Tobacco-induced carcinogenesis and chemoprevention by some natural products

Abstract

Tobacco habit is one of the main etiological factors responsible for cancer in body's multiple organs due to the presence of numerous carcinogens. In different animal models, it was evident that the carcinogens could induce carcinogenesis in multiple organs depending on its route of exposure site (e.g., skin, oral cavity, and lung), metabolism (e.g., liver and lung), and excretion (e.g., lung and kidney). It was evident that the active carcinogen metabolites could induce cellular reactive oxygen species (ROS) level, bind to DNA/RNA/proteins, thereby transforming the stem cell of the specific organs toward neoplasm. Different epidemiological studies including our own showed few natural compounds might reduce the risk of tobacco-induced carcinogenesis. The anticarcinogenic roles of crude extract as well as active compounds of such natural dietary ingredients were also evaluated by several in vivo animal models. Most of the active components have potential antioxidative, anti-inflammatory, and anticarcinogenic roles. For better understanding, the roles of three different types of compounds were selected for this review 1. Tea polyphenols from Camellia sinensis: epigallocatechin gallate and theaflavin; 2. amarogentin from Swertia chirata; and 3. Eugenol from Syzygium aromaticum. Studies showed that three types of compounds could restrict the carcinogenesis in different organs at premalignant stages. This might be due to antioxidation and activation of detoxification system, inhibition of cancer initiating stem cell population, modulation of multiple cellular pathways associated with cell cycle, cell proliferation, and survival which ultimately lead to restrict tumor development at initiation/promotion stage.