Unconventional activation of PRKDC by TNF-α: deciphering its crucial role in Th1-mediated inflammation beyond DNA repair as part of the DNA-PK complex.

BACKGROUND: The DNA-dependent protein kinase (DNA-PK) complex comprises a catalytic (PRKDC) and two requisite DNA-binding (Ku70/Ku80) subunits. The role of the complex in repairing double-stranded DNA breaks (DSBs) is established, but its role in inflammation, as a complex or individual subunits, remains elusive. While only ~ 1% of PRKDC is necessary for DNA repair, we reported that partial inhibition blocks asthma in mice without causing SCID. METHODS: We investigated the central role of PRKDC in inflammation and its potential association with DNA repair. We also elucidated the relationship between inflammatory cytokines (e.g., TNF-α) and PRKDC by analyzing its connections to inflammatory kinases. Human cell lines, primary human endothelial cells, and mouse fibroblasts were used to conduct the in vitro studies. For animal studies, LPS- and oxazolone-induced mouse models of acute lung injury (ALI) and delayed-type hypersensitivity (DHT) were used. Wild-type, PRKDC+/-, or Ku70+/- mice used in this study. RESULTS: A ~ 50% reduction in PRKDC markedly blocked TNF-α-induced expression of inflammatory factors (e.g., ICAM-1/VCAM-1). PRKDC regulates Th1-mediated inflammation, such as DHT and ALI, and its role is highly sensitive to inhibition achieved by gene heterozygosity or pharmacologically. In endothelial or epithelial cells, TNF-α promoted rapid PRKDC phosphorylation in a fashion resembling that induced by, but independent of, DSBs. Ku70 heterozygosity exerted little to no effect on ALI in mice, and whatever effect it had was associated with a specific increase in MCP-1 in the lungs and systemically. While Ku70 knockout blocked VP-16-induced PRKDC phosphorylation, it did not prevent TNF-α - induced phosphorylation of the kinase, suggesting Ku70 dispensability. Immunoprecipitation studies revealed that PRKDC transiently interacts with p38MAPK. Inhibition of p38MAPK blocked TNF-α-induced PRKDC phosphorylation. Direct phosphorylation of PRKDC by p38MAPK was demonstrated using a cell-free system. CONCLUSIONS: This study presents compelling evidence that PRKDC functions independently of the DNA-PK complex, emphasizing its central role in Th1-mediated inflammation. The distinct functionality of PRKDC as an individual enzyme, its remarkable sensitivity to inhibition, and its phosphorylation by p38MAPK offer promising therapeutic opportunities to mitigate inflammation while sparing DNA repair processes. These findings expand our understanding of PRKDC biology and open new avenues for targeted anti-inflammatory interventions.

Promotion of a synthetic degradation of activated STAT6 by PARP-1 inhibition: roles of poly(ADP-ribosyl)ation, calpains and autophagy.

BACKGROUND: We reported that PARP-1 regulates genes whose products are crucial for asthma, in part, by controlling STAT6 integrity speculatively through a calpain-dependent mechanism. We wished to decipher the PARP-1/STAT6 relationship in the context of intracellular trafficking and promoter occupancy of the transcription factor on target genes, its integrity in the presence of calpains, and its connection to autophagy. METHODS: This study was conducted using primary splenocytes or fibroblasts derived from wild-type or PARP-1-/- mice and Jurkat T cells to mimic Th2 inflammation. RESULTS: We show that the role for PARP-1 in expression of IL-4-induced genes (e.g. gata-3) in splenocytes did not involve effects on STAT6 phosphorylation or its subcellular trafficking, rather, it influenced its occupancy of gata-3 proximal and distal promoters in the early stages of IL-4 stimulation. At later stages, PARP-1 was crucial for STAT6 integrity as its inhibition, pharmacologically or by gene knockout, compromised the fate of the transcription factor. Calpain-1 appeared to preferentially degrade JAK-phosphorylated-STAT6, which was blocked by calpastatin-mediated inhibition or by genetic knockout in mouse fibroblasts. The STAT6/PARP-1 relationship entailed physical interaction and modification by poly(ADP-ribosyl)ation independently of double-strand-DNA breaks. Poly(ADP-ribosyl)ation protected phosphorylated-STAT6 against calpain-1-mediated degradation. Additionally, our results show that STAT6 is a bonafide substrate for chaperone-mediated autophagy in a selective and calpain-dependent manner in the human Jurkat cell-line. The effects were partially blocked by IL-4 treatment and PARP-1 inhibition. CONCLUSIONS: The results demonstrate that poly(ADP-ribosyl)ation plays a critical role in protecting activated STAT6 during Th2 inflammation, which may be synthetically targeted for degradation by inhibiting PARP-1.

