Modulating Effect of Lupeol on the Expression Pattern of Apoptotic Markers in 7, 12-Dimethylbenz(a)anthracene Induced Oral Carcinogenesis

Apoptosis, also known as cell suicide or programmed cell death, removes unwanted and genetically damagedcells from the body. Evasion of apoptosis is one of the major characteristic features of rapidly proliferating tumorcells. Chemopreventive agents inhibit or suppress tumor formation through apoptotic induction in target tissues.The aim of the present study was to investigate the pro-apoptotic potential of lupeol during 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch carcinogenesis. Topical application of 0.5% DMBA threetimes a week for 14 weeks in the buccal pouches of golden Syrian hamsters resulted in oral squamous cellcarcinoma. The expression pattern of apoptotic markers was analyzed using immunohistochemistry (p53, Bcl-2,Bax) and ELISA reader (caspase 3 and 9). In the present study, 100% tumor formation with defects in apoptoticmarkerexpression pattern was noticed in hamsters treated with DMBA alone. Oral administration of lupeol ata dose of 50mg/kg bw completely prevented the formation oral tumors as well as decreased the expression p53and Bcl-2, while increasing the expression of Bax and the activities of caspase 3 and 9. The present study thusindicated that lupeol might inhibit DMBA-induced oral tumor formation through its pro-apoptotic potentialin golden Syrian hamsters.     

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.     

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.     

Combination of S-allylcysteine and lycopene induces apoptosis by modulating Bcl-2, Bax, Bim and caspases during experimental gastric carcinogenesis.

Combination chemoprevention by diet-derived agents that induce apoptosis is a promising strategy to control gastric cancer, the second most common malignancy worldwide. The present study was undertaken to investigate the apoptosis-inducing potential of a combination of S-allylcysteine (SAC), an organosulphur constituent of garlic and lycopene, a tomato carotenoid during N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) and saturated sodium chloride (S-NaCl)-induced gastric carcinogenesis in Wistar rats using the apoptosis-associated proteins Bcl-2, Bax, Bim, caspase 8 and caspase 3 as markers. Animals administered MNNG followed by S-NaCl developed squamous cell carcinomas of the stomach associated with increased Bcl-2 expression and decreased expression of Bax, Bim, caspase 8 and caspase 3. Although SAC and lycopene alone significantly suppressed the development of gastric cancer, administration of SAC and lycopene in combination was more effective in inhibiting MNNG-induced stomach tumours and modulating the expression of apoptosis-associated proteins. Our results suggest that induction of apoptosis by SAC and lycopene combination represents one of the possible mechanisms that could account for their synergistic chemopreventive activity against gastric cancer.     

Expression of epidermal growth factor receptor, polyamine levels, ornithine decarboxylase activity, micronuclei, and transglutaminase I in a 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch carcinogenesis model

The expression of epidermal growth factor receptor and transglutaminase type I, polyamine (putrescine, spermidine, and spermine) levels, ornithine decarboxylase activity, and micronuclei occurrence were assessed in the 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch model to elucidate the role and timing of changes in different growth and differentiation markers during carcinogenesis. DMBA (0.5%) in heavy mineral oil was applied to the right buccal pouch 3 times per wk for up to 16 wk; controls received heavy mineral oil alone. Hamsters were killed after 0, 4, 8, and 16 wk. Frozen tissue was chemically analyzed for polyamine levels and ornithine decarboxylase activity and was also used for immunohistochemical analysis of transglutaminase I. Paraffin-embedded sections were used for epidermal growth factor receptor immunohistochemical determinations and for micronucleated cell assays. Hyperplasia was detected by histological analysis at 4 wk, dysplasia with or without papillomatous changes at 8 wk, and squamous cell carcinoma at 16 wk. Epidermal growth factor receptor was not expressed in the normal buccal epithelial layer, at a moderate level in both the superficial keratin and basal cell layers in hyperplastic epithelium, and at very high levels in both dysplasia and squamous cell carcinoma. Transglutaminase I was expressed at a limited level in normal buccal mucosa, was expressed at a low level in the basal layer of hyperplastic lesions, was somewhat elevated in dysplasia, and was markedly enhanced in squamous cell carcinoma. Putrescine and spermidine levels and ornithine decarboxylase activity increased dramatically after 8 and 16 wk of DMBA. Micronucleated cells increased after 4 wk of DMBA treatment, that high level sustained during all stages of carcinogenesis. We suggest that these biological markers could be excellent intermediate end points in assessing the effects of various chemopreventive agents to be tested in the hamster buccal pouch model and in human clinical trials.     

