Roles of Chk1 in cell biology and cancer therapy

Novel imidazolone derivatives as potential dual inhibitors of checkpoint kinases 1 and 2: Design, synthesis, cytotoxicity evaluation, and mechanistic insights

Applying various drug design strategies including ring variation, substituents variation, and ring fusion, two series of 2-(alkylthio)-5-(arylidene/heteroarylidene)imidazolones and imidazo[1,2-a]thieno[2,3-d]pyrimidines were designed and prepared as dual potential Chk1 and Chk2 inhibitors. The newly synthesized hybrids were screened in NCI 60 cell line panel where the most active derivatives 4b, d-f, and 6a were further estimated for their five dose antiproliferative activity against the most sensitive tumor cells including breast MCF-7 and MDA-MB-468 and non-small cell lung cancer EKVX as well as normal WI-38 cell. Noticeably, increasing the carbon chain attached to thiol moiety at C-2 of imidazolone scaffold elevated the cytotoxic activity. Hence, compounds 4e and 4f, containing S-butyl fragment, exhibited the most antiproliferative activity against the tested cells where 4f showed extremely potent selectivity toward them. As well, compound 6a, containing imidazothienopyrimidine core, exerted significant cytotoxic activity and selectivity toward the examined cells. The mechanistic investigation of the most active cytotoxic analogs was achieved through the evaluation of their inhibitory activity against Chk1 and Chk2. Results revealed that 4f displayed potent dual inhibition of both Chk1 and Chk2 with IC50 equal 0.137 and 0.25 μM, respectively. It also promoted its antiproliferative and Chk suppression activity via EKVX cell cycle arrest at S phase through stimulating the apoptotic approach. The apoptosis induction was also emphasized by elevating the expression of Caspase-3 and Bax, that are accompanied by Bcl-2 diminution. The in silico molecular docking and ADMET profiles of the most active analogs have been carried out to evaluate their potential as significant anticancer drug candidates.

Apelin-13 improves pulmonary epithelial barrier function in a mouse model of LPS-induced acute lung injury by inhibiting Chk1-mediated DNA damage

Apelin-13, a type of active peptide, can alleviate lipopolysaccharide (LPS)-induced acute lung injury (ALI). However, the specific mechanism is unclear. Cell cycle checkpoint kinase 1 (Chk1) plays an important role in DNA damage. Here, we investigated the regulatory effect of Apelin on Chk1 in ALI. Chk1-knockout and -overexpression mice were used to explore the role of Chk1 in LPS-induced ALI mice treated with or without Apelin-13. In addition, A549 cells were also treated with LPS to establish a cell model. Chk1 knockdown inhibited the destruction of alveolar structure, the damage of lung epithelial barrier function, and DNA damage in the ALI mouse model. Conversely, Chk1 overexpression had the opposite effect. Furthermore, Apelin-13 reduced Chk1 expression and DNA damage to improve the impaired lung epithelial barrier function in the ALI model. However, the high expression of Chk1 attenuated the protective effect of Apelin-13 on ALI. Notably, Apelin-13 promoted Chk1 degradation through autophagy to regulate DNA damage in LPS-treated A549 cells. In summary, Apelin-13 regulates the expression of Chk1 by promoting autophagy, thereby inhibiting epithelial DNA damage and repairing epithelial barrier function.

Case report: A germline CHEK1 c.613 + 2T>C leads to a splicing error in a family with multiple cancer patients

Background

Genome instability plays a crucial role in promoting tumor development. Germline mutations in genes responsible for DNA repair are often associated with familial cancer syndromes. A noticeable exception is the CHEK1 gene. Despite its well-established role in homologous recombination, germline mutations in CHEK1 are rarely reported.

Case presentation

In this report, we present a patient diagnosed with ovarian clear cell carcinoma who has a family history of cancer. Her relatives include a grandfather with esophageal cancer, a father with gastric cancer, and an uncle with a brain tumor. The patient carried a typical genomic profile of clear cell carcinoma including mutations in KRAS, PPP2R1A, and PIK3R1. Importantly, her paired peripheral blood cells harbored a germline CHEK1 mutation, CHEK1 exon 6 c.613 + 2T>C, which was also found in her father. Unfortunately, the CHEK1 status of her grandfather and uncle remains unknown due to the unavailability of their specimens. Further evaluation via RT-PCR confirmed a splicing error in the CHEK1 gene, resulting in truncation at the kinase domain region, indicative of a loss-of-function mutation.

Conclusion

This case highlights a rare germline CHEK1 mutation within a family with a history of cancer. The confirmed splicing error at the mRNA level underscores the functional consequences of this mutation. Documenting such cases is vital for future evaluation of inheritance patterns, clinical penetrance of the mutation, and its association with specific cancer types.

Antitumoral Activity of the Universal Methyl Donor S-Adenosylmethionine in Glioblastoma Cells

Glioblastoma (GBM), the most frequent and lethal brain cancer in adults, is characterized by short survival times and high mortality rates. Due to the resistance of GBM cells to conventional therapeutic treatments, scientific interest is focusing on the search for alternative and efficient adjuvant treatments. S-Adenosylmethionine (AdoMet), the well-studied physiological methyl donor, has emerged as a promising anticancer compound and a modulator of multiple cancer-related signaling pathways. We report here for the first time that AdoMet selectively inhibited the viability and proliferation of U87MG, U343MG, and U251MG GBM cells. In these cell lines, AdoMet induced S and G2/M cell cycle arrest and apoptosis and downregulated the expression and activation of proteins involved in homologous recombination DNA repair, including RAD51, BRCA1, and Chk1. Furthermore, AdoMet was able to maintain DNA in a damaged state, as indicated by the increased γH2AX/H2AX ratio. AdoMet promoted mitotic catastrophe through inhibiting Aurora B kinase expression, phosphorylation, and localization causing GBM cells to undergo mitotic catastrophe-induced death. Finally, AdoMet inhibited DNA repair and induced cell cycle arrest, apoptosis, and mitotic catastrophe in patient-derived GBM cells. In light of these results, AdoMet could be considered a potential adjuvant in GBM therapy.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

Uncovering Cell Cycle Dysregulations and Associated Mechanisms in Cancer and Neurodegenerative Disorders: A Glimpse of Hope for Repurposed Drugs

The cell cycle is the sequence of events orchestrated by a complex network of cell cycle proteins. Unlike normal cells, mature neurons subsist in a quiescent state of the cell cycle, and aberrant cell cycle activation triggers neuronal death accompanied by neurodegeneration. The periodicity of cell cycle events is choreographed by various mechanisms, including DNA damage repair, oxidative stress, neurotrophin activity, and ubiquitin-mediated degradation. Given the relevance of cell cycle processes in cancer and neurodegeneration, this review delineates the overlapping cell cycle events, signaling pathways, and mechanisms associated with cell cycle aberrations in cancer and the major neurodegenerative disorders. We suggest that dysregulation of some common fundamental signaling processes triggers anomalous cell cycle activation in cancer cells and neurons. We discussed the possible use of cell cycle inhibitors for neurodegenerative disorders and described the associated challenges. We propose that a greater understanding of the common mechanisms driving cell cycle aberrations in cancer and neurodegenerative disorders will open a new avenue for the development of repurposed drugs.

