Expression of Ku70 and Ku80 mediated by NF-kappa B and cyclooxygenase-2 is related to proliferation of human gastric cancer cells

CircJPH1 regulates the NF-κB/HERC5 axis to promote the malignant progression of esophageal squamous cell carcinoma through binding to XRCC6

Esophageal squamous cell carcinoma (ESCC) is a prevalent and malignant cancer with an unknown pathogenesis and a poor prognosis; therefore, the identification of effective biomarkers and targets is crucial for its diagnosis and treatment. Circular (circ)RNAs are prominent functional biomarkers and therapeutic targets in various diseases, particularly cancer, due to their widespread expression and regulatory mechanisms. Our study aimed to investigate the therapeutic potential of circRNA for ESCC. We identified Hsa_circ_0137111 for the first time as one of the most significantly up-regulated genes in ESCC sequencing and named it circJPH1. The results of the present study demonstrated an enhanced expression of circJPH1 in ESCC tissues. Moreover, circJPH1-knockdown could significantly inhibit the proliferation, migration, and invasion of ESCC cells, while its overexpression promoted these characteristics. In addition, circJPH1 promoted ESCC cell tumor growth in vivo. For the first time, mass spectrometry and RNA pull-down analysis revealed the interaction of X-ray repair cross-complementary 6 (XRCC6) protein with circJPH1, thereby promoting its nuclear translocation. Consequently, the nuclear factor kappa-B (NF-κB) signaling pathway was activated, leading to an up-regulation of HECT and RLD domain containing E3 ubiquitin protein ligase 5 (HERC5), thereby promoting ESCC progression. In summary, the present study elucidated the regulatory impact of circJPH1 on ESCC progression in vitro and in vivo, thereby indicating its potential role in ESCC treatment.

Noncanonical functions of Ku may underlie essentiality in human cells

The Ku70/80 heterodimer is a key player in non-homologous end-joining DNA repair but is involved in other cellular functions like telomere regulation and maintenance, in which Ku's role is not fully characterized. It was previously reported that knockout of Ku80 in a human cell line results in lethality, but the underlying cause of Ku essentiality in human cells has yet to be fully explored. Here, we established conditional Ku70 knockout cells using CRISPR/Cas9 editing to study the essentiality of Ku70 function. While we observed loss of cell viability upon Ku depletion, we did not detect significant changes in telomere length, nor did we record lethal levels of DNA damage upon loss of Ku. Analysis of global proteome changes following Ku70 depletion revealed dysregulations of several cellular pathways including cell cycle/mitosis, RNA related processes, and translation/ribosome biogenesis. Our study suggests that the driving cause of loss of cell viability in Ku70 knockouts is not linked to the functions of Ku in DNA repair or at telomeres. Moreover, our data shows that loss of Ku affects multiple cellular processes and pathways and suggests that Ku plays critical roles in cellular processes beyond DNA repair and telomere maintenance to maintain cell viability.

Genotoxicity-Stimulated and CYLD-Driven Malignant Transformation

Oxidative stress, which can cause DNA damage, can both activate TNF-R1 directly in the absence of TNF stimulation and phosphorylate c-Abl, thus promoting its cytoplasmic translocation. Persistent cytoplasmic localization of c-Abl has been associated with cellular transformation. c-Abl phosphorylates OTULIN at tyrosine 56, thereby disrupting its relationship with LUBAC. OTULIN-released LUBAC interacts with SPATA2 and is recruited to the TNF-R1sc, facilitating SPATA2-CYLD interaction. All these interactions are required for the activation of IKKβ to stimulate NF-κB transcriptional activity following genotoxic stress. IKKβ also induces the critical phosphorylation of CYLD at serine 568 to increase its deubiquitinating (DUB) activity required for the termination of signaling cascades. Contrary to the widespread belief that CYLD is an absolute tumor suppressor, CYLD initiates and terminates NF-κB activity by alternately using its oncoprotein and tumor suppressor activities, respectively. If IKKβ fails to achieve the DUB activity-inducing phosphorylation at serine 568, CYLD would operate in a sustained mode of oncogenic activity. The resulting dysregulated NF-κB activation and other accompanying pathologies will disrupt cellular homeostasis in favor of transformation.

NF-κB in Gastric Cancer Development and Therapy

Gastric cancer is considered one of the most common causes of cancer-related death worldwide and, thus, a major health problem. A variety of environmental factors including physical and chemical noxae, as well as pathogen infections could contribute to the development of gastric cancer. The transcription factor nuclear factor kappa B (NF-κB) and its dysregulation has a major impact on gastric carcinogenesis due to the regulation of cytokines/chemokines, growth factors, anti-apoptotic factors, cell cycle regulators, and metalloproteinases. Changes in NF-κB signaling are directed by genetic alterations in the transcription factors themselves, but also in NF-κB signaling molecules. NF-κB actively participates in the crosstalk of the cells in the tumor micromilieu with divergent effects on the heterogeneous tumor cell and immune cell populations. Thus, the benefits/consequences of therapeutic targeting of NF-κB have to be carefully evaluated. In this review, we address recent knowledge about the mechanisms and consequences of NF-κB dysregulation in gastric cancer development and therapy.

Pharmacological methods to transcriptionally modulate double-strand break DNA repair

There is much interest in targeting DNA repair pathways for use in cancer therapy, as the effectiveness of many therapeutic agents relies on their ability to cause damage to DNA, and deficiencies in DSB repair pathways can make cells more sensitive to specific cancer therapies. For example, defects in the double-strand break (DSB) pathways, non-homologous end joining (NHEJ) and homology-directed repair (HDR), induce sensitivity to radiation therapy and poly(ADP)-ribose polymerase (PARP) inhibitors, respectively. However, traditional approaches to inhibit DNA repair through small molecule inhibitors have often been limited by toxicity and poor bioavailability. This review identifies several pharmacologic manipulations that modulate DSB repair by reducing expression of DNA repair factors. A number of pathways have been identified that modulate activity of NHEJ and HDR through this mechanism, including growth and hormonal receptor signaling pathways as well as epigenetic modifiers. We also discuss the effects of anti-angiogenic therapy on DSB repair. Preclinically, these pharmacological manipulations of DNA repair factor expression have been shown to increase sensitivity to specific cancer therapies, including ionizing radiation and PARP inhibitors. When applicable, relevant clinical trials are discussed and areas for future study are identified.

Ku80 gene knockdown by the CRISPR/Cas9 technique affects the biological functions of human thyroid carcinoma cells

In the present study, to evaluate the role of Ku80 in thyroid carcinoma (TC), 86 thyroid tissue samples from patients with a spectrum of thyroid disorders were examined for protein levels of Ku80, nuclear factor-κB (NF-κB) and RET/TC by immunohistochemistry. Furthermore, in TC cells, Ku80 mRNA was detected by reverse transcription-quantitative PCR analysis and silenced using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technique to assess its role. An antibody array was used to identify Ku80-related regulatory genes. The protein levels of Ku80 in the TC tissues were significantly higher than those in non-neoplastic adjacent tissue samples (P<0.01). The activation of NF-kB and expression of RET/TC in the TC group were significantly increased (P<0.05) and were correlated with the protein expression of Ku80 (P<0.05). In papillary TC cells, the mRNA levels of Ku80 were high; Ku80 knockdown resulted in reductions in proliferation, invasion and colony formation, increased apoptosis, and reduced levels of proteins involved in MAPK signaling, cell proliferation and apoptosis. The high expression of Ku80 in TC was found to be associated with the expression of RET/TC and activation of NF-κB, and Ku80 knockdown decreased the malignancy of TC cells.

