Protease Action in Carcinogenesis

Abstract

The major cause of cancer appears to be the environment. Estimates of 80%–90% of cancer incidence have been ascribed to environmental factors (1,2). The main evidence for this startling hypothesis has come from epidemiological studies of migrant populations. Here, it has been noted, that the cancer incidence pattern changes from that of the migrants’ native country to that of the host country within a few generations (3). A well-known example is the study of Japanese migrants to the United States. The incidence of colon and breast cancer in Japan is low, while that of stomach cancer is high. The reverse pattern is prevalent in the United States. Within the three generations, the incidence of cancer in Japanese living in the U. S. shifts from the pattern found in Japan to that in the U. S. (Fig. 1).