Mechanism Of DNA Damage Research Articles

Nucleus-translocated mitochondrial cytochrome c liberates nucleophosmin-sequestered ARF tumor suppressor by changing nucleolar liquid-liquid phase separation.

The regular functioning of the nucleolus and nucleus-mitochondria crosstalk are considered unrelated processes, yet cytochrome c (Cc) migrates to the nucleus and even the nucleolus under stress conditions. Nucleolar liquid-liquid phase separation usually serves the cell as a fast, smart mechanism to control the spatial localization and trafficking of nuclear proteins. Actually, the alternative reading frame (ARF), a tumor suppressor protein sequestered by nucleophosmin (NPM) in the nucleoli, is shifted out from NPM upon DNA damage. DNA damage also triggers early translocation of respiratory Cc to nucleus before cytoplasmic caspase activation. Here, we show that Cc can bind to nucleolar NPM by triggering an extended-to-compact conformational change, driving ARF release. Such a NPM-Cc nucleolar interaction can be extended to a general mechanism for DNA damage in which the lysine-rich regions of Cc-rather than the canonical, arginine-rich stretches of membrane-less organelle components-controls the trafficking and availability of nucleolar proteins.

Topoisomerase 1-dependent R-loop deficiency drives accelerated replication and genomic instability.

SummaryDNA replication is a complex process tightly regulated to ensure faithful genome duplication, and its perturbation leads to DNA damage and genomic instability. Replication stress is commonly associated with slow and stalled replication forks. Recently, accelerated replication has emerged as a non-canonical form of replication stress. However, the molecular basis underlying fork acceleration is largely unknown. Here, we show that mutated HRAS activation leads to increased topoisomerase 1 (TOP1) expression, causing aberrant replication fork acceleration and DNA damage by decreasing RNA-DNA hybrids or R-loops. In these cells, restoration of TOP1 expression or mild replication inhibition rescues the perturbed replication and reduces DNA damage. Furthermore, TOP1 or RNaseH1 overexpression induces accelerated replication and DNA damage, highlighting the importance of TOP1 equilibrium in regulating R-loop homeostasis to ensure faithful DNA replication and genome integrity. Altogether, our results dissect a mechanism of oncogene-induced DNA damage by aberrant replication fork acceleration.

Influence of differential arsenic exposure on cellular redox homeostasis of exposed rural women of West Bengal.

The metalloid arsenic (As) induces oxidative stress is a well-known fact. However, the extent of variation of oxidative stress according to different exposure levels of As in groundwater and the mechanism responsible for As mediated oxidative stress is yet to be elucidated in a human population of West Bengal. In the present study, we have investigated the impact of low level (> 10 ≤ 50µg/L) and high-level groundwater As (> 50µg/L) on cellular redox status, DNA damage, and repair mechanisms in chronically exposed rural women of West Bengal. Prediction models of ordinary least square regression of nail As, forced vital capacity (FVC) %, and that of forced expiratory volume during the first one second (FEV1) % deciphered that accumulation of As in nails may predict hemoglobin deficiency. Moreover, consumption of As-laced water tends to decrease FEV1% and FVC%. A strong positive correlation was observed between water and nail As level and reactive oxygen species (ROS) generation. ROS, perturbed nuclear factor erythroid 2-related factor 2(Nrf2)/ Kelch-like ECH-associated protein 1 (Keap1) redox regulation, compromised antioxidant defense machinery-superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione transferase (GST), induced DNA damage, and suppressed DNA repair proteins-poly ADP ribose polymerase1(PARP1)/ X-ray repair cross-complementing protein 1(XRCC1)/ 8-oxoguanine glycosylase (OGG1) in a dose-dependent manner. All the low and high As areas had very high cancer risk values for the exposed population. It has been predicted that if the As level in the drinking water of a 40-year adult increases by 2 ug/L, the likelihood of the cancer risk will increase by 10%, keeping the body weight and amount of water intake constant. Thus, long-term exposure to either low or high As is seriously affecting the lives of asymptomatic women who are vulnerable to developing carcinogenic changes after a period of latency.

