A novel prognostic subtype of human hepatocellular carcinoma derived from hepatic progenitor cells

Hippo Signaling in the Liver Regulates Organ Size, Cell Fate, and Carcinogenesis

The Hippo signaling pathway, also known as the Salvador-Warts-Hippo pathway, is a regulator of organ size. The pathway takes its name from the Drosophila protein kinase, Hippo (STK4/MST1 and STK3/MST2 in mammals), which, when inactivated, leads to considerable tissue overgrowth. In mammals, MST1 and MST2 negatively regulate the transcriptional co-activators yes-associated protein 1 and WW domain containing transcription regulator 1 (WWTR1/TAZ), which together regulate expression of genes that control proliferation, survival, and differentiation. Yes-associated protein 1 and TAZ activation have been associated with liver development, regeneration, and tumorigenesis. How their activity is dynamically regulated in these contexts is just beginning to be elucidated. We review the mechanisms of Hippo signaling in the liver and explore outstanding questions for future research.

Curcumin and Turmeric Modulate the Tumor-Promoting Effects of Iron In Vitro

Free or loosely chelated iron has tumor-promoting properties in vitro. Curcumin, a polyphenol derived from the food spice turmeric (Curcuma longa), is a potent antioxidant that binds iron. The primary aim of this study was to investigate whether curcuminoids prevent tumor-promoting effects of iron in T51B cells, a non-neoplastic rat liver epithelial cell line. Purified curcuminoids (curcumin) or a standardized turmeric extract similarly reduced oxidative stress and cytotoxicity associated with iron overload (IC₅₀ values near 10 μM, P < 0.05). Inhibition of iron-induced tumor promotion (seen upon treatment with 200 μM ferric ammonium citrate ± curcumin/turmeric for 16 wk in culture; subsequently assayed by soft agar colony formation) was nearly complete at 20 μM of total curcuminoids (P < 0.05), a concentration predicted to only partially chelate the added iron. Surprisingly, lower curcumin concentrations (10 μM) increased tumor promotion (P < 0.01). Curcuminoids delivered as a standardized turmeric extract were taken up better by cells, had a longer half-life, and appeared more effective in blocking tumor promotion (P < 0.01), suggesting enhanced curcuminoid delivery to cells in culture. The primary finding that curcuminoids can inhibit tumor promotion caused by iron in T51B cells is tempered by evidence for an underlying increase in neoplastic transformation at lower concentrations.

Systemic treatment for hepatocellular carcinoma: Still unmet expectations

Many patients with hepatocellular carcinoma (HCC) are diagnosed in an advanced stage, so they cannot be offered the option of curative treatments. The results of systemic chemotherapy are unsatisfactory and this has led to molecular targeted approaches. HCC develops in chronically damaged tissue due to cirrhosis in most patients. Several different cell types and molecules constitute a unique microenvironment in the liver, which has significant implications in tumor development and invasion. This, together with genome instability, contributes to a significant heterogeneity which is further enhanced by the molecular differences of the underlying causes. New classifications based on genetic characteristics of the tissue microenvironment have been proposed and key carcinogenic signaling pathways have been described. Tumor and adjacent tissue profiling seem biologically promising, but have not yet been translated into clinical settings. The encouraging first results with molecular - genetic signatures should be validated and clinically applicable. A more personalized approach to modern management of HCC is urgently needed.

Cytokeratin19 positive hepatocellular carcinoma is associated with increased peritumoral ductular reaction

BACKGROUND AND AIMS

Cytokeratin19 positive (CK19+) hepatocellular carcinoma (HCC) is thought to derive from liver progenitor cells (LPC). However, whether peritumoralductular reaction (DR) differs between CK19+ and CK19 negative (CK19-) HCC patients remains unclear.

MATERIAL AND METHODS

One hundred and twenty HBV-related HCC patients were enrolled in this study. Clinicopathological variables were collected, and immunohistochemistry staining for CK19, proliferating cell nuclear antigen (PCNA), interleukin-6 (IL-6) and β-catenin were performed in tumor and peritumor liver tissues.

RESULTS

CK19+ HCC patients had higher grade of peritumoral DR and proportion of proliferative DR than the CK19- group. The mean number or the proportion of cytoplasmic β-catenin+ DR was higher in the CK19+ group than in the CK19- group. Furthermore, there were more patients with nuclear β-catenin+ peritumoral DR in the CK19+ group as compared to the CK19- group.

CONCLUSION

Peritumoral DR was more abundant and proliferative in CK19+ HCC patients, with higher level of nuclear translocation of β-catenin. However, it is unclear whether peritumoral DR is the cause or result of poor prognosis in these patients.

Genomic analysis of hepatoblastoma identifies distinct molecular and prognostic subgroups

Despite being the most common liver cancer in children, hepatoblastoma (HB) is a rare neoplasm. Consequently, few pretreatment tumors have been molecularly profiled, and there are no validated prognostic or therapeutic biomarkers for HB patients. We report on the first large-scale effort to profile pretreatment HBs at diagnosis. Our analysis of 88 clinically annotated HBs revealed three risk-stratifying molecular subtypes that are characterized by differential activation of hepatic progenitor cell markers and metabolic pathways: high-risk tumors were characterized by up-regulated nuclear factor, erythroid 2-like 2 activity; high lin-28 homolog B, high mobility group AT-hook 2, spalt-like transcription factor 4, and alpha-fetoprotein expression; and high coordinated expression of oncofetal proteins and stem-cell markers, while low-risk tumors had low lin-28 homolog B and lethal-7 expression and high hepatic nuclear factor 1 alpha activity.

CONCLUSION

Analysis of immunohistochemical assays using antibodies targeting these genes in a prospective study of 35 HBs suggested that these candidate biomarkers have the potential to improve risk stratification and guide treatment decisions for HB patients at diagnosis; our results pave the way for clinical collaborative studies to validate candidate biomarkers and test their potential to improve outcome for HB patients. (Hepatology 2017;65:104-121).

Circadian Homeostasis of Liver Metabolism Suppresses Hepatocarcinogenesis

Chronic jet lag induces spontaneous hepatocellular carcinoma (HCC) in wild-type mice following a mechanism very similar to that observed in obese humans. The process initiates with non-alcoholic fatty liver disease (NAFLD) that progresses to steatohepatitis and fibrosis before HCC detection. This pathophysiological pathway is driven by jet-lag-induced genome-wide gene deregulation and global liver metabolic dysfunction, with nuclear receptor-controlled cholesterol/bile acid and xenobiotic metabolism among the top deregulated pathways. Ablation of farnesoid X receptor dramatically increases enterohepatic bile acid levels and jet-lag-induced HCC, while loss of constitutive androstane receptor (CAR), a well-known liver tumor promoter that mediates toxic bile acid signaling, inhibits NAFLD-induced hepatocarcinogenesis. Circadian disruption activates CAR by promoting cholestasis, peripheral clock disruption, and sympathetic dysfunction.

