Inhibition of poly(ADP-Ribose)polymerase:A promising strategy targeting pancreatic cancer with BRCAness phenotype

The use of chemotherapeutic regimens for the treatment of pancreatic cancer is still limited because pancreatic cancer is usually diagnosed at an advanced stage as a refractory disease in which symptoms are difficult to recognize in the early stages.Furthermore,at advanced stages,there are important challenges to achieve clinical benefit and symptom resolution,even with the use of an expanded spectrum of anticancer drugs.Recently,a point of reduced susceptibility to conventional chemotherapies by breast cancer susceptibility gene(BRCA)mutations led to a new perspective for overcoming the resistance of pancreatic cancer within the framework of increased genome instability.Poly(ADP-Ribose)polymerase(PARP)-1 is an enzyme that can regulate intrinsic functions,such as response to DNA damage.Therefore,in an environment where germline mutations in BRCAs(BRCAness)inhibit homologous recombination in DNA damage,resulting in a lack of DNA damage response,a key role of PARP-1 for the adaptation of the genome instability could be further emphasized.Here,we summarized the key functional role of PARP-1 in genomic instability of pancreatic cancer with the BRCAness phenotype and listed clinical applications and outcomes of PARP-1 inhibitors to highlight the importance of targeting PARP-1 activity.

Poly(ADP-ribose) polymerase inhibition reveals a potential mechanism to promote neuroprotection and treat neuropathic pain

Neuropathic pain is triggered by the lesions to peripheral nerves which alter their structure and function. Neuroprotective approaches that jimit the pathological changes and improve the behavioral outcome have been well explained in different experimental models of neuropathy but translation of such strategies to clinics has been disappointing. Experimental evidences revealed the role of free radicals, especially per- oxynitrite after the nerve injury. They provoke oxidative DNA damage and consequent over-activation of the poly（ADP-ribose） polymerase （PARP） upregulates pro-inflammatory pathways, causing bioenergetic crisis and neuronal death. Along with these changes, it causes mitochondrial dysfunction leading to neu- ronal apoptosis. In related preclinical studies agents that neutralize the free radicals and pharmacological inhibitors of PARP have shown benefits in treating experimental neuropathy. This article reviews the in- volvement of PARP over-activation in trauma induced neuropathy and therapeutic significance of PARP inhibitors in the experimental neuropathy and neuropathic pain.

Multiple facets of poly(ADP-ribose) polymerase-1 in neurological diseases

The highly conserved abundant nuclear protein poly （ADP-ribose） polymerase-1 （PARP-1） is activated by DNA damage. PARP-1 activation is associated in DNA repair, cell death and inflammation. Since oxidative stress induced robust DNA damage and wide spread inflamma- tory responses are common pathologies of various CNS diseases, the attention towards PARP-1 as a therapeutic target has been amplifying. This review highlights the multiple roles of PARP- 1 in neurological diseases and po- tential of PARP- 1 inhibitors to enter clinical translation.

Poly(ADP-ribose) polymerase-1 gene polymorphism in various Chinese nationalities

Poly （ADP-ribose） polymerase-1 （PARP-1） can exacerbate ischemic brain injury and lessen ischemic neuronal death, which may be associated with PARP-1 polymorphisms. The present study investigated human PARP-1 gene polymorphisms in various Chinese nationalities, the results of which could potentially help in the treatment and prevention of neurologic diseases. Genetic polymorphisms of seven exons in the PARP-1 gene, in 898 Chinese Han, Buyi, Shui, Miao, and Zhuang subjects, were investigated by PCR-single-strand conformation polymorphism. A single-strand conformation polymorphism variant in exons 12, 13, 16, and 17 of the PARP-1 gene was identified in 148 people, with two stationary bands showing three degenerative single strands. Results showed that the PARP-1 gene polymorphisms exist in various nationalities, and may act as a biomarker for susceptibility to disease.