DNA Damage Repair and Current Therapeutic Approaches in Gastric Cancer: A Comprehensive Review.

DNA in cells is frequently damaged by endogenous and exogenous agents. However, comprehensive mechanisms to combat and repair DNA damage have evolved to ensure genomic stability and integrity. Improper DNA damage repair may result in various diseases, including some types of tumors and autoimmune diseases. Therefore, DNA damage repair mechanisms have been proposed as novel antitumor drug targets. To date, numerous drugs targeting DNA damage mechanisms have been developed. For example, PARP inhibitors that elicit synthetic lethality are widely used in individualized cancer therapies. In this review, we describe the latent DNA damage repair mechanisms in gastric cancer, the types of DNA damage that can contribute to the development of gastric cancer, and new therapeutic approaches for gastric cancer that target DNA damage repair pathways.

Physapruin A Enhances DNA Damage and Inhibits DNA Repair to Suppress Oral Cancer Cell Proliferation.

The selective antiproliferation to oral cancer cells of Physalis peruviana-derived physapruin A (PHA) is rarely reported. Either drug-induced apoptosis and DNA damage or DNA repair suppression may effectively inhibit cancer cell proliferation. This study examined the selective antiproliferation ability of PHA and explored detailed mechanisms of apoptosis, DNA damage, and repair. During an ATP assay, PHA provided high cytotoxicity to two oral cancer cell lines (CAL 27 and Ca9-22) but no cytotoxicity to two non-malignant oral cells (HGF-1 and SG). This selective antiproliferation of PHA was associated with the selective generation of reactive oxygen species (ROS) in oral cancer cells rather than in non-malignant oral cells, as detected by flow cytometry. Moreover, PHA induced other oxidative stresses in oral cancer cells, such as mitochondrial superoxide generation and mitochondrial membrane potential depletion. PHA also demonstrated selective apoptosis in oral cancer cells rather than non-malignant cells in annexin V/7-aminoactinmycin D and caspase 3/7 activity assays. In flow cytometry and immunofluorescence assays, PHA induced γH2AX expressions and increased the γH2AX foci number of DNA damages in oral cancer cells. In contrast, the mRNA expressions for DNA repair signaling, including homologous recombination (HR) and non-homologous end joining (NHEJ)-associated genes, were inhibited by PHA in oral cancer cells. Moreover, the PHA-induced changes were alleviated by the oxidative stress inhibitor N-acetylcysteine. Therefore, PHA generates selective antiproliferation, oxidative stress, and apoptosis associated with DNA damage induction and DNA repair suppression in oral cancer cells.

Synthesis of New Cinnamoyl-Amino Acid Conjugates and in Vitro Cytotoxicity and Genotoxicity Studies.

Amino acid conjugates are described by the reaction of amino acids with bioactive organic groups such as vitamins, hormones, flavonoids, steroids, and sugars. In this study, 12 new conjugates were synthesized by reaction of cinnamic acid derivatives with various amino acids. Cytotoxic studies against four different human cancer cells (MCF7, PC-3, Caco-2, and A2780) were carried out by MTT assay method at five different concentrations. The structure-activity relationships based on the cell viability rates were evaluated. To compare the anticancer activities of the compounds using computational chemistry methods, they were docked against A2780 human ovarian cancer, Michigan Cancer Foundation-7 (MCF7), human prostate cancer (PC-3) and human colon epidermal adenocarcinoma (Caco-2) cell lines and compared with the standard 5-Fluorouracil. The results indicate that the efficacy of cinnamic acid derivatives increases with the presence of amino acids. Comet assay was conducted to understand whether the cell deaths occur through DNA damage mechanism and the results exhibit that the changes in the specified parameters were statistically significant (p<0.05). Our study demonstrated that the compounds cause cell death through the formation of DNA damage mechanism.

Background DNA damage is higher in summer than winter in both free-living and captive birds.