Association between selenium, cadmium, and arsenic levels and genetic polymorphisms in DNA repair genes (XRCC5, XRCC6) in gastric cancerous and non-cancerous tissue

Gastric cancer is one of the most prevalent cancers in northern Iran. The DNA repair genes X-ray repair cross-complementing (XRCC) group 5, XRCC6, which are important members of non-homologous end-joining repair system, play an important role in repairing the DNA double-strand breaks. Chronic exposure to heavy metals has long been recognized as being capable of augmenting gastric cancer incidence among exposed human populations. Since trace elements could directly or indirectly damage DNA, and polymorphism in DNA DSBs-repair genes can alter the capacity of system repair, we assumed that XRCC5 VNTR and XRCC6-61C >G polymorphism also impress the DSBs-repair system ability and contribute to gastric cancer. Therefore, the objective of this research was to evaluate the tissue accumulation of Selenium (Se), Cadmium (Cd) and Arsenic (As), and XRCC5 VNTR, XRCC6-61C >G polymorphisms in cancerous and non-cancerous tissues in Golestan province. The study population included 46 gastric cancer patients and 43 cancer-free controls. Two polymorphisms of XRCC5, XRCC6 were genotyped using polymerase chain reaction (PCR) or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Further employed was atomic absorption spectroscopy so as to determine the levels of Se, Cd and As. Finally, the data were analyzed by SPSS (version 16) statistical software. The Se level was significantly higher in tumors as compared to non-tumor tissues, but there was no significant correlation between As and Cd in cancerous and noncancerous tissues. Allele frequencies of the selected genes were not statistically different between groups regarding XRCC6 (-61C>G). XRCC5 0R/0R, 0R/1R, 1R/1R, and 0R/2R genotypes were more common in cancerous group. High levels of Se in cancerous tissues vs. non-cancerous tissues may be one of the carcinogenic factors; in Golestan province, unlike other regions of Iran and the world, the level of Se is high, hence the higher risks of gastric cancer.

Ku80 promotes melanoma growth and regulates antitumor effect of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway

Melanoma is one of the most malignant and aggressive cancers with high cancer-related deaths. However, it is unclear whether Ku80 regulates tumor growth in human melanoma. In this study, we screened a siRNA library targeting 6024 human genes and identified Ku80 as a potential therapeutic target in melanoma cells. Knockdown of Ku80 significantly suppressed melanoma cell proliferation and induced apoptosis, as well as enhanced the antitumor effect of melatonin in melanoma in vitro and in vivo. Overexpression of Ku80, however, promoted melanoma growth and increased the insensitivity of melanoma cells to melatonin. Mechanistically, we found that Ku80 bound to the PDK1 promoter and activated the transcription of PDK1. Moreover, we showed that the binding of Ku80 at the PDK-1 promoter was HIF1-α dependent, and melatonin degraded HIF1-α in melanoma cells. Furthermore, clinical data revealed that the expression of Ku80 and PDK-1 proteins were positively correlated and elevated in the tumor tissues of melanoma patients, and high expression of Ku80 predicted a poor prognosis in melanoma. Collectively, our study demonstrated that Ku80 promoted melanoma growth and regulated antitumor activity of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway, suggesting that Ku80 may be a potential molecular target for melanoma treatment.

The roles of homologous recombination and the immune system in the genomic evolution of cancer

A variety of factors, whether extracellular (mutagens/carcinogens and viruses in the environment, chronic inflammation and radiation associated with the environment and/or electronic devices/machines) and/or intracellular (oxidative metabolites of food, oxidative stress due to inflammation, acid production, replication stress, DNA replication/repair errors, and certain hormones, cytokines, growth factors), pose a constant threat to the genomic integrity of a living cell. However, in the normal cellular environment multiple biological pathways including DNA repair, cell cycle, apoptosis and the immune system work in a precise, regulated (tightly controlled), timely and concerted manner to ensure genomic integrity, stability and proper functioning of a cell. If damage to DNA takes place, it is efficiently and accurately repaired by the DNA repair systems. Homologous recombination (HR) which utilizes either a homologous chromosome (in G1 phase) or a sister chromatid (in G2) as a template to repair the damage, is known to be the most precise repair system. HR in G2 which utilizes a sister chromatid as a template is also called an error free repair system. If DNA damage in a cell is so extensive that it overwhelms the repair system/s, the cell is eliminated by apoptosis. Thus, multiple pathways ensure that genome of a cell is intact and stable. However, constant exposure to DNA damage and/or dysregulation of DNA repair mechanism/s poses a risk of mutation and cancer. Oncogenesis, which seems to be a multistep process, is associated with acquisition of a number of genomic changes that enable a normal cell to progress from benign to malignant transformation. Transformed/cancer cells are recognized and killed by the immune system. However, the ongoing acquisition of new genomic changes enables cancer cells to survive/escape immune attack, evolve into a more aggressive phenotype, and eventually develop resistance to therapy. Although DNA repair (especially the HR) and the immune system play unique roles in preserving genomic integrity of a cell, they can also contribute to DNA damage, genomic instability and oncogenesis. The purpose of this article is to highlight the roles of DNA repair (especially HR) and the immune system in genomic evolution, with special focus on gastrointestinal cancer.

Molecular Mechanisms of H. pylori-Induced DNA Double-Strand Breaks

Infections contribute to carcinogenesis through inflammation-related mechanisms. H. pylori infection is a significant risk factor for gastric carcinogenesis. However, the molecular mechanism by which H. pylori infection contributes to carcinogenesis has not been fully elucidated. H. pylori-associated chronic inflammation is linked to genomic instability via reactive oxygen and nitrogen species (RONS). In this article, we summarize the current knowledge of H. pylori-induced double strand breaks (DSBs). Furthermore, we provide mechanistic insight into how processing of oxidative DNA damage via base excision repair (BER) leads to DSBs. We review recent studies on how H. pylori infection triggers NF-κB/inducible NO synthase (iNOS) versus NF-κB/nucleotide excision repair (NER) axis-mediated DSBs to drive genomic instability. This review discusses current research findings that are related to mechanisms of DSBs and repair during H. pylori infection.

Clinical values of Ku80 upregulation in superficial esophageal squamous cell carcinoma

Ku80 is an important DNA repair protein. Here, this study sought to investigate clinical impacts of Ku80 expression for patients with superficial esophageal squamous cell carcinoma (ESCC). Immunohistochemical analysis of Ku80 expression was carried out in normal esophageal mucosa, squamous epithelial dysplasia, carcinoma in situ, and superficial ESCC. Its relationships with clinicopathological features and survival of superficial ESCC patients were further clarified. Lentivirus-mediated RNA interference was used to silence Ku80 gene in ECA109 and KYSE150 cells. Both quantitative real-time PCR and Western blot were employed to evaluate Ku80 levels. CCK-8 assay, clone formation assay, flow cytometry, and tumorigenesis experiment were performed to evaluate the malignant phenotype of ECA109 and KYSE150 cells. Increased Ku80 expression was observed in dysplastic esophageal mucosa and carcinoma in situ compared to normal esophageal mucosa (P < 0.001, P < 0.001). Ku80 expression was further increased in superficial ESCC in comparison with dysplastic esophageal mucosa and carcinoma in situ (P < 0.001, P = 0.034). In superficial ESCC, Ku80 overexpression was related to tumor differentiation (P = 0.017), T status (P = 0.011), nodal involvement (P = 0.005), TNM stage (P = 0.004), and postoperative recurrence (P = 0.008). Cox proportional hazards regression showed tumor differentiation, T status, nodal involvement, TNM stage, and Ku80 expression were both independent predictors of patients' overall survival and disease-free survival. Ku80 shRNA effectively reduced Ku80 expression, which significantly inhibited proliferation, clone formation, and induced apoptosis in ECA109 and KYSE150 cells. The tumor growth of xenografts was significantly reduced by Ku80 silencing in ECA109 and KYSE150 cells. Ku80 overexpression associates with unfavorable prognosis of superficial ESCC patients, and silencing of Ku80 could inhibit the malignant behavior of ESCC cells. We provide evidence that Ku80 has unrecognized roles in carcinogenesis and development of ESCC.

Downregulation of Sp1 by Minnelide leads to decrease in HSP70 and decrease in tumor burden of gastric cancer

BACKGROUND

Gastric cancer is the third leading cause of cancer related mortality worldwide with poor survival rates. Even though a number of chemotherapeutic compounds have been used against this disease, stomach cancer has not been particularly sensitive to these drugs. In this study we have evaluated the effect of triptolide, a naturally derived diterpene triepoxide and its water soluble pro-drug Minnelide on several gastric adenocarcinoma cell lines both as monotherapy and in combination with CPT-11.

METHODS

Gastric cancer cell lines MKN28 and MKN45 were treated with varying doses of triptolide in vitro. Cell viability was measured using MTT based assay kit. Apoptotic cell death was assayed by measuring caspase activity. Effect of the triptolide pro-drug, Minnelide, was evaluated by implanting the gastric cancer cells subcutaneously in athymic nude mice.

