Yunfei Yuan

A functional polymorphism in the miR-146a gene is associated with the risk for hepatocellular carcinoma

A G > C polymorphism (rs2910164) is located in the stem region opposite to the mature miR-146a sequence, which results in a change from G:U pair to C:U mismatch in the stem structure of miR-146a precursor. Here, we elucidated the biological significance of this polymorphism, based on cancer association study and cell model system. The cancer association study included 479 hepatocellular carcinoma (HCC) and 504 control subjects. We found that the genotype distribution of this polymorphism in HCC cases was significantly different from that in control subjects (P = 0.026). The association between the genotype and the risk of HCC was further analyzed using multivariate unconditional logistic regression, with adjustment for sex, age and hepatitis B virus status. The results revealed that male individuals with GG genotype were 2-fold more susceptible to HCC (odds ratio = 2.016, 95% confidence interval = 1.056-3.848, P = 0.034) compared with those with CC genotype. We next examined the influence of this polymorphism on the production of mature miR-146a and found that G-allelic miR-146a precursor displayed increased production of mature miR-146a compared with C-allelic one. Further investigations disclosed that miR-146a could obviously promote cell proliferation and colony formation in NIH/3T3, an immortalized but non-transformed cell line. These data suggest that the G > C polymorphism in miR-146a precursor may result in important phenotypic traits that have biomedical implications. Our findings warrant further investigations on the relation between microRNA polymorphism and human diseases.

MicroRNA-125b promotes apoptosis by regulating the expression of Mcl-1, Bcl-w and IL-6R

The microRNA miR-125b is multi-faceted, with the ability to function as a tumor suppressor or an oncogene, depending on the cellular context. To date, the pro-apoptotic role of miR-125b and its underlying mechanisms are unexplored. In this study, both gain- and loss-of-function experiments revealed that miR-125b expression not only induced spontaneous apoptosis in various cell lines derived from the liver, lung and colorectal cancers, but also sensitized cancer cells to diverse apoptotic stimuli, including nutrient starvation and chemotherapeutic treatment. Furthermore, downregulation of miR-125b was a frequent event in hepatocellular carcinoma (HCC) tissues, and the miR-125b level was positively associated with the rate of apoptosis in HCC tissues. Subsequent investigations identified Mcl-1, Bcl-w and interleukin (IL)-6R as direct targets of miR-125b. Restoration of miR-125b expression not only diminished the expression of Mcl-1 and Bcl-w directly but also indirectly reduced the Mcl-1 and Bcl-xL levels by attenuating IL-6/signal transducer and activator of transcription 3 signaling. Consistent with these findings, introduction of miR-125b reduced the mitochondrial membrane potential and promoted the cleavage of pro-caspase-3. These data indicate that miR-125b may promote apoptosis by suppressing the anti-apoptotic molecules of the Bcl-2 family and miR-125b downregulation may facilitate tumor development by conferring upon cells the capability to survive under conditions of nutrient deprivation and chemotherapeutic treatment. Our findings highlight the importance of miR-125b in the regulation of apoptosis and suggest miR-125b as an attractive target for anti-cancer therapy.

MicroRNA‐195 Suppresses Angiogenesis and Metastasis of Hepatocellular Carcinoma by Inhibiting the Expression of VEGF, VAV2, and CDC42

Hepatocellular carcinoma (HCC) is characterized by active angiogenesis and metastasis, which account for rapid recurrence and poor survival. There is frequent down‐regulation of miR‐195 expression in HCC tissues. In this study, the role of miR‐195 in HCC angiogenesis and metastasis was investigated with in vitro capillary tube formation and transwell assays, in vivo orthotopic xenograft mouse models, and human HCC specimens. Reduction of miR‐195 in HCC tissues was significantly associated with increased angiogenesis, metastasis, and worse recurrence‐free survival. Both gain‐of‐function and loss‐of‐function studies of in vitro models revealed that miR‐195 not only suppressed the ability of HCC cells to promote the migration and capillary tube formation of endothelial cells but also directly repressed the abilities of HCC cells to migrate and invade extracellular matrix gel. Based on mouse models, we found that the induced expression of miR‐195 dramatically reduced microvessel densities in xenograft tumors and repressed both intrahepatic and pulmonary metastasis. Subsequent investigations disclosed that miR‐195 directly inhibited the expression of the proangiogenic factor vascular endothelial growth factor (VEGF) and the prometastatic factors VAV2 and CDC42. Knockdown of these target molecules of miR‐195 phenocopied the effects of miR‐195 restoration, whereas overexpression of these targets antagonized the function of miR‐195. Furthermore, we revealed that miR‐195 down‐regulation resulted in enhanced VEGF levels in the tumor microenvironment, which subsequently activated VEGF receptor 2 signaling in endothelial cells and thereby promoted angiogenesis. Additionally, miR‐195 down‐regulation led to increases in VAV2 and CDC42 expression, which stimulated VAV2/Rac1/CDC42 signaling and lamellipodia formation and thereby facilitated the metastasis of HCC cells. Conclusion: miR‐195 deregulation contributes to angiogenesis and metastasis in HCC. The restoration of miR‐195 expression may be a promising strategy for HCC therapy. (Hepatology 2013;58:642‐653)