Programmed death ligand 1 expression in hepatocellular carcinoma: Relationship With clinical and pathological features

The prognosis of hepatocellular carcinoma (HCC) remains poor, with only one third of patients eligible for curative treatments and very limited survival benefits with the use of sorafenib, the current standard of care for advanced disease. Recently, agents targeting the programmed death ligand 1 (PD-L1)/programmed death receptor 1 (PD-1) immune checkpoint were shown to display impressive antitumor activity in various solid or hematological malignancies, including HCC. PD-L1 immunohistochemical expression is thought to represent a biomarker predictive of drug sensitivity. Here, we investigated PD-L1 expression in a series of 217 HCCs and correlated our results with clinical and histological features and immunohistochemical markers (PD-1, cytokeratin 19, glutamine synthetase, and β-catenin expression). PD-L1 expression by neoplastic cells was significantly associated with common markers of tumor aggressiveness (high serum alpha-fetoprotein levels, P = 0.038; satellite nodules, P < 0.001; macrovascular invasion, P < 0.001; microvascular invasion, P < 0.001; poor differentiation, P < 0.001) and with the progenitor subtype of HCC (cytokeratin 19 expression, P = 0.031). High PD-L1 expression by inflammatory cells from the tumor microenvironment also correlated with high serum alpha-fetoprotein levels (P < 0.001), macrovascular invasion (P = 0.001), poor differentiation (P = 0.001), high PD-1 expression (P < 0.001), and the so-called lymphoepithelioma-like histological subtype of HCC (P = 0.003).

CONCLUSION

PD-L1 expression by either neoplastic or intratumoral inflammatory cells is related to tumor aggressiveness and suggests that the response to treatments targeting the PD-L1/PD-1 immune checkpoint could be restricted to particular HCC variants; thus, enrichment of these tumor subtypes in future clinical trials should be considered. (Hepatology 2016;64:2038-2046).

Transcriptional Induction of Periostin by a Sulfatase 2-TGFβ1-SMAD Signaling Axis Mediates Tumor Angiogenesis in Hepatocellular Carcinoma

Existing antiangiogenic approaches to treat metastatic hepatocellular carcinoma (HCC) are weakly effectual, prompting further study of tumor angiogenesis in this disease setting. Here, we report a novel role for sulfatase 2 (SULF2) in driving HCC angiogenesis. Sulf2-deficient mice (Sulf2 KO) exhibited resistance to diethylnitrosamine-induced HCC and did not develop metastases like wild-type mice (Sulf2 WT). The smaller and less numerous tumors formed in Sulf2 KO mice exhibited a markedly lower microvascular density. In human HCC cells, SULF2 overexpression increased endothelial proliferation, adhesion, chemotaxis, and tube formation in a paracrine fashion. Mechanistic analyses identified the extracellular matrix protein periostin (POSTN), a ligand of αvβ3/5 integrins, as an effector protein in SULF2-induced angiogenesis. POSTN silencing in HCC cells attenuated SULF2-induced angiogenesis and tumor growth in vivo The TGFβ1/SMAD pathway was identified as a critical signaling axis between SULF2 and upregulation of POSTN transcription. In clinical HCC specimens, elevated levels of SULF2 correlated with increased microvascular density, POSTN levels, and relatively poorer patient survival. Together, our findings define an important axis controlling angiogenesis in HCC and a mechanistic foundation for rational drug development. Cancer Res; 77(3); 632-45. ©2016 AACR.

Cancer stem cells in hepatocellular carcinoma--an immunohistochemical study with histopathological association

Background & objectives:

Cancer stem cells (CSCs) may be responsible for tumour recurrence and resistance to chemotherapy in hepatocellular carcinoma (HCC). This study was carried out to evaluate the association between histological parameters and liver CSCs (LCSC) in HCC, and to compare distribution of liver CSCs in HCC associated with and without hepatitis B virus (HBV) infection.

Methods:

Seventy nine tumours (49 surgical resections from 46 patients, and 30 from autopsy) were reviewed. Immunohistochemical staining for the LCSC marker EpCAM (epithelial cell adhesion molecule), liver progenitor cell (LPC) markers CK19 (cytokeratin 19) and neural cell adhesion molecule (NCAM) were performed and were associated with histological features of tumour behaviour.

Results:

Thirty three tumours (41.8%) showed positive staining for EpCAM. CK19 and NCAM expression were seen in 26 (32.9%) and four (5.1%) tumours, respectively. The expression of EpCAM and CK19 was significantly associated with each other (P<0.001). EpCAM expression was significantly associated with clinical and histological features indicating aggressive tumour behaviour, including younger age of onset, higher serum alpha foetoprotein (AFP) levels, tumour cell dedifferentiation, increased mitotic activity, and vascular invasiveness. There was no significant difference in expression of EpCAM, CK19 and NCAM between HBV positive and negative HCC.

Interpretation & conclusions:

The LCSC marker EpCAM was expressed in less than half of HCC, was independent of HBV aetiology, and was strongly associated with clinical and histological features of aggressive tumour behaviour. Positive staining for CK19 suggests a possible LPC origin of the EpCAM positive HCCs.

KLHL21, a novel gene that contributes to the progression of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) has very high prevalence and associated-mortality. However, targeted therapies that are currently used in clinical practice for HCC have certain limitations, in part because of the lack of reliable and clinically applicable biomarkers that can be used for diagnosis and prognosis assessments and for the surveillance of treatment effectiveness.

METHODS

Meta-analysis was used to analyze the integrated microarray data for global identification of a set of robust biomarkers for HCC. Quantitative RT-PCR (qRT-PCR) was performed to validate the expression levels of selected genes. Gene expression was inhibited by siRNA. CellTiter 96^® AQueous One Solution Cell Proliferation assays were used to determine cell proliferation, and Transwell assays were used to determine cell migration and invasion potential.

RESULTS

Meta-analysis of the expression data provided a gene expression signature from a total of 1525 patients with HCC, showing 1529 up-regulated genes and 478 down-regulated genes in cancer samples. The expression levels of genes having strong clinical significance were validated by qRT-PCR using primary HCC tissues and the paired adjacent noncancerous liver tissues. Up-regulation of VPS45, WIPI1, TTC1, IGBP1 and KLHL21 genes and down-regulation of FCGRT gene were confirmed in clinical HCC samples. KLHL21 was the most promising gene for potential use as a bioclinical marker in this analysis. Abrogating expression of it significantly inhibited cell proliferation, migration and invasion.

CONCLUSIONS

Our study suggests that KLHL21 is a potential target for therapeutic intervention. Our findings also provide novel candidate genes on a genome-wide scale, which may have significant impact on the design and execution of effective therapy of HCC patients.

Cytokeratin-19 positivity is acquired along cancer progression and does not predict cell origin in rat hepatocarcinogenesis

Although the expression of the stem/progenitor cell marker cytokeratin-19 (CK-19) has been associated with the worst clinical prognosis among all HCC subclasses, it is yet unknown whether its presence in HCC is the result of clonal expansion of hepatic progenitor cells (HPCs) or of de-differentiation of mature hepatocytes towards a progenitor-like cell phenotype. We addressed this question by using two rat models of hepatocarcinogenesis: the Resistant-Hepatocyte (R-H) and the Choline-methionine deficient (CMD) models. Our data indicate that the expression of CK-19 is not the result of a clonal expansion of HPCs (oval cells in rodents), but rather of a further step of preneoplastic hepatocytes towards a less differentiated phenotype and a more aggressive behavior. Indeed, although HCCs were positive for CK-19, very early preneoplastic foci (EPFs) were completely negative for this marker. While a few weeks later the vast majority of preneoplastic nodules remained CK-19 negative, a minority became positive, suggesting that CK-19 expression is the result of de-differentiation of a subset of EPFs, rather than a marker of stem/progenitor cells. Moreover, the gene expression profile of CK-19-negative EPFs clustered together with CK-19-positive nodules, but was clearly distinct from CK-19 negative nodules and oval cells.

Genomic Adequacy from Solid Tumor Core Needle Biopsies of ex Vivo Tissue and in Vivo Lung Masses: Prospective Study

Purpose To identify the variables and factors that affect the quantity and quality of nucleic acid yields from imaging-guided core needle biopsy. Materials and Methods This study was approved by the institutional review board and compliant with HIPAA. The authors prospectively obtained 232 biopsy specimens from 74 patients (177 ex vivo biopsy samples from surgically resected masses were obtained from 49 patients and 55 in vivo lung biopsy samples from computed tomographic [CT]-guided lung biopsies were obtained from 25 patients) and quantitatively measured DNA and RNA yields with respect to needle gauge, number of needle passes, and percentage of the needle core. RNA quality was also assessed. Significance of correlations among variables was assessed with analysis of variance followed by linear regression. Conditional probabilities were calculated for projected sample yields. Results The total nucleic acid yield increased with an increase in the number of needle passes or a decrease in needle gauge (two-way analysis of variance, P < .0001 for both). However, contrary to calculated differences in volume yields, the effect of needle gauge was markedly greater than the number of passes. For example, the use of an 18-gauge versus a 20-gauge biopsy needle resulted in a 4.8-5.7 times greater yield, whereas a double versus a single pass resulted in a 2.4-2.8 times greater yield for 18- versus 20-gauge needles, respectively. Ninety-eight of 184 samples (53%) had an RNA integrity number of at least 7 (out of a possible score of 10). Conclusion With regard to optimizing nucleic acid yields in CT-guided lung core needle biopsies used for genomic analysis, there should be a preference for using lower gauge needles over higher gauge needles with more passes. ^©RSNA, 2016 Online supplemental material is available for this article. An earlier incorrect version of this article appeared online. This article was corrected on October 21, 2016.

A Transcriptomic Signature of Mouse Liver Progenitor Cells

Liver progenitor cells (LPCs) can proliferate extensively, are able to differentiate into hepatocytes and cholangiocytes, and contribute to liver regeneration. The presence of LPCs, however, often accompanies liver disease and hepatocellular carcinoma (HCC), indicating that they may be a cancer stem cell. Understanding LPC biology and establishing a sensitive, rapid, and reliable method to detect their presence in the liver will assist diagnosis and facilitate monitoring of treatment outcomes in patients with liver pathologies. A transcriptomic meta-analysis of over 400 microarrays was undertaken to compare LPC lines against datasets of muscle and embryonic stem cell lines, embryonic and developed liver (DL), and HCC. Three gene clusters distinguishing LPCs from other liver cell types were identified. Pathways overrepresented in these clusters denote the proliferative nature of LPCs and their association with HCC. Our analysis also revealed 26 novel markers, LPC markers, including Mcm2 and Ltbp3, and eight known LPC markers, including M2pk and Ncam. These markers specified the presence of LPCs in pathological liver tissue by qPCR and correlated with LPC abundance determined using immunohistochemistry. These results showcase the value of global transcript profiling to identify pathways and markers that may be used to detect LPCs in injured or diseased liver.

Regulation of Transdifferentiation and Retrodifferentiation by Inflammatory Cytokines in Hepatocellular Carcinoma

Liver cancers are typically inflammation-associated cancers characterized by close communication between the tumor cells and the tumor environment. This supportive inflammatory environment contributes to the establishment of a pathologic niche consisting of transformed epithelial cells, tumor-educated fibroblasts, endothelial cells, and immunosuppressive immature myeloid cells. Stromal and infiltrated immune cells help determine tumor fate, but the tumor cells themselves, including cancer stem cells, also influence the surrounding cells. This bidirectional communication generates an intricate network of signals that promotes tumor growth. Cell plasticity, which includes transdifferentiation and retrodifferentiation of differentiated cells, increases tumor heterogeneity. Plasticity allows non-cancer stem cells to replenish the cancer stem cell pool, initiate tumorigenesis, and escape the effects of therapeutic agents; it also promotes tumor aggressiveness. There is increasing evidence that an inflammatory environment promotes the retrodifferentiation of tumor cells into stem or progenitor cells; this could account for the low efficacies of some chemotherapies and the high rates of cancer recurrence. Increasing our understanding of the signaling network that connects inflammation with retrodifferentiation could identify new therapeutic targets, and lead to combined therapies that are effective against highly heterogeneous tumors.

Development and Validation of a Six-Gene Recurrence Risk Score Assay for Gastric Cancer

PURPOSE

This study was aimed at developing and validating a quantitative multigene assay for predicting tumor recurrence after gastric cancer surgery.

EXPERIMENTAL DESIGN

Gene expression data were generated from tumor tissues of patients who underwent surgery for gastric cancer (n = 267, training cohort). Genes whose expression was significantly associated with activation of YAP1 (a frequently activated oncogene in gastrointestinal cancer), 5-year recurrence-free survival, and 5-year overall survival were first identified as candidates for prognostic genes (156 genes, P < 0.001). We developed the recurrence risk score (RRS) by using quantitative RT-PCR to identify genes whose expression levels were significantly associated with YAP1 activation and patient survival in the training cohort.

RESULTS

We based the RRS assay on 6 genes, IGFBP4, SFRP4, SPOCK1, SULF1, THBS, and GADD45B, whose expression levels were significantly associated with YAP1 activation and prognosis in the training cohort. The RRS assay was further validated in an independent cohort of 317 patients. In multivariate analysis, the RRS was an independent predictor of recurrence [HR, 1.6; 95% confidence interval (CI), 1.02-2.4; P = 0.03]. In patients with stage II disease, the RRS had an HR of 2.9 (95% CI, 1.1-7.9; P = 0.03) and was the only significant independent predictor of recurrence.

CONCLUSIONS

The RRS assay was a valid predictor of recurrence in the two cohorts of patients with gastric cancer. Independent prospective studies to assess the clinical utility of this assay are warranted. Clin Cancer Res; 22(24); 6228-35. ©2016 AACR.

Integrative Genomic Analysis Identifies the Core Transcriptional Hallmarks of Human Hepatocellular Carcinoma

Integrative genomics helped characterize molecular heterogeneity in hepatocellular carcinoma (HCC), leading to targeted drug candidates for specific HCC subtypes. However, no consensus was achieved for genes and pathways commonly altered in HCC. Here, we performed a meta-analysis of 15 independent datasets (n = 784 human HCC) and identified a comprehensive signature consisting of 935 genes commonly deregulated in HCC as compared with the surrounding nontumor tissue. In the HCC signature, upregulated genes were linked to early genomic alterations in hepatocarcinogenesis, particularly gains of 1q and 8q. The HCC signature covered well-established cancer hallmarks, such as proliferation, metabolic reprogramming, and microenvironment remodeling, together with specific hallmarks associated with protein turnover and epigenetics. Subsequently, the HCC signature enabled us to assess the efficacy of signature-relevant drug candidates, including histone deacetylase inhibitors that specifically reduced the viability of six human HCC cell lines. Overall, this integrative genomics approach identified cancer hallmarks recurrently altered in human HCC that may be targeted by specific drugs. Combined therapies targeting common and subtype-specific cancer networks may represent a relevant therapeutic strategy in liver cancer. Cancer Res; 76(21); 6374-81. ©2016 AACR.

