High expression of cancer stem cell markers in cholangiolocellular carcinoma. Surg Today. 2013;43:654-660. [PMID: 23192764 PMCID: PMC3651534 DOI: 10.1007/s00595-012-0437-9]

Long Non-Coding RNAs in Biliary Tract Cancer-An Up-to-Date Review

The term long non-coding RNA (lncRNA) describes non protein-coding transcripts with a length greater than 200 base pairs. The ongoing discovery, characterization and functional categorization of lncRNAs has led to a better understanding of the involvement of lncRNAs in diverse biological and pathological processes including cancer. Aberrant expression of specific lncRNA species was demonstrated in various cancer types and associated with unfavorable clinical characteristics. Recent studies suggest that lncRNAs are also involved in the development and progression of biliary tract cancer, a rare disease with high mortality and limited therapeutic options. In this review, we summarize current findings regarding the manifold roles of lncRNAs in biliary tract cancer and give an overview of the clinical and molecular consequences of aberrant lncRNA expression as well as of underlying regulatory functions of selected lncRNA species in the context of biliary tract cancer.

Immunohistochemical and molecular features of cholangiolocellular carcinoma are similar to well-differentiated intrahepatic cholangiocarcinoma

Cholangiolocellular carcinoma is characterized by low grade cytologic atypia, and anastomosing cords and glands resembling cholangioles or canals of Hering. Cholangiolocellular carcinoma has been variously regarded as a subtype of intrahepatic cholangiocarcinoma (World Health Organization 2000), combined hepatocellular-cholangiocarcinoma of stem cell subtype (World Health Organization 2010) and a distinct type of primary liver carcinoma. Capture-based next generation sequencing targeting the coding regions of 479 cancer genes and select introns was performed on 17 cases (5 cholangiolocellular carcinomas, 7 intrahepatic cholangiocarcinomas, 5 mixed cholangiolocellular-intrahepatic cholangiocarcinomas) along with immunohistochemistry for CK19, SALL4, CD56, CD117, and EMA. For 5 mixed cholangiolocellular-intrahepatic cholangiocarcinoma, the individual areas were micro-dissected prior to sequencing. CK19 and EMA were positive in all cases; both luminal and cytoplasmic EMA was seen in 3/5 cholangiolocellular carcinoma and 3/6 intrahepatic cholangiocarcinomas. CD117 and SALL4 were negative in all cases. CD56 was positive in 2/5 cholangiolocellular carcinoma, 4/6 intrahepatic cholangiocarcinoma and 2/5 mixed cases. Mutations typical of intrahepatic cholangiocarcinoma (IDH1/2, PBRM1, FGFR2) were present in 90% of cases with cholangiolocellular carcinoma component. The genomic profile (IDH1/2 mutations, FGFR2 fusions, chromatin-remodeling gene mutations such as ARID1A, PBRM1) and copy number alterations were similar in cholangiolocellular carcinoma, intrahepatic cholangiocarcinoma and mixed cholangiolocellular-intrahepatic cholangiocarcinoma. In all mixed cases, the immunohistochemistry results, mutational profile and copy number alterations in both components were similar. Cholangiolocellular carcinoma should be categorized as a histologic subtype of well-differentiated intrahepatic cholangiocarcinoma, and should not be considered a distinct entity, or combined hepatocellular-cholangiocarcinoma unless a distinct hepatocellular component is also present.

Role of Cancer Stem Cells in Cholangiocarcinoma and Therapeutic Implications

Cholangiocarcinoma (CCA) is the second most common type of liver cancer, and is highly aggressive with very poor prognosis. CCA is classified into intrahepatic cholangiocarcinoma (iCCA) and extra-hepatic cholangiocarcinoma (eCCA), which is further stratified into perihilar (pCCA) and distal (dCCA). Cancer stem cells (CSCs) are a subpopulation of cancer cells capable of tumor initiation and malignant growth, and are also responsible for chemoresistance. Thus, CSCs play an important role in CCA carcinogenesis. Surface markers such as CD133, CD24, CD44, EpCAM, Sox2, CD49f, and CD117 are important for identifying and isolating CCA CSCs. CSCs are present in the tumor microenvironment (TME), termed ‘CSC niche’, where cellular components and soluble factors interact to promote tumor initiation. Epithelial-to-mesenchymal transition (EMT) is another important mechanism underlying carcinogenesis, involved in the invasiveness, metastasis and chemoresistance of cancer. It has been demonstrated that EMT plays a critical role in generating CSCs. Therapies targeting the surface markers and signaling pathways of CCA CSCs, proteins involved in TME, and immune checkpoint proteins are currently under investigation. Therefore, this review focuses on recent studies on the roles of CSCs in CCA; the possible therapeutic strategies targeting CSCs of CCA are also discussed.

