Quantitative measurement of ADC of HCC with magnetic resonance diffusion weighted imaging is a promising functional imaging tool in the prediction of histological grade and early recurrence before treatment.

The thyroid hormone 3,3,5-triiodo-L-thyronine (T3) is essential for growth, differentiation, and development. Its biological activities are mediated by T3 nuclear receptors (TRs). At present, how T3 regulates TR proteins and the resulting functional consequences are still unknown. Immunofluorescence analyses of endogenous TR in the growth hormone-producing GC cells showed that the T3-induced rapid degradation of TR was specifically blocked by lactacystin, a selective inhibitor of the ubiquitin-proteasome degradation pathway. Immunoblots demonstrated that the transfected TR␤1 was ubiquitinated and that the ubiquitination was T3 independent. Studies with a series of truncated TR␤1 showed that the hormone-binding domain was sufficient for the T3-induced rapid degradation of TR␤1 by the proteasome degradation pathway. T3 also induced rapid degradation of TR␤2 and TR␣1. In contrast, the stability of the non-T3-binding TR␣2 and naturally occurring TR␤1 mutants that do not bind T3 was not affected by T3 treatment, indicating that hormone binding to receptor was essential for the degradation of the wild-type receptors. In the presence of proteasome protease inhibitors, the levels of both total and ubiquitinated TR␤1 protein increased, yet T3-dependent transcriptional activation and the expression of the growth hormone gene were diminished, suggesting that proteasome-mediated degradation played a novel role in modulating transcriptional activation by TR. The present study reveals a role of T3 in modulating the functions of TR by regulating its receptor level via the ubiquitin-proteasome degradation pathway. T he thyroid hormone 3,3Ј,5-triiodo-L-thyronine (T3) is essential in metabolic-energetic homeostasis, development, and differentiation. Its actions are mediated by thyroid hormone nuclear receptors (TRs), which regulate the expression of T3-targeted genes. TRs belong to a superfamily of hormone nuclear receptors functioning as ligand-activated transcription factors, which include receptors for steroid hormones, vitamin D3, and the retinoids (1). TR consists of domains including the Nterminal A͞B domain, the DNA-binding domain C, and the hormone-binding domain (domains D and E). Recent studies indicate that the transcriptional activity of TR depends not only on the type of the thyroid hormone response elements located on the promoter regions of T3 target genes but also on a host of corepressors and coactivators (2). In the absence of T3, TR binds to corepressors, such as N-CoR. Binding of T3 leads to the release of N-CoR from TR and recruitment of coactivators leading to gene activation (2). In this model, how TR proteins are regulated and the role of T3 in this process are unknown.Using biochemical methods, Samuels and Casanova have previously reported that T3 down-regulates its endogenous TR in growth hormone (GH)-producing GC cells (3). However, the underlying molecular mechanisms by which T3 downregulates the TR have not been elucidated. In this report, we demonstrated that the T3-induced degradation of TR was via ...

Background. Prediction and prevention of hepatitis B virus (HBV)-related

NFBD1/MDC1, which belongs to the BRCT superfamily, has an anti-apoptotic activity and contributes to the early cellular responses to DNA damage. Here we found that NFBD1 protects cells from apoptotic cell death by inhibiting phosphorylation of p53 at Ser-15 under steady state as well as early phase of DNA damage, thereby blocking its transcriptional and pro-apoptotic activities. During late phase of DNA damage, a remarkable reduction of NFBD1 was observed in dying but not in surviving A549 cells bearing wild-type p53. Small interference RNA-mediated knockdown of the endogenous NFBD1 resulted in an increase in sensitivity to adriamycin in A549 cells but not in p53-deficient H1299 cells. Immunoprecipitation and luciferase reporter analyses demonstrated that NFBD1 binds to the NH 2 -terminal region of p53 and strongly inhibits its transcriptional activity. Additionally, BRCT domains, which can interact with p53, reduced the adriamycin-induced phosphorylation levels of p53 at Ser-15 and also suppressed the transcriptional activity of p53. Thus, our present findings strongly suggest that NFBD1 plays an important role in the decision of cell survival and death after DNA damage through the regulation of p53. The BRCA1 carboxyl terminus (BRCT)3 domain is defined by distinct hydrophobic clusters of amino acids and is often found in a variety of cellular proteins such as BRCA1, 53BP1, and RAD9, which are involved in DNA repair and/or DNA damage signaling pathways (1-3). Although the functional role of the BRCT domain is currently unclear, the early works indicated that the BRCT domains of BRCA1 act as a transactivator (4, 5). Consistent with this notion, the point mutations detected within the BRCT domains of BRCA1 markedly inhibited its transcriptional activity (4, 5), and BRCA1 was a component of RNA polymerase II holoenzyme (6). Alternatively, the BRCT domains function as protein-protein interaction modules (7). For example, the BRCT domains of BRCA1 as well as 53BP1 were required for the interaction with p53 (8, 9). NFBD1/MDC1 (nuclear factor with BRCT domain 1/mediator of DNA damage checkpoint protein 1) is a large nuclear protein bearing three characteristic structural domains, including an NH 2 -terminal forkhead-associated (FHA) domain, an internal PST (proline/serine/threonine-rich) repeat domain, and tandem repeat of COOH-terminal BRCT domains (10 -14). We have initially reported that NFBD1 acts as a nuclear transcriptional factor with an anti-apoptotic function (11). In accordance with our results, siRNA-mediated knockdown of NFBD1 led to a significant increase in the number of apoptotic cells (15). In addition, the elimination of NFBD1 expression increased the sensitivity to irradiation (16). These observations indicate that NFBD1 has an anti-apoptotic function; however, the precise molecular mechanisms behind the anti-apoptotic effect of NFBD1 remain to be explored.Previous studies strongly suggest that NFBD1 is closely involved in early cellular responses to genotoxic stress. Upon DNA damage, NFBD1 was phosp...

