Exacerbated DNA Damage Research Articles

PARP inhibition-associated heterochromatin confers increased DNA replication stress and vulnerability to ATR inhibition in SMARCA4-deficient cells

DNA replication stress (RS), a prevalent feature of various malignancies, arises from both genetic mutations and genotoxic exposure. Elevated RS levels increase the vulnerability of cancer cells to ataxia telangiectasia and Rad3-related kinase inhibitors (ATRis). Here, we screened for DNA damage response inhibitors that enhance ATRi-induced cytotoxicity using SWI/SNF complex-deficient cells and identified a potent synergy between ATRi and poly(ADP-ribose) polymerase inhibitor (PARPi), particularly in SMARCA4-deficient cells. PARP inhibition triggers chromatin changes, namely elevated histone H3 at lysine 9 di-methylation (H3K9me2), a hallmark of facultative heterochromatin, increasing dependence on ATR activity for replication fork progression and cell survival. Interestingly, SMARCA4 deficient cells, intrinsically vulnerable to replication stress, exhibited exacerbated DNA damage upon combined ATRi and PARPi treatment in a Mre11- and Mus81-mediated manner. In vivo, combined treatment with intermittent ATRi and continuous PARPi showed greater inhibition of tumor growth than ATRi alone in SMARCA4-deficient lung adenocarcinoma xenograft models. These findings demonstrate that PARPi-induced heterochromatin amplifies RS and ATRi susceptibility, providing a potential rationale for therapeutic strategies targeting SMARCA4-deficient tumors.

The intersection of inflammation and DNA damage as a novel axis underlying the pathogenesis of autism spectrum disorders.

Autism spectrum disorders (ASD) affects 1 in 36 children and is characterized by repetitive behaviors and difficulties in social interactions and social communication. The etiology of ASD is extremely heterogeneous, with a large number of ASD cases that are of unknown or complex etiology, which suggests the potential contribution of epigenetic risk factors. In particular, epidemiological and animal model studies suggest that inflammation during pregnancy could lead to an increased risk of ASD in the offspring. However, the molecular mechanisms that contribute to ASD pathogenesis in relation to maternal inflammation during pregnancy in humans are underexplored. Several pro-inflammatory cytokines have been associated with increased autistic-like behaviors in animal models of maternal immune activation, including IL-17A. Using a combination of ASD patient lymphocytes and stem cell-derived human neurons exposed to IL-17A we discovered a shared molecular signature that highlights a metabolic and translational node that could lead to altered neuronal excitability. Further, our work on human neurons brings forward the possibility that defects in the DNA damage response could be underlying the effect of IL-17A on human excitatory neurons, linking exacerbated unrepaired DNA damage to the pathogenicity of maternal inflammation in connection to ASD.

Toxicity of microplastics and nano-plastics to coral-symbiotic alga (Dinophyceae Symbiodinium): Evidence from alga physiology, ultrastructure, OJIP kinetics and multi-omics.

Corals are representative of typical symbiotic organisms. The coral-algal (Symbiodinium spp.) symbiosis drives the productivity of entire coral reefs. In recent years, microplastics (MPs) and nano-plastics (NPs) have been shown to disrupt this symbiosis, leading to coral bleaching. However, how MPs/NPs affect the Symbiodinium spp. is less thoroughly explored. In this work, Dinophyceae Symbiodinium was employed as a model to study the toxicity effects of MPs and NPs with different concentrations (covering environment-related concentration) toward algae in terms of cellular responses, ultrastructure, OJIP kinetics curve and multi-omics. MPs and NPs caused adverse effects on algae growth throughout whole growing phase, with only slight differences observed in the maximal inhibition ratio. In addition to cell surface shrinkage, holes and plate sutures shedding of algae, the presence of distorted thylakoids, plasmolysis and expanded vesicle volume were observed due to the oxidative stress and physical damage caused by MPs/NPs. The results of OJIP kinetics and JIP-test revealed that MPs/NPs-induced deactivation of oxygen-releasing complex (OEC) centers, reduced electron transfer (photosystem II, PSII), and inefficient energy conversion of antenna proteins were the primary factors for photosynthesis reduction. Weighted correlation network analysis (WGCNA) showed that the impairment of photosynthesis further induces metabolic disturbances, including reactive oxygen species (ROS) generation and nucleotide metabolism dysregulation, thereby exacerbating DNA damage in the algae. Proteomics further validate the accuracy of our results and underscore the significance of the phosphatidylinositol (PI) signaling system in algae responding to MP/NPs acclimation. Collectively, our findings provide comprehensive insights into the ecotoxicity of NPs/MPs on symbiotic algae.