Whole-exome sequencing reveals the origin and evolution of hepato-cholangiocarcinoma

Hepatocellular-cholangiocarcinoma (H-ChC) is a rare subtype of liver cancer with clinicopathological features of both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). To date, molecular mechanisms underlying the co-existence of HCC and iCCA components in a single tumor remain elusive. Here, we show that H-ChC samples contain substantial private mutations from WES analyses, ranging from 33.1 to 86.4%, indicative of substantive intratumor heterogeneity (ITH). However, on the other hand, numerous ubiquitous mutations shared by HCC and iCCA suggest the monoclonal origin of H-ChC. Mutated genes identified herein, e.g., VCAN, ACVR2A, and FCGBP, are speculated to contribute to distinct differentiation of HCC and iCCA within H-ChC. Moreover, immunohistochemistry demonstrates that EpCAM is highly expressed in 80% of H-ChC, implying the stemness of such liver cancer. In summary, our data highlight the monoclonal origin and stemness of H-ChC, as well as substantial intratumoral heterogeneity.

Hepatocellular-cholangiocarcinoma (H-ChC) is a rare subtype of liver cancer with features of hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Here, the authors utilize whole exome sequencing to highlight the monoclonal origin and stemness of H-ChC, as well as substantial intratumoral heterogeneity.

Small cholangiolocellular carcinoma that was difficult to distinguish from cholangiocellular carcinoma: a case report

BACKGROUND

Cholangiolocellular carcinoma (CoCC) is thought to be derived from hepatic progenitor cells. Because of its origin, CoCC has diverse clinicopathological and imaging findings. Here, we report a case of small CoCC that was difficult to diagnose preoperatively.

CASE PRESENTATION

A 62-year-old woman was confirmed with a small liver nodule in the left lobe 2 years after a sustained virological response of hepatitis C virus. The size of the nodule was 11.9 × 6.1 mm, and 6 months later, the size increased to 12.5 × 7.8 mm. The doubling time of this tumor was 285 days. The tumor revealed peripheral early enhancement and delayed internal staining in dynamic computed tomography images and marked high intensity in diffusion-weighted magnetic resonance imaging scans. These imaging findings resembled those of cholangiocellular carcinoma (CCC). The tumor was removed by laparoscopic lateral sectionectomy. Pathological findings revealed that the tumor was composed of small cuboidal cells and showed irregular anastomosis small grand. Immunohistochemical findings showed that the tumor cells were negative for Hep-par 1 and positive for cytokeratin 19. Epithelial membrane antigen staining was positive for the membranous side of the lumen. According to these pathological findings, the tumor was diagnosed as CoCC.

CONCLUSION

Although some characteristic imaging findings are reported for CoCC, they are not specific because of the variety in pathological findings. Especially, small CoCCs might have poor characteristic imaging findings and may be difficult to distinguish from CCC in the images. However, slow tumor growth might be one of the characteristics to suspect the possibility of a CoCC.

Biliary tract cancer stem cells - translational options and challenges

Management of biliary tract cancer remains challenging. Tumors show high recurrence rates and therapeutic resistance, leading to dismal prognosis and short survival. The cancer stem cell model states that a tumor is a heterogeneous conglomerate of cells, in which a certain subpopulation of cells - the cancer stem cells - possesses stem cell properties. Cancer stem cells have high clinical relevance due to their potential contributions to development, progression and aggressiveness as well as recurrence and metastasis of malignant tumors. Consequently, reliable identification of as well as pharmacological intervention with cancer stem cells is an intensively investigated and promising research field. The involvement of cancer stem cells in biliary tract cancer is likely as a number of studies demonstrated their existence and the obvious clinical relevance of several established cancer stem cell markers in biliary tract cancer models and tissues. In the present article, we review and discuss the currently available literature addressing the role of putative cancer stem cells in biliary tract cancer as well as the connection between known contributors of biliary tract tumorigenesis such as oncogenic signaling pathways, micro-RNAs and the tumor microenvironment with cancer stem cells.