Targeting the Cbl-b-Notch1 axis as a novel immunotherapeutic strategy to boost CD8+ T-cell responses.

A critical feature of cancer is the ability to induce immunosuppression and evade immune responses. Tumor-induced immunosuppression diminishes the effectiveness of endogenous immune responses and decreases the efficacy of cancer immunotherapy. In this study, we describe a new immunosuppressive pathway in which adenosine promotes Casitas B-lineage lymphoma b (Cbl-b)-mediated Notch1 degradation, causing suppression of CD8+ T-cells effector functions. Genetic knockout and pharmacological inhibition of Cbl-b prevents Notch1 degradation in response to adenosine and reactivates its signaling. Reactivation of Notch1 results in enhanced CD8+ T-cell effector functions, anti-cancer response and resistance to immunosuppression. Our work provides evidence that targeting the Cbl-b-Notch1 axis is a novel promising strategy for cancer immunotherapy.

Nuclear interaction of Arp2/3 complex and BRAFV600E promotes aggressive behavior and vemurafenib resistance of thyroid cancer.

The presence of mutant BRAF V600E correlates with the risk of recurrence in papillary thyroid cancer (PTC) patients. However, not all PTC patients with BRAF V600E are associated with poor prognosis. Thus, understanding the mechanisms by which certain PTC patients with nuclear BRAF V600E become aggressive and develop resistance to a selective BRAF inhibitor, PLX-4032, is urgently needed. The effect of nuclear localization of BRAFV600E using in vitro studies, xenograft mouse-model and human tissues was evaluated. PTC cells harboring a nuclear localization signal (NLS) of BRAFV600E were established and examined in nude mice implanted with TPC1-NLS-BRAFV600E cells followed by PLX-4032 treatment. Immunohistochemical (IHC) analysis was performed on 100 PTC specimens previously confirmed that they have BRAFV600E mutations. Our results demonstrate that 21 of 100 (21%) PTC tissues stained with specific BRAFV600E antibody had nuclear staining with more aggressive features compared to their cytosolic counterparts. In vitro studies show that BRAFV600E is transported between the nucleus and the cytosol through CRM1 and importin (α/ß) system. Sequestration of BRAFV600E in the cytosol sensitized resistant cells to PLX-4032, whereas nuclear BRAFV600E was associated with aggressive phenotypes and developed drug resistance. Proteomic analysis revealed Arp2/3 complex members, actin-related protein 2 (ACTR2 aliases ARP2) and actin-related protein 3 (ACTR3 aliases ARP3), as the most enriched nuclear BRAFV600E partners. ACTR3 was highly correlated to lymph node stage and extrathyroidal extension and was validated with different functional assays. Our findings provide new insights into the clinical utility of the nuclear BRAFV600E as a prognostic marker for PTC aggressiveness and determine the efficacy of selective BRAFV600E inhibitor treatment which opens new avenues for future treatment options.

Combination of Tipifarnib and Sunitinib Overcomes Renal Cell Carcinoma Resistance to Tyrosine Kinase Inhibitors via Tumor-Derived Exosome and T Cell Modulation.

BACKGROUND: Tyrosine kinase inhibitors (TKI) were initially demonstrated as an efficacious treatment for renal cell carcinoma (RCC). However, after a median treatment length of 14 months, a vast majority of patients develop resistance. This study analyzed a combination therapy of tipifarnib (Tipi) + sunitinib that targeted exosome-conferred drug resistance. METHODS: 786-O, 786-O-SR (sunitinib resistant), A498, A498-SR, Caki-2, Caki-2-SR, and 293T cells were cultured. Exosomes were collected using differential ultracentrifugation. Cell proliferation, Jurkat T cell immune assay, and immunoblot analysis were used for downstream analysis. RESULTS: SR exosomes treatment displayed a cytotoxic effect on immune cells. This cytotoxic effect was associated with increased expression of PD-L1 on SR exosomes when compared to sunitinib-sensitive (SS) exosomes. Additionally, Tipi treatment downregulated PD-L1 expression on exosomes derived from SR cell lines. Tipi's ability to downregulate PD-L1 in exosomes has a significant application within patients. Exosomes collected from patients with RCC showed increased PD-L1 expression over subjects without RCC. Next, exosome concentrations were then compared after Tipi treatment, with all SS cell lines displaying an even greater reduction. On immunoblot assay, 293T cells showed a dose-dependent increase in Alix with no change in either nSMase or Rab27a. Conversely, all the SS and SR cell lines displayed a decrease in all three markers. After a cell proliferation employed a 48-h treatment on all SS and SR cell lines, the drug combination displayed synergistic ability to decrease tumor growth. CONCLUSIONS: Tipifarnib attenuates both the exosome endosomal sorting complex required for endosomal sorting complex required for transport (ESCRT)-dependent and ESCRT-independent pathways, thereby blocking exosome biogenesis and secretion as well as downregulating PD-L1 on SS and SR cells.