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.     

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.     

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.     

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.     

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.     

Expression of survivin and XIAP for DMBA-induced hamster buccal pouch squamous cell carcinogenesis is associated with p53 accumulation

Apoptosis (programmed cell death) is regulated by a number of inhibitory or stimulatory factors. One such family of antiapoptotic proteins is the inhibitors of apoptosis proteins (IAPs), of which survivin and X chromosome-linked IAP (XIAP) are members. The expression of survivin and XIAP, as well as their association with p53, in chemically-induced experimental oral carcinogenesis is not completely understood. The objective of the present study was, therefore, to investigate the protein expression of these two IAP family members and their relationship with p53 status, in 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch squamous cell carcinogenesis. Immunohistochemical analysis of survivin, XIAP and p53 protein expression was performed in DMBA-induced pouch squamous cell carcinogenesis. Fifty outbred, young (6 weeks), male Syrian golden hamsters (Mesocricatus auratus) were randomly divided into three experimental groups (each group consisting of 10 animals treated with DMBA for 3-, 7- or 14-weeks), and two control groups (with 10 animals in each). The pouches of the three experimental groups were painted bilaterally with a 0.5% DMBA solution three times a week. The treatment protocol for animals in one of the control groups was identical with only mineral oil applied, while the other control group remained untreated throughout the experiment. Survivin staining could not be detected by immunohistochemistry in any of the untreated or mineral oil treated hamster pouch-tissue specimens. Cytoplasmic staining of survivin proteins was apparent in the entire epithelial layer (excluding the keratinized layer) in all 3-week DMBA treated pouch-tissue analyzed. In addition, cytoplasmic survivin staining was observed in all specimens of 7- and 14-week DMBA treated pouch-tissue. XIAP positivity was confined to the outermost keratinized layer of the pouch-tissue from control animals and those treated with DMBA for 3-weeks. However, XIAP staining was detected in the whole epithelial layer (except the basal layer) in 7- and 14-week DMBA treated pouch-tissue. p53 was not detected in any untreated and mineral oil treated pouch-tissue, whereas nuclear p53 staining was observed for all 3-, 7- and 14-week DMBA treated pouch-tissue. The results of this study demonstrate the association between survivin/XIAP and p53 expression in this experimental model system for oral carcinogenesis, although their exact interactions remain to be clarified. Moreover, our findings suggest that the DMBA-induced hamster buccal pouch mucosa may serve as an appropriate experimental model for investigation of potential novel therapeutic tools for oral squamous-cell carcinomas.     

Anti-cell Proliferative and Anti-angiogenic Potential of Andrographolide During 7,12- Dimethylbenz(a)anthracene Induced Hamster Buccal Pouch Carcinogenesis

Our aim was to explore anti-cell proliferative and anti-angiogenic potential of andrographolide by analyzingthe expression pattern of cell proliferative (PCNA, Cyclin D1) and angiogenic (VEGF) markers during 7,12-dimethylbenz(a)anthracene (DMBA) induced hamster buccal pouch carcinogenesis. DMBA painting threetimes a week for 14 weeks in the buccal pouch of golden Syrian hamsters resulted in oral tumors which werehistopathologically diagnosed as well differentiated squamous cell carcinoma. Immunohistochemical (PCNA,VEGF) and RT-PCR (Cyclin D1) studies revealed over expression of PCNA, VEGF and Cyclin D1 in the buccalmucosa of hamsters treated with DMBA alone. Oral administration of andrographolide at a dose of 50 mg/kgbw to hamsters treated with DMBA not only suppressed the histological abnormalities but also down regulatedthe expression of PCNA, VEGF and Cyclin D1. The results of the present study suggest that andrographolidesuppressed tumor formation in the buccal mucosa of hamsters treated with DMBA through its anti-cellproliferative and anti-angiogenic potential.     

