Oncofetal gene SALL4 in aggressive hepatocellular carcinoma

Human primary liver cancer-derived organoid cultures for disease modeling and drug screening

Human liver cancer research currently lacks in vitro models that can faithfully recapitulate the pathophysiology of the original tumor. We recently described a novel, near-physiological organoid culture system, wherein primary human healthy liver cells form long-term expanding organoids that retain liver tissue function and genetic stability. Here we extend this culture system to the propagation of primary liver cancer (PLC) organoids from three of the most common PLC subtypes: hepatocellular carcinoma (HCC), cholangiocarcinoma (CC) and combined HCC/CC (CHC) tumors. PLC-derived organoid cultures preserve the histological architecture, gene expression and genomic landscape of the original tumor, allowing for discrimination between different tumor tissues and subtypes, even after long-term expansion in culture in the same medium conditions. Xenograft studies demonstrate that the tumorogenic potential, histological features and metastatic properties of PLC-derived organoids are preserved in vivo. PLC-derived organoids are amenable for biomarker identification and drug-screening testing and led to the identification of the ERK inhibitor SCH772984 as a potential therapeutic agent for primary liver cancer. We thus demonstrate the wide-ranging biomedical utilities of PLC-derived organoid models in furthering the understanding of liver cancer biology and in developing personalized-medicine approaches for the disease.

High-throughput flow cytometry screening of human hepatocellular carcinoma reveals CD146 to be a novel marker of tumor-initiating cells

Hepatocellular carcinoma (HCC) remains a common and lethal cancer. Cancer stem cells, or tumor-initiating cells (TICs), are thought to contribute to the pathogenesis of HCC, but remain to be fully characterized. Unbiased screens of primary human HCC cells for the identification of novel HCC TIC markers have not been reported. We conducted high-throughput flow cytometry (HT-FC) profiling to characterize the expression of 375 CD antigens on tumor cells from 10 different human HCC samples. We selected 91 of these for further analysis based on HT-FC data that showed consistent expression in discrete, rare, sortable populations of HCC cells. Nine of these CD antigens demonstrated significantly increased expression in the EpCAM⁺ stem/progenitor fraction of a human HCC cell line and were further evaluated in primary human HCC tissues from 30 different patients. Of the nine tested, only CD146 demonstrated significantly increased expression in HCC tumor tissue as compared with matched adjacent non-tumor liver tissue. CD146⁺CD31⁻CD45⁻ cells purified from HCC tumors and cell lines demonstrated a unique phenotype distinct from mesenchymal stem cells. As compared with other tumor cell fractions, CD146⁺CD31⁻CD45⁻ cells showed significantly increased colony-forming capacity in vitro, consistent with TICs. This study demonstrates that HT-FC screening can be successfully applied to primary human HCC and reveals CD146 to be a novel TIC marker in this disease.

•

Unbiased screens of human HCC cells for novel TIC markers have not been reported.

•

A high-throughput flow cytometry screen of human HCC cells was successfully performed .

•

Candidate TIC markers were further evaluated by RT-PCR and functional assays.

•

Of candidates tested, only CD146 expression was significantly increased in HCC tissues.

•

CD146⁺ cells had increased colony-forming capacity, consistent with a TIC phenotype.

Oncofetal gene SALL4 and prognosis in cancer: A systematic review with meta-analysis

The Spalt-Like Transcription Factor 4 (SALL4) oncogene plays a central function in embryo-fetal development and is absent in differentiated tissues. Evidence suggests that it can be reactivated in several cancers worsening the prognosis. We aimed at investigating the risk associated with SALL4 reactivation for all-cause mortality and recurrence in cancer using the current literature. A PubMed and SCOPUS search until 1st September 2016 was performed, focusing on perspective studies reporting prognostic parameters in cancer data. In addition, 17 datasets of different cancer types from The Cancer Genome Atlas were considered. A total of 9,947 participants across 40 cohorts, followed-up for about 5 years on average, were analyzed comparing patients showing SALL4 presence (SALL4+, n = 1,811) or absence (SALL4-, n = 8,136). All data were summarised using risk ratios (RRs) for the number of deaths/recurrences and hazard ratios (HRs) for the time-dependent risk related to SALL4+, adjusted for potential confounders. SALL4+ significantly increased overall mortality (RR = 1.34, 95% confidence intervals (CI)=1.21-1.48, p<0.0001, I2=66%; HR=1.4; 95%CI: 1.19-1.65; p<0.0001; I2=63%) and recurrence of disease (RR = 1.25, 95% CI = 1.1-1.42, p=0.0006, I2=62%); HR=1.52; 95% CI: 1.22-1.89, p=0.0002; I2=69%) compared to SALL4-. Moreover, SALL4 remained significantly associated with poor prognosis even using HRs adjusted for potential confounders (overall mortality: HR=1.4; 95%CI: 1.19-1.65; p<0.0001; I2=63%; recurrence of disease: HR=1.52; 95% CI: 1.22-1.89, p=0.0002; I2=69%). These results suggest that SALL4 expression increases both mortality and recurrence of cancer, confirming this gene as an important prognostic marker and a potential target for personalized medicine.

WASH overexpression enhances cancer stem cell properties and correlates with poor prognosis of esophageal carcinoma

There is increasing evidence that cytoskeleton remodeling is involved in cancer progression. Wiskott-Aldrich syndrome protein (WASP) family represents a key regulator of actin cytoskeleton remodeling. However, the underlying mechanism of the WASP family in cancer progression remains elusive. Here, we studied the role of WASP and SCAR Homolog (WASH), a recently identified WASP family member, in human esophageal squamous cell carcinoma (ESCC). Using three human ESCC cell lines, we found that WASH expression was significantly elevated in cancer stem-like cells enriched by sphere formation assay. WASH knockdown decreased the sphere-forming capacity of esophageal cancer cells whereas WASH over-expression exhibited the opposite effect. Mechanistically, we identified interleukin-8 (IL-8) as a key downstream target of WASH. IL-8 knockdown completely attenuated tumor sphere formation induced by WASH overexpression. WASH knockdown also delayed the growth of human ESCC xenografts in BALB/c nude mice. Importantly, high WASH levels were associated with poor clinical prognosis in a total of 145 human ESCC tissues. Collectively, our results suggest an essential role of the WASH/IL-8 pathway in human ESCC by maintaining the stemness of cancer cells. Hence, targeting this pathway might represent a promising strategy to control human esophageal carcinoma.

Liver Cancer: Molecular Characterization, Clonal Evolution and Cancer Stem Cells

Liver cancer is the second most common cause of cancer-related death. The major forms of primary liver cancer are hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). Both these tumors develop against a background of cirrhotic liver, non-alcoholic fatty liver disease, chronic liver damage and fibrosis. HCC is a heterogeneous disease which usually develops within liver cirrhosis related to various etiologies: hepatitis B virus (HBV) infection (frequent in Asia and Africa), hepatitis C virus (HCV), chronic alcohol abuse, or metabolic syndrome (frequent in Western countries). In cirrhosis, hepatocarcinogenesis is a multi-step process where pre-cancerous dysplastic macronodules transform progressively into HCC. The patterns of genomic alterations observed in these tumors were recently identified and were instrumental for the identification of potential targeted therapies that could improve patient care. Liver cancer stem cells are a small subset of undifferentiated liver tumor cells, responsible for cancer initiation, metastasis, relapse and chemoresistance, enriched and isolated according to immunophenotypic and functional properties: cell surface proteins (CD133, CD90, CD44, EpCAM, OV-6, CD13, CD24, DLK1, α2δ1, ICAM-1 and CD47); the functional markers corresponding to side population, high aldehyde dehydrogenase (ALDH) activity and autofluorescence. The identification and definition of liver cancer stem cells requires both immunophenotypic and functional properties.

Hepatocellular malignant neoplasm, NOS: a clinicopathological study of 11 cases from a single institution

AIMS

The primary aim of this study is to characterize hepatocellular malignant neoplasm, NOS (HEMNOS), a new provisional entity describing a subset of paediatric hepatocellular tumours, which have histological features of neither typical hepatoblastoma (HB) nor hepatocellular carcinoma (HCC).

METHODS AND RESULTS

The clinicopathological features of 11 patients with HEMNOS were analysed retrospectively. The median age and serum alpha-fetoprotein level at diagnosis was 7 years and 182 000 ng/ml, respectively. Ten patients presented with pretreatment extent of disease (PRETEXT) stages III/IV multifocal tumours, eight with major vascular involvement, three with lung metastases and three with extrahepatic extension. The original pathology diagnoses were: HB in seven patients, HCC in two and HEMNOS in two. Our pathology review of pre-chemotherapy specimens showed that six tumours had equivocal/overlapping histological features of HB and HCC, four had predominant HB histology along with focal HCC-like histology and one had HB histology. Seven of nine post-chemotherapy resection specimens showed predominant HCC-like histology. Beta-catenin, glypican 3 and spalt-like transcription factor 4 immunostaining showed that all the tumours had a mixed HB/HCC immunophenotype. Telomerase reverse transcriptase immunostaining showed nuclear staining in nine of the 11 tumours. All patients received chemotherapy and achieved gross total primary tumour resection. Nine of the 11 patients were treated with established HB chemotherapy regimens. After a median follow-up of 6.1 years (range: 1.2-11.8 years), all patients were in remission.