Effect of the regimen of Gaoshan Hongjingtian on the mechanism of poly（ADP-ribose） polymerase regulation of nuclear factor kappa B in the experimental diabetic retinopathy

Background Poly（ADP-ribose） polymerase （PARP） plays an important role in the death of retinal capillary cells in diabetic retinopathy （DR） partly via its regulation of nuclear factor kappa B （NF-κB）. The current study investigated the effect of the regimen of Gaoshan Hongjingtian （RG） on the mechanism of PARP regulation of NF-κB, and demonstrated the possible impact of the RG and Gaoshan Hongjingtian （Rhodiola sachalinensis, RS） on diabetic retinopathy. Methods Wistar rats were made diabetic by administering streptozotocin. They were then assigned to three groups at random. After 2 months, the three groups of these diabetic rats were treated with RS or RG, or untreated. Analyses of expression levels of PARP, NF-κB, and intercellular adhesion molecule-1 （ICAM-1） in the retinas of rats in different groups were performed by Western blotting and immunohistochemical assays, and mRNA levels of NF-κB and ICAM-1 were determined by real-time polymerase chain reaction （PCR）. In addition, the basement membranes of capillaries in the rats＇ retinas were observed using electron microscopy, and diabetes-induced capillary degeneration （ghost pericytes and acellular capillaries） were quantitated. Results From the third month after the injection of streptozotocin, the diabetic rats were given daily RG, RS or tap water separately. The diabetic rats failed to gain weight compared with normal age-matched rats, whereas their glycated hemoglobin levels were significantly increased. After 5 months, the mRNA levels of NF-KB and ICAM-1 and the protein expression of PARP, NF-κB, and ICAM-1 were significantly increased in the retinas of diabetic rats in the untreated group compared with the nondiabetic controls. After 8 months, the number of degenerated retinal capillaries （ghost pericytes and acellular capillaries） was significantly increased in the diabetic rats in the untreated group compared with normal age-matched rats. RG and RS inhibited diabetes-induced over-expression of PARP, NF-KB, and ICAM-1 in the retinas of diabetic rats at the end of 5-month diabetic duration. Treatment using RG and RS significantly inhibited increases in the number of acellular capillaries and pericyte ghosts and suppressed the basement membrane thickening in the retinas of rats with diabetes for 8 months compared with the control diabetic rats. Conclusions These results indicate that PARP plays an important role in the pathogenesis of diabetic retinopathy. RS and RG may have acted on the mechanism of PARP regulation of NF-κB, which suppressed the expression of NF-KB and ICAM-1, and led to the inhibition of retinal capillary degeneration.

Inhibition of CD38/Cyclic ADP-ribose Pathway Protects Rats against Ropivacaine-induced Convulsion

Background： The CD38/cyclic ADP-ribose （cADPR） pathway plays a role in various central nervous system diseases and in morphine tolerance, but its role in local anesthetic intoxication is unknown. The aim of this study was to determine the role of the CD38/cADPR pathway in ropivacaine-induced convulsion. Methods： Forty male Sprague-Dawley rats were randomly divided into five groups （n = 8 per group）： sham group, ropivacaine group, ropivacaine＋8-Br-cADPR （5 nmol） group, ropivacaine＋8-Br-cADPR （10 nmol） group, and ropivacaine＋8-Br-cADPR （20 nmol） group （no rats died）. Rats were intracerebroventricularly injected with normal saline or 8-Br-cADPR 30 min before receiving an intraperitoneal injection of ropivacaine. Electroencephalography and convulsion behavior scores were recorded. The hippocampus was harvested from each group and subjected to nicotinamide adenine dinucleotide and cADPR assays, Western blotting analysis, and malondialdehyde （MDA） and superoxide dismutase （SOD） assays. Results： Intraperitoneal injection of ropivacaine （33.8 mg/kg） induced convulsions in rats. CD38 and cADPR levels increased significantly following ropivacaine-induced convulsion （P = 0.031 and 0.020, respectively, compared with the sham group）. Intraventricular injection of 8-Br-cADPR （5, 10, and 20 nmol） significantly prolonged convulsion latency （P = 0.037, 0.034, and 0.000, respectively）, reduced convulsion duration （P = 0.005, 0.005, and 0.005, respectively）, and reduced convulsion behavior scores （P = 0.015, 0.015, and 0.000, respectively）. Intraventricular injection of 8-Br-cADPR （10 nmol） also increased the B-cell lymphoma-2 （Bcl-2）/Bcl-2-associated X protein ratio （P = 0.044） and reduced cleaved Caspase 3/Caspase 3 ratio, inducible nitric oxide synthase, MDAand SOD levels （P = 0.014, 0.044, 0.001, and 0.010, respectively） compared with the ropivacaine group. Conclusions： The CD38/cADPR pathway is activated in ropivacaine-induced convulsion. Inhibiting this pathway alleviates ropivacaine-induced convulsion and protects the brain from apoptosis and oxidative stress.

