抑癌基因PTEN在原发性肝癌中的表达及意义

目的 研究抑癌基因PTEN在原发性肝癌发生过程中的作用及意义。方法 应用免疫组织化学和northern杂交分析60例原发性肝癌及对应癌旁组织中PTEN mRNA及PTEN蛋白表达情况,结合患者的临床病理资料分析PTEN在原发性肝肝癌中的意义。结果 PTEN蛋白明确定位于肝细胞胞浆内。60例HCC的癌组织中,PTEN蛋白阳性率为48.3％(29/60),明显低于癌旁肝组织的阳性率(100％)。PTEN蛋白在肝癌组织内的表达阳性率与肝癌的病理学分级、有无癌栓有关,PTEN蛋白在肝癌组织的Ⅰ～Ⅱ级、Ⅲ级、Ⅳ级的阳性率分别为84.0％、23.8％、21.4％,无癌栓形成组PTEN蛋白表达的阳性率为55.56%,有癌栓形成组PTEN蛋白表达的阳性率为26.7％。Northern杂交显示,PIEN基因在肝癌细胞内存在四个转录子,其大小分别为5.5、4.4、2.4、1.8 kb。患者肝癌组织内PTEN mRNA的表达水平明显低于对应的癌旁肝组织。PTEN 5.5 kb和4.4 kb的转录子表达水平的降低与血清中AFP水平、有无癌栓、有无卫星灶及病理学分级有关;2.4 kb的转录子表达水平降低与患者有无癌栓、有无卫星灶有关;1.8 kb转录子表达水平的降低与临床病理学指标无关。结论 PTEN在肝癌的发生过程中可能起重要作用,其表达水平有可能作为反映肝癌进展和预后的病理学指标。     

Genetic and epigenetic alterations of the KLF6 gene in hepatocellular carcinoma

BACKGROUND AND AIM: Kruppel-like factor 6 (KLF6) is a zinc finger tumor suppressor gene that is frequently mutated in several human cancers and is broadly involved in differentiation and development, growth-related signal transduction, cell proliferation, apoptosis, and angiogenesis. The aim of this study was to elucidate the potential etiological role of KLF6 in the development of hepatocellular carcinoma (HCC) in Korea. METHODS: The gene mutation, allelic loss, and methylation status of the KLF6 gene was analyzed in a series of 85 Korean patients: 21 with dysplastic nodules and 85 with HCC. RESULTS: No somatic mutations were observed in the patients with dysplastic nodules or with HCC. Allelic loss was found in five (6.8%) of 73 informative HCC tissues. Three of the five patients with allelic loss had HCC with hepatitis B virus infection and cirrhosis, and the remaining two had no viral infection and a non-specific background. In methylation analysis, unmethylated and methylated DNAs of the KLF6 gene were amplified in all corresponding non-neoplastic liver tissues. Only one HCC tissue showed methylated DNA without unmethylated DNA. CONCLUSIONS: The results suggest that genetic and epigenetic alteration of KLF6 may play a minor role in the development of HCC.     

Genetic alterations of Wnt signaling pathway-associated genes in hepatocellular carcinoma

Background and Aim: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Recently, abnormal activation of the Wnt pathway has been found to be involved in the carcinogenesis of HCC. However, the relationship between genetic changes in the Wnt pathway–associated genes and its protein expression has not been studied in patients with HCC and cirrhotic nodules. The purpose of this study is to explore the contribution of inappropriate activation of the Wnt pathway in liver carcinogenesis. Methods: Somatic mutation in exons 3–5 of AXIN1 and exon 3 of β‐catenin were analyzed by direct sequencing and expression of axin and β‐catenin proteins by immunohistochemistry in a series of 36 patients with HCC and cirrhosis. Results: The AXIN1 and β‐catenin gene mutations were observed in 25% (9/36) and 2.8% (1/36) of HCCs, respectively. All mutations detected in AXIN1 and β‐catenin genes were missense point mutations. Abnormal nuclear expression of β‐catenin was observed in 11 of 36 cases of HCCs (30.6%), but not in cirrhotic nodules. Reduced or absent expression of axin was seen in 24 of 36 HCCs (66.7%). The abnormal expression of β‐catenin and axin proteins was closely correlated with mutations of AXIN1 and β‐catenin (P < 0.0001 and P = 0.008, respectively). Conclusions: These data suggest that mutation of AXIN1 gene is a frequent and late event for HCC associated with cirrhosis, and is correlated significantly with abnormal expression of axin and β‐catenin. Therefore, activation of Wnt signaling through AXIN1 rather than β‐catenin mutation might play an important role in liver carcinogenesis.     