DDO1002, an NRF2-KEAP1 inhibitor, improves hematopoietic stem cell aging and stress response.

Oxidative stress diminishes the functionality of hematopoietic stem cells (HSCs) as age advances, with heightened reactive oxygen species (ROS) levels exacerbating DNA damage, cellular senescence, and hematopoietic impairment. DDO1002, a potent inhibitor of the NRF2-KEAP1 pathway, modulates the expression of antioxidant genes. Yet, the extent to which it mitigates hematopoietic decline post-total body irradiation (TBI) or in the context of aging remains to be elucidated. Our study has elucidated the role of DDO1002 in modulating NRF2 activity, which, in turn, activates the NRF2-driven antioxidant response element (ARE) signaling cascade. This activation can diminish intracellular levels of ROS, thereby attenuating cellular senescence. In addition, DDO1002 has been demonstrated to ameliorate DNA damage and avert HSC apoptosis, underscoring its potential to mitigate hematopoietic injury precipitated by TBI. Competitive transplantation assay revealed that the administration of DDO1002 can improve the reconstitution and self-renewal capacity of HSCs in aged mice. Single-cell sequencing analysis elucidated that DDO1002 treatment attenuated intracellular inflammatory signaling pathways and mitigated ROS pathway in aged HSCs, suggesting its potential to restore the viability of these cells. Consequently, DDO1002 effectively activated the NRF2-ARE pathway, delaying cellular senescence and ameliorating impaired hematopoiesis, thereby demonstrating its potential as a therapeutic agent for age-related hematopoietic disorders.

Long non-coding ribonucleic acid SNHG18 induced human granulosa cell apoptosis via disruption of glycolysis in ovarian aging

BackgroundIn-depth understanding of dynamic expression profiles of human granulosa cells (GCs) during follicular development will contribute to the diagnostic and targeted interventions for female infertility. However, genome-scale analysis of long non-coding ribonucleic acid (lncRNA) in GCs across diverse developmental stages is challenging. Meanwhile, further research is needed to determine how aberrant lncRNA expression participates in ovarian diseases.MethodsGranulosa cell-related lncRNAs data spanning five follicular development stages were retrieved and filtered from the NCBI dataset (GSE107746). Stage-specific lncRNA expression patterns and mRNA-lncRNA co-expression networks were identified with bioinformatic approaches. Subsequently, the expression pattern of SNHG18 was detected in GCs during ovarian aging. And SNHG18 siRNA or overexpression plasmids were transfected to SVOG cells in examining the regulatory roles of SNHG18 in GC proliferation and apoptosis. Moreover, whether PKCɛ/SNHG18 signaling take part in GC glycolysis via ENO1 were verified in SVOG cells.ResultsWe demonstrated that GC-related lncRNAs were specifically expressed across different developmental stages, and coordinated crucial biological functions like mitotic cell cycle and metabolic processes in the folliculogenesis. Thereafter, we noticed a strong correlation of PRKCE and SNHG18 expression in our analysis. With downregulated SNHG18 of GCs identified in the context of ovarian aging, SNHG18 knockdown could further induce cell apoptosis, retard cell proliferation and exacerbate DNA damage in SVOG cell. Moreover, downregulated PKCɛ/SNHG18 pathway interrupted the SVOG cell glycolysis by lowering the ENO1 expression.ConclusionsAltogether, our results revealed that folliculogenesis-related lncRNA SNHG18 participated in the pathogenesis of ovarian aging, which may provide novel biomarkers for ovarian function and new insights for the infertility treatment.

