Related Experiment Videos
Mechanisms of inhibition of carcinogenesis by tea
C S Yang1, J Y Chung, G Y Yang
1Laboratory Cancer Research, College of Pharmacy Rutgers, The State University of New Jersey, Piscataway 08854-8020, USA. csyang@rci.rutgers.edu
Abstract:
Tea (Camellia sinensis) preparations have been shown to inhibit tumorigenesis at the initiation, promotion, and progression stages in different animal models. The anti-proliferative effects of tea polyphenols may be a key mechanism, especially in the NNK-induced lung tumorigenesis model with mice. Studies with cell lines have demonstrated that tea polyphenols inhibit cell proliferation and induce apoptosis. The effective concentrations used in these studies (20-100 microM) are usually higher than those observed in blood and tissues of humans and animals, which are in the low micromolar range. Glucuronide and sulfate conjugated and methylated catechins as well as ring fission products (due to intestinal microflora) have been observed in human plasma and urine. Purified green and black tea polyphenols inhibited the H-ras induced milogen-activated protein kinases, AP-1 activities, and the growth of 30.7b Ras 12 and BES21 cells. Among the catechins, both the galloyl structure on the B ring and the gallate moiety are important for the inhibition. Both (-)-epigallocatechin-3-gallate and theaflavin-3,3'-digallate inhibited the phosphorylation of c-jun and p44/42 (ERK 1/2). More mechanistic and human studies in these areas will help us to understand the possible inhibitory action of tea against carcinogenesis in humans.
Insights
Tea polyphenols show anti-cancer properties by inhibiting cell proliferation and inducing apoptosis. Further human studies are needed to confirm tea
Area of Science:
- Oncology
- Pharmacology
- Nutritional Science
Background:
- Tea (Camellia sinensis) preparations exhibit inhibitory effects on tumorigenesis across various stages in animal models.
- Tea polyphenols are hypothesized to exert anti-proliferative effects, particularly in models of lung tumorigenesis.
- In vitro studies indicate tea polyphenols can inhibit cell proliferation and induce apoptosis.
Purpose of the Study:
- To investigate the anti-cancer mechanisms of tea polyphenols, focusing on their effects on cell proliferation and signaling pathways.
- To explore the role of specific tea compounds, like catechins and theaflavins, in inhibiting cancer cell growth.
- To assess the relevance of in vitro findings to in vivo conditions by considering human metabolic profiles.
Main Methods:
- Utilized cell line studies to assess the impact of tea polyphenols on proliferation and apoptosis.
- Investigated the effects of purified green and black tea polyphenols on specific signaling pathways (H-ras, AP-1, c-jun, ERK 1/2).
- Analyzed the chemical forms of tea catechins in human plasma and urine, including conjugated and ring-fission products.
Main Results:
- Tea polyphenols demonstrated inhibition of cell proliferation and induction of apoptosis in cell line studies.
- Effective concentrations in vitro (20-100 microM) were higher than observed in human and animal tissues (low micromolar range).
- Purified tea polyphenols inhibited key signaling pathways (H-ras, AP-1) and cell growth, with specific structural features of catechins being important for inhibition.
- (-)-Epigallocatechin-3-gallate and theaflavin-3,3'-digallate were shown to inhibit phosphorylation of c-jun and p44/42 (ERK 1/2).
Conclusions:
- Tea polyphenols possess anti-proliferative and pro-apoptotic properties relevant to cancer inhibition.
- The anti-cancer activity of tea polyphenols involves the modulation of key signaling pathways.
- Further mechanistic and human studies are warranted to elucidate the full potential of tea in human cancer prevention.