Dysregulation of growth factor signaling in human hepatocellular carcinoma

Capacitative calcium entry and transient receptor potential canonical 6 expression control human hepatoma cell proliferation

Store-operated calcium entry (SOCE) is the main Ca(2+) influx pathway involved in controlling proliferation of the human hepatoma cell lines Huh-7 and HepG2. However, the molecular nature of the calcium channels involved in this process remains unknown. Huh-7 and HepG2 cells express transient receptor potential canonical 1 (TRPC1) and TRPC6, as well as STIM1 and Orai1, and these 4 channels are the most likely candidates to account for the SOCE in these cells. We generated stable TRPC6-overexpressing or TRPC6-knockdown Huh-7 clones, in which we investigated correlations between the presence of the protein, the rate of cell proliferation, and SOCE amplitude. TRPC6-overexpressing Huh-7 cells proliferated 80% faster than did untransfected cells and their SOCE amplitude was 160% higher. By contrast, proliferation rate was 50% lower and SOCE amplitude 85% lower in TRPC6-knockdown clones than in untransfected cells. OAG (olyl acetyl glycerol)-induced calcium entry was similar in all cells, and small interfering RNA (siRNA) against TRPC1 had no effect on SOCE amplitude, highlighting the relationship among SOCE, TRPC6 and cell proliferation in Huh-7 cells. SOCE amplitude was reduced by STIM1 and Orai1 knockdowns, suggesting possible cooperation between these proteins and TRPC6 in these cells. Endothelial growth factor and hepatocyte growth factor increased TRPC6 expression and SOCE amplitude in Huh-7 cells, and cyclin D1 expression was decreased by STIM1, Orai1, and TRPC6 knockdowns.

CONCLUSION

TRPC6 was very weakly expressed in isolated hepatocytes from healthy patients and expressed more strongly in tumoral samples from the liver of a cancer patient, strongly supporting a role for these calcium channels in liver oncogenesis.

Blocking transforming growth factor-beta up-regulates E-cadherin and reduces migration and invasion of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) treatment is challenging because the mechanisms underlying tumor progression are still largely unknown. Transforming growth factor (TGF)-beta1 is considered a crucial molecule in HCC tumorigenesis because increased levels of patients' serum and urine are associated with disease progression. The aim of the present study was to investigate the inhibition of TGF-beta signaling and its impact on HCC progression. Human HCC cell lines were treated with a TGF-beta receptor kinase inhibitor (LY2109761) whose selectivity was determined in a kinase assay. Exogenous TGF-beta1 phosphorylates the TGF-beta receptor, consequently activating Smad-2, whereas the drug selectively blocks this effect and dephosphorylates autocrine p-Smad-2 at concentrations ranging from 0.001 to 0.1 microM. A cytotoxic effect documented by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), trypan blue, and propidium iodide staining assays was observed at 10microM, whereas the drug inhibits (P < 0.001) the migration of HCC cells on fibronectin, laminin-5, and vitronectin and invasion through Matrigel (P < 0.001) at concentrations up to 0.1 microM. LY2109761 up-regulates (P < 0.001) E-cadherin mRNA and protein levels. This increase was localized at the cellular membrane where E-cadherin mediates anchorage that is cell-cell dependent. Consistently, a functional monoclonal antibody that inhibits E-cadherin-dependent cell-cell contact restores the migratory and invasive activity. Finally, nonmetastatic HCC tissues from 7 patients were cultured with TGF-beta1 in the presence or absence of LY2109761. E-cadherin expression was reduced by TGF-beta1 and was significantly (P < 0.0001) increased by LY2109761 treatment, measured by quantitative real-time PCR on microdissected tissues and by immunohistochemistry on serial sections. In 72 patients, E-cadherin tissue expression was more weakly expressed in metastatic than in nonmetastatic HCC (P < 0.0001).

CONCLUSION

LY2109761 blocks migration and invasion of HCC cells by up-regulating E-cadherin, suggesting that there could be a mechanistic use for this molecule in clinical trials.

Experimental models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common and deadly cancer whose pathogenesis is incompletely understood. Comparative genomic studies from human HCC samples have classified HCCs into different molecular subgroups; yet, the unifying feature of this tumor is its propensity to arise upon a background of inflammation and fibrosis. This review seeks to analyze the available experimental models in HCC research and to correlate data from human populations with them in order to consolidate our efforts to date, as it is increasingly clear that different models will be required to mimic different subclasses of the neoplasm. These models will be instrumental in the evaluation of compounds targeting specific molecular pathways in future preclinical studies.