ERK5 suppression overcomes FAK inhibitor resistance in mutant KRAS-driven non-small cell lung cancer

Mutated KRAS serves as the oncogenic driver in 30% of non-small cell lung cancers (NSCLCs) and is associated with metastatic and therapy-resistant tumors. Focal Adhesion Kinase (FAK) acts as a mediator in sustaining KRAS-driven lung tumors, and although FAK inhibitors are currently undergoing clinical development, clinical data indicated that their efficacy in producing long-term anti-tumor responses is limited. Here we revealed two FAK interactors, extracellular-signal-regulated kinase 5 (ERK5) and cyclin-dependent kinase 5 (CDK5), as key players underlying FAK-mediated maintenance of KRAS mutant NSCLC. Inhibition of ERK5 and CDK5 synergistically suppressed FAK function, decreased proliferation and induced apoptosis owing to exacerbated ROS-induced DNA damage. Accordingly, concomitant pharmacological inhibition of ERK5 and CDK5 in a mouse model of KrasG12D-driven lung adenocarcinoma suppressed tumor progression and promoted cancer cell death. Cancer cells resistant to FAK inhibitors showed enhanced ERK5-FAK signaling dampening DNA damage. Notably, ERK5 inhibition prevented the development of resistance to FAK inhibitors, significantly enhancing the efficacy of anti-tumor responses. Therefore, we propose ERK5 inhibition as a potential co-targeting strategy to counteract FAK inhibitor resistance in NSCLC.

Iron regulatory protein two facilitates ferritinophagy and DNA damage/repair through guiding ATG9A trafficking

Trace elemental iron is an essential nutrient that participates in diverse metabolic processes. Dysregulation of cellular iron homeostasis, both iron deficiency and iron overload, is detrimental and tightly associated with diseases pathogenesis. IRPs-IREs system locates at the center for iron homeostasis regulation. Additionally, ferritinophagy, the autophagy-dependent ferritin catabolism for iron recycle, is emerging as a novel mechanism for iron homeostasis regulation. It is still unclear whether IRPs-IREs system and ferritinophagy are synergistic or redundant in determining iron homeostasis. Here we report that IRP2, but not IRP1, is indispensable for ferritinophagy in response to iron depletion. Mechanistically, IRP2 ablation results in compromised AMPK activation and defective ATG9A endosomal trafficking, leading to the decreased engulfment of NCOA4-ferritin complex by endosomes and the subsequent dysregulated endosomal microferritinophagy. Moreover, this defective endosomal microferritinophagy exacerbates DNA damage and reduces colony formation in IRP2 depleted cells. Collectively, this study expands the physiological function of IRP2 in endosomal microferritinophagy and highlights a potential crosstalk between IRPs-IREs and ferritinophagy in manipulating iron homeostasis.

Cigarette smoke extract induces malignant transformation and DNA damage via c-MET phosphorylation in human bronchial epithelial cells

Cigarette smoke, a complex mixture produced by tobacco combustion, contains a variety of carcinogens and can trigger DNA damage. Overactivation of c-MET, a receptor tyrosine kinase, may cause cancer and cellular DNA damage, but the underlying mechanisms are unknown. In this work, we investigated the mechanisms of cigarette smoke extract (CSE) induced malignant transformation and DNA damage in human bronchial epithelial cells (BEAS-2B). The results demonstrated that CSE treatment led to up-regulated mRNA expression of genes associated with the c-MET signaling pathway, increased expression of the DNA damage sensor protein γ-H2AX, and uncontrolled proliferation in BEAS-2B cells. ATR, ATR, and CHK2, which are involved in DNA damage repair, as well as the phosphorylation of c-MET and a group of kinases (ATM, ATR, CHK1, CHK2) involved in the DNA damage response were all activated by CSE. In addition, CSE activation promotes the phosphorylation modification of ATR, CHK1 proteins associated with DNA damage repair. The addition of PHA665752, a specific inhibitor of c-MET, or knock-down with c-MET both attenuated DNA damage, while overexpression of c-MET exacerbated DNA damage. Thus, c-MET phosphorylation may be involved in CSE-induced DNA damage, providing a potential target for intervention in the prevention and treatment of smoking-induced lung diseases.

