H2AX phosphorylation and DNA damage kinase activity are dispensable for herpes simplex virus replication

Synergistic antitumor efficacy of rMV-Hu191 and Olaparib in pancreatic cancer by generating oxidative DNA damage and ROS-dependent apoptosis

BACKGROUND

Malignancies with BRCA1/2 deficiencies are particularly sensitive to PARP inhibitors. Thus, combining PARP inhibitors with agents that impair DNA damage repair to treat BRCA1/2 wild-type PDAC could broaden the clinical use of these promising PARP inhibitors. Here we examined the synergism and mechanism of oncolytic measles virus (rMV-Hu191) with a PARP inhibitor (Olaparib) in vitro and in vivo.

METHODS

The cell viability assay, cell cycle analysis, colony formation assay, TCID 50 method, western blotting, flow cytometry, DNA comet assay, Mice bearing PDAC xenografts, IF, IHC and TUNEL assay were performed to explore the antitumor efficacy and underlying mechanisms.

RESULTS

In this study, we explored the antitumor activities of rMV-Hu191 and Olaparib in two PDAC cell lines harboring wild-type BRCA1/2 genes. Compared to monotherapy, the combination of rMV-Hu191 and Olaparib was able to synergistically cause growth arrest, apoptotic cell death and DNA damage, accompanying with excessive oxidative stress. Mechanistically, the data indicated that the observed synergy depended on the oxidative DNA damage and ROS-dependent apoptosis generating by rMV-Hu191 combined with Olaparib in human PDAC cells. Tumor inhibition and prolonged survival of PDAC mice xenografts in vivo confirmed the synergism of combinational treatment with trivial side-effects.

CONCLUSIONS

Our findings firstly suggested that combination treatment with rMV-Hu191 and Olaparib had a profound and synergistic therapeutic effect against human PDAC through synthetic lethality. In conclusion, we recommend combining oncolytic rMV-Hu191 with a PARP inhibitor (Olaparib) as a novel therapeutic strategy and provided a potential mechanism for advanced PDAC regardless of BRCA mutation status.

Chk1 and the Host Cell DNA Damage Response as a Potential Antiviral Target in BK Polyomavirus Infection

The human BK polyomavirus (BKPyV) is latent in the kidneys of most adults, but can be reactivated in immunosuppressed states, such as following renal transplantation. If left unchecked, BK polyomavirus nephropathy (PyVAN) and possible graft loss may result from viral destruction of tubular epithelial cells and interstitial fibrosis. When coupled with regular post-transplant screening, immunosuppression reduction has been effective in limiting BKPyV viremia and the development of PyVAN. Antiviral drugs that are safe and effective in combating BKPyV have not been identified but would be a benefit in complementing or replacing immunosuppression reduction. The present study explores inhibition of the host DNA damage response (DDR) as an antiviral strategy. Immunohistochemical and immunofluorescent analyses of PyVAN biopsies provide evidence for stimulation of a DDR in vivo. DDR pathways were also stimulated in vitro following BKPyV infection of low-passage human renal proximal tubule epithelial cells. The role of Chk1, a protein kinase known to be involved in the replication stress-induced DDR, was examined by inhibition with the small molecule LY2603618 and by siRNA-mediated knockdown. Inhibition of Chk1 resulted in decreased replication of BKPyV DNA and viral spread. Activation of mitotic pathways was associated with the reduction in BKPyV replication. Chk1 inhibitors that are found to be safe and effective in clinical trials for cancer should also be evaluated for antiviral activity against BKPyV.

Herpes Simplex Virus 1 Manipulates Host Cell Antiviral and Proviral DNA Damage Responses