Lead identification to generate isoquinolinedione inhibitors of insulin-like growth factor receptor (IGF-1R) for potential use in cancer treatment

Insulin-like growth factor receptor (IGF-1R) is a growth factor receptor tyrosine kinase that acts as a critical mediator of cell proliferation and survival. This receptor is over-expressed or activated in tumor cells and is emerging as a novel target in cancer therapy. Efforts in our "Hit to Lead" group have generated a novel series of submicromolar IGF-1R inhibitors based on a isoquinolinedione template originating from a Lance enzyme HTS screen. Chemical triage and parallel synthesis incorporating focused library arrays were instrumental in moving these investigations through the Wyeth exploratory medicinal chemistry process. The strategies, synthesis, and SAR behind this interesting kinase scaffold will be described.

Involvement of Egr-1 in HGF-induced elevation of the human 5alpha-R1 gene in human hepatocellular carcinoma cells

Steroid 5alpha-reductase 1 (5alpha-R1), a key enzyme in the conversion of steroids into their respective 5alpha-reduced derivatives, plays a key role in some hormone-dependent tumours and is abundant in the liver, although it is also widely distributed throughout the body. HGF (hepatocyte growth factor) is a pleiotropic cytokine/growth factor involved in the progression of hepatocellular carcinoma. In the present paper, we report the stimulatory effect of HGF on human 5alpha-R1 transcription in hepatocellular carcinoma cells. Pre-treatment with actinomycin D or cycloheximide blocked the up-regulation of 5alpha-R1 mRNA expression by HGF, indicating that the increased level of 5alpha-R1 mRNA expression is regulated by transcriptional activation and was dependent on de novo protein synthesis. Functional analysis of the 5'-flanking region of the 5alpha-R1 gene by transfection analysis showed that the -79 to -50 region functioned as the HGF-responsive region. Mutagenesis and electrophoretic mobility-shift assays demonstrated that induction of 5a-R1 by HGF is mediated by an Egr-1 (early growth-response gene 1)-binding site at -60/-54. In addition, overexpression of Egr-1 was sufficient to transactivate 5alpha-R1 promoter activity, and knockdown of Egr-1 with gene-specific small interfering RNA resulted in inhibition of HGF-induced up-regulation of endogenous 5alpha-R1 expression. These data provide the first evidence that HGF stimulates 5alpha-R1 expression through up-regulation of the transcription factor Egr-1, thus suggesting the possibility that regulation of steroid metabolism by HGF represents a mechanism for high risk of hepatocellular carcinogenesis in males.

Different signaling pathways expressed by chicken naive CD4(+) T cells, CD4(+) lymphocytes activated with staphylococcal enterotoxin B, and those malignantly transformed by Marek's disease virus

Proteomics methods, based on liquid chromatography and tandem mass spectrometry, produce large "shotgun" proteomes that are most appropriately compared not at the level of differentially expressed proteins only but at the more comprehensive level of biological networks and pathways. This is now possible with the emergence of functional annotation databases and tools, databases of canonical pathways and molecular interactions and computational text mining tools. Here, we used shotgun proteomics, and the differential proteomics modeling functionalities available in the Pathwaystudio network modeling program to define the cell physiology of Hodgkin's disease antigen-overexpressing (CD30 (hi)) CD4 (+) T cell lymphomas using the unique Marek's disease (MD) natural animal model. CD30 (hi) lymphoma cells have characteristics of activated T cells but are also fundamentally different from their nontransformed healthy counterparts. We compared the cell physiology of naïve, superantigen-activated and MD-transformed CD4 (+) T cell proteomes. While the superantigen-activated cells had signaling pathways associated with cell activation, inflammation, proliferation and cell death, the MD-transformed cells had growth factor, cytokine, adhesion, and transcription factor signaling responses associated with oncogenicity, cell proliferation, angiogenesis, motility, and metastasis.

Hepatocarcinoma in viral and metabolic liver disease

It is becoming increasingly evident that children, like adults, with chronic viral or metabolic liver diseases are at risk for the development of hepatocarcinoma. The aims of this article are to review the risk factors for hepatocarcinoma in chronic viral or metabolic liver disease, outline potential pathogenic mechanisms of hepatocarcinoma, and describe surveillance strategies, clinical evaluation, and management of hepatocarcinoma in children.

[Epidemiology, risk factors and molecular pathogenesis of primary liver cancer]

Primary liver cancer is the fifth most common cancer worldwide. Hepatocellular carcinoma accounts for 85-90% of primary liver cancers. Distribution of hepatocellular carcinoma shows variations among geographic regions and ethnic groups. Males have higher liver cancer rates than females. Hepatocellular carcinoma occurs within an established background of chronic liver disease and cirrhosis (70-90%). Major causes (80%) of hepatocellular carcinoma are hepatitis B, C virus infection, and aflatoxin exposition. Its development is a multistep process. We have a growing understanding on the molecular pathogenesis. Genetic and epigenetic changes activate oncogenes, inhibit tumorsuppressor genes, which result in autonomous cell proliferation. The chromosomal instability caused by telomere dysfunction, the growth-retrained environment and the alterations of the micro- and macroenvironment help the expansion of the malignant cells. Understanding the molecular mechanisms could improve the screening of patients with chronic liver disease, or cirrhosis, and the prevention as well as treatment of hepatocellular carcinoma.

