Expression Of Poly ADP-ribose Polymerase Research Articles

Mild external heating and reduction in spontaneous contractions of the bladder.

To measure the effect of external heating on bladder wall contractile function, histological structure and expression of proteins related to tissue protection and apoptosis. In vitro preparations of bladder wall and exvivo perfused pig bladders were heated from 37 to 42°C, 46 and 50°C for 15min. Isolated preparations were heated by radiant energy and perfused bladders were heated by altering perfusate temperature. Spontaneous contractions or pressure variations were recorded, as well as responses to the muscarinic agonist carbachol or motor nerve excitation invitro during heating. Tissue histology in control and after heating was analysed using haematoxylin and eosin staining and 4'-6-diamidino-2-phenylindole (DAPI) nuclear labelling. The effects of heating on protein expression levels of (i) heat shock proteins HSP27-pSer82 and inducible-HSP70 and (ii) caspase-3 and its downstream DNA-repair substrate poly-[ADP-ribose] polymerase (PARP) were measured. Heating to 42°C reduced spontaneous contractions or pressure variations by ~70%; effects were fully reversible. There were no effects on carbachol or nerve-mediated responses. Tissue histology was unaffected by heating, and expression of heat shock proteins as well as caspase-3 and PARP were also unaltered. A TRPV1 antagonist had no effect on the reduction of spontaneous activity. Heating to 46°C had a similar effect on spontaneous activity and also reduced the carbachol contracture. Urothelial structure was damaged, caspase-3 levels were increased and inducible-HSP70 levels declined. At 50°C evoked contractions were abolished, the urothelium was absent and heat shock proteins and PARP expression was reduced with raised caspase-3 expression. Heating to 42°C caused a profound, reversible and reproducible attenuation of spontaneous activity, with no tissue damage and no initiation of apoptosis pathways. Higher temperatures caused tissue damage and activation of apoptotic mechanisms. Mild heating offers a novel approach to reducing bladder spontaneous activity.

Simvastatin ameliorates ionizing radiation-induced apoptosis in the thymus by activating the AKT/sirtuin 1 pathway in mice.

Simvastatin is a HMG-CoA reductase inhibitor widely used to lower plasma cholesterol and to protect against cardiovascular risk factors. The aim of this study was to investigate whether simvastatin attenuates ionizing radiation-induced damage in the mouse thymus and to elucidate the possible mechanisms invovled. For this purpose, male C57BL/6J mice aged 6 weeks were used and exposed to 4 Gy 60Co γ-radiation with or without simvastatin (20 mg/kg/day, for 14 days). Apoptosis was determined by terminal deoxynucle-otidyltransferase-mediated dUTP nick-end labeling (TUNEL) assay or transmission electron microscopy (TEM) examination. Thymocytes were also isolated and incubated in DMEM supplemented with 10% FBS at 37°C and exposed to 8 Gy 60Co γ-radiation with or without simvastatin (20 µM). The expression levels of Bcl-2, p53, p-p53, AKT, sirtuin 1 and poly(ADP-ribose) polymerase (PARP) were determined by western blot analysis. TUNEL and TEM examination revealed that simvastatin treatment significantly mitigated ionizing radiation-induced apoptosis in the mouse thymus. It was also found that simvastatin treatment increased AKT/sirtuin 1 expression following exposure to ionizing radiation in vivo and in vitro. In the in vivo model, but not in the in vitro model, Bcl-2 and PARP expression was augmented and that of p53/p-p53 decreased following treatment with simvastatin. On the whole, our findings indicate that simvastatin exerts a protective effect against ionizing radiation-induced damage in the mouse thymus, which may be partially attributed to the activation of the AKT/sirtuin 1 pathway.

Abstract 3716: Exploring the significance of PARP-1 expression for therapy and clinical PET/CT imaging of PARP-1 in ovarian cancer

Abstract Introduction: Poly(ADP-ribose) Polymerase 1 (PARP-1) is a multi-faceted enzyme that plays a significant role in DNA single-strand break and double-strand break repair. PARP inhibitors are emerging targeted therapeutics that inhibit the catalytic activity of PARP-1 and trap it on DNA producing poisonous lesions that result in cell death. While there is a vast body of pre-clinical and clinical data supporting the use of PARP inhibitors in cancers that express homologous recombination deficiencies like mutations within BRCA1/2 genes, there is an inadequate characterization of PARP-1 expression patterns in this context. Through pre-clinical studies we have explored the dynamics of PARP-1 expression in response to genotoxic stress, as well as the consequences of PARP-1 deletion for PARP inhibitor therapy in BRCA1 deficient ovarian cancer. In parallel, our group has performed the first clinical PET imaging study in epithelial ovarian cancer measuring PARP-1 in vivo using [18F]FluorThanatrace ([18F]FTT). Methods: CRISPR/Cas9 mediated PARP1 gene deletion was performed in BRCA1 deficient ovarian cancer cell lines. Next, in vitro cell viability assays were performed to evaluate the relative potency of clinically used PARP inhibitors and cisplatin. Following genotoxic stress the dynamics of PARP-1 expression were evaluated. In parallel clinical PET/CT imaging of PARP-1 was performed in epithelial ovarian cancer patients with correlative tissue histology. Results: Our studies indicate there is a spectrum of PARP-1 expression in epithelial ovarian cancer and in vitro BRCA1 mutants show higher PARP-1 expression compared to non-BRCA mutants. In addition, PARP-1 expression is required for PARP inhibitor efficacy in vitro and is either more significant or equal to BRCA1 mutational status. Also, high PARP-1 expression corresponded with platinum sensitivity in vitro. Furthermore, we observed PARP-1 expression increased in response to genotoxic insult relative to DNA damage measured by gH2AX. Lastly, our observations have been further supplemented by clinical [18F]FTT PET/CT images in ovarian cancer patients, which showed a spectrum of PARP-1 expression that corresponded with DNA damage measured by gH2AX. Conclusion: PARP-1 expression has the potential to identify functional DNA repair deficiencies and to provide a biomarker for assessing response to DNA damaging therapies. In complement, clinical PET imaging with [18F]FTT offers a novel technology to determine PARP-1 expression in ovarian cancer patients and warrants further study. Citation Format: Mehran Makvandi, Austin Pantel, Lauren E. Schwartz, Kuiying Xu, Chia-Ju Hsieh, Hyoung Kim, Shi-Hong Li, Robert Doot, Sharon Lee, Fiona Simpkins, Roger A. Greenberg, David A. Mankoff, Robert H. Mach, Lilie Lin. Exploring the significance of PARP-1 expression for therapy and clinical PET/CT imaging of PARP-1 in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3716. doi:10.1158/1538-7445.AM2017-3716