Assaying poly(ADP-ribose) polymerase activity in plants by polarographic method

A new method has been developed to assay poly(ADP-ribose) polymerase (PARP) activity in plant tissues through determining the content of nicotinamide (NIC) produced by enzymatic reaction by linear sweeping polarographic method. The detection limit of NIC was 0.03μmol/L, the calibration graph was linear up to 5μmol/L ( r = 0.999). The recoveries were approximately in the range of 92% to 98% and the relative standard deviations were less

Poly （ADP-ribose） polymerase inhibitor reduces heart ischaemia/ reperfusion injury via inflammation and Akt signalling in rats

Background Poly （ADP-ribose） polymerase （PARP） has been proposed to play an important role in the pathogenesis of heart ischaemia/reperfusion （I/R） injury. 3,4-dihydro-5-[4-（1-piperidinyl）butoxy]-l（2H）-isoquinolinone （DPQ）, a potent PARP inhibitor, has cardiac protective effects. Because the underlying mechanisms are not understood, we investigated the effect of DPQ on heart I/R injury and its mechanisms. Methods Studies were performed with I/R rats＇ hearts. DPQ was used to inhibit the activation of PARP. Cardiac function and cellular apoptosis were assessed. The activation of PARP, transcription factor nuclear factor-kappaB （NF-KB）, intercellular adhesion molecule-1 （ICAM-1）, cyclooxygenase-2 （COX-2） and matrix metalloproteinase-9 （MMP-9） were evaluated. We also evaluated expression of Akt and two of its downstream targets, glycogen synthase kinase-313 （GSK- 3β） and forkhead transcription factor FOXO3a. Results Administration of DPQ significantly decreased the activation of PARP and cellular apoptosis from （35±5）% to （20±4）% and simultaneously improved the cardiac function. DPQ reduced the expressions of NF-KB, ICAM-1, COX-2 and MMP-9 in rat heart and facilitated the activations of phosphor-Akt, phosphor-GSK-3β and phosphor-FOXO3a. Conclusion The protective effects of DPQ were associated with the suppression of inflammation and the activation of the Akt signalling pathways suggesting that the inhibition of poly （ADP-ribose） polymerase reduced heart I/R injury in rats.

Association of poly(ADP-ribose) polymerase activity in circulating mononuclear cells with myocardial dysfunction in patients with septic shock

Background Severe sepsis and septic shock are the leading causes of morbidity and mortality in hospitalized patients.This study aimed to investigate the association of poly（ADP-ribose） polymerase-1 （PARP-1） activity in circulating mononuclear cells with myocardial dysfunction in patients with septic shock.Methods A total of 64 patients with septic shock were divided into the survival group （n=41） and the nonsurvival group （n=23） according to mortality at 28 days after enrollments.PARP-1 activity in circulating mononuclear cells,brain natriuretic peptide,Acute Physiology and Chronic Health Evaluation Ⅱ score,the cardiac index （CI）,the cardiac function index （CFI）,global ejection fraction （GEF）,and the left ventricular contractility index （dp/dt max） were measured after admission to the intensive care unit.Results PARP-1 activity in circulating mononuclear cells of nonsurvival patients with septic shock was significantly higher than that in survival patients.PARP-1 activity in circulating mononuclear cells was strongly,negatively correlated with the CI,the CFI,GEE and dp/dt max.Multiple Logistic regression analysis showed that PARP-1 activity in circulating mononuclear cells was an independent risk factor of myocardial dysfunction.The optimal cutoff point of PARP-1 activity for predicting 28-day mortality was 942 nmol/L with a sensibility of 78.2% and specificity of 65.1%.Conclusion PARP-1 activity in circulating mononuclear cells is significantly associated with myocardial dysfunction and may have prognostic value in patients with septic shock.