CONCLUSIONS

HEMNOS is a subtype of HB with focal HCC-like histology, a high-risk clinical profile but favourable outcome following chemotherapy and complete tumour resection.

Gastric Cancer With Primitive Enterocyte Phenotype: An Aggressive Subgroup of Intestinal-type Adenocarcinoma

A primitive cell-like gene expression signature is associated with aggressive phenotypes of various cancers. We assessed the expression of phenotypic markers characterizing primitive cells and its correlation with clinicopathologic and molecular characteristics in gastric cancer. Immunohistochemical analysis of a panel of primitive phenotypic markers, including embryonic stem cell markers (OCT4, NANOG, SALL4, CLDN6, and LIN28) and known oncofetal proteins (AFP and GPC3), was performed using tissue microarray on 386 gastric cancers. On the basis of the expression profiles, the 386 tumors were clustered into 3 groups: group 1 (primitive phenotype, n=93): AFP, CLDN6, GPC3, or diffuse SALL4 positive; group 2 (SALL4-focal, n=56): only focal SALL4 positive; and group 3 (negative, n=237): all markers negative. Groups 1 and 2 predominantly consisted of intestinal-type adenocarcinoma, including 13 fetal gut-like adenocarcinomas exclusively in group 1. Group 1 was significantly associated with higher T-stage, presence of vascular invasion and nodal metastasis when compared with groups 2 and 3. Group 1 was associated with patients' poor prognosis and was an independent risk factor for disease-free survival. Group 1 showed frequent TP53 overexpression and little association with Epstein-Barr virus or mismatch repair deficiency. Further analysis of the Cancer Genome Atlas data set validated our observations and revealed that tumors with primitive phenotypes were mostly classified as "chromosomal instability" in the Cancer Genome Atlas' molecular classification. We identified gastric cancer with primitive enterocyte phenotypes as an aggressive subgroup of intestinal-type/chromosomal instability gastric cancer. Therapeutic strategies targeting primitive markers, such as GPC3, CLDN6, and SALL4, are highly promising.

SALL4 suppresses PTEN expression to promote glioma cell proliferation via PI3K/AKT signaling pathway

Spalt-like transcription factor 4 (SALL4), a oncogene, is known to participate in multiple carcinomas, and is up-regulated in glioma. However, its actual role and underlying mechanisms in the development of glioma remain unclear. The present study explored the molecular functions of SALL4 in promoting cell proliferation in glioma. The expression level of SALL4 in 69 human glioma samples and six non-tumor brain tissues was determined using real-time polymerase chain reaction (PCR). Then, we transfected U87 and U251 cell lines with siRNA, and assessed cellular proliferation and cell cycle to understand the function of SALL4, and the relationship between SALL4, PTEN and PI3K/AKT pathway. PCR confirmed that the expression of SALL4 was higher in the glioma samples than non-tumor brain tissues. Cellular growth and proliferation were dramatically reduced following inhibition of SALL4 expression. Western blot showed increase in PTEN expression when SALL4 was silenced, which in turn depressed the activation of PI3K/AKT pathway, suggesting that PTEN was a downstream target of SALL4 in glioma development. Therefore, SALL4 could act as a proto-oncogene by regulating the PTEN/PI3K/AKT signaling pathway, thereby facilitating proliferation of glioma cells.

Knockdown of SALL4 expression using RNA interference induces cell cycle arrest, enhances early apoptosis, inhibits invasion and increases chemosensitivity to temozolomide in U251 glioma cells

Spalt-like transcription factor 4 (SALL4) is essential for the maintenance of the self-renewal and pluripotent properties in embryonic stem cells. Although the detailed mechanism remains unclear, dysregulation of SALL4 has been detected in various malignancies. Previously, the authors' of the present study reported that the expression level of SALL4 was associated with the poor prognosis of glioblastoma multiforme (GBM). The present study aimed to investigate the function of SALL4 in U251 human glioblastoma cells, including apoptosis and invasion inhibition. It was revealed that knockdown of SALL4 expression through RNA interference induced cell cycle arrest, enhanced early apoptosis and significantly inhibited invasion. Furthermore, downregulation of SALL4 was associated with a significantly lower expression level of the core transcription factors, including POU class 5 homeobox 1, SRY-box 2 and Nanog homeobox. In addition, inhibition of SALL4 significantly reduced the concentration of chemotherapeutic agent temozolomide required to inhibit cell growth by 50%, which decreased from 113.66±23.07 and 114.93±20.91 µg/ml to 68.34±3.52 and 67.44±4.71 µg/ml in two independent short interfering RNA transfected groups. These results indicate that SALL4 serves an important role in the GBM pathophysiology and targeting SALL4 may be a potential approach to the treatment of GBM.

The Recent Advances on Liver Cancer Stem Cells: Biomarkers, Separation, and Therapy

As the third major reason of mortality related to cancer in the world, liver cancer is also the fifth most frequent cancer. Unluckily, a majority of patients succumb and relapse though many progresses have been made in detection and therapy of liver cancer. It has been put forward that in liver cancer, cancer stem cells (CSCs) hold main responsibility for the formation, invasion, metastasis, and recurrence of tumor. Strategies that are intended to target liver CSCs are playing a more and more significant role in supervising the development of liver cancer treatment and assessing new therapeutic methods. Herein, a brief review about molecule markers, signal pathways, separation, and treatment on liver cancer stem cells (LCSCs) is provided in this paper.

The MBNL3 splicing factor promotes hepatocellular carcinoma by increasing PXN expression through the alternative splicing of lncRNA-PXN-AS1

Understanding the roles of splicing factors and splicing events during tumorigenesis would open new avenues for targeted therapies. Here we identify an oncofetal splicing factor, MBNL3, which promotes tumorigenesis and indicates poor prognosis of hepatocellular carcinoma patients. MBNL3 knockdown almost completely abolishes hepatocellular carcinoma tumorigenesis. Transcriptomic analysis revealed that MBNL3 induces lncRNA-PXN-AS1 exon 4 inclusion. The transcript lacking exon 4 binds to coding sequences of PXN mRNA, causes dissociation of translation elongation factors from PXN mRNA, and thereby inhibits PXN mRNA translation. In contrast, the transcript containing exon 4 preferentially binds to the 3' untranslated region of PXN mRNA, protects PXN mRNA from microRNA-24-AGO2 complex-induced degradation, and thereby increases PXN expression. Through inducing exon 4 inclusion, MBNL3 upregulates PXN, which mediates the pro-tumorigenic roles of MBNL3. Collectively, these data demonstrate detailed mechanistic links between an oncofetal splicing factor, a splicing event and tumorigenesis, and establish splicing factors and splicing events as potential therapeutic targets.

Mixed hepatocellular cholangiocarcinoma tumors: Cholangiolocellular carcinoma is a distinct molecular entity

BACKGROUND & AIMS

Mixed hepatocellular cholangiocarcinoma (HCC-CCA) is a rare and poorly understood type of primary liver cancer. We aimed to perform a comprehensive molecular characterization of this malignancy.

METHODS

Gene expression profiling, DNA copy number detection, and exome sequencing using formalin-fixed samples from 18 patients with mixed HCC-CCA were performed, encompassing the whole histological spectrum of the disease. Comparative genomic analysis was carried out, using independent datasets of HCC (n=164) and intrahepatic cholangiocarcinoma (iCCA) (n=149).

RESULTS

Integrative genomic analysis of HCC-CCAs revealed that cholangiolocellular carcinoma (CLC) represents a distinct biliary-derived entity compared with the stem-cell and classical types. CLC tumors were neural cell adhesion molecule (NCAM) positive (6/6 vs. 1/12, p<0.001), chromosomally stable (mean chromosomal aberrations 5.7 vs. 14.1, p=0.008), showed significant upregulation of transforming growth factor (TGF)-β signaling and enrichment of inflammation-related and immune response signatures (p<0.001). Stem-cell tumors were characterized by spalt-like transcription factor 4 (SALL4) positivity (6/8 vs. 0/10, p<0.001), enrichment of progenitor-like signatures, activation of specific oncogenic pathways (i.e., MYC and insulin-like growth factor [IGF]), and signatures related to poor clinical outcome. In the classical type, there was a significant correlation in the copy number variation of the iCCA and HCC components, suggesting a clonal origin. Exome sequencing revealed an average of 63 non-synonymous mutations per tumor (2 mean driver mutations per tumor). Among those, TP53 was the most frequently mutated gene (6/21, 29%) in HCC-CCAs.

