Rapid induction of carcinomas and gamma-glutamyl transpeptidase-rich clones in N-methyl-N-benzylnitrosamine-treated hamster buccal pouch

Topical application of N-methyl-N-benzylnitrosamine [(MBN) CAS: 937-40-6] to Syrian hamster buccal pouch epithelia resulted within 4 days in the induction of epithelial cell foci with histochemical gamma-glutamyl transpeptidase (GGTase) activity. Approximately 94% of the foci consisted of individual cells or nests of 8 cells or less, as visualized in wholemounts of GGTase-stained pouch epithelia. During a regimen of twice weekly MBN applications, the GGTase-stained foci increased in size to a maximum diameter of approximately 0.4 mm by the third week. In histologic sections, the enlarging foci were similar morphologically to those of the adjacent GGTase-negative epithelium. Groups of animals treated with MBN for 2, 4, and 8 weeks developed a buccal pouch tumor incidence of 43, 86, and 100%, respectively, within 39 weeks or less. Of the 138 papillomas and carcinomas examined, 11 contained patchy GGTase activity.     

Anti-Tumour and Anti-Oxidative Potential of Diosgenin against 7, 12-Dimethylbenz(a)anthracene Induced Experimental Oral Carcinogenesis

The ultimate aim of the present study was to exploring the chemopreventive efficacy of diosgenin on 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch carcinogenesis. The chemopreventive potential of diosgenin was evaluated by measuring the tumour incidence, tumour volume and tumour burden as well as analyzing the activities of detoxification agents, levels of lipid peroxidation byproducts and antioxidants status by specific colorimetric methods. Oral squamous cell carcinoma (OSCC) was developed in the buccal pouches of male Syrian golden hamsters by painting with 0.5% DMBA in liquid paraffin, thrice a week for 16 weeks. DMBA painted animals were indicating the morphological changes as depicted as hyperplasia, dysplasia and well-developed squamous cell carcinoma. Moreover, antioxidants and lipid peroxidation byproducts levels were drastically altered in DMBA painted hamsters. Oral administration of diosgenin (80 mg/kg bw) to DMBA painted hamsters on alternate days for 16 weeks significantly reduced the formation of oral tumour and normalized the above biochemical abnormalities. We conclude that the diosgenin is probably potent chemopreventive agent due to their antioxidant function in DMBA induced hamster buccal pouch carcinogenesis.     

Tumor Preventive Efficacy of Emodin in 7,12-Dimethylbenz[a]Anthracene-Induced Oral Carcinogenesis: a Histopathological and Biochemical Approach

The aim of the present study is to focus the chemopreventive potential of Emodin during 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinogenesis. Tumors were developed in the buccal pouches of golden Syrian hamsters by painting with 0.5% DMBA thrice a week for 14 weeks. The status of lipid peroxidation, antioxidants and detoxification agents were utilized as biochemical endpoints and the expression pattern of apoptotic proteins was employed as molecular endpoints in addition to the histopathological studies, to substantiate the anticancer potential of Emodin. Hamsters treated with DMBA + Emodin revealed mild to moderate precancerous lesions such as hyperplasia and dysplasia whereas 100% tumor formation was noticed in hamsters treated with DMBA alone. Also, Emodin treatment modulated the status of lipid peroxidation, antioxidants, phase I and II detoxification agents and apoptotic proteins in favor of the inhibition/reversal/suppression of the oral tumorigenesis in DMBA treated hamsters. The present study thus concludes that the chemopreventive potential of Emodin relies on its pro-apoptotic and antioxidant efficacy during DMBA induced hamster buccal pouch carcinogenesis.     

Anti-tumor Initiating Potential of Andrographolide in 7,12-dimethylbenz[a]anthracene Induced Hamster Buccal Pouch Carcinogenesis

The aim of the study was to investigate the chemopreventive potential of andrographolide in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Oral tumors developed in the buccal pouch ofgolden Syrian hamsters at a 100% incidence on painting with 0.5% DMBA in liquid paraffin three times a weekfor 14 weeks. Marked abnormalities in the status of detoxification enzymes, lipid perxodiation and antioxidantswere noticed in hamsters treated with DMBA alone. Oral administration of andrographolide at a dose of 50 mg/kg bw to hamsters treated with DMBA not only completely prevented the tumor formation but also restored thestatus of the above mentioned biomarkers. The present study thus demonstrates the chemopreventive potentialof andrographolide in DMBA-induced hamster buccal pouch carcinogenesis, which is probably due to itsantioxidant potential as well as modulating effect on xenobiotic metabolising enzymes during DMBA-inducedoral carcinogenesis.     

