO in the diet elevated expression of peroxisome proliferator activated receptor (PPAR) γ protein in the nontumor mucosa. These results suggest that PGO rich in c9,t11,c13‐CLN can suppress AOM‐induced colon carcinogenesis, and the inhibition is associated in part with the increased content of CLA in the colon and liver and/or increased expression of PPARγ protein in the colon mucosa.

Zerumbone, a tropical ginger sesquiterpene, inhibits colon and lung carcinogenesis in mice

Zerumbone (ZER), present in subtropical ginger Zingiber zerumbet Smith, possesses anti‐growth and anti‐inflammatory properties in several human cancer cell lines. ZER also down‐regulates the cyclooxygenase‐2 and inducible nitric oxide synthase expression via modulation of nuclear factor (NF)‐κB activation in cell culture systems. These findings led us to investigate whether ZER is able to inhibit carcinogenesis in the colon and lung, using 2 different preclinical mouse models. In Exp. 1, a total of 85 male ICR mice were initiated using a single intraperitoneal (i.p.) injection with azoxymethane (AOM, 10 mg/kg bw) and promoted by 1.5% dextran sulfate sodium (DSS) in drinking water for 7 days for rapid induction of colonic neoplasms. Animals were then fed the diet containing 100, 250 or 500 ppm ZER for 17 weeks. In Exp. 2, a total of 50 female A/J mice were given a single i.p. injection of 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (10 μmol/mouse) to induce lung proliferative lesions. They were then fed the diet mixed with 100, 250 or 500 ppm ZER for 21 weeks. At the termination of the experiments (wk 20 of Exp. 1 and wk 22 of Exp. 2), all animals were subjected to complete necropsy examination to determine the pathological lesions in both tissues. Oral administration of ZER at 100, 250 and 500 ppm significantly inhibited the multiplicity of colonic adenocarcinomas. The treatment also suppressed colonic inflammation. In the lung carcinogenesis, ZER feeding at 250 and 500 ppm significantly inhibited the multiplicity of lung adenomas in a dose‐dependent manner. Feeding with ZER resulted in inhibition of proliferation, induction of apoptosis, and suppression of NFκB and heme oxygenase (HO)‐1 expression in tumors developed in both tissues. Our findings suggest that dietary administration of ZER effectively suppresses mouse colon and lung carcinogenesis through multiple modulatory mechanisms of growth, apoptosis, inflammation and expression of NFκB and HO‐1 that are involved in carcinogenesis in the colon and lung.

Dietary astaxanthin inhibits colitis and colitis-associated colon carcinogenesis in mice via modulation of the inflammatory cytokines.

Astaxanthin (AX) is one of the marine carotenoid pigments, which possess powerful biological antioxidant, anti-inflammatory and anti-cancer properties. The purpose of this study is to investigate possible inhibitory effect of AX against inflammation-related mouse colon carcinogenesis and dextran sulfate sodium (DSS)-induced colitis in male ICR mice. We conducted two different experiments. In the first experiment, we evaluated the effects of AX at three dose levels, 50, 100 and 200 ppm in diet, on colitis-associated colon carcinogenesis induced by azoxymethane (AOM)/DSS in mice. In the second, the effects of the AX (100 and 200 ppm) in diet on DSS-induced colitis were determined. We found that dietary AX significantly inhibited the occurrence of colonic mucosal ulcers, dysplastic crypts, and colonic adenocarcinoma at week 20. AX-feeding suppressed expression of inflammatory cytokines, including nuclear factor (NF)-κB, tumor necrosis factor (TNF)-α and interleukin (IL)-1β, inhibited proliferation, and induced apoptosis in the colonic adenocarcinomas. Feeding with 200 ppm AX, but not 100 ppm, significantly inhibited the development of DSS-induced colitis. AX feeding (200 ppm in diet) also lowered the protein expression of NF-κB, and the mRNA expression of inflammatory cytokines, including IL-1β, IL-6, and cyclooxygenase (COX)-2. Our results suggest that the dietary AX suppresses the colitis and colitis-related colon carcinogenesis in mice, partly through inhibition of the expression of inflammatory cytokine and proliferation. Our findings suggest that AX is one of the candidates for prevention of colitis and inflammation-associated colon carcinogenesis in humans.

