Dietary turmeric modulates DMBA-induced p21ras, MAP kinases and AP-1/NF-kappaB pathway to alter cellular responses during hamster buccal pouch carcinogenesis.
Garg Rachana,Ingle Arvind,Maru Girish
Toxicology and applied pharmacology
The chemopreventive efficacy of turmeric has been established in experimental systems. However, its mechanism(s) of action are not fully elucidated in vivo. The present study investigates the mechanism of turmeric-mediated chemoprevention in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis at 2, 4, 6, 10 and 12 weeks. Dietary turmeric (1%) led to decrease in DMBA-induced tumor burden and multiplicity, and enhanced the latency period in parallel, to its modulatory effects on oncogene products and various cellular responses during HBP tumorigenesis. DMBA-induced expression of ras oncogene product, p21 and downstream target, the mitogen-activated protein kinases were significantly decreased by turmeric during HBP carcinogenesis. Turmeric also diminished the DMBA-induced mRNA expression of proto-oncogenes (c-jun, c-fos) and NF-kappaB, leading to decreased protein levels and in further attenuation of DMBA-induced AP-1/NF-kappaB DNA-binding in the buccal pouch nuclear extracts. Besides, buccal pouch of hamsters receiving turmeric diet showed significant alterations in DMBA-induced effects: (a) decrease in cell proliferation (diminished PCNA and Bcl2 expression), (b) enhanced apoptosis (increased expression of Bax, caspase-3 and apoptotic index), (c) decrease in inflammation (levels of Cox-2, the downstream target of AP-1/NF-kappaB, and PGE2) and (d) aberrant expression of differentiation markers, the cytokeratins (1, 5, 8, and 18). Together, the protective effects of dietary turmeric converge on augmenting apoptosis of the initiated cells and decreasing cell proliferation in DMBA-treated animals, which in turn, is reflected in decreased tumor burden, multiplicity and enhanced latency period. Some of these biomarkers are likely to be helpful in monitoring clinical trials and evaluating drug effect measurements.
Chemopreventive potential of resveratrol in mouse skin tumors through regulation of mitochondrial and PI3K/AKT signaling pathways.
Roy Preeti,Kalra Neetu,Prasad Sahdeo,George Jasmine,Shukla Yogeshwer
PURPOSE:To investigate the chemopreventive potential of resveratrol, a phytoalexin found in seeds and skin of grapes, berries and peanuts in 7,12 dimethyl benz(a)anthracene (DMBA) induced mouse skin tumorigenesis. METHODS:Topical treatment of resveratrol was given to the animals 1 h prior to DMBA for 28 weeks. At the end of the study period, the skin tumors were dissected out and western blotting was carried out to examine the regulation of proteins involved in anti-tumorigenesis in response to resveratrol. RESULTS:Chemopreventive properties of resveratrol were reflected by delay in onset of tumorigenesis, reduced cumulative number of tumors, and reduction in tumor volume. Results of the western blotting showed that resveratrol treatment increased the DMBA suppressed p53 and Bax while decreased the expression of Bcl-2 and Survivin. Further, resveratrol supplementation resulted in release of cytochrome C, caspases activation, increase in apoptotic protease-activating factor-1 (Apaf-1) as mechanism of apoptosis induction. Resveratrol was also found to inhibit skin tumorigenesis through regulation of Phosphatidylinositol-3-kinase (PI3K)/ and AKT proteins which are implicated in cancer progression because it stimulates proliferation and suppresses apoptosis. CONCLUSIONS:Based on the results we can conclude that resveratrol regulates apoptosis and cell survival in mouse skin tumors as mechanism of chemoprevention hence deserve to be a chemopreventive agent.
Synergistic effect of vitamin E and selenium in the chemoprevention of mammary carcinogenesis in rats.
Horvath P M,Ip C
The present study showed that vitamin E, although ineffective by itself, was able to potentiate the ability of selenium to inhibit the development of mammary tumors induced by dimethylbenz(a)anthracene (DMBA) in rats. Animals were maintained on a high-polyunsaturated fat (20% corn oil) diet in order to increase the degree of oxidant stress; additional selenium and/or vitamin E were present at a concentration of 2.5 and 1000 mg/kg of diet, respectively. It should be noted that rats tolerated these levels of supplementation very well with no obvious undesirable effect. Furthermore, our results indicated that vitamin E facilitated the anticarcinogenic action of selenium only when it was present during the proliferative phase. We then proceeded to examine whether DMBA administration would lead to any persistent damage in tissue peroxidation or changes in activities of enzymes associated with peroxide metabolism. It was found that DMBA resulted in an acute but modest increase in lipid peroxidation at 24 hr after carcinogen treatment. This perturbation was only of a transient nature. By comparing the response in a target tissue (mammary fat pad) and a non-target tissue (liver), it can be inferred that DMBA may have a differential effect on the degree of oxidant stress. The antagonistic effect of selenium and vitamin E in suppressing lipid peroxidation was then evaluated. Several conclusions can be drawn regarding the antioxidant potency of these agents in conjunction with their efficacies in cancer prevention. First, although vitamin E is a more effective antioxidant than selenium, it is apparent that systemic suppression of lipid peroxidation by vitamin E subsequent to a carcinogenic insult is not sufficient to inhibit tumor formation. Vitamin E supplementation increases significantly the microsomal hydroperoxidase activity. At the present time, it is unclear what role, if any, this enzyme plays in the synergistic effect of vitamin E and selenium in the inhibition of tumorigenesis. Secondly, the anticarcinogenic action of high levels of selenium is not related to its biochemical function in the regulation of the selenium-dependent glutathione peroxidase. The explanation for this is that the enzyme is already operating at near maximal capacity under normal physiological conditions. Additional selenium will not further increase its activity, since the enzyme protein becomes the limiting factor. Finally, vitamin E may be able to provide a more favorable climate against oxidant stress, thereby potentiating the action of selenium via some other mechanism.
Mammary cancer chemoprevention by inorganic and organic selenium: single agent treatment or in combination with vitamin E and their effects on in vitro immune functions.
Ip C,White G
The chemopreventive efficacies of selenate, selenite, selenium dioxide, selenomethionine and selenocystine were examined during the promotion phase of carcinogenesis in the 7,12-dimethylbenz[a]anthracene-induced mammary tumor model in rats. Each agent was added to the diet at a final concentration of 3 p.p.m. selenium. In general there was no significant difference in the potency of these five selenium compounds in inhibiting the development of mammary tumors. The interaction of vitamin E (500 p.p.m.) with either selenite or selenomethionine was further characterized in a second carcinogenesis study. Results of this experiment suggested that vitamin E enhanced the protective effect of selenite but not that of selenomethionine. In an attempt to explore the synergistic mechanism of selenium and vitamin E, the effects of these two agents on mitogen-induced blastogenesis and natural killer cytotoxic activity were also investigated. No consistent changes in these in vitro immune functions were detected resulting from supranutritional feeding of either selenite or vitamin E or both. The metabolism of inorganic versus organic selenium was discussed in relation to their role in the control of neoplastic growth as well as to their selective modulation by vitamin E.
Cyclin D1 induction by benzo[a]pyrene-7,8-diol-9,10-epoxide via the phosphatidylinositol 3-kinase/Akt/MAPK- and p70s6k-dependent pathway promotes cell transformation and tumorigenesis.
