Search Results (293)

The ataxia–telangiectasia-mutated (ATM) protein plays a crucial role in the DNA damage response, particularly in the homologous recombination (HR) pathway. This study aimed to assess the impact of deleterious ATM variants on homologous recombination deficiency (HRD) and response to PARP inhibitors (PARPi) in melanoma patients, using a cell line established from melanoma tissue of a patient carrying the c.5979_5983del germline ATM variant. Despite proven loss of heterozygosity, lack of ATM activation, and HRD, our model did not show sensitivity to PARPi. We assessed the potential contribution of the Schlafen family member 11 (SLFN11) helicase, whose expression is inversely correlated with PARPi sensitivity in other cancers, to the observed resistance. The ATM mutant cell line lacked SLFN11 expression and featured hypermethylation-mediated silencing of the SLFN11 promoter. While sensitive to the ATR inhibitor (ATRi), the addition of ATRi to PARPi was unable to overcome the resistance. Our findings suggest that ATM mutational status and HRD alone do not adequately account for variations in sensitivity to PARPi in our model. A comprehensive approach is essential for optimizing the exploitation of DNA repair defects and ultimately improving clinical outcomes for melanoma patients. Full article

Lysosomal storage disorders (LSDs) are inherited metabolic conditions characterized by lysosomal enzyme deficiencies leading to substrate accumulation. As genetic diseases, LSDs can be treated with gene therapies (GT), including the CRISPR/Cas systems. The CRISPR/Cas systems enable precise and programmable genome editing, leading to targeted modifications at specific genomic loci. While the classical CRISPR/Cas9 system has been extensively used to generate LSD disease models and correct disease-associated genetic alterations through homologous recombination (HR), recently described Cas proteins as well as CRISPR/Cas9-derived strategies such as base editing, prime editing, and homology-independent targeted integration (HITI) offer a novel way to develop innovative treatments for LSDs. The direct administration of the CRISPR/Cas9 system remains the primary strategy evaluated in several LSDs; nevertheless, the ex vivo CRISPR/Cas9-based approach has been recently explored, primarily in central nervous system-affecting LSDs. Ex vivo approaches involve genetically modifying, in theory, any patient cells in the laboratory and reintroducing them into the patient to provide a therapeutic effect. This manuscript reviews the molecular aspects of the CRISPR/Cas technology and its implementation in ex vivo strategies for LSDs while discussing novel approaches beyond the classical CRISPR/Cas9 system. Full article

Targeted radionuclide therapy (TRT) utilizes radiopharmaceuticals to deliver radiation directly to cancer cells while sparing healthy tissues. Beyond the absorbed dose of ablative radiation, TRT induces non-targeted effects (NTEs) that significantly enhance its therapeutic efficacy. These effects include radiation-induced bystander effects (RIBEs), abscopal effects (AEs), radiation-induced genomic instability (RIGI), and adaptive responses, which collectively influence the behavior of cancer cells and the tumor microenvironment (TME). TRT also modulates immune responses, promoting immune-mediated cell death and enhancing the efficacy of combination therapies, such as the use of immune checkpoint inhibitors. The molecular mechanisms underlying TRT involve DNA damage, oxidative stress, and apoptosis, with repair pathways like homologous recombination (HR) and non-homologous end joining (NHEJ) playing critical roles. However, challenges such as tumor heterogeneity, hypoxia, and radioresistance limit the effectiveness of this approach. Advances in theranostics, which integrate diagnostic imaging with TRT, have enabled personalized treatment approaches, while artificial intelligence and improved dosimetry offer potential for treatment optimization. Despite the significant survival benefits of TRT in prostate cancer and neuroendocrine tumors, 30–40% of patients remain unresponsive, which highlights the need for further research into molecular pathways, long-term effects, and combined therapies. This review outlines the dual mechanisms of TRT, direct toxicity and NTEs, and discusses strategies to enhance its efficacy and expand its use in oncology. Full article