Giant Cholangiolocellular Carcinoma With Early Recurrence That Was Difficult to Distinguish From Cholangiocellular Carcinoma: Report of a Case

Cholangiolocellular carcinoma (CoCC) is a rare type of malignant liver tumor derived from hepatic stem cells, which exist in the canals of Hering. However, the characteristics of CoCC have not been clarified. In general, CoCC is associated with a better prognosis than cholangiocellular carcinoma (CCC). Here, we report a case of giant CoCC, which was difficult to distinguish from CCC and showed early recurrence and necrosis inside the tumor. A 59-year-old man was diagnosed with CCC based on preoperative imaging. The diameter of the tumor was approximately 14 cm, and he subsequently underwent extended right lobectomy of the liver. Histopathologic analysis revealed that tumor cells proliferated and replaced the surrounding normal liver cell cords in front of the tumor. Furthermore, the tumor cells were positive for cytokeratin 19 and epithelial membrane antigen. Epithelial membrane antigen staining pattern was positive on the membranous area of the lumen. Therefore, the tumor was diagnosed as CoCC. Although adjuvant chemotherapy was performed, intrahepatic recurrence occurred at 4 months after surgery. We present here the novel characteristics of CoCC that show early recurrence and necrosis within the tumor. These characteristics have not previously been reported in patients with CoCC.

Claudins-4 and -7 might be valuable markers to distinguish hepatocellular carcinoma from cholangiocarcinoma

The claudin family members are the functional components of tight junctions. Expression and localization of claudins vary among organs and tumor types. In this study, we examined expression and localization of tight junction proteins (TJP) in human liver tumors, to estimate their usefulness as differential diagnostic markers. The materials used for immunohistochemical analysis were 47 liver tumor specimens including 29 cases of hepatocellular carcinoma (HCC), 15 cases of cholangiocarcinoma (CC), 3 cases of combined HCC and CC (CHC), and 3 cases of cholangiolocellular carcinoma (CoCC). Samples were examined using semiquantitative and statistical analysis of immunoreactivity. In HCC, claudin-1, occludin, tricellulin, and JAM-A were expressed on the cell membrane as well as in hepatocytes. In CC, claudins-1, -4, and -7, tricellulin, and JAM-A were expressed on the cell membrane and occludin was predominantly expressed in the apicalmost areas of the cell membrane. Significant differences in the immunohistochemical scores of claudin-4 and claudin-7 were observed when comparing HCC and CC. CHC was positive for all of the TJPs examined in this study. The expression pattern of CoCC was found to be similar to that of CC. There were differences in the distribution of intensity scores of claudins-4 and -7 and occludin between CoCC and HCC. In addition, CHC was positive for Glypican-3 and CK-19. CoCC was positive for only CK-19. The results suggest that claudins-4 and -7 might be valuable markers for distinguishing HCC and CC and that CoCC might arise from hepatic ductal cells.

Full-length LGR5-positive cells have chemoresistant characteristics in colorectal cancer

Background:

Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is a target of Wnt signalling and considered both a cancer stem cell marker and intestinal stem cell marker. We found first some splice variants of LGR5 in human intestine and elucidated the functional feature of full-length LGR5 (LGR5FL).

Methods:

Reverse transcript PCR using mRNA extracted from intestine revealed the existence of LGR5 splice variants. We designed an antibody that recognises only LGR5FL and assessed immunohistochemically the distribution of LGR5FL-positive cells and Ki-67-positive cells in clinical samples.

Results:

Two LGR5 splice variants were expressed in the human intestine crypt cells; one lacked exon 5 and the other lacked exons 5–8. Only LGR5FL appeared during cell cycle arrest, whereas the transcript variants appeared when the cell cycle was proceeding. Immunohistochemistry and in situ hybridisation showed that LGR5FL-positive cells were negative for Ki-67. Comparing prechemotherapy and post-chemotherapy specimens, the population of LGR5FL-positive cells significantly increased with therapy (P<0.01).

