K.V.P. Chandra Mohan

In vitro evaluation of the anticancer effect of lactoferrin and tea polyphenol combination on oral carcinoma cells

We investigated the anticancer effects of green and black tea polyphenols alone and in combination with bovine milk lactoferrin (bLF) on human tongue squamous carcinoma (CAL‐27) and normal human gingival fibroblast (HGF) cells. Both green (Polyphenon‐E;P‐E) and black tea polyphenols (Polyphenon‐B;P‐B) preferentially inhibit the growth of CAL‐27 cells in a dose‐dependent manner. Based on the IC50 values, P‐E was found to be more effective than P‐B and the combination of P‐E and bLF (1:2 ratio) exhibited synergistic inhibition of CAL‐27 cells. Analysis of the mechanism revealed nuclear fragmentation and condensation with appearance of the Ao peak indicative of apoptosis. Furthermore, tea polyphenols transduced the apoptosis signal via generation of reactive oxygen species and decrease in the Bcl‐2/Bax ratio thereby inducing mitochondrial permeability transition with consequent activation of caspase‐3. Overall, the potency of cytotoxic and apoptosis inducing effects of dietary agents on CAL‐27 cells was in the order P‐E and bLF combination (1:2 ratio) > P‐E > P‐B. These results suggest that a “designer” approach may be useful for oral cancer prevention strategies.

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.

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.

Dose-response effects of tomato lycopene on lipid peroxidation and enzymic antioxidants in the hamster buccal pouch carcinogenesis model

We evaluated the chemopreventive efficacy of tomato lycopene at three different concentrations on DMBA-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into eight groups. The right buccal pouches of animals in group 1 were painted with 0.5 per cent DMBA three times a week. Animals in groups 2 to 4 painted with DMBA as in group 1, received in addition, intragastric administration of tomato lycopene of concentrations 2.5, 5 and 10 mg/kg bw respectively three times a week on days alternate to DMBA application. Groups 5 through 7 were given tomato lycopene alone while group 8 served as untreated control. All the animals were killed after an experimental period of 14 weeks. Lipid peroxidation and the status of enzymic antioxidants in the buccal pouch, liver and erythrocytes of hamsters in all the groups were assessed. All the hamsters painted with DMBA alone, developed oral squamous cell carcinomas. Diminished lipid peroxidation in the HBP tumors was accompanied by decreased activities of superoxide dismutase and catalase with increase in glutathione peroxidase. However, in the liver and erythrocytes of tumor-bearing animals increased lipid peroxidation was associated with compromised antioxidant defenses. Administration of tomato paste containing 5mg/kg bw of lycopene inhibited HBP tumor development as revealed by decreased tumour incidence and tumour burden. We suggest that tomato lycopene exerts its chemopreventive effects by modulating the oxidant-antioxidant profile in the target organ as well as in the liver and erythrocytes.

Combination Chemoprevention of Hamster Buccal Pouch Carcinogenesis by Bovine Milk Lactoferrin and Black Tea Polyphenols

Combination chemoprevention is a promising approach for oral cancer prevention. The authors evaluated the combined chemopreventive effects of bovine milk lactoferrin (bLF) and black tea polyphenols (Polyphenon-B) in a clinically relevant in vivo model of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Although dietary administration of bLF and Polyphenon-B alone significantly reduced the tumor incidence, combined administration of bLF and polyphenon-B was more effective in inhibiting DMBA-induced genotoxicity and development of HBP carcinomas by modulation of carcinogen-metabolizing enzymes and cellular redox status. These results suggest that a “designer item” approach will be useful for human oral cancer prevention strategies.

Sequential Changes in the Cellular Redox State During 7,12-Dimethylbenz(a)anthracene-Induced Carcinogenesis in the Hamster Buccal Pouch

Our objective was to elucidate sequential changes in the oxidant-antioxidant status during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. In designing the study, we divided hamsters into experimental and control groups. The right buccal pouches of the experimental animals were painted three times a week with a 0.5% solution of DMBA in liquid paraffin. The control animals received paraffin alone. The hamsters were killed after 1, 4, 8, 12, and 16 weeks of DMBA treatment, and the buccal pouches were examined for histopathological changes. The extent of lipid peroxidation and the status of glutathione-dependent antioxidants were evaluated in the buccal pouch, liver, and erythrocytes. Our results showed that the experimental animals developed severe hyperplasia and hyperkeratosis after 4 weeks, dysplasia after 8 weeks, and well-developed squamous cell carcinomas after 16 weeks of DMBA application. Topical application of DMBA increased lipid peroxidation in the buccal pouch up to the 8th week; there was a substantial fall after 12 weeks and significantly low levels after 16 weeks. This was accompanied by a sustained increase in reduced glutathione (GSH) and the activities of glutathione peroxidase (GPx), glutathione-S-transferase (GST), and γ-glutamyltranspeptidase (GGT) throughout the carcinogenic progression. However, in the liver and erythrocytes, the concentrations of lipid peroxides were higher, and GSH- and GSH-dependent enzyme activities were lower than in the controls throughout the experiment. This study has revealed intrinsic differences in the cellular redox state in the target organ and host tissues of tumor-bearing animals. We suggest that measurement of lipid peroxidation and GSH-dependent antioxidants could be valuable in evaluating carcinogenic progression and the effects of putative chemopreventive agents in the hamster buccal pouch model.

Modulatory effects of black tea polyphenols on rat forestomach carcinogenesis.

ABSTRACT The present study was designed to evaluate the chemopreventive effects of black tea polyphenols (Polyphenon-B) on N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats. Intragastric administration of MNNG induced well-differentiated squamous cell carcinomas that showed diminished mitochondrial lipid and protein oxidation and an increase in antioxidants. In contrast to tumor tissue, the liver mitochondria of tumor-bearing animals showed elevated lipid and protein oxidation with compromised antioxidant defenses. Dietary administration of Polyphenon-B effectively suppressed MNNG-induced stomach tumors, modulated mitochondrial lipid and protein oxidation, and enhanced antioxidant enzyme activities in the stomach and liver. Our results suggest that Polyphenon-B may exert its chemopreventive effects by modulating mitochondrial cellular redox status in the tumor as well as in the host liver.

Erratum to: Nimbolide a limonoid from Azadirachta indica

In the third paragraph of Introduction section, the following words should have been deleted: “(5,7,4′-trihydroxy-3′,5′diprenylflavanone)”. Paragraph should read as below: Azadirachta indica A. Juss, commonly known as neem, elaborates a vast array of bioactive phytochemicals that exhibit potent medicinal properties [11]. Although all parts of the neem tree are recognized to confer health benefits, the medicinal utilities for neem leaf are more wide ranging and include immunomodulatory, antiinflammatory, antioxidant, antimutagenic, and anticarcinogenic effects [12]. In previous reports from this laboratory, we have demonstrated that the chemopreventive effects of ethanolic neem leaf extract against experimental oral and gastric carcinogenesis are mediated by modulation of xenobiotic-metabolising enzymes, upregulation of antioxidants, inhibition of cell proliferation and induction of apoptosis [13–15]. Recently, we identified nimbolide, a limonoid, as one of the major constituents in neem leaf fractions by highperformance liquid chromatography [16]. Although nimbolide was shown to exert cytotoxicity against a panel of cancer cell lines, the effect of nimbolide on markers of cell proliferation and apoptosis has not been investigated [17–19].