Qing-Hai Ye

EpCAM-positive hepatocellular carcinoma cells are tumor initiating cells with stem/progenitor cell features

BACKGROUND & AIMS Cancer progression/metastases and embryonic development share many properties including cellular plasticity, dynamic cell motility, and integral interaction with the microenvironment. We hypothesized that the heterogeneous nature of hepatocellular carcinoma (HCC), in part, may be owing to the presence of hepatic cancer cells with stem/progenitor features. METHODS Gene expression profiling and immunohistochemistry analyses were used to analyze 235 tumor specimens derived from 2 recently identified HCC subtypes (EpCAM(+) alpha-fetoprotein [AFP(+)] HCC and EpCAM(-) AFP(-) HCC). These subtypes differed in their expression of AFP, a molecule produced in the developing embryo, and EpCAM, a cell surface hepatic stem cell marker. Fluorescence-activated cell sorting was used to isolate EpCAM(+) HCC cells, which were tested for hepatic stem/progenitor cell properties. RESULTS Gene expression and pathway analyses revealed that the EpCAM(+) AFP(+) HCC subtype had features of hepatic stem/progenitor cells. Indeed, the fluorescence-activated cell sorting-isolated EpCAM(+) HCC cells displayed hepatic cancer stem cell-like traits including the abilities to self-renew and differentiate. Moreover, these cells were capable of initiating highly invasive HCC in nonobese diabetic, severe combined immunodeficient mice. Activation of Wnt/beta-catenin signaling enriched the EpCAM(+) cell population, whereas RNA interference-based blockage of EpCAM, a Wnt/beta-catenin signaling target, attenuated the activities of these cells. CONCLUSIONS Taken together, our results suggest that HCC growth and invasiveness is dictated by a subset of EpCAM(+) cells, opening a new avenue for HCC cancer cell eradication by targeting Wnt/beta-catenin signaling components such as EpCAM.

Identification of metastasis‐related microRNAs in hepatocellular carcinoma

MicroRNAs (miRNAs) have been used as cancer‐related biomarkers. Hepatocellular carcinoma (HCC) is an aggressive cancer with a dismal outcome largely due to metastasis and postsurgical recurrence. We investigated whether the expression of certain miRNAs are associated with HCC metastasis. We examined the miRNA expression profiles of 482 cancerous and noncancerous specimens from radical resection of 241 patients with HCC. Using a supervised algorithm and a clinically well‐defined cohort of 131 cases, we built a unique 20‐miRNA metastasis signature that could significantly predict (P < 0.001) primary HCC tissues with venous metastases from metastasis‐free solitary tumors with 10‐fold cross‐validation. However, significant miRNAs could not be identified from the corresponding noncancerous hepatic tissues. A survival risk prediction analysis revealed that a majority of the metastasis‐related miRNAs were associated with survival. Furthermore, the 20‐miRNA tumor signature was validated in 110 additional cases as a significant independent predictor of survival (P = 0.009) and was significantly associated with both survival and relapse in 89 cases of early stage HCC (P = 0.022 and 0.002, respectively). These 20 miRNAs may provide a simple profiling method to assist in identifying patients with HCC who are likely to develop metastases/recurrence. In addition, functional analysis of these miRNAs may enhance our biological understanding of HCC metastasis. (HEPATOLOGY 2008.)

EpCAM and α-Fetoprotein Expression Defines Novel Prognostic Subtypes of Hepatocellular Carcinoma

The heterogeneous nature of hepatocellular carcinoma (HCC) and the lack of appropriate biomarkers have hampered patient prognosis and treatment stratification. Recently, we have identified that a hepatic stem cell marker, epithelial cell adhesion molecule (EpCAM), may serve as an early biomarker of HCC because its expression is highly elevated in premalignant hepatic tissues and in a subset of HCC. In this study, we aimed to identify novel HCC subtypes that resemble certain stages of liver lineages by searching for EpCAM-coexpressed genes. A unique signature of EpCAM-positive HCCs was identified by cDNA microarray analysis of 40 HCC cases and validated by oligonucleotide microarray analysis of 238 independent HCC cases, which was further confirmed by immunohistochemical analysis of an additional 101 HCC cases. EpCAM-positive HCC displayed a distinct molecular signature with features of hepatic progenitor cells including the presence of known stem/progenitor markers such as cytokeratin 19, c-Kit, EpCAM, and activated Wnt-beta-catenin signaling, whereas EpCAM-negative HCC displayed genes with features of mature hepatocytes. Moreover, EpCAM-positive and EpCAM-negative HCC could be further subclassified into four groups with prognostic implication by determining the level of alpha-fetoprotein (AFP). These four subtypes displayed distinct gene expression patterns with features resembling certain stages of hepatic lineages. Taken together, we proposed an easy classification system defined by EpCAM and AFP to reveal HCC subtypes similar to hepatic cell maturation lineages, which may enable prognostic stratification and assessment of HCC patients with adjuvant therapy and provide new insights into the potential cellular origin of HCC and its activated molecular pathways.

