Tea polyphenols can restrict benzo[a]pyrene-induced lung carcinogenesis by altered expression of p53-associated genes and H-ras, c-myc and cyclin D1.

The modulatory influence of tea polyphenols (epigallocatechin gallate, epicatechin gallate and theaflavin) on benzo[a]pyrene (B[a]P)-induced lung carcinogenesis in mice was analyzed using histopathological and molecular parameters. Progression of lung lesions was restricted at the hyperplastic stage by tea polyphenols. A significant reduction in cellular proliferative index and an increase in apoptotic index were noted in the restricted lung lesions. High expression of H-ras, c-myc, cyclin D1 and p53 genes was seen at the inflammatory stage (9th week) and in subsequent premalignant lesions, but down-regulation of H-ras at the hyperplastic stage (17th week). Expression of bcl-2 was high in hyperplastic lesions, whereas the expression of mdm2 and bcl-xl increased only at the moderately dysplastic stage (36th week). The tea polyphenols inhibited inflammatory response in the lung lesions on the 9th week, when decreased expression of H-ras and c-myc and increased expression of bax were noted. Prolonged treatment (>9th week) with tea polyphenols resulted in changes in the expression of some additional genes, such as reduced expression of cyclin D1 (from the 17th week), bcl-2 (from the 26th week; mild dysplasia) and p21 (on the 36th week), and high expression of p53 (from the 17th week) and p27 (on the 36th week). These observations indicate that the tea polyphenols can restrict B[a]P-induced lung carcinogenesis by differential modulation of the expression of p53 and its associated genes such as bax, bcl-2, mdm2, p21 and p27, along with H-ras, c-myc and cyclin D1, at different time points.

Influence of regular black tea consumption on tobacco associated DNA damage and HPV prevalence in human oral mucosa.

Black tea is more widely consumed than green tea worldwide, particularly in India. Therefore, it is necessary to focus attention on black tea with respect to its health promoting and anti-cancer actions. In order to establish the concept that black tea is a potential candidate for cancer prevention, it is important to provide epidemiological evidence derived from investigations of human populations. In view of this, the objective of the present study was to determine the correlation between nature of black tea consumption and DNA damage in normal subjects with or without tobacco habit and oral cancer patients, taking the latter as positive controls. Much experimental evidence points to associations between tobacco habit and HPV 16 and HPV 18 (Human Papilloma virus) infection. But no studies have taken into account the possible confounding effect of black tea consumption on DNA damage along with HPV infection. A pilot study was therefore undertaken. Comet assay was used to evaluate the DNA damage among normal subjects including tobacco users (n = 86), non-tobacco users (n = 45) and Oral cancer patients (n = 37). Percentage of damaged cells was scored in the buccal squamous cells of all subjects mentioned above. HPV analysis was performed on 79 samples (including 37 oral cancer patients). The evaluation of various confounding factors like age, tenure of tobacco habit and tea habit showed significant associations with DNA damage. The observations strongly indicate that regular intake of black tea at least above four cups can reduce tobacco associated DNA damage among normal tobacco users. HPV prevalence was not seen to be associated with age, tenure of tobacco habit or the tea drinking habit.

Epigallocatechin gallate induced apoptosis in Sarcoma180 cells in vivo: mediated by p53 pathway and inhibition in U1B, U4-U6 UsnRNAs expression.

The aim of this study was to understand the mode of action of tea polyphenol epigallocatechin gallate (EGCG) in vivo. Swiss albino mice were treated i.p. with EGCG at two different doses i.e. 12-mg/kg body weight and 15-mg/kg body weight, for 7 days prior to inoculation of Sarcoma180 (S180) cells and continued for another 7 days. The growth of the S180, harvested 7 days after inoculation, was significantly reduced due to treatment with EGCG. The flowcytometric analysis of S180 cells, showed significant increase in apoptosis and reduction in the number of cells in G2/M phase of cell cycle due to treatment with EGCG. The induction of apoptosis has also been confirmed by the TUNEL and DNA fragmentation assays. Both RT-PCR and Western blot analysis showed significant up-regulation of p53 and bax, and down-regulation of bcl-2 and c-myc due to EGCG treatment. No changes in the expression pattern of p21, p27, bcl-xl, mdm2 and cyclin D1 were seen. Interestingly, there was significant down-regulation of spliceosomal uridylic acid rich small nuclear RNAs (UsnRNAs) U1B and U4-U6 due to EGCG treatment. This indicates that these UsnRNAs may be involved in the apoptosis process. Taken together, our study suggests that in vivo EGCG could induce apoptosis in S180 cells through alteration in G2/M phase of the cell cycle by up-regulation of p53, bax and down-regulation of c-myc, bcl-2 and U1B, U4-U6 UsnRNAs.

