Reduced Expression of Fibroblast Growth Factor Receptor 2IIIb in Hepatocellular Carcinoma Induces a More Aggressive Growth

Glypicans are a family of heparan sulfate proteoglycans that are bound to the cell surface by a lipid anchor. Six members of this family have been identified in mammals (GPC1-GPC6). Glypicans act as regulators of the activity of various cytokines, including Wnts, Hedgehogs, and bone morphogenetic proteins. It has been reported that processing by a convertase is required for GPC3 activity during convergent extension in zebrafish embryos, for GPC3-induced regulation of Wnt signaling, and for the binding of GPC3 to Wnt5a. In our laboratory, we have recently demonstrated that GPC3 promotes the growth of hepatocellular carcinomas (HCCs) by stimulating canonical Wnt signaling. Because there is increasing evidence indicating that the structural requirements for GPC3 activity are cell type specific, we decided to investigate whether GPC3 needs to be processed by convertases to stimulate cell proliferation and Wnt signaling in HCC cells. We report here that a mutant GPC3 that cannot be processed by convertases is still able to play its stimulatory role in Wnt activity and HCC growth.

The immunobiology of hepatocellular carcinoma in humans and mice: Basic concepts and therapeutic implications

S-palmitoylation of PCSK9 induces sorafenib resistance in liver cancer by activating the PI3K/AKT pathway.

Notch signaling is a complex, highly conserved mechanism, originally discovered as critical regulator of cell fate determination during development in several tissues and organs.1,2 Activation of Notch may stimulate cells either to undergo a phenotypic switch or to maintain the original cell phenotype by preventing further differentiation,3 Notch is also involved in establishing organ-specific stem cell niches necessary for epithelial tissue homeostasis.3,4 The Notch system encompasses 4 genes encoding for different membrane receptors (Notch 1, 2, 3, and 4), which are activated by their binding to 5 ligands (Jagged-1, Jagged-2, and Delta-like 1, 3, and 4).4 Cell-to-cell contact is a prerequisite for the activation of Notch signaling.3,4 Whereas Notch receptors are expressed by the “receiver” cell, ligands are expressed by the “transmitter” cell. This interaction leads to the proteolytic cleavage and subsequent nuclear translocation of the intracellular domain of Notch receptors (NICD). Once migrated into the nucleus, NICD associates with the nuclear protein of the RBP-Jκ family and transcriptionally activates several other transcriptional activators or repressors that act as critical regulators of cell differentiation, apoptosis, and proliferation4 (see drawing on the left side of Figure 1). NICD is then rapidly deactivated by phosphorylation and by proteosomal degradation. The signal is maintained through ligand-induced proteolytic supply of new NICD.

The biological aggressiveness of hepatocellular carcinoma (HCC) and the lack of optimal therapeutic strategies have rendered the disease a major challenge. Highly heterogeneous genetic alteration profiles of HCC have made it difficult to identify effective tailor-made molecular therapeutic targets. Therefore, classification of HCC into genetically homogeneous subclasses would be of great worth to develop novel therapeutic strategies. We clarified genome-scale chromosomal copy number alteration profiles and mutational statuses of p53 and beta-catenin in 87 HCC tumors. We investigated the possibility that HCC might be classifiable into a number of homogeneous subclasses based solely on their genetic alteration profiles. We also explored putative molecular therapeutic targets specific for each HCC subgroup. Unsupervised hierarchical cluster analysis based on chromosomal alteration profiles suggested that HCCs with heterogeneous genetic backgrounds are divisible into homogeneous subclasses that are highly associated with a range of clinicopathologic features of the tumors and moreover with clinical outcomes of the patients (P < .05). These genetically homogeneous subclasses could be characterized distinctively by pathognomonic chromosomal amplifications (eg, c-Myc-induced HCC, 6p/1q-amplified HCC, and 17q-amplified HCC). An in vitro experiment raised a possibility that Rapamycin would significantly inhibit the proliferative activities of HCCs with 17q amplification. HCC is composed of several genetically homogeneous subclasses, each of which harbors characteristic genetic alterations that can be putative tailor-made molecular therapeutic targets for HCCs with specific genetic backgrounds. Our results offer an opportunity for developing novel individualized therapeutic modalities for distinctive genome types of HCC.

Ret, the receptor tyrosine kinase for the glial cell line-derived neurotrophic factor family ligands (GFLs), is alternatively spliced to yield at least two isoforms, Ret9 and Ret51, which differ only in their C termini. To identify tyrosines in Ret that are autophosphorylation sites in neurons, we generated antibodies specific to phosphorylated Y905Ret, Y1015Ret, Y1062Ret, and Y1096Ret, all of which are autophosphorylated in cell lines. All four of these tyrosines in Ret became phosphorylated rapidly upon activation by GFLs in sympathetic neurons. These tyrosines remained phosphorylated in sympathetic neurons in the continued presence of GFLs, albeit at a lower level than immediately after GFL treatment. Comparison of GFL activation of Ret9 and Ret51 revealed that phosphorylation of Tyr(905) and Tyr(1062) was greater and more sustained in Ret9 as compared with Ret51. In contrast, Tyr(1015) was more highly phosphorylated over time in Ret51 than in Ret9. Surprisingly, Ret9 and Ret51 did not associate with each other in sympathetic neurons after glial cell line-derived neurotrophic factor stimulation, even though they share identical extracellular domains. Furthermore, the signaling complex associated with Ret9 was markedly different from the Ret51-associated signaling complex. Taken together, these data provide a biochemical basis for the dramatic functional differences between Ret9 and Ret 51 in vivo.