RESULTS

Gastric cancer cell lines MKN28 and MKN45 cells exhibited decreased cell viability and increased apoptosis when treated with varying doses of triptolide in vitro. When implanted in athymic nude mice, treatment with Minnelide reduced tumor burden in both MKN28 derived tumors as well as MKN45 derived tumors. Additionally, we also evaluated Minnelide as a single agent and in combination with CPT-11 in the NCI-N87 human gastric tumor xenograft model.

CONCLUSION

Our results indicated that the combination of Minnelide with CPT-11 resulted in significantly smaller tumors compared to control. These studies are extremely encouraging as Minnelide is currently undergoing phase 1 clinical trials for gastrointestinal cancers.

Ku70 inhibits gemcitabine-induced DNA damage and pancreatic cancer cell apoptosis

The current study focused on the role of Ku70, a DNA-dependent protein kinase (DNA-PK) complex protein, in pancreatic cancer cell resistance to gemcitabine. In both established cell lines (Mia-PaCa-2 and PANC-1) and primary human pancreatic cancer cells, shRNA/siRNA-mediated knockdown of Ku70 significantly sensitized gemcitabine-induced cell death and proliferation inhibition. Meanwhile, gemcitabine-induced DNA damage and subsequent pancreatic cancer cell apoptosis were also potentiated with Ku70 knockdown. On the other hand, exogenous overexpression of Ku70 in Mia-PaCa-2 cells suppressed gemcitabine-induced DNA damage and subsequent cell apoptosis. In a severe combined immune deficient (SCID) mice Mia-PaCa-2 xenograft model, gemcitabine-induced anti-tumor activity was remarkably pontificated when combined with Ku70 shRNA knockdown in the xenografts. The results of this preclinical study imply that Ku70 might be a primary resistance factor of gemcitabine, and Ku70 silence could significantly chemo-sensitize gemcitabine in pancreatic cancer cells.

Prolonged inflammatory microenvironment is crucial for pro-neoplastic growth and genome instability: a detailed review

INTRODUCTION

Chronic inflammation can affect the normal cell homeostasis and metabolism by rendering the cells susceptible to genomic instability that may lead to uncontrolled cellular growth and proliferation ensuing tumorigenesis. The causal agents for inflammation may be pathogenic infections like microbial agents ranging from viruses to bacteria. These infections lead to DNA damage or disruption of normal cell metabolism and alter the genome integrity.

FINDINGS

In this review, we have highlighted the role of recurrent infections in tumor microenvironment can lead to recruitment of pro-inflammatory cells, cytokines and growth factors to the site of inflammation. This makes the environment rich in cytokines, chemokines, DNA-damaging agents (ROS, RNS) and growth factors which activate DNA damage response pathway and help in sustained proliferation of the tumor cells. In any inflammatory response, the production of cytokines and related signaling molecules is self-regulating and limiting. But in case of neoplastic risk, deregulation of these factors may lead to abnormalities and related pathogenesis.

CONCLUSION

The scope of the present review is to explore the probable mechanistic link and factors responsible for chronic inflammation. The relation between chronic inflammation and DNA damage response was further elucidated to understand the mechanism by which it makes the cells susceptible to carcinogenesis.

High Expression of XRCC6 Promotes Human Osteosarcoma Cell Proliferation through the β-Catenin/Wnt Signaling Pathway and Is Associated with Poor Prognosis

Increasing evidences show that XRCC6 (X-ray repair complementing defective repair in Chinese hamster cells 6) was upregulated and involved in tumor growth in several tumor types. However, the correlation of XRCC6 and human osteosarcoma (OS) is still unknown. This study was conducted with the aim to reveal the expression and biological function of XRCC6 in OS and elucidate the potential mechanism. The mRNA expression level of XRCC6 was measured in osteosarcoma cells and OS samples by quantitative transcription-PCR (qRT-PCR). The expression of XRCC6 protein was measured using Western blot and immunohistochemical staining in osteosarcoma cell lines and patient samples. Cell Counting Kit 8 (CCK8), colony-forming and cell cycle assays were used to test cell survival capacity. We found that XRCC6 was overexpressed in OS cells and OS samples compared with the adjacent non-tumorous samples. High expression of XRCC6 was correlated with clinical stage and tumor size in OS. Reduced expression of XRCC6 inhibits OS cell proliferation through G2/M phase arrest. Most importantly, further experiments demonstrated that XRCC6 might regulate OS growth through the β-catenin/Wnt signaling pathway. In conclusion, these findings indicate that XRCC6 exerts tumor-promoting effects for OS through β-catenin/Wnt signaling pathway. XRCC6 may serve as a novel therapeutic target for OS patients.

Targeting RRM2 and Mutant BRAF Is a Novel Combinatorial Strategy for Melanoma

The majority of patients with melanoma harbor mutations in the BRAF oncogene, thus making it a clinically relevant target. However, response to mutant BRAF inhibitors (BRAFi) is relatively short-lived with progression-free survival of only 6 to 7 months. Previously, we reported high expression of ribonucleotide reductase M2 (RRM2), which is rate-limiting for de novo dNTP synthesis, as a poor prognostic factor in patients with mutant BRAF melanoma. In this study, the notion that targeting de novo dNTP synthesis through knockdown of RRM2 could prolong the response of melanoma cells to BRAFi was investigated. Knockdown of RRM2 in combination with the mutant BRAFi PLX4720 (an analog of the FDA-approved drug vemurafenib) inhibited melanoma cell proliferation to a greater extent than either treatment alone. This occurred in vitro in multiple mutant BRAF cell lines and in a novel patient-derived xenograft (PDX) model system. Mechanistically, the combination increased DNA damage accumulation, which correlated with a global decrease in DNA damage repair (DDR) gene expression and increased apoptotic markers. After discontinuing PLX4720 treatment, cells showed marked recurrence. However, knockdown of RRM2 attenuated this rebound growth both in vitro and in vivo, which correlated with maintenance of the senescence-associated cell-cycle arrest.

IMPLICATIONS

Inhibition of RRM2 converts the transient response of melanoma cells to BRAFi to a stable response and may be a novel combinatorial strategy to prolong therapeutic response of patients with melanoma. Mol Cancer Res; 14(9); 767-75. ©2016 AACR.

Accuracy of novel diagnostic biomarkers for hepatocellular carcinoma: An update for clinicians (Review)

Hepatocellular carcinoma (HCC) is the most common liver malignancy and a leading cause of cancer-related mortality worldwide. Accurate detection and differential diagnosis of early HCC can significantly improve patient survival. Currently, detection of HCC in clinical practice is performed by diagnostic imaging techniques and determination of serum biomarkers, most notably α-fetoprotein (AFP), fucosylated AFP and des-γ-carboxyprothrombin. However, these methods display limitations in sensitivity and specificity, especially with respect to early stages of HCC. Recently, high-throughput technologies have elucidated many new pathways involved in hepatocarcinogenesis and have led to the discovery of a plethora of novel, non-invasive serum biomarkers. In particular, the combination of AFP with these new candidate molecules has yielded promising results. In this review, we aimed at recapitulating the most recent (2013–2015) developments in HCC biomarker research. We compared promising novel diagnostic serum protein biomarkers, such as annexin A2, the soluble form of the receptor tyrosine kinase Axl and thioredoxin, as well as their combinations with AFP. High diagnostic performance (area under the curve >0.75) as shown by threshold-independent receiver operating characteristic curve analysis was a prerequisite for inclusion in this review. In addition, we discuss the role and potential of microRNAs in HCC diagnosis and associated methodological challenges.