Differential effects of poly(ADP ribose) polymerase inhibitor-based metronomic therapy on programmed death-ligand 1 and matrix-associated factors in human myeloid cells.

We recently showed that while partial poly(ADP-ribose) polymerase (PARP)-1 inhibition with a low metronomic sub-half-maximal inhibitory concentration/dose (IC50) of olaparib provides superior protection against colon cancer in mice compared to complete inhibition by blocking the suppressive function of myeloid-derived suppressor cells (MDSCs) and synergizing with anti-program cell death (PD)-1-based immunotherapy. Here, we examined whether PARP inhibitors (PARPi) exert effects on human myeloid cells that alter T cell function (e.g. PD-ligand (L)1) or metastasis/tumor microenvironment-associated factors (e.g. tissue inhibitor of matrix metalloproteinases (MMPs) (TIMP)-2 and MMPs activity). We show that olaparib-based metronomic therapy induced a marginal increase in PD-L1 expression in MDSCs-enriched cells, decreased its expression in dendritic cells (DCs)-enriched cells, and caused little to no effect on macrophage-enriched cells. Interestingly, MDSCs-enriched cells also expressed low levels of PARP-1 while dendritic cells and macrophages expressed high levels of the protein. Bone marrow progenitors expressed no PD-L1; however, when differentiated into MDSCs, the expression was high displaying higher glycosylation levels compared to those observed in peripheral blood mononuclear cells (PBMCs)-derived cells. Contrary to reported effects on cancer cells, the sub-IC50 or moderate olaparib concentration caused substantial decrease in PD-L1. A sub-IC50 concentration of other clinically used PARPi (rucaparib, niraparib, and talazoparib) as well as the failed PARPi, iniparib, exerted similar effects. Furthermore, PARPi-based metronomic therapy reprogramed myeloid cells with the potential to stabilize intratumoral matrix by increasing secreted-TIMP-2 with a differential reduction in MMP-2/MMP-9 activity. Thus, PARPi-based metronomic therapy may promote functional changes in myeloid cells that provide an additional rationale for combining it with immunotherapy. Our results also provide new opportunities for iniparib in cancer therapy.

Repurposing ketoconazole as an exosome directed adjunct to sunitinib in treating renal cell carcinoma.

Renal Cell Carcinoma (RCC) is the most common form of kidney cancer, with clear cell RCC (ccRCC) representing about 85% of all RCC tumors. There are limited curable treatments available for metastatic ccRCC because this disease is unresponsive to conventional targeted systemic pharmacotherapy. Exosomes (Exo) are small extracellular vesicles (EVs) secreted from cancer cells with marked roles in tumoral signaling and pharmacological resistance. Ketoconazole (KTZ) is an FDA approved anti-fungal medication which has been shown to suppress exosome biogenesis and secretion, yet its role in ccRCC has not been identified. A time-course, dose-dependent analysis revealed that KTZ selectively decreased secreted Exo in tumoral cell lines. Augmented Exo secretion was further evident by decreased expression of Exo biogenesis (Alix and nSMase) and secretion (Rab27a) markers. Interestingly, KTZ-mediated inhibition of Exo biogenesis was coupled with inhibition of ERK1/2 activation. Next, selective inhibitors were employed and showed ERK signaling had a direct role in mediating KTZ's inhibition of exosomes. In sunitinib resistant 786-O cells lines, the addition of KTZ potentiates the efficacy of sunitinib by causing Exo inhibition, decreased tumor proliferation, and diminished clonogenic ability of RCC cells. Our findings suggest that KTZ should be explored as an adjunct to current RCC therapies.

Acute effect of inhaled iloprost on exercise dynamic hyperinflation in COPD patients: A randomized crossover study.

BACKGROUND AND OBJECTIVE: We tested whether the prostacyclin analog inhaled iloprost modulates dead space, dynamic hyperinflation (DH), and systemic inflammation/oxidative stress during maximal exercise in subjects with chronic obstructive pulmonary disease (COPD) who were not selected based on pulmonary hypertension (PH). METHODS: Twenty-four COPD patients with moderate-severe obstruction (age 59 ± 7 years, FEV1 53 ± 13% predicted) participated in a randomized, double-blind, placebo-controlled crossover trial. Each subject received a single nebulized dose of 5.0 µg iloprost or placebo on non-consecutive days followed by maximal cardiopulmonary exercise tests. The primary outcome was DH quantified by end-expiratory lung volume/total lung capacity ratio (EELV/TLC) at metabolic isotime. RESULTS: Inhaled iloprost was well-tolerated and reduced submaximal alveolar dead-space fraction but did not significantly reduce DH (0.70 ± 0.09 vs 0.69 ± 0.07 following placebo and iloprost, respectively, p = 0.38). Maximal exercise time (9.1 ± 2.3 vs 9.3 ± 2.2 min, p = 0.31) and peak oxygen uptake (17.4 ± 6.3 vs 17.9 ± 6.9 mL/kg/min, p = 0.30) were not significantly different following placebo versus iloprost. CONCLUSIONS: A single dose of inhaled iloprost was safe and reduced alveolar dead space fraction; however, it was not efficacious in modulating DH or improving exercise capacity in COPD patients who were not selected for the presence of PH.

Targeting PARP-1 with metronomic therapy modulates MDSC suppressive function and enhances anti-PD-1 immunotherapy in colon cancer.

BACKGROUND: Poly(ADP-ribose) polymerase (PARP) inhibitors (eg, olaparib) are effective against BRCA-mutated cancers at/near maximum tolerated doses by trapping PARP-1 on damaged chromatin, benefitting only small patient proportions. The benefits of targeting non-DNA repair aspects of PARP with metronomic doses remain unexplored. METHODS: Colon epithelial cells or mouse or human bone marrow (BM)-derived-myeloid-derived suppressor cells (MDSCs) were stimulated to assess the effect of partial PARP-1 inhibition on inflammatory gene expression or immune suppression. Mice treated with azoxymethane/four dextran-sulfate-sodium cycles or APCMin/+ mice bred into PARP-1+/- or treated with olaparib were used to examine the role of PARP-1 in colitis-induced or spontaneous colon cancer, respectively. Syngeneic MC-38 cell-based (microsatellite instability, MSIhigh) or CT-26 cell-based (microsatellite stable, MSS) tumor models were used to assess the effects of PARP inhibition on host responses and synergy with anti-Programmed cell Death protein (PD)-1 immunotherapy. RESULTS: Partial PARP-1 inhibition, via gene heterozygosity or a moderate dose of olaparib, protected against colitis-mediated/APCMin -mediated intestinal tumorigenesis and APCMin -associated cachexia, while extensive inhibition, via gene knockout or a high dose of olaparib, was ineffective or aggravating. A sub-IC50-olaparib dose or PARP-1 heterozygosity was sufficient to block tumorigenesis in a syngeneic colon cancer model by modulating the suppressive function, but not intratumoral migration or differentiation, of MDSCs, with concomitant increases in intratumoral T cell function and cytotoxicity, as assessed by granzyme-B/interferon-γ levels. Adoptive transfer of WT-BM-MDSCs abolished the protective effects of PARP-1 heterozygosity. The mechanism of MDSC modulation involved a reduction in arginase-1/inducible nitric oxide synthase/cyclo-oxygenase-2, but independent of PARP-1 trapping on chromatin. Although a high-concentration olaparib or the high-trapping PARP inhibitor, talazoparib, activated stimulator of interferon gene (STING) in BRCA-proficient cells and induced DNA damage, sub-IC50 concentrations of either drug failed to induce activation of the dsDNA break sensor. STING expression appeared dispensable for MDSC suppressive function and was not strictly required for olaparib-mediated effects. Ironically, STING activation blocked human and mouse MDSC function with no additive effects with olaparib. A metronomic dose of olaparib was highly synergistic with anti-PD-1-based immunotherapy, leading to eradication of MSIhigh or reduction of MSS tumors in mice. CONCLUSIONS: These results support a paradigm-shifting concept that expands the utility of PARP inhibitor and encourage testing metronomic dosing of PARP inhibitor to enhance the efficacy of checkpoint inhibitor-based immunotherapies in cancer.

