Hormones and multistage carcinogenesis.

Initiation, promotion and the role of hormones in carcinogenesis are viewed within the framework of a two-stage model for malignant transformation that has been shown by Moolgavkar and Knudson to be consistent with the main body of epidemiological and experimental data on carcinogenesis. It is argued that hormones influence carcinogenesis principally by clonal expansion or contraction of initiated or first-stage cells. The role of hormones in breast cancer and endometrial cancer is briefly discussed.