Attenuation by cyclic phosphatidic acid of peritoneal metastasis of azoxymethane-induced intestinal cancers in Wistar rats

The effect of cyclic phosphatidic acid, a unique analogue of lysophosphatidic acid, on the induction of bombesin-enhanced peritoneal metastases from intestinal adenocarcinomas induced by azoxymethane was investigated in male Wistar rats. Rats were given 10 weekly injections of azoxymethane (7.4 mg/kg body weight, s.c.) and of bombesin (40 microg/kg body weight, s.c.) every other day from the start of the experiment, and from week 16, they received injections of cyclic phosphatidic acid (3 or 6 mg/kg body weight, s.c.) every other day until the end of the experiment in week 45. Cyclic phosphatidic acid at both dosages significantly decreased the incidence of bombesin-enhanced cancer metastases to the peritoneum but had little or no effect on the location, histologic type, depth of involvement or infiltrating growth patterns of the tumors. Cyclic phosphatidic acid at either dose decreased significantly the incidence of lymphatic vessel invasion of adenocarcinomas and the activity of RhoA protein in the tumors, both of which were enhanced by bombesin. Our findings indicate that cyclic phosphatidic acid inhibits cancer metastasis through inhibition of RhoA protein activation.     

Genistein attenuates peritoneal metastasis of azoxymethane-induced intestinal adenocarcinomas in Wistar rats

The effects of the soybean isoflavonoid genistein on the development of bombesin-enhanced peritoneal metastasis from intestinal adenocarcinomas induced by azoxymethane (AOM) were investigated in male inbred Wistar rats. From the beginning of the experiment, rats were given 10 weekly s.c. injections of AOM (7.4 mg/kg body weight) and s.c. injections of bombesin (40 microg/kg body weight) every other day, and from week 16, s.c. injections of genistein (5 or 10 mg/kg body weight) every other day until the end of the experiment in week 45. Bombesin significantly increased the incidence of intestinal tumors and of cancer metastasis to the peritoneum. Although genistein administered at either dose had little or no effect on the enhancement of intestinal carcinogenesis by bombesin or on the location, histologic type, depth of involvement, labeling index, or growth pattern of intestinal cancers, it significantly decreased the incidence of cancer metastasis. Genistein also significantly decreased the incidence of lymphatic vessel invasion of adenocarcinomas, which was enhanced by bombesin. Our findings indicate that genistein attenuates cancer metastasis by inhibiting cancer cell invasion into lymphatic vessels through activities that do not affect the growth of intestinal cancers.     

Triamterene Suppresses Bombesin-enhanced Peritoneal Metastasis of Intestinal Adenocarcinomas Induced by Azoxymethane

The effects of combined administration of bombesin and the diuretic triamterene on the incidence of peritoneal metastasis of intestinal cancers induced by azoxymethane (AOM) and the labeling index of intestinal cancers were investigated in male inbred Wistar rats. From the start of the experiment, rats were given weekly s.c. injections of AOM (7.4 mg/kg body weight) for 10 weeks and s.c. injections of bombesin (40 μg/kg body weight) every other day, and from week 16, s.c. injections of triamterene (10 and 20 mg/kg body weight) every other day until the end of the experiment in week 45. Bombesin significantly increased the incidence of intestinal tumors and cancer metastasis to the peritoneum in week 45. It also significantly increased the labeling index of intestinal cancers. Although administration of both doses of triamterene with bombesin had little or no influence on the enhancement of intestinal carcinogenesis by bombesin, or the location, histologic type, depth of invasion, or labeling index of intestinal cancers, it significantly reduced the incidence of cancer metastasis. These findings indicate that triamterene suppresses cancer metastasis through a mechanism that does not affect the proliferation of intestinal cancers.     