Differential alterations in metabolic pattern of the spliceosomal UsnRNAs during pre-malignant lung lesions induced by benzo(a)pyrene: modulation by tea polyphenols.

The differential alterations of the spliceosomal UsnRNAs (U1, U2, U4, U5, and U6) were reported to be associated with cellular proliferation and development. The attempt was made in this study to analyze the metabolic pattern of the spliceosomal UsnRNAs during the development of pre-malignant lung lesions induced in experimental mice model system by benzo(a)pyrene (BP) and also to see how tea polyphenols, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), modulate the metabolism of these UsnRNAs during the lung carcinogenesis. No significant changes in the level of the UsnRNAs were seen in the inflammatory lung lesions at 9th week due to treatment of BP. However, there was significant increase in the level of U1 ( approximately 2.5 fold) and U5 ( approximately 47%) in the hyperplastic lung lesions at 17th week. But in the mild dysplastic lung lesions at 26th week, the level of UsnRNAs did not change significantly. Whereas, in the dysplastic lung lesions at 36th week there was significant increase in the level of the U2 ( approximately 2 fold), U4 ( approximately 2.5 fold) and U5 ( approximately 2 fold). Due to the EGCG and ECG treatment the lung lesions at 9th week appeared normal and in the 17th, 26th, and 36th week it appeared as hyperplasia. The level of the UsnRNAs was significantly low in the lung lesions at 9th week (only U2 and U4 by EGCG), at 17th week (only U1 by EGCG/ECG), at 26th week (U1 by ECG; U2, U4 and U5 by EGCG/ECG) and at 36th week (U1 by ECG, U2 and U4 by EGCG/ECG). Whereas, there was significant increase in the level of U5 (by EGCG/ECG) and U6 (by EGCG only) in the lung lesions at 36th and 26th week respectively. This indicates that the metabolism of the spliceosomal UsnRNAs differentially altered during the development of pre-malignant lung lesions by BP as well as during the modulation of the lung lesions by the tea polyphenols.

Clove (Syzygium aromaticum L.), a potential chemopreventive agent for lung cancer.

Spices and flavoring plants part rich in supposedly health-promoting phytochemicals are currently receiving much attention as a possible source of cancer chemopreventive compounds. Clove, the sun-dried unopened flower bud from the plant Syzygium aromaticum L. is a commonly used spice and food flavor. In the present work we assess the chemopreventive potential of aqueous infusion of clove during benzo[a]pyrene (BP)-induced lung carcinogenesis in strain A mice. Incidence of hyperplasia, dysplasia and carcinoma in situ evident in the carcinogen control group on the 8th, 17th and 26th weeks, respectively, were effectively reduced after treatment with clove infusion. Significant reduction in the number of proliferating cells and an increased number of apoptotic cells was also noted in these BP-induced lung lesions following clove treatment. Western blotting analysis revealed that clove infusion upregulates the expression of pro-apoptotic proteins p53 and Bax, and downregulates the expression of anti-apoptotic protein Bcl-2 in the precancerous stages. Expression of caspase 3 and its activation by clove infusion were evident from a very early stage of carcinogenesis (eighth week). Clove infusion was also found to downregulate the expression of some growth-promoting proteins, viz, COX-2, cMyc, Hras. The observations signify the chemopreventive potential of clove in view of its apoptogenic and anti-proliferative properties.

Black tea polyphenols restrict benzopyrene-induced mouse lung cancer progression through inhibition of Cox-2 and induction of caspase-3 expression.

Lung cancer is one of the leading causes of cancer related death in most developed and many developing countries of the world. Due to lack of validated screening methods and poor prognosis, treatment of lung cancer has not improved significantly over the last two decades. Therefore the risk of the disease needs to be minimized by preventive measures. One approach for lung cancer prevention envisages reversal or restriction of precancerous lesions by chemopreventive intervention. It demands a deeper understanding of the pathogenesis of the disease and identification of the ideal point of intervention. In the present investigation, tea components, epigallocatechin gallate (EGCG) and theaflavins (TF) were assessed for their chemopreventive potential when administered in the post initiation phase of lung carcinogenesis in an experimental mouse model. Histopathological changes in lungs of mice administered benzo(a)pyrene (BP) were followed serially and correlated with the expression of Cox-2, caspase-3 and caspase-7, which play key roles in histopathogenesis of neoplasia. The observations strongly indicate that both EGCG and TF can influence the expression of these genes to modulate the process of carcinogenesis, resulting in delayed onset and lowered incidence of pre-invasive lung lesions.

Inhibition of growth, induction of apoptosis and alteration of gene expression 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 NCI-H460. 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.