Differences of Variable Number Tandem Repeats in XRCC5 Promoter Are Associated with Increased or Decreased Risk of Breast Cancer in BRCA Gene Mutation Carriers

Ku80 is a subunit of the Ku heterodimer that binds to DNA double-strand break ends as part of the non-homologous end joining (NHEJ) pathway. Ku80 is also involved in homologous recombination (HR) via its interaction with BRCA1. Ku80 is encoded by the XRCC5 gene that contains a variable number tandem repeat (VNTR) insertion in its promoter region. Different VNTR genotypes can alter XRCC5 expression and affect Ku80 production, thereby affecting NHEJ and HR pathways. VNTR polymorphism is associated with multiple types of sporadic cancer. In this study, we investigated its potential association with familial breast cancer at the germline level. Using PCR, PAGE, Sanger sequencing, and statistical analyses, we compared VNTR genotypes in the XRCC5 promoter between healthy individuals and three types of familial breast cancer cases: mutated BRCA1 (BRCA1⁺), mutated BRCA2 (BRCA2⁺), and wild-type BRCA1/BRCA2 (BRCAx). We observed significant differences of VNTR genotypes between control and BRCA1⁺ group (P < 0.0001) and BRCA2⁺ group (P = 0.0042) but not BRCAx group (P = 0.2185), and the differences were significant between control and cancer-affected BRCA1⁺ cases (P < 0.0001) and BRCA2⁺ cases (P = 0.0092) but not cancer-affected BRCAx cases (P = 0.4251). Further analysis indicated that 2R/2R (OR = 1.94, 95%CI = 1.26–2.95, P = 0.0096) and 2R/1R (OR = 1.58, 95%CI = 1.11–2.26, P = 0.0388) were associated with increased risk but 1R/1R (OR = 0.55, 95%CI = 0.35–0.84, P = 0.0196) and 1R/0R (OR = 0, 95%CI = 0–0.29, P = 0.0012) were associated with decreased risk in cancer-affected BRCA1⁺ group; 2R/1R (OR = 1.94, 95%CI = 1.14–3.32, P = 0.0242) was associated with increased risk in cancer-affected BRCA2⁺ group. No correlation was observed for the altered risk between cancer-affected or -unaffected carriers and between different age of cancer diagnosis in cancer-affected carriers. The frequently observed VNTR association with in BRCA1⁺ and BRCA2⁺ breast cancer group indicates that VNTR polymorphism in the XRCC5 promoter is associated with altered risk of breast cancer in BRCA1⁺ and BRCA2⁺ carriers.

Overexpression of Ku80 suggests poor prognosis of locally advanced esophageal squamous cell carcinoma patients

BACKGROUND

Recent studies have shown that Ku80 expression was implicated in development and progression of malignant tumors. In the present study, we analyzed for the first time the expression of Ku80 in locally advanced esophageal squamous cell carcinoma (ESCC) and its correlation with clinicopathologic features and patient survival.

METHODS

The expression profile of Ku80 was analyzed in 126 cases of locally advanced ESCC and 79 cases of normal subjects as control using immunohistochemistry and Western blot. The associations of Ku80 expression with clinicopathological features were estimated by χ (2) test. We further performed univariate and multivariate analyses to identify prognostic factors for overall survival (OS) of patients.

RESULTS

Immunohistochemistry and Western blot analyses both showed the Ku80 protein expression was significantly higher in ESCC than normal esophageal mucosa and corresponding healthy esophageal mucosa. Statistical analysis suggested a significant correlation of Ku80 overexpression with the tumor size (p = 0.037), differentiation degree (p = 0.018), depth of invasion (p = 0.020), lymph node metastasis (p = 0.045), clinicopathological staging (p = 0.001), and tumor recurrence (p = 0.011) in locally advanced ESCC patients. Moreover, overexpression of Ku80 was associated with reduced OS of patients after surgery (p = 0.001). Multivariate analysis with a Cox proportional hazards model further suggested that Ku80 expression was an independent prognostic indicator for patients' OS (p = 0.029).

CONCLUSIONS

Ku80 was a predictor of tumor's progression and prognosis of locally advanced ESCC patients. All of these results indicate that assessment of Ku80 level could improve stratification of locally advanced ESCC patients.

MCM3AP and POMP Mutations Cause a DNA-Repair and DNA-Damage-Signaling Defect in an Immunodeficient Child

Immunodeficiency patients with DNA repair defects exhibit radiosensitivity and proneness to leukemia/lymphoma formation. Though progress has been made in identifying the underlying mutations, in most patients the genetic basis is unknown. Two de novo mutated candidate genes, MCM3AP encoding germinal center-associated nuclear protein (GANP) and POMP encoding proteasome maturation protein (POMP), were identified by whole-exome sequencing (WES) and confirmed by Sanger sequencing in a child with complex phenotype displaying immunodeficiency, genomic instability, skin changes, and myelodysplasia. GANP was previously described to promote B-cell maturation by nuclear targeting of activation-induced cytidine deaminase (AID) and to control AID-dependent hyperrecombination. POMP is required for 20S proteasome assembly and, thus, for efficient NF-κB signaling. Patient-derived cells were characterized by impaired homologous recombination, moderate radio- and cross-linker sensitivity associated with accumulation of damage, impaired DNA damage-induced NF-κB signaling, and reduced nuclear AID levels. Complementation by wild-type (WT)-GANP normalized DNA repair and WT-POMP rescued defective NF-κB signaling. In conclusion, we identified for the first time mutations in MCM3AP and POMP in an immunodeficiency patient. These mutations lead to cooperative effects on DNA recombination and damage signaling. Digenic/polygenic mutations may constitute a novel genetic basis in immunodeficiency patients with DNA repair defects.

Overexpression of Ku80 correlates with aggressive clinicopathological features and adverse prognosis in esophageal squamous cell carcinoma

Ku80, a subunit of the heterodymeric Ku protein, is clearly implicated in nonhomologous end joining DNA repair, chemoresistance and radioresistance in malignant tumors. In the present study, the clinicopathological significance of Ku80 in esophageal squamous cell carcinoma (ESCC) was investigated. The expression levels of Ku80 were determined by reverse transcription-quantitative polymerase chain reaction and immunohistochemistry in ESCC specimens and normal esophageal mucosa. The mRNA and protein levels of Ku80 were significantly higher in ESCC tissues than in normal esophageal mucosa, and were significantly associated with tumor differentiation, local invasion, lymph node metastasis and tumor-node-metastasis (TNM) stage. However, overexpression of Ku80 mRNA and protein levels were not significantly correlated with age, gender, tumor site or tumor size. Cox proportional hazards regression model demonstrated that tumor local invasion, lymph node metastasis, TNM stage and Ku80 mRNA and protein levels were independent risk factors indicating the overall survival of patients with ESCC. The present study demonstrated that aberrant Ku80 overexpression is observed in ESCC. In addition, high expression levels of Ku80 are associated with adverse clinicopathological features and unfavorable prognosis in ESCC patients.

Prognostic significance of Ku80 in pT2N0M0 esophageal squamous cell carcinoma after Ivor-Lewis esophagectomy

Recent studies have shown that Ku80, a DNA repair protein, was involved in progression of malignant tumors. This study aimed to clarify the clinicopathological significance and prognostic value of Ku80 in pT2N0M0 esophageal squamous cell carcinoma (ESCC). We enrolled 217 patients with pT2N0M0 midthoracic ESCC who had undergone Ivor-Lewis esophagectomy. The expression profile of Ku80 was examined by immunohistochemistry. The results were correlated with the clinicopathological variables, overall survival (OS) and disease-free survival (DFS), in pT2N0M0 ESCC patients. The expression of Ku80 were higher in ESCC tissues than the corresponding health esophageal mucosa (P < 0.001). Clinically, the Ku80 expression levels were significantly related to tumor size (P = 0.018), differentiation degree (P = 0.010), and tumor-node-metastasis (TNM) stage (P = 0.001). Subsequent multivariate analysis demonstrated that tumor size, differentiation degree, TNM stage, and Ku80 expression were independent prognostic factors for the OS and the DFS of pT2N0M0 ESCC patients. Our data indicated that Ku80 expression level associates with key clinicopathological features and is an independent predictor of the OS and the DFS in pT2N0M0 ESCC patients.

The DNA damage response and immune signaling alliance: Is it good or bad? Nature decides when and where

The characteristic feature of healthy living organisms is the preservation of homeostasis. Compelling evidence highlight that the DNA damage response and repair (DDR/R) and immune response (ImmR) signaling networks work together favoring the harmonized function of (multi)cellular organisms. DNA and RNA viruses activate the DDR/R machinery in the host cells both directly and indirectly. Activation of DDR/R in turn favors the immunogenicity of the incipient cell. Hence, stimulation of DDR/R by exogenous or endogenous insults triggers innate and adaptive ImmR. The immunogenic properties of ionizing radiation, a prototypic DDR/R inducer, serve as suitable examples of how DDR/R stimulation alerts host immunity. Thus, critical cellular danger signals stimulate defense at the systemic level and vice versa. Disruption of DDR/R-ImmR cross talk compromises (multi)cellular integrity, leading to cell-cycle-related and immune defects. The emerging DDR/R-ImmR concept opens up a new avenue of therapeutic options, recalling the Hippocrates quote "everything in excess is opposed by nature."