Cells activate their DNA damage response (DDR) in response to DNA virus infection, including adenoviruses, papillomaviruses, polyomaviruses, and herpesviruses. In this study, we found that the DDR kinase pathways activated in normal human fibroblasts by herpes simplex virus 1 (HSV-1) input genomic DNA, HSV-1 replicating DNA, and progeny DNA and in uninfected cells treated with etoposide are different. We also found using clustered regularly interspaced palindromic repeat (CRISPR)-Cas9 technology that different host gene products are required for the DDR in uninfected versus infected cells. Individual DDR components can be proviral or antiviral in that ataxia-telangiectasia mutated (ATM) and p53 promote and Mre11 restricts replication of ICP0-null HSV-1, but ICP0 expression eliminates these DDR effects. Thus, in total, these results argue that HSV-1 manipulates the host cell DDR to utilize specific components for its optimal replication while inactivating the antiviral aspects of the DDR.IMPORTANCE We investigated the relationship between the DNA damage response, a collection of vital cellular pathways that repair potentially lethal damage to the genome, and the DNA virus herpes simplex virus 1. We found that infection by the virus triggers the DNA damage response, and key proteins that mediate this response have opposing effects on the replication and production of progeny viruses. Our work provides novel insights into the relationship between DNA virus infection and the cellular response to the viral genome. We speculate that viral gene products modulate this response, providing potentially novel targets for therapeutic intervention against the virus.

Preliminary study on radiosensitivity to carbon ions in human breast cancer

The aim of the study was to investigate the various effects of high linear energy transfer (LET) carbon ion (12C6+) and low LET X-ray radiation on MDA-MB-231 and MCF-7 human breast cancer cells and to explore the underlying mechanisms of radiation sensitivity. Cell proliferation, cell colony formation, cell cycle distribution, cell apoptosis and protein expression levels [double-strand break marker γ-H2AX, cell cycle-related protein cyclin B1, apoptosis-related proteins Bax and Bcl-2, and the Akt/mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase B1 (p70S6K) pathway] were detected after irradiation with carbon ions or X-rays at doses of 0, 2, 4 and 8 Gy. Our results showed that the inhibition of cell proliferation and cell colony formation and the induction of G2/M phase arrest, DNA lesions and cell apoptosis/necrosis elicited by carbon ion irradiation were more potent than the effects elicited by X-ray radiation at the same dose. Simultaneously, compared with X-ray radiation, carbon ion radiation induced a marked increase in Bax and prominent decreases in cyclin B1 and Bcl-2 in a dose-dependent manner. Furthermore, the Akt/mTOR/p70S6K pathway was significantly inhibited by carbon ion radiation in both breast cancer cell lines. These results indicate that carbon ion radiation kills MDA-MB-231 and MCF-7 breast cancer cells more effectively than X-ray radiation, which might result from the inhibition of the Akt/mTOR/p70S6K pathway.

Virus DNA Replication and the Host DNA Damage Response

Viral DNA genomes have limited coding capacity and therefore harness cellular factors to facilitate replication of their genomes and generate progeny virions. Studies of viruses and how they interact with cellular processes have historically provided seminal insights into basic biology and disease mechanisms. The replicative life cycles of many DNA viruses have been shown to engage components of the host DNA damage and repair machinery. Viruses have evolved numerous strategies to navigate the cellular DNA damage response. By hijacking and manipulating cellular replication and repair processes, DNA viruses can selectively harness or abrogate distinct components of the cellular machinery to complete their life cycles. Here, we highlight consequences for viral replication and host genome integrity during the dynamic interactions between virus and host.

Virus DNA Replication and the Host DNA Damage Response

Viral DNA genomes have limited coding capacity and therefore harness cellular factors to facilitate replication of their genomes and generate progeny virions. Studies of viruses and how they interact with cellular processes have historically provided seminal insights into basic biology and disease mechanisms. The replicative life cycles of many DNA viruses have been shown to engage components of the host DNA damage and repair machinery. Viruses have evolved numerous strategies to navigate the cellular DNA damage response. By hijacking and manipulating cellular replication and repair processes, DNA viruses can selectively harness or abrogate distinct components of the cellular machinery to complete their life cycles. Here, we highlight consequences for viral replication and host genome integrity during the dynamic interactions between virus and host.