CONCLUSIONS

Mixed HCC-CCA represents a heterogeneous group of tumors, with the stem-cell type characterized by features of poor prognosis, and the classical type with common lineage for HCC and iCCA components. CLC stands alone as a distinct biliary-derived entity associated with chromosomal stability and active TGF-β signaling.

LAY SUMMARY

Molecular analysis of mixed hepatocellular cholangiocarcinoma (HCC-CCA) showed that cholangiolocellular carcinoma (CLC) is distinct and biliary in origin. It has none of the traits of hepatocellular carcinoma (HCC). However, within mixed HCC-CCA, stem-cell type tumors shared an aggressive nature and poor outcome, whereas the classic type showed a common cell lineage for both the HCC and the intrahepatic CCA component. The pathological classification of mixed HCC-CCA should be redefined because of the new molecular data provided.

DNA demethylation induces SALL4 gene re-expression in subgroups of hepatocellular carcinoma associated with Hepatitis B or C virus infection

Sal-like protein 4 (SALL4), an embryonic stem cell transcriptional regulator, is re-expressed by an unknown mechanism in poor prognosis hepatocellular carcinoma (HCC), often associated with chronic hepatitis B virus (HBV) infection. Herein, we investigated the mechanism of SALL4 re-expression in HBV-related HCCs. We performed bisulfite sequencing PCR of genomic DNA isolated from HBV-related HCCs and HBV replicating cells, and examined DNA methylation of a CpG island located downstream from SALL4 transcriptional start site (TSS). HBV-related HCCs expressing increased SALL4 exhibited demethylation of specific CpG sites downstream of SALL4 TSS. Similarly, SALL4 re-expression and demethylation of these CpGs was observed in HBV replicating cells. SALL4 is also re-expressed in poor prognosis HCCs of other etiologies. Indeed, increased SALL4 expression in hepatitis C virus-related HCCs correlated with demethylation of these CpG sites. To understand how CpG demethylation downstream of SALL4 TSS regulates SALL4 transcription, we quantified by chromatin immunoprecipitation (ChIP) assays RNA polymerase II occupancy of SALL4 gene, as a function of HBV replication. In absence of HBV replication, RNA polymerase II associated with SALL4 exon1. By contrast, in HBV replicating cells RNA polymerase II occupancy of all SALL4 exons increased, suggesting CpG demethylation downstream from SALL4 TSS influences SALL4 transcriptional elongation. Intriguingly, demethylated CpGs downstream from SALL4 TSS are within binding sites of octamer-binding transcription factor 4 (OCT4) and signal transducer and activator of transcription3 (STAT3). ChIP assays confirmed occupancy of these sites by OCT4 and STAT3 in HBV replicating cells, and sequential ChIP assays demonstrated co-occupancy with chromatin remodeling BRG1/Brahma-associated factors. BRG1 knockdown reduced SALL4 expression, whereas BRG1 overexpression increased SALL4 transcription in HBV replicating cells. We conclude demethylation of CpGs located within OCT4 and STAT3 cis-acting elements, downstream of SALL4 TSS, enables OCT4 and STAT3 binding, recruitment of BRG1, and enhanced RNA polymerase II elongation and SALL4 transcription.

Long noncoding RNA AWPPH promotes hepatocellular carcinoma progression through YBX1 and serves as a prognostic biomarker

Long noncoding RNAs (lncRNAs) have been shown to play important roles in various cancers. However, the clinical significances and biological roles of lncRNAs in hepatocellular carcinoma (HCC) remain largely unknown. In this study, using online-available data sets and quantitative real-time PCR, we identified a novel lncRNA termed lncRNA-AWPPH, which is highly expressed in HCC tissues. Its upregulation is correlated with encapsulation incomplete, microvascular invasion, advanced TNM stage and BCLC stage. Cox proportional hazards regression analysis revealed that high lncRNA-AWPPH expression is an independent prognostic factor for poor recurrence-free and overall survival. Functional experiments showed that overexpression of lncRNA-AWPPH promotes HCC cell proliferation and migration in vitro, and tumor growth and metastasis in vivo. Conversely, depletion of lncRNA-AWPPH has opposite effects on HCC. Mechanistically, lncRNA-AWPPH interacts with YBX1, promotes YBX1-mediated activation of SNAIL1 translation, and upregulates SNAIL1 expression. Furthermore, lncRNA-AWPPH promotes YBX1-mediated activation of PIK3CA transcription, upregulates PIK3CA expression, and activates PI3K/AKT pathway. Depletion of YBX1 abolishes the effects of lncRNA-AWPPH on SNAIL1 and PIK3CA, and also the biological roles of lncRNA-AWPPH on HCC cells. In conclusion, this study identifies a novel lncRNA termed lncRNA-AWPPH which is highly expressed in HCC, indicates poor prognosis of HCC patients, and promotes HCC cell proliferation, migration, and in vivo tumor growth and metastasis via a novel regulatory mechanism of interacting with YBX1.

Coexpression of SALL4 with HDAC1 and/or HDAC2 is associated with underexpression of PTEN and poor prognosis in patients with hepatocellular carcinoma

Spalt-like transcriptional factor 4 (SALL4), a stem marker, is reactivated in several cancers. A previous study has demonstrated that SALL4 interacts with the nucleosome remodeling deacetylase complex, which contains histone deacetylase 1 (HDAC1) and histone deacetylase 2 (HDAC2). In this study, we investigated the expression status of SALL4, HDAC1, and HDAC2 and their relationship with phosphatase and tensin homolog deleted on chromosome 10 (PTEN) by immunohistochemical analysis of the posthepatectomy specimens of 135 patients with hepatocellular carcinoma who were treated at our hospital. Ninety-two frozen samples were subjected to quantitative reverse-transcription polymerase chain reaction analysis to detect the messenger RNA levels of PTEN. Seventy-six (56%) of 135 patients were positive for SALL4, and this group had a higher prevalence of hepatitis B antigen, a higher value of α-fetoprotein (AFP) and protein induced by vitamin K absence (PIVKAII) and poor histologic differentiation. The 5-year survival rate was significantly lower in the SALL4-positive group. High HDAC1 expression (51%) was correlated with a poor histologic differentiation and a poor prognosis. High HDAC2 expression (46%) was associated with a higher prevalence of hepatitis B antigen positivity, a poor histologic differentiation and higher prevalence of vascular invasion, and a lower 5-year survival rate. Coexpression of SALL4 with HDAC1 and/or HDAC2 was correlated with underexpression of PTEN. Moreover, multivariable analysis revealed that coexpression of SALL4 with HDAC1 and/or HDAC2 was predictive of an unfavorable prognosis. Our data thus suggested that the combination of SALL4, HDAC1, and HDAC2 may provide a potential target for molecular therapy.

Actin-like protein 6A is a novel prognostic indicator promoting invasion and metastasis in osteosarcoma

Osteosarcoma harbors highly metastatic properties, accounting for postoperative recurrence and metastasis. Actin-like protein 6A (ACTL6A) regulates cell proliferation, migration and differentiation. However, the biologic role of ACTL6A in osteosarcoma remains unknown. In this study, the results showed that, by analysis of frozen fresh primary tumor tissues, matched non-cancerous bone tissues (NCBTs) and biopsy lung metastatic nodule tissues from 30 osteosarcoma patients after radical surgical resection, ACTL6A was overexpressed in osteosarcoma tissues compared with matched NCBTs, and its expression level was associated with osteosarcoma metastasis. Immunohistochemical analyses of osteosarcoma tissue samples from two independent cohorts of formaldehyde-fixed, paraffin-embedded osteosarcoma tissue samples from total of 186 osteosarcoma patients showed that high ACTL6A expression correlated with malignant clinicopathological features such as larger tumor size, high Ennecking grade, high histologic grade, and advanced tumor node metastasis stage. High ACTL6A expression was associated with poor prognosis for patients with osteosarcoma, and an independent and significant risk factor for disease-free survival and overall survival after radical tumor resection. Both in vitro and in vivo assays showed that ACTL6A overexpression promoted osteosarcoma cell invasion and metastasis, whereas knockdown of ACTL6A expression reduced osteosarcoma cell malignant behavior such as invasion and metastasis. Furthermore, we proved that ACTL6A promoted osteosarcoma cells of metastasis through facilitating epithelial-mesenchymal transition (EMT). In conclusion, data from the present study demonstrated that ACTL6A was associated with poor survival and promoted osteosarcoma cell metastasis through EMT, suggesting that ACTL6A may be a novel prognostic biomarker and therapeutic target for osteosarcoma.