Susceptibility to gastric cancer and polymorphisms of insertion/deletion at the intron 3 of the XRCC4 and VNTR at the promoter region of the XRCC5

The genes encoding X-ray repair cross-complementing group 4 (XRCC4; OMIM: 194363) and 5 (XRCC5; OMIM: 194364) are involved in repair of DNA double-strand breaks. To investigating the associations between polymorphisms of Insertion/Deletion (I/D, rs28360071) in the intron 3 of the XRCC4 and VNTR in the promoter region of the XRCC5 and risk of gastric cancer, the present study was carried out. We included 159 (56 females, 103 males) with gastric cancer and 242 (75 females, 167 males) healthy blood donors frequency matched for age and gender. Using PCR-based methods, the genotypes of the study polymorphisms were determined. The alleles of VNTR XRCC5 polymorphism divided into two groups: L (0 and 1 repeats) and H (2 and 3 repeats) alleles. For the I/D XRCC4 polymorphism, after stratification of the subjects according to their family history (FH) of cancer, either the ID (OR = 3.19, 95%CI: 1.35-7.50, P = 0.008) or the DD genotypes (OR = 4.62, 95%CI: 1.63-13.0, P = 0.004) among positive FH persons, increased the risk of gastric cancer compared with the reference group (persons who have negative FH and II genotype). For the VNTR XRCC5 polymorphism, the LH + HH genotypes among positive FH persons, increased the risk of gastric cancer compared with the reference group (persons who have negative FH and LL genotype) (OR = 2.88, 95%CI: 1.34-6.18, P = 0.006). Sensitivity analysis showed that the above mentioned associations were not occurred due to the maldistribution of the genotypes among missing data. The present study suggests that both polymorphisms of the XRCC4 and XRCC5 might be risk factors for gastric cancer development especially among persons with positive FH.

Molecular changes in endometriosis-associated ovarian clear cell carcinoma

BACKGROUND

Endometriosis is frequently associated with and thought of having propensity to develop into ovarian clear cell carcinoma (OCCC), although the molecular transformation mechanism is not completely understood.

METHODS

We employed immunohistochemical (IHC) staining for marker expression along the potential progression continuum. Expression profiling of microdissected endometriotic and OCCC cells from patient-matched formalin-fixed, paraffin-embedded samples was performed to explore the carcinogenic pathways. Function of novel biomarkers was confirmed by knockdown experiments.

RESULTS

PTEN was significantly lost in both endometriosis and invasive tumour tissues, while oestrogen receptor (ER) expression was lost in OCCC relative to endometriosis. XRCC5, PTCH2, eEF1A2 and PPP1R14B were significantly overexpressed in OCCC and associated endometriosis, but not in benign endometriosis (p ⩽ 0.004). Knockdown experiments with XRCC5 and PTCH2 in a clear cell cancer cell line resulted in significant growth inhibition. There was also significant silencing of a panel of target genes with histone H3 lysine 27 trimethylation, a signature of polycomb chromatin-remodelling complex in OCCC. IHC confirmed the loss of expression of one such polycomb target gene, the serous ovarian cancer lineage marker Wilms' tumour protein 1 (WT1) in OCCC, while endometriotic tissues showed significant co-expression of WT1 and ER.

CONCLUSIONS

Loss of PTEN expression is proposed as an early and permissive event in endometriosis development, while the loss of ER and polycomb-mediated transcriptional reprogramming for pluripotency may play an important role in the ultimate transformation process. Our study provides new evidence to redefine the pathogenic programme for lineage-specific transformation of endometriosis to OCCC.

Postoperative Radiotherapy Improves Survival in Stage pT2N0M0 Esophageal Squamous Cell Carcinoma with High Risk of Poor Prognosis

PURPOSE

Clinically, some patients with stage pT2N0M0 esophageal squamous cell carcinoma (ESCC) might have poor survival outcomes after Ivor-Lewis esophagectomy. We explored whether adjuvant radiotherapy could improve the prognosis for the patients with high risk of poor clinical outcomes.

METHODS

We screened 326 pT2N0M0 ESCC patients who had complete resection with Ivor-Lewis esophagectomy. The expression profile of Ku80 was examined by immunohistochemistry and validated by Western blotting. Patients with high expression of Ku80 were divided randomly into the adjuvant radiotherapy group and control group. Patients with low expression of Ku80 were enrolled into the negative group. The overall survival (OS) and disease-free survival (DFS) was determined by Kaplan-Meier and log-rank analysis.

RESULTS

According to receiver operating characteristics curve analysis of Ku80 expression, 124 patients were enrolled into the negative group, 106 patients into the radiotherapy group, and 106 patients into the control group. Log-rank analysis showed that patients in the control group had worse OS and DFS than those in the negative group (P < 0.001, P < 0.001). There is no difference in OS and DFS of patients between radiotherapy group and negative group (P = 0.166, P = 0.648). Patients in the radiotherapy group had significantly better OS and DFS than those in the control group (P = 0.007, P < 0.001). Multivariate analysis further suggested that adjuvant radiotherapy was an independent prognostic indicator for patients with Ku80 overexpression.

CONCLUSIONS

In stage pT2N0M0 ESCC, Ku80 can be exploited as a predictor to identify patients with high risk of poor prognosis. Adjuvant radiotherapy could significantly improve survival for the patients with Ku80 overexpression.

β-Carotene-induced apoptosis is mediated with loss of Ku proteins in gastric cancer AGS cells

High dietary intakes and high blood levels of β-carotene are associated with a decreased incidence of various cancers. The anticancer effect of β-carotene is related to its pro-oxidant activity. DNA repair Ku proteins, as a heterodimer of Ku70 and Ku80, play a crucial role in DNA double-strand break repair. Reductions in Ku70/80 contribute to apoptosis. Previously, we showed that reactive oxygen species (ROS) activate caspase-3 which induces degradation of Ku proteins. In the present study, we investigated the mechanism of β-carotene-induced apoptosis of gastric cancer AGS cells by determining cell viability, DNA fragmentation, apoptotic indices (increases in cytochrome c and Bax, decrease in Bcl-2), ROS levels, mitochondrial membrane potential, caspase-3 activity, Ku70/80 levels, and Ku-DNA-binding activity of the cells treated with or without antioxidant N-acetyl cysteine and caspase-3 inhibitor z-DEVED-fmk. As a result, β-carotene induced apoptosis (decrease in cell viability, increases in DNA fragmentation and apoptotic indices) and caspase-3 activation, but decreased Ku70/80 levels and Ku-DNA-binding activity. β-Carotene-induced alterations (increase in caspase-3 activity, decrease in Ku proteins) and apoptosis were inhibited by N-acetyl cysteine and z-DEVED-fmk. Increment of intracellular and mitochondrial ROS levels and loss of mitochondrial membrane potential were suppressed by N-acetyl cysteine, but not by z-DEVED-fmk in β-carotene-treated cells. Therefore, β-carotene-induced increases in ROS and caspase-3 activity may lead to reduction of Ku70/80 levels, which results in apoptosis in gastric cancer cells. Loss of Ku proteins might be the underlying mechanism for β-carotene-induced apoptosis in gastric cancer cells.