Heat Stress-Induced PI3K/mTORC2-Dependent AKT Signaling Is a Central Mediator of Hepatocellular Carcinoma Survival to Thermal Ablation Induced Heat Stress

Thermal ablative therapies are important treatment options in the multidisciplinary care of patients with hepatocellular carcinoma (HCC), but lesions larger than 2–3 cm are plagued with high local recurrence rates and overall survival of these patients remains poor. Currently no adjuvant therapies exist to prevent local HCC recurrence in patients undergoing thermal ablation. The molecular mechanisms mediating HCC resistance to thermal ablation induced heat stress and local recurrence remain unclear. Here we demonstrate that the HCC cells with a poor prognostic hepatic stem cell subtype (Subtype HS) are more resistant to heat stress than HCC cells with a better prognostic hepatocyte subtype (Subtype HC). Moreover, sublethal heat stress rapidly induces phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dependent-protein kinase B (AKT) survival signaling in HCC cells in vitro and at the tumor ablation margin in vivo. Conversely, inhibition of PI3K/mTOR complex 2 (mTORC2)-dependent AKT phosphorylation or direct inhibition of AKT function both enhance HCC cell killing and decrease HCC cell survival to sublethal heat stress in both poor and better prognostic HCC subtypes while mTOR complex 1 (mTORC1)-inhibition has no impact. Finally, we showed that AKT isoforms 1, 2 and 3 are differentially upregulated in primary human HCCs and that overexpression of AKT correlates with worse tumor biology and pathologic features (AKT3) and prognosis (AKT1). Together these findings define a novel molecular mechanism whereby heat stress induces PI3K/mTORC2-dependent AKT survival signaling in HCC cells and provide a mechanistic rationale for adjuvant AKT inhibition in combination with thermal ablation as a strategy to enhance HCC cell killing and prevent local recurrence, particularly at the ablation margin.

Epithelial-to-mesenchymal plasticity of cancer stem cells: therapeutic targets in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains one of the most common and lethal malignancies worldwide despite the development of various therapeutic strategies. A better understanding of the mechanisms responsible for HCC initiation and progression is essential for the development of more effective therapies. The cancer stem cell (CSC) model has provided new insights into the development and progression of HCC. CSCs are specialized tumor cells that are capable of self-renewal and have long-term repopulation potential. As they are important mediators of tumor proliferation, invasion, metastasis, therapy resistance, and cancer relapse, the selective targeting of this crucial population of cells has the potential to improve HCC patient outcomes and survival. In recent years, the role of epithelial-to-mesenchymal transition (EMT) in the advancement of HCC has gained increasing attention. This multi-step reprograming process resulting in a phenotype switch from an epithelial to a mesenchymal cellular state has been closely associated with the acquisition of stem cell-like attributes in tumors. Moreover, CSC mediates tumor metastasis by maintaining plasticity to transition between epithelial or mesenchymal states. Therefore, understanding the molecular mechanisms of the reprograming switches that determine the progression through EMT and generation of CSC is essential for developing clinically relevant drug targets. This review provides an overview of the proposed roles of CSC in HCC and discusses recent results supporting the emerging role of EMT in facilitating hepatic CSC plasticity. In particular, we discuss how these important new insights may facilitate rational development of combining CSC- and EMT-targeted therapies in the future.

Inducing Differentiation of Premalignant Hepatic Cells as a Novel Therapeutic Strategy in Hepatocarcinoma

Hepatocellular carcinoma (HCC) represents the second leading cause of cancer-related deaths and is reported to be resistant to chemotherapy caused by tumor-initiating cells. These tumor-initiating cells express stem cell markers. An accumulation of tumor-initiating cells can be found in 2% to 50% of all HCC and is correlated with a poor prognosis. Mechanisms that mediate chemoresistance include drug export, increased metabolism, and quiescence. Importantly, the mechanisms that regulate quiescence in tumor-initiating cells have not been analyzed in detail so far. In this research we have developed a single cell tracking method to follow up the fate of tumor-initiating cells during chemotherapy. Thereby, we were able to demonstrate that mCXCL1 exerts cellular state-specific effects regulating the resistance to chemotherapeutics. mCXCL1 is the mouse homolog of the human IL8, a chemokine that correlates with poor prognosis in HCC patients. We found that mCXCL1 blocks differentiation of premalignant cells and activates quiescence in tumor-initiating cells. This process depends on the activation of the mTORC1 kinase. Blocking of the mTORC1 kinase induces differentiation of tumor-initiating cells and allows their subsequent depletion using the chemotherapeutic drug doxorubicin. Our work deciphers the mCXCL1-mTORC1 pathway as crucial in liver cancer stem cell maintenance and highlights it as a novel target in combination with conventional chemotherapy. Cancer Res; 76(18); 5550-61. ©2016 AACR.

Cancer Stem cells and their cellular origins in primary liver and biliary tract cancers

Liver and biliary tract cancers are highly aggressive, are heterogeneous in their phenotypic traits, and result in clinical outcomes that are difficult to manage. Cancers have subpopulations of cells termed "cancer stem cells" (CSCs) that share common intrinsic signaling pathways for self-renewal and differentiation with normal stem cells. These CSCs likely have the potential to evolve over time and to give rise to new genetically and functionally diverse subclones by accumulating genetic mutations. Extrinsic signaling from the tumor microenvironment, including the CSC niche, has been implicated in tumor initiation/progression and heterogeneity through dynamic crosstalk. CSCs have become recognized as pivotal sources of tumor initiation/progression, relapse/metastasis, and chemoresistance.

CONCLUSION

The origins of CSCs are hypothesized to derive from the transformation of normal stem/progenitors and/or from the reprogramming of adult cells that converts them to stem/progenitor traits; however, the precise mechanisms have not yet been fully elucidated. (Hepatology 2016;64:645-651).

Annexin A6 protein is downregulated in human hepatocellular carcinoma

Annexin A6 (AnxA6) is a lipid-binding protein highly expressed in the liver, regulating cholesterol homeostasis and signaling pathways with a role in liver physiology. Here, we analyzed whether hepatic AnxA6 levels are affected by pathological conditions that are associated with liver dysfunction and liver injury. AnxA6 levels in the fatty liver of mice fed a high-fat diet, in ob/ob and db/db animals and in human fatty liver are comparable to controls. Similarly, AnxA6 levels appear unaffected in murine nonalcoholic steatohepatitis and human liver fibrosis. Accordingly, adiponectin, lysophosphatidylcholine, palmitate, and TGFbeta, all of which have a role in liver injury, do not affect AnxA6 expression in human hepatocytes. Likewise, adiponectin and IL8 do not alter AnxA6 levels in primary human hepatic stellate cells. However, in hepatic tumors of 18 patients, AnxA6 protein levels are substantially reduced compared to nontumorous tissues. AnxA6 mRNA is even increased in the tumors suggesting that posttranscriptional mechanisms are involved herein. Lipidomic analysis shows trends toward elevated cholesteryl ester and sphingomyelin in the tumor samples, yet the ratio of tumor to nontumorous AnxA6 does not correlate with these lipids. The current study shows that AnxA6 is specifically reduced in human hepatocellular carcinoma suggesting a role of this protein in hepatocarcinogenesis.

Prognostic value of CD44 expression in patients with hepatocellular carcinoma: meta-analysis

Background

CD44 has been reported to be involved with tumor growth and metastasis and has also been implicated as a CSC marker in hepatocellular carcinoma (HCC). However, the prognostic value of CD44 still remains controversial; hence, we investigated the correlation between CD44 and the clinicopathological features of HCC by meta-analysis.