MicroRNA-26a suppresses tumor growth and metastasis of human hepatocellular carcinoma by targeting interleukin-6-Stat3 pathway†‡

Down‐regulation of microRNA‐26a (miR‐26a) is associated with poor prognosis of hepatocellular carcinoma (HCC), but its functional mechanism in HCC remains unclear. In this study, we investigated the roles of miR‐26a in tumor growth and metastasis of HCC and found that miR‐26a was frequently down‐regulated in HCC tissues. Down‐regulation of miR‐26a correlated with HCC recurrence and metastasis. Through gain‐ and loss‐of‐function studies, miR‐26a was demonstrated to significantly inhibit in vitro cell proliferation, migration, and invasion. In addition, miR‐26a induced G1 arrest and promoted apoptosis of HCC cells. Importantly, miR‐26a suppressed in vivo tumor growth and metastasis in nude mice models bearing human HCC. Interleukin‐6 (IL‐6) was identified as a target of miR‐26a. Knockdown of IL‐6 induced effects on HCC cells similar to those induced by miR‐26a. In contrast, IL‐6 treatment abrogated the effects induced by miR‐26a up‐regulation. Moreover, miR‐26a dramatically suppressed expression of signal transducer and activator of transcription 3 (Stat3) target genes, including Bcl‐2, Mcl‐1, cyclin D1, and MMP2. IL‐6 treatment antagonized this effect, while knockdown of IL‐6 by IL‐6 short hairpin RNA (shIL‐6) induced inhibitory effects on the expression of p‐Stat3 and its main target genes, similar to miR‐26a. The messenger RNA and protein levels of IL‐6 inversely correlated with miR‐26a in HCCs. Patients with high miR‐26a or low IL‐6 in HCC tissues had a better prognosis with longer overall survival (OS) and time to recurrence (TTR). In multivariate analysis, miR‐26a, IL‐6, and their combination were demonstrated to be independent prognostic indicators for OS and TTR of HCC patients. Conclusion: miR‐26a could suppress tumor growth and metastasis of HCC through IL‐6‐Stat3 signaling and is a novel prognostic marker and therapeutic target for HCC. (HEPATOLOGY 2013)

Gene Expression Profiling Reveals Potential Biomarkers of Human Hepatocellular Carcinoma

Purpose: Hepatocellular carcinoma (HCC), a common cancer worldwide, has a dismal outcome partly due to the poor identification of early-stage HCC. Currently, one third of HCC patients present with low serum α-fetoprotein (AFP) levels, the only clinically available diagnostic marker for HCC. The aim of this study was to identify new diagnostic molecular markers for HCC, especially for individuals with low serum AFP. Experimental Design: We used the microarray technique to determine the expression profiles of 218 HCC specimens from patients with either high or low serum AFP. From the microarray study, we selected five candidate genes (i.e., GPC3, PEG10, MDK, SERPINI1, and QP-C), which were overexpressed in HCCs. Using quantitative real-time PCR analyses, we validated the expression of these five genes in 50 AFP-normal and 8 AFP-positive HCC specimens and 36 cirrhotic noncancerous hepatic specimens, which include 52 independent specimens not used in microarray analysis. Results: A significant increase in the expression of the five candidate genes could be detected in most of the HCC samples, including those with normal serum AFP and small tumors. GPC3, MDK, and SERPINI1 encode known serum proteins. Consistently, a significant increase in serum midkine, encoded by MDK, was associated with HCC patients, including those with normal serum AFP. Using prediction analysis of microarray, we showed that a combined score of these five genes can accurately classify noncancerous hepatic tissues (100%) and HCC (71%). Conclusions: We suggest that a diagnostic signature approach using a combined score of these five biomarkers rather than a single marker may improve the prediction accuracy of HCC patients, including those with normal serum AFP and smaller-sized tumors.