Inhibition of 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis by S-allylcysteine

Consumption of garlic has been reported to be associated with decreased risk of cancer. We used the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinoma model to assess the oral chemopreventive potential of S-allylcysteine (SAC), a water-soluble constituent of garlic. Hamsters were divided into four groups of six animals each. The right buccal pouches of the animals in group I were painted with a 0.5% solution of DMBA in liquid paraffin three times a week. The animals in group II were painted with DMBA as in group I and in addition received 200 mg/kg body weight SAC intragastrically three times a week on days alternate to DMBA application. Group III animals received SAC as in group II. Animals in group IV received neither DMBA nor SAC and served as control. The hamsters were killed after an experimental period of 14 weeks. Biochemical measurements were carried out on tumour and normal pouch tissues. Measurement of lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione S-transferase (GST) was used to monitor the chemopreventive potential of SAC. All hamsters painted with DMBA alone for 14 weeks developed well-differentiated squamous cell carcinomas. Diminished lipid peroxidation in the oral tumour tissue was accompanied by a significant increase in the levels of GSH, GPx and GST. Administration of SAC significantly suppressed DMBA-induced oral carcinogenesis as revealed by the absence of neoplasms. The results of the present study suggest that garlic may exert its chemopreventive effects by modulating lipid peroxidation and enhancing the levels of GSH, GPx and GST.     

Anticarcinogenic action of diallyl sulfide in hamster buccal pouch and forestomach.

The anticarcinogenic action of the garlic constituent diallyl sulfide (DAS), was examined in the hamster buccal pouch and forestomach. Groups of hamsters were topically treated, for up to 14 weeks, with a 0.5% solution of the buccal pouch and forestomach carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Prior to, during and after DMBA treatment, groups of hamsters were also treated, on alternate days, with a 1% solution of DAS. In addition to tumor formation, the induction of gamma-glutamyl transpeptidase (gamma GT) buccal pouch epithelial lesions served as an additional presumptive index of in vivo carcinogenesis/anticarcinogenesis. DAS resulted in a significant reduction in buccal pouch tumor frequency, buccal pouch tumor burden, buccal pouch gamma GT lesion frequency and forestomach tumor frequency. In a separate experiment, DAS also reduced the level of autoradiographically quantified unscheduled DNA repair synthesis (UDS) in pieces of hamster buccal pouch concurrently exposed in vitro to the potent buccal pouch carcinogen N-methyl-N-benzylnitrosamine (MBN). This study demonstrates that DAS is an effective anticarcinogenic agent in squamous mucosa of the hamster and suggests novel cost-effective strategies for the rapid identification of tissue-specific anticarcinogens and a quantitative assessment of their efficacy.     

Effects of garlic on 7,12-Dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

The inhibitory effect of garlic (Allium sativum Linn) on 7, 12-dimethylbenz[a]anthracene (DMBA)-induced buccal pouch carcinogenesis was investigated in male Syrian hamsters. Measurement of lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GPx), and glutathione S-transferase (GST) was used to monitor the chemopreventive potential of garlic. All hamsters painted on their buccal pouches with DMBA alone for 14 weeks developed well-differentiated squamous cell carcinomas. Diminished lipid peroxidation in the oral tumor tissue was accompanied by a significant increase in the levels of GSH, GPx, and GST. Administration of 250 mg/kg body weight aqueous garlic extract three times a week for 14 weeks effectively suppressed DMBA-induced oral carcinogenesis as revealed by the reduced incidence of neoplasms. The results of the present study suggest that garlic may exert its chemopreventive effects by modulating lipid peroxidation and enhancing the levels of GSH, GPx, and GST.     