Effects of 3-aminobenzamide on poly(ADP-ribose)polymerase expression,apoptosis and cell cycle progression of HeLa cells after X-ray irradiation

The aim of this paper is to study the changes of apoptosis and cell cycle progression in HeLa cells after the poly(ADP-ribose)polymerase(PARP)was inhibited by its inhibitor 3-aminobenzamide(3-AB)and the mechan-isms of PARP action on HeLa cells damaged by irra-diation.Flow cytometry(FCM)was used to examine the PARP expression and the percentage of apoptotic cells and cell cycle progression.The percentage of HeLa cells with positive expression of PARP protein 2,4,8 and 12 h after administrated with 3-AB was significantly lower than that of the control(P<0.01).The percentages of apoptotic cells in the 3-AB plus irradiation group at the time points of 2,8,12 and 24 h after 2 Gy irradiation were higher than that in the irradiation group(P<0.01 or P<0.05)and the percentage of G2 cells decreased signifi-cantly(P<0.01 or P<0.05).It indicates that 3-AB can rapidly inhibit PARP expression of HeLa cells,promote cell apoptosis and block G2 arrest induced by irradiation.

Structure-activity relationship of cyclic ADP-ribose, an update

Cyclic ADP-ribose (cADPR) is a universal Ca2+ mobilizing second messenger in many different cell types and organisms. cADPR activates Ca2+ release from endo/sarcoplasmic reticulum via ryanodine receptors. In addition, Ca2+ entry secondary to Ca2+ depletion is at least one of the mechanisms in which cADPR triggers Ca2+ inflow, too. Analogues of cADPR have been prepared by chemical and chemo-enzymatic routes. Most of the analogues were analyzed for biological activity in intact or permeabilized Jurkat T cells (a human T-lymphoma cell line). As a systematic approach, analogues were grouped according to alterations in the base, the northern ribose, the southern ribose, the pyrophosphate backbone, or in complex modifications, comprising more than one part of the molecule. Biological activity of the analogues is reviewed, with special emphasis on Jurkat T cells.

Systemic treatment strategies for triple-negative breast cancer

Triple-negative breast cancer(TNBC) is defined by the lack of immunohistochemical expression of the estrogen and progesterone receptors and human epidermal growth factor receptor 2(EGFR2). Most TNBC has a basal-like molecular phenotype by gene expression profiling and shares clinical and pathological features with hereditary BRCA1 related breast cancers. This review evaluates the activity of available chemotherapy and targeted agents in TNBC. A systematic review of PubM ed and conference databases was carried out to identify randomised clinical trials reporting outcomes in women with TNBC treated with chemotherapy and targeted agents. Our review identified TNBC studies of chemotherapy and targeted agents with different mechanisms of action, including induction of synthetic lethality and inhibition of angiogenesis, growth and survival pathways. TNBC is sensitive to taxanes and anthracyclins. Platinum agents are effective in TNBC patients with BRCA1 mutation, either alone or in combination with poly adenosine diphosphate polymerase 1 inhibitors. Combinations of ixabepilone and capecitabine have added to progression-free survival(PFS) without survival benefit in metastatic TNBC. Antiangiogenic agents, tyrosine kinase inhibitors and EGFR inhibitorsin combination with chemotherapy produced only modest gains in PFS and had little impact on survival. TNBC subgroups respond differentially to specific targeted agents. In future, the treatment needs to be tailored for a specific patient, depending on the molecular characteristics of their malignancy. TNBC being a chemosensitive entity, combination with targeted agents have not produced substantial improvements in outcomes. Appropriate patient selection with rationale combinations of targeted agents is needed for success.