Abstract 5197: Targeting PARP-1 to deliver alpha-particles to cancer chromatin

Abstract Introduction: Neuroblastoma (NB) is a radiosensitive pediatric cancer that develops in the sympathetic nervous system and typically affects children under the age of 10. High-risk NB is associated with a 40% 5-year survival rate. Nuclear enzyme poly (ADP-ribose) polymerase 1 (PARP-1) is overexpressed in high-risk NB, making it an attractive target for alpha-particle therapy. Alpha-particles have a short path length and high linear energy transfer, causing dense ionizations across DNA, inducing double stranded breaks that result in cell death. The purpose of this study was to explore a newly developed radiotherapeutic ([211At]MM4) that combines the targeting potential of a small molecule PARP inhibitor (PARPi) with the cytotoxic effects of 211At in high-risk NB. Methods: In vitro cytotoxicity was performed in a panel of high-risk NB cell lines to evaluate the relative potency of [211At]MM4. Next, DNA damage was assessed by measuring gH2AX foci formation at 1, 4, and 24 hrs after [211At]MM4 treatment. In parallel, PARP-1 expression was measured in response to therapy and cleaved PARP-1 was quantified to assess apoptosis. Cell cycle analysis was performed after treatment to identify therapy related effects. The in-vivo biodistribution of [211At]MM4 was performed alongside ex-vivo autoradiography. Tumor cytology for PARP-1, gH2AX, and Ki-67 was performed in response to therapy. Finally, in-vivo therapy experiments were performed. Results: Cytotoxicity data indicated a significant reduction in cell viability following treatment for all six NB cell lines, in-vitro co-incubation studies confirmed the specificity of [211At]-MM4 to its drug target. Immunofluorescence analysis showed a dose-dependent increase in both gH2AX and PARP-1 expression. The in-vivo biodistribution of [211At]MM4 revealed rapid tumor targeting at 1 hr and clearance from all tissues at 4 hrs. Ex-vivo autoradiography showed a tumor-muscle ratio greater than 6. Tumor cytology revealed DNA damage measured by gH2AX and PARP-1 expression increased following treatment. Small colonies of proliferating tumor cells were detected after treatment using Ki-67 staining. In-vivo therapy efficacy studies revealed low fractionated doses were tolerable and resulted in significant delay in tumor regrowth. Conclusion: [211At]MM4 is a novel alpha-emitting radiotherapeutic that specifically targets nuclear PARP-1 overexpression in neuroblastoma and incites double-stranded breaks in cancer DNA. The cytotoxic effects of [211At]MM4 have been experimentally validated both in-vitro and in-vivo; the results of these experiments confirm the therapeutic potential of [211At]MM4 as a viable treatment option for high-risk neuroblastoma. Citation Format: Laura Puentes, Kuiying Xu, Catherine Hou, Robert H. Mach, John M. Maris, Daniel A. Pryma, Mehran Makvandi. Targeting PARP-1 to deliver alpha-particles to cancer chromatin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5197. doi:10.1158/1538-7445.AM2017-5197

Abstract 3852: Validation of synthetic lethality of PARP and NAMPT dual inhibition in a small cell lung cancer PDX model