Activins and activin antagonists in hepatocellular carcinoma

In many parts of the world hepatocellular carcinoma (HCC) is among the leading causes of cancer-related mortality but the underlying molecular pathology is still insufficiently understood. There is increasing evidence that activins, which are members of the transforming growth factor β (TGFβ) superfamily of growth and differentiation factors, could play important roles in liver carcinogenesis. Activins are disulphide-linked homo- or heterodimers formed from four different β subunits termed βA, βB, βC, and βE, respectively. Activin A, the dimer of two βA subunits, is critically involved in the regulation of cell growth, apoptosis, and tissue architecture in the liver, while the hepatic function of other activins is largely unexplored so far. Negative regulators of activin signals include antagonists in the extracellular space like the binding proteins follistatin and FLRG, and at the cell membrane antagonistic co-receptors like Cripto or BAMBI. Additionally, in the intracellular space inhibitory Smads can modulate and control activin activity. Accumulating data suggest that deregulation of activin signals contributes to pathologic conditions such as chronic inflammation, fibrosis and development of cancer. The current article reviews the alterations in components of the activin signaling pathway that have been observed in HCC and discusses their potential significance for liver tumorigenesis.

Reactivation of the insulin-like growth factor-II signaling pathway in human hepatocellular carcinoma

Constitutive activation of the insulin-like growth factor (IGF)-signaling axis is frequently observed in human hepatocellular carcinoma (HCC). Especially the overexpression of the fetal growth factor IGF-II, IGF-Ireceptor (IGF-IR), and cytoplasmic downstream effectors such as insulin-receptor substrates (IRS) contribute to proliferation, anti-apoptosis, and invasive behavior. This review focuses on the relevant alterations in this signaling pathway and independent in vivo models that support the central role IGF-II signaling during HCC development and progression. Since this pathway has become the center of interest as a target for potential anti-cancer therapy in many types of malignancies, various experimental strategies have been developed, including neutralizing antibodies and selective receptor kinase inhibitors, with respect to the specific and efficient reduction of oncogenic IGF-II/IGF-IR-signaling.

Effects of hepatitis B virus X protein (HBx) on cell-growth inhibition in a CCL13-HBx stable cell line

OBJECTIVE

The known function of hepatitis B virus X protein (HBx) is to determine the fate of cells by modulating various signaling pathways. In our previous study, we demonstrated that HBx inhibits tumor formation in nude mice injected with CCL13-HBx stable cell lines; however, the mechanism underlying this inhibition is unclear.

METHODS

To investigate the possible mechanisms underlying HBx involvement in CCL13-HBx cells, gene profiles were initially analyzed by DNA microarray technology and subsequently confirmed by performing semiquantitative RT-PCR and Western blotting. Furthermore, the phenomenon of cell death via apoptosis was detected via DNA fragmentation, TUNEL staining, caspase-3 activity assay, and propidium iodide (PI) staining.

RESULTS

The results indicated that HBx induction downregulated Wnt-3 and beta-catenin that are involved in cell proliferation. Moreover, HBx induction repressed cell growth and downregulated the expressions of cyclin D1, CDK4, cyclin E, CDK2, and cyclin B1. Furthermore, HBx induction triggered cell death via apoptosis, as determined by DNA fragmentation, TUNEL staining, caspase-3 activity assay, and PI staining.

CONCLUSION

Most importantly, our results indicated that HBx induction in the CCL13-HBx stable cell line downregulated Wnt-3/beta-catenin expression and suppressed cell growth by repressing cell proliferation or triggering cell apoptosis.

Inhibition of IGF receptor signaling and hepatoma cell growth by an antibody to ligand oligopeptide of receptor

Research on insulin-like growth factor (IGF) system have shown it to be potent mitogen for hepatoma cells and made it an attractive therapeutic target. But little strategy has been reported to date on targeting and sequestrating IGF against hepatoma. This study is based on the capability of ligand oligopeptide (LOP) to recognize IGF receptor with high efficiency, which is over-expressed on some hepatoma cells. We have been hypothesizing that antibody to LOP would mimic the extracellular ligand-binding domain of IGF receptor and inhibit receptor signaling and cell proliferation. Gene encoding for LOP [E5 (EPFRSPDLALETYG)] of IGF receptor was inserted into HBc carrier for expression in Escherichia coli. The monoclonal antibody (mAb) specific LOP potently inhibited signal transduction mediated by the IGF-IR interaction with IGF-I. Furthermore, it exhibited 47% inhibitory rate of soft agar colony formation and also induced apoptosis. These results indicate an anti-hepatoma potential of the mAb to an LOP of IGF receptor could block the activation of receptor and downstream signaling pathways, and suppress the biological effects mediated by receptor.