A novel GSK-3 beta–C/EBP alpha–miR-122–insulin-like growth factor 1 receptor regulatory circuitry in human hepatocellular carcinoma†

miR‐122 is a highly abundant, hepatocyte‐specific microRNA. The biomedical significance and regulatory mechanisms of miR‐122 remain obscure. We explored the role of miR‐122 in tumorigenesis in the context of gene regulatory network. The miR‐122 promoter and its transactivator were identified by way of luciferase reporter system, electrophoretic mobility shift, and chromatin immunoprecipitation assays. The miR‐122 regulatory circuitry and its implication in hepatocarcinogenesis were identified using livers of different development stages, human hepatocellular carcinoma (HCC) tissues and cell lines, and aflatoxin B1 (AFB1)‐transformed cells. We characterized the −5.3 to −4.8 kb region upstream of miR‐122 precursor as miR‐122 promoter. Further investigation revealed that deletion of predicted CCAAT/enhancer‐binding protein alpha (C/EBPα) binding sites C/EBPα knockdown significantly reduced miR‐122 promoter activity and endogenous miR‐122 expression; and C/EBPα directly interacted with the miR‐122 promoter in vitro and in vivo. These data suggest that C/EBPα is a transactivator for miR‐122 transcription. We further demonstrated that miR‐122 suppressed insulin‐like growth factor 1 receptor (IGF‐1R) translation and sustained glycogen synthase kinase‐3 beta (GSK‐3β) activity. The activated GSK‐3β not only repressed cell proliferation, but also activated C/EBPα, which maintained miR‐122 levels and thereby enforced IGF‐1R suppression. Interestingly, down‐regulation of miR‐122 and C/EBPα, and up‐regulation of IGF‐1R were frequently observed in HCC tissues, and decreased miR‐122 levels were associated with worse survival of HCC patients. Moreover, AFB1 exposure resulted in decreased activity in GSK‐3β, C/EBPα, and miR‐122 and increased levels of IGF‐1R, whereas restoration of miR‐122 suppressed the tumorigenicity of HCC and AFB1‐transformed cells. Conclusion: We have identified a novel GSK‐3β–C/EBPα–miR‐122–IGF‐1R regulatory circuitry whose dysfunction may contribute to the development of HCC. Our findings provide new insight into miR‐122s function and the mechanisms of hepatocarcinogenesis. (Hepatology 2010;52:1702‐1712)

Identification of MACC1 as a novel prognostic marker in hepatocellular carcinoma

BackgroundMetastasis-associated in colon cancer-1 (MACC1) is a newly identified gene that plays a role in colon cancer metastasis through upregulation of c-MET proto-oncogene (c-MET). However, the value of MACC1 as a potential biomarker for hepatocellular carcinoma (HCC) remains unknown.MethodsMACC1 mRNA expression in 128 HCC tissues was examined by quantitative polymerase chain reaction. To show the potential correlation of MACC1 and c-MET, c-MET was also analysed.ResultsMACC1 was more highly expressed in HCC than in non-HCC tissues (P = 0.009). High MACC1 expression was significantly increased in cases with high alpha fetoprotein (AFP) (P = 0.025). A positive correlation was found between MACC1 and c-MET mRNAs (r = 0.235, P = 0.009). Both univariate and multivariate analyses revealed that MACC1 expression was associated with overall survival (OS) and disease-free survival (DFS). Moreover, stratified analysis showed that tumour-node-metastasis (TNM) stage I patients with high MACC1 levels had shorter OS and DFS than those with low MACC1.ConclusionsMACC1 may identify low- and high-risk individuals with HCC and be a valuable indicator for stratifying the prognosis of TNM stage I patients. MACC1 may serve as a novel biomarker for HCC.

Frequent Epigenetic Inactivation of Spleen Tyrosine Kinase Gene in Human Hepatocellular Carcinoma

Purpose: The aim of present study was to investigate the methylation and expression status of spleen tyrosine kinase (SYK) in human hepatocellular carcinoma (HCC) and to evaluate this information for its ability to predict disease prognosis. E-cadherin and TIMP-3 methylation was also analyzed here as control because both were associated with poor prognosis in some types of tumors. Experimental Design: We analyzed the methylation status of SYK, E-cadherin, and TIMP-3 in 124 cases of HCC and assessed the correlation of such methylations with clinicopathologic variables and prognosis after tumor resection. Results: We found that SYK, E-cadherin, and TIMP-3 genes were methylated in 27%, 27%, and 42% of HCC neoplastic tissues, respectively. The loss of SYK mRNA or Syk protein expression was highly correlated with SYK gene methylation. The patients with methylated SYK in neoplastic tissues had a significantly lower overall survival rate after hepatectomy than those with unmethylated SYK. No significant difference in overall survival rates, however, was found between groups of patients with methylated and unmethylated E-cadherin or TIMP-3. Patients with negative Syk protein expression had a significantly lower overall survival rate than those with positive Syk protein expression. Multivariate analyses indicated that factors affecting overall survival were tumor-node-metastasis stage, Child-Pugh classification, SYK methylation, or Syk protein status. Conclusions: Our results indicate that SYK methylation and loss of Syk expression in HCC neoplastic tissues are independent biomarkers of poor patient outcome and that determination of SYK methylation or Syk expression status may offer guidance for selecting appropriate treatments.

