Activation of the ATM kinase by ionizing radiation and phosphorylation of p53

Targeting the ATM pathway in cancer: Opportunities, challenges and personalized therapeutic strategies

Ataxia telangiectasia mutated (ATM) kinase plays a pivotal role in orchestrating the DNA damage response, maintaining genomic stability, and regulating various cellular processes. This review provides a comprehensive analysis of ATM's structure, activation mechanisms, and various functions in cancer development, progression, and treatment. I discuss ATM's dual nature as both a tumor suppressor and potential promoter of cancer cell survival in certain contexts. The article explores the complex signaling pathways mediated by ATM, its interactions with other DNA repair mechanisms, and its influence on cell cycle checkpoints, apoptosis, and metabolism. I examine the clinical implications of ATM alterations, including their impact on cancer predisposition, prognosis, and treatment response. The review highlights recent advances in ATM-targeted therapies, discussing ongoing clinical trials of ATM inhibitors and their potential in combination with other treatment modalities. I also address the challenges in developing effective biomarkers for ATM activity and patient selection strategies for personalized cancer therapy. Finally, I outline future research directions, emphasizing the need for refined biomarker development, optimized combination therapies, and strategies to overcome potential resistance mechanisms. This comprehensive overview underscores the critical importance of ATM in cancer biology and its emerging potential as a therapeutic target in precision oncology.

CEP-1347 Boosts Chk2-Mediated p53 Activation by Ionizing Radiation to Inhibit the Growth of Malignant Brain Tumor Cells

Radiation therapy continues to be the cornerstone treatment for malignant brain tumors, the majority of which express wild-type p53. Therefore, the identification of drugs that promote the ionizing radiation (IR)-induced activation of p53 is expected to increase the efficacy of radiation therapy for these tumors. The growth inhibitory effects of CEP-1347, a known inhibitor of MDM4 expression, on malignant brain tumor cell lines expressing wild-type p53 were examined, alone or in combination with IR, by dye exclusion and/or colony formation assays. The effects of CEP-1347 on the p53 pathway, alone or in combination with IR, were examined by RT-PCR and Western blot analyses. The combination of CEP-1347 and IR activated p53 in malignant brain tumor cells and inhibited their growth more effectively than either alone. Mechanistically, CEP-1347 and IR each reduced MDM4 expression, while their combination did not result in further decreases. CEP-1347 promoted IR-induced Chk2 phosphorylation and increased p53 expression in concert with IR in a Chk2-dependent manner. The present results show, for the first time, that CEP-1347 is capable of promoting Chk2-mediated p53 activation by IR in addition to inhibiting the expression of MDM4 and, thus, CEP-1347 has potential as a radiosensitizer for malignant brain tumors expressing wild-type p53.

Distinct regulation of ATM signaling by DNA single-strand breaks and APE1

In response to DNA double-strand breaks or oxidative stress, ATM-dependent DNA damage response (DDR) is activated to maintain genome integrity. However, it remains elusive whether and how DNA single-strand breaks (SSBs) activate ATM. Here, we provide direct evidence in Xenopus egg extracts that ATM-mediated DDR is activated by a defined SSB structure. Our mechanistic studies reveal that APE1 promotes the SSB-induced ATM DDR through APE1 exonuclease activity and ATM recruitment to SSB sites. APE1 protein can form oligomers to activate the ATM DDR in Xenopus egg extracts in the absence of DNA and can directly stimulate ATM kinase activity in vitro. Our findings reveal distinct mechanisms of the ATM-dependent DDR activation by SSBs in eukaryotic systems and identify APE1 as a direct activator of ATM kinase.

Key molecular DNA damage responses of human cells to radiation

Our understanding of the DNA damage responses of human cells to radiation has increased remarkably over the recent years although some notable signaling events remain to be discovered. Here we provide a brief account of the key molecular events of the responses to reflect the current understanding of the key underlying mechanisms involved.