Promises of Protein Kinase Inhibitors in Recalcitrant Small-Cell Lung Cancer: Recent Scenario and Future Possibilities

SCLC is refractory to conventional therapies; targeted therapies and immunological checkpoint inhibitor (ICI) molecules have prolonged survival only marginally. In addition, ICIs help only a subgroup of SCLC patients. Different types of kinases play pivotal roles in therapeutics-driven cellular functions. Therefore, there is a significant need to understand the roles of kinases in regulating therapeutic responses, acknowledge the existing knowledge gaps, and discuss future directions for improved therapeutics for recalcitrant SCLC. Here, we extensively review the effect of dysregulated kinases in SCLC. We further discuss the pharmacological inhibitors of kinases used in targeted therapies for recalcitrant SCLC. We also describe the role of kinases in the ICI-mediated activation of antitumor immune responses. Finally, we summarize the clinical trials evaluating the potential of kinase inhibitors and ICIs. This review overviews dysregulated kinases in SCLC and summarizes their potential as targeted therapeutic agents. We also discuss their clinical efficacy in enhancing anticancer responses mediated by ICIs.

New molecular mechanisms to explain the neuroprotective effects of insulin-like growth factor II in a cellular model of Parkinson's disease

INTRODUCTION

One of the hallmarks of Parkinsońs Disease (PD) is oxidative distress, leading to mitochondrial dysfunction and neurodegeneration. Insulin-like growth factor II (IGF-II) has been proven to have antioxidant and neuroprotective effects in some neurodegenerative diseases, including PD. Consequently, there isgrowing interest in understanding the different mechanisms involved in the neuroprotective effect of this hormone.

OBJECTIVES

To clarify the mechanism of action of IGF-II involved in the protective effect of this hormone.

METHODS

The present study was carried out on a cellular model PD based on the incubation of dopaminergic cells (SN4741) in a culture with the toxic 1-methyl-4-phenylpyridinium (MPP+), in the presence of IGF-II. This model undertakes proteomic analyses in order to understand which molecular cell pathways might be involved in the neuroprotective effect of IGF-II. The most important proteins found in the proteomic study were tested by Western blot, colorimetric enzymatic activity assay and immunocytochemistry. Along with the proteomic study, mitochondrial morphology and function were also studied by transmission electron microscopy and oxygen consumption rate. The cell cycle was also analysed using 7AAd/BrdU staining, and flow cytometry.

RESULTS

The results obtained indicate that MPP+, MPP++IGF-II treatment and IGF-II, when compared to control, modified the expression of 197, 246 proteins and 207 respectively. Some of these proteins were found to be involved in mitochondrial structure and function, and cell cycle regulation. Including IGF-II in the incubation medium prevents the cell damage induced by MPP+, recovering mitochondrial function and cell cycle dysregulation, and thereby decreasing apoptosis.

CONCLUSION

IGF-II improves mitochondrial dynamics by promoting the association of Mitofilin with mitochondria, regaining function and redox homeostasis. It also rebalances the cell cycle, reducing the amount of apoptosis and cell death by the regulation of transcription factors, such as Checkpoint kinase 1.

Key Proteins of Replication Stress Response and Cell Cycle Control as Cancer Therapy Targets

Replication stress (RS) is a characteristic state of cancer cells as they tend to exchange precision of replication for fast proliferation and increased genomic instability. To overcome the consequences of improper replication control, malignant cells frequently inactivate parts of their DNA damage response (DDR) pathways (the ATM-CHK2-p53 pathway), while relying on other pathways which help to maintain replication fork stability (ATR-CHK1). This creates a dependency on the remaining DDR pathways, vulnerability to further destabilization of replication and synthetic lethality of DDR inhibitors with common oncogenic alterations such as mutations of TP53, RB1, ATM, amplifications of MYC, CCNE1 and others. The response to RS is normally limited by coordination of cell cycle, transcription and replication. Inhibition of WEE1 and PKMYT1 kinases, which prevent unscheduled mitosis entry, leads to fragility of under-replicated sites. Recent evidence also shows that inhibition of Cyclin-dependent kinases (CDKs), such as CDK4/6, CDK2, CDK8/19 and CDK12/13 can contribute to RS through disruption of DNA repair and replication control. Here, we review the main causes of RS in cancers as well as main therapeutic targets-ATR, CHK1, PARP and their inhibitors.

Lysine demethylase 5B (KDM5B): A key regulator of cancer drug resistance

Chemoresistance, a roadblock in the chemotherapy process, has been impeding its effective treatment. KDM5B, a member of the histone demethylase family, has been crucial in the emergence and growth of malignancies. More significantly, KDM5B has recently been linked closely to cancer's resistance to chemotherapy. In this review, we explain the biological properties of KDM5B, its function in the emergence and evolution of cancer treatment resistance, and our hopes for future drug resistance-busting combinations involving KDM5B and related targets or medications.

CRISPR-based therapeutic targeting of signaling pathways in breast cancer

Breast cancer remains a leading cause of death for women worldwide, and new treatment strategies are needed. There are innumerable anomalous genes that are responsible for the multi-factorial carcinogenesis pathway. Although several disease-causing mutations have been detected, therapy frequently focuses on attenuating the manifestation of the disease rather than harmonizing the mutation in the target area. The advent of CRISPR-Cas9 technology has revolutionized genome editing, allowing for precise and efficient manipulation of gene expression. The purpose of this review paper is to summarize recent progress in the use of CRISPR-based approaches to target key signaling pathways associated with breast cancer progression. The first section introduces basic concepts of CRISPR technology, focusing on its application in genome editing and transcriptional regulation followed by an overview of aspects involving complex signaling pathways in breast cancer such as P13K/AKT/mTOR, EPK/MAPK and Wnt/β catenin. An extensive literature search using PubMed and Google Scholar is performed for information retrieval. Further, the role of CRISPR-based interventions in regulating gene expression revealed, altered pathway activity and potential therapeutic consequences are discussed. This review will be a valuable addition to providing comprehensive knowledge of CRISPR-Cas-mediated therapeutic targeting in breast cancer.

Cisplatin and Procaterol Combination in Gastric Cancer? Targeting Checkpoint Kinase 1 for Cancer Drug Discovery and Repurposing by an Integrated Computational and Experimental Approach

Checkpoint kinase 1 (CHK1), a serine/threonine kinase, plays a crucial role in cell cycle arrest and is a promising therapeutic target for drug development against cancers. CHK1 coordinates cell cycle checkpoints in response to DNA damage, facilitating repair of single-strand breaks, and maintains the genome integrity in response to replication stress. In this study, we employed an integrated computational and experimental approach to drug discovery and repurposing, aiming to identify a potent CHK1 inhibitor among existing drugs. An e-pharmacophore model was developed based on the three-dimensional crystal structure of the CHK1 protein in complex with CCT245737. This model, characterized by seven key molecular features, guided the screening of a library of drugs through molecular docking. The top 10% of scored ligands were further examined, with procaterol emerging as the leading candidate. Procaterol demonstrated interaction patterns with the CHK1 active site similar to CHK1 inhibitor (CCT245737), as shown by molecular dynamics analysis. Subsequent in vitro assays, including cell proliferation, colony formation, and cell cycle analysis, were conducted on gastric adenocarcinoma cells treated with procaterol, both as a monotherapy and in combination with cisplatin. Procaterol, in synergy with cisplatin, significantly inhibited cell growth, suggesting a potentiated therapeutic effect. Thus, we propose the combined application of cisplatin and procaterol as a novel potential therapeutic strategy against human gastric cancer. The findings also highlight the relevance of CHK1 kinase as a drug target for enhancing the sensitivity of cytotoxic agents in cancer.