Ding Jin,Ning Beifang,Gong Wenfeng,Wen Wen,Wu Kun,Liang Junqing,He Guoping,Huang Shanna,Sun Wen,Han Tao,Huang Lei,Cao Guangwen,Wu Mengchao,Xie Weifen,Wang Hongyang
The Journal of biological chemistry
Benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE), the major metabolite of B[a]P, has been well recognized as one ubiquitous carcinogen, but the molecular mechanism involved in its carcinogenic effect remains obscure. In the present study, we found that bronchial epithelial cells (Beas-2B) and hepatocytes treated with B[a]PDE presented a significant increase of cyclin D1 expression. Moreover, Akt, p70(s6k), and MAPKs including JNK, Erks, and p38 were notably activated in B[a]PDE-treated Beas-2B cells, whereas NF-kappaB, NFAT, and Egr-1 were not. Our results demonstrated that JNK and Erks were required in B[a]PDE-induced cyclin D1 expression because the inhibition of JNK or Erks by a selective chemical inhibitor or dominant negative mutant robustly impaired the cyclin D1 induction by B[a]PDE. Furthermore, we found that overexpression of the dominant negative mutant of p85 (regulatory subunit of phosphatidylinositol 3-kinase) or Akt dramatically suppressed B[a]PDE-induced JNK and Erk activation as well as cyclin D1 expression, suggesting that cyclin D1 induction by B[a]PDE is via the phosphatidylinositol 3-kinase/Akt/MAPK-dependent pathway. In addition, we clarified that p70(s6k) is also involved in B[a]PDE-induced cyclin D1 expression because rampamycin pretreatment dramatically reduced cyclin D1 induction by B[a]PDE. More importantly, we demonstrated that up-regulated cyclin D1 by B[a]PDE plays a critical role in oncogenic transformation and tumorigenesis of Beas-2B cells. These results not only broaden our knowledge of the molecular mechanism of B[a]PDE carcinogenicity but also lead to the further study of chemoprevention of B[a]PDE-associated human cancers.
Gene expression signature of DMBA-induced hamster buccal pouch carcinomas: modulation by chlorophyllin and ellagic acid.
Vidya Priyadarsini Ramamurthi,Kumar Neeraj,Khan Imran,Thiyagarajan Paranthaman,Kondaiah Paturu,Nagini Siddavaram
Chlorophyllin (CHL), a water-soluble, semi-synthetic derivative of chlorophyll and ellagic acid (EA), a naturally occurring polyphenolic compound in berries, grapes, and nuts have been reported to exert anticancer effects in various human cancer cell lines and in animal tumour models. The present study was undertaken to examine the mechanism underlying chemoprevention and changes in gene expression pattern induced by dietary supplementation of chlorophyllin and ellagic acid in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by whole genome profiling using pangenomic microarrays. In hamsters painted with DMBA, the expression of 1,700 genes was found to be altered significantly relative to control. Dietary supplementation of chlorophyllin and ellagic acid modulated the expression profiles of 104 and 37 genes respectively. Microarray analysis also revealed changes in the expression of TGFβ receptors, NF-κB, cyclin D1, and matrix metalloproteinases (MMPs) that may play a crucial role in the transformation of the normal buccal pouch to a malignant phenotype. This gene expression signature was altered on treatment with chlorophyllin and ellagic acid. Our study has also revealed patterns of gene expression signature specific for chlorophyllin and ellagic acid exposure. Thus dietary chlorophyllin and ellagic acid that can reverse gene expression signature associated with carcinogenesis are novel candidates for cancer prevention and therapy.
Chemopreventive effects of NSAIDs as inhibitors of cyclooxygenase-2 and inducers of apoptosis in experimental lung carcinogenesis.
Setia Shruti,Vaish Vivek,Sanyal Sankar Nath
Molecular and cellular biochemistry
Roles of cyclooxygenase (COX) enzyme and intrinsic pathway of apoptosis have been explored for the chemopreventive effects of non-steroidal anti-inflammatory drugs (NSAIDs) on 9,10-dimethyl benz(a)anthracene (DMBA)-induced lung cancer in rat model. 16 weeks after the administration of DMBA, morphological analysis revealed the occurrences of tumours and lesions, which were regressed considerably with the co-administration of indomethacin and etoricoxib, the two NSAIDs under investigation. DMBA group was marked by hyperplasia and dysplasia as observed by histological examination, and these features were corrected to a large extent by the two NSAIDs. Elevated levels of COX-2 were seen in the DMBA group, the enzyme responsible for prostaglandin synthesis during inflammation and cancer, whilst the expression of the constitutive isoform, COX-1, was equally expressed in all the groups. Apoptosis was quantified by studying the activities of apaf-1, caspase-9, and 3 by immunofluorescence and western blots. Their activities were found to diminish in the DMBA-treated animals as compared to the other groups. Fluorescent co-staining of the isolated broncho-alveolar lavage cells showed reduced number of apoptotic cells in the DMBA group, indicating decrease in apoptosis after carcinogen administration. The present results thus suggest that the mechanism of cancer chemoprevention of NSAIDs may include the suppression of COX-2 and the induction of apoptosis.
New approaches to cancer chemoprevention with difluoromethylornithine and selenite.
Ip C,Thompson H J
Journal of the National Cancer Institute
New approaches to enhancing D,L-alpha-difluoromethylornithine (DFMO) inhibition of DMBA-induced mammary tumorigenesis were investigated. It is reasoned that perturbation of a second regulatory element in polyamine biosynthesis, i.e., the generation of propylamine groups from S-adenosylmethionine (AdoMet), would potentiate the effectiveness of DFMO. Precursor availability for AdoMet was limited when rats were fed a low methionine diet. The diet of control rats was supplemented with 0.3% methionine. DFMO, when added to the diet at 0.1%, suppressed tumorigenesis, regardless of methionine levels, although its efficacy was significantly enhanced by the low methionine diet. Selenite, another effective chemopreventive agent in this tumor model, also requires AdoMet for its metabolism. However, the anticarcinogenic action of selenite is not compromised by low dietary methionine. The differential sensitivity of DFMO and selenium chemoprevention to low dietary methionine, therefore, provides an opportunity to test for an additive effect. Results of the combination regimen study showed that the incidence and yield of DMBA-induced mammary tumors were significantly lower in the two-agent protocol compared to either DFMO or selenite alone. The mechanism(s) that accounts for the heightened efficacy of combined DFMO and selenite chemoprevention will be discussed.
Induction of apoptosis by -gingerol associated with the modulation of p53 and involvement of mitochondrial signaling pathway in B[a]P-induced mouse skin tumorigenesis.
Nigam Nidhi,George Jasmine,Srivastava Smita,Roy Preeti,Bhui Kulpreet,Singh Madhulika,Shukla Yogeshwer
Cancer chemotherapy and pharmacology
PURPOSE:To unravel the molecular mechanisms underlying the chemopreventive potential of -gingerol, a pungent ingredient of ginger rhizome (Zingiber officinale Roscoe, Zingiberaceae), against benzo[a]pyrene (B[a]P)-induced mouse skin tumorigenesis. METHODS:Topical treatment of -gingerol (2.5 muM/animal) was given to the animals 30 min prior and post to B[a]P (5 mug/animal) for 32 weeks. At the end of the study period, the skin tumors/tissues were dissected out and examined histopathologically. Flow cytometry was employed for cell cycle analysis. Further immunohistochemical localization of p53 and regulation of related apoptogenic proteins were determined by Western blotting. RESULTS:Chemopreventive properties of -gingerol were reflected by delay in onset of tumorigenesis, reduced cumulative number of tumors, and reduction in tumor volume. Cell cycle analysis revealed that the appearance of sub-G1 peak was significantly elevated in -gingerol treated animals with post treatment showing higher efficacy in preventing tumorigenesis induced by B[a]P. Moreover, elevated apoptotic propensity was observed in tumor tissues than the corresponding non-tumor tissues. Western blot analysis also showed the same pattern of chemoprevention with -gingerol treatment increasing the B[a]P suppressed p53 levels, also evident by immunohistochemistry, and Bax while decreasing the expression of Bcl-2 and Survivin. Further, -gingerol treatment resulted in release of Cytochrome c, Caspases activation, increase in apoptotic protease-activating factor-1 (Apaf-1) as mechanism of apoptosis induction. CONCLUSIONS:On the basis of the results we conclude that -gingerol possesses apoptotic potential in mouse skin tumors as mechanism of chemoprevention hence deserves further investigation.
D-pinitol mitigates tumor growth by modulating interleukins and hormones and induces apoptosis in rat breast carcinogenesis through inhibition of NF-κB.