Early inhibition of the ATM/p53 pathway reduces the susceptibility to atrial fibrillation and atrial remodeling following acute myocardial infarction

Atrial fibrillation (AF) emerges as a critical complication following acute myocardial infarction (AMI) and is associated with a significant increased risk of heart failure, stroke and mortality. Ataxia telangiectasia mutated (ATM), a key player in DNA damage repair (DDR), has been implicated in multiple cardiovascular conditions, however, its involvement in the development of AF following AMI remains unexplored. This study seeks to clarify the contribution of the ATM/p53 pathway in the onset of AF post-AMI and to investigate the underlying mechanisms. The rat model of AMI was established by ligating left anterior descending coronary artery in the presence or absence of Ku55933 (an ATM kinase inhibitor, 5 mg/kg/d) treatment. Rats receiving Ku55933 were further divided into the early administration group (administered on days 1, 2, 4, and 7 post-AMI) and the late administration group (administered on days 8, 9, 11 and 14 post-AMI). RNA-sequencing was performed 14 days post-operation. In vitro, H2O2-challenged HL-1 atrial muscle cells were utilized to evaluate the potential effects of different ATM inhibition schemes, including earlier, middle, and late periods of intervention. Fourteen days post-AMI injury, the animals exhibited significantly increased AF inducibility, exacerbated atrial electrical/structural remodeling, reduced ventricular function and exacerbated atrial DNA damage, as evidenced by enhanced ATM/p53 signaling as well as γH2AX level. These effects were partially consistent with the enrichment results of bioinformatics analysis. Notably, the deleterious effects were ameliorated by early, but not late, administration of Ku55933. Mechanistically, inhibition of ATM signaling successfully suppressed atrial NLRP3 inflammasome-mediated pyroptotic pathway. Additionally, the results were validated in the in vitro experiments demonstrating that early inhibition of Ku55933 not only attenuated cellular ATM/p53 signaling, but also mitigated inflammatory response by reducing NLRP3 activation. Collectively, hyperactivation of ATM/p53 contributed to the pathogenesis of AF following AMI. Early intervention with ATM inhibitors substantially mitigated AF susceptibility and atrial electrical/structural remodeling, highlighting a novel therapeutic avenue against cardiac arrhythmia following AMI.

H2O2 promotes photodynamic efficacy of TMPyP4 against ovarian cancer in vitro by downregulating HIF-1α expression

Photodynamic therapy (PDT), employing photosensitizers to induce formation of reactive oxygen species (ROS) for tumor elimination, is emerging as a promising treatment modality in oncology due to its unique benefits. However, the PDT application in ovarian cancer, the most prevalent and lethal type of gynecological malignancy with a severe hypoxic microenvironment, remains unknown. This study revealed that photosensitizer TMPyP4 exhibited enhanced efficacy under H2O2 stimulation, with minimal change in cytotoxicity compared to TMPyP4 alone. The results showed that H2O2 increased ROS production induced by TMPyP4, leading to exacerbated mitochondrial dysfunction and DNA damage, ultimately inhibiting proliferation and inducing apoptosis in ovarian cancer cells. Mechanistically, H2O2 primarily enhanced the therapeutic efficacy of PDT with TMPyP4 against ovarian cancer cells by degrading HIF-1α, which subsequently modulated the HIF-1 signaling pathway, thereby alleviating the hypoxic environment in ovarian cancer cells. Our findings underscore the therapeutic potential of targeting HIF-1α within the hypoxic microenvironment for PDT in ovarian cancer and propose a novel integrated strategy for PDT treatment of this malignancy in vitro.

