- The possible involvement of several transcription systems in the anticancer activity of carotenoids is the focus of this review. Carotenoids modulate the basic mechanisms of cell proliferation, growth factor signaling, gap junctional intercellular communication, and produce changes in the expression of many proteins participating in these processes. The changes in the expression of multiple proteins suggest that the initial effect of carotenoids involves modulation of transcription. We and others have found evidence for the role of several transcription systems, such as the retinoid receptors, activator protein-1 (AP-1), peroxisome proliferator-activated receptors (PPAR), xenobiotic receptors and the antioxidant response element (ARE), in the anticancer activity of carotenoids. The observed modulation of a network of transcription systems may provide the molecular basis for the synergistic anticancer effects of the combinations of various carotenoids together with other dietary and pharmacologic compounds.