CARCINOGENESIS - ENVIRONMENT AND GENETICS

In carcinogenesis, both individual disposition and external factors ar e important. Age, sex, hormones, and psyche play a role. But oncogenes is probably is mainly a result of genetic damage, of the accumulation of activated proto-oncogenes and the inactivation of tumor suppressor For instance, ras-oncogenes and inactivation of the p53-gene are found in many malignant tumors and in precancerous lesions. Vulnerability o f genetic material responsible for tumorigenesis is inherited. Changes may occur spontaneously, or genotoxic substances or conditions as ion ising radiation and UV light induce, for instance, point mutations, tr anslocations or gene amplification. This can take place long before th e manifestation of a tumor. Generally, activation not only of one, but of several proto-oncogenes and inactivation of suppressor genes coinc ide in the development of many tumors. A rather complete picture of tu morigenesis starts to emerge. However, many white regions await furthe r description. Prevention and therapy will profit from these new insig hts into tumor initiation.