Rengarajan Thamaraiselvan,Nandakumar Natarajan,Rajendran Peramaiyan,Ganesh Mohanraj Karthik,Balasubramanian Maruthaiveeran Periyasamy,Nishigaki Ikuo
Journal of physiology and biochemistry
Breast cancer is the most prevalent malignant neoplasm in the world, and chemoprevention through dietary intervention strategy is an emerging option to reduce the incidence. D-pinitol (DP), a major component of soya bean, possesses attractive biological actions. We have investigated whether D-pinitol have an effect on tumor growth in vivo against 7,12-dimethylbenz(a)anthracene (DMBA)-initiated rat mammary carcinogenesis and investigated its mechanism of action. Tumors were induced in Sprague-Dawley (SD) rats by a gastric dose of 20 mg/kg DMBA, and after 13 weeks of induction period, the rats were orally administered with D-pinitol for 45 days. At the end of the assay, animals in carcinogen control group prompted a tumor incidence of 100 % and developed a tumor volume of 8.35 ± 0.56, which was significantly reduced to 5.74 ± 0.32 for the animals treated with D-pinitol. The D-pinitol treatment not only decreased the tumor volume but also further examination revealed that tumors from animals that received D-pinitol reduced nuclear factor kappa B (NF-κB) activation which in turn results in modulation of its downstreaming p53 and proteins of caspase-3 family. Bcl-2 expression and caspase-3 activation were also decreased after D-pinitol supplementation leading to induction of apoptosis and finally cell death. Furthermore, the status of the inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin (IL)-2, IL-6, and tumor markers, lipid profile, and hormones was also significantly declined up on D-pinitol administration. Thus, it reveals the collective involvement of the above-mentioned parameters along with NF-κB signaling through which D-pinitol induces apoptosis and subsequently suppresses breast cancer during DMBA-induced rat breast carcinogenesis.
Chemopreventive effect of a novel oleanane triterpenoid in a chemically induced rodent model of breast cancer.
Bishayee Anupam,Mandal Animesh,Thoppil Roslin J,Darvesh Altaf S,Bhatia Deepak
International journal of cancer
Breast cancer represents one of the most frequently diagnosed cancers and predominant causes of death in women worldwide. The value of preventive therapy to limit the devastating impact of breast cancer is well established. Various plant triterpenoids and their synthetic analogs have shown significant promise as potent chemopreventive agents in breast cancer. The current study was initiated to investigate mechanism-based chemopreventive potential of a novel synthetic oleanane triterpenoid (methyl-25-hydroxy-3-oxoolean-12-en-28-oate, AMR-Me) against 7,12-dimethylbenz(a)anthracene (DMBA)-initiated rat mammary carcinogenesis, an experimental rodent tumor model that closely resembles human mammary cancer. Rats were orally administered with AMR-Me (0.8, 1.2 and 1.6 mg/kg) three times per week for 18 weeks. Following two weeks of AMR-Me treatment, mammary carcinogenesis was initiated by oral administration of DMBA (50 mg/kg body weight). At the end of the study (16 weeks following DMBA exposure), AMR-Me exhibited a striking inhibition of DMBA-induced mammary tumor incidence, total tumor burden, average tumor weight and reversed histopathological alterations without toxicity. AMR-Me dose-dependently suppressed abnormal cell proliferation, induced apoptosis, up-regulated pro-apoptotic protein Bax and down-regulated antiapoptotic protein Bcl-2 in mammary tumors. AMR-Me upregulated the transcriptional levels of Bax, Bad, caspase-3, caspase-7 and poly(ADP-ribose) polymerase and down-regulated Bcl-2. These results clearly demonstrate for the first time that novel triterpenoid AMR-Me exerts chemopreventive efficacy in the classical DMBA model of breast cancer by suppressing abnormal cell proliferation and inducing apoptosis mediated through mitochondrial pro-apoptotic mechanisms. AMR-Me could be developed as a chemopreventive drug to reduce the risk of human breast cancer that remains a devastating disease.
Mitigating role of baicalein on lysosomal enzymes and xenobiotic metabolizing enzyme status during lung carcinogenesis of Swiss albino mice induced by benzo(a)pyrene.
Naveenkumar Chandrashekar,Raghunandakumar Subramanian,Asokkumar Selvamani,Binuclara John,Rajan Balan,Premkumar Thandavamoorthy,Devaki Thiruvengadam
Fundamental & clinical pharmacology
The lungs mainly serve as a primary site for xenobiotic metabolism and constitute an important defense mechanism against inhalation of carcinogens. Our current study aimed to evaluate the chemotherapeutic efficacy of baicalein (BE) in Swiss albino mice exposed to tobacco-specific carcinogen benzo(a)pyrene [B(a)P] for its ability to mitigate pulmonary carcinogenesis. Here, we report that altered activities/levels of lysosomal enzymes (cathepsin-D, cathepsin-B, acid phosphatase, β-D-galactosidase, β-D-glucuronidase, and β-D-N-acetyl glucosaminidase), phase I biotransformation enzymes (cytochrome P450, cytochrome b5, NADPH-cytochrome P450 reductase, and NADH-cytochrome b5 reductase), and phase II enzymes (glutathione S-transferase, UDP-glucuronyl transferase, and DT-diaphorase) were observed in the B(a)P-induced mice. Treatment with BE significantly restored back the activities/levels of lysosomal enzymes, phase I and phase II biotransformation enzymes. Moreover, assessment of lysosomal abnormalities by transmission electron microscopic examination revealed that BE treatment effectively counteract B(a)P-induced oxidative damages. Protein expression levels studied by immunohistochemistry, immunofluorescence, and immunoblot analysis of CYP1A1 revealed that BE treatment effectively negate B(a)P-induced upregulated expression of CYP1A1. Further analysis of scanning electron microscopic studies in lung was carried out to substantiate the anticarcinogenic effect of BE. The overall data suggest that BE treatment significantly inhibits lysosomal and microsomal dysfunction, thus revealing its potent anticarcinogenic effect.
Blueberry inhibits invasion and angiogenesis in 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral squamous cell carcinogenesis in hamsters via suppression of TGF-β and NF-κB signaling pathways.
Baba Abdul Basit,Kowshik Jaganathan,Krishnaraj Jayaraman,Sophia Josephraj,Dixit Madhulika,Nagini Siddavaram
The Journal of nutritional biochemistry
Aberrant activation of oncogenic signaling pathways plays a pivotal role in tumor initiation and progression. The purpose of the present study was to investigate the chemopreventive and therapeutic efficacy of blueberry in the hamster buccal pouch (HBP) carcinogenesis model based on its ability to target TGF-β, PI3K/Akt, MAPK and NF-κB signaling and its impact on invasion and angiogenesis. Squamous cell carcinomas were induced in the HBP by 7,12-dimethylbenz[a]anthracene (DMBA). The effect of blueberry on the oncogenic signaling pathways and downstream events was analyzed by quantitative real-time PCR and immunoblotting. Experiments with the ECV304 cell line were performed to explore the mechanism by which blueberry regulates angiogenesis. Blueberry supplementation inhibited the development and progression of HBP carcinomas by abrogating TGF-β and PI3K/Akt pathways. Although blueberry failed to influence MAPK, it suppressed NF-κB activation by preventing nuclear translocation of NF-κB p65. Blueberry also modulated the expression of the oncomiR miR-21 and the tumor suppressor let-7. Collectively, these changes induced a shift to an anti-invasive and anti-angiogenic phenotype as evidenced by downregulating matrix metalloproteinases and vascular endothelial growth factor. Blueberry also inhibited angiogenesis in ECV304 cells by suppressing migration and tube formation. The results of the present study suggest that targeting oncogenic signaling pathways that influence acquisition of cancer hallmarks is an effective strategy for chemointervention. Identification of modulatory effects on phosphorylation, intracellular localization of oncogenic transcription factors and microRNAs unraveled by the present study as key mechanisms of action of blueberry is critical from a therapeutic perspective.
Polymeric black tea polyphenols (PBPs) inhibit benzo(a)pyrene and 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone-induced lung carcinogenesis potentially through down-regulation of p38 and Akt phosphorylation in A/J mice.
