Tea and cancer chemoprevention: a comprehensive review.

Dietary components that are capable of inhibiting the growth of cancer cells without affecting the growth of normal cells are receiving considerable attention in developing novel cancer-preventive approaches. Tea, made from young leaves and leaf buds of the tea plant, 'Camellia sinensis', and the world's second most consumed beverage, has received a great deal of attention both from the general public and the scientific community because tea polyphenols are strong antioxidants, and tea preparations have inhibitory activity against tumorigenesis. Besides this, the wide spread consumption of tea throughout the world evoked the interest of the scientific community in the possibility of its use in cancer prevention. There are three main types of tea, all coming from the tea plant viz. black tea (fermented,) green tea (unfermented), or oolong tea (semi-fermented), classified based on the methods of brewing and processing. Inhibition of tumorigenesis by green or black tea preparations has been demonstrated in various animal models in different organs. Various epidemiological studies substantiate the correlation between tea consumption and cancer prevention; however, they have not yielded clear conclusions pertaining to the protective effects of tea consumption against cancer development in humans. Many mechanisms have been proposed for the inhibition of carcinogenesis by tea, including the modulation of signal transduction pathways (including growth factor-mediated, mitogen-activated protein kinase (MAPK)-dependent, and ubiquitin/proteasome degradation pathways ) that lead to the inhibition of cell proliferation and transformation; induction of apoptosis of preneoplastic and neoplastic cells, and inhibition of tumor invasion as well as angiogenesis. These mechanisms need to be evaluated, verified and corroborated in animal models and humans in order to gain more understanding on the effects of tea consumption on human cancer. Because the causative factors are different for different populations, tea consumption may affect carcinogenesis only in selected situations rather than having the general effect on all cancers. Although, on the basis of many epidemiological observations and numerous laboratory studies, it can be concluded that tea consumption is likely to have beneficial effects in reducing cancer risk in different populations, yet there is a need to define the population that could benefit from tea consumption. After careful evaluation of additional studies, it may be possible to recommend consumption of tea polyphenols by humans. Although considerable accumulating information provides a compelling body of evidence for the preventive potential of tea against cancer, naturally occurring tea polyphenols have yet to be evaluated in clinical intervention in human trials.

Involvement of multiple signaling pathways in diallyl sulfide mediated apoptosis in mouse skin tumors.

Many chemopreventive agents appear to target signaling intermediates in apoptosis-inducing pathways. Inherently, the process of neoplastic conversion selects against apoptosis to initiate, promote, and perpetuate the malignant phenotype. Thus, targeting apoptosis pathways in pre-malignant cells, in which these pathways are still relatively intact, may be an effective module of cancer prevention. Diallyl sulfide (DAS), a naturally occurring organosulfide, present in garlic, is reported to have pleiotropic biological effects. DAS is known to inhibit chemically induced tumors in a number of in vivo and in vitro studies. The aberration of tumor suppressor gene, p53 and the ras oncogene have been linked to the induction of multiple signaling pathways and to the resistance offered by cancer cells to the apoptosis. Therefore, the present study was carried out to investigate the role of DAS on modulation of multiple p53 and ras-induced signaling pathways in 7,12-dimethylbenathacene (DMBA) induced skin carcinogenesis. The results showed that DAS up regulates expression of tumor suppressor protein p53 (wt p53) and its downstream target molecule p21/waf1. Proapoptotic protein, bax was upregulated by DAS supplementation. An opposite trend was observed in DMBA induced antiapoptotic proteins expressions, survivin and bcl-2, which were significantly downregulated by DAS supplementation. In the present study we also demonstrated that DAS supplementation significantly reduces the expression of ras oncoprotein and to modulate expression of its signaling molecules including PI3K/Akt and MAPKs. Western blot analysis demonstrated that DAS significantly reduced the DMBA induced protein expressions of PI3K/Akt and p38MAPK. However, DAS supplementation did not alter the expression JNK1 and ERK1/2. Thus, our results confirm that DAS can adopt a multi-prong strategy to target multiple signaling pathways leading to induction of apoptosis and inhibition of growth of DMBA induced skin tumors in Swiss albino mice. Although studies of single pathways have been helpful in guiding investigations, new tools to study the integration and multiplicity of signaling pathways hold the hope of improved understanding of the signaling pathway alterations in cancer chemoprevention by naturally occurring compounds.

Complementary and alternative cancer therapies: past, present and the future scenario.

Use of complementary and alternative therapies is widespread among cancer patients. Throughout the world cancer patients try many questionable or unproven treatment methods. The reasons for adopting these therapies are complex and are related to the social and cultural contexts of their geographical locations. In case of severe illness, the desire to leave no stone unturned is a powerful motivator. In developing countries, ignorance, socioeconomics, and inadequate access to mainstream medical facilities are major factors that play an important role for patients opting for alternative therapies that are replacements for mainstream treatment. Whereas in developed countries a significant proportion of cancer patients try complementary therapies as adjuncts to mainstream care for management of symptoms and to improve quality of life. Many alternative therapies, including pharmacological and biological treatments, remain highly controversial but at the same time are very popular. Evidence from randomized trial supports the value of hypnosis for cancer pain and nausea; relaxation therapy and massage for anxiety; and acupuncture for nausea. This article reviews the different popular alternative cancer therapies practiced in India and neighboring south east Asian countries to project the current international scenario on complementary and alternative cancer therapies.

Herbal medicine: current status and the future.

The number of patients seeking alternate and herbal therapy is growing exponentially. Herbal medicines are the synthesis of therapeutic experiences of generations of practicing physicians of indigenous systems of medicine for over hundreds of years. Herbal medicines are now in great demand in the developing world for primary health care not because they are inexpensive but also for better cultural acceptability, better compatibility with the human body and minimal side effects. However, recent findings indicate that all herbal medicines may not be safe as severe consequences are reported for some herbal drugs. Most herbal products on the market today have not been subjected to drug approval process to demonstrate their safety and effectiveness. Thousand years of traditional use can provide us with valuable guidelines to the selection, preparation and application of herbal formulation. To be accepted as viable alternative to modern medicine, the same vigorous method of scientific and clinical validation must be applied to prove the safety and effectiveness of a therapeutical product. In the present review we attempted to describe the present scenario and project the future of herbal medicine.

Antimutagenic effects of black tea in the Salmonella typhimurium reverse mutation assay.

Black tea (Camellia sinensis) is one of the most widely consumed beverages worldwide. Its chemopreventive effects are well documented in the literature. In the present set of investigations antimutagenic effects of aqueous black tea extract (ATE) and black tea polyphenols (BTP) were evaluated in the Ames test using Salmonella typhimurium tester strains TA 98 and TA 100. Addition of benzo(a)pyrene (BaP) and cyclophosphamide (CP), two well known mutagens, at the concentrations of 20 and 15 microg/plate, respectively, in an S-9 metabolically activated system resulted in significant induction of his+ revertant colonies. However, addition of 500 microl 1, 2 and 4% ATE to the BaP and CP treated plates resulted in a dose dependent inhibition in the number of his+ revertant colonies. Furthermore in another set of experiments, supplementation with BTP at the concentrations of 100, 200 and 400 microg/plate also led to a significant inhibition in BaP and CP induced colony formation. The antimutagenic activity of BTP was found to be higher than that of ATE, which may be attributable to the higher amount of polyphenolic ingredients. Hence the study revealed that black tea has a protective efficacy in suppressing BaP and CP induced mutagenicity in a microbial test system.