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.

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.

Anticarcinogenic effects of an aqueous infusion of cloves on skin carcinogenesis.

Spices and flavouring agents are now receiving increasing attention as many of them have been shown to have anticarcinogenic properties. Cloves, sun-dried unopened flower buds from the plant Syzygium aromaticum L, are commonly used as a spice and food flavour. The present study was designed to investigate the chemopreventive action of aqueous infusion of cloves on 9,10-dimethyl benz(a)anthracene (DMBA) and croton oil induced skin carcinogenesis in Swiss mice. The results indicate protection against skin papilloma formation in a dose dependent manner. It has been shown that oral administration of aqueous infusions of clove at a dose of 100 microl/mouse/day not only delays the formation of papilloma but also reduces the incidence of papilloma as well as the cumulative number of papillomas per papilloma bearing mouse. Our observations suggest a promising role for cloves in restriction of the carcinogenesis process.

The models for assessment of chemopreventive agents: single organ models.

Research in cancer chemoprevention involves a number of activities, the first and foremost of which is acquisition of detailed knowledge concerning the process of carcinogenesis and identification of points of intervention whereby the process can be reversed or stalled. Parallel to this is the search for ideal chemopreventive agents--natural or synthetic--and screening for their activity and efficacy in vitro and in vivo. For ethical reasons it is not possible to test new agents on humans, so preclinical studies are dependent on results first being obtained with suitable animal models. Since it is not possible for a single model to reflect the diversity and heterogeneity of human cancers, it is necessary to have as many different models as possible, depending on the requirement of the studies on different aspects of cancer biology. Advances in research on carcinogenesis and chemoprevention therefore have to be accompanied by development of appropriate laboratory animal models using a variety of carcinogens that produce tumours at different sites. Animal models have contributed significantly to our understanding of carcinogenesis and ways to intervene in the underlying processes. Many animal carcinogenesis and tumour models have been found to mirror corresponding human cancers with respect to cell of origin, morphogenesis, phenotype markers and genetic alteration. In spite of the fact that interpolation of data from animal studies to humans is difficult for various reasons, animal models are widely used for assessment of new compounds with cancer chemopreventive potential and for preclinical trials. So despite the movements of animal rights activists, animal models will continue to be used for biomedical research for saving human lives. In doing so, care should be taken to treat and handle the animals with minimal discomfort to them and ensuring that alternatives are used whenever possible.