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.     

Black tea polyphenols protect against 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

Dietary chemoprevention has emerged as a cost-effective approach for cancer control. We evaluated the chemopreventive effects of black tea polyphenols (Polyphenon-B) administration during the preinitiation phase of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. The expression of proliferating cell nuclear antigen (PCNA) in the buccal pouch and the concentration of lipid peroxides, protein carbonyl, and the antioxidant status in the buccal pouch, liver and erythrocytes were used as biomarkers of chemoprevention. All the hamsters painted with DMBA alone for 14 weeks developed buccal pouch carcinomas associated with increased expression of PCNA, diminished lipid and protein oxidation, and enhanced antioxidant status. In the liver and erythrocytes of tumor-bearing animals, enhanced oxidation of lipids and proteins was accompanied by compromised antioxidant defenses. Dietary administration of Polyphenon-B effectively suppressed DMBA-induced HBP carcinogenesis as revealed by decreased incidence of tumours and PCNA expression. In addition, Polyphenon-B modulated lipid and protein oxidation and enhanced the antioxidant status in the pouch, liver, and erythrocytes. We suggest that Polyphenon-B exerts its chemopreventive effects by inhibiting cell proliferation in the target tissue and modulating the oxidant-antioxidant status in the target as well as in host tissues.     

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.     

Pretreatment with black tea polyphenols modulates xenobiotic-metabolizing enzymes in an experimental oral carcinogenesis model

The objective of this study was to evaluate the chemopreventive potential of the black tea polyphenols Polyphenon-B and BTF-35 during the preinitiation phase of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into six groups. Animals in groups 2 and 3 received diet containing Polyphenon-B and BTF-35, respectively, 4 weeks before carcinogen administration when they were 6 weeks of age and continued until the final exposure to carcinogen. At 10 weeks of age, animals in groups 1, 2, and 3 were painted with 0.5% DMBA three times a week for 14 weeks. Animals in groups 4 and 5 were given Polyphenon-B and BTF-35 alone, respectively, as in groups 2 and 3. Animals in group 6 served as control. All the animals were sacrificed after an experimental period of 18 weeks. Phase I and phase II xenobiotic-metabolizing enzymes and 8-hydroxy-deoxyguanosine (8-OH-dG) in the buccal pouch and liver were used as biomarkers of chemoprevention. Hamsters painted with DMBA showed increased expression of 8-OH-dG and enhanced activities of phase I (CYP450; total as well as CYP1A1, 1A2, and 2B isoforms and cytochrome b5) and phase II (GST and quinone reductase) xenobiotic-metabolizing enzymes with increased immunohistochemical expression of CYP1A1, and CYP1B1 isoforms in the buccal pouch. This was accompanied by increased phase I and decreased phase II enzyme activities in the liver. Administration of Polyphenon-B and BTF-35 significantly decreased tumor incidence, oxidative DNA damage, phase I enzyme activities as well as expression of CYP1A1 and CYP1B1 isoforms, while enhancing phase II enzyme activities in the buccal pouch and liver. Our results provide a mechanistic basis for the chemopreventive potential of black tea polyphenols. Furthermore, the greater efficacy of BTF-35 in chemoprevention of HBP carcinomas via inhibition of oxidative DNA damage and modulation of xenobiotic-metabolizing enzymes may have a major impact in human oral cancer prevention.     

Acute inhibition of DNA synthesis in hamster buccal pouch epithelium exposed to indirect acting carcinogens