CX-5461 Preferentially Induces Top2α-Dependent DNA Breaks at Ribosomal DNA Loci

While genotoxic chemotherapeutic agents are among the most effective tools to combat cancer, they are often associated with severe adverse effects caused by indiscriminate DNA damage in non-tumor tissue as well as increased risk of secondary carcinogenesis. This study builds on our previous work demonstrating that the RNA Polymerase I (Pol I) transcription inhibitor CX-5461 elicits a non-canonical DNA damage response and our discovery of a critical role for Topoisomerase 2α (Top2α) in the initiation of Pol I-dependent transcription. Here, we identify Top2α as a mediator of CX-5461 response in the murine Eµ-Myc B lymphoma model whereby sensitivity to CX-5461 is dependent on cellular Top2α expression/activity. Most strikingly, and in contrast to canonical Top2α poisons, we found that the Top2α-dependent DNA damage induced by CX-5461 is preferentially localized at the ribosomal DNA (rDNA) promoter region, thereby highlighting CX-5461 as a loci-specific DNA damaging agent. This mechanism underpins the efficacy of CX-5461 against certain types of cancer and can be used to develop effective non-genotoxic anticancer drugs.

The totipotent 2C-like state safeguards genomic stability of mouse embryonic stem cells

Mouse embryonic stem cells (mESCs) sporadically transition to a transient totipotent state that resembles blastomeres of the two-cell (2C) embryo stage, which has been proposed to contribute to exceptional genomic stability, one of the key features of mESCs. However, the biological significance of the rare population of 2C-like cells (2CLCs) in ESC cultures remains to be tested. Here we generated an inducible reporter cell system for specific elimination of 2CLCs from the ESC cultures to disrupt the equilibrium between ESCs and 2CLCs. We show that removing 2CLCs from the ESC cultures leads to dramatic accumulation of DNA damage, genomic mutations, and rearrangements, indicating impaired genomic instability. Furthermore, 2CLCs removal results in increased apoptosis and reduced proliferation of mESCs in both serum/LIF and 2i/LIF culture conditions. Unexpectedly, p53 deficiency results in defective response to DNA damage, leading to early accumulation of DNA damage, micronuclei, indicative of genomic instability, cell apoptosis, and reduced self-renewal capacity of ESCs when devoid of 2CLCs in cultures. Together, our data reveal that transition to the privileged 2C-like state is a major component of the intrinsic mechanisms that maintain the exceptional genomic stability of mESCs for long-term self-renewal.

Understanding the complexity of p53 in a new era of tumor suppression

p53 was discovered 45 years ago as an SV40 large T antigen binding protein, coded by the most frequently mutated TP53 gene in human cancers. As a transcription factor, p53 is tightly regulated by a rich network of post-translational modifications to execute its diverse functions in tumor suppression. Although early studies established p53-mediated cell-cycle arrest, apoptosis, and senescence as the classic barriers in cancer development, a growing number of new functions of p53 have been discovered and the scope of p53-mediated anti-tumor activity is largely expanded. Here, we review the complexity of different layers of p53 regulation, and the recent advance of the p53 pathway in metabolism, ferroptosis, immunity, and others that contribute to tumor suppression. We also discuss the challenge regarding how to activate p53 function specifically effective in inhibiting tumor growth without harming normal homeostasis for cancer therapy.

A Novel Dual ATM/DNA-PK Inhibitor, XRD-0394, Potently Radiosensitizes and Potentiates PARP and Topoisomerase I Inhibitors

A majority of patients with cancer receive radiotherapy as part of their treatment regimens whether using external beam therapy or locally-delivered radioisotopes. While often effective, some tumors are inadequately controlled with radiation and radiotherapy has significant short-term and long-term toxicities for cancer survivors. Insights into molecular mechanisms involved in cellular responses to DNA breaks introduced by radiation or other cancer therapies have been gained in recent years and approaches to manipulate these responses to enhance tumor cell killing or reduce normal tissue toxicity are of great interest. Here, we report the identification and initial characterization of XRD-0394, a potent and specific dual inhibitor of two DNA damage response kinases, ATM and DNA-PKcs. This orally bioavailable molecule demonstrates significantly enhanced tumor cell kill in the setting of therapeutic ionizing irradiation in vitro and in vivo. XRD-0394 also potentiates the effectiveness of topoisomerase I inhibitors in vitro. In addition, in cells lacking BRCA1/2 XRD-0394 shows single-agent activity and synergy in combination with PARP inhibitors. A phase Ia clinical trial (NCT05002140) with XRD-0394 in combination with radiotherapy has completed. These results provide a rationale for future clinical trials with XRD-0394 in combination with radiotherapy, PARP inhibitors, and targeted delivery of topoisomerase I inhibitors.