Hudlikar Rasika R,Venkadakrishnan Varadha Balaji,Kumar Rajiv,Thorat Rahul A,Kannan Sadhana,Ingle Arvind D,Desai Saral,Maru Girish B,Mahimkar Manoj B
The aim of our study was to evaluate chemopreventive efficacy and possible mechanism of most abundant polyphenolic fraction in black tea, polymeric black tea polyphenols (PBPs), in experimental lung carcinogenesis model. Effect of 1.5% black tea derived PBPs on benzo(a)pyrene [B(a)P] and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced lung lesions were studied over 28 wks. Chemopreventive efficacy was studied using decrease in tumor incidence and/or multiplicity and/or delay in the latency period in A/J mice. Histopathological analysis of lung was carried out post-carcinogen treatment weeks to analyze the microscopic lung lesions. Inflammation, cell proliferation, and apoptosis markers along with signaling kinases like p38, Akt, and their phosphorylated forms were studied using immunoblotting and immunohistochemistry at 4th, 10th, and 18th wk post-carcinogen treatment. Administration of PBPs throughout the treatment period significantly decreased the multiplicity of surface tumors as well as microscopic lung lesions, including adenomas. Although tumor incidence and latency period remains unaffected, histopathological evaluation of lung at 6, 10, and 18 wks post- carcinogen treatment period showed decrease in tumor multiplicity which was also correlated with different molecular markers. Anti- inflammatory action of PBPs was demonstrated by reduced Cox-2 expression. PBPs down-regulated the B(a)P and NNK-induced cell proliferation (diminished PCNA expression, proliferation index, and Bcl-2 expression) and enhanced apoptosis (increased Bax expression and apoptotic index) potentially through phosphorylation of p38 and Akt. PBPs, most abundant polyphenolic component in the black tea, have chemopreventive effect through inhibition of inflammation, cellular proliferation, and induction of apoptosis possibly via modulation of signaling kinases. © 2016 Wiley Periodicals, Inc.
Inhibition of carcinogen induced activity of gamma-glutamyl transpeptidase by certain dietary constituents in mouse skin.
Shukla Y,Singh A,Srivastava B
Biomedical and environmental sciences : BES
Cancer chemoprevention, a desirable and important facet of biomedical research, provides a practical approach to identify potentially useful inhibitors of cancer development, and offers an opportunity to study the mechanism of carcinogenesis. During the recent past a number of compounds have been tested for their anticarcinogenic potential specially constituents of our diet. The enzyme gamma-glutamyl transpeptidase (GGT) which catalyses the transfer of glutamyl groups of peptides to other peptides and amino acid and has been proposed as a marker of cell proliferation and neoplasia. It also serves as a tool to evaluate the carcinogenic and cocarcinogenic potential of environmental toxicants. In the present investigations, GGT activity induced by carcinogenic polycyclic aromatic hydrocarbons, viz. 7,12-dimethylbenz(a)anthracene (DMBA) and benzo(a) pyrene (BaP) was significantly inhibited by diallylsulfide (DAS) and indole-3-carbinol (I3C) in mouse skin. DAS and I3C are constituents of garlic and cruciferous vegetables respectively. A significant inhibition in GGT levels was also observed in a strong mitogen (12-o-tetradecanoyl phorbol-13-acetate) induced activity in mouse skin by pretreatment with DAS/I3C. Therefore these dietary constituents seem to be strong modifiers of chemically induced carcinogenesis.
Chemopreventive activities of Trigonella foenum graecum (Fenugreek) against breast cancer.
Amin Amr,Alkaabi Aysha,Al-Falasi Shamaa,Daoud Sayel A
Cell biology international
Cancer is the second leading cause of death worldwide. Conventional therapies cause serious side effects and, at best, merely extend the patient's lifespan by a few years. Cancer control may therefore benefit from the potential that resides in alternative therapies. There is thus an increasing demand to utilize alternative concepts or approaches to the prevention of cancer. In this report, we show a potential protective effect of Fenugreek seeds against 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced breast cancer in rats. At 200 mg/kg b.wt., Fenugreek seeds' extract significantly inhibited the DMBA-induced mammary hyperplasia and decreased its incidence. Epidemiological studies also implicate apoptosis as a mechanism that might mediate the Fenugreek's anti-breast cancer protective effects. To our knowledge, this is the first study that suggests significant chemopreventive effects of Fenugreek seeds against breast cancer.
Studies of the mechanism by which increased spermidine/spermine N1-acetyltransferase activity increases susceptibility to skin carcinogenesis.
Wang Xiaojing,Feith David J,Welsh Pat,Coleman Catherine S,Lopez Christina,Woster Patrick M,O'Brien Thomas G,Pegg Anthony E
Previous studies have shown that keratin 6 (K6)-spermidine/spermine N1-acetyltransferase (SSAT) transgenic mice, which modestly over-express SSAT in the skin, are more sensitive to tumor induction by a two-stage tumorigenesis protocol using initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). To evaluate the role of altered levels of polyamines and oxidative stress in this increase, studies were carried out with pharmacologic and genetic manipulation of K6-SSAT mice subjected to DMBA/TPA carcinogenesis. The increased tumor incidence was partially prevented by treatment with 1,4-bis-[N-(buta-2,3-dienyl)amino]butane, an inhibitor of acetylpolyamine oxidase which prevented degradation of the acetylated polyamines. This result suggests that toxic products such as reactive oxygen species and aldehydes liberated by the action of polyamine oxidase on the acetylated polyamines formed by SSAT may enhance tumor development. Breeding of the K6-SSAT mice with K6-antizyme (AZ) mice [which express AZ, a negative regulator of ornithine decarboxylase (ODC)] blocked the development of tumors. In addition, treatment of tumor-bearing K6-SSAT mice with the ODC inhibitor, alpha-difluoromethylornithine, resulted in the complete regression of established tumors. In contrast, treatment with N1,N11-bis(ethyl)norspermidine which increased SSAT activity in the tumors did not enhance regression. These results indicate that the tumor progression in K6-SSAT mice is dependent on elevated ODC activity and increased putrescine levels and may be further enhanced by oxidative stress. They support the use of strategies to modulate polyamine levels through the inhibition of ODC activity or polyamine uptake, but not via increased SSAT expression, for cancer chemoprevention in individuals at high risk for skin tumor development.
Chemopreventive effect of syringic acid on 7,12-dimethylbenz(a)anthracene induced hamster buccal pouch carcinogenesis.
Velu Periyannan,Vinothkumar Veerasamy,Babukumar Sukumar,Ramachandhiran Duraisamy
Toxicology mechanisms and methods
Oral squamous cell carcinoma is most prevalent and refractory cancers worldwide. Recently, chemoprevention could be a promising approach in developing countries. The present study investigates the mechanism of syringic acid (SA), a phenolic constituent of plant Alpiniacalcarata Roscoe, and their leaves are used as traditional Indian Ayurveda medicines, mediated chemoprevention on 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis (HBPC). Lipid peroxidation and antioxidants were measured in the plasma and buccal tissues in experimental hamsters. Modulating effect of SA on the expression pattern of PCNA, Cyclin D1, and mutant p53 markers was used for immunoexpression and western blotting analysis. In the present study, 100% tumor formation with marked abnormalities in the biochemical parameters of lipid peroxidation and antioxidants through up-regulation of molecular markers like PCNA, Cyclin D1, and mutant p53 was accompanied with tumor-bearing hamsters. Oral administration of SA at the doses of 50 and 100 mg/kg body weight (bw) to DMBA-treated hamsters significantly inhibited adverse changes in the biochemical parameters of the plasma and buccal mucosal tissues and also down-regulation of molecular marker expression (PCNA, Cyclin D1, and mutant p53). The present study thus suggests that SA has potent anti-lipid peroxidative, antioxidant, anti-cell proliferative, and apoptosis-inducing properties during DMBA-induced HBPC.
Antiproliferative and antioxidant potential of hesperetin against benzo(a)pyrene-induced lung carcinogenesis in Swiss albino mice.