Human foreskin fibroblasts: from waste bag to important biomedical applications

Circumcision is one of the most performed surgical procedures worldwide, and it is estimated that one in three men worldwide is circumcised, which makes the preputial skin removed after surgery an abundant material for possible applications. In particular, it is possible efficiently to isolate the cells of the foreskin, with fibroblasts being the most abundant cells of the dermis and the most used in biomedical research. This work aimed to review the knowledge and obtain a broad view of the main applications of human foreskin fibroblast cell culture. A literature search was conducted, including clinical trials, preclinical basic research studies, reviews and experimental studies. Several medical and laboratory applications of human foreskin fibroblast cell culture have been described, especially when it comes to the use of human foreskin fibroblasts as feeder cells for the cultivation of human embryonic stem cells, in addition to co-culture with other cell types. The culture of foreskin fibroblasts has also been used to: obtain induced pluripotent stem cells; the diagnosis of Clostridium difficile; to test the toxicity and effect of substances on normal cells, especially the toxicity of possible antineoplastic drugs; in viral culture, mainly of the human cytomegalovirus, study of the pathogenesis of other microorganisms; varied studies of cellular physiology and cellular interactions. Fibroblasts are important for cell models for varied application cultures, demonstrating how the preputial material can be reused, making possible new applications.

Level of evidence: Not applicable for this multicentre audit.

The ATM and Rad3-Related (ATR) Protein Kinase Pathway Is Activated by Herpes Simplex Virus 1 and Required for Efficient Viral Replication

The ATM and Rad3-related (ATR) protein kinase and its downstream effector Chk1 are key sensors and organizers of the DNA damage response (DDR) to a variety of insults. Previous studies of herpes simplex virus 1 (HSV-1) showed no evidence for activation of the ATR pathway. Here we demonstrate that both Chk1 and ATR were phosphorylated by 3 h postinfection (h.p.i.). Activation of ATR and Chk1 was observed using 4 different HSV-1 strains in multiple cell types, while a specific ATR inhibitor blocked activation. Mechanistic studies point to early viral gene expression as a key trigger for ATR activation. Both pATR and pChk1 localized to the nucleus within viral replication centers, or associated with their periphery, by 3 h.p.i. Significant levels of pATR and pChk1 were also detected in the cytoplasm, where they colocalized with ICP4 and ICP0. Proximity ligation assays confirmed that pATR and pChk1 were closely and specifically associated with ICP4 and ICP0 in both the nucleus and cytoplasm by 3 h.p.i., but not with ICP8 or ICP27, presumably in a multiprotein complex. Chemically distinct ATR and Chk1 inhibitors blocked HSV-1 replication and infectious virion production, while inhibitors of ATM, Chk2, and DNA-dependent protein kinase (DNA-PK) did not. Together our data show that HSV-1 activates the ATR pathway at early stages of infection and that ATR and Chk1 kinase activities play important roles in HSV-1 replication fitness. These findings indicate that the ATR pathway may provide insight for therapeutic approaches.IMPORTANCE Viruses have evolved complex associations with cellular DNA damage response (DDR) pathways, which sense troublesome DNA structures formed during infection. The first evidence for activation of the ATR pathway by HSV-1 is presented. ATR is activated, and its downstream target Chk1 is robustly phosphorylated, during early stages of infection. Both activated proteins are found in the nucleus associated with viral replication compartments and in the cytoplasm associated with viral proteins. We also demonstrate that both ATR and Chk1 kinase activities are important for viral replication. The findings suggest that HSV-1 activates ATR and Chk1 during early stages of infection and utilizes the enzymes to promote its own replication. The observation may be exploitable for antiviral approaches.

Herpes Simplex Virus Latency: The DNA Repair-Centered Pathway

Like all herpesviruses, herpes simplex virus 1 (HSV1) is able to produce lytic or latent infections depending on the host cell type. Lytic infections occur in a broad range of cells while latency is highly specific for neurons. Although latency suggests itself as an attractive target for novel anti-HSV1 therapies, progress in their development has been slowed due in part to a lack of agreement about the basic biochemical mechanisms involved. Among the possibilities being considered is a pathway in which DNA repair mechanisms play a central role. Repair is suggested to be involved in both HSV1 entry into latency and reactivation from it. Here I describe the basic features of the DNA repair-centered pathway and discuss some of the experimental evidence supporting it. The pathway is particularly attractive because it is able to account for important features of the latent response, including the specificity for neurons, the specificity for neurons of the peripheral compared to the central nervous system, the high rate of genetic recombination in HSV1-infected cells, and the genetic identity of infecting and reactivated virus.