Association of gankyrin protein expression with early clinical stages and insulin-like growth factor-binding protein 5 expression in human hepatocellular carcinoma

Gankyrin (also known as PSMD10) is a liver oncoprotein that interacts with multiple proteins including MDM2 and accelerates degradation of the tumor suppressors p53 and Rb. We produced a monoclonal anti-gankyrin antibody and immunohistochemically assessed the clinicopathological significance of gankyrin overexpression in 43 specimens of human hepatocellular carcinoma (HCC). Specific cytoplasmic staining for gankyrin was observed in 62.8% (27/43) of HCCs, which was significantly associated with low TNM stage (P = 0.004), no capsular invasion (P = 0.018), no portal venous invasion (P = 0.008), and no intrahepatic metastasis (P = 0.012). The cumulative survival rate of patients with gankyrin-positive HCC was significantly higher than that with gankyrin-negative HCC (P = 0.037). p53 and MDM2 were positively stained by antibodies in 30.2% and 23.3%, respectively, of HCCs, but neither was inversely associated with gankyrin expression. In the Huh-7 human HCC cell line, overexpression of gankyrin up-regulated expression of insulin-like growth factor binding protein 5 (IGFBP-5), whereas suppression of gankyrin expression by siRNA down-regulated it. Supression of IGFBP-5 expression inhibited proliferation of Huh-7 cells as well as U-2 OS osteosarcoma cells. In HCC specimens, positive staining for IGFBP-5 was observed by immunohistochemistry in 41.9% (18/43), and the level of expression was significantly correlated with that of gankyrin (rho = 0.629, P < 0.001).

CONCLUSION

These results suggest that gankyrin plays an oncogenic role(s) mainly at the early stages of human hepatocarcinogenesis, and that IGFBP-5 inducible by gankyrin overexpression may be involved in it.

Demonstration of cooperative contribution of MET- and EGFR-mediated STAT3 phosphorylation to liver regeneration by exogenous suppressor of cytokine signalings

BACKGROUND/AIMS

As conditional knockout mice for stat3 are impaired in liver regeneration after partial hepatectomy while those for gp130 have defects in early STAT3 phosphorylation but have normal DNA synthesis, late STAT3 phosphorylation induced independently of gp130 seems to be essential for liver regeneration. Since HGF and EGF can activate STAT3 via gp130-independent MET and EGFR, respectively, we assumed that these factors account for STAT3-dependent liver regeneration. Here, we investigated this hypothesis by introducing suppressor of cytokine signaling (SOCS)-1 and SOCS3, potent negative regulators of STAT3 signaling, selectively in hepatocytes.

METHODS

We generated recombinant adenoviruses expressing socs1 and socs3.

RESULTS

Hepatocytes infected with socs1-virus lacked STAT3 phosphorylation in response to IL-6 and HGF, while cells infected with socs3-virus lacked the response to all of IL-6, HGF and EGF, indicating that those SOCS proteins differently regulate EGFR signaling. Mice infected with socs3-virus exhibited severe and persistent impairment while those with socs1-virus showed only delayed regeneration, indicating requirement of both MET and EGFR signalings.

CONCLUSIONS

These results clearly demonstrated that MET- and EGFR-mediated STAT3 signalings cooperatively contribute to liver regeneration and could provide new insights into tissue homeostasis.

Development of hepatocellular carcinoma in Iqgap2-deficient mice is IQGAP1 dependent

IQGAPs are multidomain scaffolding proteins that integrate Rho GTPase and Ca2+/calmodulin signals with cell adhesive and cytoskeletal reorganizational events. Targeted disruption of the murine Iqgap2 gene resulted in the age-dependent development of apoptosis and hepatocellular carcinoma (HCC), characterized by the overexpression of IQGAP1, the loss of membrane E-cadherin expression, the cytoplasmic translocation (and activation) of beta-catenin, and the overexpression of a nuclear target of beta-catenin, cyclin D1. In normal hepatocytes, IQGAP2 was found to exist as one component of a multifunctional scaffolding complex comprising IQGAP1, beta-catenin, and E-cadherin, with no evidence for direct IQGAP1-IQGAP2 interactions. Interbreeding of Iqgap2(-/-) mice into the Iqgap1(-/-) background resulted in the phenotypic correction of the preexisting hepatopathy, decreases in the incidence and sizes of HCC tumors, and the normalization of overall survival rates compared to those of Iqgap2(-/-) mice, suggesting that maximal penetrance of the Iqgap2(-/-) HCC phenotype requires the coordinate expression of IQGAP1. These results identify Iqgap2 as a novel tumor suppressor gene specifically linked to the development of HCC and the activation of the Wnt/beta-catenin signaling pathway, while also suggesting that IQGAP1 and IQGAP2 retain functionally divergent roles in hepatocellular carcinogenesis.