Modulation of xenobiotic-metabolizing enzymes by ethanolic neem leaf extract during hamster buccal pouch carcinogenesis

Chemoprevention by medicinal plants is a promising approach for controlling cancer. There is substantial evidence to indicate that chemopreventive agents exert their anticarcinogenic effects by modulation of phase I and phase II xenobiotic-metabolizing enzymes. Therefore, we examined the chemopreventive potential of ethanolic neem leaf extract (ENLE) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into four groups of six animals each. The right buccal pouches of animals in Group I were painted with 0.5 per cent DMBA in liquid paraffin three times per week. Animals in Group 2 painted with DMBA as in group 1, received in addition, intragastric administration of ENLE at a concentration of 200 mg/kg bw three times per week on days alternate to DMBA application. Group 3 was given ENLE alone. Animals in Group 4 served as controls. All animals were killed after an experimental period of 14 weeks. Five out of six hamsters painted with DMBA alone developed squamous cell carcinomas in the buccal pouch. The HBP tumours showed an increase in phase I carcinogen activation (cytochrome P450 and b5) and phase II detoxification enzyme (glutathione-S-transferase, DT-diaphorase and NADPH-diaphorase) activities. In the liver of tumour-bearing animals, enhanced cytochrome P450 and b5 levels were accompanied by a decrease in phase II detoxification enzyme activities. Administration of ENLE effectively suppressed DMBA-induced HBP tumours, decreased cytochrome P450 and b5 levels, and enhanced phase II enzyme activities in the pouch and liver. Our results suggest that the modulation of DMBA metabolism is a possible mechanism for the chemopreventive effects of ethanolic neem leaf extract.     

Garlic induces apoptosis during 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

The apoptosis-inducing capacity of aqueous garlic extract during 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch (HBP) carcinogenesis was investigated in male Syrian hamsters using DNA fragmentation and the apoptosis-associated proteins, tissue transglutaminase (tTG) and Bcl-2. Hamsters were divided into four groups of six animals each. Animals in group 1 were painted with a 0.5% solution of DMBA in liquid paraffin on the right buccal pouches three times a week for 14 weeks. Group 2 animals painted with DMBA as in group 1, in addition received 250 mg/kg body weight aqueous garlic extract orally on days alternate to DMBA application. Group 3 animals received garlic extract as in group 2. Group 4 animals received neither DMBA nor garlic extract and served as the control. The experiment was terminated at the end of 14 weeks. Administration of aqueous garlic extract (250 mg/kg body weight) to animals painted with DMBA inhibited DMBA-induced oral carcinogenesis as revealed by the absence of neoplasms, induction of tTG and inhibition of Bcl-2 expression. The results of the present study suggest that garlic may exert its chemopreventive effect by inducing apoptosis.     

Lupeol, A Bioactive Triterpene, Prevents Tumor Formation During 7,12-Dimethylbenz(a)anthracene Induced Oral Carcinogenesis

The oral cancer chemopreventive efficacy of lupeol, a bioactive triterpene, was assessed by monitoring the tumor incidence and using the status of phase I and II xenobiotic metabolizing enzymes, lipid peroxidation and antioxidants as biochemical end points during 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch carcinogenesis. Oral tumors were developed in the buccal pouch of golden Syrian hamsters by painting with 0.5?% DMBA three times a week for 14?weeks. Well differentiated oral squamous cell carcinoma with marked abnormalities in the status of biochemical markers were noticed in hamsters treated with DMBA alone. Oral administration of lupeol at a dose of 50?mg/kg bw completely inhibited the formation of oral tumors and restored the status of biochemical markers during DMBA induced oral carcinogenesis. The present study thus demonstrates the chemopreventive potential of lupeol in DMBA induced oral carcinogenesis. The chemopreventive potential of lupeol is probably due to its antioxidant or free radical scavenging property and modulating effect on phase I and II xenobiotic metabolizing enzymes in favour of the excretion of carcinogenic metabolites during DMBA induced hamster buccal pouch carcinogenesis.     

