Advanced progress on the relationship between RA and its receptors and malignant tumors

Retinoic acid (RA) is an active derivative of vitamin A, and it has different isomers, including ATRA (all-trans-retinoic acid), 13-cRA (13-cis-retinoic acid) and 9-cRA (9-cis-retinoic acid), etc. Combining with RARs and RXRs, RA plays important roles not only in embryonic development but also in cellular growth and differentiation through transcriptional regulation of its target genes. Following the successful application in the differentiation therapy of acute promyelocytic leukemia (APL) in clinical, recent studies have found that the disturbance of RA signal transduction was also related to differentiation, proliferation or apoptosis of tumor cells. To develop novel mechanisms-based differentiation therapy for other tumors, the relationship between RA or its receptors and tumors will be summarized in this review.