Conclusions:

The function of LGR5FL-positive cells had low cell proliferative ability compared with the cells, which expressed splice variants of LGR5 and remained after chemotherapy. Designing therapeutic strategies that target LGR5FL-positive cells seems to be important in colorectal cancer.

The BMI1 inhibitor PTC-209 is a potential compound to halt cellular growth in biliary tract cancer cells

BMI1 is a core component of the polycomb repressive complex 1 (PRC1) and is up-regulated in biliary tract cancer (BTC), contributing to aggressive clinical features. In this study we investigated the cytotoxic effects of PTC-209, a recently developed inhibitor of BMI1, in BTC cells. PTC-209 reduced overall viability in BTC cell lines in a dose-dependent fashion (0.04 - 20 µM). Treatment with PTC-209 led to slightly enhanced caspase activity and stop of cell proliferation. Cell cycle analysis revealed that PTC-209 caused cell cycle arrest at the G1/S checkpoint. A comprehensive investigation of expression changes of cell cycle-related genes showed that PTC-209 caused significant down-regulation of cell cycle-promoting genes as well as of genes that contribute to DNA synthesis initiation and DNA repair, respectively. This was accompanied by significantly elevated mRNA levels of cell cycle inhibitors. In addition, PTC-209 reduced sphere formation and, in a cell line-dependent manner, aldehyde dehydrogease-1 positive cells. We conclude that PTC-209 might be a promising drug for future in vitro and in vivo studies in BTC.

Improved surgical outcomes for hilar cholangiocarcinoma: changes in surgical procedures and related outcomes based on 40 years of experience at a single institution

PURPOSE

This study aimed to examine the changes in procedures for hilar cholangiocarcinoma (HC) surgery and patient survival following HC surgery over a 40-year period.

METHODS

Between 1974 and 2014, 239 consecutive patients underwent surgery for HC. The changes in perioperative therapy and short- and long-term surgical outcomes were evaluated.

RESULTS

The rates of major hepatectomy (in particular, right hepatectomy) and R0 resection significantly increased. Blood loss, transfusion rate, morbidity, and surgical mortality all significantly decreased. The 5-year disease-specific survival was 9.29 % (n = 38) in 1974-1988, 41.1 % (n = 88) in 1989-2003 and 55.6 % (n = 57) in 2004-2008 (p = 0.0001: 1974-1988 vs 1989-2003, p < 0.0001:1974-1988 vs 2004-2008, p = 0.076: 1989-2003 vs 2004-2008). According to a multivariate analysis, Bismuth classification IV (HR vs I, 2.86), period 1989-2003 (HR vs 1974-1988, 0.31), 2004-2008 (HR vs 1974-1988, 0.26), and R1 or R2 resection (HR vs R0, 2.22) were independent prognostic factors.

CONCLUSION

The surgical outcomes for HC over the 40-year period clearly improved as a result of aggressive surgery and progress in surgical techniques, perioperative management, and diagnostic tools.

Tumor Microenvironment Versus Cancer Stem Cells in Cholangiocarcinoma: Synergistic Effects?

Cholangiocarcinoma (CCAs) may be defined as tumors that derived from the biliary tree with the differentiation in the biliary epithelial cells. This tumor is malignant, extremely aggressive with a poor prognosis. It can be treated surgically and its pathogenesis is poorly understood. The tumor microenvironment (TME) is a very important factor in the regulation of tumor angiogenesis, invasion, and metastasis. Besides cancer stem cells (CSCs) can modulate tumor growth, stroma formation, and migratory capability. The initial stage of tumorigenesis is characterized by genetic mutations and epigenetic alterations due to intrinsic factors which lead to the generation of oncogenes thus inducing tumorigenesis. CSCs may result from precancerous stem cells, cell de-differentiation, normal stem cells, or an epithelial-mesenchymal transition (EMT). CSCs have been found in the cancer niche, and EMT may occur early within the tumor microenvironment. Previous studies have demonstrated evidence of cholangiocarcinoma stem cells (CD133, CD24, EpCAM, CD44, and others) and the presence of these markers has been associated with malignant potential. The interaction between TME and cholangiocarcinoma stem cells via signaling mediators may create an environment that accommodates tumor growth, yielding resistance to cytotoxic insults (chemotherarapeutic). While progress has been made in the understanding of the mechanisms, the interactions in the tumorigenic process still remain a major challenge. Our review, addresses recent concepts of TME-CSCs interaction and will emphasize the importance of early detection with the use of novel diagnostic mechanisms such as CCA-CSC biomarkers and the importance of tumor stroma to define new treatments. J. Cell. Physiol. 231: 768-776, 2016. © 2015 Wiley Periodicals, Inc.

