FIG. 1.

Oxidative stress and antioxidant defenses during tumor progression. Local environmental and metabolic changes acquired during the processes of tumor initiation and progression from a benign cell to carcinoma in situ and invasive carcinoma result in increased oxidant generation from several different sources (left side). This progressive increase is met with enhancement of antioxidant defenses (right side) that protect tumor cells and promote survival and aggressiveness. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars