NAR cancer最新文献

Poly(ADP-ribose) polymerases 1 and 2 (PARP1/PARP2), and poly(ADP-ribose) glycohydrolase (PARG), modulate the level of poly(ADP-ribose) (PAR), a post-translational protein modification, in response to DNA damage or replication stress. Here, we find that replication-dependent and PARP1/PARP2-mediated PARylation recruits the base excision repair (BER)/single-strand break repair (SSBR) scaffold protein XRCC1 and the associated factors DNA polymerase β (POLB), aprataxin (APTX), and DNA ligase isoform 3 (LIG3). Further, these BER/SSBR proteins promote resistance to inhibitors of PARP1/PARP2 and PARG, as loss of these proteins sensitizes glioblastoma and ovarian cancer cells to each. In addition, depletion of these replication-associated BER/SSBR factors leads to enhanced PAR levels and PARG inhibitor-induced activation of the ATR/CHK1 S-phase checkpoint kinases. Both PARG inhibition and ATR inhibition lead to elevated ATM- and DNA-PK-dependent KAP1 phosphorylation. In turn, inhibition of either ATR or CHK1 enhances the cellular response to PARG inhibitors. Finally, inhibition of the ATR regulators PRMT1 or PRMT5 synergizes with PARG inhibition, implicating replication-associated BER/SSBR and PARylation in the activation of the PRMT1/PRMT5/ATR axis. This study highlights the role of BER/SSBR in protecting the cell during S-phase to suppress PARylation-induced checkpoint activation, which may suggest a potential intervention strategy for PARG inhibitor-resistant tumors.

MutLα, a heterodimer of MLH1 and PMS2, plays a key role in DNA mismatch repair (MMR), which maintains genomic stability by correcting replication errors. Loss of MLH1 function causes MMR deficiency (MMRd), leading to elevated mutation rates and increased cancer susceptibility. However, MMRd can offer a therapeutic advantage, as high tumour mutational burden enhances the efficacy of immune checkpoint inhibition. MMR also drives somatic expansion of CAG repeats linked to Huntington's disease (HD) pathogenesis. The C-terminal domain (CTD) of MLH1 contains at least two distinct protein-protein interaction (PPI) sites. The S1 site supports heterodimerization with the PMS2 endonuclease, whereas the S2 site interacts with MIP-boxes present in MMR-associated factors (EXO1, MSH3) and in the DNA repair nuclease FAN1. Here, using MLH1-S2 mutant cell models and synthetic FAN1-derived peptides containing two adjacent MLH1-binding motifs (MIP and MIM), we demonstrate that selective disruption of MLH1 PPIs impairs MMR in vitro. We further reveal that the peptide is able to inhibit the latent endonuclease activity of recombinant MutLα, possibly via competing with a putative MIM within PMS2. Our findings define key PPI interfaces within the MLH1(CTD) that govern MMR activity and may offer novel therapeutic opportunities to exploit MMRd in cancer and HD.

2'-deoxyuridine (dU) is a common DNA lesion resulting from cytosine deamination and from dUMP incorporation by DNA polymerases, both of which are prevalent in cancer. The primary mechanism that repairs dU lesions in genomic DNA is base excision repair initiated by Uracil-DNA Glycosylase 2 (UNG2). We generated Ung knockout mouse B16 melanoma cells to investigate the consequences of UNG deficiency in a well-characterized, immunocompetent, syngeneic mouse cancer model. We show that UNG-deficient (ΔUNG) B16 tumors exhibited T cell-dependent, delayed growth in vivo and were more responsive to anti-PD-L1 therapy. Immune profiling revealed reduced CD8⁺ T cell infiltration but augmented IFN-γ-competent effector CD4⁺ T cells in ΔUNG tumors. In vitro, ΔUNG tumor cells exhibited strongly suppressed cell-intrinsic type-I interferon, type-II interferon, and inflammatory signaling gene expression signatures as well as altered cytokine and chemokine secretion. In vivo, ΔUNG tumors exhibited a modified inflammatory cytokine and chemokine milieu. Furthermore, ΔUNG tumor cells had altered sensitivity to exogenous interferons in vitro, with increased sensitivity to IFN-γ but decreased sensitivity to IFN-α/β. Collectively, our data show that tumor-cell-specific UNG deficiency results in an altered tumor microenvironment in vivo and provide proof of concept for the use of UNG inhibitors to modulate inflammatory pathways in tumors.