Methods

Identification and review of publications assessing clinical or prognostic significance of CD44 expression in HCC until November 1, 2015. A meta-analysis was performed to clarify the association between CD44 expression and clinical outcomes.

Results

A total of 14 publications met the criteria and comprised 2235 cases. Analysis of these data showed that CD44 expression was not significantly associated with the tumor differentiation (OR 1.48, 95 % confidence interval [CI] 0.85–2.60, P = 0.17), AFP level of HCC patients (OR 0.83, 95 % CI 0.52–1.33, P = 0.45), or disease-free survival (relative risk [RR] 1.15, 95 % CI, 0.85–1.54; P = 0.36). However, in the identified studies, CD44 expression was highly correlated with tumor TNM classification (OR 2.38, 95 % CI 1.23–4.60; P = 0.01) and decreased overall survival (RR 1.49, 95 % CI, 1.26–1.76; P < 0.00001).

Conclusions

This meta-analysis shows CD44 expression in HCC is connected with decreased overall and thus marks a worse prognosis.

Jagged1 DNA Copy Number Variation Is Associated with Poor Outcome in Liver Cancer

Notch signaling abnormalities are reported to be involved in the acceleration of malignancy in solid tumors and stem cell formation or regeneration in various organs. We analyzed specific genes for DNA copy number variations in liver cancer cells and investigated whether these factors relate to clinical outcome. Chromosome 20p, which includes the ligand for Notch pathways, Jagged1, was found to be amplified in several types of hepatoma cells, and its mRNA was up-regulated according to α-fetoprotein gene expression levels. Notch inhibition using Jagged1 shRNA and γ-secretase inhibitors produced significant suppression of cell growth in α-fetoprotein-producing cells with suppression of downstream genes. Using in vivo hepatoma models, the administration of γ-secretase inhibitors resulted in reduced tumor sizes and effective Notch inhibition with widespread apoptosis and necrosis of viable tumor cells. The γ-secretase inhibitors suppressed cell growth of the epithelial cell adhesion molecule-positive fraction in hepatoma cells, indicating that Notch inhibitors could suppress the stem cell features of liver cancer cells. Even in clinical liver cancer samples, the expression of α-fetoprotein and Jagged1 showed significant correlation, and amplification of the copy number of Jagged1 was associated with Jagged1 mRNA expression and poor survival after liver cancer surgical resection. In conclusion, amplification of Jagged1 contributed to mRNA expression that activates the Jagged1-Notch signaling pathway in liver cancer and led to poor outcome.

Oncogenic role of the Notch pathway in primary liver cancer

Primary liver cancer, which includes hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (ICC) and fibrolamellar HCC, is one of the most common malignancies and the third leading cause of cancer-associated mortality, worldwide. Despite the development of novel therapies, the prognosis of liver cancer patients remains extremely poor. Thus, investigation of the genetic background and molecular mechanisms underlying the development and progression of this disease has gained significant attention. The Notch signaling pathway is a crucial determinant of cell fate during development and disease in several organs. In the liver, Notch signaling is involved in biliary tree development and tubulogenesis, and is also significant in the development of HCC and ICC. These findings suggest that the modulation of Notch pathway activity may have therapeutic relevance. The present review summarizes Notch signaling during HCC and ICC development and discusses the findings of recent studies regarding Notch expression, which reveal novel insights into its function in liver cancer progression.

Prognostic value of DNA repair based stratification of hepatocellular carcinoma

Aberrant activation of DNA repair is frequently associated with tumor progression and response to therapy in hepatocellular carcinoma (HCC). Bioinformatics analyses of HCC data in the Cancer Genome Atlas (TCGA) were performed to define DNA repair based molecular classification that could predict the prognosis of patients with HCC. Furthermore, we tested its predictive performance in 120 independent cases. Four molecular subgroups were identified on the basis of coordinate DNA repair cluster (CDRC) comprising 15 genes in TCGA dataset. Increasing expression of CDRC genes were significantly associated with TP53 mutation. High CDRC was significantly correlated with advanced tumor grades, advanced pathological stage and increased vascular invasion rate. Multivariate Cox regression analysis indicated that the molecular subgrouping was an independent prognostic parameter for both overall survival (p = 0.004, hazard ratio (HR): 2.989) and tumor-free survival (p = 0.049, HR: 3.366) in TCGA dataset. Similar results were also obtained by analyzing the independent cohort. These data suggest that distinct dysregulation of DNA repair constituents based molecular classes in HCC would be useful for predicting prognosis and designing clinical trials for targeted therapy.

CHD1L promotes lineage reversion of hepatocellular carcinoma through opening chromatin for key developmental transcription factors

High-grade tumors with poor differentiation usually show phenotypic resemblance to their developmental ancestral cells. Cancer cells that gain lineage precursor cell properties usually hijack developmental signaling pathways to promote tumor malignant progression. However, the molecular mechanisms underlying this process remain unclear. In this study, the chromatin remodeler chromodomain-helicase-DNA-binding-protein 1-like (CHD1L) was found closely associated with liver development and hepatocellular carcinoma (HCC) tumor differentiation. Expression of CHD1L decreased during hepatocyte maturation and increased progressively from well-differentiated HCCs to poorly differentiated HCCs. Chromatin immunoprecipitation followed by high-throughput deep sequencing found that CHD1L could bind to the genomic sequences of genes related to development. Bioinformatics-aided network analysis indicated that CHD1L-binding targets might form networks associated with developmental transcription factor activation and histone modification. Overexpression of CHD1L conferred ancestral precursor-like properties of HCC cells both in vitro and in vivo. Inhibition of CHD1L reversed tumor differentiation and sensitized HCC cells to sorafenib treatment. Mechanism studies revealed that overexpression of CHD1L could maintain an active "open chromatin" configuration at promoter regions of estrogen-related receptor-beta and transcription factor 4, both of which are important regulators of HCC self-renewal and differentiation. In addition, we found a significant correlation of CHD1L with developmental transcriptional factors and lineage differentiation markers in clinical HCC patients.

CONCLUSION

Genomic amplification of chromatin remodeler CHD1L might drive dedifferentiation of HCC toward an ancestral lineage through opening chromatin for key developmental transcriptional factors; further inhibition of CHD1L might "downgrade" poorly differentiated HCCs and provide novel therapeutic strategies.

Neoangiogenesis-related genes are hallmarks of fast-growing hepatocellular carcinomas and worst survival. Results from a prospective study

OBJECTIVE

The biological heterogeneity of hepatocellular carcinoma (HCC) makes prognosis difficult. We translate the results of a genome-wide high-throughput analysis into a tool that accurately predicts at presentation tumour growth and survival of patients with HCC.

DESIGN

Ultrasound surveillance identified HCC in 78 (training set) and 54 (validation set) consecutive patients with cirrhosis. Patients underwent two CT scans 6 weeks apart (no treatment in-between) to determine tumour volumes (V0 and V1) and calculate HCC doubling time. Baseline-paired HCC and surrounding tissue biopsies for microarray study (Agilent Whole Human Genome Oligo Microarrays) were also obtained. Predictors of survival were assessed by multivariate Cox model.

