BACKGROUND: Previous reports from these authors found that activation of peroxisome proliferator-activated receptor gamma (PPARc) suppressed hepatocellular carcinoma (HCC). This study sought to identify the molecular target of PPARc and characterize its antitumor effect in HCC. METHODS: Optimal PPARc binding activity was obtained using the PPARc agonist rosiglitazone (100 lM) as determined by enzyme-linked immunosorbent assay. Under PPARc activation, 114 PPARc downstream targets associated with cancer development were identified by oligonucleotide microarray and Gene Ontology analysis. Among them, Cbp/p300-interacting transactivator, with Glu/Asp-rich carboxy-terminal domain, 2 (CITED2) was the most prominent PPARc-bound target, as determined by chromatin immunoprecipitation-polymerase chain reaction. RESULTS: CITED2 messenger RNA and protein was significantly down-regulated in primary HCCs compared with their adjacent nontumor tissues. PPARc induced expression of CITED2 in HCC cell lines after adenovirus-PPARc transduction. The biological function of CITED2 was evaluated by loss-and gain-of-function assays. CITED2 knockdown in the hepatocyte cell line LO2 and HCC cell line Hep3B significantly increased cell viability and clonogenicity, and promoted G 1 -S phase transition in both cell lines. In contrast, ectopic expression of CITED2 in HepG2 and BEL7404 HCC cell lines significantly suppressed cell growth. The tumor suppressive effect of CITED2 was associated with up-regulation of cyclin-dependent kinase inhibitors p15 INK4B , p21 Wat1/Cip1 , p27 Kip1 , antiproliferative regulator interferon alpha 1, proapoptotic mediators including tumor necrosis factor receptor superfamily member 1A (TNFRSF1A), TNFRSF25, caspase-8, granzyme A, and the tumor suppressor gene maspin. CITED2 was also associated with the down-regulation of cell cycle regulator cyclin D1, oncogene telomerase reverse transcriptase, and proinvasion/metastasis gene matrix metallopeptidase 2. CONCLUSIONS: CITED2 is a direct effector of PPARc for tumor suppression.