Triple-negative breast cancer (TNBC), defined by the absence of ER, PR, and Her2, impacts over 46 000 U.S. women annually, disproportionately affecting minority ethnic groups and individuals with BRCA mutations. Despite advancements such as PARP inhibitors, TNBC remains highly aggressive, with frequent recurrences and a 50% mortality rate within four years, underscoring the urgent need for more effective targeted therapies. MicroRNAs (miRNAs) represent a novel therapeutic approach. In TNBC, overexpressed miR-21 drives tumor progression, immune evasion, treatment resistance, and metastasis. Targeted miR-21 inhibition could curb these effects while minimizing harm to normal cells. We developed a peptide-conjugated miR-21 inhibitor targeting TNBC cells via the overexpressed IGF1 receptor (IGF1R), associated with poor prognosis. Using aminomethyl-bridged nucleic acid (BNA) chemistry, a serum-stable anti-miR-21 RNA analog was designed and tested for its effects on TNBC cell proliferation, apoptosis, tumor suppressor expression, and immune checkpoint regulation. Conjugation to an IGF1 peptide analog improved delivery, demonstrating tumor-specific biodistribution, efficacy, and safety in TNBC-bearing mice. The miR-21 inhibitor-peptide conjugate reduced proliferation, induced apoptosis, elevated tumor suppressors, and suppressed immune checkpoints in TNBC cell lines. In vivo, it concentrated in tumors, inhibited tumor growth, and showed no detectable liver or kidney toxicity at the tested dose, supporting therapeutic potential.

The alternative lengthening of telomeres (ALT) pathway is a telomerase-independent telomere maintenance mechanism leveraged by a subset of human cancers. In these tumors, telomere DNA synthesis is achieved via homologous recombination-based mechanisms. ALT-positive tumors harbor distinctive hallmarks, including heterogeneous telomere lengths, the presence of ALT-associated PML bodies, extrachromosomal telomeric repeats, telomere fragility, and mitotic DNA synthesis. These features reflect underlying replication stress and deregulated DNA repair mechanisms. ALT is associated with various tumor types and can often contribute to worsening the patient's prognosis. Strikingly, ALT cancers are particularly enriched in childhood cancers, especially in high-grade gliomas, neuroblastoma, and osteosarcomas, three cancer types that are very common in children. Here, we provide a comprehensive review of the DNA repair factors that drive ALT activation and maintenance and explore emerging therapeutic opportunities associated with the selective dependence of ALT cancer cells on these specific DNA damage response factors. We aim to promote a growing interest in deciphering the DNA-repair-dependent mechanisms of ALT, ultimately helping to build a foundation for the discovery of novel therapeutics against aggressive ALT tumors, for which prognosis is particularly poor and treatments are currently severely lacking.

Cancer cells display dysregulated metabolic programs, which result in excessive reactive oxygen species (ROS) leading to oxidative stress. ROS reaction with macromolecules, including proteins, lipids, and nucleic acids, can result in damaging modifications with alter or nullify function. While tumors upregulate antioxidant defences for viability, they remain sensitive to additional oxidant perturbations. Because of this, therapies that overwhelm cancers with ROS are gaining clinical attention due to their potential targeting of diseased tissue over normal tissue. In this review, we summarize the available genetic tools for targeted ROS production in both cellular and organismal models, specifically focusing on tools with spatial and temporal control. Largely, these approaches use light to activate a chromophore in the cell, which produces ROS for protein inactivation, DNA damage, or cell ablation. These photosensitizers are genetically fused to target proteins of interest, and all have advantages and disadvantages for both basic and translational research, which we discuss below.