Although stress can cause overall damage to the genome, it is currently unknown whether normal background damage to DNA varies throughout the annual cycle. If DNA damage did vary seasonally, it would have major implications on environmental-genomic interactions. We measured background DNA double-stranded breaks using the neutral comet assay in fivetissues (nucleated red blood cells, abdominal fat, hippocampus, hypothalamus, and liver) in fourcohorts of house sparrows (Passer domesticus): free-living summer, captives on a summer light cycle, free-living winter, and captives on a winter light cycle. The experiment was designed to answer threequestions: (1) Is red blood cell DNA damage representative of other tissues? (2) Is DNA damage in captive birds representative of DNA damage in free-living birds? (3) Does DNA damage show seasonality? We found that (1) blood is a representative tissue, (2) captive animals are representative of free-living animals, and (3) DNA damage is higher in the summer than in the winter. These data indicate that red blood cells can be an index of DNA damage throughout the body and that background levels of DNA damage show substantial seasonal variation. The latter result suggests the possibility that underlying molecular mechanisms of DNA damage and/or repair also change seasonally.

Ulexite modulates the neurotoxicological outcomes of acetylferrocene-exposed rainbow trout.

In this study, the neuroprotective action potential by ulexite (UX) (18.75 mg/L) against acetylferrocene (AFC) (3.82 mg/L) induced neurotoxicity was aimed to investigate in brain tissues of Oncorhynchus mykiss. For this purpose, the effects on neurotoxicity markers, proinflammatory cytokines, antioxidant immune system, DNA, and apoptosis mechanisms were assessed on brain tissues in the 48-96h of the 96- trial period. In this research, it was determined that brain-derived nerve cell growth factor (BDNF) level and acetylcholinesterase (AChE) activity were inhibited in the brain tissue compared to the control group by AFC. In addition, inhibition in glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) values (which are antioxidant system biomarkers), and inductions in malondialdehyde (MDA) and myeloperoxidase (MPO) amounts (which are indicators of lipid peroxidation) were determined (p < 0.05) after exposure to AFC. And, while tumor necrosis factor-α (TNF-α) and IL-6 levels were increased in the AFC-exposed group, Nrf-2 levels were found to be remarkably decreased. Upregulation was also detected in 8-hydroxydeoxyguanosine (8-OHdG) and caspase-3 levels, which are related to DNA damage and apoptosis mechanism. On the contrary, UX (single/with AFC) suppressed the AChE and BDNF inhibition by AFC. Moreover, UX mitigated AFC-induced oxidative, inflammatory, and DNA damage and attenuated AFC-mediated neurotoxicity via activating Nrf2 signaling in fish. Collectively, our findings revealed that UX supplementation might exert beneficial effects and may be considered as a natural and promising neuroprotective agent against AFC-induced toxicity.

Spatial and Temporal Resolution of the Oxygen-Independent Photoinduced DNA Interstrand Cross-Linking by a Nitroimidazole Derivative.

DNA damage is ubiquitous in nature and is at the basis of emergent treatments such as photodynamic therapy, which is based on the activation of highly oxidative reactive oxygen species by photosensitizing O2. However, hypoxia observed in solid tumors imposes the necessity to devise oxygen-independent modes of action able to induce DNA damage under a low oxygen concentration. The complexity of these DNA damage mechanisms in realistic environments grows exponentially when taking into account light absorption and subsequent excited-state population, photochemical and (photo)-redox reactions, the multiple species involved in different electronic states, noncovalent interactions, multiple reaction steps, and the large number of DNA reactive sites. This work tackles all the intricate reactivity of a photosensitizer based on a nitroimidazole derivative reacting toward DNA in solution under UV light exposition. This is performed through a combination of ground- and excited-state quantum chemistry, classical molecular dynamics, and hybrid QM/MM simulations to rationalize in detail the formation of DNA interstrand cross-links (ICLs) exerted by the noncanonical noncovalent photosensitizer. Unprecedented spatial and temporal resolution of these phenomena is achieved, revealing that the ICL is sequence-specific and that the fastest reactions take place at AT, GC, and GT steps involving either the opposite nucleobases or adjacent Watson–Crick base pairs. The N7 and O6 positions of guanine, the N7 and N3 sites of adenine, the N4 position of cytosine, and the O2 atom of thymine are deemed as the most nucleophile sites and are positively identified to participate in the ICL productions. This work provides a multiscale computational protocol to study DNA reactivity with noncovalent photosensitizers, and contributes to the understanding of therapies based on photoinduced DNA damage at molecular and electronic levels. In addition, we believe the depth understanding of these processes should assist the design of new photosensitizers considering their molecular size, electronic properties, and the observed regioselectivity toward nucleic acids.

