Assembling a Tumor Progression Model

Tumor progression can very broadly be def ined as the progression from a less advanced to a more advanced neoplasm, due to the acquisition of genetic or other cell biologic alterations (Fig. 1 ). Implicit in this definition is the hypothesis that these acquired cellular alterations endow neoplastic cells with a growth advantage that is subsequently selected for in the evolution of the more advanced lesion ( 1 ). As such, these acquired alterations are the answers to many critical questions regarding tumor biology. As an example, consider the transformation that occurs when a benign neoplasm progresses to malignancy. Delineating the events that occur during this process could also yield new clinical tools for diagnosis and treatment, while understanding the forces that drive the acquisition of these alterations could yield insights into putative preventive targets.   Fig. 1.  Simple model of neoplastic progression. Less advanced neoplasms acquire genetic or epigenetic alterations that are selected for during tumor growth, resulting in clonal evolution.