Synergistic Suppressive Effect of PARP-1 Inhibitor PJ34 and HDAC Inhibitor SAHA on Proliferation of Liver Cancer Cells

Summary： Poly （ADP-ribose） polymerase-1 （PARP-1） inhibitors and histone deacetylase （HDAC） in- hibitors have recently emerged as promising anticancer drugs. The aim of this study was to investigate the effect of combination treatment with the PARP inhibitor P J34 and HDAC inhibitor SAHA on the proliferation of liver cancer cells. Cell proliferation and apoptosis were assessed in three human liver cancer cell lines （HepG2, Hep3B and HCC-LM3） treated with PJ34 （8 μmol/L） and SAHA （1 panol/L）, alone or combined, by Cell Counting Kit-8 assay and flow cytometry, respectively. The nude mice bear- ing subcutaneous HepG2 tumors were administered different groups of drugs （10 mg/kg PJ34, 25 mg/kg SAHA, 10 mg/kg PJ34＋25 mg/kg SAHA）, and the inhibition rates of tumor growth were compared between groups. The results showed that combined use of P J34 and SAHA could synergistically inhibit the proliferation of liver cancer cell lines HepG2, Hep3B and HCC-LM3. The apoptosis rate of HepG2 cells treated with PJ34＋SAHA was significantly higher than that of HepG2 cells treated with PJ34 or SAHA alone （P〈0.05）. In vivo, the tumor inhibition rates were 53.5%, 61.4% and 82.6% in PJ34, SAHA and PJ34＋SAHA groups, respectively. The combined use of PJ34 and SAHA could significantly inhibit the xenograft tumor growth when compared with use of P J34 or SAHA alone （P〈0.05）. It was led to conclude that P J34 and SAHA can synergistically suppress the proliferation of liver cancer cells.

核因子蛋白90敲减对肝癌细胞增殖影响及机制的研究

目的探究核因子蛋白90(NF90)敲减对肝癌细胞增殖影响并探讨其可能机制。方法将靶向NF90的寡核苷酸链克隆至PLKO质粒后,包装出靶向敲减NF90的慢病毒shRNA(带有绿色荧光标签及G418抗性)。将肝癌细胞QGY-7703、SMMC-7721分为对照组及干扰组,分别感染包含随机序列shRNA和靶向NF90 shRNA的病毒液。48 h后流式分选出带有绿色荧光的阳性细胞,G418筛选阳性单克隆细胞株,Western blotting鉴定NF90的蛋白表达水平,最终在对照组中选取一株细胞命名shRNA-ns,在干扰组中选取NF90敲减效果良好且稳定的两株细胞命名为shRNA-1、shRNA-2。采用CCK-8法检测各株细胞的增殖情况,克隆形成试验分析各株细胞的克隆形成能力。质谱分析预测NF90的相关结合蛋白,内、外源免疫共沉淀确定NF90与多聚ADP核糖合成酶(PARP1)的关系,荧光定位分析NF90与PARP1在细胞内的定位情况。结果 shRNA-1、shRNA-2细胞中的NF90表达水平显著低于shRNA-ns细胞,表明包装的慢病毒敲减NF90效果良好。与shRNA-ns细胞比较,shRNA-1、shRNA-2细胞的生长缓慢,克隆形成数减少,差异均有统计学意义(P<0.01)。NF90与PARP1在细胞内相互结合并且共定位于细胞核。结论敲减NF90可抑制肝癌细胞增殖,其机制可能与PARP1相互作用有关。

PARP inhibitor reduces proliferation and increases apoptosis in breast cancer cells