Hypoxia, characterized by a reduction in tissue oxygen levels, is a hallmark of many solid tumors and affects a range of cellular processes, including DNA repair. In low-oxygen conditions, cancer cells often suppress key DNA repair pathways such as homologous recombination (HR), leading to the accumulation of DNA damage and increased genomic instability. These changes not only drive tumor progression but also contribute to resistance against conventional therapies. Hypoxia significantly reduces the effectiveness of oxygen-dependent treatments, including radiotherapy and many chemotherapeutic agents. To address this limitation, bioreductive drugs have been developed that become selectively activated in hypoxic environments, providing targeted cytotoxic effects within oxygen-deprived tumor regions. Additionally, the rapid growth of tumors often results in disorganized and inefficient vasculature, further impairing the delivery of oxygen and therapeutic agents. This review explores the molecular mechanisms by which hypoxia disrupts DNA repair and contributes to treatment resistance. It also presents emerging therapeutic strategies aimed at targeting the hypoxic tumor microenvironment to improve treatment efficacy and patient outcomes. Full article

PARP inhibitors (PARPi), alone or in combination with androgen receptor signaling inhibitors (ARSi), have shown clinical benefit in metastatic castration-resistant prostate cancer (mCRPC), particularly in tumors with homologous recombination repair (HRR) gene alterations. Recent data from the TALAPRO-2 trial complete the current evidence on PARPi–ARSi combination strategies in this setting. Background/Objectives: To evaluate the efficacy and safety of PARPi-based therapies—monotherapy and combination with ARSi—in patients with mCRPC, focusing on molecular subgroups defined by DNA repair alterations. Methods: We conducted a systematic review and meta-analysis of phase III randomized controlled trials (RCTs) assessing PARPi as monotherapy or in combination with ARSi. Searches were performed in PubMed, EMBASE, the Cochrane Library, and oncology conference proceedings up to February 2025. Outcomes included radiographic progression-free survival (rPFS), overall survival (OS), second progression-free survival (PFS2), and grade ≥3 adverse events (AEs). Data were pooled using a random-effects model, with subgroup analyses by DNA repair status. Results: Five RCTs (n = 2921) were I confirmincluded: three on combination therapy (n = 2271) and two on monotherapy (n = 650). Combination therapy improved rPFS in the ITT (HR = 0.64; 95% CI: 0.56–0.74), HRRm (HR = 0.55; 95% CI: 0.44–0.68), and BRCAm (HR = 0.33; 95% CI: 0.18–0.58) subgroups. OS was also improved in the ITT (HR = 0.80; 95% CI: 0.70–0.92), HRRm (HR = 0.68; 95% CI: 0.55–0.83), and BRCAm (HR = 0.54; 95% CI: 0.34–0.85) groups. No benefit was observed in non-HRRm patients. PFS2 favored combination therapy (HR = 0.77; 95% CI: 0.64–0.91). Grade ≥3 AEs were more frequent (RR = 1.44; 95% CI: 1.20–1.73). Monotherapy improved rPFS in ITT (HR = 0.46; 95% CI: 0.20–0.81) and BRCAm (HR = 0.33; 95% CI: 0.15–0.75); OS benefit was seen only in BRCAm (HR = 0.73; 95% CI: 0.57–0.95). Conclusions: PARPi therapies improve outcomes mainly in HRR- and BRCA-mutated mCRPC. Molecular selection is key to optimizing benefit and minimizing toxicity. Further research on the activity of PARPi combinations in non-HRR mutated mCRPC is needed to better understand the underlying mechanisms of efficacy. Full article

Epigenetic modifications are heritable, reversible alterations that causally reshape chromatin architecture and thereby influence DNA repair without changing nucleotide sequence. DNA methylation, histone modifications and non-coding RNAs profoundly influence DNA repair mechanisms and genomic stability. Aberrant epigenetic patterns in cancer compromise DNA damage recognition and repair, therefore impairing homologous recombination (HR), non-homologous end joining (NHEJ), and base excision repair (BER) by suppressing key repair genes and lowering access to repair sites. Then it is dissected how loss-of-function mutations in Switch/Sucrose non-fermentable, imitation switch and CHD (Chromodomain helicase DNA-binding) chromatin-remodeling complexes impair nucleosome repositioning, preventing effective damage sensing and assembly of repair machinery. Non-coding RNAs contribute to epigenetic silencing at DNA break sites, exacerbating repair deficiencies. This review evaluates recent advances concerning epigenetic dysfunction and DNA repair impairment. It is also highlighted that nanoparticle-mediated delivery strategies are designed to overcome pharmacologic resistance. It is presented how epigenetic dysregulation of DNA repair can guide more effective and drug-resistant cancer therapies. Full article

