Chemoprevention by coffee and coffee components

Although „chemical compounds“ are often rather perceived as pro-carcinogenic in the eyes oft the public, it has to be strongly emphasized that many of these compounds may also protect against cancer. The intake of such substances is at times caused by life-style but can also occur in the frame of targeted intervention measures. The protective mechanisms involved are summarized as „ chemoprevention“ (other than chemotherapy) whenever they are effective before diagnosis and thus usually before the onset of symptoms of the disease. Since cancer is mostly diagnosed at a rather late time point in the carcinogenic process, chemopreventive mechanisms may be aimed at various stages of carcinogenesis (e.g. carcinogen-activation, tumor initiation, tumor promotion) and equally at many different mechanistic systems. Thus, a varied field of action for chemoprevention research at different levels is provided.

Since epidemiological studies had repeatedly revealed lower rates of colon and liver cancers in coffee drinkers we made potential protective mechanisms of coffee and its components a specific focus in our research activity. Our main interest is directzed towards the diterpenes kahweol and cafestol which are contained in the coffee bean and in several types of coffee. Indeed, we have observed more than one beneficial effect as a consequence of their intake. For instance, carcinogen-detoxfying enzymes are induced whereas carcinogen-activating enzymes are at the same time inhibited. There is also enhancement of an important system that repairs alkylated DNA and protection against oxidative stress is increased at several levels. Investigation of all of these systems of protection is presently being continued in order to achieve a more thorough characterization of the involved mechanisms and to find new approaches. In this context, we are particularly intertested in redox effects on thiols such as glutathione and thioredoxin which may, just like „switches“, influence the function of numerous proteins. In addition, other potentially chemopreventive compounds (e.g. xanthumol oder quercetin) are/were targets in our studies.