Abstract Small cell lung cancer (SCLC) is a highly malignant cancer type with a 5-year survival rate of less than 10%. Different from non-small cell lung cancer (NSCLC), no effective target therapies have been approved to treat SCLC. Poly (ADP) ribose polymerase (PARP) overexpression in SCLC has prompted great efforts to evaluate the role of PARP inhibitors in clinic. To maximize their therapeutic value it is urgent in need to explore the best combination strategies between PARP inhibitors and other pathway modulators. In this study we identified a SCLC patient-derived xenograft (PDX) model with high PARP level and low nicotinamide phosphoribosyltransferase (NAMPT) level. Furthermore, synergistic effect of PARP and NAMPT dual inhibition was demonstrated, supporting translational research of PARP inhibitors and NAMPT inhibitors in this model. The mRNA expression of PARP as well as its 30 most-studied synthetic lethality genes was compared between SCLC and NSCLC in both PDXs and cancer cell lines. We found that NAMPT levels decreased most significantly in SCLC compared with NSCLC across the 30 synthetic lethality genes of PARP. As NAMPT is the rate-limiting enzyme for the synthesis of the PARP substrate β-NAD+, we hypothesized that low β-NAD+ level due to low NAMPT level might render SCLC sensitive to PARP inhibition. LU-01-0547, a SCLC PDX model with high PARP and low NAMPT expression, was identified here. To test our hypothesis, we investigated the preclinical efficacy of ABT888, a PARP inhibitor, with or without FK866, a NAMPT inhibitor, in this subcutaneous xenograft model. The single-agent efficacy of ABT888 was demonstrated (TGI=96%@100 mg/kg, BID). At a sub-optimal dose (50 mg/kg, BID), treatment of ABT888 alone produced little activity in the same model, while its combination with a NAMPT inhibitor, FK866, significantly boosted the antitumor response indicating the synergistic effect (TGI=117%, ORR=6/6, CR=4/6). When nicotinic acid (NA) was administered to promote β-NAD+ biosynthesis via the de novo pathway other than the NAMPT-mediated transformation, the PARP inhibitor’s effectiveness was greatly antagonized (TGI=70% vs. 13%), suggesting β-NAD+ level might correlate with PARP inhibitor sensitivity. In conclusion, this study identified a SCLC PDX model with high PARP and low NAMPT expression. Synergistic inhibition of PARP and NAMPT in this model was demonstrated superior to either treatment alone in efficacy, which warranted its future application in drug discovery. To our knowledge, this was the first in vivo evidence of synthetic lethality in SCLC PDX, supporting future clinical test of combination of PARP and NAMPT inhibitors in SCLC patients. Citation Format: Zhixiang Zhang, Dongfang Li, Chen Chen, Bo Zhang, Xuzhen Tang, Hao Ye, Qingyang Gu, Qunsheng Ji. Validation of synthetic lethality of PARP and NAMPT dual inhibition in a small cell lung cancer PDX model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3852. doi:10.1158/1538-7445.AM2017-3852

Poly (ADP-Ribose) Polymerase-1 (PARP-1) Induction by Cocaine Is Post-Transcriptionally Regulated by miR-125b.

Cocaine exposure alters gene expression in the brain via methylation and acetylation of histones along with methylation of DNA. Recently, poly (ADP-ribose) polymerase-1 (PARP-1) catalyzed PARylation has been reported as an important regulator of cocaine-mediated gene expression. In this study, we report that the cellular microRNA “miR-125b” plays a key role for cocaine-induced PARP-1 expression. Acute and chronic cocaine exposure resulted in the downregulation of miR-125b concurrent with upregulation of PARP-1 in dopaminergic neuronal cells and nucleus accumbens (NAc) of mice but not in the medial prefrontal cortex (PFC) or ventral tegmental area (VTA). In silico analysis predicted a binding site of miR-125b in a conserved 3’-untranslated region (3’UTR) of the PARP-1 mRNA. Knockdown and overexpression studies showed that miR-125b levels negatively correlate with PARP-1 protein expression. Luciferase reporter assay using a vector containing the 3’UTR of PARP-1 mRNA confirmed regulation of PARP-1 by miR-125b. Specific nucleotide mutations within the binding site abrogated miR-125b’s regulatory effect on PARP-1 3’UTR. Finally, we established that downregulation of miR-125b and concurrent upregulation of PARP-1 is dependent on binding of cocaine to the dopamine transporter (DAT). Collectively, these results identify miR-125b as a post-transcriptional regulator of PARP-1 expression and establish a novel mechanism underlying the molecular effects of cocaine action.

Abstract 1942: The nicotinamide phosphoribosyltransferase (NAMPT) inhibitor, OT-82, exhibits in vitro and in vivo efficacy against patient-derived xenograft models of high-risk acute lymphoblastic leukemia

Abstract Cancer cells are highly dependent on nicotinamide phosphoribosyltransferase (NAMPT) for the biosynthesis of nicotinamide adenine dinucleotide (NAD). Besides its role in energy metabolism, NAMPT influences the activity of NAD-dependent enzymes, including poly (ADP-ribose) polymerase-1 (PARP-1) and sirtuins, and thereby regulates cellular survival and stress response. Disruption of NAD synthesis through NAMPT inhibition represents a potential therapeutic strategy for treating cancer. The aim of this study was to evaluate the efficacy of the novel NAMPT inhibitor OT-82, initially isolated for its selective toxicity against a panel of adult leukemia cell lines, in a diverse panel of leukemia cell lines in vitro and pediatric acute lymphoblastic leukemia (ALL) patient-derived xenografts (PDXs) in vivo, and to identify potential biomarkers predictive of OT-82 response. OT-82 demonstrated low nanomolar IC50 values (0.9 – 3.4 nM) in 3 ALL and 3 acute myeloid leukemia cell lines as determined by resazurin reduction assays. In vivo efficacy of OT-82 (40 mg/kg x 3 days x 3 weeks, p.o.) was evaluated as a single agent against pediatric ALL PDXs, including B-cell precursor ALL (n = 3), Philadelphia chromosome (Ph) positive ALL (n = 2), Ph-like ALL (n = 2), T-cell ALL (n = 3), and early T-cell precursor ALL (n = 3) in immune deficient (NSG) mice. Response to treatment was assessed by time to event or stringent objective response criteria modeled after the clinical setting. OT-82 was well tolerated, significantly increased event-free survival (EFS) relative to control mice in 11/13 ALL PDXs, and elicited objective responses in 11/13 (85%) PDXs [3 Partial Responses, 4 Complete Responses (CRs) and 4 Maintained CRs (MCRs)]. Analysis of basal protein expression revealed elevated levels of poly (ADP-ribosyl)ated (PARylated) PARP-1 in 4/5 responders versus 0/2 non-responders. In vitro studies examining various chemotherapeutic agents used for childhood leukemia showed synergy between cytarabine (AraC) and OT-82 in an ALL cell line. In an OT-82 sensitive Mixed Lineage Leukemia (MLL) PDX, treatment with AraC (25 mg/kg x 5 days x 2 weeks, i.p.) and OT-82 (40 mg/kg x 3 days x 2 weeks, p.o.) significantly increased EFS compared to OT-82 (P<0.0001) or AraC (P<0.0001) alone. Moreover, the OT-82/AraC combination elicited an MCR compared to OT-82 (CR) and AraC (Progressive Disease) alone. The results herein demonstrate significant activity of OT-82 against leukemia cell lines and a range of pediatric ALL subtypes in vivo, and the potential for PARylated PARP-1 expression as a biomarker for predicting OT-82 response. Moreover, the enhanced activity of OT-82 in combination with AraC over single agent therapy further suggests NAMPT inhibition as an attractive strategy for treating high-risk pediatric ALL. Supported by U01CA199000 from the NCI. Citation Format: Kathryn Evans, Tara Pritchard, Michelle J. Henderson, Klaartje Somers, Mawar Karsa, Leanna Cheung, Raymond Yung, Stephen W. Erickson, Lioubov Korotchkina, Olga Chernova, Andrei Gudkov, Malcolm A. Smith, Richard B. Lock. The nicotinamide phosphoribosyltransferase (NAMPT) inhibitor, OT-82, exhibits in vitro and in vivo efficacy against patient-derived xenograft models of high-risk acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1942. doi:10.1158/1538-7445.AM2017-1942