PARP-1 Is Critical for Recruitment of Dendritic Cells to the Lung in a Mouse Model of Asthma but Dispensable for Their Differentiation and Function.

Dendritic cells (DCs) are critical in asthma and many other immune diseases. We previously demonstrated a role for PARP-1 in asthma. Evidence on PARP-1 playing a role in Th2-associated DC function is not clear. In this study, we examined whether PARP-1 is critical for DC differentiation and function using bone marrow progenitors and their migration to the lung in an ovalbumin-based mouse model of asthma. Results show that changes in PARP-1 levels during GM-CSF-induced DC differentiation from bone marrow progenitors were cyclic and appear to be part of an array of changes that included STAT3/STAT5/STAT6/GRAIL/RAD51. Interestingly, PARP-1 gene deletion affected primarily STAT6 and γH2AX. PARP-1 inhibition significantly reduced the migration of DCs to the lungs of ovalbumin-challenged mice, which was associated with a concomitant reduction in lung levels of the adhesion molecule VCAM-1. The requirement of PARP-1 for VCAM-1 expression was confirmed using endothelial and lung smooth muscle cells. PARP-1 expression and activity were also required for VCAM-1 in differentiated DCs. An assessment of CD11b+/CD11c+/MHCIIhigh DCs in spleens and lymph nodes of OVA-sensitized mice revealed that PARP-1 inhibition genetically or by olaparib exerted little to no effect on DC differentiation, percentage of CD80+/CD86+/CD40+-expressing cells, or their capacity to promote proliferation of ovalbumin-primed (OTII) CD4+ T cells. These findings were corroborated using GM-CSF-induced differentiation of DCs from the bone marrow. Surprisingly, the PARP-1-/- DCs exhibited a higher intrinsic capacity to induce OTII CD4+ T cell proliferation in the absence of ovalbumin. Overall, our results show that PARP-1 plays little to no role in DC differentiation and function and that the protective effect of PARP-1 inhibition against asthma is associated with a prevention of DC migration to the lung through a reduction in VCAM-1 expression. Given the current use of PARP inhibitors (e.g., olaparib) in the clinic, the present results may be of interest for the relevant therapies.

Microparticles in systemic sclerosis: Potential pro-inflammatory mediators and pulmonary hypertension biomarkers.

BACKGROUND AND OBJECTIVE: Endothelial microparticles (EMP) are submicron vesicles released from endothelial cells. We aimed to determine the utility of EMP as biomarkers of pulmonary arterial hypertension (PAH) in systemic sclerosis (SSc) patients and the pathogenic role of microparticles (MP) in vascular inflammation. METHODS: Levels of EMP (CD144+, CD31+, CD62E+ and CD143+) were compared between three groups (10 SSc patients with PAH, 10 SSc patients without pulmonary hypertension (no-PH) and 10 healthy age- and sex-matched controls). Human pulmonary artery endothelial cells (HPAEC) were exposed in vitro to MP obtained from SSc patients or healthy controls, and levels of cytokines and inflammatory adhesion molecules were compared. RESULTS: CD144+ EMP were significantly higher in the SSc-PAH group compared to either the SSc-no PH or healthy controls (diagnostic accuracy 80%, P = 0.02). Compared to controls, SSc patients had higher CD31+/CD62E+ ratios, indicating larger contributions of apoptosis to EMP release (P = 0.04). Patients with limited SSc had significantly higher levels of CD143+ EMP compared to those with diffuse subtype (P = 0.008). When HPAEC were exposed to MP from SSc patients, there was a significant increase in inflammatory cytokines and adhesion molecules. Interestingly, exposure to healthy control MP caused a reduction in inflammatory markers. CONCLUSION: EMP (particularly CD144+) are promising biomarkers of PAH in SSc but require further study. MP isolated from SSc patients induced an increase in endothelial cell inflammation and may be an important pathogenic factor in SSc.

Sulfated non-anticoagulant heparin blocks Th2-induced asthma by modulating the IL-4/signal transducer and activator of transcription 6/Janus kinase 1 pathway.