Ornithine decarboxylase inhibitor attenuates bombesin enhancement of intestinal carcinogenesis and metastasis induced by azoxymethane

The effects of combined administration of bombesin (40 μ/kg body weight) and the ornithine decarboxylase (ODC) inhibitor, 1,3-diaminopropane (DAP), on the development of large and small intestinal tumors and the incidence of their metastasis to the peritoneum induced by azoxymethane (AOM, 7.4 mg/kg body weight), the ODC activity of the intestinal wall, and the labeling index of the intestinal mucosa and tumor were investigated in inbred Wistar rats. Rats received weekly s.c. injections of AOM for 10 weeks, s.c. injections of bombesin every other day, and drinking water containing DAP (2.5 g/l) until the end of the experiment at week 40. Administration of bombesin significantly increased the incidence of intestinal tumors at week 40. It had no influence on the location, size, histological features or depth of involvement of intestinal adenocarcinomas, but significantly increased the incidence of their metastasis to the peritoneum. It also resulted in a significant increase in the intestinal ODC activity and labeling index. Administration of DAP with bombesin significantly reduced the enhancement of intestinal carcinogenesis by bombesin. Although the combined use of DAP with bombesin had little or no influence on the location, size, histological features, or depth of involvement of intestinal cancers, the incidence of their metastasis was significantly reduced. DAP significantly attenuated bombesin enhancement of the intestinal ODC activity and labeling index. These findings indicate that ODC inhibition attenuated the enhancement of intestinal carcinogenesis and metastasis to the peritoneum.     

Enhancement by bombesin of colon carcinogenesis and metastasis induced by azoxymethane in Wistar rats.

The effects of bombesin on the incidence, number and histology of colon tumors induced by azoxymethane (AOM), and on their metastases to the peritoneum and/or lymph nodes, were investigated in Wistar rats. Rats received weekly s.c. injections of AOM for 10 weeks, and s.c. injections of bombesin in depot form every other day until the end of the experiment in week 30. Administration of bombesin significantly increased the incidence of colon tumors in week 30. It had no influence on the histological features or depths of involvement of colon adenocarcinomas, but significantly increased the incidence of cancer metastasis to the peritoneum and/or lymph nodes. It also caused a significant increase in the labeling index of the colon epithelial cells. Our findings indicate that bombesin enhances the development and metastasis of colon tumors, and that this effect may be related to its effect in increasing proliferation of epithelial cells of the colon.     

Chemoprevention of colon carcinogenesis by concurrent administration of piroxicam, a nonsteroidal antiinflammatory drug with D,L-alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, in diet

The effect of three levels of piroxicam and three levels of D,L-alpha-difluoromethylornithine (DFMO) fed individually and in combination during the postinitiation phase of carcinogenesis was studied in male F344 rats to generate a data base on the efficacy and synergistic and additive effects of these compounds as inhibitors of colon carcinogenesis. The maximum tolerated dose of DFMO was determined in male F344 rats and found to be 5000 ppm in the AIN-76A diet. Piroxicam at levels of 25, 75, and 150 ppm and DFMO at concentrations of 400, 1000, and 4000 ppm (20, 50, and 80% maximum tolerated dose) in AIN-76 diet were tested individually and in combinations. At 7 weeks of age, while the rats were consuming the control diet (AIN-76A), all animals except the vehicle (saline)-treated controls were given a single s.c. injection of azoxymethane (CAS: 25843-45-2) at a dose level of 29.6 mg/kg body weight to induce intestinal tumors. One week after azoxymethane injection, animals were transferred to their respective experimental diets containing piroxicam and DFMO. Fifty-six weeks after azoxymethane injection, all animals were necropsied and colon and small intestinal tumor incidences and multiplicity were compared among the various dietary groups. Feeding of diets containing 75 and 150 ppm piroxicam or 1000 and 4000 ppm DFMO significantly inhibited the incidence (percentage of animals with tumors) of colon adenocarcinomas compared to that of control diet. The multiplicity (number of tumors/rat) of adenocarcinomas was significantly inhibited in animals fed the 25, 75, and 150 ppm piroxicam or 400, 1000, and 4000 ppm DFMO diets. Results analyzed by the linear regression method suggested a dose-dependent inhibition in colon adenocarcinoma incidence with increasing levels of piroxicam or DFMO. The incidence and multiplicity of colon adenocarcinomas were significantly inhibited in animals fed the diets containing combinations of 25, 75, and 150 ppm piroxicam and 400, 1000, and 4000 ppm DFMO. Piroxicam and DFMO administered together had a stronger inhibitory effect than did those given individually. Piroxicam and DFMO when administered individually had no significant inhibitory effect on colon adenoma incidence and multiplicity; in contrast, combinations of these compounds significantly inhibited colon adenomas. No consistent differences were found in the incidence and multiplicity of small intestinal tumors among the dietary groups.(ABSTRACT TRUNCATED AT 400 WORDS)     

Attenuation by the GABA receptor agonist baclofen of experimental carcinogenesis in rat colon by azoxymethane.

