DNA Damage Response Transducers Research Articles

Immune, inflammatory, autophagic and DNA damage responses to long-term H2O2 exposure in different tissues of common carp (Cyprinus carpio)

Hydrogen peroxide (H2O2) is a stable reactive oxygen species (ROS) in aquatic environment, and high concentration of ambient H2O2 may directly or indirectly affect aquatic animal health. However, the response mechanism of fish to ambient H2O2 has not been well studied yet. Therefore, the aim of the study was to investigate the immune, inflammatory, autophagic and DNA damage responses to long-term H2O2 exposure in different tissues of common carp. The results showed that H2O2 exposure induced a significant immune response, with alterations in the levels of immune parameters including AKP, ACP, LZM, C3, HSP90 and HSP70 in different tissues. The inflammatory response evoked by H2O2 exposure was associated with the activations of TLRs and NF-κB (P65) in the majority of tested tissues. The autophagy process was significantly affected by H2O2 exposure, evidenced by the upregulations of the autophagy-related genes in liver, gills, muscle, intestines, heart and spleen and the downregulations in kidney. Meanwhile, the mRNA level of atm, a primary transducer of DNA damage response, was upregulated in liver, gills, intestines and spleen, and the DNA damage was evidenced by increased 8-OHdG level in intestines after H2O2 exposure. Moreover, cell cycle regulation-related genes, including cyclin A1, B and/or E1, highly expressed in all tested tissues except heart after H2O2 exposure. Interestingly, IBR analysis exhibited that immune, inflammatory, autophagic and DNA damage responses to H2O2 exposure were in a dose-dependent and tissue-specific manner. These data may contribute to understanding H2O2 toxicity for fish and assessing potential risk of H2O2 in aquatic environment.

En Guard! The Interactions between Adenoviruses and the DNA Damage Response.

Virus–host cell interactions include several skirmishes between the virus and its host, and the DNA damage response (DDR) network is one of their important battlegrounds. Although some aspects of the DDR are exploited by adenovirus (Ad) to improve virus replication, especially at the early phase of infection, a large body of evidence demonstrates that Ad devotes many of its proteins, including E1B-55K, E4orf3, E4orf4, E4orf6, and core protein VII, and utilizes varied mechanisms to inhibit the DDR. These findings indicate that the DDR would strongly restrict Ad replication if allowed to function efficiently. Various Ad serotypes inactivate DNA damage sensors, including the Mre11-Rad50-Nbs1 (MRN) complex, DNA-dependent protein kinase (DNA-PK), and Poly (ADP-ribose) polymerase 1 (PARP-1). As a result, these viruses inhibit signaling via DDR transducers, such as the ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, to downstream effectors. The different Ad serotypes utilize both shared and distinct mechanisms to inhibit various branches of the DDR. The aim of this review is to understand the interactions between Ad proteins and the DDR and to appreciate how these interactions contribute to viral replication.

Epstein-Barr Virus Hijacks DNA Damage Response Transducers to Orchestrate Its Life Cycle.

The Epstein–Barr virus (EBV) is a ubiquitous virus that infects most of the human population. EBV infection is associated with multiple human cancers, including Burkitt’s lymphoma, Hodgkin’s lymphoma, a subset of gastric carcinomas, and almost all undifferentiated non-keratinizing nasopharyngeal carcinoma. Intensive research has shown that EBV triggers a DNA damage response (DDR) during primary infection and lytic reactivation. The EBV-encoded viral proteins have been implicated in deregulating the DDR signaling pathways. The consequences of DDR inactivation lead to genomic instability and promote cellular transformation. This review summarizes the current understanding of the relationship between EBV infection and the DDR transducers, including ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related), and DNA-PK (DNA-dependent protein kinase), and discusses how EBV manipulates the DDR signaling pathways to complete the replication process of viral DNA during lytic reactivation.

Abstract B11: YM155 synergizes with Plk1 inhibitor volasertib in killing of non-small cell lung cancer

Abstract Non-small cell lung cancer (NSCLC) remains the leading cause of cancer death in the US. There is a pressing need for more regimens that are both effective and well tolerated by the typical metastatic lung cancer population. The synthetic lethal approach is emerging as an attractive strategy in mining such regimens. Volasertib is a highly selective and potent small molecule inhibitor of polo-like kinase 1(Plk1) that is essential for cell cycle progression. Its toxicity is mainly hematological and reversible. Single agent performance is less than optimal. In a search for novel agents that boost the anti-neoplastic effects of Plk1 inhibitor volasertib, we found that a YM155 and volasertib combination at the nano mole concentration potently inhibited growth of various NSCLC cell lines than either drug alone could achieve in vitro. Flow cytometry analysis showed that the combination regimen is much more potent in inducing apoptosis than either alone. Volasertib normally arrests cells at G2/M. Cells treated with both drugs initially arrest in G2 and then distribute equally in both G1/S and G2/M suggesting that fewer cells escaped to G1 from the polo arrest compared to volasertib treatment alone in which the majority of them were able to transit to G1 from G2 phase. Western blot analysis demonstrated that addition of YM155 to volasertib prevented accumulation of survivin and cyclin B, which is consistent with a cell cycle arrest before the end of mitosis and cytokinesis when compared to volasertib alone. All these data suggest that YM155 induces cell cycle arrest. However, YM155, originally developed as a survivin inhibitor, only caused modest suppression of survivin expression and could not explain the degree of cell growth inhibition it caused. Further studies demonstrated DNA damage of cancer cells when they are treated with YM155, which is evidenced by induction of phospho-γH2AX, a marker for DNA double strand break (DSB). In line with induction of a DNA damage response in cancer cells, known DNA damage response transducers ATM, ATR, CHK1, CHK2, p53 and BRCA1 are phosphorylated following drug treatment. Meanwhile, expression of CIP1, BAX and KARP1 are induced at the mRNA level as determined by quantitative real time PCR. Therefore, YM155 suppresses cancer cell growth by causing DNA damage and illicits a DNA damage response, cell cycle arrest and programmed cell death. Furthermore, cells with wild type p53 (H661) seem to be more sensitive to YM155 induced growth arrest than cells with p53 deletion (H1299, H520), which is consistent with a role of p53 in mediating programmed cell death after DNA damage. Polo-like kinase is known to play an essential role in recovery from checkpoint-triggered cell cycle arrest. We speculate that volasertib synergizes with YM155 by preventing recovery from DNA damage checkpoint triggered cell cycle arrest. On the other hand, since YM155 causes DNA damage, fewer cells arrested in G2 by volasertib may be able to escape from the polo arrest when their DNAs are severely damaged. Currently, we are testing the two hypotheses. Combination of the two inhibitors deserves close scrutiny in the clinical arena if future studies in an animal model support this prediction. Citation Format: Mei Hong, Mingqiang Ren, John Cowell, Zhonglin Hao. YM155 synergizes with Plk1 inhibitor volasertib in killing of non-small cell lung cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr B11.