Polymorphisms of base-excision repair genes and the hepatocarcinogenesis

A spliceosome-associated gene signature aids in predicting prognosis and tumor microenvironment of hepatocellular carcinoma

Splicing alterations have been shown to be key tumorigenesis drivers. In this study, we identified a novel spliceosome-related genes (SRGs) signature to predict the overall survival (OS) of patients with hepatocellular carcinoma (HCC). A total of 25 SRGs were identified from the GSE14520 dataset (training set). Univariate and least absolute shrinkage and selection operator (LASSO) regression analyses were utilized to construct the signature using genes with predictive significance. We then constructed a risk model using six SRGs (BUB3, IGF2BP3, RBM3, ILF3, ZC3H13, and CCT3). The reliability and predictive power of the gene signature were validated in two validation sets (TCGA and GSE76427 dataset). Patients in training and validation sets were divided into high and low-risk groups based on the gene signature. Patients in high-risk groups exhibited a poorer OS than in low-risk groups both in the training set and two validation sets. Next, risk score, BCLC staging, TNM staging, and multinodular were combined in a nomogram for OS prediction, and the decision curve analysis (DCA) curve exhibited the excellent prediction performance of the nomogram. The functional enrichment analyses demonstrated high-risk score patients were closely related to multiple oncology characteristics and invasive-related pathways, such as Cell cycle, DNA replication, and Spliceosome. Different compositions of the tumor microenvironment and immunocyte infiltration ratio might contribute to the prognostic difference between high and low-risk score groups. In conclusion, a spliceosome-related six-gene signature exhibited good performance for predicting the OS of patients with HCC, which may aid in clinical decision-making for individual treatment.

Genetic polymorphisms in DNA repair genes and hepatocellular carcinoma risk

Hepatocellular carcinoma (HCC) is one of the most frequent types of tumors worldwide. Its occurrence and development have been related to various risk factors, such as chronic infection with hepatitis B or C viruses and alcohol addiction. DNA repair systems play a critical role in maintaining the integrity of the genome. Defects in these systems have been related to increased susceptibility to various types of cancer. Multiple genetic polymorphisms in genes of DNA repair systems have been reported that may affect DNA repair capacity (DRC) and modulate risk to cancer. Several studies have been conducted to assess the role of polymorphisms of DNA repair genes on the HCC risk. Identifying these polymorphisms and their association with HCC risk may help to improve prevention and treatment strategies. In this study, we review investigations that evaluated the association between genetic polymorphisms of DNA repair genes and risk of HCC.

New perspectives in cancer biology from a study of canonical and non-canonical functions of base excision repair proteins with a focus on early steps

Alterations of DNA repair enzymes and consequential triggering of aberrant DNA damage response (DDR) pathways are thought to play a pivotal role in genomic instabilities associated with cancer development, and are further thought to be important predictive biomarkers for therapy using the synthetic lethality paradigm. However, novel unpredicted perspectives are emerging from the identification of several non-canonical roles of DNA repair enzymes, particularly in gene expression regulation, by different molecular mechanisms, such as (i) non-coding RNA regulation of tumour suppressors, (ii) epigenetic and transcriptional regulation of genes involved in genotoxic responses and (iii) paracrine effects of secreted DNA repair enzymes triggering the cell senescence phenotype. The base excision repair (BER) pathway, canonically involved in the repair of non-distorting DNA lesions generated by oxidative stress, ionising radiation, alkylation damage and spontaneous or enzymatic deamination of nucleotide bases, represents a paradigm for the multifaceted roles of complex DDR in human cells. This review will focus on what is known about the canonical and non-canonical functions of BER enzymes related to cancer development, highlighting novel opportunities to understand the biology of cancer and representing future perspectives for designing new anticancer strategies. We will specifically focus on APE1 as an example of a pleiotropic and multifunctional BER protein.

Association Between Arg72Pro Polymorphism in TP53 and Malignant Abdominal Solid Tumor Risk in Hunan Children

Pediatric solid tumors are heterogeneous and comprise various histological subtypes. TP53, a tumor suppressor, orchestrates the transcriptional activation of anti-cancer genes. The gene coding for this protein is highly polymorphic, and its mutations are associated with cancer development. The Arg72Pro polymorphism in TP53 has been associated with susceptibility to various types of cancer. Here, in this hospital-based study, we evaluated the association of this polymorphism with susceptibility toward malignant abdominal solid tumors in children in the Hunan province of China. We enrolled 162 patients with neuroblastoma, 60 patients with Wilms' tumor, and 28 patients with hepatoblastoma as well as 270 controls. Genotypes were determined using a TaqMan assay, and the strength of the association was assessed using an odds ratio, within a 95% confidence interval identified using logistic regression models. Our results showed that the Arg72Pro polymorphism did not exhibit significant association with susceptibility toward pediatric malignant abdominal solid tumors. Stratification analysis revealed that this polymorphism exerts weak sex- and age-specific effects on Wilms' tumor and hepatoblastoma susceptibility, respectively. Overall, our results indicate that the Arg72Pro polymorphism may have a marginal effect on susceptibility toward pediatric malignant abdominal solid tumors in Hunan, and this finding warrants further confirmation.

