Preventive effect of fermented brown rice and rice bran on N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric carcinogenesis in rats

A number of possible preventive agents for cancers in different organs have been reported, however, little information is available regarding the effective agents for the development of gastric cancers. The rice components are known to be effective for the prevention of the development of cancers. Our group has demonstrated that fermented brown rice by Aspergillus Orzae (FBRA) has chemopreventive potentials in several organs. In this study, we investigated the modifying effects of FBRA exposed during the initiation or post-initiation phase of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in rats. Five-week-old male ACI rats were divided into 7 groups. Groups 1-5 were given oral administration of MNNG (100 mg/l in distilled water) for 24 weeks starting at 6 weeks of age. Groups 2 and 3 were fed a diet containing 5 and 10% FBRA during the initiation phase, respectively, whereas groups 4 and 5 were fed these diets during the post-initiation phase. Group 6 was given a diet containing 10% FBRA throughout the experiment. Group 7 was kept on the basal diet alone and served as an untreated control. Rats were sacrificed at 52 weeks after the start, and the epithelium of the stomach was investigated in detail. Incidence and multiplicity of gastric proliferative lesions of group 1 (MNNG alone) were 61% and 1.67+/-1.57/rat, respectively. Those of group 5 (25%, 0.35+/-0.67) which were given FBRA at a dose of 10% during the post-initiation phase were significantly less than those of group 1. Furthermore, the same group expressed a significantly decreased Ki67-labeling index in the non-lesional gastric epithelium when compared to that of group 1. These results indicate that FBRA inhibits MNNG-induced development of gastric tumors by administration during the post-initiation phase in rats. FBRA is regarded as a promising dietary agent for the prevention of human gastric cancer.     

Preventive effect of fermented brown rice and rice bran against colon carcinogenesis in male F344 rats

Epidemiological and preclinical studies demonstrate that nutrition plays an important role in the etiology of cancer. It has been reported that rice components, especially rice germ plays a key role in prevention of cancer. The experiments described here examined the potential anticancer properties of brown rice fermented by Aspergillus Oryzae (FBRA) in male F344 rats using inhibition of the formation of azoxymethene (AOM) induced aberrant crypt foci (ACF) and tumors in the colon as the measure of preventive efficacy. The agent was administered at 2.5 and 5% levels in the diet during the initiation phase (during and until 1 week after carcinogen treatment) and/or post-initiation phase (beginning 1 week after carcinogen treatment) of carcinogenesis. In the ACF and tumor studies, rats were sacrificed 5 or 40 weeks after the initiation of AOM treatment (15 mg/kg body weight, once weekly for 3 weeks), respectively. Colonic ACF and tumors were evaluated histopathologically. Administration of 2.5 and 5% FBRA in the diet continuously during initiation and post-initiation period significantly inhibited the ACF formation in rats treated with AOM, compared with rats treated with AOM alone (99+/-24.1 and 79+/-18.4 vs. 139.5+/-27.7, respectively). In addition, administration of 5% FBRA in the diet during the post-initiation phase significantly suppressed the incidence (44 vs.18%) and multiplicity (0.93+/-0.96 vs. 0.18+/-0.40) of colon adenocarcinomas as compared to those given the control diet. In addition, 5% FBRA in the diet during post-initiation phase caused significant inhibition of cell proliferation in the colonic mucosa as compared to the group fed the control diet (81% reduction, p<0.05). These observations demonstrated for the first time that FBRA inhibits colon tumor development in rats, and suggest that it is a promising dietary supplement for prevention of human colon cancer.     