抑癌基因PTEN及p53在肝细胞肝癌中表达的免疫组化研究

为探讨肝细胞肝癌组织中抑癌基因PTEN及p53蛋白的表达情况及临床病理意义。应用免疫组织化学技术检测了41例肝细胞肝癌及其相应的癌旁组织中PTEN和p53蛋白的表达情况。41例癌旁组织PTEN全部阳性表达,肝细胞肝癌组织中PTEN阳性表达率39％,阳性信号显示于胞浆中。p53阳性表达率51％,PTEN蛋白在肝细胞肝癌组织中的阳性表达与组织分化程度明显相关,高分化癌的阳性率为73％,低分化癌阳性率27％。肝细胞肝癌细胞中存在较高比例的PTEN蛋白阴性表达,说明在肝细胞肝癌的发生发展中PTEN基因失活起着重要作用,它的阳性表达可能有一定的预后意义。     

Clinical implications of DNA methylation in hepatocellular carcinoma

Background

Epigenetics is a rapidly evolving field of genetic study applicable to nearly every aspect of genome-related research. The importance of epigenetics has been recognised in human hepatocellular carcinoma (HCC). Changes in DNA methylation patterns, including global hypomethylation and promoter hypermethylation, are thought to be early events in hepatocarcinogenesis.

Objectives

This review aimed to summarise the role of epigenetics in HCC, to describe the mechanisms of epigenetic changes in HCC and to examine the clinical relevance of epigenetics in HCC.

Methods

This review examines the role of CpG-rich regions and DNA methylation, and describes an epigenetic model of cancer, tumour type-specific methylation, the relationships among methylation, cirrhosis and hepatocarcinogenesis, and the role of DNA methylation in HCC. The clinical implications of epigenetics in HCC are discussed.

Results

A multivariate predictor model based on traditional clinical factors and DNA methylation profile may have important applications in the early detection of neoplastic transformation in populations at high risk for HCC. CpG methylation may be valuable in HCC prognostics. DNA methylation profiles may enable clinical prediction in pre-therapy patient biopsies, paraffin-embedded samples or plasma DNA.

Conclusions

Epigenetic changes and profiles may correlate to the biological behaviour of tumours and clinical outcome of HCC patients. The use of DNA methylation profiles as a surrogate biomarker remains an active area of clinical cancer research.     

生存素、p27和PTEN在肝细胞癌中的表达及临床病理意义

目的 探讨生存素蛋白、生存素mRNA、p27蛋白、p27 mRNA和第10号染色体同源丢失性磷酸酶张力蛋白基因(PTEN)蛋白在肝细胞癌(HCC)中的表达及其临床病理意义.方法 自制组织芯片,采用免疫组织化学和原位杂交法检测生存素蛋白、p27蛋白、PTEN蛋白和生存素mRNA、p27 mRNA在141份肝细胞癌、128份癌旁肝组织、97份远癌肝组织及17份正常肝组织中的表达,探讨各指标的关系并建立预测肝癌发生的模型.结果 肝癌组中生存素蛋白(Ridit值的95%CI为0.689±0.048,P《0.01)、生存素mRNA(Ridit值的95% CI为0.690±0.049,P《0.01)和p27蛋白(Ridit值的95% CI为0.556±0.053,P《0.05)表达明显增高,PTEN(Ridit值的95% CI为0.282±0.048)表达明显下降(P《0.01);肝癌中生存素的表达与p27、PTEN表达均显著相关;生存素mRNA、p27蛋白和PTEN蛋白对判断肝癌发生与否有重要意义.结论 生存素mRNA、p27蛋白的表达上调和PTEN蛋白的表达下调可作为判断肝癌发生的有价值指标.     