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.

The Base Excision Repair Pathway in the Nematode Caenorhabditis elegans

Exogenous and endogenous damage to the DNA is inevitable. Several DNA repair pathways including base excision, nucleotide excision, mismatch, homologous and non-homologous recombinations are conserved across all organisms to faithfully maintain the integrity of the genome. The base excision repair (BER) pathway functions to repair single-base DNA lesions and during the process creates the premutagenic apurinic/apyrimidinic (AP) sites. In this review, we discuss the components of the BER pathway in the nematode Caenorhabditis elegans and delineate the different phenotypes caused by the deletion or the knockdown of the respective DNA repair gene, as well as the implications. To date, two DNA glycosylases have been identified in C. elegans, the monofunctional uracil DNA glycosylase-1 (UNG-1) and the bifunctional endonuclease III-1 (NTH-1) with associated AP lyase activity. In addition, the animal possesses two AP endonucleases belonging to the exonuclease-3 and endonuclease IV families and in C. elegans these enzymes are called EXO-3 and APN-1, respectively. In mammalian cells, the DNA polymerase, Pol beta, that is required to reinsert the correct bases for DNA repair synthesis is not found in the genome of C. elegans and the evidence indicates that this role could be substituted by DNA polymerase theta (POLQ), which is known to perform a function in the microhomology-mediated end-joining pathway in human cells. The phenotypes observed by the C. elegans mutant strains of the BER pathway raised many challenging questions including the possibility that the DNA glycosylases may have broader functional roles, as discuss in this review.

Sorafenib Resistance in Hepatocellular Carcinoma: The Relevance of Genetic Heterogeneity

Despite advances in biomedicine, the incidence and the mortality of hepatocellular carcinoma (HCC) remain high. The majority of HCC cases are diagnosed in later stages leading to the less than optimal outcome of the treatments. Molecular targeted therapy with sorafenib, a dual-target inhibitor targeting the serine-threonine kinase Raf and the tyrosine kinases VEGFR/PDGFR, is at present the main treatment for advanced-stage HCC, either in a single or combinatory regimen. However, it was observed in a large number of patients that its effectiveness is hampered by drug resistance. HCC is highly heterogeneous, within the tumor and among individuals, and this influences disease progression, classification, prognosis, and naturally cellular susceptibility to drug resistance. This review aims to provide an insight on how HCC heterogeneity influences the different primary mechanisms of chemoresistance against sorafenib including reduced drug intake, enhanced drug efflux, intracellular drug metabolism, alteration of molecular targets, activation/inactivation of signaling pathways, changes in the DNA repair machinery, and negative balance between apoptosis and survival of the cancer cells. The diverse variants, mutations, and polymorphisms in molecules and their association with drug response can be a helpful tool in treatment decision making. Accordingly, the existence of heterogeneous biomarkers in the tumor must be considered to strengthen multi-target strategies in patient-tailored treatment.

Ras-Mediated Activation of NF-κB and DNA Damage Response in Carcinogenesis

Cancer is a multi-step process during which cells acquire mutations that eventually lead to uncontrolled cell growth and division and evasion of programmed cell death. The oncogenes such as Ras and c-Myc may be responsible in all three major stages of cancer i.e., early, intermediate, and late. The NF-κB has been shown to control the expression of genes linked with tumor pathways such as chronic inflammation, tumor cell survival, anti-apoptosis, proliferation, invasion, and angiogenesis. In the last few decades, various biomarker pathways have been identified that play a critical role in carcinogenesis such as Ras, NF-κB and DNA damage.

Visceral Fat Area, Not Subcutaneous Fat Area, is Associated with Cardiac Hemodynamics in Type 2 Diabetes

BACKGROUND

This study was conducted in patients with type 2 diabetes mellitus (T2DM) to assess the association between visceral fat area (VFA) and cardiac hemodynamics.

METHODS

A total of 568 patients with type 2 diabetes (mean age 54±12 years; 40.8% of women) were enrolled. Visceral fat area (VFA, m²) and subcutaneous fat area (SFA, m²) were evaluated by a bioelectrical impedance analyzer. Cardiac hemodynamics were measured by echocardiography, and other clinical and laboratory variables were also assessed and recorded. Patients were divided into those with VFA ≤ 100 (n=369) and those with VFA > 100 (n=199).

RESULTS

VFA, SFA, LVMI (left ventricular mass index), left atrial diameter, left ventricular diastolic diameter (LvDd), interventricular septal thickness (IVST), left ventricular systolic diameter (LvSd), and posterior wall thickness (PWT) levels in high-V groups were significantly higher than those in low-V groups. Correlation analysis showed that VFA was positively correlated with LVMI (r=0.120, p=0.004), LVM (r=0.249, p<0.0001), left atrial diameter (r=0.375, p<0.0001), aortic root diameter (r=0.243, p<0.0001), left ventricular systolic diameter (LvSd) (r=0.211, p<0.0001) and negatively correlated with LVEF (r=-0.107, p=0.011). In multivariate linear regression analysis, VFA was the strongest independent determinant of LVMI (β=0.04, p=0.016), LVEF (β=-0.01, p=0.023), and left atrial diameter (β=0.035, p<0.0001), Internal diameter of the aortic root (β=0.014, p<0.0001) and LvSd (β=0.017, p<0.0001). In addition, the VFA also better predicted cardiovascular disease risk with AUC of 0.609 (95% CI:0.563-0.656), compared with SFA, waist-hip ratio (WHR), in a statistically significant manner.

