The molecular determinants of carcinogenesis

This monograph has emphasized the molecular aspects of both the differences between cancer and normal cells and the development of a cancer cell from a normal cell. Multistage carcinogenesis is now well known in a variety of histogenetic circumstances, and definable stages of initiation, promotion, and progression have been identified. Activation of proto-oncogenes in neoplasms may occur at any time during the development of malignancy, but most examples to date have shown this occurrence during the final stage of progression. A new form of carcinogenesis, that induced by specific genetic constructions in vivo or in vitro, has been accomplished. The specificity of genetic carcinogenesis can reside in the specific construct itself, especially in tissue-specific enhancer regions. On the other hand, the specific molecular genetic characteristics of at least one human genetic condition resulting in a high incidence of a specific histogenetic type of neoplasia, hereditary neuroblastoma, have been partially characterized. All of the various types ov carcinogenesis--genetic, viral, chemical, and radiation--exhibit, or at one time or another or in one situation or another, multiple stage ion their development.