DNA repair mechanisms in embryonic stem cells

Embryonic stem cells (ESCs) can undergo unlimited self-renewal and retain the pluripotency to differentiate into all cell types in the body. Therefore, as a renewable source of various functional cells in the human body, ESCs hold great promise for human cell therapy. During the rapid proliferation of ESCs in culture, DNA damage, such as DNA double-stranded breaks, will occur in ESCs. Therefore, to realize the potential of ESCs in human cell therapy, it is critical to understand the mechanisms how ESCs activate DNA damage response and DNA repair to maintain genomic stability, which is a prerequisite for their use in human therapy. In this context, it has been shown that ESCs harbor much fewer spontaneous mutations than somatic cells. Consistent with the finding that ESCs are genetically more stable than somatic cells, recent studies have indicated that ESCs can mount more robust DNA damage responses and DNA repair than somatic cells to ensure their genomic integrity.

Cell Cycle M-Phase Genes Are Highly Upregulated in Anaplastic Thyroid Carcinoma

BACKGROUND

Anaplastic thyroid carcinoma (ATC) accounts for only 3% of thyroid cancers, yet strikingly, it accounts for almost 40% of thyroid cancer deaths. Currently, no effective therapies exist. In an effort to identify ATC-specific therapeutic targets, we analyzed global gene expression data from multiple studies to identify ATC-specific dysregulated genes.

METHODS

The National Center for Biotechnology Information Gene Expression Omnibus database was searched for high-throughput gene expression microarray studies from human ATC tissue along with normal thyroid and/or papillary thyroid cancer (PTC) tissue. Gene expression levels in ATC were compared with normal thyroid or PTC using seven separate comparisons, and an ATC-specific gene set common in all seven comparisons was identified. We investigated these genes for their biological functions and pathways.

RESULTS

There were three studies meeting inclusion criteria, (including 32 ATC patients, 69 PTC, and 75 normal). There were 259 upregulated genes and 286 downregulated genes in ATC with at least two-fold change in all seven comparisons. Using a five-fold filter, 36 genes were upregulated in ATC, while 40 genes were downregulated. Of the 10 top globally upregulated genes in ATC, 4/10 (MMP1, ANLN, CEP55, and TFPI2) are known to play a role in ATC progression; however, 6/10 genes (TMEM158, CXCL5, E2F7, DLGAP5, MME, and ASPM) had not been specifically implicated in ATC. Similarly, 3/10 (SFTA3, LMO3, and C2orf40) of the most globally downregulated genes were novel in this context, while 7/10 genes (SLC26A7, TG, TSHR, DUOX2, CDH1, PDE8B, and FOXE1) have been previously identified in ATC. We experimentally validated a significant correlation for seven transcription factors (KLF16, SP3, ETV6, FOXC1, SP1, EGFR1, and MAFK) with the ATC-specific genes using microarray analysis of ATC cell lines. Ontology clustering of globally altered genes revealed that "mitotic cell cycle" is highly enriched in the globally upregulated gene set (44% of top upregulated genes, p-value <10^-30).

CONCLUSIONS

By focusing on globally altered genes, we have identified a set of consistently altered biological processes and pathways in ATC. Our data are consistent with an important role for M-phase cell cycle genes in ATC, and may provide direction for future studies to identify novel therapeutic targets for this disease.

The evolving concept of liver cancer stem cells

Liver cancer is an often fatal malignant tumor with a high recurrence rate and chemoresistance. The major malignant phenotypes of cancer, including recurrence, metastasis, and chemoresistance, are related to the presence of cancer stem cells (CSCs). In the past few decades, CSCs have been identified and characterized in many tumors including liver cancer. Accumulated evidence has revealed many aspects of the biological behavior of liver CSCs and the mechanism of their regulation. Based on these findings, a number of studies have investigated eradication of liver CSCs. This review focuses on the recent advances in our understanding of the biology of liver CSCs and the development of strategies for their treatment.

IGF2 Is Up-regulated by Epigenetic Mechanisms in Hepatocellular Carcinomas and Is an Actionable Oncogene Product in Experimental Models

BACKGROUND & AIMS

Effective treatments are urgently needed for hepatocellular carcinoma (HCC), which is usually diagnosed at advanced stages. Signaling via the insulin-like growth factor (IGF) pathway is aberrantly activated in HCC by IGF2 overexpression. We aimed to elucidate the mechanism of IGF2 overexpression and its oncogenic activities and evaluate the anti-tumor effects of reducing IGF2 signaling.

METHODS

We obtained 228 HCC samples from patients who underwent liver resection, 168 paired non-tumor adjacent cirrhotic liver samples, and 10 non-tumor liver tissues from patients undergoing resection for hepatic hemangioma. We analyzed gene expression, microRNA, and DNA methylation profiles for all samples, focusing on genes in the IGF signaling pathway. IGF2 was expressed in SNU449 and PLC5 HCC cells and knocked down with small hairpin RNAs in Hep3B and Huh7 cell lines. We analyzed these cells for proliferation, apoptosis, migration, and colony formation. We performed studies in mice engineered to express Myc and Akt1 in liver, which develop liver tumors, with or without hepatic expression of Igf2. Mice with xenograft tumors grown from HCC cells were given a monoclonal antibody against IGF1 and IGF2 (xentuzumab), along with sorafenib; tumor growth was measured and tissues were analyzed by immunohistochemistry and immunoblots.

RESULTS

Levels of IGF2 messenger RNA and protein were increased >20-fold in 15% of human HCC tissues compared with non-tumor liver tissues. Methylation at the fetal promoters of IGF2 was reduced in the HCC samples and cell lines that overexpressed IGF2, compared with those that did not overexpress this gene, and non-tumor tissues. Tumors that overexpressed IGF2 had gene expression patterns significantly associated with hepatic progenitor cell features, stellate cell activation, NOTCH signaling, and an aggressive phenotype (P < .0001). In mice engineered to express Myc and Akt1 in liver, co-expression of Igf2 accelerated formation of liver tumors, compared to mice with livers expressing only Myc and Akt1, and shortened survival times (P = .02). The antibody xentuzumab blocked phosphorylation of IGF1 receptor in HCC cell lines and reduced their proliferation and colony formation. In mice with xenograft tumors, injection of xentuzumab, with or without sorafenib, slowed tumor growth and increased survival times compared to vehicle or sorafenib alone. Xentuzumab inhibited phosphorylation of IGF1 receptor and AKT and reduced decreased tumor vascularization compared with vehicle.

CONCLUSIONS

A large proportion of HCC samples were found to overexpress IGF2, via demethylation of its fetal promoter. Overexpression of IGF2 accelerates formation of liver tumors in mice with hepatic expression of MYC and AKT1, via activation of IGF1 receptor signaling. An antibody against IGF1 and IGF2 slows growth of xenograft tumors and increases survival of these mice.

MicroRNA-98 Plays a Suppressive Role in Non-Small Cell Lung Cancer Through Inhibition of SALL4 Protein Expression

MicroRNAs (miRs) have been demonstrated to be significantly associated with the development and progression of non-small cell lung cancer (NSCLC). However, the underlying mechanism of miR-98 in mediating the malignant phenotypes of NSCLC cells remains obscure. In this study, we found that miR-98 was significantly downregulated in NSCLC tissues compared to nontumor lung tissues. Downregulation of miR-98 was significantly associated with poor differentiation and advanced clinical stage. Restoration of miR-98 expression significantly decreased the proliferation, migration, and invasion of NSCLC A549 and H1229 cells. SALL4 was identified as a target gene of miR-98, and the protein expression of SALL4 was negatively regulated by miR-98 in NSCLC A549 and H1229 cells. Overexpression of SALL4 promoted A549 and H1229 cell proliferation, migration, and invasion and reversed the suppressive effects of miR-98 on the malignant phenotypes of A549 and H1229 cells. Moreover, SALL4 was found to be significantly upregulated in NSCLC tissues compared to the nontumor lung tissues. We then observed an inverse correlation between the miR-98 and SALL4 levels in NSCLC tissues. In vivo study revealed that miR-98 overexpression suppressed NSCLC growth. In summary, we demonstrate that miR-98 acts as a tumor suppressor in NSCLC cells by inhibiting the protein expression of its target gene SALL4. Therefore, our study highlights the importance of the miR-98/SALL4 axis in NSCLC.

SALL4 promotes gastric cancer progression through activating CD44 expression

The stem cell factor SALL4 (Sal-like protein 4) plays important roles in the development and progression of cancer. SALL4 is critically involved in tumour growth, metastasis and therapy resistance. However, the underlying mechanisms responsible for the oncogenic roles of SALL4 have not been well characterized. In this study, we demonstrated that SALL4 knockdown by short hairpin RNA greatly inhibited the proliferation, migration and invasion of gastric cancer cells. We further confirmed the inhibitory effects of SALL4 knockdown on gastric cancer cells by using a tetracycline-inducible system. Mechanistically, SALL4 knockdown downregulated the expression of CD44. The results of luciferase assay and chromatin immunoprecipitation study showed that SALL4 bound to CD44 promoter region and transcriptionally activated CD44. The results of rescue study revealed that CD44 overexpression antagonized SALL4 knockdown-mediated inhibition of gastric cancer cell proliferation, migration, and invasion in vitro and gastric cancer growth in vivo. Collectively, our findings indicate that SALL4 promotes gastric cancer progression through directly activating CD44 expression, which suggests a novel mechanism for the oncogenic roles of SALL4 in gastric cancer and represents a new target for gastric cancer therapy.