The effects of the gamma-amino-n-butyric acid (GABA)A receptor agonist muscimol, and the GABAB receptor agonist baclofen, on colon carcinogenesis induced by azoxymethane in Wistar rats were tested. Administration of either muscimol or baclofen had no influence on the incidence of colon tumors at week 30. However, almost all the colon tumors that developed in rats treated with baclofen were adenomas, whereas in the control group the tumors were mainly adenocarcinomas. In contrast, administration of muscimol did not affect the histological types of the colon tumors. These findings indicate that baclofen inhibits the growth of colon tumors via the GABAB receptor.     

Chemoprevention by galanin against colon carcinogenesis induced by azoxymethane in wistar rats

The effects of the neuropeptide galanin on the development of colon tumors induced by azoxymethane (AOM) and on the labeling index of colon epithelial cells were investigated in Wistar rats. Treatment with galanin significantly decreased the incidence of colon tumors at week 45. Galanin did not influence the histological appearance of the colon tumors, but it slightly increased the frequency of sub-mucosal adenocarcinomas. Furthermore, it significantly decreased the labeling index of colon mucosa during and after AOM treatment. These findings indicate that galanin inhibited the development of colon tumors and that this effect may be related to its suppression of colon-epithelial-cell proliferation. © 1995 Wiley-Liss, Inc.     

K-ras point mutation is associated with enhancement by deoxycholic acid of colon carcinogenesis induced by azoxymethane, but not with its attenuation by all-trans-retinoic acid

The effects of deoxycholic acid (DCA) with and without all-trans-retinoic acid (ATRA) on the incidence of colon tumors induced by azoxymethane, the incidence of K-ras point mutation in colon tumors and the labeling index of colon mucosa were investigated in male Wistar rats. Rats received 5 weekly injections of 7.4 mg/kg body weight of azoxymethane. From the start of the experiment, all rats in 3 groups also received chow pellets containing 0.3% DCA with and without s.c. injections of 0.75 or 1.5 mg/kg body weight of ATRA every other day until the end of week 45. Oral administration of DCA significantly increased the incidence of colon tumors in week 45. Concomitant use of DCA and ATRA at either dose significantly attenuated the enhancement by DCA of colon tumorigenesis. Administration of DCA significantly increased the incidence of K-ras point mutation in colon tumors and the labeling index in the colon mucosa. Combined administration of DCA and ATRA significantly reduced the labeling index of colon mucosa, which was increased by DCA, but did not affect the incidence of K-ras point mutation in colon tumors. These findings suggest that DCA enhances development of colon tumors and that this enhancement is attenuated by ATRA. A possible mechanism of this enhancement is induction of K-ras point mutation. However, decreased cell proliferation in the colon mucosa may be closely related to the attenuation of DCA-enhanced colon tumorigenesis, but not suppression of K-ras point mutation.     

Enhancement by thyroxine of experimental carcinogenesis induced in rat colon by azoxymethane.

The effect of thyroxine (T4) on the incidence, number and histology of colon tumors induced by azoxymethane (AOM), and on the labeling index of colon mucosa were investigated in Wistar rats. Rats were given AOM by injection once a week for 10 weeks, together with T4 in depot form until the end of the experiment. Administration of T4 resulted in a significant increase in the incidence of colon tumors in week 35. However, it did not influence the histological appearance of the colon tumors or the histological types and depths of involvement of colon adenocarcinomas. Furthermore, it caused a significant increase in the labeling index of the colon during, but not after, AOM treatment. Our findings indicate that T4 enhances the development of colon tumors, which may be related to its effect in increasing proliferation of epithelial cells in the colon mucosa during administration of the carcinogen.     

Colon carcinogenesis in germ-free rats with intrarectal 1,2-dimethylhydrazine and subcutaneous azoxymethane.