NF-kB as a key player in regulation of cellular radiation responses and identification of radiation countermeasures

Nuclear factor (NF)-κB is a transcription factor that plays significant role in immunity, cellular survival and inhibition of apoptosis, through the induction of genetic networks. Depending on the stimulus and the cell type, the members of NF-κB related family (RelA, c-Rel, RelB, p50, and p52), forms different combinations of homo and hetero-dimers. The activated complexes (Es) translocate into the nucleus and bind to the 10bp κB site of promoter region of target genes in stimulus specific manner. In response to radiation, NF-κB is known to reduce cell death by promoting the expression of anti-apoptotic proteins and activation of cellular antioxidant defense system. Constitutive activation of NF-κB associated genes in tumour cells are known to enhance radiation resistance, whereas deletion in mice results in hypersensitivity to IR-induced GI damage. NF-κB is also known to regulate the production of a wide variety of cytokines and chemokines, which contribute in enhancing cell proliferation and tissue regeneration in various organs, such as the GI crypts stem cells, bone marrow etc., following exposure to IR. Several other cytokines are also known to exert potent pro-inflammatory effects that may contribute to the increase of tissue damage following exposure to ionizing radiation. Till date there are a series of molecules or group of compounds that have been evaluated for their radio-protective potential, and very few have reached clinical trials. The failure or less success of identified agents in humans could be due to their reduced radiation protection efficacy. In this review we have considered activation of NF-κB as a potential marker in screening of radiation countermeasure agents (RCAs) and cellular radiation responses. Moreover, we have also focused on associated mechanisms of activation of NF-κB signaling and their specified family member activation with respect to stimuli. Furthermore, we have categorized their regulated gene expressions and their function in radiation response or modulation. In addition, we have discussed some recently developed radiation countermeasures in relation to NF-κB activation

CDKN1A and FANCD2 are potential oncotargets in Burkitt lymphoma and multiple myeloma

Background

Comparative genetic and biological studies on malignant tumor counterparts in human beings and laboratory mice may be powerful gene discovery tools for blood cancers, including neoplasms of mature B-lymphocytes and plasma cells such as Burkitt lymphoma (BL) and multiple myeloma (MM).

Methods

We used EMSA to detect constitutive NF-κB/STAT3 activity in BL- and MM-like neoplasms that spontaneously developed in single-transgenic IL6 (interleukin-6) or MYC (c-Myc) mice, or in double-transgenic IL6MYC mice. qPCR measurements and analysis of clinical BL and MM datasets were employed to validate candidate NF-κB/STAT3 target genes.

Results

qPCR demonstrated that IL6- and/or MYC-dependent neoplasms in mice invariably contain elevated mRNA levels of the NF-κB target genes, Cdkn1a and Fancd2. Clinical studies on human CDKN1A, which encodes the cell cycle inhibitor and tumor suppressor p21, revealed that high p21 message predicts poor therapy response and survival in BL patients. Similarly, up-regulation of FANCD2, which encodes a key member of the Fanconi anemia and breast cancer pathway of DNA repair, was associated with poor outcome of patients with MM, particularly those with high-risk disease.

Conclusions

Our findings suggest that CDKN1A and FANCD2 are potential oncotargets in BL and MM, respectively. Additionally, the IL-6- and/or MYC-driven mouse models of human BL and MM used in this study may lend themselves to the biological validation of CDKN1A and FANCD2 as molecular targets for new approaches to cancer therapy and prevention.

Electronic supplementary material

The online version of this article (doi:10.1186/s40164-015-0005-2) contains supplementary material, which is available to authorized users.

Nuclear factor kappa B role in inflammation associated gastrointestinal malignancies

Nuclear factor kappa B (NF-κB) has an established role in the regulation of innate immunity and inflammation. NF-κB is also involved in critical mechanisms connecting inflammation and cancer development. Recent investigations suggest that the NF-κB signaling cascade may be the central mediator of gastrointestinal malignancies including esophageal, gastric and colorectal cancers. This review will explore NF-κB's function in inflammation-associated gastrointestinal malignancies, highlighting its oncogenic contribution to each step of carcinogenesis. NF-κB's role in the inflammation-to-carcinoma sequence in gastrointestinal malignancies warrants stronger emphasis upon targeting this pathway in achieving greater therapeutic efficacy.

NF-κB-dependent DNA damage-signaling differentially regulates DNA double-strand break repair mechanisms in immature and mature human hematopoietic cells

Hematopoietic stem and progenitor cells (HSPC), that is, the cell population giving rise not only to all mature hematopoietic lineages but also the presumed target for leukemic transformation, can transmit (adverse) genetic events, such as are acquired from chemotherapy or ionizing radiation. Data on the repair of DNA double-strand-breaks (DSB) and its accuracy in HSPC are scarce, in part contradictory, and mostly obtained in murine models. We explored the activity, quality and molecular components of DSB repair in human HSPC as compared with mature peripheral blood lymphocytes (PBL). To consider chemotherapy/radiation-induced compensatory proliferation, we established cycling HSPC cultures. Comparison of pathway-specific repair activities using reporter systems revealed that HSPC were severely compromised in non-homologous end joining and homologous recombination but not microhomology-mediated end joining. We observed a more pronounced radiation-induced accumulation of nuclear 53BP1 in HSPC relative to PBL, despite evidence for comparable DSB formation from cytogenetic analysis and γH2AX signal quantification, supporting differential pathway usage. Functional screening excluded a major influence of phosphatidylinositol-3-OH-kinase (ATM/ATR/DNA-PK)- and p53-signaling as well as chromatin remodeling. We identified diminished NF-κB signaling as the molecular component underlying the observed differences between HSPC and PBL, limiting the expression of DSB repair genes and bearing the risk of an inaccurate repair.

Mesencephalic astrocyte-derived neurotrophic factor is involved in inflammation by negatively regulating the NF-κB pathway

Inflammation can cause endoplasmic reticulum (ER) stress and therefore activates the unfolded protein response (UPR). ER stress and the consequent UPR have the potential to activate NF-κB. However, the factors mediating the crosstalk between ER stress and the NF-κB pathway remain unclear. Here, we determined that ER stress inducible protein Mesencephalic Astrocyte-derived Neurotrophic Factor (MANF) was up-regulated in autoimmune diseases and inflammatory disease models. Inflammation caused MANF to relocalize to the nuclei. MANF interacted with the DNA binding domain of p65 through its C-terminal SAP-like domain in the nuclei under the condition of inflammation or ER stress. MANF consequently inhibited p65-mediated transcriptional activation by interfering with the binding of p65 to its target genes promoters. Consistently, MANF suppressed the expressions of NF-κB-dependent target genes and the proliferation of inflammatory synoviocytes. These findings suggest that MANF may be a negative regulator of inflammation and mediate the crosstalk between the NF-κB pathway and ER stress.

Expression of Ku86 and presence of Ku86 antibody as biomarkers of hepatitis B virus related hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a common disease and the third leading cause of cancer-related deaths worldwide. Level of the 82-kDa ATP-dependent DNA helicase II (Ku86) increases in some tumors, but its clinical use as a marker for HCC is rare.

AIMS

To examine the relationship between increases in Ku86 and the development of hepatitis B virus (HBV)-related HCC to define the relationship between Ku86 and HCC.

METHODS

Expression of Ku86 in tumor tissue, para-tumor tissue, and normal tissue was examined by immunohistochemistry, and Ku86 antibody titers in patient serum collected pre- and post-operatively were measured by ELISA. Long-term survival of the patients was also monitored.

RESULTS

Ku86 staining in tumors was much stronger than in para-tumor and normal tissues. The expression of Ku86 was related to the tumor size, TNM stage, and tumor differentiation but not to gender, age, Child-Pugh score, tumor number, or α-fetoprotein levels. The long-term survival of patients with low Ku86 expression was longer. Patients with HCC had higher pre-operative Ku86 antibody levels. After surgical intervention, Ku86 antibody levels in patients with HCC declined significantly. Survival analysis showed that double-positive patients had the lowest survival rate, double-negative patients had the highest. Receiver operating characteristic curve analysis showed no significant difference between the AFP and Ku86 antibody. Multivariate analysis showed that Ku86 protein and Ku86 antibodies were independent prognostic factors of overall survival.

CONCLUSIONS

Ku86 and Ku86 antibodies are promising tumor markers for early detection and prognosis prediction of HBV-related HCC.

Cellular stress response and innate immune signaling: integrating pathways in host defense and inflammation

Extensive research in the past decade has identified innate immune recognition receptors and intracellular signaling pathways that culminate in inflammatory responses. Besides its role in cytoprotection, the importance of cell stress in inflammation and host defense against pathogens is emerging. Recent studies have shown that proteins in cellular stress responses, including the heat shock response, ER stress response, and DNA damage response, interact with and regulate signaling intermediates involved in the activation of innate and adaptive immune responses. The effect of such regulation by cell stress proteins may dictate the inflammatory profile of the immune response during infection and disease. In this review, we describe the regulation of innate immune cell activation by cell stress pathways, present detailed descriptions of the types of stress response proteins and their crosstalk with immune signaling intermediates that are essential in host defense, and illustrate the relevance of these interactions in diseases characteristic of aberrant immune responses, such as chronic inflammatory diseases, autoimmune disorders, and cancer. Understanding the crosstalk between cellular stress proteins and immune signaling may have translational implications for designing more effective regimens to treat immune disorders.