Bodduluru Lakshmi Narendra,Kasala Eshvendar Reddy,Barua Chandana C,Karnam Kalyani Chowdary,Dahiya Vicky,Ellutla Maheswara
Lung cancer is the foremost cause of cancer mortality and is a growing economic burden worldwide. Chemoprevention, employing the use of natural, dietary or synthetic agents has become an appealing strategy to combat the increasing cases of cancers worldwide. The present study was designed to investigate the mechanism-based chemopreventive nature of hesperetin (HSP) against B[a]P induced lung carcinogenesis in Swiss albino mice. We analyzed the chemopreventive potential of HSP by estimating the status of lipid peroxidation (LPO), enzymic (SOD, CAT, GPx, GR, and GST), nonenzymic antioxidants (GSH, Vit C and Vit E), proinflammatory cytokine (TNF-α), western blotting (CYP1A1, PCNA, Nrf2 and NF-κB expression) and histopathology of lung tissues of control and experimental mice. Administration of B[a]P (50 mg/kg, p.o.) resulted in an increase in lung weight, LPO with concomitant decrease in body weight, enzymic (SOD, CAT, GPx, GR, and GST) and non-enzymic (GSH, Vit C and Vit E) antioxidants. Histological examination of lungs revealed severe alveolar and bronchiolar damages in B[a]P-induced mice. Further, elevated levels of TNF-α along with activated expression of NF-κB, PCNA and CYP1A1, and downregulation of Nrf2 was observed in B[a]P intoxicated animals. Pre- and post-treatment with HSP effectively suppressed B[a]P induced lung carcinoma and the associated preneoplastic lesions by alleviating LPO, modulating antioxidants and decreasing the expression of NF-κB, PCNA and CYP1A1. These findings demonstrate that HSP possesses a potential chemopreventive activity against B[a]P induced lung cancer and this is attributed to its free radical scavenging, antioxidant, anti-inflammatory and antiproliferative properties.
Anti-Inflammatory Mechanism Involved in Pomegranate-Mediated Prevention of Breast Cancer: the Role of NF-κB and Nrf2 Signaling Pathways.
Mandal Animesh,Bhatia Deepak,Bishayee Anupam
Pomegranate ( L.), a nutrient-rich unique fruit, has been used for centuries for the prevention and treatment of various inflammation-driven diseases. Based on our previous study, a characterized pomegranate emulsion (PE) exhibited a striking inhibition of dimethylbenz(a)anthracene (DMBA)-initiated rat mammary tumorigenesis via antiproliferative and apoptosis-inducing mechanisms. The objective of the present work is to investigate the anti-inflammatory mechanism of action of PE during DMBA rat mammary carcinogenesis by evaluating the expression of cyclooxygenase-2 (COX-2), heat shock protein 90 (HSP90), nuclear factor-κB (NF-κB) and nuclear factor erythroid 2p45 (NF-E2)-related factor 2 (Nrf2). Mammary tumor samples were harvested from our previous chemopreventive study in which PE (0.2-5.0 g/kg) was found to reduce mammary tumorigenesis in a dose-dependent manner. The expressions of COX-2, HSP90, NF-κB, inhibitory κBα (IκBα) and Nrf2 were detected by immunohistochemical techniques. PE decreased the expression of COX-2 and HSP90, prevented the degradation of IκBα, hindered the translocation of NF-κB from cytosol to nucleus and increased the expression and nuclear translocation of Nrf2 during DMBA-induced mammary tumorigenesis. These findings, together with our previous results, indicate that PE-mediated prevention of DMBA-evoked mammary carcinogenesis may involve anti-inflammatory mechanisms through concurrent but differential regulation of two interrelated molecular pathways, namely NF-κB and Nrf2 signaling.
In vitro and in vivo studies of methylseleninic acid: evidence that a monomethylated selenium metabolite is critical for cancer chemoprevention.
Ip C,Thompson H J,Zhu Z,Ganther H E
Previous research suggested that the beta-lyase-mediated production of a monomethylated selenium metabolite from Se-methylselenocysteine is a key step in cancer chemoprevention by this agent. In an attempt to affirm the concept, the present study was designed to evaluate the activity of methylseleninic acid, a compound that represents a simplified version of Se-methylselenocysteine without the amino acid moiety, thereby obviating the need for beta-lyase action. The in vitro experiments showed that methylseleninic acid was more potent than Se-methylselenocysteine in inhibiting cell accumulation and inducing apoptosis in TM12 (wild-type p53) and TM2H (nonfunctional p53) mouse mammary hyperplastic epithelial cells, and these effects were not attributable to DNA damage, as determined by the comet assay. In general, methylseleninic acid produced a more robust response at one-tenth the concentration of Se-methylselenocysteine. It is possible that these cell lines may have only a modest ability to generate a monomethylated selenium species from Se-methylselenocysteine via the beta-lyase enzyme. In contrast, methylseleninic acid already serves as a preformed active monomethylated metabolite, and this could be an underlying reason why methylseleninic acid acts more rapidly and exerts a more powerful effect than Se-methylselenocysteine in vitro. Interestingly, the distinction between these two compounds disappeared in vivo, where their cancer chemopreventive efficacies were found to be very similar to each other [in both methylnitrosourea and dimethylbenz(a)anthracene rat mammary tumor models]. The beta-lyase enzyme is present in many tissues; thus, animals have an ample capacity to metabolize Se-methylselenocysteine systemically. Therefore, Se-methylselenocysteine would be expected to behave like methylseleninic acid if beta-lyase is no longer a limiting factor. Taken together, the present in vitro and in vivo results provide strong evidence in support of our earlier hypothesis that a monomethylated selenium metabolite is important for cancer chemoprevention. Methylseleninic acid could be an excellent tool, especially for molecular mechanism studies in cell culture, and some of these attributes are discussed.
Chemopreventive effect of farnesol on DMBA/TPA-induced skin tumorigenesis: involvement of inflammation, Ras-ERK pathway and apoptosis.
Chaudhary Sandeep Chand,Alam Mohammad Sarwar,Siddiqui Mohammad Saeed,Athar Mohammad
AIMS:Naturally-derived farnesol has been reported for its chemopreventive and chemotherapeutic efficacy in various cancers. However, the mechanism of action of farnesol is still to be elucidated. The present study demonstrates the chemopreventive potential of farnesol on 9,10-dimethylbenz(a)anthracene (DMBA)-initiated and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumorigenesis in Swiss albino mice. MAIN METHODS:Farnesol at three different doses 25, 50 and 100 mg/kg body weight was topically applied to the mouse skin, 30 min prior to TPA (2 microg/200 microl acetone) to evaluate edema, hyperplasia, expression of cyclooxygenase-2 (COX-2), oxidative stress response and hyperproliferation, and expression of Ras, Raf, p-ERK1/2, Bax and Bcl-2 in DMBA/TPA-induced tumors. KEY FINDINGS:Farnesol at both the low doses significantly reduced the TPA-induced skin edema, hyperplasia, expression of COX-2 and oxidative stress response. Interestingly, higher dose of farnesol did not show any significant response. Pretreatment of farnesol significantly decreased TPA-induced ornithine decarboxylase (ODC) activity and [(3)H]thymidine incorporation in dose-dependent manner. During promotion phase, farnesol with higher dose significantly regressed tumor incidence and tumor burden with an extension of latency period of 4-8 weeks. More importantly, low doses of farnesol significantly inhibited Ras/Raf/ERK1/2 signaling pathway in mouse skin tumors whereas higher dose of farnesol induced the pathway. Moreover, farnesol at all doses altered Bax/Bcl-2 ratio which leads to induction of apoptosis as confirmed by DNA fragmentation. SIGNIFICANCE:These findings revealed that oxidative stress, inflammation, Ras/Raf/ERK1/2 pathway and apoptosis collectively played a crucial role in the chemopreventive activity of farnesol to inhibit the murine skin tumorigenesis.
Inhibition of carcinogen-induced activity of gamma-glutamyl transpeptidase by certain dietary constituents in mouse skin.
Shukla Y,Singh A,Srivastava B
Biomedical and environmental sciences : BES
Cancer chemoprevention, a desirable and important facet of biomedical research, provides a practical approach to identify potentially useful inhibitors of cancer development, and offers an opportunity to study the mechanism of carcinogenesis. During the recent past a number of compounds have been tested for their anticarcinogenic potential specially constituents of human diet. The enzyme gamma-glutamyl transpeptidase (GGT), which catalyses the transfer of glutamyl groups of peptides to other peptides and amino acids, has been proposed as a marker of cell proliferation and neoplasia. It also serves as a tool to evaluate the carcinogenic and cocarcinogenic potential of environmental toxicants. In the present investigations, GGT activity induced by carcinogenic polycyclic aromatic hydrocarbons, viz. 7,12-dimethyl-benz(a)anthracene (DMBA) and benzo(a)pyrene (BaP) was significantly inhibited by diallylsulfide (DAS) and indole-3-carbinol (I3C) in mouse skin. DAS and I3C are constituents of garlic. A significant inhibition in GGT levels was also observed in a strong mitogen (12-o-tetradecanoyl phorbol-13-acetate) induced activity by pretreatment of DAS/I3C in mouse skin. Therefore these dietary constituents seem to be strong modifiers of chemically induced carcinogenesis.
