Clinical significance of increased expression of Nijmegen breakage syndrome gene (NBS1) in human primary liver cancer

The role of DNA damage and repair in liver cancer

Hepatocellular carcinoma is rapidly becoming a major cause of global mortality due to the ever-increasing prevalence of obesity. DNA damage is known to play an important role in cancer initiation, however DNA repair systems are also vital for the survival of cancer cells. Given the function of the liver and its exposure to the gut, it is likely that DNA damage and repair would be of particular importance in hepatocellular carcinoma. However, many contemporary reports have neglected the role of individual pathways of DNA damage and repair in their hypotheses. This review, therefore, aims to provide a concise overview for researchers in the field of liver cancer to understand the pathways of DNA damage and repair and their individual roles in hepatocellular carcinoma.

Non-HFE mutations in haemochromatosis in China: combination of heterozygous mutations involving HJV signal peptide variants

INTRODUCTION

Hereditary haemochromatosis (HH) caused by a homozygous p.C282Y mutation in haemochromatosis (HFE) gene has been well documented. However, less is known about the causative non-HFE mutation. We aimed to assess mutation patterns of haemochromatosis-related genes in Chinese patients with primary iron overload.

METHODS

Patients were preanalysed for mutations in the classic HH-related genes: HFE, HJV, HAMP, TFR2 and SLC40A1. Whole exome sequencing was conducted for cases with variants in HJV signal peptide region. Representative variants were analysed for biological function.

RESULTS

None of the cases analysed harboured the HFE p.C282Y; however, 21 of 22 primary iron-overload cases harboured at least one non-synonymous variant in the non-HFE genes. Specifically, p.E3D or p.Q6H variants in the HJV signal peptide region were identified in nine cases (40.9%). In two of three probands with the HJV p.E3D, exome sequencing identified accompanying variants in BMP/SMAD pathway genes, including TMPRSS6 p.T331M and BMP4 p.R269Q, and interestingly, SUGP2 p.R639Q was identified in all the three cases. Pedigree analysis showed a similar pattern of combination of heterozygous mutations in cases with HJV p.E3D or p.Q6H, with SUGP2 p.R639Q or HJV p.C321X being common mutation. In vitro siRNA interference of SUGP2 showed a novel role of downregulating the BMP/SMAD pathway. Site-directed mutagenesis of HJV p.Q6H/p.C321X in cell lines resulted in loss of membrane localisation of mutant HJV, and downregulation of p-SMAD1/5 and HAMP.

CONCLUSION

Compound heterozygous mutations of HJV or combined heterozygous mutations of BMP/SMAD pathway genes, marked by HJV variants in the signal peptide region, may represent a novel aetiological factor for HH.

Genetic variation of acquired structural chromosomal aberrations

Human malignancies are often hallmarked with genomic instability, which itself is also considered a causative event in malignant transformation. Genomic instability may manifest itself as genetic changes in the nucleotide sequence of DNA, or as structural or numerical changes of chromosomes. Unrepaired or insufficiently repaired DNA double-strand breaks, as well as telomere shortening, are important contributors in the formation of structural chromosomal aberrations (CAs). In the present review, we discuss potential mechanisms behind the formation of CAs and their relation to cancer. Based on our own studies, we also illustrate how inherited genetic variation may modify the frequency and types of CAs occurring in humans. Recently, we published a series of studies on variations in genes relevant to maintaining genomic integrity, such as those encoding xenobiotic-metabolising enzymes, DNA repair, the tumour suppressor TP53, the spindle assembly checkpoint, and cyclin D1 (CCND1). While individually genetic variation in these genes exerted small modulating effects, in interactions they were associated with CA frequencies in peripheral blood lymphocytes of healthy volunteers. Moreover, we observed opposite associations between the CCND1 splice site polymorphism rs9344 G870A and the frequency of CAs compared to their association with translocation t(11,14). We discuss the functional consequences of the CCND1 gene in interplay with DNA damage response and DNA repair during malignant transformation. Our review summarizes existing evidence that gene variations in relevant cellular pathways modulate the frequency of CAs, predominantly in a complex interaction. More functional/mechanistic studies elucidating these observations are required. Several questions emerge, such as the role of CAs in malignancies with respect to a particular phenotype and heterogeneity, the formation of CAs during the process of malignant transformation, and the formation of CAs in individual types of lymphocytes in relation to the immune response.

A non-synonymous polymorphism in NBS1 is associated with progression from chronic hepatitis B virus infection to hepatocellular carcinoma in a Chinese population

PURPOSE

Nijmegen breakage syndrome 1 (NBS1) has a vital role in DNA double-strand break (DSB) repair, functioning as a sensor to identify and repair DNA damage and maintaining genomic stability by participating in the intra-S-phase checkpoint. Polymorphisms of NBS1 have been investigated in multiple cancers with variable results. To our best knowledge, no previous study has focused on the association between NBS1 single-nucleotide polymorphisms (SNPs) and hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Five NBS1 SNPs were selected based on their potential functional impact. A hospital-based cohort, comprising 481 patients with HBV-related HCC, 508 patients with chronic hepatitis B virus infection (CHB), and 581 healthy controls, was recruited for genotyping analysis.