PB1787: GADD45A IS OVER-EXPRESSED IN THE BONE MARROW OF PATIENTS WITH DE NOVO ACUTE MYELOID LEUKEMIA REFRACTORY TO INDUCTION CHEMOTHERAPY

Background: Acute myeloid leukemia (AML) is a life-threatening malignant myeloid disorder with poor prognosis. Response to induction treatment determines long-term prognosis; however, mechanisms underlying response have not been thoroughly investigated. DNA damage and repair mechanisms influence not only the genetic predisposition to leukemia but are also very important for refractoriness to treatment. Aims: The aim of this study was to investigate the possible alterations in the gene expression profile of DNA damage signaling pathways in two leukemic cell lines following their exposure to chemotherapeutic agents, namely, idarubicin and cytarabine, and verify the findings in AML patient samples at diagnosis before the onset of chemotherapy. Methods: Cell lines Kasumi-1 with the t(8;21) and MV4-11 (biphenotypic B-myelomonocytic leukemia) were exposed either to idarubicin (0.1μΜ) for 6h or cytarabine (1μΜ) for 48h. Dead cells were eliminated from drug-treated cells using an appropriate commercial kit. Gene expression profiling through PCR arrays analysis (RT2 Profiler, Qiagen) was performed in triplicate after RNA extraction from untreated, chemotherapy-treated and live cells following chemotherapy exposure. Human DNA damage signaling pathway-related gene expression was evaluated and analyzed through the RT2 Profiler PCR Array data analysis tool. Moreover, mononuclear cells were isolated from bone marrow of lymphoma patients, used as controls, and from AML patients at diagnosis who subsequently received chemotherapy with the 7 + 3 regiment. Response to first-line chemotherapy was recorded. Total RNA was isolated (RNeasy plus Mini Kit, Qiagen) and quantified and cDNA was synthesized. Relative expression of genes of interest was quantified using SYBR® Green-based real-time RT-PCR (QuantiTect® Primer Assay, Qiagen). Statistics were performed using linear regression. Results: The following genes were over two-fold up-regulated in live cells from leukemic cell lines after treatment with either agent: PPP1R15A and CDKN1A in both cell lines, GADD45A and GADD45G in live MV4-11 cells and EXO1 in live Kasumi cells. These genes were selected for relative quantification; 25 control samples and 38 AML samples (28 responders and 10 non-responders to treatment) were evaluated. GADD45A in AML compared to controls was found 2-fold up-regulated in treatment responders (ns) and 9-fold up-regulated in non-responders [p=0.01]. In addition, GADD45A was overexpressed in non-responders compared to responders [p=0.02]. PPP1R15A in AML compared to controls was 12-fold up-regulated in responders [p=0.001] and 16-fold up-regulated in non-responders [p=0.001]. (Figure 1) Image:Summary/Conclusion: GADD45A controls the balance between apoptosis and autophagy via the p38 and JNK/MAPK pathways and PPP1R15A participates in growth arrest and apoptosis in response to DNA damage by attenuating the translational elongation of key transcription factors. Both genes are likely to play an important role in the pathogenesis of AML. Furthermore, GADD45A overexpression appears to be related with resistance to induction treatment, which may have significant prognostic and therapeutic implications.

