Ara-A, Ara-C, Ara-G, and Ara-T are arabinose sugars combined with adenine, cytosine, guanine, and thymine bases, respectively. These drugs are clinically important as these drugs are commonly used as anti-viral and anti-cancer drugs. Ara-C, an arabinoside, serves as a chain terminator of deoxyribonucleic acid (DNA) replication by interfering with replication after it is incorporated at the 3′ end of nascent DNA, thereby restricting the proliferation of viruses and cancer cells. The incorporated Ara-CMP is efficiently removed by the proofreading exonuclease activity of polymerase epsilon (Polε), in which the alternative clamp loader CTF18 plays a pivotal role. However, the requirement of CTF18 for the removal of the other arabinosides from the 3′ end of nascent DNA remains unclear. Here, we explored DNA repair pathways responsible for the cellular tolerance to Ara-A and found that cells deficient in the proofreading exonuclease activity of Polε (POLE1 exo−/−) showed the highest sensitivity to Ara-A. This activity was also required for cellular tolerance to Ara-G and Ara-T. CTF18 −/− cells showed higher Ara-A sensitivity than wild-type cells, though it was critically lower than that of POLE1 exo−/− cells. Similar trends were observed for the sensitivity to Ara-G and Ara-T. These results indicate that these arabinosides are removed by Polε proofreading exonuclease activity, and CTF18 is pivotal for Polε-mediated Ara-C removal but does not play critical roles for Polε-mediated removal of Ara-A, Ara-G, and Ara-T. In this study, we unveiled a difference between Ara-C and the other arabinosides (Ara-A, Ara-G, and Ara-T) in the removal from the 3′ end of nascent DNA.
Genomic integrity is a fundamental prerequisite for all living organisms, ensuring the accurate transmission of genetic information and stability of cellular functions across generations. The maintenance of genome integrity relies on a meticulously orchestrated network encompassing a variety of DNA repair factors and pathways. In eukaryotic cells, genomic DNA is assembled into chromatin, a highly organized complex of proteins and DNA. Therefore, chromatin and epigenetic factors have emerged as crucial guardians against genotoxic stress. In this review, we provide a comprehensive summary of the multifaceted roles of H3K9me3, a histone mark associated with silent chromatin, in DNA damage repair and genome maintenance, elucidating its dynamic participation in chromatin organization, silencing of repetitive DNA sequences, and modulation of DNA repair pathways. Importantly, we discuss the potential contribution of H3K9me3 to epigenetic memory following DNA damage, which introduces an additional layer of complexity to our comprehension of genomic surveillance. Finally, we explore the implications of H3K9me3 dysregulation in human cancers and the promising therapeutic avenues that may arise from a nuanced understanding of its function in maintaining genomic stability.
The significance of telomere/telomerase biology in the pathogenesis of age-related cardiovascular diseases (CVDs), such as atherosclerosis, hypertension, myocardial infarction (MI), and heart failure, has been increasingly highlighted in recent years. The activation of the DNA damage response (DDR) due to the presence of short telomeres is believed to be a significant upstream signal responsible for inducing a permanent cessation of the cell cycle in cardiomyocytes. Heart failure (HF) is a condition that arises due to the restricted regenerative capacity of the elderly and injured mammalian heart. This limitation may be related to the decreased proliferative potential of cardiac stem cells (CSCs) and cardiomyocytes. The association between CVDs and shorter telomeres provides a foundation for developing therapeutic techniques aimed at elongating telomeres and subsequently restoring the proliferative ability of the adult mammalian heart. This phenomenon offers intriguing prospects for the treatment and prevention of cardiovascular disease (CVD). Further investigation into telomerase gene therapy in the field of cardiac regenerative medicine is justified based on the encouraging outcomes shown in mice models, whereby the reactivation of telomerase in the heart after MI has demonstrated beneficial effects.
Although the importance of histone methylation in epigenetics was first suggested more than 50 years ago, research into histone modifications conducted in the past decade has led to an exponential increase in our understanding of histone H3 modifications. In particular, the involvement of H3 histone 27 lysine trimethylation in the development of various cancer phenotypes has been demonstrated. Unlike mutations in the DNA sequence, such epigenetic changes are reversible, suggesting that inhibitors of H3 histone 27 amino acid methylation enzymes could be used as anti-cancer agents. Here, we outline the regulatory functions of H3 histone 27 lysine trimethylation carried out by different enzymes, in carcinogenesis. We describe the role of H3 histone 27 lysine trimethylation as an important epigenetic regulatory mechanism in the development of various cancers via effects on inflammation, DNA damage repair, cell proliferation, cell metastasis, regulatory cell death, ferroptosis, and angiogenesis. Finally, we focus specifically on H3 histone 27 lysine trimethylation regulators and their future development as anti-cancer drugs.