BACKGROUND: The efficacy of heparins and low-MW-heparins (LMWH) against human asthma has been known for decades. However, the clinical utility of these compounds has been hampered by their anticoagulant properties. Much effort has been put into harnessing the anti-inflammatory properties of LMWH but none have been used as therapy for asthma. Sulfated-non-anticoagulant heparin (S-NACH) is an ultra-LMWH with no systemic anticoagulant effects. OBJECTIVE: The present study explored the potential of S-NACH in blocking allergic asthma and examined the potential mechanism by which it exerts its effects. METHODS: Acute and chronic ovalbumin-based mouse models of asthma, splenocytes, and a lung epithelial cell line were used. Mice were challenged with aerosolized ovalbumin and administered S-NACH or saline 30 min after each ovalbumin challenge. RESULTS: Sulfated-non-anticoagulant heparin administration in mice promoted a robust reduction in airway eosinophilia, mucus production, and airway hyperresponsiveness even after chronic repeated challenges with ovalbumin. Such effects were linked to suppression of Th2 cytokines IL-4/IL-5/IL-13/GM-CSF and ovalbumin-specific IgE without any effect on IFN-γ. S-NACH also reduced lung fibrosis in mice that were chronically-exposed to ovalbumin. These protective effects of S-NACH may be attributed to modulation of the IL-4/JAK1 signal transduction pathway through an inhibition of STAT6 phosphorylation and a subsequent inhibition of GATA-3 and inducible NO synthase expression. The effect of the drug on STAT6 phosphorylation coincided with a reduction in JAK1 phosphorylation upon IL-4 treatment. The protective effects of S-NACH treatment was associated with reduction of the basal expression of the two isoforms of arginase ARG1 and ARG2 in lung epithelial cells. CONCLUSIONS: Our study demonstrates that S-NACH constitutes an opportunity to benefit from the well-known anti-asthma properties of heparins/LMWH while bypassing the risk of bleeding. Our results show, for the first time, that such anti-asthma effects may be associated with reduction of the IL-4/JAK1/STAT6 pathway.

Molecular and Structural Traits of Insulin Receptor Substrate 1/LC3 Nuclear Structures and Their Role in Autophagy Control and Tumor Cell Survival.

Insulin receptor substrate 1 (IRS-1) is a common cytosolic adaptor molecule involved in signal transduction from insulin and insulin-like growth factor I (IGF-I) receptors. IRS-1 can also be found in the nucleus. We report here a new finding of unique IRS-1 nuclear structures, which we observed initially in glioblastoma biopsy specimens and glioblastoma xenografts. These nuclear structures can be reproduced in vitro by the ectopic expression of IRS-1 cDNA cloned in frame with the nuclear localization signal (NLS-IRS-1). In these structures, IRS-1 localizes at the periphery, while the center harbors a key autophagy protein, LC3. These new nuclear structures are highly dynamic, rapidly exchange IRS-1 molecules with the surrounding nucleoplasm, disassemble during mitosis, and require a growth stimulus for their reassembly and maintenance. In tumor cells engineered to express NLS-IRS-1, the IRS-1/LC3 nuclear structures repress autophagy induced by either amino acid starvation or rapamycin treatment. In this process, IRS-1 nuclear structures sequester LC3 inside the nucleus, possibly preventing its cytosolic translocation and the formation of new autophagosomes. This novel mechanism provides a quick and reversible way of inhibiting autophagy, which could counteract autophagy-induced cancer cell death under severe stress, including anticancer therapies.

Opportunities for the repurposing of PARP inhibitors for the therapy of non-oncological diseases.

The recent clinical availability of the PARP inhibitor olaparib (Lynparza) opens the door for potential therapeutic repurposing for non-oncological indications. Considering (a) the preclinical efficacy data with PARP inhibitors in non-oncological diseases and (b) the risk-benefit ratio of treating patients with a compound that inhibits an enzyme that has physiological roles in the regulation of DNA repair, we have selected indications, where (a) the severity of the disease is high, (b) the available therapeutic options are limited, and (c) the duration of PARP inhibitor administration could be short, to provide first-line options for therapeutic repurposing. These indications are as follows: acute ischaemic stroke; traumatic brain injury; septic shock; acute pancreatitis; and severe asthma and severe acute lung injury. In addition, chronic, devastating diseases, where alternative therapeutic options cannot halt disease development (e.g. Parkinson's disease, progressive multiple sclerosis or severe fibrotic diseases), should also be considered. We present a preclinical and clinical action plan for the repurposing of PARP inhibitors. LINKED ARTICLES: This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Bortezomib sensitizes thyroid cancer to BRAF inhibitor in vitro and in vivo.