Transcriptional regulation of human DNA repair genes following genotoxic stress: trigger mechanisms, inducible responses and genotoxic adaptation

DNA repair is the first barrier in the defense against genotoxic stress. In recent years, mechanisms that recognize DNA damage and activate DNA repair functions through transcriptional upregulation and post-translational modification were the focus of intensive research. Most DNA repair pathways are complex, involving many proteins working in discrete consecutive steps. Therefore, their balanced expression is important for avoiding erroneous repair that might result from excessive base removal and DNA cleavage. Amelioration of DNA repair requires both a fine-tuned system of lesion recognition and transcription factors that regulate repair genes in a balanced way. Transcriptional upregulation of DNA repair genes by genotoxic stress is counteracted by DNA damage that blocks transcription. Therefore, induction of DNA repair resulting in an adaptive response is only visible through a narrow window of dose. Here, we review transcriptional regulation of DNA repair genes in normal and cancer cells and describe mechanisms of promoter activation following genotoxic exposures through environmental carcinogens and anticancer drugs. The data available to date indicate that 25 DNA repair genes are subject to regulation following genotoxic stress in rodent and human cells, but for only a few of them, the data are solid as to the mechanism, homeostatic regulation and involvement in an adaptive response to genotoxic stress.

Piperlongumine inhibits LMP1/MYC-dependent mouse B-lymphoma cells

Piperlongumine (PL), isolated from the fruit of Long pepper, Piper longum, is a cancer-inhibiting compound that selectively kills tumor cells while sparing their normal counterparts. Here we evaluated the efficacy with which PL suppresses malignant B cells derived from a newly developed, double-transgenic mouse model of human endemic Burkitt lymphoma (BL), designated mCD40-LMP1/iMyc(Eμ). PL inhibited tumor cell proliferation in a concentration-dependent manner and induced apoptosis of neoplastic but not normal B cells. Treatment with PL resulted in downregulation of EBV-encoded LMP1, cellular Myc, constitutive NF-κB activity, and a host of LMP1-Myc-NF-κB-regulated target genes including Aurka, Bcat1, Bub1b, Ccnb1, Chek1, Fancd2, Tfrc and Xrcc6. Of note, p21(Cip1)-encoding Cdkn1a was suppressed independent of changes in Trp53 mRNA levels and p53 DNA-binding activity. Considering the central role of the LMP1-NF-κB-Myc axis in B-lineage neoplasia, these findings further our understanding of the mechanisms by which PL inhibits B-lymphoma and provide a preclinical rationale for the inclusion of PL in new interventions in blood cancers.

The novel allele (3R) of the VNTR polymorphism in the XRCC5 promoter region dramatically decreases the gene expression

Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of X-ray repair cross-complementing 5 (MIM: 194364, XRCC5; rs6147172) was reported. The aim of the present study is to evaluate the influence of this polymorphism on XRCC5 mRNA levels. Genotypes of XRCC5 VNTR were determined by high resolution of melting analysis (HRMA). The quantitative XRCC5 mRNA expression (compared to ß-actin expression) among 0R/1R, 1R/2R, and 1R/3R genotypes was investigated. There was a negative correlation between the overall number of tandem repeats and XRCC5 expression (r=-0.965, df=7, P<0.001). The mRNA level of XRCC5 decreased as function of number of tandem repeats. The 3R allele of the VNTR polymorphism in the XRCC5 promoter region dramatically decreases the gene expression.

Aberrant expression of proteins involved in signal transduction and DNA repair pathways in lung cancer and their association with clinical parameters

BACKGROUND

Because cell signaling and cell metabolic pathways are executed through proteins, protein signatures in primary tumors are useful for identifying key nodes in signaling networks whose alteration is associated with malignancy and/or clinical outcomes. This study aimed to determine protein signatures in primary lung cancer tissues.

METHODOLOGY/ PRINCIPAL FINDINGS

We analyzed 126 proteins and/or protein phosphorylation sites in case-matched normal and tumor samples from 101 lung cancer patients with reverse-phase protein array (RPPA) assay. The results showed that 18 molecules were significantly different (p<0.05) by at least 30% between normal and tumor tissues. Most of those molecules play roles in cell proliferation, DNA repair, signal transduction and lipid metabolism, or function as cell surface/matrix proteins. We also validated RPPA results by Western blot and/or immunohistochemical analyses for some of those molecules. Statistical analyses showed that Ku80 levels were significantly higher in tumors of nonsmokers than in those of smokers. Cyclin B1 levels were significantly overexpressed in poorly differentiated tumors while Cox2 levels were significantly overexpressed in neuroendocrinal tumors. A high level of Stat5 is associated with favorable survival outcome for patients treated with surgery.

CONCLUSIONS/ SIGNIFICANCE

Our results revealed that some molecules involved in DNA damage/repair, signal transductions, lipid metabolism, and cell proliferation were drastically aberrant in lung cancer tissues, and Stat5 may serve a molecular marker for prognosis of lung cancers.

NF-κB regulates DNA double-strand break repair in conjunction with BRCA1-CtIP complexes

NF-κB is involved in immune responses, inflammation, oncogenesis, cell proliferation and apoptosis. Even though NF-κB can be activated by DNA damage via Ataxia telangiectasia-mutated (ATM) signalling, little was known about an involvement in DNA repair. In this work, we dissected distinct DNA double-strand break (DSB) repair mechanisms revealing a stimulatory role of NF-κB in homologous recombination (HR). This effect was independent of chromatin context, cell cycle distribution or cross-talk with p53. It was not mediated by the transcriptional NF-κB targets Bcl2, BAX or Ku70, known for their dual roles in apoptosis and DSB repair. A contribution by Bcl-xL was abrogated when caspases were inhibited. Notably, HR induction by NF-κB required the targets ATM and BRCA2. Additionally, we provide evidence that NF-κB interacts with CtIP-BRCA1 complexes and promotes BRCA1 stabilization, and thereby contributes to HR induction. Immunofluorescence analysis revealed accelerated formation of replication protein A (RPA) and Rad51 foci upon NF-κB activation indicating HR stimulation through DSB resection by the interacting CtIP-BRCA1 complex and Rad51 filament formation. Taken together, these results define multiple NF-κB-dependent mechanisms regulating HR induction, and thereby providing a novel intriguing explanation for both NF-κB-mediated resistance to chemo- and radiotherapies as well as for the sensitization by pharmaceutical intervention of NF-κB activation.

Ku80 is differentially expressed in human lung carcinomas and upregulated in response to irradiation in mice

Based on the role of Ku80 in mediating radiation-induced DNA repair, we investigated Ku80 expression in human lung cancers of different pathological types and evaluated the effect of radiotherapy on Ku80 expression levels in a mouse model. We used immunohistochemistry and real-time PCR to determine Ku80 protein and mRNA levels, respectively. We inoculated nude mice with A549 cells and subjected the tumor-bearing mice to varying doses of irradiation. Lung carcinoma tissue exhibited higher Ku80 mRNA and protein levels when compared with normal tissue. Among the tumor subtypes, lung adenocarcinoma and lung squamous carcinoma showed higher levels of Ku80 protein and mRNA, compared with small-cell lung carcinoma. There was a dose-dependent and time-dependent increase in Ku80 mRNA levels in nude mice that were inoculated with A549 cells and exposed to varying doses of irradiation. Ku80 may play an important role in the DNA damage response pathway. Higher Ku80 levels in lung squamous carcinoma and adenocarcinoma may explain their lower radiosensitivity when compared with small-cell lung carcinoma. Ku80 expression levels could be useful in predicting radiosensitivity of lung tumors and inhibition of Ku80 may be an interesting target to improve radiosensitivity in lung cancer patients.

Ku80 gene G-1401T promoter polymorphism and risk of gastric cancer

AIM: To evaluate the possible relationship between the Ku80 gene polymorphism and the risk of gastric cancer in China.

METHODS: In this hospital-based case-control study of gastric cancer in Jiangsu Province, China, we investigated the association of the Ku80 G-1401T (rs828907) polymorphism with gastric cancer risk. A total of 241 patients with gastric cancer and 273 age- and sex-matched control subjects were genotyped and analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS: The frequencies of genotypes GG, GT and TT were 65.6%, 22.8% and 11.6% in gastric cancer cases, respectively, and 75.8%, 17.6% and 6.6% in controls, respectively. There were significant differences between gastric cancer and control groups in the distribution of their genotypes (P = 0.03) and allelic frequencies (P = 0.002) in the Ku80 promoter G-1401T polymorphism.