The DNA damage-independent ATM signalling maintains CBP/DOT1L axis in MLL rearranged acute myeloid leukaemia

The long-term maintenance of leukaemia stem cells (LSCs) is responsible for the high degree of malignancy in MLL (mixed-lineage leukaemia) rearranged acute myeloid leukaemia (AML). The DNA damage response (DDR) and DOT1L/H3K79me pathways are required to maintain LSCs in MLLr-AML, but little is known about their interplay. This study revealed that the DDR enzyme ATM regulates the maintenance of LSCs in MLLr-AML with a sequential protein-posttranslational-modification manner via CBP-DOT1L. We identified the phosphorylation of CBP by ATM, which confers the stability of CBP by preventing its proteasomal degradation, and characterised the acetylation of DOT1L by CBP, which mediates the high level of H3K79me2 for the expression of leukaemia genes in MLLr-AML. In addition, we revealed that the regulation of CBP-DOT1L axis in MLLr-AML by ATM was independent of DNA damage activation. Our findings provide insight into the signalling pathways involoved in MLLr-AML and broaden the understanding of the role of DDR enzymes beyond processing DNA damage, as well as identigying them as potent cancer targets.

Mechanistic insights into DNA damage recognition and checkpoint control in plants

The plant DNA damage response (DDR) pathway safeguards genomic integrity by rapid recognition and repair of DNA lesions that, if unrepaired, may cause genome instability. Most frequently, DNA repair goes hand in hand with a transient cell cycle arrest, which allows cells to repair the DNA lesions before engaging in a mitotic event, but consequently also affects plant growth and yield. Through the identification of DDR proteins and cell cycle regulators that react to DNA double-strand breaks or replication defects, it has become clear that these proteins and regulators form highly interconnected networks. These networks operate at both the transcriptional and post-transcriptional levels and include liquid-liquid phase separation and epigenetic mechanisms. Strikingly, whereas the upstream DDR sensors and signalling components are well conserved across eukaryotes, some of the more downstream effectors are diverged in plants, probably to suit unique lifestyle features. Additionally, DDR components display functional diversity across ancient plant species, dicots and monocots. The observed resistance of DDR mutants towards aluminium toxicity, phosphate limitation and seed ageing indicates that gaining knowledge about the plant DDR may offer solutions to combat the effects of climate change and the associated risk for food security.

Plasma membrane damage limits replicative lifespan in yeast and induces premature senescence in human fibroblasts

Plasma membrane damage (PMD) occurs in all cell types due to environmental perturbation and cell-autonomous activities. However, cellular outcomes of PMD remain largely unknown except for recovery or death. In this study, using budding yeast and normal human fibroblasts, we found that cellular senescence-stable cell cycle arrest contributing to organismal aging-is the long-term outcome of PMD. Our genetic screening using budding yeast unexpectedly identified a close genetic association between PMD response and replicative lifespan regulations. Furthermore, PMD limits replicative lifespan in budding yeast; upregulation of membrane repair factors ESCRT-III (SNF7) and AAA-ATPase (VPS4) extends it. In normal human fibroblasts, PMD induces premature senescence via the Ca2+-p53 axis but not the major senescence pathway, DNA damage response pathway. Transient upregulation of ESCRT-III (CHMP4B) suppressed PMD-dependent senescence. Together with mRNA sequencing results, our study highlights an underappreciated but ubiquitous senescent cell subtype: PMD-dependent senescent cells.

Kaposi's sarcoma herpesvirus exploits the DNA damage response to circularize its genome

To establish lifelong, latent infection, herpesviruses circularize their linear, double-stranded, DNA genomes through an unknown mechanism. Kaposi's sarcoma (KS) herpesvirus (KSHV), a gamma herpesvirus, is tightly linked with KS, primary effusion lymphoma, and multicentric Castleman's disease. KSHV persists in latently infected cells as a multi-copy, extrachromosomal episome. Here, we show the KSHV genome rapidly circularizes following infection, and viral protein expression is unnecessary for this process. The DNA damage response (DDR) kinases, ATM and DNA-PKcs, each exert roles, and absence of both severely compromises circularization and latency. These deficiencies were rescued by expression of ATM and DNA-PKcs, but not catalytically inactive mutants. In contrast, γH2AX did not function in KSHV circularization. The linear viral genomic ends resemble a DNA double strand break, and non-homologous DNA end joining (NHEJ) and homologous recombination (HR) reporters indicate both NHEJ and HR contribute to KSHV circularization. Last, we show, similar to KSHV, ATM and DNA-PKcs have roles in circularization of the alpha herpesvirus, herpes simplex virus-1 (HSV-1), while γH2AX does not. Therefore, the DDR mediates KSHV and HSV-1 circularization. This strategy may serve as a general herpesvirus mechanism to initiate latency, and its disruption may provide new opportunities for prevention of herpesvirus disease.

