Inhibition of the Carcinogenic Process and of Expression of the Neoplastic Phenotype

Abstract

Current interest in inhibitors of carcinogenesis stems from our increasing understanding of mechanisms of carcinogenesis, which in turn has been stimulated by the growing realization that the majority of human cancer is of environmental origin. Environmental studies of cancer incidence on a world-wide basis have revealed striking differences in the rates of such neoplasms as those of the colon, breast, and lung, which are common in the United States but occur much less frequently in non-Western societies (Doll et al., 1970). Of particular interest is the low incidence rate for breast cancer and the high rate for stomach cancer in Japan, which contrast with the high breast cancer and low stomach cancer rates in the U.S. That these differences are not primarily of racial origin is apparent in studies of Japanese migrants to the U.S., who begin to aquire incidence rates characteristic of the host country (Haenszel and Kurihara, 1968). Similarly, studies within the U.S. have shown wide geographaphic differences in cancer incidence, the highest levels being typically found in urban industrial settings. In contrast, some of the lowest incidence rates are found among groups such as Seventh-Day Adventists, whose life-style includes the prohibition of alcohol and tobacco, and a lacto-ovovegetarian diet.