Chemopreventive potential of apigenin in 7,12-dimethylbenz(a)anthracene induced experimental oral carcinogenesis.
Silvan Simon,Manoharan Shanmugam,Baskaran Nagarethinam,Anusuya Chezhiyan,Karthikeyan Sekar,Prabhakar Murugaraj Manoj
European journal of pharmacology
Aim was to investigate the chemopreventive potential of apigenin by analyzing the tumor incidence as well as monitoring lipid peroxidation, antioxidants and phase I and phase II detoxification as biomarkers during DMBA induced hamster buccal pouch carcinogenesis. Oral tumors were developed in the buccal pouches of golden Syrian hamsters using topical application of 0.5% DMBA (DMBA) three times a week for 14weeks. Tumor incidence, tumor volume and burden were measured in hamsters treated with 7,12-dimethylbenz(a)anthracene and DMBA+apigenin (2.5mg/kg body weight) treated hamsters. Oral administration of apigenin not only completely prevented the formation of oral tumors, it also brought back the status of lipid peroxidation, antioxidants and phase I and phase II detoxification agents to near normal range during DMBA induced oral carcinogenesis. The present study thus concludes that apigenin might have inhibited oral carcinogenesis by improving the status of antioxidant defense mechanism and modulated the activities of phase I and phase II detoxification cascade toward increased excretion of active metabolite of DMBA, during DMBA induced hamster buccal pouch carcinogenesis.
Chemoprevention by Hippophae rhamnoides: effects on tumorigenesis, phase II and antioxidant enzymes, and IRF-1 transcription factor.
Padmavathi Bandhuvula,Upreti Meenakshi,Singh Virendra,Rao A Ramesha,Singh Rana P,Rath Pramod C
Nutrition and cancer
Fruits or berries of Hippophae rhamnoides (sea buckthorn), a rich source of vitamins A, C, and E, carotenes, flavonoids, and microelements such as sulfur, selenium, zinc, and copper, are edible and have been shown to protect from atopic dermatitis, hepatic injury, cardiac disease, ulcer, and atherosclerosis. However, its mechanism of action is not clear. We show that Hippophae inhibits benzo(a)pyrene-induced forestomach and DMBA-induced skin papillomagenesis in mouse. This decrease in carcinogenesis may be attributed to the concomitant induction of phase II enzymes such as glutathione S-transferase and DT-diaphorase and antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in the mouse liver. This was accompanied by a remarkable induction of the transcription factor interferon regulatory factor-1 in the Hippophae-treated liver. Our results strongly suggest that Hippophae fruit is able to decrease carcinogen-induced forestomach and skin tumorigenesis, which might involve up-regulation of phase II and antioxidant enzymes as well as DNA-binding activity of IRF-1, a known antioncogenic transcription factor causing growth suppression and apoptosis induction for its anticancer effect.
Isoflavone-deprived soy peptide suppresses mammary tumorigenesis by inducing apoptosis.
Park Kyoungsook,Choi Kyusam,Kim Hyemee,Kim Kwangbae,Lee Mi Hee,Lee Je Ho,Kim Rim Jean Chinock
Experimental & molecular medicine
During carcinogenesis, NF-gammaB mediates processes associated with deregulation of the normal control of proliferation, angiogenesis, and metastasis. Thus, suppression of NF-gammaB has been linked with chemoprevention of cancer. Accumulating findings reveal that heat shock protein 90 (HSP90) is a molecular chaperone and a component of the IgammaB kinase (IKK) complex that plays a central role in NF-gammaB activation. HSP90 also stabilizes key proteins involved in cell cycle control and apoptosis signaling. We have determined whether the exogenous administration of isoflavone-deprived soy peptide prevents 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced rat mammary tumorigenesis and investigated the mechanism of action. Dietary administration of soy peptide (3.3 g/rat/day) significantly reduced the incidence of ductal carcinomas (50%), the number of tumors per multiple tumor-bearing rats (49%; P<0.05), and extended the latency period of tumor development (8.07+/-0.92 weeks) compared to control diet animals (10.80+/-1.30; P<0.05). Our results have further demonstrated that soy peptide (1) dramatically inhibits the expression of HSP90, thereby suppressing signaling pathway leading to NF-gammaB activation; (2) induces expression of p21, p53, and caspase-3 proteins; and (3) inhibits expression of VEGF. In agreement with our in vivo data, soy peptide treatment inhibited the growth of human breast MCF-7 tumor cells in a dose-dependent manner and induced apoptosis. Taken together, our in vivo and in vitro results suggest chemopreventive and tumor suppressive functions of isoflavone-deprived soy peptide by inducing growth arrest and apoptosis.
Chemopreventive effect of kava on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone plus benzo[a]pyrene-induced lung tumorigenesis in A/J mice.
Johnson Thomas E,Kassie Fekadu,O'Sullivan M Gerard,Negia Mesfin,Hanson Timothy E,Upadhyaya Pramod,Ruvolo Peter P,Hecht Stephen S,Xing Chengguo
Cancer prevention research (Philadelphia, Pa.)
Lung cancer is the leading cause of cancer death, and chemoprevention is a potential strategy to help control this disease. Epidemiologic survey indicates that kava may be chemopreventive for lung cancer, but there is a concern about its potential hepatotoxicity. In this study, we evaluated whether oral kava could prevent 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) plus benzo[a]pyrene (B[a]P)-induced lung tumorigenesis in A/J mice. We also studied the effect of kava to liver. At a dose of 10 mg/g diet, 30-week kava treatment (8 weeks concurrent with NNK and B[a]P treatment followed by 22 weeks post-carcinogen treatment) effectively reduced lung tumor multiplicity by 56%. Kava also reduced lung tumor multiplicity by 47% when administered concurrently with NNK and B[a]P for 8 weeks. Perhaps most importantly, kava reduced lung tumor multiplicity by 49% when administered after the final NNK and B[a]P treatment. These results show for the first time the chemopreventive potential of kava against lung tumorigenesis. Mechanistically, kava inhibited proliferation and enhanced apoptosis in lung tumors, as shown by a reduction in proliferating cell nuclear antigen (PCNA), an increase in caspase-3, and cleavage of poly(ADP-ribose) polymerase (PARP). Kava treatment also inhibited the activation of nuclear factor kappaBNF-kappaB, a potential upstream mechanism of kava chemoprevention. Although not rigorously evaluated in this study, our preliminary data were not suggestive of hepatotoxicity. Based on these results, further studies are warranted to explore the chemopreventive potential and safety of kava.
Prevention of carcinogen and inflammation-induced dermal cancer by oral rapamycin includes reducing genetic damage.
Dao Vinh,Pandeswara Srilakshmi,Liu Yang,Hurez Vincent,Dodds Sherry,Callaway Danielle,Liu Aijie,Hasty Paul,Sharp Zelton D,Curiel Tyler J
Cancer prevention research (Philadelphia, Pa.)
Cancer prevention is a cost-effective alternative to treatment. In mice, the mTOR inhibitor rapamycin prevents distinct spontaneous, noninflammatory cancers, making it a candidate broad-spectrum cancer prevention agent. We now show that oral microencapsulated rapamycin (eRapa) prevents skin cancer in dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) carcinogen-induced, inflammation-driven carcinogenesis. eRapa given before DMBA/TPA exposure significantly increased tumor latency, reduced papilloma prevalence and numbers, and completely inhibited malignant degeneration into squamous cell carcinoma. Rapamycin is primarily an mTORC1-specific inhibitor, but eRapa did not reduce mTORC1 signaling in skin or papillomas, and did not reduce important proinflammatory factors in this model, including p-Stat3, IL17A, IL23, IL12, IL1β, IL6, or TNFα. In support of lack of mTORC1 inhibition, eRapa did not reduce numbers or proliferation of CD45(-)CD34(+)CD49f(mid) skin cancer initiating stem cells in vivo and marginally reduced epidermal hyperplasia. Interestingly, eRapa reduced DMBA/TPA-induced skin DNA damage and the hras codon 61 mutation that specifically drives carcinogenesis in this model, suggesting reduction of DNA damage as a cancer prevention mechanism. In support, cancer prevention and DNA damage reduction effects were lost when eRapa was given after DMBA-induced DNA damage in vivo. eRapa afforded picomolar concentrations of rapamycin in skin of DMBA/TPA-exposed mice, concentrations that also reduced DMBA-induced DNA damage in mouse and human fibroblasts in vitro. Thus, we have identified DNA damage reduction as a novel mechanism by which rapamycin can prevent cancer, which could lay the foundation for its use as a cancer prevention agent in selected human populations.