Background: Breast cancer (BC) is the most common cancer in women worldwide. Much progress has been made to improve treatment options for patients suffering from the disease, including a novel therapy—Poly (ADP-ribose) polymerase inhibitor (PARPi) that specifically targets tumors with deficiencies in the Homologous Recombination (HR) DNA repair pathway. To benefit better from conventional therapy, many patients seek alternative supplementation, with 20–30% of cancer patients using herbal medication on top of their regular treatment. An example of such easily available over-the-counter supplements is curcumin, a natural compound derived from turmeric (Curcuma longa). Various studies reported the potential HR deficiency (HRD) inducing effect of curcumin in cancer cells. Methods: Eight BrC and three normal cell lines and a BrC PDX model were used to evaluate the effect of curcumin on RAD51 ionizing radiation-induced focus (IRIF) formation. Three breast BrC cell lines underwent further analysis using the BRCA2 Western blot technique. To assess cell survival after treatment with curcumin and/or PARPi, a clonogenic survival assay was performed on both normal and cancerous cell lines. Results: Curcumin treatment led to a reduction in RAD51 IRIF formation capacity across all tested models. A decrease in BRCA2 levels was observed in the tested cell lines. Our findings demonstrate that HRD can be induced in both cancerous and normal cells, suggesting that curcumin treatment may increase the risk of toxicity when combined with PARPi therapy. Conclusions: The use of curcumin in combination with certain anti-cancer treatments should not be implemented without extensive monitoring for deleterious side effects. Full article

Hereditary breast and ovarian cancer (HBOC) syndrome is primarily associated with mutations in BRCA1 and BRCA2, but increasing evidence links it to other malignancies, including male breast, prostate, and pancreatic cancers. Advances in genetic testing have led to the use of multigene panels, revealing that additional genes contribute to HBOC risk. We tested 280 patients with suspected HBOC using a multigene panel including BRCA1, BRCA2, and other genes involved in homologous recombination (HR) and additional DNA repair mechanisms. Variants were classified as pathogenic variants (PVs), variants of uncertain significance (VUS), or novel. In silico tools were used to predict the clinical relevance of VUS and novel variants. The clinical phenotype of families carrying a PV was evaluated. PVs were identified in 19.3% of patients: 8.9% in BRCA1/2 and 10.4% in other genes, mainly CHEK2, ATM, PALB2, and BRIP1. An additional 1.8% of cases harbored likely pathogenic VUS or novel variants according to bioinformatic prediction. Breast and ovarian cancer were the most frequent malignancies in our population, both in the BRCA group and in those with PVs in other susceptibility genes. Broad genetic testing beyond BRCA improves HBOC diagnostics, supports identification of at-risk families, and enables more personalized surveillance and treatment. Full article

Trichomonas vaginalis, the protozoan responsible for trichomoniasis, encounters fluctuating levels of metal cations in the male urogenital tract, notably zinc (Zn²⁺) and cadmium (Cd²⁺), which may induce genotoxic stress. While zinc is a key physiological component of the male reproductive tract, both Zn²⁺ and Cd²⁺ can become genotoxic at elevated concentrations. However, their effect on DNA repair mechanisms in T. vaginalis remains poorly understood. This study characterizes, for the first time, the expression and modulation of the recombinase TvRAD51, a homologous recombination (HR) key enzyme, in response to UV irradiation and sublethal concentrations of Zn²⁺ (1.6 mM) and Cd²⁺ (0.1 mM). In silico analyses confirmed the presence and conserved structure of the tvrad51 gene and its interaction with HR-related proteins, such as TvBLM and TvBRCA2. Quantitative RT-PCR, Western blot, and immunofluorescence assays revealed that TvRAD51 is upregulated at both transcript and protein levels following UV- and cation-induced DNA damage, with distinct temporal expression patterns for Zn²⁺ and Cd²⁺ exposure. Notably, TvRAD51 showed nuclear localization at early time points post-exposure, suggesting active participation in DNA repair processes. These findings demonstrate that TvRAD51 is a central component of the genotoxic stress response in T. vaginalis, potentially contributing to parasite survival and adaptation in hostile environments through homologous recombination repair pathways. Full article