Identification of formononetin as the active compound of CR-SR in hepatocellular carcinoma treatment: An integrated approach combining network pharmacology and weighted gene co-expression networks

Hepatocellular carcinoma (HCC) is a life-threatening disease for which there is no cure. Traditional Chinese medicine is a treasure trove of Medicinals that has been used for thousands of years. In China, the traditional herb pair, Curcumae Rhizoma and Sparganii Rhizoma (CR-SR) represent a classic herbal combination used for the treatment of HCC. However, the drug targets and pharmacological mechanism of action of CR-SR in the treatment of HCC are unclear. To address this, we screened the active components and drug targets of CR-SR from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database and a high-throughput experiment- and reference-guided database of traditional Chinese medicines (HERB database). Combined with the weighted co-expression network analysis of dataset GSE76427, we constructed an active component-target-disease regulatory network. It was found that CR-SR's active components for HCC treatment included trans-gondoic acid, beta-sitosterol, stigmasterol, hederagenin, and formononetin. These compounds specifically targeted the genes Estrogen Receptor 1 (ESR1), Cyclin A2 (CCNA2), Checkpoint Kinase 1 (CHEK1), and Nuclear Receptor Coactivator 2 (NCOA2). ESR1, CCNA2, and CHEK1 genes showed significant differences in survival prognosis, expression levels, and statistical significance during the pathological stage. Moreover, their high affinity for formononetin was determined through molecular docking analysis. Cell assays and high-throughput sequencing were performed to reveal that the inhibitory effect of formononetin on HepG2 cell proliferation was related to hepatocyte metabolism and cell cycle regulation-related pathways. This study provides insights into potential HCC treatments.

In silico and structure-based evaluation of deleterious mutations identified in human Chk1, Chk2, and Wee1 protein kinase

Checkpoint kinases Chk1, Chk2, Wee1 are playing a key role in DNA damage response and genomic integrity. Cancer-associated mutations identified in human Chk1, Chk2, and Wee1 were retrieved to understand the function associated with the mutation and also alterations in the folding pattern. Therefore, an attempt has been made to identify deleterious effect of variants using in silico and structure-based approach. Variants of uncertain significance for Chk1, Chk2, and Wee1 were retrieved from different databases and four prediction servers were employed to predict pathogenicity of mutations. Further, Interpro, I-Mutant 3.0, Consurf, TM-align, and have (y)our protein explained were used for comprehensive study of the deleterious effects of variants. The sequences of Chk1, Chk2, and Wee1 were analyzed using Clustal Omega, and the three-dimensional structures of the proteins were aligned using TM-align. The molecular dynamics simulations were performed to explore the differences in folding pattern between Chk1, Chk2, Wee1 wild-type, and mutant protein and also to evaluate the structural integrity. Thirty-six variants in Chk1, 250 Variants in Chk2, and 29 in Wee1 were categorized as pathogenic using in silico prediction tools. Furthermore, 25 mutations in Chk1, 189 in Chk2, and 14 in Wee1 were highly conserved, possessing deleterious effect and also influencing the protein structure and function. These identified mutations may provide underlying genetic intricacies to serve as potential targets for therapeutic inventions and clinical management.

Design and synthesis of certain 7-Aryl-2-Methyl-3-Substituted Pyrazolo{1,5-a}Pyrimidines as multikinase inhibitors

Four new series 7a-e, 8a-e, 9a-e, and 10a-e of 7-aryl-3-substituted pyrazolo[1,5-a]pyrimidines were synthesized and tested for their RTK and STK inhibitory activity. Compound 7d demonstrated potent enzymatic inhibitory activity against TrkA and ALK2 with IC50 0.087and 0.105 μM, respectively, and potent antiproliferative activity against KM12 and EKVX cell lines with IC50 0.82 and 4.13 μM, respectively. Compound 10e showed good enzyme inhibitory activity against TrkA, ALK2, c-KIT, EGFR, PIM1, CK2α, CHK1, and CDK2 in submicromolar values. Additionally 10e revealed antiproliferative activity against MCF7, HCT116 and EKVX with IC50 3.36, 1.40 and 3.49 μM, respectively; with good safety profile. Moreover, 10e showed cell cycle arrest at the G1/S phase and G1 phase in MCF7 and HCT116 cells with good apoptotic effect. Molecular docking studies were fulfilled for compound 10e and illustrated good interaction with the hot spots of the active site of the tested enzymes.

Small-Molecule Probes as Pharmacological Tools for the Bone Morphogenetic Protein Signaling Pathway

The bone morphogenetic protein (BMP) pathway is highly conserved and plays central roles in health and disease. The quality and quantity of its signaling outputs are regulated at multiple levels, offering pharmacological options for targeted modulation. Both target-centric and phenotypic drug discovery (PDD) approaches were applied to identify small-molecule BMP inhibitors and stimulators. In this Review, we accumulated and systematically classified the different reported chemotypes based on their targets as well as modes-of-action, and herein we illustrate the discovery history of selected candidates. A comprehensive summary of available biochemical, cellular, and in vivo activities is provided for the most relevant BMP modulators, along with recommendations on their preferred use as chemical probes to study BMP-related (patho)physiological processes. There are a number of high-quality probes used as BMP inhibitors that potently and selectively interrogate the kinase activities of distinct type I (16 chemotypes available) and type II receptors (3 chemotypes available). In contrast, only a few high-quality BMP stimulator modalities have been introduced to the field due to a lack of profound target knowledge. FK506-derived macrolides such as calcineurin-sparing FKBP12 inhibitors currently represent the best-characterized chemical tools for direct activation of BMP-SMAD signaling at the receptor level. However, several PDD campaigns succeeded in expanding the druggable space of BMP stimulators. Albeit the majority of them do not entirely fulfill the strict chemical probe criteria, many chemotypes exhibit unique and unrecognized mechanisms as pathway potentiators or synergizers, serving as valuable pharmacological tools for BMP perturbation.

NH4I-promoted electrosynthesis of 2-aminothiazole derivatives from ketone compounds and NH4SCN

A novel and efficient electrochemical synthesis of 2-aminothiazole derivatives from ketones and NH4SCN is described. Under the co-action of NH3 and iodine free radicals or iodine (I2) electrochemically generated in situ, the target product 2-aminothiazole derivatives could be successfully obtained in good to excellent yields.

Identification of naturally occurring compounds as alternatives to radiation therapy for treatment of small cell lung cancer

Radiation resistance is one of the major problems in the treatment of small cell lung cancer (SCLC). Most of these patients are given radiation as first-line treatment and it was observed that the initial response in these patients is very good. However, they show relapse in a few months which is also associated with resistance to treatment. Thus, targeting the mechanism by which these cells develop resistance could be an important strategy to improve the survival chances of these patients. From the RNA-Seq data analysis, it was identified that CHEK1 gene was overexpressed. Chk1 protein which is encoded by the CHEK1 gene is an important protein that is involved in radiation resistance in SCLC. It is known to favour the cells to deal with replicative stress. CHEK1 is the major cause for developing radiation resistance in SCLC. Thus, natural compounds that could also serve as potential inhibitors for Chk1 were explored. Accordingly; the compounds were screened based on ADME, docking and MM-GBSA scores. MD simulations were performed for the selected protein-ligand complexes and the results were compared to the co-crystallised ligand, 3-(indol-2-yl)indazole. The results showed that compound INC000033832986 could be a natural alternative to the commercial ligand for the prevention of SCLC.Communicated by Ramaswamy H. Sarma.

New horizons in lung cancer management through ATR/CHK1 pathway modulation

Lung cancer is the leading cause of cancer-related deaths worldwide. Molecular profiling has contributed to a new classification of lung cancer, driving advancements in research and therapy. The ataxia telangiectasia and rad3/checkpoint kinase 1 (ATR/CHK1) pathway plays a crucial role in maintaining genomic stability, and its activation has been linked to the development of lung cancer, drug resistance and poor prognosis. Clinical and preclinical studies have demonstrated promising results in targeting this pathway. ATR and CHK1 are proteins that collaborate to repair DNA damage caused by radiation or chemotherapy. ATR/CHK1 inhibitors are currently under investigation in preclinical and clinical trials. This article explores the ATR/CHK1 pathway and its potential for treating lung cancer.