Triptolide induced spermatogenesis dysfunction via ferroptosis activation by promoting K63-linked GPX4 polyubiquitination in spermatocytes

Triptolide (TP) is a major bioactive compound derived from Tripterygium wilfordii Hook. F. (TwHF) known for its medicinal properties, but it also exhibits potential toxic effects. It has been demonstrated to induce severe male reproductive toxicity, yet the precise mechanism behind this remains unclear, which limits its broad clinical application. This study aimed to investigate the mechanisms underlying testicular damage and spermatogenesis dysfunction induced by TP in mice, using both mouse models and the spermatocyte-derived cell line GC-2spd. In the present study, it was found that TP displayed significant testicular microstructure damaged and spermatogenesis defects including lower concentration and abnormal morphology by promoting ROS formation, MDA production and restraining GSH level, glutathione peroxidase 4 (GPX4) expression in vivo. Furthermore, Ferrostatin-1 (FER-1), a ferroptosis inhibitor, was found to significantly reduce the accumulation of lipid peroxidation, alleviate testicular microstructural damage, and enhance spermatogenic function in mice. Besides, notably decreased cell viability, collapsed mitochondrial membrane potential, and elevated DNA damage were observed in vitro. The above-mentioned phenomenon could be reversed by pre-treatment of FER-1, indicating that ferroptosis participated in the TP-mediated spermatogenesis dysfunction. Mechanistically, TP could enhance GPX4 ubiquitin degradation via triggering K63-linked polyubiquitination of GPX4, thereby stimulating ferroptosis in spermatocytes. Functionally, GPX4 deletion intensified ferroptosis and exacerbated DNA damage in GC-2 cells, while GPX4 overexpression mitigated ferroptosis induced by TP. Overall, these findings for the first time indicated a vital role of ferroptosis in TP induced-testicular injury and spermatogenic dysfunction through promoting GPX4 K63-linked polyubiquitination, which hopefully offers a potential therapeutic avenue for TP-related male reproductive damage. In addition, this study also provides a theoretical foundation for the improved clinical application of TP or TwHF in the future.

Obstructive Sleep Apnea Syndrome Exacerbates NASH Progression via Selective Autophagy-Mediated Eepd1 Degradation.

Obstructive sleep apnea syndrome (OSAS), characterized by chronic intermittent hypoxia (CIH), is an independent risk factor for aggravating non-alcoholic steatohepatitis (NASH). The prevailing mouse model employed in CIH research is inadequate for the comprehensive exploration of the impact of CIH on NASH development due to reduced food intake observed in CIH-exposed mice, which deviates from human responses. To address this issue, a pair-feeding investigation with CIH-exposed and normoxia-exposed mice is conducted. It is revealed that CIH exposure aggravates DNA damage, leading to hepatic fibrosis and inflammation. The analysis of genome-wide association study (GWAS) data also discloses the association between Eepd1, a DNA repair enzyme, and OSAS. Furthermore, it is revealed that CIH triggered selective autophagy, leading to the autophagic degradation of Eepd1, thereby exacerbating DNA damage in hepatocytes. Notably, Eepd1 liver-specific knockout mice exhibit aggravated hepatic DNA damage and further progression of NASH. To identify a therapeutic approach for CIH-induced NASH, a drug screening is conducted and it is found that Retigabine dihydrochloride suppresses CIH-mediated Eepd1 degradation, leading to alleviated DNA damage in hepatocytes. These findings imply that targeting CIH-mediated Eepd1 degradation can be an adjunctive approach in the treatment of NASH exacerbated by OSAS.

The photoactivated antifungal activity and possible mode of action of sodium pheophorbide a on Diaporthe mahothocarpus causing leaf spot blight in Camellia oleifera