Preventive effect of fermented brown rice and rice bran on diethylnitrosoamine and phenobarbital-induced hepatocarcinogenesis in male F344 rats

Epidemiological and preclinical studies have suggested that nutrition plays an important role in the etiology of cancer. Our group previously demonstrated that rice germ or fermented brown rice has a preventive effect on colorectal carcinogenesis. The experiment described here was examined for the potential anticancer properties of brown rice fermented by Aspergillus Oryzae (FBRA) in male F344 rats using inhibition of diethylnitrosoamine (DEN) and phenobarbital (PB)-induced hepatocarcinogenesis as the measure of preventive efficacy when this agent was administered at 5% and 10% levels in diet during initiation phase (during and until 1 week after carcinogen treatment) or post-initiation phase (beginning 1 week after carcinogen treatment) of the carcinogenesis. Rats were sacrificed 20 weeks after the initiation of DEN treatment (200 mg/kg body weight, once weekly for 3 weeks). Expression of liver tumors was evaluated histopathologically. Administration of 10% FBRA in the diet during the initiation phase significantly decreased the incidence (43% vs. 8%) and multiplicity (0.5+/-0.6 vs. 0.1+/-0.3) of hepatocellular carcinoma (HCC) as compared to those given the control diet. In addition, 5% and 10% of FBRA in the diet during post-initiation phase significantly decreased the incidence of HCC (43% vs. 15% and 9%, respectively) and multiplicity of hepatocellular adenoma (4.7+/-3.7 vs. 2.1+/-2.2 and 2.4+/-1.4, respectively) and HCC (0.5+/-0.6 vs. 0.2+/-0.4 and 0.1+/-0.3, respectively). These data prove that FBRA has an inhibitory effect on the hepatocarcinogenesis in rats. FBRA could be a promising chemopreventive agent for human liver as well as colorectal neoplasia.     

Chemopreventive effect of fermented brown rice and rice bran on 4-nitroquinoline 1-oxide-induced oral carcinogenesis in rats

The preventive effects of the dietary administration of brown rice and rice bran fermented with Aspergillus oryzae (FBRA) on oral carcinogenesis induced by 4-nitroquinoline 1-oxide (4-NQO) were investigated in male F344 rats. At 7 weeks of age, the animals were given 20 ppm 4-NQO in their drinking water for 8 weeks to induce tongue neoplasms. Groups of rats were fed diets containing 5 or 10% FBRA during the initiation or postinitiation phases of the 4-NQO-induced oral carcinogenesis. The other groups consisted of rats fed 10% FBRA or untreated rats. At the termination of the study (week 32), the incidences, multiplicities of tongue lesions (pre-neoplasms and neoplasms) and the cell proliferation activity estimated by the 5-bromodeoxyuridine (BrdU)-labeling index were compared among the groups. Feeding of 5% FBRA during the initiation phase significantly decreased the incidence (68.2 vs 36.8%; p<0.05) and multiplicity (1.05+/-0.84 vs 0.37+/-0.50; p<0.005) of the tongue carcinoma. When feeding of 10% FBRA occurred after the 4-NQO exposure, the multiplicity of tongue carcinoma was also reduced (1.05+/-0.84 vs 0.52+/-0.60; p<0.05). In addition, the dietary administration of FBRA at both doses significantly decreased the BrdU-labeling index in the oral squamous epithelium (p<0.05). Although a dose-dependent response was not observed, FBRA is effective in suppressing the development of 4-NQO-induced oral carcinogenesis by its concurrent exposure to the carcinogen. The inhibitory effect could be related to the suppression of the hyperproliferation of cells in the tongue epithelium and the radical scavenging activity of FBRA.     

Inhibition of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis in rats by green and black tea

In this study, we investigated the effects of green tea andblack tea, when given either during or after carcinogen treatment,on esophageal tumorigenesis in male Sprague—Dawley rats.Rats were treated with N-nitrosomethylbenzylamine (NMBzA) (2.5mg/kg, s.c., twice weekly) for 5 weeks; 39 weeks after the initialdose of NMBzA, 65% of the rats had esophageal tumors with anaverage of 1.4 0.3 tumors per rat. In the groups of rats receiving0.6% of decaffeinated green tea (DGT) or decaffeinated blacktea (DBT) (6 mg tea solids/ml) as the sole source of drinkingfluid during the NMBzA-treatment period, esophageal tumor incidenceand multiplicity were reduced by     

Promotion effects of hot water on N-nitrosomethylbenzylamine-induced esophageal tumorigenesis in F344 rats