Potent molecular-targeted therapies for gastro-entero-pancreatic neuroendocrine carcinoma

Neuroendocrine neoplasms (NENs), which are characterized by neuroendocrine differentiation, can arise in various organs. NENs have been divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on morphological differentiation, each of which has a distinct etiology, molecular profile, and clinicopathological features. While the majority of NECs originate in the pulmonary organs, extrapulmonary NECs occur most predominantly in the gastro-entero-pancreatic (GEP) system. Although platinum-based chemotherapy is the main therapeutic option for recurrent or metastatic GEP-NEC patients, the clinical benefits are limited and associated with a poor prognosis, indicating the clinically urgent need for effective therapeutic agents. The clinical development of molecular-targeted therapies has been hampered due to the rarity of GEP-NECs and the paucity of knowledge on their biology. In this review, we summarize the biology, current treatments, and molecular profiles of GEP-NECs based on the findings of pivotal comprehensive molecular analyses; we also highlight potent therapeutic targets for future precision medicine based on the most recent results of clinical trials.

BRD7 suppresses tumor chemosensitivity to CHK1 inhibitors by inhibiting USP1-mediated deubiquitination of CHK1

Checkpoint kinase 1 (CHK1), a key effector in the cellular response to DNA lesions, is a crucial component of all cell cycle checkpoints. Recent reports have revealed that CHK1 is highly expressed in numerous cancer types in the clinical settings. However, the mechanisms underlying the regulation of CHK1 expression in tumor cells remain unclear. Here, we report that CHK1 is negatively regulated by the bromodomain-containing protein 7 (BRD7). Specifically, BRD7 silencing increased CHK1 (but not CHK2) expression at both mRNA and protein levels, in a p53-independent manner in multiple tumor cell lines. Furthermore, BRD7 silencing stabilized CHK1 via reducing its ubiquitination. Mechanistically, BRD7 knockdown not only increased the levels of USP1, a deubiquitinase for CHK1, but also promoted the interaction between CHK1 and USP1, subsequently enhancing the de-ubiquitination of CHK1. USP1 knockdown abrogated BRD7 silencing-induced CHK1 induction. Biologically, the increased expression of CHK1 in tumor cells caused by BRD7 silencing significantly increased cell sensitivity to CHK1 inhibitors by enhancing tumor cell apoptosis, and this effect was reversed by the simultaneous knockdown of CHK1 or USP1. Taken together, our findings suggest that BRD7 is a potential genetic or drug target that may help to improve the efficacy of chemotherapeutic drugs targeting CHK1 in combinatorial therapy.

Cleavage and Polyadenylation-Specific Factor 4 (CPSF4) Expression Is Associated with Enhanced Prostate Cancer Cell Migration and Cell Cycle Dysregulation, In Vitro

Potential oncogene cleavage and polyadenylation specific factor 4 (CPSF4) has been linked to several cancer types. However, little research has been conducted on its function in prostate cancer (PCa). In benign, incidental, advanced, and castrate resistant PCa (CRPCa) patient samples, protein expression of CPSF4 was examined on tissue microarray (TMAs) of 353 PCa patients using immunohistochemistry. Using the 'The Cancer Genome Atlas' Prostate Adenocarcinoma (TCGA PRAD) database, significant correlations were found between high CPSF4 expression and high-risk genomic abnormalities such as ERG-fusion, ETV1-fusion, and SPOP mutations. Gene Set Enrichment Analysis (GSEA) of CPSF4 revealed evidence for the increase in biological processes such as cellular proliferation and metastasis. We further examined the function of CPSF4 in vitro and confirmed CPSF4 clinical outcomes and its underlying mechanism. Our findings showed a substantial correlation between Gleason groups and CPSF4 protein expression. In vitro, CPSF4 knockdown reduced cell invasion and migration while also causing G1 and G2 arrest in PC3 cell lines. Our findings demonstrate that CPSF4 may be used as a possible biomarker in PCa and support its oncogenic function in cellular proliferation and metastasis.

Studying the DNA damage response pathway in hematopoietic canine cancer cell lines, a necessary step for finding targets to generate new therapies to treat cancer in dogs

Background

Dogs present a significant opportunity for studies in comparative oncology. However, the study of cancer biology phenomena in canine cells is currently limited by restricted availability of validated antibody reagents and techniques. Here, we provide an initial characterization of the expression and activity of key components of the DNA Damage Response (DDR) in a panel of hematopoietic canine cancer cell lines, with the use of commercially available antibody reagents.

Materials and methods

The techniques used for this validation analysis were western blot, qPCR, and DNA combing assay.

Results

Substantial variations in both the basal expression (ATR, Claspin, Chk1, and Rad51) and agonist-induced activation (p-Chk1) of DDR components were observed in canine cancer cell lines. The expression was stronger in the CLBL-1 (B-cell lymphoma) and CLB70 (B-cell chronic lymphocytic leukemia) cell lines than in the GL-1 (B-cell leukemia) cell line, but the biological significance of these differences requires further investigation. We also validated methodologies for quantifying DNA replication dynamics in hematopoietic canine cancer cell lines, and found that the GL-1 cell line presented a higher replication fork speed than the CLBL-1 cell line, but that both showed a tendency to replication fork asymmetry.

Conclusion

These findings will inform future studies on cancer biology, which will facilitate progress in developing novel anticancer therapies for canine patients. They can also provide new knowledge in human oncology.

Small Cell Lung Cancer: Emerging Targets and Strategies for Precision Therapy

Small cell lung cancer is an aggressive subtype of lung cancer with limited treatment options. Precision medicine has revolutionized cancer treatment for many tumor types but progress in SCLC has been slower due to the lack of targetable biomarkers. This review article provides an overview of emerging strategies for precision therapy in SCLC. Targeted therapies include targeted kinase inhibitors, monoclonal antibodies, angiogenesis inhibitors, antibody-drug conjugates, PARP inhibitors, and epigenetic modulators. Angiogenesis inhibitors and DNA-damaging agents, such as PARP and ATR inhibitors, have been explored in SCLC with limited success to date although trials are ongoing. The potential of targeting DLL3, a NOTCH ligand, through antibody-drug conjugates, bispecific T-cell engagers, and CAR T-cell therapy, has opened up new therapeutic options moving forward. Additionally, new research in epigenetic therapeutics in reversing transcriptional repression, modulating anti-tumor immunity, and utilizing antibody-drug conjugates to target cell surface-specific targets in SCLC are also being investigated. While progress in precision therapy for SCLC has been challenging, recent advancements provide optimism for improved treatment outcomes. However, several challenges remain and will need to be addressed, including drug resistance and tumor heterogeneity. Further research and biomarker-selected clinical trials are necessary to develop effective precision therapies for SCLC patients.