DNA Damage Repair System and Antineoplastic Agents in Lung Cancer

DNA损伤修复（DNA damage repair, DDR）系统在维持“基因组稳定性”方面发挥重要作用。DNA损伤的累积及DDR功能减弱，都会促进肿瘤发生、发展，同时也给肿瘤的药物治疗提供机会和靶点。在肺癌治疗中，很多抗肿瘤药物发挥作用都与DNA损伤和修复密切相关。从导致DNA损伤的经典化疗药物、新型抗体偶联药物，到抑制DNA修复的靶向药物，以及免疫检查点抑制剂，这些药物在发挥抗肿瘤活性过程中，都直接或间接涉及DNA损伤及修复。本文综述了DNA损伤和修复在上述药物发挥抗肿瘤活性中的作用，并汇总了上述各类药物在肺癌治疗中的应用现状及临床探索，以期通过DNA损伤和修复为切入点，摸索更精准和有效的肺癌治疗策略。

Abstract SY39-01: The DNA damageome and cancer evolution

Abstract DNA damage provokes mutations, genome instability, cancer and biological aging and results from external agents or endogenous cellular processes. We identified networks of unrelated proteins of diverse functions that promote DNA damage when overproduced: the DNA “damageome” proteins (DDPs). We found a large overproduction DDP network in Escherichia coli and find that the proteins promote mutagenesis and genome instability by various mechanisms—three of which we identify. Their 284 human homologs are over-represented among known cancer drivers, and their expression in tumors predicts heavy mutagenesis and poor prognosis. When overproduced in human cells, many of the human homologs promote DNA damage and mutation, with DNA-damaging mechanisms like those in E. coli. As the earliest upstream provocateurs of cancer evolution, the proteins of DNA damageome networks may indicate that there are evolution-accelerating functions of many human known and newly implicated cancer-promoting proteins. Citation Format: Susan Rosenberg. The DNA damageome and cancer evolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr SY39-01.

DNA damage response in neurodevelopment and neuromaintenance.

The central nervous system is particularly susceptible to DNA repair deficiency, which renders a variety of neurodevelopmental and neurodegenerative disorders in humans. It is generally believed that DNA damage occurs upon repetitive replication and oxidative stress in highly proliferating neuroprogenitor cells (NPs), or due to high rates of metabolism and active neuronal activity in terminally differentiated neurons. DNA double-stranded breaks (DSBs) and single-stranded breaks (SSBs) constitute the most prevalent forms of DNA damage, which can result in neuronal apoptosis if unrepaired. Despite these notions, there are still gaps in our knowledge regarding the mechanism and specificity of DNA damage and repair in the neural development and the homeostasis of neural tissues. Recent studies have identified recurrent DSBs within neuronal long genes in NPs and 'programmed' SSBs in neuronal activity genes. However, the physiological function of these DNA breakages in the nervous system has not been so far explored. In this review, we summarise the recent advances in the field of DNA damage and DNA repair in neural development and neuropathies.

Silica Nanoparticle–Induced Reproductive Toxicity in Male Albino Rats via Testicular Apoptosis and Oxidative Stress

Amorphous silica nanoparticles (SiNPs) are being utilized in different fields such as medicine, cosmetics, and foods. However, the causes and mechanisms underlying SiNP testicular damage remain largely unclear. In the present study, we aimed to investigate this issue. Thirty male rats were randomly divided into three groups: control group (n = 10), 500 ppm SiNP–treated group (n = 10), and 1000 ppm SiNP–treated group (n = 10). SiNPs were given orally in drinking water for 30 days. Micronucleus assay was performed on blood RBCs. The concentrations of testicular malondialdehyde (MDA) and glutathione (GSH) and catalase (CAT) activity were measured. Moreover, the histopathological alterations and the expression of apoptotic (caspase-3) and pro-inflammatory and oxidative stress markers (iNOS) in testes and epididymis were analyzed and compared between the three groups. The results showed an increased level of micronucleus frequencies in the 1000 ppm–treated group, as well as increased levels of MDA and decreased activity of CAT and GSH content in testicular tissues in the 1000 ppm–treated group, suggesting DNA damage and oxidative stress mechanisms. Also, there were significant testicular histopathological alterations in this group. Furthermore, 1000-ppm SiNPs could enhance testicular apoptosis, inflammation, and oxidative stress by increasing the expression of apoptotic, pro-inflammatory, and oxidative stress genes including caspase 3 and iNOS in the examined tissue. The lower concentration of SiNPs did not produce any significant biochemical, histopathological, or immunohistochemical alterations whereas 1000-ppm SiNPs resulted in significant testicular changes by exacerbating apoptotic, inflammatory, and oxidative stress–mediated testicular damage.