Dietary seed oil rich in conjugated linolenic acid from bitter melon inhibits azoxymethane-induced rat colon carcinogenesis through elevation of colonic PPARγ expression and alteration of lipid composition

Our previous short‐term experiment demonstrated that seed oil from bitter melon (Momordica charantia) (BMO), which is rich in cis(c)9, trans(t)11, t13‐conjugated linolenic acid (CLN), inhibited the development of azoxymethane (AOM)‐induced colonic aberrant crypt foci (ACF). In our study, the possible inhibitory effect of dietary administration of BMO on the development of colonic neoplasms was investigated using an animal colon carcinogenesis model initiated with a colon carcinogen AOM. Male F344 rats were given subcutaneous injections of AOM (20 mg/kg body weight) once a week for 2 weeks to induce colon neoplasms. They also received diets containing 0.01%, 0.1% or 1% BMO for 32 weeks, starting 1 week before the first dosing of AOM. At the termination of the study (32 weeks), AOM induced 83% incidence (15/18 rats) of colonic adenocarcinoma. Dietary supplementation with 0.01% and 0.1% BMO caused significant reduction in the incidence (47% inhibition by 0.01% BMO, p<0.02; 40% inhibition by 0.1% BMO, p<0.05; and 17% inhibition by 1% BMO) and the multiplicity (64% inhibition by 0.01% BMO, p<0.005; 58% inhibition by 0.1% BMO, p<0.02; and 48% inhibition by 1% BMO, p<0.05) of colonic adenocarcinoma, though a clear dose response was not observed. Such inhibition was associated with the increased content of CLA (c9,t11‐18:2) in the lipid composition in colonic mucosa and liver. Also, BMO administration in diet enhanced expression of peroxisome proliferator‐activated receptor (PPAR) γ protein in the nonlesional colonic mucosa. These findings suggest that BMO rich in CLN can suppress AOM‐induced colon carcinogenesis and the inhibition might be caused, in part, by modification of lipid composition in the colon and liver and/or increased expression of PPARγ protein level in the colon mucosa.

Suppressive effects of nobiletin on hyperleptinemia and colitis-related colon carcinogenesis in male ICR mice

Adipocytokines are a group of adipocyte-secreted proteins that have significant effects on the metabolism of lipids and carbohydrates, as well as numerous other processes. A number of recent studies have indicated that some adipocytokines may significantly influence the proliferation of malignant cells in vitro, whereas it remains unclear whether they have similar roles in vivo. In this study, we determined serum levels of adipocytokines in mice with azoxymethane (AOM)- and dextran sulfate sodium (DSS)-induced colon carcinogenesis. Five-week-old ICR mice were given a single intraperitoneal injection of AOM followed by 1% DSS in drinking water for 7 days. Nobiletin (NOB), a citrus flavonoid, was given in the diet (100 p.p.m) for 17 weeks. Thereafter, the incidence and number of colon tumors and serum concentration of adipocytokines were determined at the end of week 20. The serum leptin level in AOM/DSS-treated mice was six times higher than that in untreated mice, whereas there were no significant differences in the levels of triglycerides, adiponectin and interleukin-6. Feeding with NOB abolished colonic malignancy and notably decreased the serum leptin level by 75%. Further, NOB suppressed the leptin-dependent, but not independent, proliferation of HT-29 colon cancer cells and decreased leptin secretion through inactivation of mitogen-activated protein kinase/extracellular signaling-regulated protein kinase, but not that of adiponectin in differentiated 3T3-L1 mouse adipocytes in a dose-dependent manner. Taken together, our results suggest that higher levels of leptin in serum promote colon carcinogenesis in mice, whereas NOB has chemopreventive effects against colon carcinogenesis, partly through regulation of leptin levels.

Melatonin suppresses AOM/DSS-induced large bowel oncogenesis in rats.