Photodynamic therapy induced cell cycle arrest and cancer cell synchronization: review

Cell cycle arrest (CCA) is seen as a prime candidate for effective cancer therapy. This mechanism can help researchers to create new treatments to target cancer cells at particular stages of the cell cycle (CC). The CCA is a characteristic of various therapeutic modalities, including radiation (RT) and chemotherapy (CT), which synchronizes the cells and facilitates the standardization of radio-chemotherapy protocols. Although it was discovered that photodynamic treatment (PDT) had a biological effect on CCA in cancer cells, the mechanism remains unclear. Furthermore, besides conventional forms of cell death such as apoptosis, autophagy, and necrosis, various unconventional types of cell death including pyroptosis, mitotic catastrophe, paraptosis, ferroptosis, necroptosis, and parthanatos after PDT have been reported. Thus, a variety of elements, such as oxygen, the tumor's microenvironment, the characteristics of light, and photosensitizer (PS), influence the effectiveness of the PDT treatment, which have not yet been studied clearly. This review focuses on CCA induced by PDT for a variety of PSs agents on various cell lines. The CCA by PDT can be viewed as a remarkable effect and instructive for the management of the PDT protocol. Regarding the relationship between the quantity of reactive oxygen species (ROS) and its biological consequences, we have proposed two mathematical models in PDT. Finally, we have gathered recent in vitro and in vivo studies about CCA post-PDT at various stages and made suggestions about how it can standardize, potentiate, and customize the PDT methodology.

Impact of DNA damage repair alterations on prostate cancer progression and metastasis

Prostate cancer is among the most common diseases worldwide. Despite recent progress with treatments, patients with advanced prostate cancer have poor outcomes and there is a high unmet need in this population. Understanding molecular determinants underlying prostate cancer and the aggressive phenotype of disease can help with design of better clinical trials and improve treatments for these patients. One of the pathways often altered in advanced prostate cancer is DNA damage response (DDR), including alterations in BRCA1/2 and other homologous recombination repair (HRR) genes. Alterations in the DDR pathway are particularly prevalent in metastatic prostate cancer. In this review, we summarise the prevalence of DDR alterations in primary and advanced prostate cancer and discuss the impact of alterations in the DDR pathway on aggressive disease phenotype, prognosis and the association of germline pathogenic alterations in DDR genes with risk of developing prostate cancer.

SCML2 contributes to tumor cell resistance to DNA damage through regulating p53 and CHK1 stability

SCML2 has been found to be highly expressed in various tumors. However, the extent to which SCML2 is involved in tumorigenesis and cancer therapy is yet to be fully understood. In this study, we aimed to investigate the relationship between SCML2 and DNA damage response (DDR). Firstly, DNA damage stabilizes SCML2 through CHK1-mediated phosphorylation at Ser570. Functionally, this increased stability of SCML2 enhances resistance to DNA damage agents in p53-positive, p53-mutant, and p53-negative cells. Notably, SCML2 promotes chemoresistance through distinct mechanisms in p53-positive and p53-negative cancer cells. SCML2 binds to the TRAF domain of USP7, and Ser441 is a critical residue for their interaction. In p53-positive cancer cells, SCML2 competes with p53 for USP7 binding and destabilizes p53, which prevents DNA damage-induced p53 overactivation and increases chemoresistance. In p53-mutant or p53-negative cancer cells, SCML2 promotes CHK1 and p21 stability by inhibiting their ubiquitination, thereby enhancing the resistance to DNA damage agents. Interestingly, we found that SCML2A primarily stabilizes CHK1, while SCML2B regulates the stability of p21. Therefore, we have identified SCML2 as a novel regulator of chemotherapy resistance and uncovered a positive feedback loop between SCML2 and CHK1 after DNA damage, which serves to promote the chemoresistance to DNA damage agents.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

The evolving role of DNA damage response in overcoming therapeutic resistance in ovarian cancer

Epithelial ovarian cancer (EOC) is treated in the first-line setting with combined platinum and taxane chemotherapy, often followed by a maintenance poly (ADP-ribose) polymerase inhibitor (PARPi). Responses to first-line treatment are frequent. For many patients, however, responses are suboptimal or short-lived. Over the last several years, multiple new classes of agents targeting DNA damage response (DDR) mechanisms have advanced through clinical development. In this review, we explore the preclinical rationale for the use of ATR inhibitors, CHK1 inhibitors, and WEE1 inhibitors, emphasizing their application to chemotherapy-resistant and PARPi-resistant ovarian cancer. We also present an overview of the clinical development of the leading drugs in each of these classes, emphasizing the rationale for monotherapy and combination therapy approaches.

ATF2 loss promotes 5-FU resistance in colon cancer cells via activation of the ATR-Chk1 damage response pathway

BACKGROUND

The role of ATF2 in colon cancer (CC) is controversial. Recently, we reported that low ATF2 expression is characteristic of highly invasive tumors, suggesting that ATF2 might also be involved in therapy resistance. 5-Fluorouracil (5-FU) is the best-known chemotherapeutic drug for CC, but drug resistance affects its curative effect. To date, the role of ATF2 in the 5-FU response remains elusive.

METHODS/RESULTS

For our study, we had available HCT116 cells (wild-type p53) and HT29 colon tumor cells (mutant p53) and their corresponding CRISPR‒Cas9-generated ATF2-KO clones. We observed that loss of ATF2 triggered dose- and time-dependent 5-FU resistance in HCT116 cells by activating the DNA damage response (DDR) pathway with high p-ATR^Thr1989 and p-Chk1^Ser317 levels accompanied by an increase in the DNA damage marker γ-H2AX in vitro and in vivo using the chicken chorioallantoic membrane (CAM) model. Chk1 inhibitor studies causally displayed the link between DDR and drug resistance. There were contradictory findings in HT29 ATF2-KO cells upon 5-FU exposure with low p-Chk1^Ser317 levels, strong apoptosis induction, but no effects on DNA damage. In ATF2-silenced HCT116 p53^-/- cells, 5-FU did not activate the DDR pathway. Co-immunoprecipitation and proximity ligation assays revealed that upon 5-FU treatment, ATF2 binds to ATR to prevent Chk1 phosphorylation. Indeed, in silico modelling showed reduced ATR-Chk1 binding when ATF2 was docked into the complex.

CONCLUSIONS

We demonstrated a novel ATF2 scaffold function involved in the DDR pathway. ATF2-negative cells are highly resistant due to effective ATR/Chk1 DNA damage repair. Mutant p53 seems to overwrite the tumor suppressor function of ATF2.

p130RB2 positively contributes to ATR activation in response to replication stress via the RPA32-ETAA1 axis

Ataxia-telangiectasia mutated and Rad3-related (ATR) kinase is a crucial regulator of the cell cycle checkpoint and activated in response to DNA replication stress by two independent pathways via RPA32-ETAA1 and TopBP1. However, the precise activation mechanism of ATR by the RPA32-ETAA1 pathway remains unclear. Here, we show that p130RB2, a member of the retinoblastoma protein family, participates in the pathway under hydroxyurea-induced DNA replication stress. p130RB2 binds to ETAA1, but not TopBP1, and depletion of p130RB2 inhibits the RPA32-ETAA1 interaction under replication stress. Moreover, p130RB2 depletion reduces ATR activation accompanied by phosphorylation of its targets RPA32, Chk1, and ATR itself. It also causes improper re-progression of S phase with retaining single-stranded DNA after cancelation of the stress, which leads to an increase in the anaphase bridge phenotype and a decrease in cell survival. Importantly, restoration of p130RB2 rescued the disrupted phenotypes of p130RB2 knockdown cells. These results suggest positive involvement of p130RB2 in the RPA32-ETAA1-ATR axis and proper re-progression of the cell cycle to maintain genome integrity.

Next-generation sequencing study on poorly differentiated carcinoma derived from a thirty-year-old epidermoid cyst: A case report

Although epidermoid cysts are frequently seen as benign lesions, they are highly uncommon to develop into cancerous lesions. A 36-year-old man with a cystic mass present on his left flank since childhood presented to our department. Based on the patient’s medical history and abdominal computed tomography scan, we excised the lesion under the suspicion of an epidermoid cyst. Histopathological evaluation revealed the presence of poorly differentiated carcinoma with squamoid and basaloid differentiation, which showed a strong possibility of carcinoma arising from an epidermal cyst. Next-generation sequencing using TruSight oncology 500 assay showed copy number variation of ATM and CHEK1 genes.