The effect of intestinal microflora on colon carcinogenesis by 1,2-dimethylhydrazine and azoxymethane was studied, with the use of germ-free and conventional female Fischer rats. At 7 weeks of age, germ-free and conventional rats were treated with 20 weekly intrarectal 1,2-dimethylhydrazine (20 mg per kg body weight per week) or subcutaneous azoxymethane (10 mg per kg body weight per week) doses and were autopsied 15 weeks later. Tumors were induced in the small intestine and colon of germ-free and conventional rats treated with intrarectal 1,2-dimethylhydrazine; the number of rats with colon tumors and the multiplicity of tumors were decreased in germ-free rats, compared with conventional animals. Azoxymethane given subcutaneously increased the incidence and multiplicity of colon tumors in germ-free rats, compared with conventional controls. It is concluded that the intestinal microflora alter the carcinogenic and/or cocarcinogenic effect of different compounds in the large intestine.     

Chemoprevention of colon carcinogenesis by dietary organoselenium, benzylselenocyanate, in F344 rats

The effect of feeding benzylselenocyanate (BSC) and its sulfur analogue, benzylthiocyanate (BTC), 2 wk before, during, and until 1 wk after carcinogen administration (initiation phase) on intestinal carcinogenesis induced by azoxymethane (CAS:25843-45-2) was studied in male F344 rats. Weanling rats were raised on a semipurified diet (AIN-76A diet; control diet). Beginning at 5 wk of age, groups of animals consuming the control diet were fed one of the diets containing 25 ppm BSC or BTC. An additional group was continued on the control diet. At 7 wk of age, all animals in 3 groups, except the vehicle-treated controls, were administered s.c. injections of azoxymethane (15 mg/kg body weight, once weekly for 2 wk). Animals were continued on the control diet and BSC and BTC diets until 1 wk after carcinogen treatment, when those groups receiving BSC and BTC diets were fed the control diet until termination of the experiment. Tissue and blood plasma glutathione peroxidase activity was measured in vehicle-treated animals fed the control diet and BSC and BTC diets for 5 wk. The results indicate that body weights were comparable among the various dietary groups. BSC in the diet significantly inhibited the incidence (percentage of animals with tumors) and multiplicity (tumors/animal) of adenocarcinomas in the colon and multiplicity of adenocarcinomas in the small intestine compared to those fed the control diet. BTC in the diet had no effect on colon and small intestinal tumors. Selenium-dependent glutathione peroxidase activity was significantly increased in kidneys and colon and small intestinal mucosae of animals fed the BSC diet compared to animals fed the BTC and control diets.     

Enhancement of azoxymethane-induced colon carcinogenesis in spontaneously hypertensive rats

The incidence, number, location, and histological types of colon tumors induced by azoxymethane (AOM) and the tissue norepinephrine concentration of the colon wall were investigated in spontaneously hypertensive (SH) rats and in control normotensive Wistar Kyoto (WKY) rats. All rats received 10 weekly s.c. injections of AOM. At week 30, the incidence of colon tumors were significantly higher in SH than in WKY rats. Colon tumors were chiefly located in the proximal colon in WKY but were found with significant frequency in the distal colon in SH rats. The colon tumors induced were mainly adenocarcinomas, but no significant difference in histological type of adenocarcinoma was found between the 2 strains of rat. At weeks 8 and 30, the norepinephrine concentration and labelling index of the distal colon, but not of the proximal colon, were significantly higher in SH than in WKY rats. These findings indicate that increased sympathetic nervous system activity enhances the development of colon tumors.     

Inhibition by dietary oltipraz of experimental intestinal carcinogenesis induced by azoxymethane in male F344 rats

Epidemiological studies suggest that consumption of cruciferous vegetables rich in dithiolethiones is associated with a reduction in the incidence of cancer in man. The effect of two dose levels of dietary oltipraz [5-(2-pyrazinyl)-4-methyl-1, 2- dithiole-3-thione], a substituted dithiolethione, on azoxymethane (AOM)-induced intestinal carcinogenesis and on serum levels was studied in male F344 rats. The maximum tolerated dose (MTD) of oltipraz was determined in male F344 rats and found to be 500 p.p.m. Oltipraz at levels of 200 p.p.m. (40% MTD) and 400 p.p.m. (80% MTD) diet was tested as inhibitor of intestinal carcinogenesis. At 5 weeks of age, animals were fed the modified AIN-76A (control) diet and experimental diets containing oltipraz. At 7 weeks of age, all animals except the vehicle-treated animals were administered s.c. injection of AOM (15 mg/kg body wt/week for 2 weeks). Animals intended for vehicle treatment were administered s.c. with an equal volume of normal saline. Fifty-two weeks later, all animals were killed and colon and small intestinal tumor incidences and multiplicity were compared among the dietary groups. The results indicate that feeding of 200 and 400 p.p.m. of oltipraz significantly inhibited the incidence of adenocarcinomas in colon and small intestine and multiplicity of colon adenomas and small intestinal adenocarcinomas. Animals fed 400 p.p.m. oltipraz showed increased levels of oltipraz in the serum as compared to those fed 200 p.p.m. oltipraz. The results of this study indicate that dietary oltipraz inhibits intestinal carcinogenesis.     

