Growth Control by Retinoids: Regulation of Cell Cycle Progression and Apoptosis

In multicellular organisms, a balance between differentiation, proliferation and cell death maintains tissue homeostasis in adult tissues and directs normal development during embryonic morphogenesis. Vitamin A is one of the critical factors regulating the molecular events involved in these processes. The requirement of retinoids for normal development and tissue homeostasis has been known since Wolbach and Howe first reported on the defects that occurred in vitamin A-deficient animals in 1926. A large literature has since appeared describing the role of retinoids in promoting proliferation, differentiation or apoptosis in vivo (see also Chaps. 12–15, this volume), in a variety of cell culture systems (see also Chaps. 3, 9, 10, this volume) and more recently through studies using retinoid receptor knock-out strategies (Taneja et al. 1996; Sapin et al. 1997). In addition, these investigations have provided insight into the mechanisms by which retinoids induce teratogenic effects and inhibit neoplastic development, and hold promise for new therapeutic applications of retinoids, particularly in cancer.