Oxidative stress is the main cause of cardiac injury during ischemia/reperfusion but the molecular mechanism for this process is unclear. In this study, it was found that hypoxia induces apoptosis in rat embryonic heart-derived H9c2 cells leading to the induction of GADD153, which is an apoptosis-related gene. Therefore, this study addressed the molecular role of GADD153 in hypoxia-induced apoptosis. The stable or inducible overexpression of GADD153 sensitized the H9c2 cells to apoptotic cell death. The results suggest that the transactivation domain of the GADD153 might be responsible for this cell execution and play a role in the nucleoplasmic localization of GADD153. The cells transiently transfected with the antisense GADD153 were more resistant to hypoxia-induced apoptosis than the vector control cells. Furthermore, GADD153 transcriptionally down-regulated the expression of the cardiac ankyrin repeat protein gene (CARP), which is a nuclear transcriptional co-factor that negatively regulates the expression of the cardiac gene. The ectopic expression of CARP in H9c2 cells increased the resistance to hypoxia-induced apoptosis. These results suggest that GADD153 overexpression and the concomitant down-regulation of CARP might have a causative role in the apoptotic cell injury of hypoxic H9c2 cells.

Opa interacting protein 5 (OIP5) is upregulated in some types of human cancers, but the biological implications of its upregulation have not yet been clarified in human hepatocellular carcinoma (HCC). In this study, the signaling pathway downstream of OIP5 was analyzed by proteome kinase profiling. A putative microRNA targeting OIP5 was identified using a miRNA PCR array. Tumorigenicity and metastatic ability were examined in an orthotopic animal model. OIP5 expression was strongly detected in early and advanced tumors via gene expression profiling and immunohistochemical staining analyses. Cells with knockdown of OIP5 via target shRNA exhibited reduced hepatic mass formation and metastatic tumor nodules in an orthotopic mouse model. OIP5-induced AKT activation was mediated by both mTORC2 and p38/PTEN activation. AKT activation was linked to mTORC1 and GSK-3β/β-catenin signaling, which are primarily associated with tumor cell growth and metastasis, respectively. miR-15b-5p, which targets OIP5, efficiently inhibited OIP5-mediated mTORC1 and GSK-3β/β-catenin signaling. These findings suggest that OIP5 may be involved in HCC growth and metastasis and that miR-15b-5p inhibits OIP5-mediated oncogenic signaling in HCC.

The transcription factor CHOP/GADD153 is reportedly induced by cellular stresses such as UV light, genotoxic agents, and protein misfolding in the endoplasmic reticulum. However, the mechanism whereby induction of the GADD153 gene is linked to a downstream pathway is still unclear. Previously, we observed that a synthetic retinoid N-(4-hydroxyphenyl)retinamide (4HPR) effectively impaired cell growth and survival (induction of growth arrest and apoptosis) in human hepatoma cells, which was accompanied by over expression of GADD153. Furthermore, GADD153-transfected Hep 3B cells were growth arrested and were sensitized to drug-induced apoptosis. Thus, in this study, we used suppression subtractive hybridization (SSH) to identify GADD153 target genes that were up-regulated or down-regulated in the GADD153 transfectants. We screened 614 sequence-verified clones by Northern blotting, of which 42 genes were scored as over expressed and 17 genes as under expressed in GADD153 transfectants compared with control vector transfectants. Of those genes, 49 corresponded to known genes in public databases. Among them, we further verified that the expression of transferrin (Tf), which is a negative acute-phase protein and is essential to cell survival as a growth factor, was highly modulated by drug-induced

CTHRC1 expression is involved in invasion and metastasis in various tumors. However, the molecules involved in its signaling pathways in hepatocellular carcinoma (HCC) remain elusive. The migration and invasion abilities of HCC cells stably expressing CTHRC1 were assessed in vitro and in vivo with a mouse model. Moreover, signaling pathways involved in invasion and metastasis were analyzed. CTHRC1 was abundantly expressed in HCC cell lines and HCC tissues. CTHRC1 was also detectable in the serum of HCC patients, compared with non-tumor controls. CTHRC1 mRNA was positively correlated with large tumor size (p <0.003), Edmondson differentiation grade (p <0.0001), microvessel invasion (p <0.05), intrahepatic metastasis (p <0.005), and HCC stage (AJCC, p <0.0001). Ectopic expression of CTHRC1 in HepG2 cells promoted cell migration and invasiveness in vitro, and promoted tumor metastasis in a lung metastasis mouse model. Knockdown of CTHRC1 by short hairpin RNA (shRNA) in HCC cells suppressed migratory and invasive abilities. Growth factor-mediated CTHRC1 expression promoted cancer cell invasiveness and metastasis through activation of CREB/Snail signaling, which induced EMT change and MMPs expression. Therefore, CTHRC1 and its downstream molecules may be potential therapeutic targets for HCC invasion and metastasis.

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