Induction and Inhibition of Tumor Progression

Carcinogenesis has been demonstrated by experimental and epidemiologic studies to be a multistage process composed of three major stages, initiation, promotion, and progression (1). The progression stage of this process encompasses the changes by which a tumor develops from a contained, differentiated lesion of uncoordinated growth into a rapidly growing, invasive lesion that can spread to other areas of the body, i.e., from a benign to a malignant tumor. Progression is of great therapeutic relevance because the process involves a change from a lesion that is easily treated surgically to one requiring extensive therapy with less favorable outcome.