Targeting DNA damage response in cardiovascular diseases: from pathophysiology to therapeutic implications.

Cardiovascular diseases (CVDs) arise from a complex interplay among genomic, proteomic, and metabolomic abnormalities. Emerging evidence has recently consolidated the presence of robust DNA damage in a variety of cardiovascular disorders. DNA damage triggers a series of cellular responses termed DNA damage response (DDR) including detection of DNA lesions, cell cycle arrest, DNA repair, cellular senescence, and apoptosis, in all organ systems including hearts and vasculature. Although transient DDR in response to temporary DNA damage can be beneficial for cardiovascular function, persistent activation of DDR promotes the onset and development of CVDs. Moreover, therapeutic interventions that target DNA damage and DDR have the potential to attenuate cardiovascular dysfunction and improve disease outcome. In this review, we will discuss molecular mechanisms of DNA damage and repair in the onset and development of CVDs, and explore how DDR in specific cardiac cell types contributes to CVDs. Moreover, we will highlight the latest advances regarding the potential therapeutic strategies targeting DNA damage signalling in CVDs.

Development of a Bile Acid-Related Gene Signature for Predicting Survival in Patients with Hepatocellular Carcinoma.

Background Hepatocellular carcinoma (HCC) is one of the most common diseases that threaten millions of lives annually. Evidence supports that bile acid (BA) affects HCC through inflammation, DNA damage, or other mechanisms. Methods A total of 127 BA-associated genes were analyzed in HCC tumor and nontumor samples using The Cancer Genome Atlas data. Genes correlated to the prognosis of patients with HCC were identified using univariate and multivariate Cox regression analyses. Furthermore, a prediction model with identified genes was constructed to evaluate the risk of patients with HCC for prognosis. Results Out of 26 genes with differential expressions between the HCC and nontumor samples, 19 and 7 genes showed upregulated and downregulated expressions, respectively. Three genes, NPC1, ABCC1, and SLC51B, were extrapolated to construct a prediction model for the prognosis of patients with HCC. Conclusion The three-gene prediction model was more reliable than the pathological staging characters of the tumor for the prognosis and survival of patients with HCC. In addition, the upregulated genes facilitating the transport of BAs are associated with poor prognosis of patients with HCC, and genes of de novo synthesis of BAs benefit patients with HCC.

Ionizing radiation-induced DNA damage responses affect cell compressibility.

Radiotherapy is an important treatment modality for cancer patients. Ionizing radiation kills cancer cells by inducing DNA damage. However, it remains unclear how this process affects the biomechanical properties of cells and how cellular mechanics affect DNA damage and repair. In this study, the effects of ionizing radiation on cell mechanics were investigated by precisely measuring the compressibility of cells in suspension using an in-house developed microfluidic device. We found that cell compressibility significantly increased after irradiation, depending on cell type and radiation dose. Radiation-induced DNA damage response (DDR) is an important process that alters cell mechanics, and this association was confirmed experimentally by inhibiting the DDR process. Furthermore, the mechanisms involved in changes in cell compressibility were investigated from the perspective of the nucleus and cytoplasm. Experiments showed that radiation reduced H3K9me3 staining intensity but had no effect on F-actin. This suggested that chromatin decondensation caused by radiation-induced DDR is the primary cause of changes in cell compressibility after radiation. The effects of cell mechanics on radiation-induced DNA damage were also investigated. The addition of blebbistatin reduced cytoskeletal forces on the nucleus, which resulted in a reduction in radiation-induced DNA damage. Collectively, this study elucidated reciprocal mechanisms of radiation-induced DNA damage and cell mechanics.