Objective： Apoptosis is a reliable marker of chemotherapeutic efficacy. Olaparib and paclitaxel inhibit proliferation and induce apoptosis in a variety of cancers. We investigated the effects of paclitaxel combined with olaparib on apoptosis in breast cancer Bcap37 cells. Methods： Proliferation and apoptosis were detected by MTT assay and PI staining. Degradation of procaspase-3 and poly（ADP-ribose） polymerase （PARP） was analyzed by Western blotting. Results： Compared with paclitaxel alone, paclitaxel combined with 100 mg olaparib significantly reduced survival in Bcap37 cells at all tested treatment durations （P〈0.05）; inhibition increased with increasing olaparib dose and treatment time （P〈0.01）. Combined treatment yielded significantly higher rates of apoptosis （P〈0.05）, which also increased with time （P〈0.01）. Fluorescence micrographs showed that early and late apoptotic cells increased with treatment time. Pro-caspase-3 and PARP degradation was induced by paclitaxel and enhanced by olaparib in a dose-dependent manner. Thus, combined treatment was substantially more effective than treatment with paclitaxel alone. Conclusions： Our findings suggest that paclitaxel and olaparib inhibit breast cancer Bcap37 cell proliferation and induce apoptosis. Combined treatment further reduced cell growth and enhanced apoptosis, suggesting that this combination therapy may be a promising treaunent for breast cancer.

Mechanisms of acquired resistance of BRCA1/2-driven tumors to platinum compounds and PARP inhibitors

Molecular pathogenesis of tumors arising in BRCA1/2 germ-line mutation carriers usually includes somatic inactivation of the remaining allele of the involved gene.Consequently,BRCA1/2-driven cancers are sensitive to platinum-based therapy and poly(ADP-ribose)polymerase inhibitors(PARPi).Long-term exposure to these drugs may result in the emergence of secondary BRCA1/2 mutations,which restore the open-reading frame of the affected allele.This platinum/PARPi crossresistance mechanism applies both for BRCA1 and BRCA2 genes and has been repeatedly validated in various laboratory models and multiple clinical studies.There are some other routes associated with the partial rescue of BRCA1/2 function or the development of BRCA1/2-independent pathways for genomic maintenance;however,their actual clinical relevance remains to be established.In addition,studies on the short-term neoadjuvant therapy for ovarian cancer revealed that even chemonaive BRCA1-driven tumors contain a small proportion of BRCA1-proficient cells.These pre-existing cells with retained BRCA1 heterozygosity rapidly repopulate the tumor mass during platinum exposure,but become outcompeted by BRCA1-deficient cells during therapy holidays.Understanding of the platinum/PARPi resistance pathways has led to the development of novel therapeutic approaches,which aim to improve the management of BRCA1/2-related cancers and are currently undergoing preclinical and clinical evaluation.

BRCA mutated pancreatic cancer:A change is coming

Pancreatic cancer remains a leading cause of cancer-related death with few available therapies for advanced disease.Recently,patients with germline BRCA mutations have received increased attention due to advances in the management of BRCA mutated ovarian and breast tumors.Germline BRCA mutations significantly increase risk of developing pancreatic cancer and can be found in up to 8%of patients with sporadic pancreatic cancer.In patients with germline BRCA mutations,platinum-based chemotherapies and poly(ADP-ribose)polymerase inhibitors are effective treatment options which may offer survival benefits.This review will focus on the molecular biology,epidemiology,and management of BRCA-mutated pancreatic cancer.Further-more,we will discuss future directions for this area of research and promising active areas of research.

High mobility group box-1 release from H2O2-injured hepatocytes due to sirt1 functional inhibition