The Sal-like 4 - integrin α6β1 network promotes cell migration for metastasis via activation of focal adhesion dynamics in basal-like breast cancer cells

During metastasis, cancer cell migration is enhanced. However, the mechanisms underlying this process remain elusive. Here, we addressed this issue by functionally analyzing the transcription factor Sal-like 4 (SALL4) in basal-like breast cancer cells. Loss-of-function studies of SALL4 showed that this transcription factor is required for the spindle-shaped morphology and the enhanced migration of cancer cells. SALL4 also up-regulated integrin gene expression. The impaired cell migration observed in SALL4 knockdown cells was restored by overexpression of integrin α6 and β1. In addition, we clarified that integrin α6 and β1 formed a heterodimer. At the molecular level, loss of the SALL4 - integrin α6β1 network lost focal adhesion dynamics, which impairs cell migration. Over-activation of Rho is known to inhibit focal adhesion dynamics. We observed that SALL4 knockdown cells exhibited over-activation of Rho. Aberrant Rho activation was suppressed by integrin α6β1 expression, and pharmacological inhibition of Rho activity restored cell migration in SALL4 knockdown cells. These results indicated that the SALL4 - integrin α6β1 network promotes cell migration via modulation of Rho activity. Moreover, our zebrafish metastasis assays demonstrated that this gene network enhances cell migration in vivo. Our findings identify a potential new therapeutic target for the prevention of metastasis, and provide an improved understanding of cancer cell migration.

Splenectomy suppresses growth and metastasis of hepatocellular carcinoma through decreasing myeloid-derived suppressor cells in vivo

The function of the spleen in tumor development has been investigated for years. The relationship of the spleen with hepatocellular carcinoma (HCC), a huge health burden worldwide, however, remains unknown. The present study aimed to examine the effect of splenectomy on the development of HCC and the possible mechanism. Mouse hepatic carcinoma lines H22 and Hepa1-6 as well as BALB/c and C57 mice were used to establish orthotopic and metastatic mouse models of liver cancer. Mice were divided into four groups, including control group, splenectomy control group (S group), tumor group (T group) and tumor plus splenectomy group (T+S group). Tumor growth, metastases and overall survival were assessed at determined time points. Meanwhile, myeloid-derived suppressor cells (MDSCs) were isolated from the peripheral blood (PB), the spleen and liver tumors, and then measured by flow cytometery. It was found that liver cancer led to splenomegaly, and increased the percentage of MDSCs in the PB and spleen in the mouse models. Splenectomy inhibited the growth and progression of liver cancer and prolonged the overall survival time of orthotopic and metastatic models, which was accompanied by decreased proportion of MDSCs in the PB and tumors of liver cancer-bearing mouse. It was suggested that splenectomy could be considered an adjuvant therapy to treat liver cancer.

Clinical Significance of Epigenetic Alterations in Human Hepatocellular Carcinoma and Its Association with Genetic Mutations

Accumulation of genetic and epigenetic alterations is a hallmark of cancer genomes, including those in hepatocellular carcinoma (HCC). Particularly, in human HCC, epigenetic changes are more frequently observed than genetic changes in a variety of cancer-related genes, suggesting a potential role for epigenetic alterations during hepatocarcinogenesis. Several environmental factors, such as inflammation, obesity, and steatosis, are reported to affect the epigenetic status in hepatocytes, which could play a role in HCC development. In addition, genetic mutations in histone modulators and chromatin regulators would be critical for the acceleration of epigenetic alteration. It is also possible that major genetic mutations of HCC, such as TP53 and CNTTB1 mutations, are associated with the disturbance of epigenetic integrity. For example, specific TP53 mutations frequently induced by aflatoxin B1 exposure might affect histone modifiers and nucleosome remodelers. Generally, epigenetic alteration is reversible, because of which dysregulation of transcription takes place, without affecting protein structure. Therefore, differentiation therapy is one of the potential approaches for HCC with advanced epigenetic alterations. On the other hand, a tumor carrying an accumulation of genetic mutations would result in many abnormal proteins that could be recognized as non-self and could be targets for immune reactions; thus, immune-checkpoint blockers should be effective for HCCs with genetic hypermutation. Although the emergence of genetic and epigenetic alterations could be linked to each other and there could be some crossover or convergence between these cancer pathways, characterization of the mutation spectrum of genetic and epigenetic alterations could influence future HCC treatment.

Ginsenoside exhibits concentration-dependent dual effects on HepG2 cell proliferation via regulation of c-Myc and HNF-4α

Although ginsenoside can generally promote cell proliferation, it is reported to have anti-proliferative effects in hepatocellular carcinoma (HCC). Whether ginsenoside has concentration-dependent effects on HCC cell proliferation have not been clarified. Transcription factors c-Myc and hepatocyte nuclear factor (HNF)-4α are the most important opposite controllers of HCC cell proliferation. Whether and how ginsenoside regulates c-Myc and HNF-4α as well as their recruitment of the co-activator p300 to exhibit its effects on HCC cell proliferation are pending. In this study, it was found that low concentration ginsenoside promoted HepG2 cell proliferation while high concentration ginsenoside exhibited anti-proliferation effect. For low concentration ginsenoside treatment, c-Myc was up-regulated and the binding of p300 to c-Myc was promoted with obvious co-localization to activate HepG2 cell proliferation. However, for high concentration ginsenoside treatment, besides c-Myc, HNF-4α was also up-regulated might to exhibit an alternative effect. Furthermore, in contrast to the weakened binding and co-localization of c-Myc and p300, the binding of p300 to HNF-4α was enhanced with distinct co-localization to inhibit HepG2 cell proliferation for high concentration ginsenoside treatment. The results manifested that ginsenoside with low and high concentrations may differentially regulate c-Myc and HNF-4α as well as their recruitments of p300, to exhibit concentration-dependent dual effects on HepG2 cell proliferation.

MicroRNA-33b suppresses the proliferation and metastasis of hepatocellular carcinoma cells through the inhibition of Sal-like protein 4 expression

MicroRNAs (miRNAs or miRs) have been found to participate in the development and malignant progression of human cancers by negatively mediating the expression of their target genes. Recently, miR‑33b has been reported to be involved in multiple types of human cancer, including hepatocellular carcinoma (HCC). However, the underlying regulatory mechanisms of miR‑33b in HCC cell growth and metastasis remain largely unclear. In the present study, RT-qPCR revealed that miR‑33b was significantly downregulated in HCC tissues compared to their matched adjacent normal tissues. Moreover, the miR‑33b level was significantly lower in advanced-stage HCC (stages T3-T4) compared to early-stage HCC (stages T1-T2). Furthermore, it was also downregulated in the HCC cell lines, LH86, HepG2, LMH and PLHC-1, when compared with the THLE-3 normal human liver cells. We further demonstrated that the overexpression of miR‑33b led to a significant decrease in the proliferation, migration and invasion of HepG2 and LH86 cells. Luciferase reporter assay identified Sal-like protein 4 (SALL4) as a target gene of miR‑33b, and its protein expression was negatively regulated by miR‑33b in HepG2 and LH86 cells. Moreover, the restoration of SALL4 expression markedly reversed the inhibitory effect of miR‑33b overexpression on the proliferation, migration and invasion of HepG2 and LH86 cells, indicating that SALL4 is involved in miR‑33b-mediated malignant phenotypes of HCC cells. Furthermore, we found that SALL4 was significantly upregulated in HCC tissues compared to their matched adjacent normal tissues, and its increased expression was significantly associated with the advanced malignancy of HCC. Moreover, SALL4 was also upregulated in HCC cell lines compared to the THLE-3 normal human liver cells. Finally, we found that the SALL4 expression inversely correlated with the miR‑33b level in HCC tissues. On the whole, the findings of our study demonstrate that miR‑33b suppresses the proliferation and metastasis of HCC cells through the inhibition of SALL4 expression. Therefore, miR‑33b/SALL4 may become a potential therapeutic target for the treatment of HCC.