8-OHdG is a risk factor for the development of HCC in patients with chronic HCV infection. Patients with chronic HCV who express 8-OHdG should be monitored carefully for the development of HCC.

I kappa B kinase (IKK) complex plays an important role in the regulation of signaling pathway that activates nuclear factor-kappa-B (NF-jB). Recently, we reported that cisplatin (CDDP) treatment causes a remarkable nuclear accumulation of IKK-a in association with stabilization and activation of p73. However, underlying mechanisms of CDDP-induced nuclear accumulation of IKK-a are elusive. Here, we found that ataxia-telangiectasia mutated (ATM) is one of upstream mediators of IKK-a during CDDP-induced apoptosis. In response to CDDP, ATM was phosphorylated at Ser-1981, which was accompanied with nuclear accumulation of IKK-a in HepG2 cells, whereas CDDP treatment had undetectable effects on IKK-a in ATM-deficient cells. Indirect immunofluorescence experiments demonstrated that phosphorylated form of ATM colocalizes with nuclear IKK-a in response to CDDP. In vitro kinase assay indicated that ATM phosphorylates IKK-a at Ser-473. Moreover, IKKa-deficient MEFs displayed CDDP-resistant phenotype as compared with wild-type MEFs. Taken together, our present results suggest that ATM-mediated phosphorylation of nuclear IKK-a, which stabilizes p73, is one of the main apoptotic pathways in response to CDDP.

No abstract

Heat shock factor 1 (HSF1), a major transactivator of stress responses, has been implicated in carcinogenesis in various organs. However, little is known about the biological functions of HSF1 in the development of hepatocellular carcinoma (HCC). To clarify the functional role of HSF1 in HCC, we established HSF1-knockdown (HSF1 KD) KYN2 HCC cells by stably expressing either small hairpin RNA (shRNA) against HSF1 (i.e. HSF1 KD) or control shRNA (HSF1 control). Tumorigenicity was significantly reduced in orthotopic mice with HSF1 KD cells compared with those with HSF1 control cells. Reduced tumorigenesis in HSF1 KD cells appeared attributable to increased apoptosis and decreased proliferation. Tumor necrosis factor-α-induced apoptosis was increased in HSF1 KD cells and HSF1(-/-) mouse hepatocytes compared with controls. Decreased expression of IκB kinase γ, a positive regulator of nuclear factor-κB, was also observed in HSF1 KD cells and HSF1(-/-) mouse hepatocytes. Furthermore, expression of bcl-2-associated athanogene domain 3 (BAG3) was dramatically reduced in HSF1 KD cells and HSF1(-/-) mouse hepatocytes. We also found that epidermal growth factor-stimulated mitogen-activated protein kinase signaling was impaired in HSF1 KD cells. Clinicopathological analysis demonstrated frequent overexpression of HSF1 in human HCCs. Significant correlations between HSF1 and BAG3 protein levels and prognosis were also observed. In summary, these results identify a mechanistic link between HSF1 and liver tumorigenesis and may provide as a potential molecular target for the development of anti-HCC therapies.