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Niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase inhibitor, radiosensitizes human lung and breast cancer cells.

ABSTRACT: The aim of this study was to assess niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase (PARP) inhibitor, for its ability to radiosensitize human tumor cells. Human tumor cells derived from lung, breast and prostate cancers were tested for radiosensitization by niraparib using clonogenic survival assays. Both p53 wild-type and p53-defective lines were included. The ability of niraparib to alter the repair of radiation-induced DNA double strand breaks (DSBs) was determined using detection of ?-H2AX foci and RAD51 foci. Clonogenic survival analyses indicated that micromolar concentrations of niraparib radiosensitized tumor cell lines derived from lung, breast, and prostate cancers independently of their p53 status but not cell lines derived from normal tissues. Niraparib also sensitized tumor cells to H2O2 and converted H2O2-induced single strand breaks (SSBs) into DSBs during DNA replication. These results indicate that human tumor cells are significantly radiosensitized by the potent and selective PARP-1 inhibitor, niraparib, in the in vitro setting. The mechanism of this effect appears to involve a conversion of sublethal SSBs into lethal DSBs during DNA replication due to the inhibition of base excision repair by the drug. Taken together, our findings strongly support the clinical evaluation of niraparib in combination with radiation.

SUBMITTER: Bridges KA

PROVIDER: S-EPMC4148123 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase inhibitor, radiosensitizes human lung and breast cancer cells.

Bridges Kathleen A KA Toniatti Carlo C Buser Carolyn A CA Liu Huifeng H Buchholz Thomas A TA Meyn Raymond E RE

Oncotarget 20140701 13

The aim of this study was to assess niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase (PARP) inhibitor, for its ability to radiosensitize human tumor cells. Human tumor cells derived from lung, breast and prostate cancers were tested for radiosensitization by niraparib using clonogenic survival assays. Both p53 wild-type and p53-defective lines were included. The ability of niraparib to alter the repair of radiation-induced DNA double strand breaks (DSBs) was determined using detection of ...[more]

PMID: 24970803

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Project description:Poly(ADP-ribose) polymerases (PARPs) are involved in many aspects of the cellular response to various forms of damage. PARP-1 and PARP-2, the most abundant PARPs, are central to the response to specific types of DNA damage, especially single-strand breaks. Inhibition of PARP activity may sensitize the cell to exogenous agents such as chemotherapy and radiation. In circumstances where rescue pathways are deficient, particularly the homologous recombination (HR)-directed DNA repair pathway, inhibition of PARP may result in "synthetic lethality." BRCA mutation-associated breast cancers are a paradigm of HR-directed repair deficient tumors. Early clinical trials have demonstrated significant activity of single-agent PARP inhibitors in BRCA-deficient breast and ovarian cancer. Because of phenotypic similarities between some "triple-negative" breast cancers (TNBC) and the most prevalent type of breast cancer seen in BRCA1 mutation carriers, some have hypothesized that TNBC might also be specifically sensitive to PARP inhibition. The activity of single-agent PARP inhibitors in TNBC has not been reported. One trial did suggest significant enhancement of the activity of platinum-based combination chemotherapy, without incremental toxicity. These studies indicate that PARP inhibition is an exciting new approach to the treatment of breast cancers in women with underlying BRCA mutations and possibly in sporadic cancers with defects in HR-directed repair. Future studies will be necessary to determine whether the effectiveness of PARP inhibitors in nonhereditary cancer requires an underlying HR defect or whether these agents may improve the activity of conventional chemotherapy by other means. In addition, studies will be required to determine whether PARP inhibitors may induce synthetic lethality in tumors with defects in pathways other than the BRCA-dependent DNA repair pathway. If either or both of these prove to be the case, then PARP inhibition may benefit a wide spectrum of cancer patients.

Project description:ObjectiveActivation of the constitutive nuclear and mitochondrial enzyme poly (ADP-ribose) polymerase (PARP) has been implicated in the pathogenesis of cell dysfunction, inflammation, and organ failure in various forms of critical illness. The objective of our study was to evaluate the efficacy and safety of the clinically approved PARP inhibitor olaparib in an experimental model of pancreatitis in vivo and in a pancreatic cell line subjected to oxidative stress in vitro. The preclinical studies were complemented with analysis of clinical samples to detect PARP activation in pancreatitis.MethodsMice were subjected to cerulein-induced pancreatitis; circulating mediators and circulating organ injury markers; pancreatic myeloperoxidase and malondialdehyde levels were measured and histology of the pancreas was assessed. In human pancreatic duct epithelial cells (HPDE) subjected to oxidative stress, PARP activation was measured by PAR Western blotting and cell viability and DNA integrity were quantified. In clinical samples, PARP activation was assessed by PAR (the enzymatic product of PARP) immunohistochemistry.ResultsIn male mice subjected to pancreatitis, olaparib (3 mg/kg i.p.) improved pancreatic function: it reduced pancreatic myeloperoxidase and malondialdehyde levels, attenuated the plasma amylase levels, and improved the histological picture of the pancreas. It also attenuated the plasma levels of pro-inflammatory mediators (TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-12, IP-10, KC) but not MCP-1, RANTES, or the anti-inflammatory cytokine IL-10. Finally, it prevented the slight, but significant increase in plasma blood urea nitrogen level, suggesting improved renal function. The protective effect of olaparib was also confirmed in female mice. In HPDE cells subjected to oxidative stress olaparib (1 μM) inhibited PARP activity, protected against the loss of cell viability, and prevented the loss of cellular NAD levels. Olaparib, at 1μM to 30 μM did not have any adverse effects on DNA integrity. In human pancreatic samples from patients who died of pancreatitis, increased accumulation of PAR was demonstrated.ConclusionOlaparib improves organ function and tempers the hyperinflammatory response in pancreatitis. It also protects against pancreatic cell injury in vitro without adversely affecting DNA integrity. Repurposing and eventual clinical introduction of this clinically approved PARP inhibitor may be warranted for the experimental therapy of pancreatitis.

Dataset Information

Niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase inhibitor, radiosensitizes human lung and breast cancer cells.

Publications

Niraparib (MK-4827), a novel poly(ADP-Ribose) polymerase inhibitor, radiosensitizes human lung and breast cancer cells.

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