Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.30 (PARP)
 13,611 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly(ADP-ribose) polymerase-1 (PARP-1) facilitates DNA single-strand break-base excision repair to maintain genomic stability. Inhibition or loss of PARP activity leads to a recombinogenic phenotype characterized by increased sister chromatid exchange. Deficiency in homologous recombination (HR) owing to loss of BRCA1 or BRCA2 is associated with hereditary cancers of the breast, ovary, pancreas and prostate. We investigated the therapeutic potential of PARP inhibitors in HR and BRCA2-defective cells. We exposed cells defective in the HR component XRCC3 (irs1SF) and BRCA2 (V-C8) and their parental (AA8, V79) or deficiency corrected (CXR3, V-C8+B2) cells to the PARP inhibitors NU1025 and AG14361. Mice bearing BRCA2-deficient and BRCA2-proficient tumours were treated with AG14361. All HR-defective cells were hypersensitive to normally non-cytotoxic concentrations of PARP inhibitors. Cells lacking BRCA2 were 20 times more sensitive to PARP inhibitor-induced cytotoxicity. Three out of five BRCA2-defective xenografts responded to the potent PARP inhibitor, AG14361, and one tumour regressed completely, compared with non-responses in the BRCA2-proficient tumours treated with AG14361 or any mice treated with vehicle control. Untreated PARP-1(-/-) mouse embryo fibroblasts (MEFs) accumulated more DNA double-strand breaks than did PARP-1(+/+) MEFs. We believe the underlying cytotoxic mechanism is due to PARP inhibitor-mediated suppression of repair of DNA single-strand breaks, which are converted to DNA double-strand breaks at replication. These replication-associated double-strand breaks, which are normally repaired by HR, become cytotoxic in cells defective in HR. Using a DNA repair inhibitor alone to selectively kill a tumour represents an exciting new concept in cancer therapy.
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PMID:Exploiting the Achilles heel of cancer: the therapeutic potential of poly(ADP-ribose) polymerase inhibitors in BRCA2-defective cancer. 1882

Synthetic lethality is an attractive strategy for the design of novel therapies for cancer. Using this approach we have previously demonstrated that inhibition of the DNA repair protein, PARP1, is synthetically lethal with deficiency of either of the breast cancer susceptibility proteins, BRCA1 and BRCA2. This observation is most likely explained by the inability of BRCA deficient cells to repair DNA damage by homologous recombination (HR) and has led to the clinical trials of potent PARP inhibitors for the treatment of BRCA mutation-associated cancer. To identify further determinants of PARP inhibitor response, we took a high-throughput genetic approach. We tested each of the genes recognised as having a role in DNA repair using short-interfering RNA (siRNA) and assessed the sensitivity of siRNA transfected cells to a potent PARP inhibitor, KU0058948. The validity of this approach was confirmed by the identification of known genetic determinants of PARP inhibitor sensitivity, including genes involved in HR. Novel determinants of PARP inhibitor response were also identified, including the transcription coupled DNA repair (TCR) proteins DDB1 and XAB2. These results suggest that DNA repair pathways other than HR may determine sensitivity to PARP inhibitors and highlight the likelihood that ostensibly distinct DNA repair pathways cooperate to maintain genomic stability and cellular viability. Furthermore, the identification of these novel determinants may eventually guide the optimal use of PARP inhibitors in the clinic.
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PMID:A high-throughput RNA interference screen for DNA repair determinants of PARP inhibitor sensitivity. 1883 51

The abundant nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1), represents an important novel target in cancer therapy. PARP-1 is essential to the repair of DNA single-strand breaks via the base excision repair pathway. Inhibitors of PARP-1 have been shown to enhance the cytotoxic effects of ionizing radiation and DNA damaging chemotherapy agents, such as the methylating agents and topoisomerase I inhibitors. There are currently at least five PARP inhibitors in clinical trial development. Recent in vitro and in vivo evidence suggests that PARP inhibitors could be used not only as chemo/radiotherapy sensitizers, but as single agents to selectively kill cancers defective in DNA repair, specifically cancers with mutations in the breast cancer associated (BRCA) 1 and 2 genes. This theory of selectively exploiting cells defective in one DNA repair pathway by inhibiting another is a major breakthrough in the treatment of cancer. BRCA1/2 mutations are responsible for the majority of genetic breast/ovarian cancers, known as the hereditary breast ovarian cancer syndrome. This review summarizes the preclinical and clinical evidence for the potential of PARP inhibitors in genetic breast and ovarian cancers.
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PMID:The potential of PARP inhibitors in genetic breast and ovarian cancers. 1883 94