Although overall survival rate for patients with thyroid cancer (TC) is high, there is an alarming 10-year recurrence rate of up to 30% conferring a ~50% survival among these high-risk patients. The BRAFV600E mutation is estimated to be present in over 50% of papillary thyroid cancer (PTC) cases besides being associated with carcinogenesis and poor prognosis. We assessed the status of NF-κB, Ki-67, cyclin D1 and BRAFV600E in TC tissues and TC cell lines using immunohistochemistry and Western blot analysis. Concurrently, we evaluated the outcomes of combined targeting of the proteasome pathway in addition to selective BRAF inhibitors in cases of PTC. In this study, BRAFV600E-bearing TC cells were treated with BRAFV600E inhibitor, Vemurafenib alone or in combination with the proteasome inhibitor, Bortezomib. The combination of both drugs showed synergistic effects as evidenced by cell growth inhibition (P < 0.05), increased G2-phase cell cycle arrest and induced apoptosis (P < 0.05). In our TC xenograft model, the combination of Vemurafenib and Bortezomib significantly reduced tumor size (P < 0.05) and expression of the markers of cell growth and proliferation, Ki-67 and cyclin D1 (P < 0.001), when compared to monotherapy. Further analysis demonstrated that treatment with Bortezomib sensitized TC cells to Vemurafenib via mitochondrial dysregulation and apoptosis of TC cells, as evidenced by the increase in the expression of p53, Noxa protein, the loss of mitochondrial membrane potential, cytochrome c release and Poly (ADP-ribose) polymerase cleavage. Our results demonstrate a strong clinical potential for the combination of the Bortezomib and the BRAF inhibitor Vemurafenib as an efficient therapeutic approach for the treatment of TC.

Immunohistochemistry as an accurate tool for evaluating BRAF-V600E mutation in 130 samples of papillary thyroid cancer.

BACKGROUND: BRAFV600E mutation has been investigated by immunohistochemistry and has shown high sensitivity and specificity. We aim to investigate the accuracy of immunohistochemistry versus molecular testing of BRAFV600E in papillary thyroid cancer using a large number of polymerase chain reaction-positive BRAFV600E papillary thyroid cancer tissues. METHODS: We stained 130 formalin-fixed papillary thyroid cancer specimens using the VE1 antibody: 100 BRAFV600E positive and 30 BRAFV600E negative confirmed by PCR. The sensitivity, specificity, and predictive values of the antibody were assessed. RESULTS: Immunohistochemistry of BRAFV600E showed 98.0% sensitivity, 93.3% specificity, and positive and negative predictive values of 98.0% and 93.3%, respectively. Of 100 patients with BRAFV600E PCR-positive samples, 97 (97.0%) had cytoplasmic weak (4.0%), moderate (17.0%), and strong (76.0%) immunostaining. In BRAFV600E PCR-negative samples, cytoplasmic staining was not detected in 93.3% (28/30) of papillary thyroid cancer tissues. The receiver operating characteristic curve demonstrated a high validity and comparable immunohistochemistry method (area under the curve = 98.8%) compared with PCR testing. CONCLUSION: The use of VE1 immunohistochemistry for the detection of BRAFV600E in papillary thyroid cancer tissues is a clinically applicable method with high specificity, sensitivity, and positive and negative predictive values. The reliable use of BRAFV600E immunohistochemistry should promulgate the routine use of this method for BRAFV600E detection in papillary thyroid cancer tissues.

PARP inhibition protects against alcoholic and non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Mitochondrial dysfunction, oxidative stress, inflammation, and metabolic reprograming are crucial contributors to hepatic injury and subsequent liver fibrosis. Poly(ADP-ribose) polymerases (PARP) and their interactions with sirtuins play an important role in regulating intermediary metabolism in this process. However, there is little research into whether PARP inhibition affects alcoholic and non-alcoholic steatohepatitis (ASH/NASH). METHODS: We investigated the effects of genetic deletion of PARP1 and pharmacological inhibition of PARP in models of early alcoholic steatohepatitis, as well as on Kupffer cell activation in vitro using biochemical assays, real-time PCR, and histological analyses. The effects of PARP inhibition were also evaluated in high fat or methionine and choline deficient diet-induced steatohepatitis models in mice. RESULTS: PARP activity was increased in livers due to excessive alcohol intake, which was associated with decreased NAD+ content and SIRT1 activity. Pharmacological inhibition of PARP restored the hepatic NAD+ content, attenuated the decrease in SIRT1 activation and beneficially affected the metabolic-, inflammatory-, and oxidative stress-related alterations due to alcohol feeding in the liver. PARP1-/- animals were protected against alcoholic steatohepatitis and pharmacological inhibition of PARP or genetic deletion of PARP1 also attenuated Kupffer cell activation in vitro. Furthermore, PARP inhibition decreased hepatic triglyceride accumulation, metabolic dysregulation, or inflammation and/or fibrosis in models of NASH. CONCLUSION: Our results suggests that PARP inhibition is a promising therapeutic strategy in steatohepatitis with high translational potential, considering the availability of PARP inhibitors for clinical treatment of cancer. LAY SUMMARY: Poly(ADP-ribose) polymerases (PARP) are the most abundant nuclear enzymes. The PARP inhibitor olaparib (Lynparza) is a recently FDA-approved therapy for cancer. This study shows that PARP is overactivated in livers of subjects with alcoholic liver disease and that pharmacological inhibition of this enzyme with 3 different PARP inhibitors, including olaparib, attenuates high fat or alcohol induced liver injury, abnormal metabolic alteration, fat accumulation, inflammation and/or fibrosis in preclinical models of liver disease. These results suggest that PARP inhibition is a promising therapeutic strategy in the treatment of alcoholic and non-alcoholic liver diseases.