Background: Deinococcus radiodurans, renowned for its exceptional resistance to radiation, provides a robust model for elucidating cellular stress responses and DNA repair mechanisms. Previous studies have established PprI as a key regulator contributing to radiation resistance through its involvement in DNA damage repair pathways, oxidative stress response, and metabolic regulation. Methods: Building upon these foundations, our study employs label-free quantitative (LFQ) proteomics coupled with high-resolution mass spectrometry to systematically map pprI deletion protein networks by comparing the global proteomic profiles of pprI knockout and wild-type D. radiodurans strains. Results: Under stringent screening criteria, we identified 719 significantly higher and 281 significantly lower abundant proteins in the knockout strain compared to wild-type strains. Functional analysis revealed that PprI deficiency disrupts homologous recombination (HR) repair, activates nucleotide excision repair (NER) and base excision repair (BER) as a compensatory mechanism, and impairs Mn/Fe homeostasis and carotenoid biosynthesis, leading to increased oxidative stress. Furthermore, PprI deficiency induces significant metabolic reprogramming, including impaired purine synthesis, compromised cell wall integrity, etc. Conclusions: These proteomic findings delineate the extensive regulatory network influenced by PprI, revealing coordinated perturbations across multiple stress response systems when PprI is absent. Full article

Background: Niraparib is an oral poly (adenosine diphosphate-ribose) polymerase inhibitor with promising activity for patients with advanced breast cancer harboring germline BRCA1/2 mutations. Methods: LUZERN (NCT04240106) was a multicenter, open-label, Simon’s two-stage, phase II clinical trial evaluating the efficacy and safety of niraparib with aromatase inhibitors (AIs) for patients with HR-positive/HER2-negative advanced breast cancer with either a germline BRCA1/2 mutation (cohort A) or germline BRCA1/2 wild-type and homologous recombination deficiency (exploratory cohort B). Eligible patients received ≤1 line of chemotherapy and 1–2 prior lines of endocrine therapy for advanced disease with secondary resistance to the last AI-based regimen. Patients received niraparib (300 mg or 200 mg) plus an AI. The primary endpoint was the clinical benefit rate (CBR) in cohort A. Results: Between June 2020 and November 2022, 14 patients were enrolled in cohort A (n = 6 for stage I, n = 8 for stage II) and no patients were enrolled in cohort B. One patient was excluded from the efficacy analysis due to no prior AI treatment. Nearly all patients (92.9%) previously received a cyclin-dependent kinase 4/6 inhibitor, but no patients had received prior platinum-based chemotherapy. Median follow-up was 16.7 months (range: 13.2–18.2). The CBR was 46.2% (95% CI: 19.2–74.9), meeting the primary endpoint. Median progression-free survival was 5.5 months (95% CI: 1.9–8.5), and median overall survival was 18.1 months (95% CI: 9.7–NE). The safety profile was consistent with the known toxicity of both drugs. Conclusions: Niraparib combined with an AI has encouraging antitumor activity and a manageable safety profile in patients with AI-resistant HR-positive/HER2-negative advanced breast cancer with germline BRCA1/2 mutations. Full article

As an important class of microorganisms, filamentous fungi have crucial roles in protein secretion, secondary metabolite production and environmental pollution control. However, characteristics such as apical growth, heterokaryon, low homologous recombination (HR) efficiency and the scarcity of genetic markers mean that the application of traditional gene editing technology in filamentous fungi faces great challenges. The introduction of the RNA-mediated CRISPR/Cas (clustered regularly interspaced short palindromic repeat/CRlSPR-associated protein) system in filamentous fungi in recent years has revolutionized gene editing in filamentous fungi. In addition, the continuously expressed CRISPR system has significantly improved the editing efficiency, while the optimized sgRNA design and reduced cas9 concentration have effectively reduced the off-target effect, further enhancing the safety and reliability of the technology. In this review, we systematically analyze the molecular mechanism and regulatory factors of CRISPR/Cas9, focus on the optimization of its expression system and the improvement of the transformation efficiency in filamentous fungi, and reveal the core regulatory roles of HR and non-homologous end-joining (NHEJ) pathways in gene editing. Based on the analysis of various filamentous fungi applications, this review reveals the outstanding advantages of CRISPR/Cas9 in the enhancement of protein secretion, addresses the reconstruction of secondary metabolic pathways and pollutant degradation in the past decade, and provides a theoretical basis and practical guidance for the optimization of the technology and engineering applications. Full article

