CDKN1B and cancer: In contrast, the proximal 5'-upstream region (-1797) of p27 gene (p27-Kpn I) was activated by four nutritional and chemopreventive anti-cancer agents, namely all-trans-retinoic acid (atRA), 9-cis-retinoic acid (9cRA), 13-cis-retinoic acid (13cRA) and dexamethasone (Fig. 1e).