MKP-1 suppresses PARP-1 degradation to mediate cisplatin resistance.

Understanding the mechanisms of platinum compound resistance, including cisplatin resistance, has important implications for improving cancer treatments. Previous studies identified a potential role for mitogen-activated protein kinase phosphatase-1 (MKP-1) in cisplatin resistance. This work focuses on the regulation of poly(ADP-ribose) polymerase-1 (PARP-1) expression by MKP-1. We found that MKP-1 overexpression stimulates PARP-1 and poly(ADP-ribose) (PAR) protein expression and cisplatin resistance while its downregulation suppresses PARP-1 and PAR protein expression and cisplatin resistance. Silencing MKP-1 promoted PARP-1 ubiquitination, which decreased PARP-1 protein levels. We also found that silencing c-Jun N-terminal kinase 1/2 (JNK1/2) decreased PARP-1 ubiquitination while increasing total PARP-1 protein levels. Furthermore, we showed that acquired cisplatin resistant ovarian cancer cells expressed the high levels of MKP-1 and PARP-1 proteins, and that silencing MKP-1 or PARP-1 increased cisplatin sensitivity in resistant cells. Notably, the pharmacologic inhibition of PARP activity restored cisplatin sensitivity in MKP-1 overexpressing cells. Thus, this work indicates that suppression of JNK1/2 activity by MKP-1 maintains PARP-1 levels and suggests that MKP-1-mediated cisplatin resistance can be bypassed by PARP-1 inhibition.

Poly (ADP-ribose) polymerase-1 inhibition decreases proliferation through G2/M arrest in esophageal squamous cell carcinoma.

Poly (ADP-ribose) polymerase-1 (PARP1) plays a vital role in DNA repair and is expected to be an effective target in various malignancies. The aim of the present study was to investigate the clinical and biological significance of PARP1 expression in esophageal squamous cell carcinoma (ESCC). Immunohistochemical (IHC) staining was used to examine the association between PARP1 expression and the clinicopathological features of 86 patients with ESCC. The antitumor effect of small interfering RNA against PARP1 (siPARP1) was examined in a proliferation assay, and the mechanisms of this effect were investigated using western blot analysis and cell cycle assays. Cox multivariate analysis revealed that high expression of PARP1 in IHC staining was a statistically significant independent prognostic factor of poor overall survival (OS). The adjusted hazard ratio for OS in the group with high expression of PARP1 was 2.39 (95% confidence interval, 1.29–4.44; P=0.0051). In vitro assays showed that siPARP1 significantly decreased proliferation through G2/M arrest. Furthermore, western blot analysis showed that PARP1 was associated with the ataxia telangiectasia mutated-checkpoint kinase 2-cell division control 25c pathway. The present study suggests that PARP1 expression has a critical role in ESCC progression, and may be a clinical therapeutic target.

Abstract AP20: A PILOT STUDY OF A POLY (ADP–RIBOSE) POLYMERASE–1 (PARP) TARGETED NOVEL PET TRACER (18F–FLUOURTHANOTRACE) IN PATIENTS WITH OVARIAN CARCINOMA

