APPLICATION OF RETINOIDS FOR THE TREATMENT OF CANINE FELINE CANCER

摘要

Retinoids are natural or synthetic derivatives of vitamin A that exert profound effects on the growth and differentiation of many cell types both in vivo and in vitro. Retinoids are essential for epithelial differentiation; they have been demonstratedto induce growth inhibition and cell cycle arrest in cancer cells by induction of terminal differentiation and apoptosis. This effect occurs through interaction with specific retinoid nuclear receptors that are part of the steroid superfamily of nuclearreceptors. Retinoid receptors function as ligand-dependent transcription factors, and with retinoid binding and activation of the receptor leading to transcription of responsive genes. Retinoid receptors are divided in two families: the retinoic acid receptors (RARs); and the retinoid X receptors (RXRs, also called rexinoids). Each family has three receptor subtypes (alpha, beta and gamma), with multiple isoforms and specific genes that encode each of them. In the physiologic setting, the natural diet-derived retinoids (all-trans retinoic acid-ATRA and 9-cis-RA), have different binding affinities to the receptors. Specifically, ATRA and 9-cis-RA bind RAR, but only 9-cis-RA binds RXR).