Review of genetic and epigenetic alterations in hepatocarcinogenesis

Abstract   Hepatocellular carcinoma (HCC) is associated with multiple risk factors and is believed to arise from pre-neoplastic lesions, usually in the background of cirrhosis. However, the genetic and epigenetic events of hepatocarcinogenesis are relatively poorly understood. HCC display gross genomic alterations, including chromosomal instability (CIN), CpG island methylation, DNA rearrangements associated with hepatitis B virus (HBV) DNA integration, DNA hypomethylation and, to a lesser degree, microsatellite instability. Various studies have reported CIN at chromosomal regions, 1p, 4q, 5q, 6q, 8p, 10q, 11p, 16p, 16q, 17p and 22q. Frequent promoter hypermethylation and subsequent loss of protein expression has also been demonstrated in HCC at tumor suppressor gene (TSG), p16 , p14 , p15 , SOCS1, RIZ1, E-cadherin and 143-3  . An interesting observation emerging from these studies is the presence of a methylator phenotype in hepatocarcinogenesis, although it does not seem advantageous to have high levels of microsatellite instability. Methylation also appears to be an early event, suggesting that this may precede cirrhosis. However, these genes have been studied in isolation and global studies of methylator phenotype are required to assess the significance of epigenetic silencing in hepatocarcinogenesis. Based on previous data there are obvious fundamental differences in the mechanisms of hepatic carcinogenesis, with at least two distinct mechanisms of malignant transformation in the liver, related to CIN and CpG island methylation. The reason for these differences and the relative importance of these mechanisms are not clear but likely relate to the etiopathogenesis of HCC. Defining these broad mechanisms is a necessary prelude to determine the timing of events in malignant transformation of the liver and to investigate the role of known risk factors for HCC.     

Alterations of epigenetics and microRNA in hepatocellular carcinoma

Studies have shown that alterations of epigenetics and microRNA (miRNA) play critical roles in the initiation and progression of hepatocellular carcinoma (HCC). Epigenetic silencing of tumor suppressor genes in HCC is generally mediated by DNA hypermethylation of CpG island promoters and histone modifications such as histone deacetylation, methylation of histone H3 lysine 9 (H3K9) and tri‐methylation of H3K27. Chromatin‐modifying drugs such as DNA methylation inhibitors and histone deacetylase inhibitors have shown clinical promise for cancer therapy. miRNA are small non‐coding RNA that regulate expression of various target genes. Specific miRNA are aberrantly expressed and play roles as tumor suppressors or oncogenes during hepatocarcinogenesis. We and other groups have demonstrated that important tumor suppressor miRNA are silenced by epigenetic alterations, resulting in activation of target oncogenes in human malignancies including HCC. Restoring the expression of tumor suppressor miRNA by inhibitors of DNA methylation and histone deacetylase may be a promising therapeutic strategy for HCC.     

PTEN hypermethylation profiles of Chinese Kazakh patients with esophageal squamous cell carcinoma

Aberrant DNA methylation of promoter region CpG islands may serve as an alternative mechanism to genetic defects in the inactivation of tumor suppressor genes (TSGs) in human malignancies. The aim of this study was to examine the promoter methylation status of the PTEN TSG and its association with esophageal squamous cell carcinoma (ESCC) carcinogenesis in a Chinese Kazakh population, which is known to have a relatively high ESCC incidence and mortality. The methylation status of the PTEN promoter region was determined in patients with ESCC (n = 95) and healthy individuals (n = 65) using highly sensitive Sequenom Epityper assays. The methylation level of the PTEN gene was significantly higher in patients with ESCC than in healthy controls. The median methylation level was 10.0% (interquartile range [IQR]: 7.0–11.0%) in patients with ESCC and 6.0% in controls (IQR: 4.0–9.0%; P = 0.001). PTEN methylation levels were higher in male patients with ESCC than in male controls, whereas a trend toward significance was observed between female patients with ESCC and female controls (P = 0.005 and P = 0.086, respectively). The PTEN methylation level was associated with histopathological grade and lymph node metastasis in patients with ESCC (P = 0.002 and P = 0.009, respectively). To our knowledge, this is the first report to show the presence of PTEN promoter CpG hypermethylation in ESCC and its association with tumor metastasis.     