CHK1 targets spleen tyrosine kinase (L) for proteolysis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies resistant to current chemotherapies or radiotherapies, which makes it urgent to identify new therapeutic targets for HCC. In this study, we found that checkpoint kinase 1 (CHK1) was frequently overexpressed and correlated with poor clinical outcome in patients with HCC. We further showed that the CHK1 inhibitor GÖ6976 was capable of sensitizing HCC cells to cisplatin, indicating that CHK1 may have oncogenic function in HCC. We found that CHK1 phosphorylated the tumor suppressor spleen tyrosine kinase (L) (SYK[L]) and identified the phosphorylation site at Ser295. Furthermore, CHK1 phosphorylation of SYK(L) promoted its subsequent proteasomal degradation. Expression of a nonphosphorylated mutant of SYK(L) was more efficient at suppressing proliferation, colony formation, mobility, and tumor growth in HCC lines. Importantly, a strong inverse correlation between the expression levels of CHK1 and SYK(L) was observed in patients with HCC. Collectively, our data demonstrate that SYK(L) is a substrate of CHK1 in tumor cells and suggest that targeting the CHK1/SYK(L) pathway may be a promising strategy for treating HCC.

Role of Sox2 and Oct4 in predicting survival of hepatocellular carcinoma patients after hepatectomy

OBJECTIVES The present study was aimed to explore the prognostic strength of Sox2 and Oct4A in hepatocellular carcinoma (HCC). DESIGN AND METHODS We investigated the expression of Sox2 and Oct4A in five hepatoma cell lines, one immortalized normal liver cell line, HCC tissues with matched nontumorous liver tissues and normal liver tissues by reverse transcription-polymerase chain reaction. RESULTS Sox2 and Oct4A mRNA were overexpressed in hepatoma cell lines and tumor tissues. Sox2 or Oct4A positive expression was significantly associated with an aggressive phenotype. Both univariate and multivariate analyses revealed that Sox2 or Oct4A was an independent prognostic factor for HCC. When using subgroup analysis, the patients with a co-expression of Sox2/Oct4A had the poorest prognosis. Further analysis demonstrated that Sox2 alone or Sox2/Oct4A could stratify outcome in HCC patients with early stage. CONCLUSIONS Sox2 and Oct4A can be novel predictors of poor prognosis for patients undergoing resection of HCC.

Large-scale analysis of the genetic and epigenetic alterations in hepatocellular carcinoma from Southeast China

Our knowledge about molecular alterations during hepatocarcinogenesis is still fragmentary, due to lack of comprehensive genetic and epigenetic analyses in the same set of hepatocellular carcinomas (HCCs). In this study, we conducted a large-scale analysis, including mutation screening in 50 genes and methylation assays in three genes in 54 pairs of HCCs and their neighboring non-cancerous tissues. All samples were collected from the residents in Southeast China. We found HBV infection and chronic hepatitis/cirrhosis in 83.3% and 98.1% of the cases, respectively. Mutations were identified in 18 out of 54 (33.3%) samples, with p53 alterations in 14 cases and beta-catenin mutations in four tumors. No mutations were identified in the neighboring tissues. Interestingly, 9 out of 14 (64.3%) tumors carrying p53 mutations displayed substitution of serine by arginine at codon 249, a characteristic change believed to be induced by aflatoxin-B1. Furthermore, p53 mutation was significantly associated with shorter recurrence-free survival (P=0.004). The results also revealed aberrant methylation in two or more genes in as high as 90% of tumors and 40% of adjacent tissues. The frequency of RASSF1A hypermethylation was much higher than that of p16INK4a and HAI2 in both HCC and neighboring tissues, indicating that deregulation of RASSF1A may precede the other two genes. These data suggest that aberrant methylation occurs before mutation and is an early event in the development of this set of HCC. Our findings highlight p53 as a prognostic factor of HCC and RASSF1A as a potential target in preventing malignant transformation of hepatocytes.

Effects of antiviral therapy on hepatitis B virus reactivation and liver function after resection or chemoembolization for hepatocellular carcinoma

How hepatitis B virus (HBV) infection react to hepatocellular carcinoma (HCC) treatment remains unclear, and the roles of anti‐HBV therapy were seldom reported in HCC.