Identifying efficacious approaches to chemoprevention with chlorophyllin, purified chlorophylls and freeze-dried spinach in a mouse model of transplacental carcinogenesis.
Castro David J,Löhr Christiane V,Fischer Kay A,Waters Katrina M,Webb-Robertson Bobbie-Jo M,Dashwood Roderick H,Bailey George S,Williams David E
The carcinogenic potential of dibenzo[a,l]pyrene (DBP) has been well characterized in numerous animal models. We have previously documented that a single dose of 15 mg/Kg DBP to pregnant mice late in gestation (GD 17) produces an aggressive T-cell lymphoma as well as lung and liver cancer in offspring. The current study examines the chemopreventative properties of chlorophyllin (CHL) and chlorophyll (Chl) in this transplacental carcinogenesis model. Pregnant B6129SF1 females, bred to 129S1/SvIm males, received purified diets incorporated with either 2000 p.p.m. CHL, 2000 p.p.m. Chl or 10% freeze-dried spinach beginning at gestation day 9. Lymphoma-dependent mortality was not significantly altered by maternal consumption of any of the diet and little effect on lung tumor burden in mice surviving to 10 months of age was observed. However, coadministration of CHL at 380 mg/Kg with DBP by gavage (molar ratio of 10:1, CHL:DBP) provided significant protection against DBP-initiated carcinogenesis. Offspring born to dams receiving CHL co-gavaged with DBP exhibited markedly less lymphoma-dependent mortality (P < 0.001). The degree of protection by CHL, compared with controls dosed with DBP in tricaprylin (TCP) as the vehicle, was less marked, but still significant. Coadministration of CHL (TCP as vehicle) also reduced lung tumor multiplicity in mice by approximately 50% and this was observed throughout the study (P < 0.005). This is the first demonstration that CHL can provide potent chemoprotection in a transplacental carcinogenesis model and support a mechanism involving complex-mediated reduction of carcinogen uptake.
Low dose triterpene-quinone fraction from Ardisia crispa root precludes chemical-induced mouse skin tumor promotion.
Yeong Looi Ting,Abdul Hamid Roslida,Saiful Yazan Latifah,Khaza'ai Huzwah,Mohtarrudin Norhafizah
BMC complementary and alternative medicine
BACKGROUND:Drastic increment of skin cancer incidence has driven natural product-based chemoprevention as a promising approach in anticancer drug development. Apart from its traditional usages against various ailments, Ardisia crispa (Family: Myrsinaceae) specifically its triterpene-quinone fraction (TQF) which was isolated from the root hexane extract (ACRH) was recently reported to exert antitumor promoting activity in vitro. This study aimed at determining chemopreventive effect of TQF against chemically-induced mouse skin tumorigenesis as well as elucidating its possible pathway(s). METHODS:Mice (n = 10) were initiated with single dose of 7,12-dimethylbenz[α]anthracene (DMBA) (390 nmol/100 μl) followed by, a week later, repeated promotion (twice weekly; 20 weeks) with 12-O-tetradecanoylphorbol-13-acetate (TPA) (1.7 nmol/100 μl). TQF (10, 30 and 100 mg/kg) and curcumin (10 mg/kg; reference) were, respectively, applied topically to DMBA/TPA-induced mice 30 min before each TPA application. Upon termination, histopathological and biochemical analysis, as well as Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and transcription factor enzyme-linked immunosorbent assay (ELISA) assays were performed to elucidate the potential mechanism of TQF. RESULTS:With comparison to the carcinogen control, results revealed that lower dose of TQF (10 mg/kg) conferred antitumor promoting effect via significant (P < 0.05) suppression against lipid peroxidation (LPO), apoptotic index (cell death) and nuclear factor-kappa B (NF-κB), along with reduction of keratinocyte proliferation; whilst its higher dose (100 mg/kg) was found to promote tumorigenesis by significantly (P < 0.05) increasing LPO and apoptotic index, in addition to aggravating keratinocyte proliferation. CONCLUSIONS:This study evidenced that TQF, particularly at its lower dosage (10 mg/kg), ameliorated DMBA/TPA-induced mouse skin tumorigenesis. Though, future investigations are warranted to determine the lowest possible therapeutic dose of TQF in subsequent in vivo chemopreventive studies.
Effects of cruciferous vegetables and their constituents on drug metabolizing enzymes involved in the bioactivation of DNA-reactive dietary carcinogens.
Steinkellner H,Rabot S,Freywald C,Nobis E,Scharf G,Chabicovsky M,Knasmüller S,Kassie F
Epidemiological studies give evidence that cruciferous vegetables (CF) protect humans against cancer, and also results from animal experiments show that they reduce chemically induced tumor formation. These properties have been attributed to alterations in the metabolism of carcinogens by breakdown products of glucosinolates, which are constituents of CF. The present article gives an overview on the present state of knowledge on the impact of CF and their constituents on enzymes that are involved in the metabolism of DNA-reactive carcinogens. The development of in vitro models with metabolically competent cell lines led to the detection of potent enzyme inducers contained in CF such as sulforaphane. Recently, we showed that Brassica juices induce glutathione-S-transferases (GST) and cytochrome P-450 1A2 in human hepatoma cells (HepG2) and protect against the genotoxic effects of B(a)P and other carcinogens. Earlier in vivo experiments with rodents indicated that indoles and isothiocyanates, two major groups of glucosinolate breakdown products, attenuate the effects of polycyclic aromatic hydrocarbons (PAHs) and nitrosamines via induction of GST and inhibition of cytochrome-P450 isoenzymes, respectively. Our own investigations showed that CF are also protective towards heterocyclic amines (HAs): Brussels sprouts- and garden cress juices attenuated IQ-induced DNA-damage and preneoplastic lesions in colon and liver of rats. These effects were paralleled by induction of uridine-di-phospho-glucuronosyl transferase (UDPGT) which is very probably the mechanism of protection against HAs by cruciferous vegetables. There is also evidence that consumption of CF might protect humans against cancer. In matched control intervention studies with these vegetables, it was shown that they induce GST-activities in humans but overall, results were inconclusive. Recently, we carried out crossover intervention studies and found pronounced GST-induction upon consumption of Brussels sprouts and red cabbage, whereas no effects were seen with white cabbage and broccoli. Furthermore, we found that the isoenzyme induced was GST-pi which plays an important role in protection against breast, bladder, colon and testicular cancer. No induction of the GST-alpha isoform could be detected. Urinary mutagenicity experiments gave further evidence that CF affect drug metabolism in humans. Consumption of red cabbage led to changes in the pattern of meat-derived urinary mutagenicity. Overall, CF are among the most promising chemopreventive dietary constituents and further elucidation of their protective mechanisms and the identification of active constituents may contribute to the development of highly protective Brassica varieties.
Benzo[a]pyrene-induced cytochrome P450 1A and DNA binding in cultured trout hepatocytes - inhibition by plant polyphenols.