Posttranslational modifications (PTMs), occurring on various histones and nonhistone proteins, greatly enrich the diversity of the proteome, thereby profoundly affecting protein structures and biological functions. Histones are particularly important components of genomic chromatin and their modifications represent a critical event in the control of DNA damage response (DDR) induced by endogenous or exogenous insults. Extensive studies have revealed the roles of classical PTMs including phosphorylation, acetylation and ubiquitination, in modulating chromatin dynamics through the recruitment of chromatin remodeling complex and repair machinery during DDR process, thus successfully maintaining genome stability and preventing the cells from adverse fates such as apoptosis or malignant transformation. In recent years, several novel PTMs, such as ufmylation, crotonylation, succinylation and lactylation, have been discovered on both histones and nonhistone proteins. Their potential roles and regulatory mechanisms during DDR process have indeed emerged, but are still far from completely understood. This review primarily focuses on the regulation of novel PTMs in DDR, and further discusses the repair networks of cell in response to DNA damage and the interplay between diverse modifications in DNA damage response, which aims to expand the understanding of PTMs involved in DDR regulation and provides potential insights into disease intervention.
Immunotherapy has made remarkable progress within the past decade, but the role of B cells in tumor immunity remains unclear. Here, we show that the combination therapy of anti-PD-1 and TLR9 agonist significantly suppresses the growth of colon and lung tumors in syngeneic mouse models and induces B cell expansion in the tumor-draining lymph nodes and spleen. Using immunological repertoire high-throughput sequencing, we found that combination therapy significantly increased the richness and decreased clonality of B-cell receptors (BCR) with the latter being inversely correlated with the efficacy of tumor inhibition. Moreover, secretory tumor-specific antibodies were increased in combination therapy and elicited Fc-directed tumor lysis function. Employing high-throughput single-cell BCR sequencing technology, we discovered a tumor specific monoclonal antibody (mAb), named 19C5, that had potent anti-tumor activity in vivo. Immunoprecipitation and mass spectrometry analysis revealed that 19C5 mAb specifically recognizes a tumor-associated antigen G protein pathway suppressor 1 (GPS1), whose expression is associated with a worse prognosis in human colon and lung cancer. Taken together, our data highlight the pivotal role of B cells and the production of tumor-reactive antibodies during immunotherapy, suggesting that dynamic changes to the BCR repertoire might serve as a biomarker to predict a clinical response for immunotherapy. We also provide a novel strategy to develop anti-tumor antibodies that may target tumor-associated antigens.
BRCA1 and BRCA2 mutations significantly increase the risk of breast and ovarian cancers (OC) by affecting crucial cellular processes such as cell cycle regulation, DNA repair, and apoptosis. Despite understanding their broad impacts, the detailed effects on gene expression and signaling pathways in OC remain unclear. This study aims to elucidate these dynamics by analyzing RNA-Seq data from 24 OC patients with BRCA1/2 mutations and controls using advanced molecular techniques. Differential expression analysis identified 6136 DEGs in BRCA1-mutant and 3615 DEGs in BRCA2-mutant OCs, with 2041 overlapping DEGs. These shared genes underwent Gene Ontology (GO), KEGG, and Protein–protein interaction (PPI) network analyses, revealing pathways like MyD88-independent TLR signaling and mRNA vaccine activation of dendritic cells. Key genes (TRAF3, TICAM1, IRF7, CD40, IRF3, SARM1, RAB11FIP, and PRKCE) involved in TRIF-dependent TLR signaling showed distinct expression patterns in BRCA1/2-deficient OCs. The top 10 hub genes identified were evaluated for their prognostic significance using the Kaplan–Meier Plotter database. The findings highlight the genetic landscape and pathways altered by BRCA1/2 mutations in OC, offering insights for improved diagnostics and personalized treatments. Additionally, the impact on immunosurveillance through the TRIF-dependent TLR system suggests new immunotherapeutic strategies for OC patients with BRCA1/2 mutations, addressing the challenge of cancer recurrence.
Camptothecin (CPT) is a widely used chemotherapeutic drug that acts by trapping topoisomerase I (TOP1) on DNA during replication. UFMylation is a ubiquitin-like modification involved in various cellular processes, including DNA double-strand break repair. The role of UFMylation in regulating replication-induced DNA damage within cells, however, is unclear. Through in vivo screening, we ascertained that the structure-specific endonuclease MUS81 is UFMylated. MUS81 is responsible for the progression and restarting of replication forks in human cells. We show that CPT triggered the UFMylation of MUS81 at lysine 400, which in turn prevented its ubiquitination-mediated degradation. Additionally, re-expression of WT MUS81, but not UFMylation defective mutant MUS81(K400R), in MUS81-depleted cells rescued CPT-induced cytotoxicity. Thus, the study revealed a new role for UFMylation in CPT-induced DNA damage, in which MUS81 UFMylation at K400 promotes cancer cell survival by inhibiting MUS81 degradation in response to CPT treatment, thus providing an attractive therapeutic strategy combining UFMylation inhibitors with CPT.