RESULTS

Calculated tumour doubling times ranged from 30 to 621 days (mean, 107±91 days; median, 83 days) and were divided into quartiles: ≤53 days (n=19), 54-82 days (n=20), 83-110 days (n=20) and ≥111 days (n=19). Median survival according to doubling time was significantly lower for the first quartile versus the others (11 vs 41 months, 42, and 47 months, respectively) (p<0.0001). A five-gene transcriptomic hepatic signature including angiopoietin-2 (ANGPT2), delta-like ligand 4 (DLL4), neuropilin (NRP)/tolloid (TLL)-like 2 (NETO2), endothelial cell-specific molecule-1 (ESM1), and nuclear receptor subfamily 4, group A, member 1 (NR4A1) was found to accurately identify rapidly growing HCCs of the first quartile (ROC AUC: 0.961; 95% CI 0.919 to 1.000; p<0.0001) and to be an independent factor for mortality (HR: 3.987; 95% CI 1.941 to 8.193, p<0.0001).

CONCLUSIONS

The hepatic five-gene signature was able to predict HCC growth in individual patient and the consequent risk of death. This implies a role of this molecular tool in the future therapeutic management of patients with HCC.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT01657695.

Hepatocellular carcinoma

Liver cancer is the second leading cause of cancer-related deaths globally and has an incidence of approximately 850,000 new cases per year. Hepatocellular carcinoma (HCC) represents approximately 90% of all cases of primary liver cancer. The main risk factors for developing HCC are well known and include hepatitis B and C virus infection, alcohol intake and ingestion of the fungal metabolite aflatoxin B1. Additional risk factors such as non-alcoholic steatohepatitis are also emerging. Advances in the understanding of the molecular pathogenesis of HCC have led to identification of critical driver mutations; however, the most prevalent of these are not yet druggable targets. The molecular classification of HCC is not established, and the Barcelona Clinic Liver Cancer staging classification is the main clinical algorithm for the stratification of patients according to prognosis and treatment allocation. Surveillance programmes enable the detection of early-stage tumours that are amenable to curative therapies - resection, liver transplantation or local ablation. At more developed stages, only chemoembolization (for intermediate HCC) and sorafenib (for advanced HCC) have shown survival benefits. There are major unmet needs in HCC management that might be addressed through the discovery of new therapies and their combinations for use in the adjuvant setting and for intermediate- and advanced-stage disease. Moreover, biomarkers for therapy stratification, patient-tailored strategies targeting driver mutations and/or activating signalling cascades, and validated measurements of quality of life are needed. Recent failures in the testing of systemic drugs for intermediate and advanced stages have indicated a need to refine trial designs and to define novel approaches.

Spontaneous Hepatocellular Carcinoma after the Combined Deletion of Akt Isoforms

Akt is frequently hyperactivated in human cancers and is targeted for cancer therapy. However, the physiological consequences of systemic Akt isoform inhibition were not fully explored. We showed that while combined Akt1 and Akt3 deletion in adult mice is tolerated, combined Akt1 and Akt2 deletion induced rapid mortality. Akt2(-/-) mice survived hepatic Akt1 deletion but all developed spontaneous hepatocellular carcinoma (HCC), which is associated with FoxO-dependent liver injury and inflammation. The gene expression signature of HCC-bearing livers is similar to aggressive human HCC. Consistently, neither Akt1(-/-) nor Akt2(-/-) mice are resistant to diethylnitrosamine-induced hepatocarcinogenesis, and Akt2(-/-) mice display a high incidence of lung metastasis. Thus, in contrast to other cancers, hepatic Akt inhibition induces liver injury that could promote HCC.

Mechanisms of HBV-induced hepatocellular carcinoma

Hepatitis B virus (HBV) contributes to hepatocellular carcinoma (HCC) development through direct and indirect mechanisms. HBV DNA integration into the host genome occurs at early steps of clonal tumor expansion and induces both genomic instability and direct insertional mutagenesis of diverse cancer-related genes. Prolonged expression of the viral regulatory protein HBx and/or altered versions of the preS/S envelope proteins dysregulates cell transcription and proliferation control and sensitizes liver cells to carcinogenic factors. Accumulation of preS1 large envelope proteins and/or preS2/S mutant proteins activates the unfold proteins response, that can contribute to hepatocyte transformation. Epigenetic changes targeting the expression of tumor suppressor genes occur early in the development of HCC. A major role is played by the HBV protein, HBx, which is recruited on cellular chromatin and modulates chromatin dynamics at specific gene loci. Compared with tumors associated with other risk factors, HBV-related tumors have a higher rate of chromosomal alterations, p53 inactivation by mutations and overexpression of fetal liver/hepatic progenitor cells genes. The WNT/β-catenin pathway is also often activated but HBV-related tumors display a low rate of activating β-catenin mutations. HBV-related HCCs may arise on non-cirrhotic livers, further supporting the notion that HBV plays a direct role in liver transformation by triggering both common and etiology specific oncogenic pathways in addition to stimulating the host immune response and driving liver chronic necro-inflammation.

The metabolic gene HAO2 is downregulated in hepatocellular carcinoma and predicts metastasis and poor survival

BACKGROUND & AIMS

l-2-Hydroxy acid oxidases are flavin mononucleotide-dependent peroxisomal enzymes, responsible for the oxidation of l-2-hydroxy acids to ketoacids, resulting in the formation of hydrogen peroxide. We investigated the role of HAO2, a member of this family, in rat, mouse and human hepatocarcinogenesis.

METHODS

We evaluated Hao2 expression by qRT-PCR in the following rodent models of hepatocarcinogenesis: the Resistant-Hepatocyte, the CMD and the chronic DENA rat models, and the TCPOBOP/DENA and TCPOBOP only mouse models. Microarray and qRT-PCR analyses were performed on two cohorts of human hepatocellular carcinoma (HCC) patients. Rat HCC cells were transduced by a Hao2 encoding lentiviral vector and grafted in mice.

RESULTS

Downregulation of Hao2 was observed in all investigated rodent models of hepatocarcinogenesis. Interestingly, Hao2 mRNA levels were also profoundly downregulated in early preneoplastic lesions. Moreover, HAO2 mRNA levels were strongly downregulated in two distinct series of human HCCs, when compared to both normal and cirrhotic peri-tumoral liver. HAO2 levels were inversely correlated with grading, overall survival and metastatic ability. Finally, exogenous expression of Hao2 in rat cells impaired their tumorigenic ability.

CONCLUSION

Our work identifies for the first time the oncosuppressive role of the metabolic gene Hao2. Indeed, its expression is severely decreased in HCC of different species and etiology, and its reintroduction in HCC cells profoundly impairs tumorigenesis. We also demonstrate that dysregulation of HAO2 is a very early event in the development of HCC and it may represent a useful diagnostic and prognostic marker for human HCC.

Genetic polymorphisms in the Wnt/β-catenin pathway genes as predictors of tumor development and survival in patients with hepatitis B virus-associated hepatocellular carcinoma

OBJECTIVES

Wnt/β-catenin signaling has a pivotal role in the pathogenesis of hepatocellular carcinoma (HCC). The present study aimed to determine whether genetic variation in the Wnt/β-catenin signaling pathway is associated with the development and/or progression of HCC and the survival of patients with hepatitis B virus (HBV)-associated HCC.

DESIGN AND METHODS

We assessed seven single nucleotide polymorphisms (SNPs) of the AXIN1, AXIN2, CTNNB1, and WNT2 genes in 245 patients with HBV-associated HCC and 483 chronic HBV carriers without HCC. We analyzed the association of each SNP with HCC development or progression and overall survival.