Comparison of hepatocellular carcinoma in Eastern versus Western populations

Hepatocellular carcinoma (HCC) is a heterogeneous disease that remains highly prevalent in many Asian countries and is the second most common cause of cancer-related mortality worldwide. Significant differences exist between Eastern and Western populations on many key aspects of HCC, contributing to the potential different treatment outcomes and challenges of clinical trial design and data interpretation. In this review, the authors compare HCC in Asia versus the West and highlight 1) differences in terms of epidemiology and trends and their correlation with etiology, 2) differences in genetics and how they relate to underlying etiology, 3) differences in treatment approaches based on existing guidelines and consensus statements, and 4) differences in clinical outcomes for Asian versus non-Asian patients with HCC in clinical trials and the implications for future clinical trial design. Cancer 2016;122:3430-3446. © 2016 American Cancer Society.

Knockdown of Sall4 inhibits intrahepatic cholangiocarcinoma cell migration and invasion in ICC-9810 cells

In spite of improvements in surgical technology, the resectability and curability of intrahepatic cholangiocarcinoma (ICC) are still low. Our previous study showed that the strong Sal-like protein 4 (Sall4)-positive cases had shorter overall survival compared to Sall4-negative cases, indicating an oncogenic role of Sall4 in ICC. In this study, we aimed to explore the precise mechanism of Sall4 on ICC cell invasion and metastasis. We evaluated the expression of Sall4, PTEN, and Bmi-1 in 28 cases of adjacent tissues and 175 cases of ICC tissues by using immunohistochemical staining. We found that the expression of Sall4 and Bmi-1 was significantly increased in ICC tissues compared with the adjacent tissues, while PTEN expression was reduced in ICC tissues compared with the adjacent tissues, and there was a reverse relationship between Sall4 and PTEN in ICC, whereas there was a positive correlation in Sall4 and Bmi-1 expression in ICC. In addition, overall survival analysis showed that ICC patients with low PTEN exhibited a worse prognosis than ICC patients with high PTEN, and lower Bmi-1 expression showed a better prognosis than ICC patients with high Bmi-1. By a battery of experiments in vitro, we demonstrated that Sall4 promotes ICC cell proliferation, and progression of ICC might be through PTEN/PI3K/Akt and Bmi-1/Wnt/β-catenin signaling and enhancing epithelial-mesenchymal transition process. Thus, Sall4 may be a potential target for the treatment of ICC metastasis.

SALL4 is a novel therapeutic target in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is the most common and deadly disease of the biliary tree due to its poor prognosis. Sal-like protein 4 (SALL4), a stem cell marker, has been identified as a potential target for aggressive hepatocellular carcinoma (HCC). In our study, 175 ICC cases with an average age of 55 years were included, and 53% (93/175) were male. And 28 adjacent non-tumor tissues were also collected. The SALL4-positive immunoreactivity was detected in a total of 102 ICC cases (58%), whereas all 28 adjacent tissues showed negative staining. Univariate analysis, showed that the SALL4-positive ICC cases had significantly more frequent lymph nodal metastasis (P = 0.0460), vascular invasion (P < 0.0001), and nerve invasion (P < 0.0001). Furthermore, the strong SALL4-positive cases (n = 7, 5 months) had shorter overall survival, when compared to moderate SALL4-positive (n = 46, 9 months) or SALL4-negative cases (n = 73, 7 months), respectively. Our data also suggest that SALL4 may be involved in the regulation of epithelial-mesenchymal transition (EMT) in ICC. Those results for the first time indicate an oncogenic role of SALL4 in ICC. Therefore, SALL4 may serve as a promising therapeutic target for ICC.

The Progress and Prospects of Putative Biomarkers for Liver Cancer Stem Cells in Hepatocellular Carcinoma

Accumulating evidence suggests that hepatocellular carcinoma (HCC) is organized by liver cancer stem cells (LCSCs), which are a subset of cells with “stem-like” characteristics. Identification of the LCSCs is a fundamental and important problem in HCC research. LCSCs have been investigated by various stem cell biomarkers. There is still lack of consensus regarding the existence of a “global” marker for LCSCs in HCC. In this review article, we summarize the progress and prospects of putative biomarkers for LCSCs in the past decades, which is essential to develop future therapies targeting CSCs and to predict prognosis and curative effect of these therapies.

The diagnostic and prognostic value of SALL4 in hepatoblastoma

AIMS

To investigate the expression of spalt-like transcription factor 4 (SALL4), a regulator of embryonal development, in three epithelial components of hepatoblastoma (HB) and the relationship between SALL4 expression levels and patients' clinicopathological features.

METHODS AND RESULTS

A total of 115 specimens from 79 patients with HB were selected for immunostaining of SALL4. Nuclear staining was semi-quantified using the immunoreactive score (IS; range: 0-12). SALL4 expression was seen in all embryonal components (mean IS = 8.58) and in 41% of fetal components (mean IS = 0.78). No SALL4 expression was seen in either small cell undifferentiated or mesenchymal components of HB. Neither chemotherapy nor metastasis altered SALL4 expression significantly. High SALL4 expression levels were associated significantly with decreased overall survival (OS) (P = 0.004), event-free survival (EFS) (P = 0.003) and the presence of metastasis (P = 0.049) on univariate analysis. Multivariate analysis identified SALL4 as an independent prognostic predictor for OS (P = 0.029).

CONCLUSIONS

SALL4 is useful for subtyping HB, and high SALL4 expression is associated with decreased survival in HB.

Positive immunostaining of Sal-like protein 4 is associated with poor patient survival outcome in the large and undifferentiated Korean hepatocellular carcinoma

PURPOSE

Previous studies have shown the role of Sal-like protein 4 (SALL4) as a biomarker in hepatocellular carcinoma (HCC), and some studies have shown the relationship between SALL4 and prognosis. Given the debates in study groups differences in terms of etiologic causes between Western and Asian HCC and detection methods, we attempted to verify the features of SALL4 immunoreactivity and its clinical correlation in Korean HCC patients.

METHODS

Immunohistochemical staining of SALL4 of tissue microarrays (TMAs) consisting of 213 surgically resected HCC patients' tissue were scored in a semiquantitative scoring system with immunoreactive score and the results analyzed with clinical outcome, in addition to general demographics and clinical characteristics.

RESULTS

SALL4 immunoreactivity was expressed in 50 cases. Relevance between SALL4 and α-FP correlated significantly (P = 0.002). Also, the SALL4-positive patients had considerably higher tumor grade (P < 0.001). The survival analysis showed negative correlation with SALL4 immunoreactivity in all HCC patient groups, but SALL4 immunoreactivity in T3 and T4 HCC correlated with poor prognosis.

CONCLUSION

Here, we found that positive immunostaining of SALL4 is correlated with poor patient survival outcome in large and undifferentiated Korean HCC. SALL4 expression showed close relationship with clinical outcomes of HCCs in Korean patients.

Developmental Stage-Specific Embryonic Induction of HepG2 Cell Differentiation

BACKGROUND

Although hepatocellular carcinoma cells can sometimes undergo differentiation in an embryonic microenvironment, the mechanism is poorly understood.

AIM

The developmental stage-specific embryonic induction of tumor cell differentiation was investigated.

METHODS

Both chick and mouse liver extracts and hepatoblast-enriched cells at different developmental stages were used to treat human hepatoma HepG2 cells, and the effects on the induction of differentiation were evaluated. The nuclear factors controlling differentiation, hepatocyte nuclear factor (HNF)-4α, HNF-1α, HNF-6 and upstream stimulatory factor-1 (USF-1), and the oncogene Myc and alpha-fetoprotein (AFP) were measured. HNF-4α RNA interference was used to verify the role of HNF-4α. Embryonic induction effects were further tested in vivo by injecting HepG2 tumor cells into immunodeficient nude mice.

RESULTS

The 9-11-days chick liver extracts and 13.5-14.5-days mouse hepatoblast-enriched cells could inhibit proliferation and induce differentiation of HepG2 cells, leading to either death or maturation to hepatocytes. The maturation of surviving HepG2 cells was confirmed by increases in the expressions of HNF-4α, HNF-1α, HNF-6, and USF-1, and decreases in Myc and AFP. The embryonic induction of HepG2 cell maturation could be attenuated by HNF-4α RNA interference. Furthermore, the 13.5-days mouse hepatoblast culture completely eliminated HepG2 tumors with inhibited Myc and induced HNF-4α, confirming this embryonic induction effect in vivo.

CONCLUSIONS

This study demonstrated that developmental stage-specific embryonic induction of HepG2 cell differentiation might help in understanding embryonic differentiation and oncogenesis.

SALL4, the missing link between stem cells, development and cancer

There is a growing body of evidence supporting that cancer cells share many similarities with embryonic stem cells (ESCs). For example, aggressive cancers and ESCs share a common gene expression signature that includes hundreds of genes. Since ESC genes are not present in most adult tissues, they could be ideal candidate targets for cancer-specific diagnosis and treatment. This is an exciting cancer-targeting model. The major hurdle to test this model is to identify the key factors/pathway(s) within ESCs that are responsible for the cancer phenotype. SALL4 is one of few genes that can establish this link. The first publication of SALL4 is on its mutation in a human inherited disorder with multiple developmental defects. Since then, over 300 papers have been published on various aspects of this gene in stem cells, development, and cancers. This review aims to summarize our current knowledge of SALL4, including a SALL4-based approach to classify and target cancers. Many questions about this important gene still remain unanswered, specifically, on how this gene regulates cell fates at a molecular level. Understanding SALL4's molecular functions will allow development of specific targeted approaches in the future.