This study is to determine the effects of hot water on N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal tumorigenesis model. F344 rats received one treatment of hot water 1 ml/kg and NMBA 1 mg/kg, or a combination treatment of NMBA 1 mg/kg pus hot water 1 ml/kg, or/and EGCG (epigallocatechin-3-gallate) 10 mg/kg. The experiment was concluded at the 20th week. Our results showed that the number of tumors and incidence of carcinomas were significantly increased by hot water (65 degrees C) (p<0.05, p<0.03, respectively), as compared with the group which received NMBA injections only. EGCG treatment did not significantly reduce the number or the size of tumours as the temperature of added hot water increased. In addition, PGE2 production was induced by NMBA, and further significantly increased by added hot water (p<0.05). On the other hand, EGCG slightly decreased the elevated PGE2 production, however, this effect of EGCG was offset by hot water. Our study further confirmed that the drinking of hot beverages increased the risk of esophageal carcinogenesis, and the drinking hot tea will abolish the inhibitory effects of EGCG on this disease.     

Inhibitory effects of fermented brown rice and rice bran on the development of acute hepatitis in Long-Evans Cinnamon rats

To investigate the effects of fermented brown rice (FBRA) on the development of hereditary hepatitis in Long-Evans Cinnamon (LEC) rats, we compared the incidence and grades of acute hepatitis among rats fed 5% and 10% FBRA in the conventional diet and the conventional diet alone. Both the 5% and 10% FBRA-supplemented diets indicated a tendency to prevent the development of hepatitis, and the significant effect of 10% FBRA was observed until 16-17 weeks of age in the accumulated incidence and survival ratio compared with the unsupplemented conventional diet, although no significant difference was observed between 5% and 10% FBRA-supplemented diets. At the age of 12 weeks, which is just before the rats develop hepatitis, serum copper levels in rats fed either of the test diets were similar to those in rats fed the conventional diet. Furthermore, the copper concentration in liver tissue at 12 weeks of age was not changed by the test diet. These results suggest that FBRA has preventive effects on the development of hepatitis in LEC rats and may play an important role in protecting the liver against the free radicals induced by copper accumulation in the liver.     

Inhibitory effects of epigallocatechin-3-gallate on N-nitrosomethylbenzylamine-induced esophageal tumorigenesis in F344 rats

The present study was conducted to assess the inhibitory effects of EGCG (epigallocatechin-3-gallate) on NMBA-induced rat esophageal tumorigenesis and to seek the potential mechanisms. In experiment I, 81 F344 rats were randomly divided into seven experimental groups according to the different regiments of NMBA 1 mg/kg subcutaneously (s.c.) and EGCG 4 mg/kg or 10 mg/kg orally or intraperitoneally (i.p.). The experiment was terminated at 24 weeks. In experiment II, 48 rats were allocated into two groups, each group contained 24 rats, in which the rats were injected with NMBA 1 mg/kg only or a combination of NMBA 1 mg/kg and EGCG 4 mg/kg i.p. Six rats from each group were sacrificed at the 12th, 16th, 20th and 24th week, respectively. The expression of cyclin D1 and cyclooxygenases (COX-2 and COX-1) was detected using semi-quantitative RT-PCR, and the production of prostaglandin E2 (PGE2) was measured by ELISA. In the groups which were treated with EGCG at a dose of 4 mg/kg i.p., or 10 mg/kg both orally and i.p., the mean number of tumors per rat was significantly reduced to 48, 56 and 61%, respectively (p<0.05). The incidence rate of esophageal carcinomas in the rats that were treated with EGCG 4 mg/kg i.p., was significantly lower than that in the rats which only received NMBA 1 mg/kg (p<0.05). The expression of cyclin D1 and COX-2, and the levels of PGE2 were also decreased by EGCG treatment. These results indicated that EGCG significantly inhibits the NMBA-induced rat esophageal carcinogenesis and it inhibitory effects may partly target cyclin D1 and COX-2 expression, and PGE2 production.     