Abstract 302: Upregulation Of The Absent-in-melanoma 2 Inflammasome Correlates With Markers Of DNA Damage And Cell Cycle Dysregulation In Peripheral Arterial Disease

Introduction: We showed that myoblasts (Mb) in peripheral arterial disease (PAD) differentiate poorly and have evidence of inflammasome activation. Absent-in-melanoma 2 (AIM2), an inflammasome and mediator of pyroptosis, binds damaged DNA which also triggers the G2/M DNA damage checkpoint including CDC2 and its regulator, polo-like kinase 1 (PLK1). Dysregulated checkpoints can cause faulty replication, but a link between checkpoint function and AIM2 is not known. We hypothesize that AIM2 expression in PAD Mb correlates with increased DNA damage and a dysregulated G2/M DNA damage checkpoint. Methods: Cells were harvested from ischemic and perfused muscle obtained during amputations for PAD. Mb (Pax7-/MyoD+) were isolated using sequential plating and cell sorting. Mb from healthy donors (PAD -) were purchased (Cook MyoSite®). AIM2, γH2AX (DNA damage marker), PLK1 and CDC2 were measured with immunofluorescence (5 images/dish). Mb were treated with the PLK1-inhibitor BI2536 (10nM; 1h) to assess checkpoint responsiveness. ANOVA with post-hoc analysis confirmed statistical significance (α=0.05). Results: γH2AX expression was elevated in all PAD groups compared to PAD (-) Mb (N=3-4/PAD group). While PLK1 expression was similar across groups, CDC2 was lower in all ischemic PAD groups relative to perfused PAD Mb. BI2536 attenuated CDC2 expression in perfused PAD Mb (p = 0.006) while Mb in ischemic PAD remained unresponsive. AIM2 expression was significantly higher in ischemic Mb compared to perfused and PAD (-) Mb, correlating with high γH2AX and low CDC2. Results are summarized in Figure 1. Conclusion: Here, we show that in PAD Mb, AIM2 correlates with DNA damage, attenuated DNA damage checkpoint protein expression and diminished CDC2 responsiveness to BI2536. Thus, AIM2 may promote pyroptosis in the setting of defective DNA damage mechanisms that would otherwise prompt apoptosis. Whether these pathways are reversed by revascularization is a topic of further study.

Targeting the key players of DNA Repair Pathways as Cancer Therapeutics

The DNA Damage Response (DDR) is essentially a complicated network of cellular pathways involving a vast array of signalling proteins that help in maintaining the genome integrity of the cell and its turmoil is one of the hallmarks of cancer. Longestablished treatment of cancer with radiation therapies or genotoxic chemotherapies has exploited the defects in the DNA damage response for therapeutic application. The recent strategies for targeted therapy aim on inhibiting the DNA damage response in cancer which offers a greater potential by tailoring treatment to patients with tumours lacking specific DDR functions. This out-manoeuvres one of the key limitations of many DNA-damaging therapies, which is their inability in selectively targeting cancer cells that in turn leads to toxic effects on healthy cells and disastrous effects for patients. This review highlights the different concepts of DNA damage and repair mechanisms that exist in a living cell. In addition, it discusses the small molecule inhibitors of DDR pathway that seem to be promising cancer therapeutics.

Fusobacterium nucleatum and Colorectal Cancer.

Fusobacterium nucleatum (F.n) is an oral anaerobic gram-negative bacillus that can colonize into the colon tissues through bloodstream infection. F.n have been found to be involved in both the occurrence and metastasis of colorectal cancer (CRC) through regulating immune response, virulence factor, oncogenic microRNAs, intestinal metabolites, DNA damage and other mechanisms. Therefore, F.n can be as an important pathogenic risk factor and a possible biomarker of CRC. Based on this, we have summarized the potential relationship between F.n and CRC to provide reference for the targeted therapy of CRC.