The green tea catechin epigallocatechin gallate induces cell cycle arrest and shows potential synergism with cisplatin in biliary tract cancer cells

Background

The green tea catechin epigallocatechin gallate (EGCG) was shown to effectively inhibit tumor growth in various types of cancer including biliary tract cancer (BTC). For most BTC patients only palliative therapy is possible, leading to a median survival of about one year. Chemoresistance is a major problem that contributes to the high mortality rates of BTC. The aim of this study was to investigate the cytotoxic effect of EGCG alone or in combination with cisplatin on eight BTC cell lines and to investigate the cellular anti-cancer mechanisms of EGCG.

Methods

The effect of EGCG treatment alone or in combination with the standard chemotherapeutic cisplatin on cell viability was analyzed in eight BTC cell lines. Additionally, we analyzed the effects of EGCG on caspase activity, cell cycle distribution and gene expression in the BTC cell line TFK-1.

Results

EGCG significantly reduced cell viability in all eight BTC cell lines (p < 0.05 or p < 0.01, respectively, for most cell lines and EGCG concentrations > 5 μM). Combined EGCG and cisplatin treatment showed a synergistic cytotoxic effect in five cell lines and an antagonistic effect in two cell lines. Furthermore, EGCG reduced the mRNA levels of various cell cycle-related genes, while increasing the expression of the cell cycle inhibitor p21 and the apoptosis-related death receptor 5 (p < 0.05). This observation was accompanied by an increase in caspase activity and cells in the sub-G1 phase of the cell cycle, indicating induction of apoptosis. EGCG also induced a down-regulation of expression of stem cell-related genes and genes that are associated with an aggressive clinical character of the tumor, such as cd133 and abcg2.

Conclusions

EGCG shows various anti-cancer effects in BTC cell lines and might therefore be a potential anticancer drug for future studies in BTC. Additionally, EGCG displays a synergistic cytotoxic effect with cisplatin in most tested BTC cell lines.

Graphical abstract

Expression of cancer stem cell biomarkers as a tool for a correct therapeutic approach to hepatocellular carcinoma

Liver cancer is the fifth most commonly diagnosed malignancy and the second most frequent cause of cancer death in men worldwide. Amongst liver cancers, hepatocellular carcinoma (HCC) represents the major histological subtype and it is one of the most common malignant human tumors worldwide. Research into the molecular biology of hepatocarcinogenesis has identified several biomarkers, which could provide additional informations in order to better understand the biology of HCC. A large number of biomarkers have been shown to have potential predictive significance and a wide variety of molecular markers have been proven to be excellent diagnostic tools for HCC but it is difficult to characterize HCC with a single biomarker. Thus, signatures of a combination of biomarkers may be more valuable for the diagnosis, staging and prognosis of HCC. Specifically, a correlation of HCC-CSCs phenotype to specific hepatic cancer subtypes and to specific clinical and pathological features has not yet been reported in human liver tumors. In this view we will first discuss the possible sources of liver stem cells and their relation with liver cancer development and we will secondly focus on the prognostic significance of clinical and pathological features of HCC.