Chemoprevention of mouse urinary bladder carcinogenesis by fermented brown rice and rice bran

Fermented brown rice by Aspergillus oryzae (FBRA) has been shown to be a potent anti-carcinogenic compound. Here, we investigated the modifying effects of dietary feeding with a naturally occurring anti-oxidant FBRA on N-butyl-N-(4-hydroxybutyl)-nitrosamine (OH-BBN)-induced urinary bladder carcinogenesis in male ICR mice. Five-week-old male ICR mice were divided into 7 groups, and groups 1-5 were given OH-BBN (500 ppm) in drinking water for 6 weeks starting at 7 weeks of age. Groups 2 and 3 were fed the diet containing 5% and 10% FBRA during the initiation phase, respectively, whereas groups 4 and 5 were fed these diets during the post-initiation phase. Group 6 was given the diet containing 10% FBRA throughout the experiment, and group 7 was kept on the basal diet alone and served as an untreated control. At the end of the study (week 32), the incidences of simple hyperplasia, dysplasia and carcinoma in the bladders of group 1 (OH-BBN alone) were 92%, 49% and 38%, respectively. Those of group 5 (64%, 23% and 10%) and the incidence of carcinoma of group 4 (17%) was significantly less than that of group 1. Furthermore, the multiplicity of simple hyperplasia and carcinoma of group 5 was significantly less than that of group 1. Post-initiation exposure of 10% FBRA significantly decreased the number/nucleus of silver-stained nucleolar organizer region proteins (AgNORs), an index of cell proliferation, in the non-lesional transitional epithelium when compared to that of the control. Our results indicate that FBRA exerts chemopreventive effects against chemically induced urinary bladder carcinogenesis through anti-proliferative mechanisms. FBRA could be a promising chemopreventive agent for human urinary bladder cancer.     

Chemopreventive effect of curcumin on N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats.

Modifying effects of curcumin (derived from the rhizome of Curcuma longa L.) during the initiation or post-initiation phase of N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis were investigated in male F344 rats. Five-week-old rats were divided into 5 groups, and groups 1, 2 and 3 were given intraperitoneal injections of NMBA (0.5 mg / kg body weight / injection 15 times) for 5 weeks from 7 weeks old to induce esophageal neoplasms. Groups 2 and 3 were fed the diet containing 500 ppm curcumin during the initiation and post-initiation phases, respectively. Group 4 was given the diet containing curcumin throughout the experiment, and group 5 was kept on the basal diet alone and served as an untreated control. Incidence and multiplicity of esophageal neoplasms of group 1 (NMBA alone) were 66.7% and 0.83 +/- 0.70, respectively. Those of groups 2 and 3 were significantly less than those of group 1 (39.3%, 0.46 +/- 0.64, P < 0.05; 33.3%, 0.36 +/- 0.56, P < 0.05, respectively). Furthermore, the incidence and multiplicity of esophageal preneoplastic lesions (moderate or severe epithelial dysplasia) of group 2 (57.1%, 0.61 +/- 0.57; 40%, 0.29 +/- 0.46) or 3 (56.7%, 0.67 +/- 0.66; 23.3%, 0.23 +/- 0.43) were less than those of group 1 (100%, 1.67 +/- 0.70; 70.8%, 0.92 +/- 0.72) (P < 0.05). In this experiment, feeding of curcumin significantly decreased the expression of cell proliferation biomarkers (5-bromo-2'-deoxyuridine labeling index) in the non-lesional esophageal epithelium (P < 0.01). These findings indicate that curcumin inhibits NMBA-induced esophageal carcinogenesis when given during the post initiation as well as initiation phase. This inhibition may be related to suppression of the increased cell proliferation induced by NMBA in the esophageal epithelium.     

