[Improving cancer treatment, from the standpoint of basic cancer research]

It has been reported that most human carcinomas result from exposure to the carcinogens present in certain foods, products of cigarette smoking and the general environment. A number of chemicals have already been isolated and tested for potential carcinogenesis in animals, and we report on the following aspects of chemical carcinogenesis. A series of new mutagenic heterocyclic amines have been isolated from pyrolysates of amino acids and proteins, and from cooked foods such as the charred parts of broiled fish and meat. Among these heterocyclic amines, nine compounds have been studied in long-term animal experiments, all of which were shown to cause carcinomas in mice. Some chemicals were also proved to be carcinogenic in rats. Because of their eating habits, people may simultaneously ingest mutagens and carcinogens, both of which have been found in certain cooked foods. Nitrosatable precursors of mutagens and tumor promoters have also been discovered in food--a finding of great importance in this particular context. Thus, it would appear that people are ingesting carcinogens, precursors of mutagens, tumor promoters, and tumor inhibitors, simultaneously. Commonly encountered human pathological conditions, such as viral and bacterial infections, non-infections inflammatory diseases, nutritional disorders, hormonal or homeostatic disturbances, gall and/or kidney stones, and benign proliferative disorders may be shown to be precursors for the development of future cancers. In most cases, however, the scientific evidence to support this theory has not been completely evaluated, but the existence of such pathological conditions should be taken into consideration whenever the development of a cancer is being studied. The division which at one time existed between basic cancer research and the clinical investigation of the disease has begun to disappear. The importance of clinical investigation and its use in the prevention of disease has been demonstrated, for example, in studies of adult human T-cell leukemia.