Laminin-5 stimulates hepatocellular carcinoma growth through a different function of alpha6beta4 and alpha3beta1 integrins

Hepatocellular carcinoma (HCC) growth severely affects prognosis. Ki-67, a known marker of cell proliferation, is a negative prognostic factor in HCC. Growth factors such as the epidermal growth factor (EGF) induce HCC cell proliferation but do not explain the great heterogeneity of HCC growth. Laminin-5 (Ln-5) is an extracellular matrix protein (ECM) present in the tissue microenvironment of HCC. The two main receptors for Ln-5, integrins alpha3beta1 and alpha6beta4, are expressed on the cell surface of HCC cells. The aim of this study is to investigate an alternative mechanism of HCC growth whereby Ln-5 promotes HCC cell proliferation through alpha3beta1 and alpha6beta4. HCC tissues containing Ln-5 display a larger diameter and higher number of positive cells for Ki-67, a well known proliferative index, as determined by double immunofluorescence staining and real-time PCR on microdissected tissues. In vitro, Ln-5, but not collagen I, collagen IV or fibronectin, induces proliferation as much as EGF does, via Erk phosphorylation as a consequence of beta4 integrin phosphorylation. However, the two HCC cell lines do not proliferate in presence of Ln-5 despite beta4 integrin and Erk1/2 activation. After transfection with alpha3 integrin, in the presence of Ln-5 one of these HCC cell lines acquires a proliferative activity whereas one of the proliferative HCC cell lines, knocked-down for alpha3 integrin, loses its proliferative activity.

CONCLUSIONS

Our study suggests a new mechanism of HCC growth whereby Ln-5 stimulates proliferation via a different function of alpha6beta4 and alpha3beta1.

The EGF receptor is required for efficient liver regeneration

Mice lacking the EGF receptor (EGFR) die between midgestation and postnatal day 20 with various defects in neural and epithelial organs. Here, we generated mice carrying a floxed EGFR allele to inactivate the EGFR in fetal and adult liver. Perinatal deletion of EGFR in hepatocytes resulted in decreased body weight, whereas deletion in the adult liver did not affect body mass. Although liver function was not affected, after partial hepatectomy mice lacking EGFR in the liver showed increased mortality accompanied by increased levels of serum transaminases indicating liver damage. Liver regeneration was delayed in the mutants because of reduced hepatocyte proliferation. Analysis of cell cycle progression in EGFR-deficient livers indicated a defective G(1)-S phase entry with delayed transcriptional activation and reduced protein expression of cyclin D1 followed by reduced cdk2 and cdk1 expression. Impaired liver regeneration was accompanied by compensatory up-regulation of TNFalpha in the serum and prolonged activation of c-Jun. Moreover, p38alpha and NF-kappaB activation was reduced in regenerating mutant livers, indicating an impaired stress response after hepatectomy. Our studies demonstrate that EGFR is a critical regulator of hepatocyte proliferation in the initial phases of liver regeneration.

Arecoline-induced growth arrest and p21WAF1 expression are dependent on p53 in rat hepatocytes

Betel-quid use is associated with the risk of liver cirrhosis and hepatocellular carcinoma and arecoline, the major alkaloid of betel-quid, is hepatotoxic in mice. Therefore, we studied the cytotoxic and genotoxic effects of arecoline in normal rat hepatocytes (Clone-9 cells). Arecoline dose-dependently (0.1-1mM) decreased cell cycle-dependent proliferation while inducing DNA damage at 24h. Moreover, arecoline (1mM)-induced apoptosis and necrosis at 24h. Arecoline dose-dependently (0.1-0.5mM) increased transforming growth factor-beta (TGF-beta) mRNA, gene transcription and bioactivity and neutralizing TGF-beta antibody attenuated arecoline (0.5mM)-inhibited cell proliferation at 24h. Arecoline (0.5mM) also increased p21(WAF1) protein expression and p21(WAF1) gene transcription. Moreover, arecoline (0.5mM) time-dependently (8-24h) increased p53 serine 15 phosphorylation. Pifithrin-alpha (p53 inhibitor) and the loss of the two p53-binding elements in the p21(WAF1) gene promoter attenuated arecoline-induced p21(WAF1) gene transcription at 24h. Pifithrin-alpha also attenuated arecoline (0.5mM)-inhibited cell proliferation at 24h. We concluded that arecoline induces cytotoxicity, DNA damage, G(0)/G(1) cell cycle arrest, TGF-beta1, p21(WAF1) and activates p53 in Clone-9 cells. Moreover, arecoline-induced p21(WAF1) is dependent on p53 while arecoline-inhibited growth is dependent on both TGF-beta and p53.