Perillyl alcohol as a chemopreventive agent in N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis

Perillyl alcohol (POH) is a monoterpene found in lavender, spearmint, and cherries. Phase I clinical trials with this agent have shown a favorable toxicity profile and preliminary data indicate some chemotherapeutic efficacy in advanced cancers. Animal studies have demonstrated the ability of POH to inhibit tumorigenesis in the mammary gland, liver, and pancreas. Although the precise mechanism of action is unclear, POH has been shown to inhibit the farnesylation of small G-proteins, including Ras, up-regulate the mannose-6-phosphate receptor, and induce apoptosis. Previous studies in our laboratory using the rat model of squamous cell carcinoma of the esophagus have shown that a specific Ha-ras codon 12 mutation is important for tumor promotion and progression. Given the limited toxicity of POH in humans, its proven efficacy in several animal models and its potential to inhibit Ha-ras farnesylation, we conducted an animal study to evaluate the efficacy of POH as a chemopreventive agent for squamous cell carcinoma of the esophagus. Male Fischer-344 rats were treated s.c. with 0.25 mg/kg b.w. of N-nitrosomethylbenzylamine three times a week for 5 weeks. Three days after the final carcinogen dose, they were started either on control diet or diets containing 0.5 or 1.0% POH. At 25 weeks, the animals were sacrificed, and esophageal tumors were counted. Animals fed either dose of POH showed a significant increase in dysplasia when compared with controls (P < 0.05) and a nonsignificant trend toward increased tumor multiplicity. Additionally, 1.0% POH did not affect Ras membrane localization. These data indicate that POH has a weakly promoting effect early in nitrosamine-induced esophageal tumorigenesis and suggest that POH may not be an effective chemopreventive agent for esophageal cancer in humans.     

Suppression of N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis by dietary feeding of auraptene

The modifying effects of auraptene on N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis were investigated in male F344 rats. At 5 weeks of age, all animals, except those with the test chemical alone and control rats, received s.c. injections of NMBA (0.5 mg/kg body weight/injection, three times per week) for 5 weeks. At the end of the study (20 weeks), 75% of the rats treated with NMBA alone had esophageal neoplasms (papillomas). However, the groups who received a dose of 500 ppm auraptene during the initiation phase developed significantly reduced incidence of tumors (39%; P<0.05). Exposure to auraptene (500 ppm) during the post-initiation phase also decreased the frequency of the tumors (29%; P<0.01). The reduction of the incidence of severe dysplasia was obtained when auraptene was administered in the post-initiation phase (P<0.05). Cell proliferation in the esophageal epithelium determined by proliferating cell nuclear antigen (PCNA) was lowered by auraptene (P<0.01). Blood polyamine contents in rats who received NMBA and the test compound were also smaller than those of rats that received the carcinogen (P<0.05). These findings suggest that dietary auraptene is effective in inhibiting the development of esophageal tumors by NMBA when given during the initiation as well as post-initiation phases, and such inhibition is related to suppression of cell proliferation in the esophageal epithelium.     

香加皮三萜类化合物对甲基苄基亚硝胺诱导的食管癌大鼠调节性T细胞功能的影响

目的：探讨香加皮三萜类化合物（triterpenes compound of cortex periplocae,TCCP）对甲基苄基亚硝胺（N_nitrosomethylbenzylamine,NMBA）诱导的食管癌大鼠CD4^＋CD25^＋调节性T细胞功能的影响。方法：健康雄性F344大鼠40只,随机分为模型组（0.5mg/kg NMBA皮下注射）、治疗组（0.5mg/kg NMBA皮下注射及10mg/kg TCCP肌肉注射）、大豆油对照组（肌肉注射大豆油1ml/kg）和正常对照组,每组10只。各组每周给受试物3次,连续5周。分别在给受试物后第9周和第15周抽取4组大鼠外周血各1ml。用流式细胞仪检测大鼠外周血中CD4^＋T细胞和CD4^＋CD25^＋调节性T细胞（Tr细胞）的水平。另留取血清用ELISA法检测大鼠外周血白细胞介素IL-2、IL-10和转化生长因子TGF_β1的含量。结果：与正常对照组相比,NMBA给药后第9周和第15周,模型组外周血中CD4^＋T细胞比例均显著降低（P均〈0.05）,而CD4^＋CD25^＋Tr细胞比例均显著升高（P均〈0.05）。与同时期模型组比较,TCCP治疗组在给药后第9周和第15周外周血中CD4^＋T细胞比例升高,CD4^＋CD25^＋Tr细胞比例降低,差异均具有统计学意义（P均〈0.05）。NMBA给药后第9周和第15周,模型组大鼠外周血中IL-10、TGF-β1水平显著高于正常对照组（P均〈0.05）,经TCCP治疗后显著下降（P均〈0.05）;大鼠外周血中IL-2水平则呈现与之相反的趋势。结论：NMBA诱导大鼠食管癌后外周血中CD4^＋CD25^＋Tr细胞水平增加,TCCP可以通过抑制CD4^＋CD25^＋Tr细胞活化来纠正食管癌发生、发展过程中所致免疫细胞抑制状态,改善NMBA诱导的食管癌大鼠细胞免疫功能紊乱。     