RESULTS

After quality control, four SNPs were successfully genotyped (rs10464867, rs1063053, rs1805794, and rs709816), none of which were significantly associated with HCC or CHB compared with those of healthy controls. Similarly, the combined HBV-infected group (including the HCC and CHB groups) exhibited no significant associations with these SNPs compared with healthy controls. In contrast, comparison of the frequency of rs1805794 between patients with CHB and those with HCC identified a significant association (P=2.99E-03, odds ratio =1.31, 95% confidence interval =1.10-1.56).

CONCLUSION

These findings suggest that, as a non-synonymous SNP, the rs1805794 C/G polymorphism may play a role in the progression from CHB to HCC.

Potential Strategies to Target Protein-Protein Interactions in the DNA Damage Response and Repair Pathways

This review article discusses some insights about generating novel mechanistic inhibitors of the DNA damage response and repair (DDR) pathways by focusing on protein-protein interactions (PPIs) of the key DDR components. General requirements for PPI strategies, such as selecting the target PPI site on the basis of its functionality, are discussed first. Next, on the basis of functional rationale and biochemical feasibility to identify a PPI inhibitor, 26 PPIs in DDR pathways (BER, MMR, NER, NHEJ, HR, TLS, and ICL repair) are specifically discussed for inhibitor discovery to benefit cancer therapies using a DNA-damaging agent.

Hepatocellular carcinoma mouse models: Hepatitis B virus-associated hepatocarcinogenesis and haploinsufficient tumor suppressor genes

The multifactorial and multistage pathogenesis of hepatocellular carcinoma (HCC) has fascinated a wide spectrum of scientists for decades. While a number of major risk factors have been identified, their mechanistic roles in hepatocarcinogenesis still need to be elucidated. Many tumor suppressor genes (TSGs) have been identified as being involved in HCC. These TSGs can be classified into two groups depending on the situation with respect to allelic mutation/loss in the tumors: the recessive TSGs with two required mutated alleles and the haploinsufficient TSGs with one required mutated allele. Hepatitis B virus (HBV) is one of the most important risk factors associated with HCC. Although mice cannot be infected with HBV due to the narrow host range of HBV and the lack of a proper receptor, one advantage of mouse models for HBV/HCC research is the numerous and powerful genetic tools that help investigate the phenotypic effects of viral proteins and allow the dissection of the dose-dependent action of TSGs. Here, we mainly focus on the application of mouse models in relation to HBV-associated HCC and on TSGs that act either in a recessive or in a haploinsufficient manner. Discoveries obtained using mouse models will have a great impact on HCC translational medicine.

An Analysis of Immunoreactive Signatures in Early Stage Hepatocellular Carcinoma

Background

Hepatocellular carcinoma (HCC) is prevalent worldwide and early diagnosis of HCC is critical for effective treatment and optimal prognosis.

Methods

Serum was screened first by immunoproteomic analysis for HCC-related tumor associated antigens (TAAs). Selected TAAs were clinically evaluated retrospectively in patients with HCC, liver cirrhosis, chronic hepatitis and healthy controls. Levels of autoantibody to the selected TAAs were measured by protein microarrays containing protein antigens of the candidate TAAs. Analyses were done by using receiver operating characteristics (ROC) to calculate diagnostic accuracy.

Findings

Twenty-two candidate TAAs were assessed by protein microarray analysis in 914 participants with serum α-fetoprotein (AFP) available. Twelve candidate TAAs were statistically different in signal intensity between HCC and controls. Among them, CENPF, HSP60 and IMP-2 showed AUC (area under the curve) values of 0.826, 0.764 and 0.796 respectively for early HCC. The highest prevalence of autoantibody positivity was observed in HCC cases with BCLC tumor stage A, well-differentiated histology and Child-Pugh grade C. Specifically, 73.6% or 79.3% cases of early HCC with negative AFP were positive for autoantibody to CENPF or HSP60.

Interpretation

Tumor-associated autoimmune reactions may be triggered by early stage HCCs. Measurement of serum autoantibody to TAAs may be complementary to AFP measurements and improve diagnosis of early HCC.

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Tumor-associated autoimmune reaction may be triggered by early stage HCCs, and TAAs may be potential marker for early HCC.

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Measurement of autoantibody to TAAs may be complementary to AFP measurements and improve diagnosis of early HCC.

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Generation of autoantibody to CENPF may result from autoimmune reaction in response to overexpression of CENPF in tumor cell.