The effects of citrus limonoids on hamster buccal pouch carcinogenesis

Two citrus limonoids, limonin and nomilin, were tested for theireffects on the development of 7,12-dimethyIbenz-[a]anthracene(DMBA)-induced buccal pouch epidermoid carcinomas. Forty-fivefemale Syrian hamsters were divided into three equal groups.The left buccal pouches of the animals in each group were pretreatedtopically with two applications of dimethylsulfoxide (DMSO)(group I), a 2.5% solution of limonin dissolved in DMSO (groupII) or a 2.5% solution of nomilin dissolved in DMSO (group III).After this initial treatment, 11 hamsters from each group wereselected. The left buccal pouches of these animals were painted2 or 3 times weekly with a 0.5% solution of DMBA in mineraloil. On alternate days the pouches were painted with DMSO (I),the 2.5% solution of limonin (II) or the 2.5% solution of nomilin(III). The 12 remaining hamsters were used as controls and werepainted with mineral oil and DMSO (I), mineral oil and the 2.5%solution of limonin (II), or mineral oil and the 2.5% solutionof nomilin (III). After 15 weeks the hamsters were killed, thepouches were excised and the tumors were counted and measured.Tumors of variable size were common in the animals treated withDMBA. However, the animals receiving topical applications oflimonin exhibited a 60% reduction in tumor burden. Further comparisonsbetween groups I and II showed that this reduction in tumorburden was due to a 20% decrease in tumor number and a 50% decreasein tumor mass. The results for group III showed that nomilinwas considerably less effective as an inhibitor of DMBA-inducedneoplasia.     

Inhibition of experimental oral carcinogenesis by topical beta carotene

ß-Carotene was found to significantly inhibit theformation of 7, 12-dimethylbenz(a)anthracene (DMBA)-inducedsquamous cell carcinoma of hamster buccal pouch when appliedtopically on days alternate to the application of 0.25% DMBAin heavy mineral oil thrice weekly for 22 weeks. An initialexperiment utilized 40 male young adult Syrian hamsters dividedinto four equal groups. Group 1 had DMBA applied to left buccalpouches thrice weekly. Group 2 had DMBA applied as in group1 but also ß-carotene thrice weekly on days alternateto the DMBA application of 0.25% DMBA in heavy mineral oil thriceweekly for 22 weeks. An initial experiment utilized 40 maleyoung adult Syrian hamsters divided into four equal groups.Group 1 had DMBA applied to left buccal pouches thrice weekly.Group 2 had DMBA applied as in group 1 but also ßcarotene thrice weekly on days alternate to the DMBA application.Group 3 animals were painted with only ß caroteneand group 4 animals were untreated controls. In a second experimentwith 80 animals, ß carotene was found to inhibit oralcarcinogenesis in an initiation-promotion hamster buccal pouchsystem using 0.1% DMBA as initiator and 40% benzoyl peroxideas promoter. ß-Carotene inhibited both initiationand promotion.     

Saffron Reduction of 7,12-Dimethylbenz[a]anthracene-inducedHamster Buccal Pouch Carcinogenesis

Our aim was to investigate the chemopreventive potential of saffron in DMBA-induced hamster buccal pouchcarcinogenesis. Assessment was by monitoring the percentage of tumor bearing hamsters, tumor size as wellas the status of detoxification agents, lipid peroxidation and antioxidants. Oral squamous cell carcinomas wereinduced in the buccal pouch of Syrian golden hamsters by painting them with 0.5% DMBA in liquid paraffin threetimes a week for 14 weeks. We observed 100% oral tumor formation with severe histopathological abnormalitiesin all the hamsters treated with DMBA alone, activities of phase I and phase II detoxification enzymes, lipidperoxidation and antioxidants being significantly altered. Though oral administration of saffron completelyprevented the formation of tumors, we noticed severe hyperplasia and dysplasia in hamsters treated with DMBA,suggesting that tumors might eventually develop. Oral administration of saffron return detoxification enzymes,lipid peroxidation and antioxidants to normal ranges. The chemopreventive potential of saffron thus is likelydue to antioxidant properties and modulating effects on detoxification in favour of the excretion of carcinogenicmetabolites during DMBA-induced hamster buccal pouch carcinogenesis.     

P53 expression, p53 and Ha-ras mutation and telomerase activation during nitrosamine-mediated hamster pouch carcinogenesis

