Molecular and Biochemical Control of Tumor Growth Following Treatment With Carotenoids or Tocopherols

Abstract

Chemopreventative agents such as retinoids, carotenoids or tocopherols have been shown in vitro and in animal models to inhibit, prevent, and regress established malignancies when they are administered in combination. Their mode of action appears to involve oxygen reactivity, which results in either the control or the promotion of tumor cell growth. Recent evidence indicates that there are common mechanisms for the growth inhibitory effects of these different chemopreventative groups. These include the reduction of mutant p53 protein expression with increases in protein expression of wild type p53 and stress protein 70 and 90 kD in treated tumor cells. An accumulation of cells in G1 of the cell cycle, a change in cyclin complex activities, and a reduction in the expression of transcription protein factors in tumors cells was also noted for carotenoids and alpha tocopherol activity. There was also an increase in programmed cell death as determined by the nucleosome formation. At higher concentrations these agents can induce increased growth and mitotic activity dissociated from programmed cell death processes.Oxygen reactive nutrients may inhibit growth but they also may contribute to the triggering of side effects in human populations.