Hepatocellular carcinoma (HCC) is the fifth most prevalent cancer worldwide and the third most lethal. Dysregulation of alternative splicing underlies a number of human diseases, yet its contribution to liver cancer has not been explored fully. The Krüppel-like factor 6 (KLF6) gene is a zinc finger transcription factor that inhibits cellular growth in part by transcriptional activation of p21. KLF6 function is abrogated in human cancers owing to increased alternative splicing that yields a dominant-negative isoform, KLF6 splice variant 1 (SV1), which antagonizes full-length KLF6-mediated growth suppression. The molecular basis for stimulation of KLF6 splicing is unknown. In human HCC samples and cell lines, we functionally link oncogenic Ras signaling to increased alternative splicing of KLF6 through signaling by phosphatidylinositol-3 kinase and Akt, mediated by the splice regulatory protein ASF/SF2. In 67 human HCCs, there is a significant correlation between activated Ras signaling and increased KLF6 alternative splicing. In cultured cells, Ras signaling increases the expression of KLF6 SV1, relative to full-length KLF6, thereby enhancing proliferation. Abrogation of oncogenic Ras signaling by small interfering RNA (siRNA) or a farnesyl-transferase inhibitor decreases KLF6 SV1 and suppresses growth. Growth inhibition by farnesyl-transferase inhibitor in transformed cell lines is overcome by ectopic expression of KLF6 SV1. Down-regulation of the splice factor ASF/SF2 by siRNA increases KLF6 SV1 messenger RNA levels. KLF6 alternative splicing is not coupled to its transcriptional regulation. Our findings expand the role of Ras in human HCC by identifying a novel mechanism of tumor-suppressor inactivation through increased alternative splicing mediated by an oncogenic signaling cascade.

Transcriptional regulators in hepatocarcinogenesis – Key integrators of malignant transformation

Enhanced Expression of Keratinocyte Growth Factor and Its Receptor Correlates with Venous Invasion in Pancreatic Cancer

miR-122 acts as a tumor suppressor in hepatocarcinogenesis in vivo

The X protein (HBx) of hepatitis B virus (HBV) is involved in the development of hepatocellular carcinoma (HCC), and methionine adenosyltransferase 2A (MAT2A) promotes the growth of liver cancer cells through altering S-adenosylmethionine homeostasis. Thus, we speculated that a link between HBx and MAT2A may contribute to HCC development. In this study, the effects of HBx on MAT2A expression and cell apoptosis were investigated, and the molecular mechanism by which HBx and MAT2A regulate tumorigenesis was evaluated. Results from immunohistochemistry analyses of 37 pairs of HBV-associated liver cancer tissues/corresponding peritumor tissues showed that HBx and MAT2A are highly expressed in most liver tumor tissues. Our in vitro results revealed that HBx activates MAT2A expression in a dose-dependent manner in hepatoma cells, and such regulation requires the cis-regulatory elements NF-κB and CREB on the MAT2A gene promoter. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) further demonstrated that HBx facilitates the binding of NF-κB and CREB to MAT2A gene promoter. In addition, overexpression of HBx or MAT2A inhibits cell apoptosis, whereas knockdown of MAT2A expression stimulates apoptosis in hepatoma cells. Furthermore, we demonstrated that HBx reduces MAT1A expression and AdoMet production but enhances MAT2β expression. Thus, we proposed that HBx activates MAT2A expression through NF-κB and CREB signaling pathways to reduce AdoMet production, inhibit hepatoma cell apoptosis, and perhaps enhance HCC development. These findings should provide new insights into our understanding how the molecular mechanisms underline the effects of HBV infection on the production of MAT2A and the development of HCC.

The Mutational and Transcriptional Landscapes of Hepatocarcinogenesis in a Rat Model.

Vascular endothelial growth factor and liver regeneration

Hepatitis B Virus X Protein and Pin1 in Liver Cancer: “Les Liaisons Dangereuses”

New technological developments have frequently preceded major advances in biomedical research and medicine [1]. For example, the development of fluorescent DNA sequencing techniques made it possible to establish the large-scale high-throughput technology needed for human genome sequencing. Polymerase chain reaction (PCR), fluorescent DNA sequencing, and other techniques have enabled the discovery of about 1700 mendelian disease genes [2]. The advent of the DNA microarray based technologies has now made it possible to measure simultaneously the expression of tens of thousands of genes in different tissues under a variety of conditions. This high-throughput technology has afforded biomedical scientists a unique opportunity to integrate the descriptive characteristics (i.e. ‘phenotype’) of a biological system under study with the genomic readout (i.e. gene expression). The opportunity to contemplate the integrated view of biological systems has provoked a shift in biological sciences away from the classical reductionism to systems biology [1,3,4]. The systems approach to a disease is based on the hypothesis that disease processes perturb a regulatory network of genes and proteins in a way that differs from the respective normal counterpart. Consequently, by using multi-parametric measurements it may be possible to transform current diagnostic and therapeutic approaches and enable a predictive and preventive personalized medicine [4]. The application of microarray technologies to characterize tumors at the gene expression level has significantly impacted clinical oncology [5,6]. Global gene expression analysis of various human tumors has resulted in