Inhibition of DNA synthesis was observed and quantitated in hamster buccal pouch epithelium exposed in vivo and in vitro to indirect acting carcinogens. Topical application of a 0.5% solution of the potent hamster buccal pouch carcinogen 7,12-dimethylbenz[a]-anthracene (DMBA) acutely inhibited epithelial DNA synthesis by 40-65%, as indicated by a decrease in [3H]thymidine incorporation over a period of 24 h. When applied twice at a concentration of 2%, N-methyl-N-benzylnitrosamine (MBN), another potent buccal pouch carcinogen, inhibited epithelial DNA synthesis by 76% within a period of 4 h. A similar acute inhibitory effect on DNA synthesis was observed when explants of buccal pouch mucosa, exhibiting continuous cell replication, were exposed in vitro in the presence of MBN or DMBA for periods up to 12 and 24 h, respectively. The inhibitory effect of DMBA was greater than that of other polycyclic aromatic hydrocarbons of lesser carcinogenic potency in this tissue. This study demonstrates that the metabolic activation of indirect acting carcinogens leading to acute cytotoxicity and inhibition of DNA synthesis occurs rapidly in hamster buccal pouch mucosa exposed to these agents in vitro as well as in vivo. The experimental imposition of an acute inhibitory pressure, applied as demonstrated in this report, may enable the detection of precancerous cells which have acquired the property of resistance to this cytotoxic effect in the course of carcinogenesis. In principle, the in vitro approach, coupled with autoradiography, may be useful in identifying microscopic foci of resistant preneoplastic cells in samples of human oral mucosa. 24R01 34160     

Inhibitory Effects of Dietary Protocatechuic Acid and Costunolide on 7,12-Dimethylbenz[a]anthracene-induced Hamster Cheek Pouch Carcinogenesis

The modifying effects of dietary exposure to two natural products, protocatechuic acid (PCA) and Costunolide during the development of neoplasms in oral carcinogenesis initiated with 7,12-dimethyl-benz[ a ]anthracene (DMBA) were investigated in male Syrian golden hamsters. All hamsters except those in the test chemical alone and control groups received DMBA (0.5%) in mineral oil to the right buccal pouch 3 times per week for 4 or 6 weeks. At 13 weeks of age, the groups exposed to DMBA were fed diet containing PCA or Costunolide at a dose of 0.2 g/kg diet (200 ppm) for 17 weeks. The other groups consisted of hamsters given mineral oil alone for 6 weeks, or given 200 ppm PCA or Costunolide alone, or untreated. All animals were necropsied at the termination of the experiment (week 24). PCA or costunolide significantly decreased the tumor burden (P<0.001- P <0.05) and the extent of dysplastic areas (%) (P<0.001-P<0.05). PCA significantly decreased the mean number of AgNORs/nucleus (P<0.05). The BrdUrd-labeling index was reduced by dietary administration of test compounds, though not significantly. These results suggest that PCA and costunolide inhibited hamster buccal pouch carcinogenesis and such inhibition may be related to suppression of cell proliferation in the buccal mucosa. It was also found that telomerase activity expressed in neoplastic and preneoplastic lesions of hamster buccal pouch epithelium after DMBA treatment correlated with the histopathological degree of malignancy.     

Inhibition of Growth,Induction of Apoptosis and Alteration of GeneExpression by Tea Polyphenols in the Highly Metastatic Human Lung Cancer Cell Line NCI-H460

Lung cancer is a complex group of diseases but each lesion is thought to originate from a single mutated progenitor ‍cell. It is evident that multiple genetic changes are involved in the generation of each specific type of lung cancer. Due ‍to the high complexity of these processes and rapid metastasis, treatment of advanced lung cancer, particularly of ‍NSCLCs, is far from satisfactory. Thus, there is a need for innovative strategies for modulation of adverse alteration ‍in protooncogene or tumor suppressor genes so that lung carcinogenesis can be suppressed or delayed. To this end, ‍we have evaluated the effects of tea compounds (theaflavins, epicatechin-gallate and epigallo-catechin-gallate) on ‍proliferation and apoptosis and associated gene expression in a highly metastatic human lung cancer cell line NCIH460. ‍Significant reduction of cell proliferation, detected in situ by BrdU incorporation, and induction of apoptosis, ‍assessed by the by the TUNEL method, were noted following treatments. Expression of p53, Bcl-2, c-Myc and H-Ras, ‍was localized by immunocytochemistry and analysed by Western blotting. Tea compounds upregulated expression ‍of p53, downregulated expression of Bcl-2 but there was no significant influence on H-ras and c-Myc expressions. It ‍is suggested that tea compounds can influence genetic alteration to disfavour, growth and survival of lung cancer ‍cells.