Organelle-selective click labeling coupled with flow cytometry allows pooled CRISPR screening of genes involved in phosphatidylcholine metabolism

Cellular lipid synthesis and transport are governed by intricate protein networks. Although genetic screening should contribute to deciphering the regulatory networks of lipid metabolism, technical challenges remain-especially for high-throughput readouts of lipid phenotypes. Here, we coupled organelle-selective click labeling of phosphatidylcholine (PC) with flow cytometry-based CRISPR screening technologies to convert organellar PC phenotypes into a simple fluorescence readout for genome-wide screening. This technique, named O-ClickFC, was successfully applied in genome-scale CRISPR-knockout screens to identify previously reported genes associated with PC synthesis (PCYT1A, ACACA), vesicular membrane trafficking (SEC23B, RAB5C), and non-vesicular transport (PITPNB, STARD7). Moreover, we revealed previously uncharacterized roles of FLVCR1 as a choline uptake facilitator, CHEK1 as a post-translational regulator of the PC-synthetic pathway, and CDC50A as responsible for the translocation of PC to the outside of the plasma membrane bilayer. These findings demonstrate the versatility of O-ClickFC as an unprecedented platform for genetic dissection of cellular lipid metabolism.

Dual inhibition of CHK1/FLT3 enhances cytotoxicity and overcomes adaptive and acquired resistance in FLT3-ITD acute myeloid leukemia

FLT3 inhibitors (FLT3i) are widely used for the treatment of acute myeloid leukemia (AML), but adaptive and acquired resistance remains a primary challenge. Inhibitors simultaneously blocking adaptive and acquired resistance are highly demanded. Here, we observed the potential of CHK1 inhibitors to synergistically improve the therapeutic effect of FLT3i in FLT3-mutated AML cells. Notably, the combination overcame adaptive resistance. The simultaneous targeting of FLT3 and CHK1 kinases may overcome acquired and adaptive resistance. A dual FLT3/CHK1 inhibitor 30 with a good oral PK profile was identified. Mechanistic studies indicated that 30 inhibited FLT3 and CHK1, downregulated the c-Myc pathway and further activated the p53 pathway. Functional studies showed that 30 was more selective against cells with various FLT3 mutants, overcame adaptive resistance in vitro, and effectively inhibited resistant FLT3-ITD AML in vivo. Moreover, 30 showed favorable druggability without significant blood toxicity or myelosuppression and exhibited a good oral PK profile with a T_1/2 over 12 h in beagles. These findings support the targeting of FLT3 and CHK1 as a novel strategy for overcoming adaptive and acquired resistance to FLT3i therapy in AML and suggest 30 as a potential clinical candidate.

Monitoring Chk1 kinase activity dynamics in live single cell imaging assays

The ATR/Chk1 pathway is an important regulator of cell cycle progression, notably upon genotoxic stress where it can detect a large variety of DNA alterations and induce a transient cell cycle arrest that promotes DNA repair. In addition to its role in DNA damage response (DDR), Chk1 is also active during a non-perturbed S phase and contributes to prevent a premature entry into mitosis with an incompletely replicated genome, meaning the ATR/Chk1 pathway is an integral part of the cell cycle machinery that preserves genome integrity during cell growth. We recently developed a FRET-based Chk1 kinase activity reporter to directly monitor and quantify the kinetics of Chk1 activation in live single cell imaging assays with unprecedented sensitivity and time resolution. This tool allowed us to monitor Chk1 activity dynamics over time during a normal S phase and following genotoxic stress, and to elucidate the underlying mechanisms leading to its activation. Here, we review available fluorescent tools to study the interplay of cell cycle progression, DNA damage and DDR in individual live cells, and present the full protocol and image analysis pipeline to monitor Chk1 activity in two imaging assays.

Integrative multi-omics networks identify PKCδ and DNA-PK as master kinases of glioblastoma subtypes and guide targeted cancer therapy

Despite producing a panoply of potential cancer-specific targets, the proteogenomic characterization of human tumors has yet to demonstrate value for precision cancer medicine. Integrative multi-omics using a machine-learning network identified master kinases responsible for effecting phenotypic hallmarks of functional glioblastoma subtypes. In subtype-matched patient-derived models, we validated PKCδ and DNA-PK as master kinases of glycolytic/plurimetabolic and proliferative/progenitor subtypes, respectively, and qualified the kinases as potent and actionable glioblastoma subtype-specific therapeutic targets. Glioblastoma subtypes were associated with clinical and radiomics features, orthogonally validated by proteomics, phospho-proteomics, metabolomics, lipidomics and acetylomics analyses, and recapitulated in pediatric glioma, breast and lung squamous cell carcinoma, including subtype specificity of PKCδ and DNA-PK activity. We developed a probabilistic classification tool that performs optimally with RNA from frozen and paraffin-embedded tissues, which can be used to evaluate the association of therapeutic response with glioblastoma subtypes and to inform patient selection in prospective clinical trials.

Inhibition of Checkpoint Kinase 1 (CHK1) Upregulates Interferon Regulatory Factor 1 (IRF1) to Promote Apoptosis and Activate Anti-Tumor Immunity via MICA in Hepatocellular Carcinoma (HCC)

BACKGROUND

CHK1 is considered a key cell cycle checkpoint kinase in DNA damage response (DDR) pathway to communicate with several signaling pathways involved in the tumor microenvironment (TME) in numerous cancers. However, the mechanism of CHK1 signaling regulating TME in hepatocellular carcinoma (HCC) remains unclear.

METHODS

CHK1 expression in HCC tissue was determined by IHC staining assay. DNA damage and apoptosis in HCC cells induced by cisplatin or CHK1 inhibition were detected by WB and flow cytometry. The interaction of CHK1 and IRF1 was analyzed by single-cell RNA-sequence, WB, and immunoprecipitation assay. The mechanism of IRF1 regulating MICA was investigated by ChIP-qPCR.

RESULTS

CHK1 expression is upregulated in human HCC tumors compared to the background liver. High CHK1 mRNA level predicts advanced tumor stage and worse prognosis. Cisplatin and CHK1 inhibition augment cellular DNA damage and apoptosis. Overexpressed CHK1 suppresses IRF1 expression through proteolysis. Furthermore, single-cell RNA-sequence analyses confirmed that MICA expression positively correlated with IRF1 in HCC cells. Immunoprecipitation assay showed the binding between CHK1 and IRF1. Cisplatin and CHK1 inhibition upregulate MICA expression through IRF1-mediated transcriptional effects. A novel specific cis-acting IRF response element was identified at -1756 bp in the MICA promoter region that bound IRF1 to induce MICA gene transcription. MICA may increase NK cell and CD8+T cell infiltration in HCC.

CONCLUSIONS

DNA damage regulates the interaction of CHK1 and IRF1 to activate anti-tumor immunity via the IRF1-MICA pathway in HCC.

The Combination of ATM and Chk1 Inhibitors Induces Synthetic Lethality in Colorectal Cancer Cells

Genetic abnormalities induce the DNA damage response (DDR), which enables DNA repair at cell cycle checkpoints. Although the DDR is thought to function in preventing the onset and progression of cancer, DDR-related proteins are also thought to contribute to tumorigenesis, tumor progression, and drug resistance by preventing irreparable genomic abnormalities from inducing cell death. In the present study, the combination of ataxia telangiectasia-mutated serine/threonine kinase (ATM) and checkpoint kinase 1 (Chk1) inhibition exhibited synergistic antitumor effects and induced synergistic lethality in colorectal cancer cells at a low dose. The ATM and Chk1 inhibitors synergistically promoted the activation of cyclin-dependent kinase 1 by decreasing the phosphorylation levels of T14 and Y15. Furthermore, the combined treatment increased the number of sub-G1-stage cells, phospho-histone H2A.X-positive cells, and TdT-mediated dUTP nick-end labeling-positive cells among colon cancer cells, suggesting that the therapy induces apoptosis. Finally, the combined treatment exhibited a robust antitumor activity in syngeneic tumor model mice. These findings should contribute to the development of new treatments for colorectal cancer that directly exploit the genomic instability of cancer cells.