Amphiregulin: A new growth factor in hepatocarcinogenesis

Amphiregulin (AR) is a member of the epidermal growth factor family and a ligand of the epidermal growth factor receptor (EGFR). As other ligands of the EGFR, AR is synthesized as a precursor that is shed from the plasma membrane by metalloproteases. Hyperactive autocrine loops involving AR production have been described in a variety of tumors, and this growth factor is thought to play a non-redundant role in cancer development. AR expression is not detected in the normal liver, however it is readily induced during acute liver injury and behaves as a potent pro-regenerative and survival factor. Increased AR expression is also detected in human chronic liver injury (liver cirrhosis), which is considered a pre-neoplastic condition. Recent evidences suggest that AR can play a unique role in liver tumorigenesis and in the maintenance of the neoplastic phenotype of hepatocarcinoma cells. In this review, we summarize some aspects of AR patho-biology and the rationale behind its definition as a novel target in hepatocarcinoma therapy.

Wnt Signaling, Stem Cells, and the Cellular Origin of Breast Cancer

The breast epithelium comprises cells at different stages of differentiation, including stem cells, progenitor cells, and more differentiated epithelial and myoepithelial cells. Wnt signaling plays a critical role in regulating stem/progenitor cells in the mammary gland as well as other tissue compartments. Furthermore, there is strong evidence suggesting that aberrant activation of Wnt signaling induces mammary tumors from stem/progenitor cells, and that Wnt exerts its oncogenic effects through LRP5/6-mediated activation of beta-catenin and mTOR pathways. Recent studies using avian retrovirus-mediated introduction of oncogenes into a small subset of somatic mammary cells suggest that polyoma middle T antigen (PyMT) may also preferentially transform stem/progenitor cells. These observations suggest that stem/progenitor cells in the mammary gland may be especially susceptible to oncogenic transformation. Whether more differentiated cells may also be transformed by particular oncogenes is actively debated; it is presently unclear whether stem cells or differentiated mammary cells are more susceptible to transformation by individual oncogenes. Better stem cell and progenitor cell markers as well as the ability to specifically target oncogenes into different mammary cell types will be needed to determine the spectrum of oncogene transformation for stem cells versus more differentiated cells.

Disruption of transforming growth factor-beta signaling through beta-spectrin ELF leads to hepatocellular cancer through cyclin D1 activation

Transforming growth factor-beta (TGF-beta) signaling members, TGF-beta receptor type II (TBRII), Smad2, Smad4 and Smad adaptor, embryonic liver fodrin (ELF), are prominent tumor suppressors in gastrointestinal cancers. Here, we show that 40% of elf(+/-) mice spontaneously develop hepatocellular cancer (HCC) with markedly increased cyclin D1, cyclin-dependent kinase 4 (Cdk4), c-Myc and MDM2 expression. Reduced ELF but not TBRII, or Smad4 was observed in 8 of 9 human HCCs (P<0.017). ELF and TBRII are also markedly decreased in human HCC cell lines SNU-398 and SNU-475. Restoration of ELF and TBRII in SNU-398 cells markedly decreases cyclin D1 as well as hyperphosphorylated-retinoblastoma (hyperphosphorylated-pRb). Thus, we show that TGF-beta signaling and Smad adaptor ELF suppress human hepatocarcinogenesis, potentially through cyclin D1 deregulation. Loss of ELF could serve as a primary event in progression toward a fully transformed phenotype and could hold promise for new therapeutic approaches in human HCCs.

Biología celular y genética en el cáncer de hígado

Hepatocellular carcinoma (HCC) is the main cause of death in cirrhotic patients and has become a major health problem in developed countries. Analysis of the somatic alterations and gene expression profiles in patients with HCC have provided important information the genes involved in liver carcinogenesis. Nevertheless, the most important molecular alterations in the initial stages of the disease are currently unknown. The application of high resolution technologies to other forms of cancer (genome analysis with oligo microarrays and SNP arrays) should lead to greater insight into the pathogenesis of this neoplasm. In the last few years, distinct signaling pathways involved in hepatocarcinogenesis have been identified. Among these, the Wnt, EGFR and PI3k/akt/mTOR pathways are constitutively altered in numerous studies, providing the molecular basis for the molecular treatment of this tumor. As in other neoplasms, the original tumor cell in HCC is controversial. The most widely accepted hypothesis suggests that numerous genomic alterations in the hepatocyte cells lead to a neoplastic phenotype. Alternatively, it has been postulated that at least a subgroup of tumors could be of stem cell origin. Both hypotheses agree on the existence of cancer stem cells, arising from the original tumor cell; these cancer stem cells would then perpetuate and disseminate the neoplasm. This review summarizes the most important information on the structural and functional alterations in HCC and describes some of the main signaling pathways implicated in liver cancer.