RESULTS

The CTNNB1 rs3864004 A allele was associated with a decreased risk of HCC development (P=0.049). Haplotype analysis revealed a significantly higher frequency of CTNNB1 G-A/G-A haplotype at rs3864004 and rs4135385 positions in patients with HCC than in chronic HBV carriers without HCC (P=0.042). The AXIN1 rs1805105 T>C SNP was associated with small tumor size and early tumor stage and the WNT2 rs39315 G allele was associated with advanced tumor stage in HCC. In Kaplan-Meier analysis, carriers of the AXIN1 rs214252 C allele showed longer survival than those with the TT genotype (P=0.020). In multivariate Cox regression analysis, absence of CTNNB1 haplotype A-A at rs3864004 and rs4135385 positions and advanced tumor stage were independent poor predictors of patient survival in patients with HCC.

CONCLUSION

These findings suggest that the genetic polymorphisms in CTNNB1 gene might affect tumor development and survival in patients with HBV-associated HCC.

Current and future challenges in the surgical treatment of hepatocellular carcinoma: a review

Challenges in the treatment of hepatocellular carcinoma Hepatocellular carcinoma (HCC) represents one of the most frequent types of cancer worldwide. Surgery, although only a part of the armamentarium against HCC, represents the cornerstone in the management of this aggressive disease. This article will review the current and future challenges in the surgical management of HCC, with a special emphasis on the following areas: (1) the evolution of staging of the disease and the importance of the biological nature and behavior of HCC, (2) the effort to increase resectability, (3) technical innovations and the role of image-guided surgery, and, finally, (4) the role of liver transplantation in the continuum of care for these patients. Although by no means an exhaustive list, the issues mentioned above represent some of the most promising prospects for significant progress in the management of HCC.

Multiple cellular origins and molecular evolution of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy associated with unfavorable prognosis and for which no effective treatments are available. Its molecular pathogenesis is poorly understood. Genome-wide sequencing and high-throughput technologies have provided critical insights into the molecular basis of ICC while sparking a heated debate on the cellular origin. Cancer exhibits variabilities in origin, progression and cell biology. Recent evidence suggests that ICC has multiple cellular origins, including differentiated hepatocytes; intrahepatic biliary epithelial cells (IBECs)/cholangiocytes; pluripotent stem cells, such as hepatic stem/progenitor cells (HPCs) and biliary tree stem/progenitor cells (BTSCs); and peribiliary gland (PBG). However, both somatic mutagenesis and epigenomic features are highly cell type-specific. Multiple cellular origins may have profoundly different genomic landscapes and key signaling pathways, driving phenotypic variation and thereby posing significant challenges to personalized medicine in terms of achieving the optimal drug response and patient outcome. Considering this information, we have summarized the latest experimental evidence and relevant literature to provide an up-to-date view of the cellular origin of ICC, which will contribute to establishment of a hierarchical model of carcinogenesis and allow for improvement of the anatomical-based classification of ICC. These new insights have important implications for both the diagnosis and treatment of ICC patients.

Clinical implications of basic research in hepatocellular carcinoma

A 58-year old Caucasian female has compensated hepatitis C related cirrhosis. Her surveillance ultrasound showed hypodense liver nodules and subsequent triple phase CT scan showed five tumor nodules with diameters ranging from 3-5cms involving both hepatic lobes. The nodules showed characteristic radiologic findings on the CT scan and she was diagnosed with hepatocellular carcinoma (HCC) based on non-invasive criteria. There was also associated right portal vein tumor thrombosis. Her functional capacity at diagnosis was slightly limited, but she was capable of performing all activities of daily living and self-care. Her laboratory tests at diagnosis were as follows: sodium 129mmol/L, potassium 3.6mmol/L, blood urea nitrogen 22mg/dL, creatinine 1.0mg/dL, albumin 2.9g/dl, bilirubin 1.8mg/dl, alanine aminotransferase 87U/L, aspartate aminotransferase 68U/L, alkaline phosphatase 139U/L, white blood cell 3.5x10(9)/L, hemoglobin 10.4, platelet count 73x10(9)/L, international normalized ratio 1.9 and alpha-fetoprotein 5200ng/ml. An upper endoscopy was negative for esophageal or gastric varices. Based on the tumor burden, presence of macrovascular invasion, ECOG performance status of 1 and Child-Pugh class A she was classified to have BCLC stage C HCC. She was started on sorafenib therapy at 400mg oral twice daily but unfortunately this had to be discontinued since she experienced severe diarrhea and skin rash. She now returns for follow-up and requests information on the available therapeutic options. This particular case scenario is not uncommon and does raise several clinically relevant questions: This review provides a comprehensive overview of the current state of HCC management and also examines the clinical implications of recent basic research in HCC.

Cellular prognostic markers in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the five big killers worldwide and is frequently associated with chronic hepatitis B and C virus (HBV and HCV) infections. Tumor microenvironment consists of a complex network of cells and factors that plays a key role in the tumor progression and prognosis. This is true also for HCC. Several studies have shown strikingly strong correlation between HCC clinical prognosis and intratumoral infiltration of cells affecting tumor growth, invasion, angiogenesis and metastasis. None of such cells is yet validated for routine diagnostic and prognostic assessment. The present review aims at providing a state-of-the-art of such studies.

Metformin prevents hepatocellular carcinoma development by suppressing hepatic progenitor cell activation in a rat model of cirrhosis

BACKGROUND

Hepatocellular carcinoma (HCC)-associated mortality is increasing at an alarming rate, and there is a readily identifiable cohort of at-risk patients with cirrhosis, viral hepatitis, nonalcoholic fatty liver disease, and diabetes. These patients are candidates for chemoprevention. Metformin is an attractive agent for chemoprevention because it is inexpensive, has a favorable safety profile, and is well tolerated over long time periods.

METHODS

The authors studied the efficacy of metformin as a prevention agent in a clinically relevant rat model of HCC, in which tumors develop in the setting of chronic inflammation and cirrhosis. Repeated injections of diethylnitrosamine were used to induce sequential cirrhosis and HCC, and metformin was administered at the first signs of either fibrosis or cirrhosis.

RESULTS

Prolonged metformin exposure was safe and was associated with decreases in fibrotic and inflammatory markers, especially when administered early at the first signs of fibrosis. In addition, early metformin treatment led to a 44% decrease in HCC incidence, whereas tumor burden was unchanged when metformin was administered at the first signs of cirrhosis. It is noteworthy that activation of the hepatic progenitor/stem cell compartment was first observed at the onset of cirrhosis; therefore, only early metformin treatment suppressed receptor for advanced glycation end products and inhibited the activation of hepatic progenitor cells.

CONCLUSIONS

The current results are the first to demonstrate an effect on progenitor/stem cells in the setting of chemoprevention and provide further rationale to explore metformin as an early intervention in clinical trials of patients with chronic liver disease at high risk for HCC.

Persistent effect of mTOR inhibition on preneoplastic foci progression and gene expression in a rat model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a heterogeneous disease in which tumor subtypes can be identified based on the presence of adult liver progenitor cells. Having previously identified the mTOR pathway as critical to progenitor cell proliferation in a model of liver injury, we investigated the temporal activation of mTOR signaling in a rat model of hepatic carcinogenesis. The model employed chemical carcinogens and partial hepatectomy to induce progenitor marker-positive HCC. Immunohistochemical staining for phosphorylated ribosomal protein S6 indicated robust mTOR complex 1 (mTORC1) activity in early preneoplastic lesions that peaked during the first week and waned over the subsequent 10 days. Continuous administration of rapamycin by subcutaneous pellet for 70 days markedly reduced the development of focal lesions, but resulted in activation of the PI3K signaling pathway. To test the hypothesis that early mTORC1 activation was critical to the development and progression of preneoplastic foci, we limited rapamycin administration to the 3-week period at the start of the protocol. Focal lesion burden was reduced to a degree indistinguishable from that seen with continuous administration. Short-term rapamycin did not result in the activation of PI3K or mTORC2 pathways. Microarray analysis revealed a persistent effect of short-term mTORC1 inhibition on gene expression that resulted in a genetic signature reminiscent of normal liver. We conclude that mTORC1 activation during the early stages of hepatic carcinogenesis may be critical due to the development of preneoplastic focal lesions in progenitor marker-positive HCC. mTORC1 inhibition may represent an effective chemopreventive strategy for this form of liver cancer.