CONCLUSION: The T allele of Ku80 G-1401T may be associated with the development of gastric cancer.

Activated PI3K/Akt/COX-2 pathway induces resistance to radiation in human cervical cancer HeLa cells

Activation of Akt, or protein kinase B, is frequently observed in human cancers. It has been demonstrated that PI3K activation leads to radiation resistance. Here, the role of PI3K/Akt/COX-2 pathway in the resistance to radiation in human cervical cancer HeLa cells is explored. Cultured HeLa cells were randomly assigned to five treatment groups: control, radiation, LY294002, PI3K antagonist, and the COX-2-antagonist celecoxib, with the objective of determining the role of PI3K/Akt/COX-2 pathway in the radiation resistance of HeLa cells. The cell survival ratios were computed by clone formation. To calculate the quasi-threshold dose (Dq), mean lethal dose (D(0)), survival fraction at 2 Gy radiation dose (SF(2)), and radiosensitization ratio, the cell survival curves were fitted to the one-hit multitarget model. The protein expression profiles for pAkt, Akt, COX-2, Bad, and pBad were detected by Western blot analysis, and the mRNA expression profiles for COX-2 and Bad were analyzed by RT-polymerase chain reaction. Treatment with a combination of celecoxib, LY294002, and radiation resulted in elevated Dq, D(0), and SF(2), and increased radiosensitivity in HeLa cells. The PI3K/Akt/COX-2 pathway was activated by radiation, whereas celecoxib inhibited the activation of the PI3K/Akt/COX-2 axis through several targets. Our results indicate that the activated PI3K/Akt/COX-2 signal transduction pathway was the main cause for decline in radiosensitivity in HeLa cells. This study proposes that the inhibition of the PI3K/Akt/COX-2 pathway can synergistically enhance radiation efficacy.

The DNA repair complex Ku70/86 modulates Apaf1 expression upon DNA damage

Apaf1 is a key regulator of the mitochondrial intrinsic pathway of apoptosis, as it activates executioner caspases by forming the apoptotic machinery apoptosome. Its genetic regulation and its post-translational modification are crucial under the various conditions where apoptosis occurs. Here we describe Ku70/86, a mediator of non-homologous end-joining pathway of DNA repair, as a novel regulator of Apaf1 transcription. Through analysing different Apaf1 promoter mutants, we identified an element repressing the Apaf1 promoter. We demonstrated that Ku70/86 is a nuclear factor able to bind this repressing element and downregulating Apaf1 transcription. We also found that Ku70/86 interaction with Apaf1 promoter is dynamically modulated upon DNA damage. The effect of this binding is a downregulation of Apaf1 expression immediately following the damage to DNA; conversely, we observed Apaf1 upregulation and apoptosis activation when Ku70/86 unleashes the Apaf1-repressing element. Therefore, besides regulating DNA repair, our results suggest that Ku70/86 binds to the Apaf1 promoter and represses its activity. This may help to inhibit the apoptosome pathway of cell death and contribute to regulate cell survival.

COX-2 inhibitor celecoxib improves radiosensitivity of human colon carcinoma cell line SW480

AIM: To determine whether celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, can improve radiosensitivity of human colon carcinoma cell line SW480.

METHODS: Cultured SW480 cells were treated with celecoxib for 24 h and then irradiated with different doses of X-rays. Cell survival was evaluated by colony formation assay. To calculate Dq, D0, SF2 and SER, the cell survival curve was fitted by the one-hit multi-target model. After 6-Gy radiation, the apoptosis of SW480 cells was detected by flow cytometry, and the expression of pAkt, COX-2, and pBad in SW480 cells was detected by Western blot.

RESULTS: The Dq, D0 and SF2 values for irradiated SW480 cells pretreated with celecoxib were lower than those for unpretreated ones (0.995 vs 2.527, 1.091 vs 1.622 and 0.352 vs 0.805, respectively; all P < 0.05). The SER for irradiated SW480 cells pretreated with celecoxib was 1.487. X-ray radiation enhanced the expression of pAkt, COX-2 and pBad proteins in SW480 cells. The expression levels of pAkt, COX-2 and pBad proteins in irradiated SW480 cells pretreated with celecoxib were lower than those in unpretreated ones. The apoptosis rate was significantly higher in irradiated SW480 cells pretreated with celecoxib than in unpretreated ones (15.02 ± 2.16 vs 6.25 ± 1.22, P < 0.05).

CONCLUSION: Celecoxib improves radiosensitivity of human colon carcinoma cell line SW480 perhaps by inhibiting the activation of the PI3K/Akt/COX-2 pathway.

Helicobacter pylori in a Korean isolate expressed proteins differentially in human gastric epithelial cells

PURPOSE

The proteins expressed in gastric epithelial cells infected with Helicobacter pylori (H. pylori) may determine the clinical outcome such as chronic gastritis, peptic ulcer, and gastric carcinoma. The present study aims to determine the differentially expressed proteins in human gastric epithelial AGS cells that were infected with H. pylori in a Korean isolate, a cagA+, vacA s1b m2 iceA1 H. pylori by proteomic analysis. The differentially expressed proteins, whose expression levels were more or less than twofold in H. pylori-infected cells, were analyzed.

RESULTS

Ten proteins (chromatin assembly factor-1, proliferating cell nuclear antigen, 14-3-3 protein tau, eukaryotic translation initiation factor 6, heat-shock protein 90beta, dimethylarginine dimethylaminohydrolase-1, L-lactate dehydrogenase B chain, prohibitin, triosephosphate isomerase, protein disulfide isomerase) were up-regulated while eight proteins (heat-shock gp96 precursor, nucleophosmin, ornithine aminotransferase, Ku70, L-arginine-glycine amidinotransferase, Smad anchor for receptor activation, ADP-ribosylation factor, WD repeat-containing protein isoform 1) were down-regulated by H. pylori infection in AGS cells. These proteins are related to cell proliferation, cell adhesion, carcinogenesis, cell-defense mechanisms against oxidative stress, membrane trafficking, and energy metabolism.

CONCLUSIONS

Oxidative stress, cell proliferation, cell adhesion, and membrane trafficking may be involved in the pathogenesis of gastric diseases including cancer associated with H. pylori in a Korean isolate.

alphaPix interacts with Helicobacter pylori CagA to induce IL-8 expression in gastric epithelial cells

OBJECTIVE

Helicobacter pylori CagA, translocated into gastric epithelial cells, induces IL-8 expression through the signalling pathways, including extracellular signal-regulated kinase (ERK) and nuclear factor-kappaB (NF-kappaB). We previously demonstrated that CagA interacts with host alphaPix. The present study was purposed to determine the role of the interaction of alphaPix with CagA on the signalling pathways for IL-8 expression in H. pylori-infected gastric epithelial cells.

MATERIAL AND METHODS

H. pylori HP99 strain (CagA+, VacA+) was infected to gastric epithelial AGS cells transfected with non-targeting (NT) or alphaPix- targeting siRNA. Activation of signalling molecules including p21-activated kinase (PAK), ERK and NF-kappaB, and expression of IL-8 in the cells were assessed.

RESULTS

H. pylori CagA was delivered into AGS cells and then interacted with alphaPix at 4 h following H. pylori infection. PAK1, ERK and NF-kappaB were activated in the cells containing NT and alphaPix siRNA at 1-2 h following H. pylori infection. However, after 4 h, the time when CagA was delivered into the cells, the activations of PAK1, ERK and NF-kappaB were inhibited by down-regulation of alphaPix using siRNA but not by NT siRNA. The results indicate that alphaPix is required for H. pylori-mediated signalling of PAK1, ERK and NF-kappaB. Additionally, alphaPix siRNA suppressed IL-8 induction after translocation of CagA into the cells, indicating that interaction of CagA with alphaPix is critical for CagA-mediating signalling for IL-8 expression.

CONCLUSIONS

The interaction of alphaPix with CagA activates PAK1, ERK and NF-kappaB, which induces IL-8 expression in H. pylori-infected gastric epithelial cells.