Tsuji Petra A,Walle Thomas
Polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene (BaP) mainly induce lung cancer in humans, but induce liver cancer in fishes. The chemoprevention of cancers through inhibition of molecular events via phytochemicals is a potentially beneficial area of research, and has been carried out in human cell cultures in the past. Carcinogenesis initiation events are thought to occur in similar ways in fish and humans. Our study investigated the feasibility of using cultured rainbow trout CRL-2301 liver cells as a model for BaP-induced carcinogenesis and its prevention by dietary phytochemicals. Treatment with 1 microM BaP resulted in extensive time-dependent covalent binding to cellular DNA and marked cytochrome P450 (CYP) 1A induction, for both about a 20-fold increase, which is similar to what has been observed in cultured human cells. A surprisingly high expression of epoxide hydrolase (EH) activity in these cells likely contributed substantially to the bioactivation of BaP. Two methoxylated flavones and the stilbene resveratrol were effective inhibitors of both the BaP-DNA binding and CYP 1A induction, in particular 5,7-dimethoxyflavone (5,7-DMF), supporting a role for these dietary compounds as cancer chemopreventive agents. Unlike in human liver or bronchial cells, the main mechanism of inhibition of BaP-induced CYP 1A activity in trout liver cells appears to be direct competition at the protein level. Different cellular responses in any particular model used can be expected and the effect of cell context on the biological responses to xenobiotics, including carcinogens as well as polyphenols, must be considered. The trout CRL-2301 cells' sensitivity to BaP treatment is a clear advantage when contemplating a model system for studies of PAH-induced carcinogenesis and cancer chemoprevention. However, extrapolation to human organs should be done cautiously.
Mechanism of Breast Cancer Preventive Action of Pomegranate: Disruption of Estrogen Receptor and Wnt/β-Catenin Signaling Pathways.
Mandal Animesh,Bishayee Anupam
Molecules (Basel, Switzerland)
A pomegranate emulsion (PE), containing various bioactive phytochemicals, has recently been found to exert substantial chemopreventive effect against 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumorigenesis in rats via antiproliferative and proapoptotic actions. Nevertheless, the underlying mechanisms of action are not completely understood. The present study was designed to investigate the effects of PE treatment on intratumor expression of estrogen receptor (ER)-α, ER-β,β-catenin and cyclin D1 during DMBA rat mammary carcinogenesis. Mammary tumor sections were harvested from a chemopreventive study in which PE (0.2, 1.0 and 5.0 g/kg) exhibited inhibition of mammary tumorigenesis in a dose-response manner. The expressions of ER-α, ER-β, β-catenin and cyclin D1 were analyzed by immunohistochemical techniques. PE downregulated the expression of intratumor ER-α and ER-β and lowered ER-α:ER-β ratio. PE also decreased the expression, cytoplasmic accumulation, and nuclear translocation of β-catenin, an essential transcriptional cofactor for Wnt signaling. Moreover, PE suppressed the expression of cell growth regulatory protein cyclin D1, which is a downstream target for both ER and Wnt signaling. Our current results in conjunction with our previous findings indicate that concurrent disruption of ER and Wnt/β-catenin signaling pathways possibly contributes to antiproliferative and proapoptotic effects involved in PE-mediated chemoprevention of DMBA-inflicted rat mammary tumorigenesis.
Trianthema portulacastrum Linn. exerts chemoprevention of 7,12-dimethylbenz(a)anthracene-induced mammary tumorigenesis in rats.
Bishayee Anupam,Mandal Animesh
Due to limited treatment options for advanced-stage metastatic breast cancer, a high priority should be given to develop non-toxic chemopreventive drugs. The value of various natural and dietary agents to reduce the risk of developing breast cancer is well established. Trianthema portulacastrum Linn. (Aizoaceae), a dietary and medicinal plant, has been found to exert antihepatotoxic and antihepatocarcinogenic properties in rodents. This study was initiated to investigate mechanism-based chemopreventive potential of an ethanolic extract of T. portulacastrum (TPE) against 7,12-dimethylbenz(a)anthracene (DMBA)-initiated rat mammary gland carcinogenesis, an experimental tumor model that closely resembles human breast cancer. Rats had access to a basal diet supplemented with TPE to yield three dietary doses of the extract, i.e., 50, 100 and 200 mg/kg body weight. Following two weeks of TPE treatment, mammary tumorigenesis was initiated by oral administration of DMBA (50 mg/kg body weight). At the end of the study (16 weeks after DMBA exposure), TPE exhibited a striking reduction of DMBA-induced mammary tumor incidence, total tumor burden and average tumor weight and reversed intratumor histopathological alterations. TPE dose-dependently suppressed proliferating cell nuclear antigen and cyclin D1 expression, induced apoptosis, upregulated proapoptotic protein Bax, downregulated antiapoptotic protein Bcl-2 and diminished the expression of nuclear and cytosolic β-catenin in mammary tumors. Our results clearly provide the first experimental evidence that TPE exerts chemopreventive effect in the classical DMBA model of breast cancer by suppressing abnormal cell proliferation and inducing apoptosis mediated through alteration of Bax/Bcl-2 ratio. Mechanistically, TPE is capable of diminishing activated canonical Wnt/β-catenin signaling to exhibit antiproliferative, proapoptotic and oncostatic effects during an early-stage breast cancer. These results may encourage further studies to explore full potential of T. portulacastrum phytoconstituents as breast cancer chemopreventive agents.
Chemoprevention of dibenzo[a,l]pyrene transplacental carcinogenesis in mice born to mothers administered green tea: primary role of caffeine.
Castro David J,Yu Zhen,Löhr Christiane V,Pereira Clifford B,Giovanini Jack N,Fischer Kay A,Orner Gayle A,Dashwood Roderick H,Williams David E
Our laboratory recently developed a mouse model of transplacental induction of lymphoma, lung and liver cancer by the polycyclic aromatic hydrocarbon, dibenzo[a,l]pyrene (DBP). Pregnant B6129SF1 females, bred to 129S1/SvIm males, were treated on day 17 of gestation with an oral dose of 15 mg/kg DBP. Beginning on day 0 of gestation, dams were given (ad lib) buffered water, 0.5% green tea, 0.5% decaffeinated green tea, caffeine or epigallocatechin-3-gallate (EGCG) (both at equivalent concentrations found in tea). The concentration of the teas (and corresponding caffeine and EGCG) was increased to 1.0% upon entering the second trimester, 1.5% at onset of the third trimester and continued at 1.5% until pups were weaned at 21 days of age. Offspring were raised with normal drinking water and AIN93G diet. Beginning at 2 months of age, offspring experienced significant mortalities due to an aggressive T-cell lymphoma as seen in our previous studies. Ingestion of caffeinated, but not decaffeinated, green tea provided modest but significant protection (P = 0.03) against mortality. Caffeine provided a more robust (P = 0.006) protection, but EGCG was without effect. Offspring also developed DBP-dependent lung adenomas. All treatments significantly reduced lung tumor multiplicity relative to controls (P < 0.02). EGCG was most effective at decreasing tumor burden (P = 0.005) by on average over 40% compared with controls. Induction of Cytochrome P450 (Cyp)1b1 in maternal liver may reduce bioavailability of DBP to the fetus as a mechanism of chemoprevention. This is the first demonstration that maternal ingestion of green tea, during pregnancy and nursing, provides protection against transplacental carcinogenesis.
Chemopreventive Effects of Korean Red Ginseng (Panax ginseng Meyer) on Exposure to Polycyclic Aromatic Hydrocarbons.
Lee Ho-Sun,Park Jong Yun,Yang Mihi
Journal of ginseng research
Polycyclic aromatic hydrocarbons (PAHs) are well known environmental carcinogens. PAH metabolites, especially BaP-7,8- dihydrodiol, 9,10 epoxide, initiate carcinogenesis via high specificity binding to DNA to form DNA adducts. The Korean red ginseng (KRG) from Panax ginseng has been suggested to protect against damages due to PAH exposure but the mechanism is unknown. Therefore, we investigated effects of KRG on PAH exposure using toxicokinetic methods and changes of PAH-induced oxidative damage during a 2 week-clinical trial (n=21 healthy young female, 23.71±2.43 years). To analyze antioxidative effects of KRG, we measured changes in the levels of urinary malondialdehyde (MDA) before and after KRG treatment. We observed a significant positive association between levels of urinary MDA and 1-hydroxypyrene, a biomarker of PAH exposures (slope=1.47, p=0.03) and confirmed oxidative stress induced by PAH exposures. A reverse significant correlation between KRG treatment and level of urinary MDA was observed (p=0.03). In summary, results of our clinical trial study suggest that KRG plays a significant role in antioxidative as well as toxicokinetic pathways against PAHs exposure.