Gastric tumors are the third leading cause of cancer-related mortality worldwide. This study investigates the effects of Notch signaling pathway dysregulations during gastric carcinogenesis. Hence, the signatures relevant to Notch signaling pathways were collected from the molecular signatures database, and their expression patterns in available mRNA expression profiles of gastric cancer cohorts were explored using a Z score-based pathway activation scoring method. The results of this study uncover that the Notch signaling pathway signatures are dysregulated highly in diffuse subtype-specific gastric cancer rather than intestinal subtype tumors. In addition, ontological functional analysis reveals that Notch signaling involves extracellular matrix structure and complex organization, collagen structure and trimer biosynthesis during their proliferation, survival, and metastasis. The identified pathway dysregulation is further reconfirmed by examining ROC curves of Notch receptor isoform genes such as NOTCH1, NOTCH2, NOTCH3, and NOTCH4, which could prognostic the diffuse subtype-specific gastric tumors with better specificity and sensitivity with greater areas under the curve (AUC) values. Additionally, overall survival (OS) studies also reassured that these gene expressions reveal poor survival patterns associated with highly expressed conditions in diffuse subtypes of gastric cancer patients with significant p-values (p < 0.05). The results of the genomics drug sensitivity in cancer (GDSC) profile show that ERK and MAPK inhibitors are prominent drug targets for this signaling pathway dysregulations in the corresponding subtype of gastric tumors. Thus, the current findings would benefit the development of drug treatments in diffuse subtype-specific gastric carcinogenesis.
The mechanism governing the stabilization of the replication fork under replication stress is pivotal for maintaining genomic integrity and cellular viability. In this context, the safeguard factors BRCA1/2 and nucleases engage in a regulatory equilibrium, modulating the extent of nascent strand end resection—a process vital for replication fork stabilization under stress and for fork restart upon stress released. The recruitment dynamics of these nucleases, however, remain to be elucidated. Recent two independent studies by
Pyroptosis is a type of programmed lytic cell death mechanism associated with the activation of inflammasomes and inflammatory caspases, proteolytic cleavage of gasdermin proteins (GSDMA-E and PJVK), resulting in the formation of pores in cellular membranes such as plasma membrane and mitochondrial membranes. Here, I show that GSDMC expression was increased, GSDME (DFNA5) and PJVK (DFNB59) expression were decreased in uterine corpus endometrial carcinoma (UCEC) cells compared to normal non-malignant endometrial cells. Total percentage of patients affected by mutations in gasdermin family of genes was the highest in UCEC compared to other cancer types. The highest mutation percentage in UCEC patients among the members of the protein family was observed for GSDME which also showed the most significant difference in the mRNA expression among other family members between tumor and normal samples, possibly pointing to its relatively higher importance in the pathogenesis of UCEC. Gasdermin family of genes (except GSDMA) had higher transcript levels in serous endometrial adenocarcinoma than in endometrioid endometrial adenocarcinoma, demonstrating the histotype-dependent expression of the most of gasdermin family of genes in UCEC. Transcript levels of certain gasdermin family members also differed based on residual tumor status and histologic tumor grade; however, the expression of any gasdermin genes did not change depending on menopause status. This study suggests that a better mechanistic understanding of pyroptotic cell death in uterine corpus endometrial carcinoma might help identify novel therapeutic targets for the management of this gynecological malignancy.
The inhibition of KIF18A selectively reduces the viability of chromosomally unstable cancers due to increased mitotic vulnerability. KIF18A expression was also reported to be upregulated and associated with tumor aggressiveness in certain cancer types including breast cancer. Here, I first showed that KIF18A mRNA expression is higher in triple-negative breast cancer (TNBC) than in non-TNBC. I also found that ER (estrogen receptor)-negative and PR (progesterone receptor)-negative breast cancer cells have higher KIF18A mRNA expression compared to ER-positive and PR-positive breast cancer cells, respectively. In contrast, HER2-positive breast tumors have higher KIF18A expression compared to HER2-negative breast tumors. In terms of PAM50 breast cancer subtypes, KIF18A transcript levels were found to be the highest in basal-like breast cancer, followed by HER2-enriched, luminal B, normal-like and luminal A. Besides, in non-TNBC, cells with high AR (androgen receptor) mRNA expression have higher KIF18A mRNA expression than cells with low AR mRNA expression. Both non-TNBC and TNBC cells with high BRCA1 and BRCA2 mRNA expression levels were observed to have higher KIF18A mRNA expression than those with low BRCA1 and BRCA2 mRNA expression levels, respectively. Combined, this study demonstrates that breast tumors with low and high expression of ER, PR, HER2, AR and BRCA1/2 have differential transcript levels of KIF18A, pointing that KIF18A might contribute to the molecular differences between different breast cancer subtypes.
Death-associated protein 3 (DAP3) is a highly conserved guanosine triphosphate (GTP) binding protein. As a component of the mitochondrial ribosome 28 S small subunit, DAP3 is involved in apoptosis pathways and plays a vital role in mitochondrial dynamics, mitochondrial protein synthesis, anoikis, and autophagy. Recently, DAP3 has been reported to participate in the development and progression of various cancers. In this review, we provide a brief overview of recent findings regarding the structure, subcellular localization, and function of DAP3 as well as its role in cancer development and progression.