BACKGROUND High mobility group box-1 (HMGB1), recognized as a representative of damageassociated molecular patterns, is released during cell injury/death, triggering the inflammatory response and ultimately resulting in tissue damage. Dozens of studies have shown that HMGB1 is involved in certain diseases, but the details on how injured hepatocytes release HMGB1 need to be elicited. AIM To reveal HMGB1 release mechanism in hepatocytes undergoing oxidative stress. METHODS C57BL6/J male mice were fed a high-fat diet for 12 wk plus a single binge of ethanol to induce severe steatohepatitis. Hepatocytes treated with H2O2 were used to establish an in vitro model. Serum alanine aminotransferase, liver H2O2 content and catalase activity, lactate dehydrogenase and 8-hydroxy-2- deoxyguanosine content, nicotinamide adenine dinucleotide (NAD+) levels, and Sirtuin 1 (Sirt1) activity were detected by spectrophotometry. HMGB1 release was measured by enzyme linked immunosorbent assay. HMGB1 translocation was observed by immunohistochemistry/immunofluorescence or Western blot. Relative mRNA levels were assayed by qPCR and protein expression was detected by Western blot. Acetylated HMGB1 and poly(ADP-ribose)polymerase 1 (Parp1) were analyzed by Immunoprecipitation. RESULTS When hepatocytes were damaged, HMGB1 translocated from the nucleus to the cytoplasm because of its hyperacetylation and was passively released outside both in vivo and in vitro. After treatment with Sirt1-siRNA or Sirt1 inhibitor (EX527), the hyperacetylated HMGB1 in hepatocytes increased, and Sirt1 activity inhibited by H2O2 could be reversed by Parp1 inhibitor (DIQ). Parp1 and Sirt1 are two NAD+-dependent enzymes which play major roles in the decision of a cell to live or die in the context of stress . We showed that NAD+ depletion attributed to Parp1 activation after DNA damage was caused by oxidative stress in hepatocytes and resulted in Sirt1 activity inhibition. On the contrary, Sirt1 suppressed Parp1 by negatively regulating its gene expression and deacetylation. CONCLUSION The functional inhibition between Parp1 and Sirt1 leads to HMGB1 hyperacetylation, which leads to its translocation from the nucleus to the cytoplasm and finally outside the cell.

Inhibition of PARP1 Increases IRF-dependent Gene Transcription in Jurkat Cells

Poly(ADP-ribose) polymerase 1 (PARP1) plays important roles in the regulation of transcription factors. Mounting evidence has shown that inhibition of PARP1 influences the expression of genes associated with inflammatory response. Interferon regulatory factor 1 (IRF1) is a critical transcription factor for the development of both the innate and adaptive immune responses against infections. However, the molecular mechanism through which PARP1 mediates the effects has not been clearly demonstrated. Jurkat cells were exposed to dexamethasone (Dex) or PARP1 inhibitor PJ34. The expression levels of IL-12, LMP2, OAS1 and PKR were detected using real-time RT-PCR. The interactions between PARP1 and IRF1 were examined by coimmunoprecipitation (co-IP) assays. We further explored the mechanism of PARP1 suppressing IRF1 by assessing the activities of interferon stimulated response element (ISRE). The mRNA expression of IL-12, LMP2, OAS1 and PKR was obviously suppressed by Dex in Jurkat cells, which could be rescued by PJ34 treatment. Luciferase study revealed that poly(ADP-ribosyl)- ation suppressed IRF1-mediated transcription through preventing the binding of IRF1 to ISREs. PARP1 inhibited IRF1-mediated transcription in Jurkat cells by preventing IRF1 binding to ISREs in the promoters of target genes. It is suggested that PARP1 is a crucial regulator of IRF1-mediated immune response. This study provides experimental evidence for the possible application of PARP1 inhibitors in the treatment of IRF1-related immune anergy.

Importance of BRCA mutation for the current treatment of pancreatic cancer beyond maintenance

In this editorial,we comment on pancreatic cancer(PC),one of the most aggressive and lethal cancers.Only minimal improvements in survival rates have been achieved over recent years.Available chemotherapeutic regimens have little impact,and surgical resection remains the only reliable curative approach.We address current treatment options for these patients,focusing on the usefulness of breast cancer(BRCA)gene mutation as a prognostic biomarker and predictor of response to chemotherapy.Superior survival outcomes have been reported in patients with PC and mutant BRCA gene treated with first-line platinum-based chemotherapy.Therefore,it appears appropriate to include BRCA gene status among clinical criteria used to select the chemotherapy regimen.In addition,maintenance treatment with poly(ADP-ribose)polymerase inhibitors has been found to improve progression-free survival in patients with PC and mutated BRCA whose disease does not progress after first-line platinum-based chemotherapy.This combination has therefore been proposed as the optimal treatment regimen for these patients.