RARRES1 (Retinoic acid receptor responder 1) is a retinoid-regulated gene whose expression is down-regulated through DNA hypermethylation. It was originally identified as a target gene that was induced by the synthetic retinoid tazarotene (AGN 190168). Its expression is upregulated by retinoic acid receptor-specific, but not by retinoid X receptor-specific retinoids. Although the function of RARRES1 is not entirely clear, it is thought to act as a tumor suppressor of a variety of human cancers since inactivation of RARRES1 is involved in the malignant progression of prostate cancer. It may also function as a cell adhesion molecule. Additionally, RARRES1 may also have protease inhibitor activity and inhibit the degradation of extracellular matrix.