Involvement of PI3K/PTEN/AKT/mTOR pathway in invasion and metastasis in hepatocellular carcinoma: Association with MMP-9

Aim:  To investigate the status of Phosphatidylinositol 3-kinase (PI3K)/PTEN/AKT/mammalian target of rapamycin (mTOR) pathway and its correlation with clinicopathological features and matrix metalloproteinase-2, -9 (MMP-2, 9) in human hepatocellular carcinoma (HCC).
Methods:  PTEN, Phosphorylated AKT (p-AKT), Phosphorylated mTOR (p-mTOR), MMP-2, MMP-9 and Ki-67 expression levels were evaluated by immunohistochemistry on tissue microarrays containing 200 HCCs with paired adjacent non-cancerous liver tissues. PTEN, MMP-2 and MMP-9 mRNA levels were determined by real-time RT-PCR in 36 HCCs. The relationships between PI3K/PTEN/AKT/mTOR pathway and clinicopathological factors and MMP-2, 9 were analyzed in HCC.
Results:  In HCC, PTEN loss and overexpression of p-AKT and p-mTOR were associated with tumor grade, intrahepatic metastasis, vascular invasion, TNM stage and high Ki-67 labeling index ( P  < 0.05). PTEN loss was correlated with p-AKT, p-mTOR and MMP-9 overexpression. Furthermore, PTEN and MMP-2, 9 mRNA levels were down-regulated and up-regulated in HCC compared with paired non-cancerous liver tissues, respectively ( P  < 0.01). PTEN, MMP-2 and MMP-9 mRNA levels were correlated with tumor stage and metastasis. There was an inverse correlation between PTEN and MMP-9 mRNA expression. However, PI3K/PTEN/AKT/mTOR pathway was not correlated with MMP-2.
Conclusions:  PI3K/PTEN/AKT/mTOR pathway, which is activated in HCC, is involved in invasion and metastasis through up-regulating MMP-9 in HCC.     

Genome-wide association study: new genetic insights into HBV/HCV-related hepatocellular carcinoma genomes

Hepatocellular carcinoma (HCC) is the third common cause of cancer-related death with highest prevalence in developing countries, such as Southeast China and Saharan African. The major pathogenic factors can be categorized into environmental effects and genetic variations, and it is mostly caused by hepatitis B or C virus (HBV and HCV). The geographic prevalence of chronic hepatitis B and C (CHB and CHC) varies, with HBV heavily-infected in developing countries and HCV prevalent in developed countries. The infection of either hepatitis virus B or C causes damage to the liver cells through cellular immune attack by the mechanism of inflammation. However, how liver cell injury progresses to HCC development is still poorly understood. Along with the maturation of genome-wide association study (GWAS) technology, the specific genetic mutations responsible for the progression from CHB or CHC to HCC have been identified. Moreover, the findings of similar studies for these variants are different from each other due to diverse populations. More functional experiments are warranted to confirm the precise roles of these genetic mutations in the correlations between HBV/HCV and HCC for the future clinical application.     

Fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma is an uncommon malignancy seen in young adults without underlying liver disease. Physical signs are minimal and laboratory values are noncontributory. Diagnosis is suggested by clinical history, supported by radiographic studies, and confirmed by histologic examination. Individuals with fibrolamellar carcinoma generally have a greater survival than those with hepatocellular carcinoma. Although most patients with fibrolamellar carcinoma undergo curative surgery, two of the three patients we report had inoperable tumors.     

HBV基因突变与肝细胞癌发生关系研究进展

HBV感染是引起肝细胞癌(hepatocellular carcinoma,HCC)发生的主要因素,我国HCC患者中的HBs Ag阳性率为60%~70%,因此HBV防治成为全球医疗热点问题。HBV包含4个开放阅读框(pre S/S、pre C/C、P、X),它们中的各种点突变、缺失、插入及截短突变与HCC发生相关。一些突变和乙型肝炎重症化有关,可作为预测HCC发生的生物学指标;一些突变产生的特定HBV抗原直接或间接调节细胞周期及细胞凋亡等相关蛋白分子,促进细胞增殖及染色体不稳定,增加HCC发生风险。     

乙型肝炎病毒与肝细胞癌关系研究进展鲍曼不动杆菌感染暴发的流行病学调查

[摘要]　HBV是一种诱发急、慢性乙型肝炎的DNA病毒,HBV感染是引起肝细胞癌（hepatocellular carcinoma, HCC）的主要原因之一。HBV诱发HCC是一个多因素、多阶段的过程,包括HBV DNA整合到宿主基因中、HBV基因组突变和病毒调节蛋白HBx异常表达等分子机制,异常免疫攻击介导慢性肝损害的免疫机制和DNA甲基化等表观遗传相关机制以及细胞自噬。本文将对近年来HBV诱发HCC的各种机制的研究进展进行综述。