The zinc-finger transcription factor SALL4 is frequently expressed in human cancers: association with clinical outcome in squamous cell carcinoma but not in adenocarcinoma of the esophagus

SALL4 is a transcription factor originally identified as a homeotic gene essential for organ development. Early studies suggested that SALL4 is a useful marker to identify testicular and ovarian germ cell tumors. The aim of the study was to evaluate the diagnostic potential of SALL4 immunohistochemistry. Immunohistochemical staining was performed on a tissue microarray (TMA) with 3966 samples from 94 different tumor types and on a further TMA with 492 esophagus carcinomas. SALL4 immunostaining was by far most prevalent and most intensive in testicular tumors with a positivity rate of 93.1% in seminomas, 80% in mixed germ cell tumors (embryonic carcinomas/yolk sac tumors), and 18.5% in teratomas, respectively. However, SALL4 expression is not specific to germ cell tumors. We observed SALL4 positivity in non-germ cell tumors as carcinomas of the kidney (28.9% of chromophobe, 34.4% of clear cell carcinoma), in intestinal type adenocarcinoma of the stomach (10.9%), in adenocarcinoma (10.5%) and squamous cell carcinoma (7.2%) of the esophagus, and in malignant melanoma (8.1%) and invasive urothelial bladder carcinoma (20%). SALL4 expression was not found in lymphomas, in soft tissue tumors or breast tumors. At analysis of esophagus carcinoma TMA, no significant association was seen between SALL4 expression and overall survival in adenocarcinoma. However, SALL4 expression was strongly associated with worse overall survival in squamous cell carcinoma. SALL4 expression can be found at relevant frequencies in various tumors of different primary sites. SALL4 expression in squamous cell carcinoma of the esophagus may constitute a sign of dedifferentiation leading to poor patient prognosis.

Cancer stem cells in hepatocellular carcinoma: Therapeutic implications based on stem cell biology

Hepatocellular carcinoma (HCC) is the sixth most common cancer and the third most frequent cause of cancer-related death worldwide. Despite advances in its diagnosis and treatment, the prognosis of patients with advanced HCC remains unfavorable. Recent advances in stem cell biology and associated technologies have enabled the identification of minor components of tumorigenic cells, termed cancer stem cells (CSC) or tumor-initiating cells, in cancers such as HCC. Furthermore, because CSC play a central role in tumor development, metastasis and recurrence, they are considered to be a therapeutic target in cancer treatment. Hepatic CSC have been successfully identified using functional and cell surface markers. The analysis of purified hepatic CSC has revealed the molecular machinery and signaling pathways involved in their maintenance. In addition, epigenetic transcriptional regulation has been shown to be important in the development and maintenance of CSC. Although inhibitors of CSC show promise as CSC-targeting drugs, novel therapeutic approaches for the eradication of CSC are yet to be established. In this review, we describe recent progress in hepatic CSC research and provide a perspective on the available therapeutic approaches based on stem cell biology.

Immunohistochemical molecular analysis indicates hepatocellular carcinoma subgroups that reflect tumor aggressiveness

Histopathologic parameters and molecular markers are widely accepted as useful predictors of tumor aggressiveness in hepatocellular carcinoma (HCC). However, few studies have analyzed immunohistochemical profiles comprehensively in one series, a fact that has resulted in fragmentation of information that could be applied in clinical practice. We conducted immunohistochemical expression analysis of biliary/stem cell markers (cytokeratin 19, sal-like protein 4, epithelial cell adhesion molecule, and CD133), Wnt/β-catenin signaling-related molecules (β-catenin and glutamine synthetase), p53, and cell proliferation markers (Ki-67 and mitosis) in 162 HCCs surgically resected from 142 patients and analyzed the results with respect to clinicopathological features. Immunohistochemical analysis broadly identified 3 groups: the biliary/stem cell marker-positive group, the Wnt/β-catenin signaling-related marker-positive group, and the biliary/stem cell marker-negative and Wnt/β-catenin signaling-related marker-negative group. p53 was frequently positive in the biliary/stem cell marker-positive group, but it was rarely positive in the Wnt/β-catenin signaling-related marker-positive group. The biliary/stem cell marker-positive group exhibited poor tumor differentiation, increased frequency of portal vein invasion and/or intrahepatic metastasis, and highly proliferative activity. In contrast, the biliary/stem cell marker-negative and Wnt/β-catenin signaling-related marker-negative group exhibited better tumor differentiation, a decreased frequency of portal vein invasion and/or intrahepatic metastasis, and less proliferative activity. The Wnt/β-catenin signaling-related marker-positive group showed neither tendency. The biliary/stem cell marker-positive group had the shortest time to recurrence among the 3 groups. Immunohistochemical profiling of HCC reflects tumor aggressiveness and suggests the potential efficacy of immunohistochemistry-based subclassification of HCC.

Functional and genetic deconstruction of the cellular origin in liver cancer

During the past decade, research on primary liver cancers has particularly highlighted the uncommon plasticity of differentiated parenchymal liver cells (that is, hepatocytes and cholangiocytes (also known as biliary epithelial cells)), the role of liver progenitor cells in malignant transformation, the importance of the tumour microenvironment and the molecular complexity of liver tumours. Whereas other reviews have focused on the landscape of genetic alterations that promote development and progression of primary liver cancers and the role of the tumour microenvironment, the crucial importance of the cellular origin of liver cancer has been much less explored. Therefore, in this Review, we emphasize the importance and complexity of the cellular origin in tumour initiation and progression, and attempt to integrate this aspect with recent discoveries in tumour genomics and the contribution of the disrupted hepatic microenvironment to liver carcinogenesis.

RBMY, a novel inhibitor of glycogen synthase kinase 3β, increases tumor stemness and predicts poor prognosis of hepatocellular carcinoma

Male predominance of hepatocellular carcinoma (HCC) occurs particularly among young children aged 6-9 years, indicative of a possible role of the Y chromosome-encoded oncogene in addition to an androgenic effect. The discovery of oncogenic activation of RBMY (RNA-binding motif on Y chromosome), which is absent in normal hepatocytes but present in male HCC tissues, sheds light on this issue. Herein, we report on a critical hepatocarcinogenic role of RBMY and its ontogenic origin. During liver development, the Ser/Thr phosphorylated RBMY is expressed in the cytoplasm of human and rodent fetal livers. It is then silenced in mature hepatocytes and restricted to scarce expression in the bile ductular cells. Upon hepatocarcinogenesis, a noteworthy increase of cytoplasmic and nuclear RBMY is observed in HCC tissues; however, only the former is expressed dominantly in hepatic cancer stem cells and correlates significantly to a poor prognosis and decreased survival rate in HCC patients. Cytoplasmic expression of RBMY, which is mediated by binding to nuclear exporter chromosome region maintenance 1 and further enriched upon Wnt-3a stimulation, confers upon tumor cells the traits of cancer stem cell by augmenting self-renewal, chemoresistance, cell-cycle progression, proliferation, and xenograft tumor growth. This is achieved mechanistically through increasing Ser9 phosphorylation-inactivation of glycogen synthase kinase 3β by RBMY, thereby impeding the glycogen synthase kinase 3β-dependent degradation of β-catenin and eventually inducing the nuclear entry of β-catenin for the transcription of downstream oncogenes.

CONCLUSION

RBMY is a novel oncofetal protein that plays a key role in attenuating glycogen synthase kinase 3β activity, leading to aberrant activation of Wnt/β-catenin signaling, which facilitates malignant hepatic stemness; because of its absence from normal human tissues except the testis, RBMY represents a feasible therapeutic target for the selective eradication of HCC cells in male patients.

Spalt-like transcription factor 4 immunopositivity is associated with epithelial cell adhesion molecule expression in combined hepatocellular carcinoma and cholangiocarcinoma

AIM

Combined hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) (cHCC-CC) is a rare biphasic liver cancer. Recent studies have demonstrated that cHCC-CC originates from hepatic progenitor cells (HPCs). Spalt-like transcription factor 4 (SALL4) is a marker for a progenitor subclass of HCC with an aggressive phenotype. However, little has been revealed about SALL4 expression in cHCC-CC. The aims of this study were to report SALL4 immunopositivity and the results of clinicopathological analysis in cHCC-CC, and to examine the two different nuclear immunostaining patterns for SALL4.