The ATR Inhibitor VE-821 Enhances the Radiosensitivity and Suppresses DNA Repair Mechanisms of Human Chondrosarcoma Cells

To overcome the resistance to radiotherapy in chondrosarcomas, the prevention of efficient DNA repair with an additional treatment was explored for particle beams as well as reference X-ray irradiation. The combined treatment with DNA repair inhibitors-with a focus on ATRi VE-821-and proton or carbon ions irradiation was investigated regarding cell viability, proliferation, cell cycle distribution, MAPK phosphorylation, and the expression of key DNA repair genes in two human chondrosarcoma cell lines. Pre-treatment with the PARPis Olaparib or Veliparib, the ATMi Ku-55933, and the ATRi VE-821 resulted in a dose-dependent reduction in viability, whereas VE-821 has the most efficient response. Quantification of γH2AX phosphorylation and protein expression of the DNA repair pathways showed a reduced regenerative capacity after irradiation. Furthermore, combined treatment with VE-821 and particle irradiation increased MAPK phosphorylation and the expression of apoptosis markers. At the gene expression and at the protein expression/phosphorylation level, we were able to demonstrate the preservation of DNA damage after combined treatment. The present data showed that the combined treatment with ATMi VE-821 increases the radiosensitivity of human chondrosarcoma cells in vitro and significantly suppresses efficient DNA repair mechanisms, thus improving the efficiency of radiotherapy.

DNA Damage Response Alterations in Ovarian Cancer: From Molecular Mechanisms to Therapeutic Opportunities

The DNA damage response (DDR), a set of signaling pathways for DNA damage detection and repair, maintains genomic stability when cells are exposed to endogenous or exogenous DNA-damaging agents. Alterations in these pathways are strongly associated with cancer development, including ovarian cancer (OC), the most lethal gynecologic malignancy. In OC, failures in the DDR have been related not only to the onset but also to progression and chemoresistance. It is known that approximately half of the most frequent subtype, high-grade serous carcinoma (HGSC), exhibit defects in DNA double-strand break (DSB) repair by homologous recombination (HR), and current evidence indicates that probably all HGSCs harbor a defect in at least one DDR pathway. These defects are not restricted to HGSCs; mutations in ARID1A, which are present in 30% of endometrioid OCs and 50% of clear cell (CC) carcinomas, have also been found to confer deficiencies in DNA repair. Moreover, DDR alterations have been described in a variable percentage of the different OC subtypes. Here, we overview the main DNA repair pathways involved in the maintenance of genome stability and their deregulation in OC. We also recapitulate the preclinical and clinical data supporting the potential of targeting the DDR to fight the disease.

Therapeutic targets in cancer treatment: Cell cycle proteins

Cancer has been linked to the uncontrolled proliferation of cells and the overexpression of cell-cycle genes. The cell cycle machinery plays a crucial role in the regulation of the apoptosis to mitosis to growth phase progression. The mechanisms of the cell cycle also play an important role in preventing DNA damage. There are multiple members of the protein kinase family that are involved in the activities of the cell cycle. Essential cyclins effectively regulate cyclin-dependent kinases (CDKs), which are themselves adversely regulated by naturally occurring CDK inhibitors. Despite the fact that various compounds can effectively block the cell cycle kinases and being investigated for their potential to fight cancer. This chapter explains the detail of cell cycle and checkpoint regulators, that are crucial to the malignant cellular process. The known CDKs inhibitors and their mechanism of action in various cancers have also been addressed as a step toward the development of a possibly novel technique for the design of new drugs against cell cycle kinase proteins.

Chk1 inhibition-induced BRCAness synergizes with olaparib in p53-deficient cancer cells

Although targeting DNA-damage repair by inhibition of PARP exhibits weak or modest single-agent activity due to the existence of functional BRCA1/2 alleles, PARP inhibitors have been gradually applicable in BRCA-proficient cancers. Checkpoint kinase 1 (Chk1) inhibition selectively disrupts homologous recombination (HR)-mediated DNA repair and confers synthetic lethality in p53-deficient tumors, we therefore aim at expounding the chemopotentiating effects of Chk1 inhibition on PARPi in BRCA-proficient and p53-deficient cancer cells. Initially, BRCA wild-type, p53-null cells including AsPC-1 and H1299 demonstrated innate resistance to PARP inhibitor olaparib compared to BRCA1-mutant, p53-null MDA-MB-436 cells. We quantified the interaction between olaparib and a selective Chk1 inhibitor MK-8776, which produced synergistic effects under sub-IC50 concentrations in p53-depleted AsPC-1 and H1299 cells. Olaparib in combination with MK-8776 showed enhanced antitumor effects through prohibiting proliferation and secondarily inducing apoptosis in two cell lines. Of note, we observed that MK-8776 significantly sensitized cells to olaparib by broad DNA and chromosomal breaks. Mechanistically, MK-8776 abrogated olaparib-induced BRCA1 intranuclear foci formation, MCM7-mediated replication machineries, and ultimately triggered an accumulation of γH2AX, a well-recognized marker of DNA double-strand breaks. Additionally, we established ectopic expression of hotspot mutant p53 in H1299 cells. Introduction of p53R175 H promoted olaparib resistance as single-agent treatment, but the synergy between olaparib and MK-8776 was still achievable and the region of synergy was produced by lower combination concentrations. These data provide insight into how Chk1 inhibition could be effectively targeted and confer sensitivity to olaparib toward p53-deficient and HR-proficient cancers.

Expressional and functional characteristics of checkpoint kinase 1 as a prognostic biomarker in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the most common pathological subtype of liver cancer and is the third leading cause of cancer death worldwide. Checkpoint kinase 1 (CHEK1), an essential serine/threonine kinase that regulates the cell cycle, is reported to be associated with carcinogenesis. However, the biological role and clinical significance of CHEK1 in HCC are still incompletely known.

Methods

In this research, CHEK1 messenger RNA (mRNA) levels in various liver hepatocellular carcinoma (LIHC) cohorts from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases were evaluated. The Kaplan-Meier database was applied to identify the correlation between survival time and CHEK1 expression in patients with HCC. Gene set enrichment analysis (GSEA) was performed to explore the potential mechanism of CHEK1 in HCC, and NetworkAnalyst v. 3.0 (https://www.networkanalyst.ca/) was used to construct the regulatory networks of CHEK1 in HCC. Discriminant Regulon Expression Analysis (DoRothEA) was used to detect the activity of transcriptional factors (TFs) in gene-enriched cells (EC) with CHEK1 coexpression. In vitro experiments were conducted to investigate the effects of CHEK1 on the biological function of HCC cells.

Results

The CHEK1 mRNA level was overexpressed in HCC, and increased CHEK1 expression correlated with poor survival outcomes. The homo sapiens-microRNA-195 (hsa-miR-195) may have contributed to the upregulation of CHEK1 in HCC. GSEA and NetworkAnalyst v. 3.0 showed that CHEK1 played a crucial part in tumor proliferation of HCC and may be regulated by TF E2F1. DoRothEA showed increased transcriptional activity of E2F1 in gene-EC with CHEK1 coexpression. Moreover, experiments of cell function showed that the knockdown of CHEK1 weakened the aggressive behavior and proliferation of HCC cells. Overexpression of E2F1 increased the proliferation and invasion of HCC cells in vitro, while the silencing of CHEK1 dampened cell invasion induced by E2F1 overexpression.