BRCA/Fanconi anemia pathway implicates chemoresistance to gemcitabine in biliary tract cancer

The BRCA/Fanconi anemia (FA) pathway plays a key role in the repair of DNA double strand breaks. We focused on this pathway to clarify chemoresistance mechanisms in biliary tract cancer (BTC). We also investigated changes in the CD24⁺/44⁺ population that may be involved in chemoresistance, as this population likely includes cancer stem cells. We used three BTC cell lines to establish gemcitabine (GEM)-resistant (GR) cells and evaluated the expression of BRCA/FA pathway components, chemoresistance, and the effect of BRCA/FA pathway inhibition on the CD24⁺/44⁺ population. FANCD2 and CD24 expression were evaluated in 108 resected BTC specimens. GR cells highly expressed the BRCA/FA components. The BRCA/FA pathway was upregulated by GEM and cisplatin (CDDP) exposure. Inhibition using siRNA and RAD51 inhibitor sensitized GR cells to GEM or CDDP. The CD24⁺/44⁺ population was increased in GR and parent BTC cells treated with GEM or CDDP and highly expressed BRCA/FA genes. FANCD2 was related to CD24 expression in resected BTC specimens. Inhibition of the BRCA/FA pathway under GEM reduced the CD24⁺/44⁺ population in MzChA1-GR cells. Thus, high expression of the BRCA/FA pathway is one mechanism of chemoresistance against GEM and/or CDDP and is related to the CD24⁺/44⁺ population in BTC.

RFPL4A increases the G1 population and decreases sensitivity to chemotherapy in human colorectal cancer cells

Cell cycle-arrested cancer cells are resistant to conventional chemotherapy that acts on the mitotic phases of the cell cycle, although the molecular mechanisms involved in halting cell cycle progression remain unclear. Here, we demonstrated that RFPL4A, an uncharacterized ubiquitin ligase, induced G1 retention and thus conferred decreased sensitivity to chemotherapy in the human colorectal cancer cell line, HCT116. Long term time lapse observations in HCT116 cells bearing a "fluorescence ubiquitin-based cell cycle indicator" identified a characteristic population that is viable but remains in the G1 phase for an extended period of time (up to 56 h). Microarray analyses showed that expression of RFPL4A was significantly up-regulated in these G1-arrested cells, not only in HCT116 cells but also in other cancer cell lines, and overexpression of RFPL4A increased the G1 population and decreased sensitivity to chemotherapy. However, knockdown of RFPL4A expression caused the cells to resume mitosis and induced their susceptibility to anti-cancer drugs in vitro and in vivo. These results indicate that RFPL4A is a novel factor that increases the G1 population and decreases sensitivity to chemotherapy and thus may be a promising therapeutic target for refractory tumor conditions.

Pathogenesis of Cholangiolocellular Carcinoma: Possibility of an Interlobular Duct Origin

Cholangiolocellular carcinoma (CoCC) is categorized as a different entity from ordinary intrahepatic cholangiocarcinoma (ICC) due to its unique clinical, radiological and histological features. The lesion is supposed to originate from cholangioles, where hepatic stem/progenitor cells exist. However, the interlobular duct is also speculated to be the origin of CoCC. According to the findings of morphometric and immunohistochemical studies, CoCC closely resembles the interlobular duct. The unique clinical and pathological features of this disease can also be explained by the interlobular duct origin theory. The malignant counterparts of cholangioles and interlobular ducts have been categorized as CoCC to date. In order to differentiate between true CoCC (cholangiole origin) and pseudo-CoCC (interlobular duct origin), assessing the size of the cancer duct, positivity for c-Kit and coexistence of an ordinary ICC component is useful.

Integrins αvβ6, α6β4 and α3β1 are down-regulated in cholangiolocellular carcinoma but not cholangiocarcinoma

AIM

The aim of this study was to evaluate integrin expression and immunolocalization of the extracellular matrix proteins in cholangiolocellular carcinoma (CoCC).

METHODS

Tissue specimens of 23 CoCC, 28 cholangiocarcinomas (CCC), 42 hepatocellular carcinomas (HCC) and 11 classical type combined hepatocellular cholangiocarcinomas (CHC) were immunostained for β6, β4 and α3 integrins, fibronectin and laminin. ITGB6, B4 and A3 mRNA levels in six HCC cell lines, five CCC cell lines and two CHC cell lines were quantified by quantitative reverse transcription polymerase chain reaction.