METHODS AND RESULTS

We defined the diffuse finely granular nuclear immunostaining pattern as immunopositive for SALL4; this was observed in eight (8.9%) of 90 cHCC-CCs. SALL4 immunopositivity was significantly associated with immunopositivity for α-fetoprotein, glypican 3, and epithelial cell adhesion molecule (EpCAM). There was no relationship between SALL4 immunopositivity and prognosis. We confirmed SALL4 mRNA expression in samples with a punctuate/clumped immunostaining pattern, which showed a significantly lower rate of immunopositivity for EpCAM than those with a diffuse finely granular pattern.

CONCLUSIONS

SALL4 immunopositivity is not a prognostic factor in cHCC-CC; however, it is associated with α-fetoprotein, glypican 3 and EpCAM immunopositivity, indicating the mechanism of carcinogenesis. Further study is necessary to interpret the immunostaining pattern for SALL4.

SALL4 as an Epithelial-Mesenchymal Transition and Drug Resistance Inducer through the Regulation of c-Myc in Endometrial Cancer

SALL4 plays important roles in the development and progression of many cancers. However, the role and molecular mechanism of SALL4 in endometrial cancer remain elusive. In the present research, we have demonstrated that the expression of SALL4 was upregulated in endometrial cancer and correlated positively with tumor stage, metastases and poor survival of patients. The overexpression of SALL4 promoted the invasiveness in endometrial cancer cells, as indicated by the upregulation of mesenchymal cell marker N-cadherin and downregulation of the epithelial marker E-cadherin, and invasion assays in vitro. Additionally, there was also an increase in drug resistance in these cell models due to the upregulation of ATP-binding cassette multidrug transporter ABCB1 expression. Moreover, we also found that ABCB1 was critical for SALL4-induced drug resistance. In contrast, SALL4 knockdown restored drug sensitivity, reversed EMT, diminished cell metastasis and suppressed the downregulation of E-cadherin and the upregulation of N-cadherin and ABCB1. Furthermore, we showed that SALL4 upregulated c-Myc expression and c-Myc was a direct target for SALL4 by ChIP assay, depletion of c-Myc with siRNA abolished the SALL4-induced downregulation of E-cadherin, upregulation of N-cadherin and ABCB1, suggesting that c-Myc was a downstream target for SALL4 and required for SALL4-induced EMT, invasion and drugs resistance in endometrial cancer cells. These results indicated that SALL4 could induce EMT and resistance to antineoplastic drugs through the regulation of c-Myc. SALL4 and c-Myc may be novel therapeutic targets for endometrial cancer.

Tumour antigen expression in hepatocellular carcinoma in a low-endemic western area

Background:

Identification of tumour antigens is crucial for the development of vaccination strategies against hepatocellular carcinoma (HCC). Most studies come from eastern-Asia, where hepatitis-B is the main cause of HCC. However, tumour antigen expression is poorly studied in low-endemic, western areas where the aetiology of HCC differs.

Methods:

We constructed tissue microarrays from resected HCC tissue of 133 patients. Expression of a comprehensive panel of cancer-testis (MAGE-A1, MAGE-A3/4, MAGE-A10, MAGE-C1, MAGE-C2, NY-ESO-1, SSX-2, sperm protein 17), onco-fetal (AFP, Glypican-3) and overexpressed tumour antigens (Annexin-A2, Wilms tumor-1, Survivin, Midkine, MUC-1) was determined by immunohistochemistry.

Results:

A higher prevalence of MAGE antigens was observed in patients with hepatitis-B. Patients with expression of more tumour antigens in general had better HCC-specific survival (P=0.022). The four tumour antigens with high expression in HCC and no, or weak, expression in surrounding tumour-free-liver tissue, were Annexin-A2, GPC-3, MAGE-C1 and MAGE-C2, expressed in 90, 39, 17 and 20% of HCCs, respectively. Ninety-five percent of HCCs expressed at least one of these four tumour antigens. Interestingly, GPC-3 was associated with SALL-4 expression (P=0.001), an oncofetal transcription factor highly expressed in embryonal stem cells. SALL-4 and GPC-3 expression levels were correlated with vascular invasion, poor differentiation and higher AFP levels before surgery. Moreover, patients who co-expressed higher levels of both GPC-3 and SALL-4 had worse HCC-specific survival (P=0.018).

Conclusions:

We describe a panel of four tumour antigens with excellent coverage and good tumour specificity in a western area, low-endemic for hepatitis-B. The association between GPC-3 and SALL-4 is a novel finding and suggests that GPC-3 targeting may specifically attack the tumour stem-cell compartment.

Keratin 19 protein expression is an independent predictor of survival in human hepatocellular carcinoma

AIM

We aimed to assess the clinicopathological relevance and prognostic significance of expression of the hepatic progenitor cell markers keratin 19 (K19), epithelial cell adhesion molecule (EpCAM) and CD117 (c-KIT) in a White series of hepatocellular carcinoma (HCC).

METHODS

We evaluated the immunohistochemical expression of K19, EpCAM and CD117 in 89 surgical specimens of HCC from Greek patients (mean age 66.7±11.3 years, male 75.2%) followed up for 39.6±25.3 months.

RESULTS

K19, EpCAM and CD117 expression was detected in tumour cells of 10.11, 15.38 and 3.7% HCCs, respectively. Female sex was correlated with EpCAM immunohistochemical expression (P=0.035), whereas no other significant relationship with clinicopathological parameters was observed. K19 positivity tended to be correlated with microvascular invasion (P=0.054). In univariate analysis, K19 positivity and microvascular invasion were found to be associated with decreased recurrence-free survival (P<0.001 and P=0.004, respectively) and overall survival (P=0.002 and P=0.029, respectively). EpCAM and CD117 positivity was not correlated with patient survival. In multivariate analysis, K19 positivity emerged as an independent predictor of recurrence-free survival (odds ratio=7.84, 95% confidence interval=2.658-22.912, P<0.001) and overall survival (odds ratio=3.845, 95% confidence interval=1.401-10.549, P=0.009).

CONCLUSION

Our study confirms the prognostic significance of K19 expression in Caucasian patients with HCCs, providing further evidence that it may be used to stratify HCC according to tumour aggressiveness.

SALL4 Expression in Hepatocellular Carcinomas Is Associated with EpCAM-Positivity and a Poor Prognosis

Background:

There is increasing interest in hepatocellular carcinomas (HCC) expressing “stemness”-related markers, as they have been associated with aggressive behavior and poor prognosis. In this study, we investigated the usefulness of Sal-like protein 4 (SALL4), a recently proposed candidate marker of “stemness.”

Methods:

Immunohistochemical stains were performed for SALL4, K19, and epithelial cellular adhesion molecule (EpCAM) on tissue microarrays constructed from 190 surgically resected HCCs, and the results were correlated with the clinicopathological features and patient survival data.

Results:

Nuclear SALL4 expression was observed in 39/190 HCCs (20.5%), while K19 and EpCAM were expressed in 30 (15.9%) and 92 (48.7%) HCCs, respectively. The nuclear expression was generally weak, punctate or clumped. SALL4 expression was significantly associated with a poor overall survival compared to SALL4-negative HCCs (p = .014) compared to SALL4-negative HCCs. On multivariate analysis adjusted for tumor size, multiplicity, vascular invasion, and pathological tumor stage, SALL4 remained as a significant independent predictor of decreased overall survival (p= .004). SALL4 expression was positively correlated with EpCAM expression (p = .013) but not with K19 expression. HCCs that expressed both SALL4 and EpCAM were associated with significantly decreased overall survival, compared to those cases which were negative for both of these markers (p = .031).

Conclusions:

Although SALL4 expression was not significantly correlated with other clinicopathological parameters suggestive of tumor aggressiveness, SALL4 expression was an independent predictor of poor overall survival in human HCCs, and was also positively correlated with EpCAM expression.

Biological features and biomarkers in hepatocellular carcinoma

Similar to other cancers, a multistep process of carcinogenesis is observed in hepatocellular carcinoma (HCC). Although the mechanisms underlying the development of HCC have been investigated in terms of oncology, virology, and stem cell biology, the whole picture of hepatocarcinogenesis remains to be elucidated. Recent progress in molecular biology has provided clues to the underlying cause of various diseases. In particular, sequencing technologies, such as whole genome and exome sequencing analyses, have made an impact on genomic research on a variety of cancers including HCC. Comprehensive genomic analyses have detected numerous abnormal genetic alterations, such as mutations and copy number alterations. Based on these findings, signaling pathways and cancer-related genes involved in hepatocarcinogenesis could be analyzed in detail. Simultaneously, a number of novel biomarkers, both from tissue and blood samples, have been recently reported. These biomarkers have been successfully applied to early diagnosis and prognostic prediction of patients with HCC. In this review, we focus on the recent developments in molecular cancer research on HCC and explain the biological features and novel biomarkers.