Squamous cell carcinomas (SCC) induced in hamster buccal pouch (HBP) by 22 weeks of topical N-methyl-N-benzylnitrosamine (MBN) treatment (twice-weekly, 10 mg MBN/ml propylene glycol) were evaluated for: (i) altered expression of p53 using immunohistochemistry (IHC); (ii) mutations in Ha-ras and p53 using PCR/single strand conformation polymorphism (SSCP); (iii) telomerase activity using the telomerase repeat amplification protocol (TRAP). Precancerous lesions were also evaluated using p53 IHC. Hamsters were killed for lesion analysis at either 3 days (group A, eight hamsters, 89 carcinomas) or 7 weeks (group B, six hamsters, 105 carcinomas) following the final MBN application. Between 3 days and 7 weeks post-treatment the proportion of tumors exhibiting p53 IHC activity (at least 10% of nuclei stained using D07 antibodies for detection of both mutant and wild-type p53) fell from 91 to 50%. However, during this same post-treatment period the frequency of tumors analyzed exhibiting confirmed sequence alterations in the conserved exons (E5-E8) of p53 remained constant (5/15 = 33% in group A versus 14/45 = 31% in group B). Heightened expression of wild-type p53 resulting from DNA damage in the immediate post-treatment period is likely to have contributed to the high proportion of group A tumors exhibiting p53 IHC activity. Nearly 80% of the identified p53 mutations were G-->A and C-->T transitions. The identified p53 point mutations occurred at or near (within three codons) of the corresponding hot-spot codons (175, 245, 248 and 273) of human oral SCC. The proportion of group A and group B tumors analyzed exhibiting Ha-ras mutations was 1/15 (7%) and 7/45 (16%), respectively. Only four of the observed eight Ha-ras mutations occurred in codons known to result in activation of this gene. Telomerase activation was demonstrated in 11 of 13 group A tumors (85%) and in 23 of 24 (96%) group B tumors analyzed. The alterations in p53, Ha-ras and telomerase activity observed in this HBP-MBN model are similar in many respects to those observed in the analogous human lesions of the head and neck. This model may be particularly useful for development of cancer chemoprevention regimens and multimodality cancer therapies.     

Coffee enhances the development of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinomas

In this study, we examined the effect of roasted coffee extract on 7,12-dimethylbenz[a]anthracene (DMBA)-induced buccal pouch carcinogenesis in male Syrian hamsters using lipid peroxidation, reduced glutathione (GSH) and glutathione peroxidase (GPx) activity as biomarkers of chemoprevention. Forty male hamsters were divided into four groups of 10 animals. The right buccal pouches of the animals in Group 1 was painted with a 0.5% solution of DMBA in liquid paraffin three times a week. The animals in Group 2 painted with DMBA as in Group 1, received in addition 2 ml of 8% black coffee extract intragastrically three times a week on days alternate to DMBA application. Group 3 animals received coffee extract as in Group 2. Animals in Group 4 received neither DMBA nor coffee extract and served as control. The hamsters were sacrificed after an experimental period of 14 weeks. Biochemical measurements were carried out on tumour and normal pouch tissues. Administration of roasted coffee extract had no preventive effect on DMBA-induced oral cancer as revealed by the higher mean tumour volume and tumour burden compared to animals painted with DMBA alone. Diminished lipid peroxidation in the oral tumour tissue was accompanied by a significant increase in the levels of GSH and GPx. CONCLUSIONS: The results of the present study suggest that coffee exerts a tumour enhancing effect when administered during DMBA-induced hamster buccal pouch carcinogenesis.     

Berberine prevents 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis: a biochemical approach

Chemoprevention, a novel and useful approach in experimental oncology, deals with the prevention, suppression, or inhibition of carcinogenesis using natural or synthetic entities. This study evaluated the chemopreventive potential of berberine on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Oral squamous cell carcinoma was developed in the buccal pouch of golden Syrian hamsters by painting with 0.5% DMBA in liquid paraffin three times a week for 14 weeks. Tumor incidence, tumor volume, tumor burden, phase I and phase II carcinogen detoxification agents, lipid peroxidation, antioxidant status, and histopathological changes were assessed in hamsters treated with DMBA alone and in DMBA+berberine-treated animals. Hundred percent tumor incidences with an imbalance in carcinogen-metabolizing enzymes and cellular redox status were observed in hamsters treated with DMBA alone. Oral administration of berberine at a dose of 75 mg/kg body weight (bw) to DMBA-treated hamsters completely prevented tumor incidence and restored the status of the above-mentioned biochemical markers. Berberine, a traditional drug from Southeast Asia, shows promising chemopreventive efficacy in hamster buccal pouch carcinogenesis.     

Anaplastic carcinoma in the buccal pouches of hamsters as a model of oral cancer

An anaplastic model of oral cancer has been developed by abdominal transplantation of carcinomas induced in buccal pouches of hamsters by DMBA. The transplanted tumors were replanted abdominally through five generations. The original carcinomas of the buccal pouch became stable in the abdomen after two generations of such transplantations and could thereafter be retransplanted intraperitoneally with 100% of success, as well as being transferable again to the buccal pouches of hamsters, where they were capable of being maintained as an oral model for anaplastic epidermoid carcinoma.     