Conclusions

These results identified the prognostic significance and expression characteristics of CHEK1 in HCC through bioinformatics analysis and experimental verification. This lays the foundation for further research on the diagnosis and treatment of HCC.

Checkpoint Kinase 1 (CHK1) Functions as Both a Diagnostic Marker and a Regulator of Epithelial-to-Mesenchymal Transition (EMT) in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is more difficult to treat and has a higher mortality rate than other subtypes. Although hormone receptor-targeted therapy is an effective treatment to increase survival rate in breast cancer patients, it is not suitable for TNBC patients. To address the issues, differentially expressed genes (DEGs) in TNBC patients from the Gene Expression Omnibus (GEO) database were analyzed. A total of 170 genes were obtained from three Genomic Spatial Events (GSEs) using the intersection of each GSE dataset and 61 DEGs were identified after validation with the gene enrichment analysis. We combined this with the degree scores from the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and protein-protein interaction (PPI) network, of which 7 genes were correlated with survival rate. Finally, a proteomics database revealed that only the CHK1 protein level was differently expressed in basal-like compared with other subtypes. We demonstrated that CHK1 expression was higher in TNBC cell lines compared with non-TNBC cell lines, and CHK1 promotes epithelial to mesenchymal transition (EMT) as well as migration and invasion ability. Our study provides new insight into the TNBC subnetwork that may be useful in the prognosis and treatment of TNBC patients.

Synthesis and Biological Evaluation of Cardiac Glycosides for Cancer Therapy by Targeting the DNA Damage Response

Cardiac glycosides (CGs) are bioactive compounds originally used to treat heart diseases, but recent studies have demonstrated their anticancer activity. We previously demonstrated that Antiaris toxicaria 2 (AT2) possesses anticancer activity in KRAS mutated lung cancers via impinging on the DNA damage response (DDR) pathway. Toward developing this class of molecules for cancer therapy, herein we report a multistep synthetic route utilizing k-strophanthidin as the initial building block for determination of structure-activity relationships (SARs). A systematic structural design approach was applied that included modifications of the sugar moiety, the glycoside linker, stereochemistry, and lactone ring substitutions to generate a library of O-glycosides and MeON-neoglycosides derivatives. These molecules were screened for their anticancer activities and their impact on DDR signaling in KRAS mutant lung cancer cells. These results demonstrate the ability to chemically synthesize CG derivatives and define the SARs to optimize AT2 as a cancer therapeutic.

Natural products targeting the ATR-CHK1 signaling pathway in cancer therapy

Cancer is one of the most severe medical conditions in the world, causing millions of deaths each year. Chemotherapy and radiotherapy are critical for treatment approaches, but both have numerous adverse health effects. Furthermore, the resistance of cancerous cells to anticancer medication leads to treatment failure. The rising burden of cancer requires novel efficacious treatment modalities. Natural remedies offer feasible alternative options against malignancy in contrast to available synthetic medication. Selective killing of cancer cells is privileged mainstream in cancer treatment, and targeted therapy represents the new tool with the potential to pursue this aim. The discovery of innovative therapies targeting essential components of DNA damage signaling and repair pathways such as ataxia telangiectasia mutated and Rad3 related Checkpoint kinase 1 (ATR-CHK1)has offered a possibility of significant therapeutic improvement in oncology. The activation and inhibition of this pathway account for chemopreventive and chemotherapeutic activity, respectively. Targeting this pathway can also aid to overcome the resistance of conventional chemo- or radiotherapy. This review enlightens the anticancer role of natural products by ATR-CHK1 activation and inhibition. Additionally, these compounds have been shown to have chemotherapeutic synergistic potential when used in combination with other anticancer drugs. Ideally, this review will trigger interest in natural products targeting ATR-CHK1 and their potential efficacy and safety as cancer lessening agents.

Ceramide nanoliposomes augment the efficacy of venetoclax and cytarabine in models of acute myeloid leukemia

Despite several new therapeutic options for acute myeloid leukemia (AML), disease relapse remains a significant challenge. We have previously demonstrated that augmenting ceramides can counter various drug-resistance mechanisms, leading to enhanced cell death in cancer cells and extended survival in animal models. Using a nanoscale delivery system for ceramide (ceramide nanoliposomes, CNL), we investigated the effect of CNL within a standard of care venetoclax/cytarabine (Ara-C) regimen. We demonstrate that CNL augmented the efficacy of venetoclax/cytarabine in in vitro, ex vivo, and in vivo models of AML. CNL treatment induced non-apoptotic cytotoxicity, and augmented cell death induced by Ara-C and venetoclax. Mechanistically, CNL reduced both venetoclax (Mcl-1) and cytarabine (Chk1) drug-resistant signaling pathways. Moreover, venetoclax and Ara-C augmented the generation of endogenous pro-death ceramide species, which was intensified with CNL. Taken together, CNL has the potential to be utilized as an adjuvant therapy to improve outcomes, potentially extending survival, in patients with AML.

Whole-Transcriptome Sequencing Reveals Characteristics of Cancer Microbiome in Korean Patients with GI Tract Cancer: Fusobacterium nucleatum as a Therapeutic Target

Remarkable progress has occurred over the past two decades in identifying microbiomes affecting the human body in numerous ways. The microbiome is linked to gastrointestinal (GI) tract cancer. The purpose of this study was to determine if there is a common microbiome among GI tract cancers and how the microbiome affects the disease. To ensure ethnic consistency, Korean patients with GI tract cancer were selected. Fusobacterium nucleatum is an enriched bacteria in all cancer tissues. F. nucleatum is a Gram-negative obligate anaerobe that promotes colorectal cancer. Through Gene Set Enrichment Analysis (GSEA) and Differentially Expressed Genes (DEG) analyses, the upregulation of the G2M checkpoint pathway was identified in the F. nucleatum-high group. Cell viability and G2M checkpoint pathway genes were examined in MC 38 cells treated with F. nucleatum. F. nucleatum upregulated the expression of G2M checkpoint pathway genes and the cell proliferation of MC 38 cells. F. nucleatum facilitated cancer’s use of G2M checkpoint pathways and F. nucleatum could be a therapeutic target in Korean GI tract cancer.

A RUNX-targeted gene switch-off approach modulates the BIRC5/PIF1-p21 pathway and reduces glioblastoma growth in mice

Glioblastoma is the most common adult brain tumour, representing a high degree of malignancy. Transcription factors such as RUNX1 are believed to be involved in the malignancy of glioblastoma. RUNX1 functions as an oncogene or tumour suppressor gene with diverse target genes. Details of the effects of RUNX1 on the acquisition of malignancy in glioblastoma remain unclear. Here, we show that RUNX1 downregulates p21 by enhancing expressions of BIRC5 and PIF1, conferring anti-apoptotic properties on glioblastoma. A gene switch-off therapy using alkylating agent-conjugated pyrrole-imidazole polyamides, designed to fit the RUNX1 DNA groove, decreased expression levels of BIRC5 and PIF1 and induced apoptosis and cell cycle arrest via p21. The RUNX1-BIRC5/PIF1-p21 pathway appears to reflect refractory characteristics of glioblastoma and thus holds promise as a therapeutic target. RUNX gene switch-off therapy may represent a novel treatment for glioblastoma.

Interfering with RUNX family proteins reduces glioblastoma growth in mice and reveals pathways involved in the maintenance of tumour growth.