Ten per cent of all breast cancer cases have a strong hereditary component in which half carry a deleterious mutation in the high penetrance genes BRCA1 or BRCA2. These genes confer a lifetime risk of 60-80% for breast cancer and 20-40% for ovarian cancer. Since the identification of these genes in the mid-1990s, an interdisciplinary approach was established in 12 specialized university-based centres in Germany for identifying high-risk families that enables genetic testing and preventive clinical options. It could be demonstrated that ultrasound, mammography, and breast MRI allow the identification of early breast cancer stages. Prophylactic mastectomy and salpingo-oophorectomy reduce breast and ovarian cancer incidence considerably. New therapeutic and preventive strategies are being validated in ongoing clinical studies. Most recently a new molecular target, a PARP inhibitor, was developed that targets specifically BRCA-deficient tumour cells. Participation in a phase II study for metastatic breast and ovarian cancer is available through the centres. Accompanying scientific studies of over 4,500 DNA samples from BRCA1/2-negative high-risk families are moreover being examined for other predisposing genes.
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PMID:[Hereditary breast cancer]. 1885 64

Whereas target-specific drugs are available for treating ERBB2-overexpressing and hormone receptor-positive breast cancers, no tailored therapy exists for hormone receptor- and ERBB2-negative ("triple-negative") mammary carcinomas. Triple-negative tumors account for 15% of all breast cancers and frequently harbor defects in DNA double-strand break repair through homologous recombination (HR), such as BRCA1 dysfunction. The DNA-repair defects characteristic of BRCA1-deficient cells confer sensitivity to poly(ADP-ribose) polymerase 1 (PARP1) inhibition, which could be relevant to treatment of triple-negative tumors. To evaluate PARP1 inhibition in a realistic in vivo setting, we tested the PARP inhibitor AZD2281 in a genetically engineered mouse model (GEMM) for BRCA1-associated breast cancer. Treatment of tumor-bearing mice with AZD2281 inhibited tumor growth without signs of toxicity, resulting in strongly increased survival. Long-term treatment with AZD2281 in this model did result in the development of drug resistance, caused by up-regulation of Abcb1a/b genes encoding P-glycoprotein efflux pumps. This resistance to AZD2281 could be reversed by coadministration of the P-glycoprotein inhibitor tariquidar. Combination of AZD2281 with cisplatin or carboplatin increased the recurrence-free and overall survival, suggesting that AZD2281 potentiates the effect of these DNA-damaging agents. Our results demonstrate in vivo efficacy of AZD2281 against BRCA1-deficient breast cancer and illustrate how GEMMs of cancer can be used for preclinical evaluation of novel therapeutics and for testing ways to overcome or circumvent therapy resistance.
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PMID:High sensitivity of BRCA1-deficient mammary tumors to the PARP inhibitor AZD2281 alone and in combination with platinum drugs. 1897 40

Triple-negative breast cancer is a subtype of breast cancer that is clinically negative for expression of estrogen and progesterone receptors (ER/PR) and HER2 protein. It is characterized by its unique molecular profile, aggressive behavior, distinct patterns of metastasis, and lack of targeted therapies. Although not synonymous, the majority of triple-negative breast cancers carry the "basal-like" molecular profile on gene expression arrays. The majority of BRCA1-associated breast cancers are triple-negative and basal-like; the extent to which the BRCA1 pathway contributes to the behavior of sporadic basal-like breast cancers is an area of active research. Epidemiologic studies illustrate a high prevalence of triple-negative breast cancers among younger women and those of African descent. Increasing evidence suggests that the risk factor profile differs between this subtype and the more common luminal subtypes. Although sensitive to chemotherapy, early relapse is common and a predilection for visceral metastasis, including brain metastasis, is seen. Targeted agents, including epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and poly (ADP-ribose) polymerase (PARP) inhibitors, are currently in clinical trials and hold promise in the treatment of this aggressive disease.
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PMID:Understanding and treating triple-negative breast cancer. 1898 22