Effects of dietary saturated and unsaturated fatty acids on fecal bile acids and colon carcinogenesis induced by azoxymethane in rats

To determine whether the kind of dietary fat affects colon carcinogenesis, male Donryu rats were fed a 5% fat diet containing linoleate, an unsaturated fat, or stearate, a saturated fat, in semipurified fat-free chow. The rats were given azoxymethane (7.4 mg/kg body weight) s.c. once a week for 11 weeks and killed 15 weeks after the last injection of the carcinogen. The rats on the unsaturated fat diet had a significantly higher incidence of colon tumors. Fatty acid analysis of cholesterol esters in the liver and examination of the amount of fecal bile acids showed that the unsaturated fat diet increased the level of cholesterol linoleate and arachidonate in the liver and also increased the fecal excretion of bile acids, especially that of lithocholic acid. The colon tumors in rats on the unsaturated fat diet, compared with those in rats on the saturated fat diet, contained a higher level of lysophosphatidylcholine. These results suggest that increased fecal excretion of bile acids due to increased polyunsaturated cholesterol esters in the liver stimulates phospholipase A2 activity of colon initiated cells and enhances colon carcinogenesis in rats on the unsaturated fat diet.     

Inhibition by the dopamine antagonist haloperidol of experimental carcinogenesis induced by azoxymethane in rat colon.

The effects of the dopamine agonist bromocriptine and antagonist haloperidol on the incidence and histology of colon tumors induced by azoxymethane and on the labeling index of colon mucosa were investigated in Wistar rats. Rats received weekly s.c. injections of 7.4 mg/kg of body weight azoxymethane for 10 weeks and s.c. injections of 2 mg/kg of body weight bromocriptine or 2 mg/kg of body weight haloperidol, in depot form, every other day until the end of the experiment in week 30. Administration of haloperidol resulted in a significant decrease in the incidence of colon tumors. It also caused a significant decrease in the incidence of adenocarcinomas, with 75% of the tumors being adenomas, and in the labeling index of the colon epithelial cells. In contrast, bromocriptine had no influence on the incidence or histology of colon tumors or the labeling index of the colon mucosa. These findings indicate that the dopamine antagonist haloperidol inhibits colon carcinogenesis and that this effect may be related to its effect in decreasing the proliferation of colon epithelial cells.     

Enhancement by the tricyclic antidepressant, desipramine, of experimental carcinogenesis in rat colon induced by azoxymethane

The effects of the tricyclic antidepressant drug desipramineon the incidence, number and histology of colon tumors inducedby azoxymethane (AOM), and on the serum norepinephrine (NE)concentration and the labeling index of colon mucosa were investigatedin Wistar rats. Rats were treated s.c. with 7.4 mg AOM/kg bodywt once a week for 10 weeks, and also s.c. with 10 mg desipraminehydrochloride (desipramine)/kg body weight until the end ofthe experiment. Treatment with desipramine significantly increasedthe incidence, but not the number, of colon tumors in week 35.However, it did not influence the location and the histologicalappearance of the colon tumors or the histological types ofcolon adenocarcinomas. Furthermore, it significantly increasedthe serum NE level and the labeling index of colon mucosa duringand after AOM treatment. These findings indicate that desipramineenhanced the development of colon tumors and that its effectmay be related to its effect in increasing proliferation ofcolon epithelial cells.     

