Hepatocellular carcinoma (HCC) is a highly malignant tumor with a poor prognosis. Treatment of HCC is complicated by the fact that the disease is often diagnosed at an advanced stage when it is no longer amenable to curative surgery, and current systemic chemotherapeutics are mostly inefficacious. Sirtuin 1 (SIRT1) is a class III histone deacetylase that is implicated in gene regulations and stress resistance. In this study, we found that SIRT1 is essential for the tumorigenesis of HCC. We showed that although SIRT1 was expressed at very low levels in normal livers, it was overexpressed in HCC cell lines and in a subset of HCC. Tissue microarray analysis of HCC and adjacent nontumoral liver tissues revealed a positive correlation between the expression levels of SIRT1 and advancement in tumor grades. Downregulation of SIRT1 consistently suppressed the proliferation of HCC cells via the induction of cellular senescence or apoptosis. SIRT1 silencing also caused telomere dysfunction-induced foci and nuclear abnormality that were clearly associated with reduced expressions of telomerase reverse transcriptase (TERT), and PTOP, which is a member of the shelterin complex. Ectopic expression of either TERT or PTOP in SIRT1-depleted cells significantly restored cell proliferation. There was also a positive correlation between the level of induction of SIRT1 and PTOP in human HCC. Finally, SIRT1-silencing sensitized HCC cells to doxorubicin treatment. Together, our findings reveal a novel function for SIRT1 in telomere maintenance of HCC, and they rationalize the clinical exploration of SIRT1 inhibitors for HCC therapy.

Sirtuin 1 (SIRT1) has been implicated in telomere maintenance and the growth of hepatocellular carcinoma (HCC). Nevertheless, the role of other sirtuins in the pathogenesis of HCC remains elusive. We found that sirtuin 2 (SIRT2), another member of the sirtuin family, also contributes to cell motility and invasiveness of HCC. SIRT2 is up-regulated in HCC cell lines and in a subset of human HCC tissues (23/45). Up-regulations of SIRT2 in primary HCC tumors were significantly correlated with the presence of microscopic vascular invasion (P 5 0.001), a more advanced tumor stage (P 5 0.004), and shorter overall survival (P 5 0.0499). Functional studies by short hairpin RNA-mediated suppression of SIRT2 expression in HCC cell lines revealed significant inhibition of motility and invasiveness. Depletion of SIRT2 also led to the regression of epithelial-mesenchymal transition (EMT) phenotypes, whereas the ectopic expression of SIRT2 in the immortalized hepatocyte cell line L02 promoted cell motility and invasiveness. Mechanistic studies revealed that SIRT2 regulates the deacetylation and activation of protein kinase B, which subsequently impinges on the glycogen synthase kinase-3b/b-catenin signaling pathway to regulate EMT. Conclusions: Our findings have uncovered a novel role for SIRT2 in HCC metastasis, and provide a rationale to explore the use of sirtuin inhibitors in HCC therapy.

Epstein-Barr virus (EBV) latency gene expression in lymphoblastoid cell lines is regulated by EBNA2.However, the factors regulating viral expression in EBV-associated tumors that do not express EBNA2 are poorly understood. In EBV-associated tumors, EBNA1 and frequently LMP1 are synthesized. We found that an alternative latent membrane protein 1 (LMP1) promoter, L1-TR, located within the terminal repeats is active in both nasopharyngeal carcinoma and Hodgkin's disease tissues. Examination of the L1-TR and the standard ED-L1 LMP1 promoters in electrophoretic mobility shift assays revealed that both promoters contain functional STAT binding sites. Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that, after primary exposure, maintains a latent infection for the life of the individual. Approximately 1 to 50 per 10 6 circulating B cells in healthy seropositive individuals carry the EBV genome, and the site of long-term latency has been identified as the G 0 memory B cell (39). EBV infection elicits a strong immune response (44), and in general viral persistence is controlled by the host and is asymptomatic. However, one consequence of lifelong infection is the potential for the development of EBV-associated malignancies, which include Burkitt's lymphoma, nasopharyngeal carcinoma (NPC), Hodgkin's disease, lymphoproliferative disease in immunocompromised patients, primary central nervous system lymphoma in AIDS patients, nasal T-cell lymphoma, a subset of gastric carcinoma, and possibly also a subset of primary liver and breast cancers (2, 3, 43, 51).On initial EBV infection, and in latently infected lymphoblastoid cell lines in culture, the full spectrum of EBV latency genes is expressed. The Wp promoter, which is regulated by B-cell-specific factors, is responsible for the initial transcription of the nuclear EBNAs, EBNA1, EBNA2, EBNA3A, EBNA3B, EBNA3C, and EBNA-LP (32). EBNA2, which functions as a transcriptional activator, then enforces a switch to Cp promoter-driven EBNA synthesis and also regulates synthesis of the LMP1 and LMP2 latency membrane proteins. However, EBNA2 is detected in EBV-associated malignancies only in the context of immunosuppression, presumably because the Cp-driven EBNA3 family proteins elicit a robust CD8 cell-mediated immune response (44). In EBV-associated tumors in immunocompetent patients, the Cp is repressed by methylation (1, 41). An alternative TATA-less promoter, Qp (40,46), is used to express EBNA1 in the absence of the immunogenic EBNAs, and LMP1 is also frequently expressed. EBNA1 binds to the origin of latent DNA replication, oriP, and is required for maintainance of the episomal form of the latent EBV genome (35,42,60). LMP1, an integral membrane protein, is essential for EBV-driven B-cell immortalization and induces transformation in primary Rat1 cells (56). The transforming ability of LMP1 is explicable in large part by its functioning as a constituitively activated tumor necrosis factor (TNF) receptor that mimics signaling by the B-lymphocyte activation antigen CD4...