Abstract PURPOSE: There is now substantial data that poly (ADP-ribose) polymerase-1 (PARP) inhibitors have activity in tumors with defects in homologous recombination, in particular BRCA-related cancers. One of the challenges, however, is identifying patients that may best respond to these class of drugs. 18F-FTT (fluorthanotrace) is a novel PET imaging tracer that can quantify PARP enzyme activity in vivo. We report results on an initial pilot study of 18F-FTT imaging in patients with ovarian carcinoma. METHODS: Eight patients with newly diagnosed or recurrent ovarian, primary peritoneal, or fallopian tube carcinoma and measurable disease underwent both 18F-FDG PET/CT and 18F-FTT PET/CT imaging within 30 days of each other. Patients who were undergoing surgery or had disease amenable to biopsy underwent dynamic imaging of the abdomen/pelvis and static skull base to mid-thigh imaging following injection of approximately 10mCi of 18F-FTT. Patients with no biopsy accessible disease underwent a series of whole body PET/CT scans over 4 hours following injection of 18F-FTT to evaluate the biodistribution and dosimetry of 18F-FTT. Standardized uptake value (SUV) was calculated for primary and/or metastatic implants on all patients with quantifiable tumor on both PET/CT scans. Quantitative assessment of the 18F-FTT PET/CT was performed first using the 18F-FDG PET/CT to identify and match lesions. Regions of interest were then drawn over the tumor implant using multiple planar view. Up to three lesions were quantified on each dataset (primary and metastases if present). Ex vivo autoradiography with [ 125I]-KX (a novel radio-iodinated PARP radiotracer that can quantitatively assess PARP-1 enzyme expression in vitro), immunohistochemical staining with γh2ax, CD45, and keratin was performed on tumor samples. RESULTS: Active regions of disease was noted for 7/8 patients on 18F-FDG PET/CT imaging and 18F-FTT PET/CT imaging. Maximum SUV of primary or metastases on 18F-FDG PET/CT ranged from 1.97-14.54 and on 18F-FTT PET/CT ranged from 3.04-12.13. We acquired tumor tissue on four patients for analysis. SUV on 18F-FTT PET/CT correlated with average counts/area on [ 125I]-KX autoradiography (R=0.70) and gammh2ax immunohistochemistry staining on tumor specimens. Low SUV FTT:FDG ratio was noted in 4/4 patients with platinum resistant disease and/or low PARP-1 expression on [ 125I]-KX autoradiography and high FTT:FDG ratio was noted in 2/3 patients with platinum sensitivity and/or high binding on [ 125I] KX auto-radiography. CONCLUSION: Our initial preliminary studies demonstrate that 18F-FTT localizes to known areas of tumor and may distinguish between tumors with low level expression of PARP and platinum resistance vs high levels of PARP and platinum sensitivity and may be a promising biomarker for PARP inhibitor and platinum sensitivity. Citation Format: Lilie Lin MD, Mehran Makvandi PharmD, Austin Pantel MD, Robert Doot PhD, Lauren Schwartz MD, Fiona Simpkins MD, David Mankoff MD PHD, Robert Mach PhD. A PILOT STUDY OF A POLY (ADP–RIBOSE) POLYMERASE–1 (PARP) TARGETED NOVEL PET TRACER (18F–FLUOURTHANOTRACE) IN PATIENTS WITH OVARIAN CARCINOMA [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP20.

Therapeutic Targeting of Poly(ADP-Ribose) Polymerase-1 (PARP1) in Cancer: Current Developments, Therapeutic Strategies, and Future Opportunities.

Poly(ADP-ribose) polymerase-1 (PARP-1) plays a central role in numerous cellular processes including DNA repair, replication, and transcription. PARP interacts directly, indirectly or via PARylation with various oncogenic proteins and regulates several transcription factors thereby modulating carcinogenesis. Therapeutic inhibition of PARP is therefore perceived as a promising anticancer strategy and a number of PARP inhibitors (PARPi) are currently under development and clinical evaluation. PARPi inhibit the DNA repair pathway and thus form the concept of synthetic lethality in cancer therapeutics. Preclinical and clinical studies have shown the potential of PARPi as chemopotentiator, radiosensitizer, or as adjuvant therapeutic agents. Recent studies have shown that PARP-1 could be either oncogenic or tumor suppressive in different cancers. PARP inhibitor resistance is also a growing concern in the clinical setting. Recently, changes in the levels of PARP-1 activity or expression in cancer patients have provided the basis for consideration of PARP-1 regulatory proteins as potential biomarkers. This review focuses on the current developments related to the role of PARP in cancer progression, therapeutic strategies targeting PARP-associated oncogenic signaling, and future opportunities in use of PARPi in anticancer therapeutics.

Hydroquinone induces TK6 cell growth arrest and apoptosis through PARP-1/p53 regulatory pathway.

Hydroquinone (HQ), one of the most important metabolites derived from benzene, induces cell cycle arrest and apoptosis. Poly(ADP-ribose) polymerase-1 (PARP-1) participates in various biological processes, including DNA repair and cell cycle regulation. To explore whether PARP-1 regulatory pathway mediated HQ-induced cell cycle arrest and apoptosis, we assessed the effect of PARP-1 suppression on induction of apoptosis analyzed by FACSCalibur flow cytometer in PARP-1 deficientTK6 cells (TK6-shPARP-1). We observed an increase in the fraction of cells in G1 phase by 7.6% and increased apoptosis by 4.5% in PARP-1-deficient TK6 cells (TK6-shPARP-1) compared to those negative control cells (TK6-shNC cells) in response to HQ treatment. Furthermore, HQ might activate the extrinsic pathways of apoptosis via up-regulation of Fas expression, followed by caspase-3 activation, apoptotic body, and sub G1 accumulation. Enhanced p53 expression was observed in TK6-shPARP-1 cells than in TK6-shNC cells after HQ treatment. In contrast, Fas expression was lower in TK6-shPARP-1 cells than in TK6-shNC cells. Therefore, we conclude that HQ may activate apoptotic signals via Fas up-regulation and p53-mediated apoptosis in TK6-shNC cells. The reduction of PARP-1 expression further intensified up-regulation of p53 in TK6-shPARP-1 cells, resulting in an increased G1→S phase cell arrest and apoptosis in TK6-shPARP-1 cells compared to TK6-shNC cells.