Effect of alkyl chain length on inhibition of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis and DNA methylation by isothiocyanates

This study was undertaken to evaluate the inhibitory effectsof benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC),3-phenylpropyl isothiocyanate (PPITC) or 4- phenylbutyl isothiocyanate(PBITC) on N-nitrosomethylbenzylamine (NMBA)-induced esophagealtumorigenesis in male Fisher 344 rats. Groups of 15 male ratswere fed modified AIN-76A diet or diet containing the four isothiocyanatesat concentrations of 2.5, 1.0 and 0.4 µmol/g diet for25 weeks. After two weeks, rats were administered 0.5 mg/kgNMBA S.C. once weekly for 15 weeks. Additional controls receivedmodified AIN-76A diet only or diet containing the high concentrationof isothiocyanates (2.5 µmol/g) only. No tumors were foundin any of the groups that were not administered NMBA. Rats treatedwith NMBA only developed 6.7±0.8 tumors/animal. Tumorincidences in rats treated with 2.5 and 1.0 µmol PEITC/gdiet, and with all three dietary concentrations of PPITC wereinhibited by 60/100% compared to controls. Tumor multiplicitieswere inhibited by 83–100% by PEITC or PPITC at all dietaryconcentrations tested. PPITC clearly had a stronger inhibitoryeffect on NMBA tumorigenesis than did PEITC. Compared to PEITCand PPITC, BITC and PBITC had little inhibitory effect on tumormultiplicity and no effect on NMBA tumor incidence. In general,the occurrence of preneoplastic lesions (acanthoses, hyperkeratose,leukoplakias and leukokeratoses) was inhibited in a similarmanner as tumor incidence and multiplicity, except that no experimentaldiet resulted in a significant reduction of the incidence ofacanthoses and hyperkeratoses. As with their effects on tumorigenicityand formation of premalignant lesions, the inhibitory effectsof the isothiocyanates on NMBA-induced DNA methylation 24 hafter administration followed the order: PPITC > PEITC >PBITC > BITC.     

Suppression of N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis by dietary feeding of 1'-acetoxychavicol acetate.

The modifying effects of 1'-acetoxychavicol acetate (ACA) on N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis were investigated in male F344 rats. At 5 weeks of age, all test animals, except those given the test chemical alone, and the control rats received s.c. injections of NMBA (0.5 mg/kg body weight/injection, three times per week) for 5 weeks. At the termination of the study (20 weeks), 75% of rats treated with NMBA alone had esophageal neoplasms (papillomas). However, the groups given a dose of 500 ppm ACA during the initiation phase developed a significantly reduced incidence of tumors (29%; P<0.01). Exposure to ACA (500 ppm) during the post-initiation phase also decreased the frequency of the tumors (38%; P<0.05). A reduction of the incidence of preneoplastic lesions (hyperplasia or dysplasia) was obtained when ACA was administered in the initiation phase (P<0.01). Cell proliferation in the esophageal epithelium, determined by assay of proliferating cell nuclear antigen (PCNA), was lowered by ACA (P<0.05). Blood polyamine contents in rats given NMBA and the test compound were also smaller than those of rats given the carcinogen (P<0.05). These findings suggest that dietary ACA is effective in inhibiting the development of esophageal tumors by NMBA when given during the initiation or post-initiation phase, and such inhibition is related to suppression of cell proliferation in the esophageal epithelium.     