CONCLUSION

We found a significant correlation between VFA (but not SFA) and cardiac hemodynamic parameters. The VFA has advantages as a predictor of visceral obesity and is significantly associated with the development of cardiovascular risk factors (CVD) in T2DM patients.

Inhibition of APE1-endonuclease activity affects cell metabolism in colon cancer cells via a p53-dependent pathway

The pathogenesis of colorectal cancer (CRC) involves different mechanisms, such as genomic and microsatellite instabilities. Recently, a contribution of the base excision repair (BER) pathway in CRC pathology has been emerged. In this context, the involvement of APE1 in the BER pathway and in the transcriptional regulation of genes implicated in tumor progression strongly correlates with chemoresistance in CRC and in more aggressive cancers. In addition, the APE1 interactome is emerging as an important player in tumor progression, as demonstrated by its interaction with Nucleophosmin (NPM1). For these reasons, APE1 is becoming a promising target in cancer therapy and a powerful prognostic and predictive factor in several cancer types. Thus, specific APE1 inhibitors have been developed targeting: i) the endonuclease activity; ii) the redox function and iii) the APE1-NPM1 interaction. Furthermore, mutated p53 is a common feature of advanced CRC. The relationship between APE1 inhibition and p53 is still completely unknown. Here, we demonstrated that the inhibition of the endonuclease activity of APE1 triggers p53-mediated effects on cell metabolism in HCT-116 colon cancer cell line. In particular, the inhibition of the endonuclease activity, but not of the redox function or of the interaction with NPM1, promotes p53 activation in parallel to sensitization of p53-expressing HCT-116 cell line to genotoxic treatment. Moreover, the endonuclease inhibitor affects mitochondrial activity in a p53-dependent manner. Finally, we demonstrated that 3D organoids derived from CRC patients are susceptible to APE1-endonuclease inhibition in a p53-status correlated manner, recapitulating data obtained with HCT-116 isogenic cell lines. These findings suggest the importance of further studies aimed at testing the possibility to target the endonuclease activity of APE1 in CRC.

Urinary 8-hydroxydeoxyguanosine in relation to XRCC1 rs25487 G/A (Arg399Gln) and OGG1 rs1052133 C/G (Ser326Cys) DNA repair genes polymorphisms in patients with chronic hepatitis C and related hepatocellular carcinoma

Background and aim: DNA repair represents a protective mechanism against cell injury and cancer. 8-hydroxy-deoxyguanosine (8-OHdG) is the main ROS-induced DNA mutation. The current study aimed to evaluate urinary 8-OHdG levels in patients with chronic hepatitis C virus (HCV) and its related hepatocellular (HCC) and correlate its level to XRCC1 rs25487 G/A and OGG1 rs1052133 C/G gene polymorphisms.

Materials and methods: Urinary 8-OHdG assays were performed using HPLC technique, and XRCC1 rs25487 G/A and OGG1 rs1052133 C/G gene polymorphisms were analyzed by PCR using confronting two-pair primer method (PCR-CTPP) in 200 subjects allocated into 50 chronic HCV patients, 50 HCV-related HCC patients, and 100 controls.

Results: There were significantly increased urinary 8-OHdG levels in HCV-related HCC and chronic HCV patients when compared with the controls (P<0.05 for all). Urinary 8-OHdG was associated with the tumor spread. Regarding, XRCC1 (Arg399Gln), AA (Gln/Gln) genotype and A-allele were more frequent in HCC and chronic HCV patients than in the controls (P<0.05). ORs (95%CI) using the dominant and the recessive genetic models were; 2.1 (1.1–4.1), P=0.032 and 1.9 (1–3.6), P=0.043 respectively. For OGG1 (Ser326Cys), GG (Cys/Cys) genotype and G-allele were increased significantly in chronic HCV and HCC patients compared to the controls (P<0.05). ORs (95%CI) under the dominant and the recessive genetic models were; 2.1 (1.1–4.1), P=0.032 and 1.9 (1–3.8), P=0.049 respectively. Additionally, XRCC1 (AA) and OGG1 (GG) genotypes had significantly increased urinary 8-OHdG levels among patients (P<0.05).

Conclusions: XRCC1 (AA) and OGG1 (GG) could be considered as possible genotypic risk factors for HCV- related HCC development which were associated with significantly high urinary 8-hydroxy-deoxyguanosine levels, thus urinary 8-OHdG could be considered as non-invasive marker in follow-up chronic HCV progression into HCC.