The inhibitory effects of exogenous melatonin (MEL) on colon oncogenesis were investigated using an azoxymethane (AOM)/dextran sodium sulfate (DSS) rat model. Male F344 rats initiated with a single intraperitoneal injection of AOM (20mg/kg bw) were promoted by 1% (w/v) DSS in drinking water for 7 days. They were then given 0.4, 2 or 10ppm MEL in drinking water for 17 weeks. At week 20, the development of colonic adenocarcinoma was significantly inhibited by the administration with MEL dose-dependently. MEL exposure modulated the mitotic and apoptotic indices in the colonic adenocarcinomas that developed and lowered the immunohistochemical expression of nuclear factor kappa B, tumor necrosis factor alpha, interleukin-1beta and STAT3 in the epithelial malignancies. These results may indicate the beneficial effects of MEL on colitis-related colon carcinogenesis and a potential application for inhibiting colorectal cancer development in the inflamed colon.

Global gene expression analysis of the mouse colonic mucosa treated with azoxymethane and dextran sodium sulfate

BackgroundChronic inflammation is well known to be a risk factor for colon cancer. Previously we established a novel mouse model of inflammation-related colon carcinogenesis, which is useful to examine the involvement of inflammation in colon carcinogenesis. To shed light on the alterations in global gene expression in the background of inflammation-related colon cancer and gain further insights into the molecular mechanisms underlying inflammation-related colon carcinogenesis, we conducted a comprehensive DNA microarray analysis using our model.MethodsMale ICR mice were given a single ip injection of azoxymethane (AOM, 10 mg/kg body weight), followed by the addition of 2% (w/v) dextran sodium sulfate (DSS) to their drinking water for 7 days, starting 1 week after the AOM injection. We performed DNA microarray analysis (Affymetrix GeneChip) on non-tumorous mucosa obtained from mice that received AOM/DSS, AOM alone, and DSS alone, and untreated mice at wks 5 and 10.ResultsMarkedly up-regulated genes in the colonic mucosa given AOM/DSS at wk 5 or 10 included Wnt inhibitory factor 1 (Wif1, 48.5-fold increase at wk 5 and 5.7-fold increase at wk 10) and plasminogen activator, tissue (Plat, 48.5-fold increase at wk 5), myelocytomatosis oncogene (Myc, 3.0-fold increase at wk 5), and phospholipase A2, group IIA (platelets, synovial fluid) (Plscr2, 8.0-fold increase at wk 10). The notable down-regulated genes in the colonic mucosa of mice treated with AOM/DSS were the peroxisome proliferator activated receptor binding protein (Pparbp, 0.06-fold decrease at wk 10) and the transforming growth factor, beta 3 (Tgfb3, 0.14-fold decrease at wk 10). The inflammation-related gene, peroxisome proliferator activated receptor γ (Pparγ 0.38-fold decrease at wk 5), was also down-regulated in the colonic mucosa of mice that received AOM/DSS.ConclusionThis is the first report describing global gene expression analysis of an AOM/DSS-induced mouse colon carcinogenesis model, and our findings provide new insights into the mechanisms of inflammation-related colon carcinogenesis and the establishment of novel therapies and preventative strategies against carcinogenesis.

Dietary flavonoids suppress azoxymethane-induced colonic preneoplastic lesions in male C57BL/KsJ-db/db mice