Sequential endoscopic findings and histological changes of N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats

We performed a sequential endoscopic examination of esophageal carcinogenesis induced by N-nitrosomethyl-benzylamine (NMBA) in F344 rats. The endoscopic findings were consistent with the histological changes observed in the specimens obtained by a biopsy and/or an autopsy. Seven-week-old male F344 rats received a weekly subcutaneous injection of 0.5 mg/kg NMBA for 15 weeks. The first endoscopic change that was detected was redness of the musosa due to the dilatation of the submucosal blood vessels. Subsequently, the mucosal redness became obscure, and we observed a focal loss of the visible blood vessel network due to hyperkeratosis, followed by the appearance of plaque-like elevated lesions due to acanthosis. Then, smooth and irregular polyps appeared as a result of the development of papilloma without or with dysplastic potential, respectively. Finally, rough elevation appeared as a result of carcinoma in situ and invasive squamous cell carcinoma. The present endoscopic findings correlated closely with the histological changes, indicating that sequential fiberscopic examination may be useful for monitoring esophageal carcinogenesis.     

The effects of L-748706, a selective cyclooxygenase-2 inhibitor, on N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis

Epidemiological studies suggest that the frequent intake of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a decreased risk of developing esophageal squamous cell carcinoma (SCC). This decrease is thought to correlate with the inhibition of cyclooxygenase (COX) activity. The production of prostaglandin E2 (PGE2), a major metabolite of COX, is increased in numerous human cancers including esophageal SCC, therefore, inhibition of COX activity and subsequent suppression of the formation of PGE2 may be chemopreventive in the esophagus. The objective of the present study was to determine whether L-748706 (L-706), a novel selective COX-2 inhibitor, would prevent N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumor progression in the Fischer 344 (F344) rat. In rats pretreated with a low-dose of NMBA (0.25 mg/kg body weight), L-706 at 100 p.p.m. in the diet significantly reduced tumor multiplicity but not tumor incidence. At 150 p.p.m. in the diet, L-706 alone and in combination with 200 p.p.m. piroxicam produced significant reductions in both tumor incidence and multiplicity. Inhibition of tumor development in low-dose NMBA-treated rats was associated with reductions in esophageal cell proliferation rates and PGE2 levels in preneoplastic tissues. In contrast, in rats treated with a higher dose of NMBA (0.5 mg/kg body weight), neither L-706 alone nor in combination with piroxicam reduced esophageal tumor incidence or multiplicity in spite of the fact that they reduced esophageal PGE2 levels in preneoplastic tissues and in papillomas. Cell proliferation rates were reduced only in animals treated with L-706 + piroxicam. Our data suggest that the chemopreventive treatments were effective in inhibiting tumor development in NMBA-treated animals only when they reduced PGE2 levels in preneoplastic esophageal tissues approximately to those levels found in normal esophagus.     

Preventive effects of antioestrogen on mammary and pituitary tumorigenesis in rats

Six groups of inbred male Wistar/Furth (WF) rats were castrated at 40 days of age and group I received no further treatment. Groups 3 and 5 received 5.0 mg diethylstilboestrol (DES) pellets. Groups 4 and 6 were given both DES and 5.0 mg anti-oestrogen (antiE) clomiphene citrate pellets. At 50-55 days of age groups 2, 5, and 6 were exposed daily to drinking water containing 5.0 mg N-nitrosobutylurea (NBU), for 30 days. None of the castrated rats given NBU alone developed mammary or pituitary tumours (MT, PT). When antiE was administered, both MT and PT incidences were reduced in rats given DES alone or in combination with NBU. Furthermore, in antiE-treated rats receiving DES and NBU the mean number of MT per rat was also significantly decreased. Similarly a marked reduction in the mean pituitary weight was observed in antiE-treated groups. These results indicate that antiE treatment was effective in the prevention of both mammary and pituitary tumorigenesis in rats receiving DES alone or receiving a combination of DES and NBU, and its inhibitory effect on mammary tumorigenesis may be mainly due to competitive antagonism for DES-induced pituitary tumorigenesis by antiE.