Potential of Inducible Nitric Oxide Synthase as a Therapeutic Target for Allergen-Induced Airway Hyperresponsiveness: A Critical Connection to Nitric Oxide Levels and PARP Activity.

Although expression of inducible NO synthase (iNOS) in the lungs of asthmatics and associated nitrosative damage are established, iNOS failed as a therapeutic target for blocking airway hyperresponsiveness (AHR) and inflammation in asthmatics. This dichotomy calls for better strategies with which the enzyme is adequately targeted. Here, we confirm iNOS expression in the asthmatic lung with concomitant protein nitration and poly(ADP-ribose) polymerase (PARP) activation. We show, for the first time, that iNOS is highly expressed in peripheral blood mononuclear cells (PBMCs) of asthmatics with uncontrolled disease, which did not correspond to protein nitration. Selective iNOS inhibition with L-NIL protected against AHR upon acute, but not chronic, exposure to ovalbumin or house dust mite (HDM) in mice. Supplementation of NO by nitrite administration significantly blocked AHR in chronically HDM-exposed mice that were treated with L-NIL. Protection against chronic HDM exposure-induced AHR by olaparib-mediated PARP inhibition may be associated with the partial but not the complete blockade of iNOS expression. Indeed, L-NIL administration prevented olaparib-mediated protection against AHR in chronically HDM-exposed mice. Our study suggests that the amount of iNOS and NO are critical determinants in the modulation of AHR by selective iNOS inhibitors and renews the potential of iNOS as a therapeutic target for asthma.

Treatment with intranasal iloprost reduces disease manifestations in a murine model of previously established COPD.

Pulmonary endothelial prostacyclin appears to be involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). The effect of treatment with a prostacyclin analog in animal models of previously established COPD is unknown. We evaluated the short- and long-term effect of iloprost on inflammation and airway hyperresponsiveness (AHR) in a murine model of COPD. Nineteen mice were exposed to LPS/elastase, followed by either three doses of intranasal iloprost or saline. In the long-term treatment experiment, 18 mice were exposed to LPS/elastase and then received 6 wk of iloprost or were left untreated as controls. In the short-term experiment, iloprost did not change AHR but significantly reduced serum IL-5 and IFN-γ. Long-term treatment with iloprost for both 2 and 6 wk significantly improved AHR. After 6 wk of iloprost, there was a reduction in bronchoalveolar lavage (BALF) neutrophils, serum IL-1ß (30.0 ± 9.2 vs. 64.8 ± 7.4 pg/ml, P = 0.045), IL-2 (36.5 ± 10.6 vs. 83.8 ± 0.4 pg/ml, P = 0.01), IL-10 (75.7 ± 9.3 vs. 96.5 ± 3.5 pg/ml, P = 0.02), and nitrite (15.1 ± 5.4 vs. 30.5 ± 10.7 µmol, P = 0.01). Smooth muscle actin (SMA) in the lung homogenate was also significantly reduced after iloprost treatment (P = 0.02), and SMA thickness was reduced in the small and medium blood vessels after iloprost (P < 0.001). In summary, short- and long-term treatment with intranasal iloprost significantly reduced systemic inflammation in an LPS/elastase COPD model. Long-term iloprost treatment also reduced AHR, serum nitrite, SMA, and BALF neutrophilia. These data encourage future investigations of prostanoid therapy as a novel treatment for COPD patients.