Abstract B31: Poly(ADP-ribose) Polymerase 1 as a novel target for alpha-particle therapy in high-risk neuroblastoma

Abstract Introduction: Poly(ADP-ribose) Polymerase 1 (PARP-1) is the second most abundant nuclear protein next to histones and offers a unique target for the delivery of alpha emitting radionuclides directly to chromatin maximizing radiobiological effects. Alpha emitting radionuclides decay through the emission of a high linear energy transfer alpha particle that travels only 50-70 µM. This results in dense ionizations over the alpha particle track length, causing high levels of DNA double strand breaks. High-risk neuroblastoma is a deadly pediatric malignancy that overexpresses PARP-1 and approximately 80% of patients succumb to their disease. By utilizing the overexpression of PARP-1 we aim to selectively target high-risk neuroblastomas for the delivery of alpha particles to induce irreparable DNA damage and subsequent cell death. Methods: Astatine-211 was produced on a JSW BC3015 cyclotron at 28.5 MeV via the Bi-209(α,2n)At-211 nuclear reaction. Astatine-211 was isolated by dry distillation and radiochemically functionalized onto a small molecule PARP inhibitor to afford 211At-MM4. Using a panel of neuroblastoma cell lines, the pharmacology and cytotoxicity of 211At-MM4 was evaluated in vitro. Next, protein analysis was performed by Western to evaluate expression of classical and alternative non-homologous end joining proteins. In addition, PARP-1 expression and DNA damage were assessed in response to therapy. Furthermore, in vivo therapy studies with PET/CT imaging of PARP-1 were performed to assess therapeutic potential and predictive capabilities of companion diagnostics. Results: IMR-05, SK-N-SH, and NLF were the most sensitive cell lines evaluated and Be-2-c was the most resistant cell line. All cell lines evaluated were high-risk neuroblastomas and baseline Western protein analysis did not reveal specific pathway dependence for classical or alternative non-homologous end joining defined by protein expression. Response to therapy showed significant increases in DNA damage measured by gH2AX. Interestingly PARP-1 expression was upregulated post therapy in the resistant cell line Be-2-c. IMR-05 was the most sensitive cell line in vitro and was translated to in vivo models where therapeutic efficacy was shown. PET/CT imaging of PARP-1 post therapy showed low tumor uptake and was indicative of response. Conclusion: 211At-MM4 is a small molecule PARP inhibitor functionalized with an alpha emitting radionuclide astatine-211 that can effectively deliver alpha-particles to the nucleus of cancer cells. The neuroblastoma cell lines evaluated showed differential sensitivities and in vitro results translated into in vivo models. Furthermore we have characterized a novel therapy for high-risk neuroblastoma and aim for future clinical translation. Citation Format: Mehran Makvandi, Catherine Hou, Kuiying Xu, Redmond-Craig Anderson, Samuel Ander-Effron, Robert H. Mach, John M. Maris, Daniel A. Pryma. Poly(ADP-ribose) Polymerase 1 as a novel target for alpha-particle therapy in high-risk neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr B31.

An Infectious Disease–Associated Il12b Polymorphism Regulates IL-12/23 p40 Transcription Involving Poly(ADP-Ribose) Polymerase 1

IL-12 and IL-23 are important host defense factors produced by APCs against certain intracellular and extracellular pathogens. Their dysregulation has also been implicated in several autoimmune diseases. The nucleotide polymorphism in the promoter region of Il12b (rs41292470 consisting of the long or short allele) encoding the shared subunit of IL-12 and IL-23, p40, has been reported to associate with susceptibility to infectious diseases and autoimmune disorders. How these genetic variants impact Il12b expression at the molecular level was unclear. We established an Il12b promoter-luciferase reporter system containing the long or short allele driving the reporter gene expression and found that the long allele (infection-resistant) displayed ∼2-fold higher transcriptional activity than the short allele (infection-susceptible), associated with a selective and differential nuclear binding activity to the two alleles in activated macrophages. DNA pull-down assays coupled with mass spectrometry analyses identified the specific DNA binding activity as poly(ADP-ribose) polymerase 1 (PARP-1). Small hairpin RNA-mediated knockdown of the endogenous PARP-1 expression resulted in reduced p40 mRNA expression and Il12b promoter activity. Bone marrow-derived macrophages from PARP-1-deficient mice had decreased p40 expression at both mRNA and protein levels. Furthermore, selective PARP-1 inhibitors resulted in impaired production of IL-12p40 and IL-23 in bone-marrow derived macrophages and PBMCs. Chromatin immunoprecipitation assay revealed that PARP-1 could bind specifically to Il12b in LPS-stimulated macrophages. Our study opens the way for further elucidating the molecular mechanism whereby allele-specific immune responses to foreign and self-antigens mediated by IL-12/IL-23 are controlled in an individually variable manner.

Arsenic, Cadmium, and Lead Like Troglitazone Trigger PPARγ-Dependent Poly (ADP-Ribose) Polymerase Expression and Subsequent Apoptosis in Rat Brain Astrocytes.