IntroductionSodium pheophorbide a (SPA) is a natural plant-derived photosensitizer, with high photoactivated antifungal activity against some phytopathogenic fungi. However, its fungicidal effect on Diaporthe mahothocarpus, a novel pathogen that causes Camellia oleifera leaf spot blight, is unclear.MethodsIn the present study, we explored its inhibitory effects on spore germination and mycelial growth of D. mahothocarpus. Then we determined its effects on the cell membrane, mycelial morphology, redox homeostasis, and cell death through bioassay. Finally, RNA-seq was used further to elucidate its mode of action at the transcriptional level.ResultsWe found that SPA effectively inhibited the growth of D. mahothocarpus, with half-maximal effective concentrations to inhibit mycelial growth and spore germination of 1.059 and 2.287 mg/mL, respectively. After 1.0 mg/mL SPA treatment, the conductivity and malondialdehyde content of D. mahothocarpus were significantly increased. Scanning electron microscopy and transmission electron microscopy indicated that SPA significantly affected the morphology and ultrastructure of D. mahothocarpus hyphae, revealing that SPA can destroy the mycelial morphology and cell structure, especially the cell membrane of D. mahothocarpus. Furthermore, transcriptome analysis revealed that SPA significantly suppressed the expression of genes involved in morphology, cell membrane permeability, and oxidative stress. Then, we also found that SPA significantly promoted the accumulation of reactive oxygen species (ROS) in of D. mahothocarpus, while it decreased the content of reduced glutathione, inhibited the enzyme activities of superoxide dismutase and catalase, and exacerbated DNA damage. Annexin V-FITC/PI staining also confirmed that 1.0 mg/mL SPA could significantly induce apoptosis and necrosis.DiscussionGenerally, SPA can induce ROS-mediated oxidative stress and cell death, thus destroying the cell membrane and hyphal morphology, and ultimately inhibiting mycelial growth, which indicates that SPA has multiple modes of action, providing a scientific basis for the use of SPA as an alternative plant-derived photoactivated fungicide against C. oleifera leaf spot blight.

COMMD10 inhibited DNA damage to promote the progression of gastric cancer

PurposeThe copper metabolism MURR1 domain 10 (COMMD10) plays a role in a variety of tumors. Here, we investigated its role in gastric cancer (GC).MethodsOnline prediction tools, quantitative real-time PCR, western blotting and immunohistochemistry were used to evaluate the expression of COMMD10 in GC. The effect of COMMD10 knockdown was investigated in the GC cell lines and in in vivo xenograft tumor experiments. Western blotting and immunofluorescence were used to explore the relationships between COMMD10 and DNA damage.ResultsThe expression of COMMD10 was upregulated in GC compared to that in para-cancerous tissue and correlated with a higher clinical TNM stage (P = 0.044) and tumor size (P = 0.0366). High COMMD10 expression predicted poor prognosis in GC. Knockdown of COMMD10 resulted in the suppression of cell proliferation, migration, and invasion, accompanied by cell cycle arrest and an elevation in apoptosis rate. Moreover, the protein expression of COMMD10 was decreased in cisplatin-induced DNA-damaged GC cells. Suppression of COMMD10 impeded DNA damage repair, intensified DNA damage, and activated ATM–p53 signaling pathway in GC. Conversely, restoration of COMMD10 levels suppressed DNA damage and activation of the ATM-p53 signaling cascade. Additionally, knockdown of COMMD10 significantly restrained the growth of GC xenograft tumors while inhibiting DNA repair, augmenting DNA damage, and activating the ATM–p53 signaling pathway in xenograft tumor tissue.ConclusionCOMMD10 is involved in DNA damage repair and maintains genomic stability in GC; knockdown of COMMD10 impedes the development of GC by exacerbating DNA damage, suggesting that COMMD10 may be new target for GC therapy.

Dual-targeted nanoparticulate drug delivery systems for enhancing triple-negative breast cancer treatment