Hepatocyte growth factor at S phase induces G2 delay through sustained ERK activation

The effect of growth factors on the cell cycle progression, except G1/S transition, is poorly understood. Herein, we examined the effect of hepatocyte growth factor (HGF) treated at S phase on the cell cycle progression of HeLa cells. Interestingly, the treatment resulted in G2 delay, evidenced by flow cytometric and mitotic index analyses. The delay corresponded with the delay of degradation of cyclin A and cyclin B, and the delay of decrease of Cdk1/cyclin B and Cdk2/cyclin A kinase activities. As for the signaling responsible, sustained activation of ERK, but neither of p38MAPK nor of JNK, was observed after HGF treatment at S phase. Furthermore, U0126, an inhibitor of MEK1, and DN-MEK partially abrogated the G2 delay, indicating that activation of MEK-ERK pathway is involved. Taken together, HGF treatment of HeLa cells at S phase induces G2 delay partially through sustained activation of ERK signaling.

New molecular targets for hepatocellular carcinoma: the ErbB1 signaling system

Hepatocellular carcinoma (HCC) is a major cause of cancer-related deaths. This malignancy is often diagnosed at an advanced state, when most potentially curative therapies are of limited efficacy. In addition, HCC is a type of tumor highly resistant to available chemotherapeutic agents, which leaves HCC patients with no effective therapeutic options and a poor prognosis. From a molecular perspective, HCC is a heterogeneous type of tumor. However, in most cases, HCC emerges on a background of persistent liver injury, inflammation and hepatocellular proliferation, which is characteristic of chronic hepatitis and cirrhosis. Recent studies have revealed that dysregulation of a limited number of growth and survival-related pathways can play a key role in HCC development. The epidermal growth factor receptor (ErbB1) can be bound and activated by a broad family of ligands, and can also engage in extensive cross talk with other signaling pathways. This system is considered as an important defense mechanism for the liver during acute tissue injury; however, accumulating evidences suggest that its chronic stimulation can participate in the neoplastic conversion of the liver. Agents that target the ErbB1 receptor have shown antineoplastic activity in other types of tumors, but their efficacy either alone or in combination with other compounds has just started to be tested in experimental and human HCC. Here, we review the evidences that support the involvement of the ErbB1 in HCC development and that provide a rationale for ErbB1 targeting in HCC prevention and treatment.

Survival and apoptosis: a dysregulated balance in liver cancer

BACKGROUND/AIMS

Dysregulation of the balance between proliferation and cell death represents a protumorigenic principle in human hepatocarcinogenesis. This article aims to provide a review of the current findings about how physiological hepatocyte apoptosis is regulated and whether or not its dysregulation might contribute to the progression towards a hepatocellular carcinoma (HCC) process.

RESULTS

Although some physiological proapoptotic molecules are downregulated or inactivated in HCC, such as Fas, p53, Bax or Bid, dysregulation of the balance between death and survival is mainly due to overactivation of antiapoptotic signals. Thus, some growth factors that mediate cell survival are upregulated in HCC, as well as the molecules involved in the machinery responsible for cleavage of their proforms to an active peptide. The expression of the pten gene is reduced or absent in almost half the HCCs and the Spred family of Ras/ERK inhibitors is also dysregulated in HCC, which consequently lead to the overactivation of relevant survival kinases: AKT and ERKs. Alterations in the expression and/or activity of molecules involved in counteracting apoptosis, such as NF-kappaB, Bcl-X(L), Mcl-1 or c-IAP1, have also been observed in HCC.

CONCLUSIONS

Therefore, therapeutic strategies to inhibit selectively antiapoptotic signals in tumour cells have the potential to provide powerful tools to treat liver cancer.

Nitric oxide in the pathogenesis of diffuse pulmonary fibrosis

By studying the responses of nitric oxide in pulmonary fibrosis, the role of inducible nitric oxide synthase in diffuse pulmonary fibrosis as caused by lipopolysaccharide (LPS) treatment was investigated. When compared to rats treated with LPS only, the rats pretreated with 1400W (an iNOS-specific inhibitor) were found to exhibit a reduced level in: (i) NOx (nitrate/nitrite) production, (ii) collagen type I protein expression, (iv) soluble collagen production, and (iv) the loss of body weight and carotid artery PO2. In the pulmonary fibroblast culture, exogenous NO from LPS-stimulated secretion by macrophages or from a NO donor, such as DETA NONOate, was observed to induce the expression of TIMP-1, HSP47, TGF-beta1, and collagen type I as well as the phosphorylation of SMAD-2. After inhalation of NO for 24 h, an up-regulation of collagen type I protein was also noted to occur in rat pulmonary tissue. The results suggest that the NO signal pathway enhanced the expression of TGF-beta1, TIMP-1, and HSP47 in pulmonary fibroblasts, which collectively demonstrate that the NO signal pathway could activate the SMAD-signal cascade, by initiating a rapid increase in TGF-beta1, thereby increasing the expression of TIMP-1 and HSP47 in pulmonary fibroblasts, and play an important role in pulmonary fibrosis.