We previously demonstrated that arsenic, cadmium, and lead mixture at environmentally relevant doses induces astrocyte apoptosis in the developing brain. Here, we investigated the mechanism and contribution of each metal in inducing the apoptosis. We hypothesized participation of transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), reported to affect astrocyte survival. We treated cultured rat astrocytes with single metals and their combinations and performed apoptosis assay and measured PPARγ expression levels. We found that cadmium demonstrated maximum increase in PPARγ as well as apoptosis, followed by arsenic and then lead. Interestingly, we observed that the metals mimicked PPARγ agonist, troglitazone, and enhanced PPARγ-transcriptional activity. Co-treatment with PPARγ-siRNA or PPARγ-antagonist, GW9662, suppressed the astrocyte apoptosis, suggesting a prominent participation of PPARγ in metal(s)-induced astrocyte loss. We explored PPARγ-transcriptional activity and identify its target gene in apoptosis, performed in silico screening. We spotted PPARγ-response elements (PPREs) within poly(ADP-ribose) polymerase (PARP) gene, and through gel-shift assay verified metal(s)-mediated increased PPARγ binding to PARP-PPREs. Chromatin-immunoprecipitation and luciferase-reporter assays followed by real-time PCR and Western blotting proved PPRE-mediated PARP expression, where cadmium contributed most and lead least, and the effects of metal mixture were comparable with troglitazone. Eventually, dose-dependent increased cleaved-PARP/PARP ratio confirmed astrocyte apoptosis. Additionally, we found that PPARγ and PARP expressions were c-Jun N-terminal kinases and cyclin-dependent kinase5-dependent. In vivo treatment of developing rats with the metals corroborated enhanced PPARγ-dependent PARP and astrocyte apoptosis, where yet again cadmium contributed most. Overall, our study enlightens a novel PPARγ-dependent mechanism of As-, Cd-, and Pb-induced astrocyte apoptosis.

TNFR2 promotes Adriamycin resistance in breast cancer cells by repairing DNA damage.

In recent years, tumor necrosis factor receptor2 (TNFR2) has attracted increasing attention for its important roles in promoting proliferation, migration and angiogenesis in several types of cancer. However, its role in drug resistance remain unclear. In the present study, TNFR2 expression levels in MDA‑MB‑231 and MCF‑7 breast cancer cells were demonstrated to be associated with Adriamycin (ADM) resistance. Silencing of TNFR2 in MCF‑7 cells significantly inhibited ADM resistance, while overexpression of TNFR2 in MDA‑MB‑231 cells significantly enhanced ADM resistance. ADM treatment induced phosphorylation of the histone family2A variant X (pH2AX), an established marker of DNA damage. Silencing of TNFR2 in MCF‑7 cells further induced pH2AX levels but inhibited the expression of the DNA damage repair protein, poly(ADP‑ribose) polymerase (PARP). By contract, overexpression of TNFR2 in MDA‑MB‑231 cells decreased pH2AX levels and enhanced PARP expression. Of note, treatment with the PARP inhibitor ABT888 significantly abrogated the effects of TNFR2 on pH2AX expression. On a molecular mechanism level, TNFR2 significantly affected the phosphorylation of AKT serine/threonine kinase 1 (AKT) in both cell lines, and treatment with the AKT inhibitor LY294002 effectively abrogated TNFR2‑induced PARP expression. Adrug resistance assay demonstrated that treatment with either LY294002 or ABT888 inhibited ADM resistance in breast cancer cells, and combination treatment with both LY294002 and ABT888 exhibited a significantly stronger inhibition effect on ADM resistance. The present results indicated that TNFR2 promoted ADM resistance in breast cancer cells by regulating the DNA damage repair protein PARP via the AKT signaling pathway.

S-allylcysteine 매개 caspases의 활성화 및 PARP의 불활성화를 통한 HeLa 세포주의 증식 억제효과

본 연구에서는 인간 자궁경부암세포주에서 S-allylcysteine (SAC)이 세포자멸경로에 중요한 역할을 담당하는 initiator caspase의 하나인 caspase-9와 effector caspase에 속하는 caspase-3 및 caspase-7 그리고 DNA 복구에 관여하는 poly ADP-ribose polymerase (PARP)의 발현조절에 미치는 영향과, SAC에 의한 이러한 세포자멸 및 DNA 복구 관련 단백질의 발현변화가 세포증식억제를 통한 기능적 작용을 유발하는지를 조사하였다. 단백질 발현분석 결과, 특히 50 mM의 SAC로 48시간 동안 처리하였을 경우, procaspase-3, -7, -9 및 PARP의 발현은 각각 94%, 38%, 95% 및 64% 감소되었으며, 이와 반대로 caspase-3, -7, -9 및 cleaved-PARP의 발현은 현저히 증가되었다. 또한 cell proliferation assay 결과, 20 mM 이상의 SAC 처리는 6, 12, 24 및 48시간에서 농도 및 시간 의존적인 세포증식 억제효과를 나타내었다. 이러한 결과는 SAC 처리가 자궁경부암세포의 증식을 억제하며, 이에 대한 가능한 분자적 작용기전들 중의 하나로 세포자멸과정 중 initiator caspase의 하나인 caspase-9의 활성을 유도하고 이에 따른 effector caspase인 caspase-3과 caspase-7의 활성을 촉진시킬 뿐만 아니라 DNA 복구에 관여하는 PARP의 불활성화를 초래함으로써 세포자멸 유도에 관여하는 것으로 사료된다. Our previous study suggested that S-allylcysteine (SAC) inhibits the proliferation of the human cervical cancer cell line, HeLa, at least in part through the induction of apoptosis and cell cycle arrest. To further analyze the specific molecular mechanism(s) by which SAC mediates its antiproliferative effects, this study examined the role of SAC in regulating the protein expression of initiator caspase (caspase-9), effector caspases (caspase-3 and caspase-7), and poly-ADP-ribose polymerase (PARP) in HeLa. Western blot analysis showed that when cells were treated with 50 mM SAC for 48 hr, the expression of procaspase-3, -7, and -9 and PARP was reduced by 94%, 38%, 95%, and 64%, respectively, as compared to the untreated control. In contrast, the expression of caspase-3, -7, and -9 and cleaved-PARP was markedly increased by SAC treatment. The SAC-mediated changes in the expression of these proteins were correlated with the concomitant inhibition of cellular proliferation by SAC. The cell proliferation assay showed that HeLa treatment with more than 20 mM SAC for 6-48 hr resulted in both concentration- and time-dependent inhibition of cellular proliferation. These results indicate that the SAC-induced antiproliferative effect in HeLa may be mediated at least in part through the activation of caspase-9, followed by the activation of caspase-3 and caspase-7 as well as the inactivation of PARP, thus leading to cellular apoptosis.