Dose-response effect of tomato paste on 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

We evaluated the dose-response effect of tomato paste on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis using lipid peroxidation, reduced glutathione (GSH) and the GSH-dependent enzymes; glutathione peroxidase (GPx), glutathione-S-transferase (GST) and gamma-glutamyltranspeptidase (GGT) as biomarkers of chemoprevention. Hamsters were divided into eight groups of six animals each. The right buccal pouches of animals in group 1 were painted with a 0.5 per cent DMBA in liquid paraffin three times per week. Animals in groups 2 to 4 painted with DMBA as in group 1, received in addition, intragastric administration of tomato paste containing lycopene at concentrations of 2.5, 5 and 10 mgkg(-1)bw, respectively three times per week on days alternate to DMBA application. Groups 5 through 7 were given tomato paste alone. Animals in group 8 served as controls. All animals were killed after an experimental period of 14 weeks. Lipid peroxidation and GSH-dependent antioxidants were measured in the buccal pouch, liver and erythrocytes. Diminished lipid peroxidation in the HBP tumours was associated with enhanced levels of GSH and GSH-dependent enzymes. In contrast to the buccal pouch, the liver and erythrocytes of tumour-bearing hamsters exhibited elevated lipid peroxidation accompanied by compromised antioxidant status. Administration of tomato paste significantly reduced the incidence of HBP tumours, modulated lipid peroxidation and enhanced GSH and GSH-dependent enzymes in the pouch, liver and erythrocytes. Among the three doses used, tomato paste containing 5 mgkg(-1)bw lycopene showed the optimum effect. It is suggested that tomato paste exerts its chemopreventive effects by modulating lipid peroxidation and enhancing antioxidants in the target organ as well as in the liver and erythrocytes.     

GGT reduction in beta carotene-inhibition of hamster buccal pouch carcinogenesis

Levels of activity for gamma glutamyl transpeptidase (GGT) were studied in hamster buccal pouches developing DMBA-induced epidermoid carcinomas and in pouches in which carcinogenesis was inhibited by topical application of beta carotene. The beta carotene acted to inhibit tumor development when applied topically on days alternate to the application of 0.25% DMBA in heavy mineral oil thrice weekly for 22 weeks. Forty male young adult Syrian hamsters were divided into four equal groups. Group 1 had DMBA applied to left buccal pouches thrice weekly. Group 2 had DMBA applied as in Group 1 but also beta carotene thrice weekly on days alternate to the DMBA application. Group 3 animals were painted with only beta carotene and Group 4 animals were untreated controls. The left buccal pouches were dissected at autopsy and divided in half. One half was fixed in formalin, sectioned in paraffin and stained with hematoxylin-eosin for histologic study. The other half was prepared for the histochemical demonstration of GGT activity using epithelial whole mount preparations. GGT activity was found to be reduced in the left buccal pouches of those animals treated with both beta carotene and DMBA when compared to those animals treated with DMBA alone.     

Chemopreventive Potential of Coumarin in 7, 12-dimethylbenz[a] anthracene Induced Hamster Buccal Pouch Carcinogenesis

The aim of the present study was to investigate the chemopreventive effect of coumarin against 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis by monitoring tumorincidence and histopathological changes as well as by analyzing the status of biochemical markers (lipidperoxidation, enzymatic and non-enzymatic antioxidants, phase I and phase II detoxification enzymes). Oralsquamous cell carcinomas were induced in the buccal pouch of Syrian golden hamsters by painting with 0.5%DMBA in liquid paraffin three times a week for 14 weeks. We noted 100% tumor formation with markedabnormalities in the biomarkers status in hamsters treated with DMBA alone. Oral administration of coumarinat a dose of 100 mg/kg body weight (bw) to DMBA treated hamsters completely prevented the tumor formationas well as restored the staus of biochemical variables. The results of the present study thus suggest that thechemopreventive effect of coumarin is probably due to its anti-lipid peroxidative potential and modulating effecton carcinogen detoxification agents in favor of the excretion of ultimate carcinogenic metabolites of DMBAduring DMBA-induced hamster buccal pouch carcinogenesis.