RESULTS

Little or no positivity for β6, β4 and α3 integrins was shown in 91%, 91% and 52% of CoCC and 100%, 98% and 81% of HCC, respectively, according to immunostaining, whereas intense positive staining for these integrins was demonstrated in 64%, 96% and 75% of CCC, respectively. There was a close correlation between β4 and α3 integrin expression and intracytoplasmic laminin in CoCC, CCC and HCC, but not between β6 expression and its ligand, fibronectin. Integrin mRNA levels were increased in four of five CCC cell lines, but nearly undetectable in five of six HCC cell lines and one CHC cell line. Tubular differentiation of a CHC cell line cultured in collagen gel matrix induced upregulation of these integrins.

CONCLUSION

Our results first indicated downregulation of αvβ6, α6β4 and α3β1 integrins in CoCC, in contrast to its high expression in CCC, suggesting a diagnostic value of integrins in the differential diagnosis of CoCC and CCC, as well as a useful inducible marker of the intermediate features of CoCC.

Role of liver stem cells in hepatocarcinogenesis

Liver cancer is an aggressive disease with a high mortality rate. Management of liver cancer is strongly dependent on the tumor stage and underlying liver disease. Unfortunately, most cases are discovered when the cancer is already advanced, missing the opportunity for surgical resection. Thus, an improved understanding of the mechanisms responsible for liver cancer initiation and progression will facilitate the detection of more reliable tumor markers and the development of new small molecules for targeted therapy of liver cancer. Recently, there is increasing evidence for the “cancer stem cell hypothesis”, which postulates that liver cancer originates from the malignant transformation of liver stem/progenitor cells (liver cancer stem cells). This cancer stem cell model has important significance for understanding the basic biology of liver cancer and has profound importance for the development of new strategies for cancer prevention and treatment. In this review, we highlight recent advances in the role of liver stem cells in hepatocarcinogenesis. Our review of the literature shows that identification of the cellular origin and the signaling pathways involved is challenging issues in liver cancer with pivotal implications in therapeutic perspectives. Although the dedifferentiation of mature hepatocytes/cholangiocytes in hepatocarcinogenesis cannot be excluded, neoplastic transformation of a stem cell subpopulation more easily explains hepatocarcinogenesis. Elimination of liver cancer stem cells in liver cancer could result in the degeneration of downstream cells, which makes them potential targets for liver cancer therapies. Therefore, liver stem cells could represent a new target for therapeutic approaches to liver cancer in the near future.

Hypomethylation of long interspersed nuclear element-1 (LINE-1) is associated with poor prognosis via activation of c-MET in hepatocellular carcinoma

BACKGROUND

Long interspersed nuclear element-1 (LINE-1) methylation status, representing global DNA methylation levels, is associated with patient prognosis in several types of cancer. This study was designed to examine the prognostic significance of LINE-1 methylation in patients with hepatocellular carcinoma (HCC) and the possible mechanisms related to oncogene activation.

METHODS

Seventy-five HCC patients who underwent hepatectomy between 2006 and 2012 were enrolled in this study. Quantitative pyrosequencing was performed to quantify the methylation level of three CpG sites in the LINE-1 promoter. Clinicopathological variables and prognosis were compared between LINE-1 hypo- and hypermethylation groups. LINE-1-inserted c-MET (L1-MET) gene expression and its correlation with LINE-1 methylation levels also were analyzed.

RESULTS

LINE-1 was significantly hypomethylated in tumor tissues compared with nontumor tissues (48.3 ± 12.2 % vs. 68.2 ± 2.0 %, respectively, p < 0.0001). LINE-1 hypomethylation was not associated with any clinicopathological factors in HCC patients, except sex (p < 0.05). However, patients with LINE-1 hypomethylation exhibited significantly poorer outcome, and multivariate analysis revealed that LINE-1 hypomethylation was an independent risk factor for overall survival (hazard ratio (HR) = 6.1, p = 0.031) and disease-free survival (HR = 2.34, p = 0.045). L1-MET expression was significantly higher in tumor tissues (p < 0.01). L1-MET expression levels were inversely correlated with LINE-1 methylation levels, and positively correlated with c-MET expression (p < 0.05). Furthermore, higher c-MET protein expression was observed in the LINE-1 hypomethylated tumor tissues compared with hypermethylated tumor tissues (p = 0.032).

CONCLUSIONS

LINE-1 hypomethylation is significantly associated with poor prognosis in patients with HCC, possibly due to activation of c-MET expression.