Effects and mechanism of bFGF on rat myoblast oxidative injury induced by hydrogen peroxide

To explore the protective role of basic fibroblast growth factor (bFGF) on attenuating hydrogen peroxide-induced injury in cultured rat myoblasts. Cultured rat myoblasts at growth phase were randomly divided into four groups (n=6):control group (control), bFGF group (bFGF), model group(H2O2) and the treatment group (bFGF + H2O2). Model group was treated with 100 μmol/L hydrogen peroxide for 4h. B-cell lymphoma-2 (Bcl-2) positive particles were detected by immunohistochemistry; Reactive oxygen species (ROS) and expression for Bcl-2 associated X protein (Bax), Bcl-2 and Cytochrome C (Cyt. C) fluorescence were observed under the invented microscope; Cyt. C and Poly ADP-ribose polymerase(PARP)protein were assessed by Western blot. Compared with control group, the myoblats in the model group showed low expression of Bcl-2 positive particles, accompanied by high expression of ROS level and Cyt. C fuorescence (P < 0.05); Compared with model group, bFGF enhanced Bcl-2 activity of the myoblasts, and significantly downregulated Cyt. C and PARP expression (P < 0.05). bFGF could attenuate oxidative injury of rat myoblasts induced by hydrogen peroxide, which mechanism might be related to enhanced Bcl-2 and reduced ROS, Cyt. C levels.

Rho-kinase signaling pathway promotes the expression of PARP to accelerate cardiomyocyte apoptosis in ischemia/reperfusion.

It has been previously reported that Rho-kinase (ROCK) and poly ADP-ribose polymerase (PARP) serve critical roles in myocardial ischemia/reperfusion (I/R) injury. Studies have additionally demonstrated that the activation of ROCK and the expression of PARP are increased in I/R. However, the effect and mechanism of the two proteins remains to be fully elucidated in I/R. In addition, whether they can be influenced by each other is unclear. In the present study, it was demonstrated that ischemia followed by reperfusion resulted in a significant increase in ROCK and PARP. In addition, Y-27632 (ROCK inhibitor) and 3-aminobenzamide (3-AB; PARP inhibitor) pretreatment rescued myocardial infarction size and cardiomyocyte apoptosis. The inhibitory role of Y-27632 was observed to be superior to that of the 3-AB group. In addition, Y-27632 and 3-AB diminished extracellular signal-related kinase (ERK) phosphorylation and the production of tumor necrosis factor α and interleukin 6. Overall, the results of the present study suggested that the inhibition of ROCK leads to reduced myocardial infarction size and cardiomyocyte apoptosis via the PARP/ERK signaling pathway.

Integrin linked kinase regulates syncytialization of BeWo trophoblast cells.

During placental development, mononuclear villous cytotrophoblast cells differentiate and fuse with the overlying syncytiotrophoblast. This process requires the dissolution of E-cadherin (CDH1)-containing adherens junctions in cytotrophoblast. Integrin linked kinase (ILK) can downregulate CDH1 through poly (ADP-ribose) polymerase 1 (PARP1) and Snail-1 (SNAI1) during epithelial-mesenchymal transition. ILK is known to be expressed in cytotrophoblast; thus, the role of a potential ILK-PARP1-SNAI1 pathway in aiding trophoblast syncytialization via the downregulation of CDH1 was examined. The spatiotemporal expression of PARP1, SNAI1, and CDH1 were determined in first and early second trimester chorionic villi, term villi, and BeWo cells by immunofluorescence analysis. PARP1 and SNAI1 were highly detectable in villous cytotrophoblast nuclei of human chorionic villi and SNAI1 expression, in particular, also persisted in syncytiotrophoblast. In BeWo cells undergoing syncytialization, PARP1 and SNAI1 increasingly localized to cell nuclei in correlation with decreased CDH1 expression. Using luciferase reporter assays, it was determined that PARP1 and SNAI1 promoter activities were significantly higher in BeWo cells during syncytialization compared to the activities in proliferating cells. Overexpression of wild type or constitutively active ILK also resulted in significantly increased PARP1 and SNAI1 promoter activities while dominant negative ILK overexpression significantly reduced promoter activities. Lastly, siRNA-mediated depletion of ILK expression in BeWo cells undergoing syncytialization resulted in significantly reduced SNAI1 expression and a significant reduction in the incidence of syncytialization correlating with increased CDH1 expression. These results demonstrate that ILK aids trophoblast syncytialization via the downregulation of CDH1, perhaps through an ILK-PARP1-SNAI1 pathway.