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Significant febrile reactions after platelet transfusion are highly likely to be indicative of bacteremia. Routine retention of platelet bags for subsequent microbiologic study was useful in the investigation of these febrile reactions. Empiric antibiotic therapy is indicated.

c-Met represents an important emerging therapeutic target in cancer. Here, we demonstrate the mechanism by which c-Met tyrosine kinase inhibition inhibits tumor growth in a highly invasive Asian-prevalent head and neck cancer, nasopharyngeal cancer (NPC). c-Met tyrosine kinase inhibitors (TKIs; AM7 and c-Met TKI tool compound SU11274) downregulated c-Met phosphorylation resulting in markedly inhibited growth and invasion of NPC cells. Strikingly, inhibition of c-Met resulted in marked downregulation of TIGAR (TP53-induced Glycolysis and Apoptosis Regulator) and subsequent depletion of intracellular NADPH. Importantly, overexpression of TIGAR ameliorated the effects of c-Met kinase inhibition, confirming the importance of TIGAR downregulation in growth inhibition induced by c-Met TKI. The effects of c-Met inhibition on TIGAR and NADPH levels were observed with two different c-Met TKIs (AM7 and SU11274) and with multiple cell lines. As NADPH provides a crucial reducing power required for cell survival and proliferation, our findings represent a novel mechanistic action of c-Met TKI, which may represent a key effect of c-Met kinase inhibition. Our data provides the first evidence linking c-Met, TIGAR and NADPH regulation in human cancer cells suggesting that inhibition of a tyrosine kinase/TIGAR/NADPH cascade may have therapeutic applicability in human cancers.

Epigenetic disruption of tumor suppressor genes is frequently involved in tumorigenesis. We identified a novel 19q13 KRAB domain-containing zinc finger protein, ZNF545/ZFP82, broadly expressed in normal tissues but downregulated in multiple tumor cell lines. The ZNF545 promoter contains a CpG island, which is frequently methylated in cell lines. The transcriptional silencing of ZNF545 could be reversed by pharmacologic or genetic demethylation, indicating direct epigenetic silencing. ZNF545 was also frequently methylated in multiple primary tumors of nasopharyngeal, esophageal, lung, gastric, colon, and breast, but rarely in normal epithelial tissues and paired normal tissues. ZNF545 is located in the nucleus and mainly sequestered in nucleoli, functioning as a repressor. ZNF545 is able to repress NF-kB and AP-1 signaling pathways, whereas ectopic expression of ZNF545 in silenced tumor cells significantly inhibited their growth and induced apoptosis. Functional studies showed that ZNF545 was involved in ribosome biogenesis through inhibiting the activity of rDNA promoter and decreasing cellular protein translation efficiency. Thus, we identified ZNF545 as a novel tumor suppressor inducing tumor cell apoptosis, repressing ribosome biogenesis and target gene transcription. The tumor-specific methylation of ZNF545 could be an epigenetic biomarker for cancer diagnosis. Mol Cancer Res; 10(7); 925-36. Ó2012 AACR.