TIP30 regulates apoptosis-related genes in its apoptotic signal transduction pathway

AIM: To investigate the role of TIP30 in apoptotic signal pathway in hepatoblastoma cells and to provide a basis for TIP30 as a gene therapy candidate in the regression of hepatoblastoma cells. METHODS: Apoptosis of human hepatoblastoma cell lines HepG2 (p53 wild), Hep3B (p53 null) and PLC/RPF/5 (p53 mutant) infected with Ad-TIP30 (bearing a wild type human Tip30 gene) were analyzed and p53, Bax and Bcl-xl expression levels were compared among these cells. MTT assay, DNA fragmentation, in situ 3' end labeling of DNA, annexin-V FITC staining were used to detect cell death and apoptosis in cells at various time intervals subsequent to infection, and to determine whether TIP30 had an effect on the expression levels of some apoptosis-related gene products such as Bax, p53 and Bcl-xl. A similar time course experiment was performed by Western blotting. RESULTS: In MTT assay, the viability of HepG2 cells decreased significantly from 99.7% to 10% and displayed more massive cell death within 5-8 d than Hep3B and PLC/ RPF/5 cells, with their viability decreased from 97.8% to 44.3% and 98.1% to 50.4%, respectively. In annexin-V FITC assay, the percentage of apoptosis cells in HepG2 cells was two to three-fold higher than that in control cells (infected with Ad-GFP), two-fold higher than that in Hep3B cells and 1.4-fold higher than that in PLC/RPF/5 cells 36 h after infection, respectively. Moreover, in HepG2 cells, the p53 began to increase 6-8 h after infection, reaching a maximum level between 8 and 12 h after infection and then dropped. Bax showed a similar increase in the cells as p53 reached the maximum at 8-12 h and subsequently decreased. Interestingly, Bcl-xl protein levels were down regulated during 24 to 36 h after Ad-TIP30 infection. In contrast, ectopic expression of TIP30 in Hep3B and PLC/ RPF/5 cells had no effect on the regulation of Bax expression, but had an effect on Bcl-xl levels. In comparison with HepG2 cells, these data suggested that up-regulation of p53 levels by TIP30 might be a pre-requisite for Bax and Bax/Bcl-xl ratio increase. We hypothesied that TIP30 might regulate Bax gene partly through p53, which sensitizes cells to apoptosis by involving a p53 apoptosis signal transduction pathway. CONCLUSION: TIP30 plays an important role in predisposing hepatoblastoma cells to apoptosis through regulating expression levels of these genes. Ad-TIP30 carrying exogenous TIP30-anti-tumor genes may be regarded as a potential candidate for the treatment of hepatocellular carcinoma.

Role of the JNK signal transduction pathway in inflammatory bowel disease

The c-Jun NH2-terminal Kinase (JNK) pathway representsone sub-group of the mitogen-activated protein (MAP)kinases which plays an important role in variousinflammatory diseases states, including inflammatorybowel disease (IBD). Significant progress towardsunderstanding the function of the JNK signaling pathwayhas been achieved during the past few years. Blockadeof the JNK pathway with JNK inhibitors in animal modelsof IBD lead to resolution of intestinal inflammation.Current data suggest specific JNK inhibitors hold promiseas novel therapies in IBD.

The signal transduction pathways and molecules for ES cells self-renewal

Embryonic stem cells (ES cells) are derived from the inner cell mass (ICM) of blastocysts. ES cells can divide and produce identical copies of them over and over again (self-renewal) in vitro for a long time, and retain the capability of differentiating into all cell types when induced by appropriate signals. Their capability of multilineage dif- ferentiation might be exploited for cell-based therapies. Therefore, ES cells have a broad prospect in many clinical applications. To achieve success in the clinical applications, we have to understand how ES cells propagate and differen- tiate into specific cell types. The cytokine LIF can sustain the self-renewal of certain mouse ES cells (mES cells) through activation of the signal transduction pathway LIF/gp130/ STAT3. In this pathway the transcription factor STAT3 is a crucial factor. Furthermore, Oct-3/4 plays a very important role in maintaining the ES cell pluripotency. Oct-3/4 regu- lates embryo development through its co-factor Sox2 and Rox-1. Recently nanog, a new homeodomain gene, was found and it has been shown to be crucial for the renewal and pluripotency of ES cells. Three other signals BMP, Wnt and ERK also can influence differentiation and propagation of ES cells. This review article summarizes recent progress in this area, mainly focusing on the LIF signaling pathway and the transcription factors Oct-3/4 and Nanog. Although it is still unclear how these components cooperate, a model is presented here to provide a design for solving this problem.