DNA damage has emerged as a critical factor in fuelling the development and progression of cancer. DNA damage response (DDR) pathways lie at the crux of cell fate decisions following DNA damage induction, which can either trigger the repair of detrimental DNA lesions to protect cancer cells or induce the cell death machinery to eliminate damaged cells. Cytoskeletal dynamics have a critical role to play and influence the proper function of DDR pathways. Microfilaments, intermediate filaments, microtubules, and their associated proteins are well involved in the DDR. For instance, they are not only implicated in the recruitment of specific DDR molecules to the sites of DNA damage but also in the regulation of the mobility of the damaged DNA to repair sites in the periphery of the nucleus. The exquisite roles that these cytoskeletal proteins play in different DDR pathways, such as non-homologous end joining (NHEJ), homologous recombination (HR), base excision repair (BER), and nucleotide excision repair (NER), in cancer cells are extensively discussed in this review. Many cancer treatments are reliant upon inducing DNA damage in cancer cells to eliminate them; thus, it is important to shed light on factors that could affect their efficacy. Although the cytoskeleton is intricately involved in the DDR process, this has often been overlooked in cancer research and has not been exploited in developing DDR-targeting cancer therapy. Understanding the interplay between the cytoskeleton and the DDR in cancer will then provide insights into improving the development of cancer therapies that can leverage the synergistic action of DDR inhibitors and cytoskeleton-targeting agents. Full article

Background/Objectives: PARP inhibitors (PARPi) are pivotal to treating homologous recombination repair-deficient (HRD) cancers, particularly BRCA1/2-mutated ovarian and breast cancers. However, most ovarian and breast cancers harbor wild-type (WT) BRCA1/2, limiting PARPi eligibility. This study aims to identify an approved drug that could induce a BRCAness phenotype, thereby sensitizing WT BRCA cancers to PARPi. Methods: Ovarian and breast cancer cell lines with WT BRCA1/2 were treated with ivosidenib. HR repair efficiency was assessed via RAD51 foci formation and reporter assays. Synthetic lethality with PARPi was evaluated using viability and colony formation assays. Mechanistic studies included RNA-binding protein pulldown, co-immunoprecipitation, and functional analyses of DNA repair pathways. YTHDC2′s role in HR was investigated through siRNA knockdown and rescue experiments. Results: Ivosidenib significantly reduced HR repair efficiency and sensitized cells to PARPi, inducing synthetic lethality. Mechanistically, ivosidenib directly bound YTHDC2, an m6A reader critical for HR. This interaction disrupted YTHDC2′s ability to promote DNA double-strand break repair via HR, evidenced by impaired recruitment of repair proteins (e.g., BRCA1, RAD51) and accumulation of DNA damage (γH2AX foci). YTHDC2 knockdown phenocopied ivosidenib effects, while overexpression rescued HR defects. Conclusions: Ivosidenib induces BRCAness in WT BRCA ovarian and breast cancers by targeting YTHDC2, thereby suppressing HR repair and enhancing PARPi sensitivity. This uncovers a novel, metabolism-independent mechanism of ivosidenib, repositioning it as a therapeutic agent for HRD tumors. These findings propose a strategy to expand PARPi eligibility to WT BRCA cancers, addressing a critical unmet need in oncology. Full article

Cancers that arise from germline mutations of breast cancer associated gene 1 (BRCA1), which is a crucial player in homologous recombination (HR) DNA repair, are vulnerable to DNA-damaging agents such as platinum and PARP inhibitors (PARPis). Increasing evidence suggests that BRCA1 is an essential driver of all phases of the cell cycle, thereby maintaining orderly steps during cell cycle progression. Specifically, loss of BRCA1 activity causes the S-phase, G₂/M, spindle checkpoints, and centrosome duplication to be dysregulated, thereby blocking cell proliferation and inducing apoptosis. In vertebrates, loss of HR genes such as BRCA1 and/or BRCA2 is lethal, since HR is a prerequisite for genome integrity. Thus, cancer cells utilize alternative DNA repair pathways such as non-homologous end joining (NHEJ) to cope with the loss of BRCA1 function. In this review, we attempt to update and discuss how these novel components are crucial for regulating DNA damage repair (DDR) in BRCA1-deficient cancers. Full article