A Gene Expression Signature Associated with Overall Survival in Patients with Hepatocellular Carcinoma Suggests a New Treatment Strategy

Despite improvements in the management of liver cancer, the survival rate for patients with hepatocellular carcinoma (HCC) remains dismal. The survival benefit of systemic chemotherapy for the treatment of liver cancer is only marginal. Although the reasons for treatment failure are multifactorial, intrinsic resistance to chemotherapy plays a primary role. Here, we analyzed the expression of 377 multidrug resistance (MDR)-associated genes in two independent cohorts of patients with advanced HCC, with the aim of finding ways to improve survival in this poor-prognosis cancer. Taqman-based quantitative polymerase chain reaction revealed a 45-gene signature that predicts overall survival (OS) in patients with HCC. Using the Connectivity Map Tool, we were able to identify drugs that converted the gene expression profiles of HCC cell lines from ones matching patients with poor OS to profiles associated with good OS. We found three compounds that convert the gene expression profiles of three HCC cell lines to gene expression profiles associated with good OS. These compounds increase histone acetylation, which correlates with the synergistic sensitization of those MDR tumor cells to conventional chemotherapeutic agents, including cisplatin, sorafenib, and 5-fluorouracil. Our results indicate that it is possible to modulate gene expression profiles in HCC cell lines to those associated with better outcome. This approach also increases sensitization of HCC cells toward conventional chemotherapeutic agents. This work suggests new treatment strategies for a disease for which few therapeutic options exist.

Diversity of Gene Expression in Hepatocellular Carcinoma Cells

Understanding tumor diversity has been a long-lasting and challenging question for researchers in the field of cancer heterogeneity or tumor evolution. Studies have reported that compared to normal cells, there is a higher genetic diversity in tumor cells, while higher genetic diversity is associated with higher progression risks of tumor. We thus hypothesized that tumor diversity also holds true at the gene expression level. To test this hypothesis, we used t-test to compare the means of Simpson’s diversity index for gene expression (SDIG) between tumor and non-tumor samples. We found that the mean SDIG in tumor tissues is significantly higher than that in the non-tumor or normal tissues (P < 0.05) for most datasets. We also combined microarrays and next-generation sequencing data for validation. This cross-platform and cross-experimental validation greatly increased the reliability of our results.

Reversible Human TGF-β Signal Shifting between Tumor Suppression and Fibro-Carcinogenesis: Implications of Smad Phospho-Isoforms for Hepatic Epithelial-Mesenchymal Transitions

Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are observed during both physiological liver wound healing and the pathological fibrotic/carcinogenic (fibro-carcinogenetic) process. TGF-β and pro-inflammatory cytokine are considered to be the major factors accelerating liver fibrosis and promoting liver carcinogenesis. Smads, consisting of intermediate linker regions connecting Mad homology domains, act as the intracellular mediators of the TGF-β signal transduction pathway. As the TGF-β receptors, c-Jun N-terminal kinase and cyclin-dependent kinase, differentially phosphorylate Smad2/3, we have generated numerous antibodies against linker (L) and C-terminal (C) phosphorylation sites in Smad2/3 and identified four types of phosphorylated forms: cytostatic COOH-terminally-phosphorylated Smad3 (pSmad3C), mitogenic pSmad3L (Ser-213) signaling, fibrogenic pSmad2L (Ser-245/250/255)/C signaling and migratory pSmad2/3L (Thr-220/179)/C signaling. After acute liver injury, TGF-β upregulates pSmad3C signaling and terminates pSmad3L (Ser-213)-mediated hepatocyte proliferation. TGF-β and pro-inflammatory cytokines cooperatively enhance collagen synthesis by upregulating pSmad2L (Thr-220)/C and pSmad3L (Thr-179)/C pathways in activated hepatic stellate cells. During chronic liver injuries, hepatocytes persistently affected by TGF-β and pro-inflammatory cytokines eventually become pre-neoplastic hepatocytes. Both myofibroblasts and pre-neoplastic hepatocyte exhibit the same carcinogenic (mitogenic) pSmad3L (Ser-213) and fibrogenic pSmad2L (Ser-245/250/255)/C signaling, with acquisition of fibro-carcinogenic properties and increasing risk of hepatocellular carcinoma (HCC). Firstly, we review phospho-Smad-isoform signalings in epithelial and mesenchymal cells in physiological and pathological conditions and then consider Smad linker phosphorylation as a potential target for pathological EMT during human fibro-carcinogenesis, because human Smad phospho-isoform signals can reverse from fibro-carcinogenesis to tumor-suppression in a process of MET after therapy.

Integrin αvβ6 critically regulates hepatic progenitor cell function and promotes ductular reaction, fibrosis, and tumorigenesis

Integrin αvβ6 is rapidly up-regulated on cells of epithelial lineage during tissue injury, where one of its primary functions is activation of latent transforming growth factor beta 1 (TGFβ1). In human liver cirrhosis, αvβ6 is overexpressed by cells comprising the ductular reaction, and its inhibition suppresses experimental biliary fibrosis in rodents. Here, we show that αvβ6 is expressed on the actively proliferating subset of hepatic progenitor cells and is required for their progenitor function in vivo and in vitro through integrin αvβ6-dependent TGFβ1 activation. Freshly isolated αvβ6(+) liver cells demonstrate clonogenic potential and differentiate into cholangiocytes and functional hepatocytes in vitro, whereas colony formation by epithelial cell adhesion molecule-positive progenitor cells is blocked by αvβ6-neutralizing antibody and in integrin beta 6-deficient cells. Inhibition of progenitors by anti-αvβ6 antibody is recapitulated by TGFβ1 neutralization and rescued by addition of bioactive TGFβ1. Genetic disruption or selective targeting of αvβ6 with 3G9 antibody potently inhibits progenitor cell responses in mouse models of chronic biliary injury and protects from liver fibrosis and tumorigenesis, two conditions clinically associated with exacerbated ductular reaction.

CONCLUSION

These results suggest that αvβ6 is a promising target for chronic fibrotic liver diseases and associated cancers.

Advances in Liver Regeneration: Revisiting Hepatic Stem/Progenitor Cells and Their Origin

The liver has evolved to become a highly plastic organ with extraordinary regenerative capabilities. What drives liver regeneration is still being debated. Adult liver stem/progenitor cells have been characterized and used to produce functional hepatocytes and biliary cells in vitro. However, in vivo, numerous studies have questioned whether hepatic progenitor cells have a significant role in liver regeneration. Mature hepatocytes have recently been shown to be more plastic than previously believed and give rise to new hepatocytes after acute and chronic injury. In this review, we discuss current knowledge in the field of liver regeneration and the importance of the serotonin pathway as a clinical target for patients with liver dysfunction.