Obesity is known to be a risk factor for colon carcinogenesis. Although there are several reports on the chemopreventive abilities of dietary flavonoids in chemically induced colon carcinogenesis, those have not been addressed in an obesity-associated carcinogenesis model. In the present study, the effects of 3 flavonoids (chrysin, quercetin and nobiletin) on modulation of the occurrence of putative preneoplastic lesions, aberrant crypt foci (ACF), and beta-catenin-accumulated crypts (BCACs) in the development of colon cancer were determined in male db/db mice with obesity and diabetic phenotypes. Male db/db mice were given 3 weekly intraperitoneal injections of azoxymethane (AOM) to induce the ACF and BCAC. Each flavonoid (100ppm), given in the diet throughout the experimental period, significantly reduced the numbers of ACF by 68-91% and BCAC by 64-71%, as well as proliferation activity in the lesions. Clinical chemistry results revealed that the serum levels of leptin and insulin in mice treated with AOM were greater than those in the untreated group. Interestingly, the most pronounced suppression of development of preneoplastic lesions and their proliferation were observed in the quercetin-fed group, in which the serum leptin level was lowered. Furthermore, quercetin-feeding decreased leptin mRNA expression and secretion in differentiated 3T3-L1 mouse adipocytes. These results suggest that the present dietary flavonoids are able to suppress the early phase of colon carcinogenesis in obese mice, partly through inhibition of proliferation activity caused by serum growth factors. Furthermore, they indicate that certain flavonoids may be useful for prevention of colon carcinogenesis in obese humans.

Citrus Compounds Inhibit Inflammation- and Obesity-Related Colon Carcinogenesis in Mice

Dietary polyphenols are important potential chemopreventive natural agents. Other agents, such as citrus compounds, are also candidates for cancer chemopreventives. They act on multiple key elements in signal transduction pathways related to cellular proliferation, differentiation, apoptosis, inflammation, and obesity. This short review article provides our findings of preclinical studies on potential chemopreventive activities of dietary citrus compounds, auraptene, collinin, and citrus unshiu segment membrane (CUSM), using clitis- and obesity-related colon tumorigenesis models. Dietary feeding with auraptene and collinin at dose levels of 0.01% and 0.05% significantly lowered the incidence (50–60% reduction) and multiplicity (67–80% reduction) of colonic adenocarcinomas induced by azoxymetahene [AOM, single intraperitoneal injection of 10 mg/kg body weight (bw)] and dextran sodium sulfate (1% in drinking water). Anti-inflammatory potency of aurapene and collinin may contribute to the effects. Administration with CUSM at 3 doses in diet significantly inhibited development of aberrant crypts foci induced by 5 weekly subcutaneous injections of AOM (15 mg/kg bw) in male db/db mice: 53% inhibition by 0.02% CUSM, 54% inhibition by 0.1% CUSM, and 59% inhibition by 0.5% CUSM. CUSM treatment also decreased serum level of triglycerides. Our findings suggest that certain citrus materials are capable of inhibiting clitis- and obesity-related colon carcinogenesis.

Dietary Tricin Suppresses Inflammation-Related Colon Carcinogenesis in Male Crj: CD-1 Mice

The flavone 4′,5,7-trihydroxy-3′,5′-dimethoxyflavone (tricin) present in rice, oats, barley, and wheat exhibits antigrowth activity in several human cancer cell lines and anti-inflammatory potential. However, the chemopreventive activity has not yet been elucidated in preclinical animal models of colorectal cancer. This study was designed to determine whether dietary tricin exerts inflammation-associated colon carcinogenesis induced by azoxymethane and dextran sulfate sodium in mice. Male Crj: CD-1 mice were initiated with a single i.p. injection of azoxymethane (10 mg/kg body weight) and followed by a 1-week exposure to dextran sulfate sodium (1.5%, w/v) in drinking water to induce colonic neoplasms. They were then given the experimental diet containing 50 or 250 ppm tricin. The experiment was terminated at week 18 to determine the chemopreventive efficacy of tricin. In addition, the effects of dietary tricin on the expression of several inflammatory cytokines, including tumor necrosis factor (TNF)-α, were assayed. The development of colonic adenomas and adenocarcinomas was significantly reduced by feeding with 50 and 250 ppm tricin, respectively. Dietary tricin also significantly reduced the proliferation of adenocarcinoma cells as well as the numbers of mitoses/anaphase bridging in adenocarcinoma cells. The dietary administration with tricin significantly inhibited the expression of TNF-α in the nonlesional cypts. Our findings that dietary tricin inhibits inflammation-related mouse colon carcinogenesis by suppressing the expression of TNF-α in the nonlesional cyrpts and the proliferation of adenocarcinomas suggest a potential use of tricin for clinical trials of colorectal cancer chemoprevention.