Application of genomic biomarkers to predict increased lung tumor incidence in 2-year rodent cancer bioassays

Rodent cancer bioassays are part of a legacy of safety testing that has not changed significantly over the past 30 years. The bioassays are expensive, time consuming, and use hundreds of animals. Fewer than 1500 chemicals have been tested in a rodent cancer bioassay compared to the thousands of environmental and industrial chemicals that remain untested for carcinogenic activity. In this study, we used existing data generated by the National Toxicology Program (NTP) to identify gene expression biomarkers that can predict results from a rodent cancer bioassay. A set of 13 diverse chemicals was selected from those tested by the NTP. Seven chemicals were positive for increased lung tumor incidence in female B6C3F1 mice and six were negative. Female mice were exposed subchronically to each of the 13 chemicals, and microarray analysis was performed on the lung. Statistical classification analysis using the gene expression profiles identified a set of eight probe sets corresponding to six genes whose expression correctly predicted the increase in lung tumor incidence with 93.9% accuracy. The sensitivity and specificity were 95.2 and 91.8%, respectively. Among the six genes in the predictive signature, most were enzymes involved in endogenous and xenobiotic metabolism, and one gene was a growth factor receptor involved in lung development. The results demonstrate that increases in chemically induced lung tumor incidence in female mice can be predicted using gene biomarkers from a subchronic exposure and may form the basis of a more efficient and economical approach for evaluating the carcinogenic activity of chemicals.

Hepatocellular expression of glutamine synthetase: an indicator of morphogen actions as master regulators of zonation in adult liver

Glutamine synthetase (GS) has long been known to be expressed exclusively in pericentral hepatocytes most proximal to the central veins of liver lobuli. This enzyme as well as its peculiar distribution complementary to the periportal compartment for ureogenesis plays an important role in nitrogen metabolism, particularly in homeostasis of blood levels of ammonium ions and glutamine. Despite this fact and intensive studies in vivo and in vitro, many aspects of the regulation of its activity on the protein and on the genetic level remained enigmatic. Recent experimental advances using transgenic mice and new analytic tools have revealed the fundamental role of morphogens such as wingless-type MMTV integration site family member signals (Wnt), beta-catenin, and adenomatous polyposis coli in the regulation of this particular enzyme. In addition, novel information concerning the structure of transcription factor binding sites within regulatory regions of the GS gene and their interactions with signalling pathways could be collected. In this review we focus on all aspects of the regulation of GS in the liver and demonstrate how the new findings have changed our view of the determinants of liver zonation. What appeared as a simple response of hepatocytes to blood-derived factors and local cellular interactions must now be perceived as a fundamental mechanism of adult tissue patterning by morphogens that were considered mainly as regulators of developmental processes. Though GS may be the most obvious indicator of morphogen action among many other targets, elucidation of the complex regulation of the expression of the GS gene could pave the road for a better understanding of the mechanisms involved in patterning of liver parenchyma. Based on current knowledge we propose a new concept of how morphogens, hormones and other factors may act in concert, in order to restrict gene expression to small subpopulations of one differentiated cell type, the hepatocyte, in different anatomical locations. Although many details of this regulatory network are still missing, and an era of exciting new discoveries is still about to come, it can already be envisioned that similar mechanisms may well be active in other organs contributing to the fine-tuning of organ-specific functions.

Right hepatic lobectomy in elderly patients with hepatocellular carcinoma

BACKGROUND/AIMS

The outcome of hepatectomy in elderly patients with hepatocellular carcinoma have been reported, however neither the morphological nor functional hepatic regeneration in elderly patients have been fully investigated.

MATERIALS AND METHODS

Fifty-six patients with hepatocellular carcinoma, who underwent a right hepatic lobectomy over an 8-year period, were classified into three groups according to their age; group 1 (n = 7), more than 70 years of age; group 2 (n = 40), patients from 50 to 69 years of age and group 3 (n = 9), under 50 years of age. There were no significant differences regarding backgrounds or intra-operative parameters among the three groups. The perioperative hepatic function, postoperative complications and the regeneration rate of the remnant left lobe at 1 month after operation were compared.

RESULTS

No differences were found in the regeneration rate, however, the levels of the hepaplastin test and lecithin:cholesterol acyltransferase at 7 days after hepatectomy in group 1 (31.3%, 8.8 U) were significantly lower than those in groups 2 and 3 (37.4%, 18.4 U; 47.9%, 29.4 U, respectively). The incidence of hospital death due to hepatic failure in group 1 (42.9%) was also significantly higher than that of group 2 (5.0%) or group 3 (0%).

CONCLUSION

The decline of postoperative protein synthesis regardless of the voluminal regeneration is a characteristic of the elderly. This phenomenon might thus be an important promoter of postoperative hepatic failure which remains unpredictable using any type of examination. Therefore, at this time, a major hepatectomy is not recommended as a viable treatment alternative in the elderly.