Mammalian cells are frequently at risk of DNA damage from multiple sources. Accordingly, cells have evolved the DNA damage response (DDR) pathways to monitor the integrity of their genome. Conceptually, DDR pathways contain three major components (some with overlapping functions): sensors, signal transducers, and effectors. At the level of sensors, ATM (ataxia telangiectasia mutated) and ATR (ATM-Rad3-related) are proximal kinases that act as the core sensors of and are central to the entire DDR. These two kinases function to detect various forms of damaged DNA and trigger DNA damage response cascades. If cells harbor DDR defects and fail to repair the damaged DNA, it would cause genomic instability and, as a result, lead to cellular transformation. Indeed, deficiencies of DDR frequently occur in human cancers. Interestingly, this property of cancer also provides a great opportunity for cancer therapy. For example, by using a synthetic lethality model to search for the effective drugs, ChK1 inhibitors have been shown to selectively target the tumor cells with p53 mutations. In addition, the inhibitors of poly(ADP-ribose) polymerase (PARP-1) showed selectively killing effects on the cells with defects of homologous recombination (HR), particularly in the context of BRCA1/2 mutations. Since Brit1 is a key regulator in DDR and HR repair, we believe that we can develop a similar strategy to target cancers with Brit1 deficiency. Currently, we are conducting a high-throughput screening to identify novel compounds that specifically target the Brit1-deficient cancer which will lead to development of effective personalized drugs to cure cancer in clinic.
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PMID:DNA damage response pathways in tumor suppression and cancer treatment. 1903 64

Poly (ADP-ribose) polymerase (PARP) plays a key role in DNA repair mechanisms by detecting and initiating repair after DNA strand breaks. Inhibition of PARP in DNA repair-defective tumors (like those with BRCA1 or BRCA2 mutations) can lead to gross genomic instability and cell death. Likewise, combining PARP inhibition with cytotoxic agents such as chemotherapy or radiation therapy is synergistic in many preclinical models. Several drugs designed to inhibit PARP are currently in clinical development, many following a development path different from that of typical anticancer agents. In this review we will focus on the early clinical data from PARP inhibitors that are entering clinical trials, the potential tumors they might target, their combination with other drugs and the different biomarkers that are being explored. Concepts such as 'BRCAness', synthetic lethality, Phase 0 trials and pharmacodynamic markers will be discussed in the context of the development of PARP inhibitors.
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PMID:Development of PARP inhibitors in oncology. 1905 80

Cells carrying mutated BRCA1 or BRCA2 genes are defective in DNA repair by homologous recombination and, as a consequence, are highly sensitive to inhibitors of poly (ADP-ribose) polymerase (PARP). This provides the basis for a novel "synthetic lethal" approach to cancer therapy. We have recently shown that this sensitivity can be reversed, and resistance to PARP inhibition can be acquired by deletion of a mutation in BRCA2. Furthermore, a similar mechanism seems to be associated with carboplatin resistance in some BRCA2 mutation carriers with ovarian cancer.
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PMID:Drug resistance caused by reversion mutation. 1907 63

Poly(ADP-ribose) polymerases (PARPs) are defined as cell signaling enzymes that catalyze the transfer of ADP-ribose units from NAD(+) to a number of acceptor proteins. PARP-1, the best characterized member of the PARP family, which currently comprises 18 members, is an abundant nuclear enzyme implicated in cellular responses to DNA injury provoked by genotoxic stress. PARP is involved in DNA repair and transcriptional regulation and is now recognized as a key regulator of cell survival and cell death as well as a master component of a number of transcription factors involved in tumor development and inflammation. PARP-1 is essential to the repair of DNA single-strand breaks via the base excision repair pathway. Inhibitors of PARP-1 have been shown to enhance the cytotoxic effects of ionizing radiation and DNA-damaging chemotherapy agents, such as the methylating agents and topoisomerase I inhibitors. There are currently at least five PARP inhibitors in clinical trial development. Recent in vitro and in vivo evidence suggests that PARP inhibitors could be used not only as chemo/radiotherapy sensitizers, but also as single agents to selectively kill cancers defective in DNA repair, specifically cancers with mutations in the breast cancer-associated genes (BRCA1 and BRCA2). PARP becomes activated in response to oxidative DNA damage and depletes cellular energy pools, thus leading to cellular dysfunction in various tissues. The activation of PARP may also induce various cell death processes and promotes an inflammatory response associated with multiple organ failure. Inhibition of PARP activity is protective in a wide range of inflammatory and ischemia-reperfusion-associated diseases, including cardiovascular diseases, diabetes, rheumatoid arthritis, endotoxic shock, and stroke. The aim of this review is to overview the emerging data in the literature showing the role of PARP in the pathogenesis of cancer and inflammatory diseases and unravel the solid body of literature that supports the view that PARP is an important target for therapeutic intervention in critical illness.
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PMID:PARP inhibitors: new partners in the therapy of cancer and inflammatory diseases. 1936 86


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