Induction by bombesin of peritoneal metastasis of gastric cancers induced by N-methyl-N′-nitro-N-nitrosoguanidine in Wistar rats

Background. We investigated the effect of the gastrointestinal regulatory peptide, bombesin, on the development of peritoneal metastasis from gastric cancers induced in rats by N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), and on Rho activity in the gastric cancers. Methods. Rats were allocated to three groups. All groups received MNNG (100 μg/ml) solution for 25 weeks from the start of the experiment. Group 1 (controls) received olive oil injections from the start of MNNG treatment; group 2 animals received alternate-day s.c. injections of bombesin (40 μg/kg body weight) in olive oil from the start of the experiment until the end of the experiment at week 52; and group 3 received the s.c. bombesin injection on alternate days from week 26 until week 52. The effect of bombesin on Rho activity in gastric cancer was examined by Western blotting. Results. Bombesin given from the start of the experiment (group 2) and after the MNNG treatment (group 3) both significantly increased the incidence of gastric cancer metastasis, compared with controls, at week 52: The incidence of metastasis was significantly higher in group 2 than in group 3. Bombesin from the start of the experiment (group 2) significantly increased the incidence of tumors with deeper invasion or more infiltrative growth pattern, or lymphatic vessel tumor invasion, while bombesin after MNNG treatment (group 3) significantly increased the incidence of lymphatic vessel invasion. Bombesin also increased the activity of Rho protein in the tumors. Conclusion. Bombesin significantly increased the incidence of peritoneal metastasis from gastric cancers through the activation of Rho protein. Received: October 19, 2000 / Accepted: January 9, 2001     

Effect of dietary corn bran and autohydrolyzed lignin on 3,2'-dimethyl-4-aminobiphenyl-induced intestinal carcinogenesis in male F344 rats

The effect of dietary corn bran and autohydrolyzed lignin on 3,2'-dimethyl-4-aminobiphenyl (DMAB)-induced intestinal carcinogenesis was studied in male inbred F344 rats. Groups of weanling rats were fed semipurified diets containing 15% corn bran or 7.5% lignin or a semipurified diet without these fibers (control diet). At 7 weeks of age, all animals, except vehicle-treated controls, were given sc injections of 50 mg DMAB/kg body weight/week for 20 weeks. All animals were autopsied 20 weeks after the last injection of DMAB. The incidence of colon tumors (percentage of animals with tumors) and colon tumor multiplicity (tumors/animal) were increased in rats fed the corn bran diet as compared to the tumor incidence and multiplicity in rats fed the control diet. The incidence of small intestinal tumors was slightly lower in rats fed the corn bran diet as compared to the incidence in rats fed the control diet. The concentrations (mg/g dry feces) of fecal deoxycholic acid and total bile acids and the daily output of fecal deoxycholic acid, lithocholic acid, hyodeoxycholic acid, and total bile acids were increased in rats fed the corn bran diet as compared to the concentrations and daily output in rats fed the control diet. The incidence and multiplicity of small intestinal tumors as well as the number of colon adenocarcinomas per tumor-bearing animal were lower in animals fed the lignin diet than in those fed the control diet. Lignin had no effect on the concentrations of fecal bile acids, but the daily output of total bile acids was increased in animals fed the lignin diet as compared to the daily output in rats fed the control diet. This study thus indicates that the protection against colon cancer depends on the type of fiber.     

Prevention of azoxymethane-induced intestinal tumors by a crude ethyl acetate-extract and tryptanthrin extracted from Polygonum tinctorium Lour

The effect of a crude ethyl acetate (AcOEt)-extract and tryptanthrin extracted from the Indigo plant (Polygonum tinctorium Lour.) on azoxymethane (AOM)-induced intestinal tumors was examined in F344 rats. The rats were given subcutaneous (s.c.) injections of either AOM (15 mg/kg body weight (b.w.)) once a week for 3 weeks to induce atypical crypt foci (ACF) as a known cancer precursor, or AOM (7.5 mg/kg b.w.) once a week for 10 weeks to induce intestinal tumors. The rats were also administered the AcOEt-extract (500 mg/kg b.w.) or tryptanthrin (50 mg/kg b.w.) orally, 5 days a week, for 7 or 30 weeks, starting two days before the first administration of AOM. All rats were killed 4 or 20 weeks after the last treatment. In the short-term experiment, the incidence of ACE and atypical crypts (AC) in the groups receiving the AcOEt-extract and tryptanthrin was significantly lower than in the control group. In the tumor-inducing experiment, intestinal tumor incidence in the tryptanthrin group was lower than in the AOM-control group (5% versus 26%), and small intestine tumor incidence in the AcOEt-extract and tryptanthrin groups were lower than in the AOM-control group (0% and 0% versus 23%). These results show that the AcOEt-extract of Indigo and tryptanthrin have cancer chemopreventive activity.