The efficacy of DNA-damaging agents, such as the topoisomerase I inhibitor SN38, is often compromised by the robust DNA repair mechanisms in tumor cells, notably homologous recombination (HR) repair. Addressing this challenge, we introduce a novel nano-strategy utilizing binary tumor-killing mechanisms to enhance the therapeutic impact of DNA damage and mitochondrial dysfunction in cancer treatment. Our approach employs a synergistic drug pair comprising SN38 and the BET inhibitor JQ-1. We synthesized two prodrugs by conjugating linoleic acid (LA) to SN38 and JQ-1 via a cinnamaldehyde thioacetal (CT) bond, facilitating co-delivery. These prodrugs co-assemble into a nanostructure, referred to as SJNP, in an optimal synergistic ratio. SJNP was validated for its efficacy at both the cellular and tissue levels, where it primarily disrupts the transcription factor protein BRD4. This disruption leads to downregulation of BRCA1 and RAD51, impairing the HR process and exacerbating DNA damage. Additionally, SJNP releases cinnamaldehyde (CA) upon CT linkage cleavage, elevating intracellular ROS levels in a self-amplifying manner and inducing ROS-mediated mitochondrial dysfunction. Our results indicate that SJNP effectively targets murine triple-negative breast cancer (TNBC) with minimal adverse toxicity, showcasing its potential as a formidable opponent in the fight against cancer.

Paclitaxel Overload Supramolecular Oxidative Stress Nanoamplifier with a CDK12 Inhibitor for Enhanced Cancer Therapy.

Combination therapy has emerged as a promising approach for treating tumors, although there is room for improvement. This study introduced a novel strategy that combined the enhancement of apoptosis, ferroptosis, and DNA damage to improve therapeutic outcomes for prostate cancer. Specifically, we have developed a supramolecular oxidative stress nanoamplifier, which was comprised of β-cyclodextrin, paclitaxel, and ferrocene-poly(ethylene glycol). Paclitaxel within the system disrupted microtubule dynamics, inducing G2/M phase arrest and apoptosis. Concurrently, ferrocene utilized hydrogen peroxide to generate toxic hydroxyl radicals in cells through the Fenton reaction, triggering a cascade of reactive oxygen species expansion, reduction of glutathione levels, lipid peroxidation, and ferroptosis. The increased number of hydroxyl radicals and the inhibitory effect of THZ531 on DNA repair mechanisms exacerbated DNA damage within tumor cells. As expected, the supramolecular nanoparticles demonstrated excellent drug delivery ability to tumor cells or tissues, exhibited favorable biological safety in vivo, and enhanced the killing effect on prostate cancer.

Disrupting glycolysis and DNA repair in anaplastic thyroid cancer with nucleus-targeting platinum nanoclusters

Cancer cells rely on aerobic glycolysis and DNA repair signals to drive tumor growth and develop drug resistance. Yet, fine-tuning aerobic glycolysis with the assist of nanotechnology, for example, dampening lactate dehydrogenase (LDH) for cancer cell metabolic reprograming remains to be investigated. Here we focus on anaplastic thyroid cancer (ATC) as an extremely malignant cancer with the high expression of LDH, and develop a pH-responsive and nucleus-targeting platinum nanocluster (Pt@TAT/sPEG) to simultaneously targets LDH and exacerbates DNA damage. Pt@TAT/sPEG effectively disrupts LDH activity, reducing lactate production and ATP levels, and meanwhile induces ROS production, DNA damage, and apoptosis in ATC tumor cells. We found Pt@TAT/sPEG also blocks nucleotide excision repair pathway and achieves effective tumor cell killing. In an orthotopic ATC xenograft model, Pt@TAT/sPEG demonstrates superior tumor growth suppression compared to Pt@sPEG and cisplatin. This nanostrategy offers a feasible approach to simultaneously inhibit glycolysis and DNA repair for metabolic reprogramming and enhanced tumor chemotherapy.

Dual p38MAPK and MEK inhibition disrupts adaptive chemoresistance in mesenchymal glioblastoma to temozolomide.