Let-7g targets collagen type I α2 and inhibits cell migration in hepatocellular carcinoma

BACKGROUND & AIMS Hepatocellular carcinoma (HCC) is an aggressive cancer with a poor prognosis mainly due to metastasis. MicroRNAs are endogenous small noncoding RNAs that regulate cellular gene expression and are functionally linked to tumourigenesis. Using microarray analysis, we recently identified 20 miRNAs associated with HCC metastasis. Here, we carried out further analyses on one of these microRNAs, let-7g, to determine whether it is functionally linked to HCC metastasis. METHODS Quantitative real-time polymerase chain reaction was used to determine the level of mature let-7g transcript in HCC clinical specimens and its correlation with patient survival. Ectopic expression of let-7g was carried out in HCC cell lines to assess its influence on cell growth, migration, and invasion. RESULTS We confirmed that the level of let-7g was significantly lower in metastatic HCCs compared to metastasis-free HCCs. Moreover, low let-7g expression in a tumour was predictive of poor survival in HCC patients. Functional studies indicated that ectopic expression of let-7g significantly inhibits HCC cell migration and cell growth. In-silico analysis revealed members of soluble collagens as potential targets of let-7g. Consistently, the levels of type I collagen alpha2 (COL1A2) and let-7g were inversely correlated in HCC clinical specimens. COL1A2 was experimentally validated as a direct target of let-7g. Moreover, addition of COL1A2 counteracted the inhibitory effect of let-7g on cell migration. CONCLUSIONS These results suggest that let-7g may suppress HCC metastasis partially through targeting COL1A2.

Transcriptomic profiling reveals hepatic stem‐like gene signatures and interplay of miR‐200c and epithelial‐mesenchymal transition in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocellular carcinoma (ICC) is the second most common type of primary liver cancer. However, its tumor heterogeneity and molecular characteristics are largely unknown. In this study, we conducted transcriptomic profiling of 23 ICC and combined hepatocellular cholangiocarcinoma tumor specimens from Asian patients using Affymetrix messenger RNA (mRNA) and NanoString microRNA microarrays to search for unique gene signatures linked to tumor subtypes and patient prognosis. We validated the signatures in an additional 68 ICC cases derived from Caucasian patients. We found that both mRNA and microRNA expression profiles could independently classify Asian ICC cases into two main subgroups, one of which shared gene expression signatures with previously identified hepatocellular carcinoma (HCC) with stem cell gene expression traits. ICC‐specific gene signatures could predict survival in Asian HCC cases and independently in Caucasian ICC cases. Integrative analyses of the ICC‐specific mRNA and microRNA expression profiles revealed that a common signaling pathway linking miR‐200c signaling to epithelial‐mesenchymal transition (EMT) was preferentially activated in ICC with stem cell gene expression traits. Inactivation of miR‐200c resulted in an induction of EMT, whereas activation of miR‐200c led to a reduction of EMT including a reduced cell migration and invasion in ICC cells. We also found that miR‐200c and neural cell adhesion molecule 1 (NCAM1) expression were negatively correlated and their expression levels were predictive of survival in ICC samples. NCAM1, a known hepatic stem/progenitor cell marker, was experimentally demonstrated to be a direct target of miR‐200c. Conclusion: Our results indicate that ICC and HCC share common stem‐like molecular characteristics and poor prognosis. We suggest that the specific components of EMT may be exploited as critical biomarkers and clinically relevant therapeutic targets for an aggressive form of stem cell‐like ICC. (HEPATOLOGY 2012;56:1792–1803)

Lentiviral‐mediated miRNA against osteopontin suppresses tumor growth and metastasis of human hepatocellular carcinoma