Apurinic/apyrimidinic endonucleases - APE1 and APE2 are central to genome maintenance and the cellular DNA damage response, with expanding relevance in cancer biology. APE1 is the primary endonuclease in base excision repair and functions as a redox coactivator of transcription factors. In contrast, APE2 exhibits PCNA dependent 3'-5' exonuclease and 3'-phosphodiesterase activities, contributing to microhomology-mediated end joining, ATR-Chk1 activation, and immunoglobulin diversification. Both enzymes are often deregulated in cancer: APE1 is frequently overexpressed, drives tumor progression and chemoresistance, while APE2 is similarly upregulated in multiple malignancies. APE1 can be targeted by redox-specific or endonuclease inhibitors, with early clinical evidence of biological activity and tolerability. Although APE2-specific inhibitors remain in early development, emerging synthetic lethality data and preclinical studies highlight APE2 as a novel clinical target in breast cancer type 1/2 susceptibility (BRCA)-mutated cancers. This review discusses the structural and functional roles of APE1 and APE2, their contributions to cancer biology and therapeutics, recent advances in inhibitor development, and future strategies for precision oncology.

Oxidative DNA damage is a major driver of genome instability and human disease. Among the various types of oxidative DNA base lesions, 8-oxo-7,8-dihydroguanine (8oxoG) is particularly prevalent due to guanine's low oxidation potential and the abundance of guanine-rich (G-rich) sequences across the genome. Structure-forming repeat sequences, which are commonly G-rich, can adopt alternative DNA secondary structures that further expose nucleobases to oxidative damage. The base excision repair (BER) pathway is primarily responsible for the repair of 8oxoG lesions; however, the complex topologies and dynamic conformations formed by these repeat sequences present challenges for complete repair. Inefficient BER within these structures can lead to DNA strand breaks, mutations, and large chromosomal rearrangements, all of which are associated with human disease. Notably, structure-forming repeat sequences are often enriched at regulatory genomic regions, where BER can directly influence processes such as replication and transcription. This review summarizes current insights into BER activity within oxidatively damaged structure-forming repeat sequences and highlights how repair efficiency within these sequences impacts genome stability and disease.

Small base lesions in DNA are primarily repaired through the base excision repair pathway, which is initiated by DNA glycosylases. This review focuses on single-strand selective monofunctional uracil-DNA glycosylase (SMUG1), an enzyme whose name incompletely captures its broader biological roles. SMUG1 excises a wide range of substrates beyond uracil, shows a preference for double-stranded DNA, and has been reported to be a bifunctional DNA glycosylase with a weak lyase activity. Moreover, SMUG1 plays roles extending beyond DNA repair, including functions in RNA quality control and RNA biogenesis. Recently, genetic interactions have been described between SMUG1 and proteins that safeguard stressed replication forks, implicating a function for SMUG1 in cancer cell biology. Understanding SMUG1's full repertoire is key to uncovering its role in genome maintenance and unlocking its potential as a therapeutic target. Here, we review the biochemical properties reported for SMUG1 and its distinct functions from other uracil-DNA glycosylases in vivo. We also highlight the emerging role of SMUG1 in cancer cells and its potential as a therapeutic target, emphasizing the need to define the genetic and molecular contexts in which its modulation may be beneficial.

Acquired resistance presents a major challenge for targeted therapies, with initially responsive tumors eventually reverting underlying vulnerabilities. Our group recently reported that cancers harboring isocitrate dehydrogenase 1/2 (IDH1/2) mutations have defective recruitment of homology-directed repair (HDR) factors to sites of DNA damage and consequent sensitivity to poly(ADP-ribose) polymerase inhibitors (PARPi), a vulnerability that is being tested in clinical trials. To probe potential mechanisms by which resistance to PARPi might arise in this setting, we modeled PARPi resistance in IDH-mutant tumors via serial transplantation of patient-derived xenografts in mice treated with PARPi. An analysis of candidate DNA repair factors in these resistant tumor populations identified downregulation of two end protection factors that are negative regulators of HDR, 53BP1, and REV7. Knockout of these factors by CRISPR-Cas9 in IDH1-mutant cancer cells conferred robust resistance to PARPi and restored HDR capacity. To overcome this resistance, we found that treatment with the receptor tyrosine kinase inhibitor, cediranib, previously reported to suppress expression of downstream HDR factors, resensitizes 53BP1 and REV7-knockout cells to PARPi treatment. Our findings identify key pathways driving PARPi resistance in IDH1-mutant cancers and highlight potential therapeutic strategies to overcome this resistance.