Precision treatment of glioblastoma is increasingly focused on molecular subtyping, with the mesenchymal subtype particularly resistant to temozolomide. Here, we aim to develop a targeted therapy for temozolomide resensitization in the mesenchymal subtype. We integrated kinomic profiles and kinase inhibitor screens from patient-derived proneural and mesenchymal glioma-propagating cells and public clinical datasets to identify key protein kinases implicated in temozolomide resistance. RNAseq, apoptosis assays, and comet assays were used to examine the role of p38MAPK signaling and adaptive chemoresistance in mesenchymal cells. The efficacy of dual p38MAPK and MEK/ERK inhibition using ralimetinib (selective orally active p38MAPK inhibitor; phase I/II for glioblastoma) and binimetinib (approved MEK1/2 inhibitor for melanoma; phase II for high-grade glioma) in primary and recurrent mesenchymal tumors was evaluated using an intracranial patient-derived tumor xenograft model, focusing on survival analysis. Our transcriptomic-kinomic integrative analysis revealed p38MAPK as the prime target whose gene signature enables patient stratification based on their molecular subtypes and provides prognostic value. Repurposed p38MAPK inhibitors synergize favorably with temozolomide to promote intracellular retention of temozolomide and exacerbate DNA damage. Mesenchymal cells exhibit adaptive chemoresistance to p38MAPK inhibition through a pH-/calcium-mediated MEK/ERK pathway. Dual p38MAPK and MEK inhibition effectively maintain temozolomide sensitivity in primary and recurrent intracranial mesenchymal glioblastoma xenografts. Temozolomide resistance in mesenchymal glioblastoma is associated with p38MAPK activation. Adaptive chemoresistance in p38MAPK-resistant cells is mediated by MEK/ERK signaling. Adjuvant therapy with dual p38MAPK and MEK inhibition prolongs temozolomide sensitivity, which can be developed into a precision therapy for the mesenchymal subtype.

The dimeric deubiquitinase USP28 integrates 53BP1 and MYC functions to limit DNA damage.

DNA replication is a major source of endogenous DNA damage in tumor cells and a key target of cellular response to genotoxic stress. DNA replication can be deregulated by oncoproteins, such as transcription factor MYC, aberrantly activated in many human cancers. MYC is stringently regulated by the ubiquitin system - for example, ubiquitination controls recruitment of the elongation factor PAF1c, instrumental in MYC activity. Curiously, a key MYC-targeting deubiquitinase USP28 also controls cellular response to DNA damage via the mediator protein 53BP1. USP28 forms stable dimers, but the biological role of USP28 dimerization is unknown. We show here that dimerization limits USP28 activity and restricts recruitment of PAF1c by MYC. Expression of monomeric USP28 stabilizes MYC and promotes PAF1c recruitment, leading to ectopic DNA synthesis and replication-associated DNA damage. USP28 dimerization is stimulated by 53BP1, which selectively binds USP28 dimers. Genotoxic stress diminishes 53BP1-USP28 interaction, promotes disassembly of USP28 dimers and stimulates PAF1c recruitment by MYC. This triggers firing of DNA replication origins during early response to genotoxins and exacerbates DNA damage. We propose that dimerization of USP28 prevents ectopic DNA replication at transcriptionally active chromatin to maintain genome stability.

Abstract IA020: Micronuclei are a nexus of DNA damage signaling and genomic instability

Abstract Micronuclei have classically been considered inert biomarkers of genomic instability arising from failed DNA damage repair and chromosome segregation errors in mitosis. Work from several groups including our own have now demonstrated that micronuclei are active contributors to the cellular response to DNA damage by driving chromothripsis and through induction of anti-viral gene expression programs mediated by the cGAS-STING pathway. We now show that the specific DNA damage type leading to micronuclei formation influences the capacity for cGAS localization and activation. This arises in part due to discrete chromatin features, present prior to DNA damage induction, that are retained in micronuclei several days after their formation. Together these data demonstrate that micronuclei connect the pre-damage chromatin status and the chromatin context of micronuclei-inciting lesions to the long-term signaling outcomes important for anti-tumor immunity. This finding implies that micronuclei represent archives for the nature of DNA repair failure and downstream signaling consequences. Based on this premise we will present our efforts in micronuclear proteomics where we uncover common features of micronuclei including splicing deficiencies. Such deficiencies presage exacerbated MN-associated DNA damage that is upstream of chromothripsis. These studies have direct implications for how cells sense the aftermath of DNA damage and how micronuclei contribute to ongoing genomic instability. Citation Format: Shane M. Harding. Micronuclei are a nexus of DNA damage signaling and genomic instability [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr IA020.