In our previous study, osteopontin (OPN) was identified as one of the leading genes that promote the metastasis of hepatocellular carcinoma (HCC). However, the mechanism by which OPN promotes metastasis of HCC is not understood. In this study, RNA interference mediated by viral vectors—which could induce a long‐lasting down‐regulation in gene expression—was applied to analyze the role of OPN in metastasis of HCC. Three lentiviral vectors encoding microRNA against OPN, Lenti.OPNi‐1, Lenti.OPNi‐2, and Lenti.OPNi‐3, were constructed and found to down‐regulate the OPN level by 62%, 78%, and 95%, respectively, in HCCLM3 cells which had an overexpression of OPN and a higher metastatic potential. Consequently, both Lenti.OPNi‐2 and Lenti.OPNi‐3 induced a significant decrease in matrix metalloproteinase (MMP)‐2 and urokinase plasminogen activator expression, and led to an obvious inhibition of both in vitro invasion and in vivo lung metastasis of HCCLM3 cells (P < 0.001). Moreover, Lenti.OPNi‐3, rather than Lenti.OPNi‐2, could also suppress in vitro proliferation and in vivo tumor growth of HCCLM3. Smaller detectable tumors were found in only 50% of mice after implantation of Lenti.OPNi‐3–transfected HCCLM3 cells (341 ± 502.6 mm3 versus >3500 mm3 in controls; P < 0.001). Lenti.OPNi‐3, not Lenti.OPNi‐2, significantly suppressed the MEK/ERK1/2 pathway in HCCLM3 cells. Recombinant OPN was found to induce translocation of p65 into the nucleus of HCC cells and activation of MMP‐2 and MEK/ERK/1/2, which were suppressed by the nuclear factor κB (NF‐κB) inhibitor pyrrolidine dithiocarbamate. Conclusion: OPN plays an important role in metastasis as well as tumor growth of HCC, in which different minimum threshold levels of OPN are needed. These effects may occur through activation of the mitogen‐activated protein kinase and NF‐κB pathways, and MMP‐2. OPN could be a hopeful target for the control of HCC. (HEPATOLOGY 2008;48:1834‐11842.)

Cancer-Associated Molecular Signature in the Tissue Samples of Patients with Cirrhosis

Several types of aggressive cancers, including hepatocellular carcinoma (HCC), often arise as a multifocal primary tumor. This suggests a high rate of premalignant changes in noncancerous tissue before the formation of a solitary tumor. Examination of the messenger RNA expression profiles of tissue samples derived from patients with cirrhosis of various etiologies by complementary DNA (cDNA) microarray indicated that they can be grossly separated into two main groups. One group included hepatitis B and C virus infections, hemochromatosis, and Wilsons disease. The other group contained mainly alcoholic liver disease, autoimmune hepatitis, and primary biliary cirrhosis. Analysis of these two groups by the cross‐validated leave‐one‐out machine‐learning algorithms revealed a molecular signature containing 556 discriminative genes (P < .001). It is noteworthy that 273 genes in this signature (49%) were also significantly altered in HCC (P < .001). Many genes were previously known to be related to HCC. The 273‐gene signature was validated as cancer‐associated genes by matching this set to additional independent tumor tissue samples from 163 patients with HCC, 56 patients with lung carcinoma, and 38 patients with breast carcinoma. From this signature, 30 genes were altered most significantly in tissue samples from high‐risk individuals with cirrhosis and from patients with HCC. Among them, 12 genes encoded secretory proteins found in sera. In conclusion, we identified a unique gene signature in the tissue samples of patients with cirrhosis, which may be used as candidate markers for diagnosing the early onset of HCC in high‐risk populations and may guide new strategies for chemoprevention. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270‐9139/suppmat/index.html). (HEPATOLOGY 2004;39:518–527.)

Human mesenchymal stem cells inhibit metastasis of a hepatocellular carcinoma model using the MHCC97-H cell line

The effects of mesenchymal stem cells (MSC) on the growth and metastasis of human malignancies including hepatocellular carcinoma (HCC) are controversial, and the underlying mechanisms are not yet understood. The aim of this study was to explore the role of MSC in the progression of HCC. We investigated the effect of MSC on in vitro proliferation and invasion and in vivo tumor growth and pulmonary metastasis of MHCC97‐H HCC cells with a high metastatic potential. The mRNA and protein levels of transforming growth factor‐beta 1 (TGFβ1) and MMP, and their association with the effects of MSC on HCC cells were also evaluated. Co‐culture of MHCC97‐H cells with MSC conditioned medium significantly enhanced in vitro proliferation but inhibited invasiveness. Following MSC treatment of a nude mouse model bearing human HCC, the MSC were predominantly located in the HCC tissues. Compared with controls, MSC‐treated mice exhibited significantly larger tumors (3080.51 ± 1234.78 mm3vs 2223.75 ± 1000.60 mm3, P = 0.045), but decreased cellular numbers of lung metastases (49.75 ± 18.86 vs 227.22 ± 74.67, P = 0.046). Expression of TGFβ1 and MMP‐2 was significantly downregulated in the MSC‐treated HCC cells. TGFβ siRNA concurrently downregulated expression of TGFβ and MMP‐2 in HCC cells and blocked the MSC‐induced proliferation and invasiveness of MHCC97‐H cells. The MSC enhanced tumor growth but significantly inhibited the invasiveness and metastasis of HCC, possibly through downregulation of TGFβ1. These findings suggest that MSC could be useful in controlling metastatic recurrence of HCC. (Cancer Sci 2010; 101: 2546–2553)