REV7-p53 interaction inhibits ATM-mediated DNA damage signaling

REV7 is an abundant, multifunctional protein that is a known factor in cell cycle regulation and in several key DNA repair pathways including Trans-Lesion Synthesis (TLS), the Fanconi Anemia (FA) pathway, and DNA Double-Strand Break (DSB) repair pathway choice. Thus far, no direct role has been studied for REV7 in the DNA damage response (DDR) signaling pathway. Here we describe a novel function for REV7 in DSB-induced p53 signaling. We show that REV7 binds directly to p53 to block ATM-dependent p53 Ser15 phosphorylation. We also report that REV7 is involved in the destabilization of p53. These findings affirm REV7's participation in fundamental cell cycle and DNA repair pathways. Furthermore, they highlight REV7 as a critical factor for the integration of multiple processes that determine viability and genome stability.

Long non-coding RNA (lncRNA) PVT1 in drug resistance of cancers: Focus on pathological mechanisms

According to estimates, cancer will be the leading cause of death globally in 2022, accounting for 9.6 million deaths. At present, the three main therapeutic modalities utilized to treat cancer are radiation therapy, chemotherapy, and surgery. However, during treatment, tumor cells resistant to chemotherapy may arise. Drug resistance remains a major oppose since it often leads to therapeutic failure. Furthermore, the term "acquired drug resistance" describes the situation where tumor cells already display drug resistance before undergoing chemotherapy. However, little is still known about the basic mechanisms underlying chemotherapy-induced drug resistance. The development of new technologies and bioinformatics has led to the discovery of additional genes associated with drug resistance. Long noncoding RNA plasmacytoma variant translocation 1 (PVT1) has been linked to an increased risk of cancer, according to a growing body of research. Apart from biological functions associated with cell division, development, pluripotency, and cell cycle, lncRNA PVT1 contributes significantly to the regulation of various aspects of genome function, such as transcription, splicing, and epigenetics. The article will address the mechanism by which lncRNA PVT1 influences drug resistance in cancer cells.

Comparison of cellular responses to ionizing radiation in keratinocytes isolated from healthy donors and type II diabetes patients

PURPOSE

Due to the expanding repertoire of treatment devices that use radiation, the possibility of exposure to both low-dose and high-dose radiation continues to increase. Skin is the outermost part of the body and thus directly exposed to radiation-induced damage. In particular, the skin of diabetes patients is fragile and easily damaged by external stimuli, such as radiation. However, damage and cellular responses induced by ionizing irradiation in diabetic skin have not been explored in detail. In this study, we investigated the effects of several irradiation dose on normal keratinocytes and those from type II diabetes patients, with particular focus on DNA damage.

MATERIALS AND METHODS

Cellular responses to low-dose radiation (0.1 Gy) and high-dose radiation (0.5 and 2 Gy) were evaluated. Cell cycle analysis was conducted via flow cytometry and cell viability analyzed using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Proteins related to the DNA damage response (DDR) and repair signaling pathways and apoptosis were detected via immunoblot analysis. Apoptosis and cell differentiation were additionally examined in 3D skin organoids using immunohistochemistry.

RESULTS

Compared to respective control groups, no significant changes were observed in cell cycle, DDR and repair mechanisms, cell survival, and differentiation in response to 0.1 Gy irradiation in both normal and diabetes type II keratinocytes. On the other hand, the cell cycle showed an increase in the G2/M phase in both cell types following exposure to 2 Gy irradiation. At radiation doses 2 Gy, activation of the DDR and repair signaling pathways, apoptosis, and cell differentiation were increased and viability was decreased in both cell types. Notably, these differences were more pronounced in normal than diabetes type II keratinocytes.

CONCLUSIONS

Normal keratinocytes respond more strongly to radiation-induced damage and recovery than diabetes type II keratinocytes.

Differential effects of pesticides on dioxin receptor signaling and p53 activation

As modern agricultural practices increase their use of chemical pesticides, it is inevitable that we will find a number of these xenobiotics within drinking water supplies and disseminated throughout the food chain. A major problem that arises from this pollution is that the effects of most of these pesticides on cellular mechanisms in general, and how they interact with each other and affect human cells are still poorly understood. In this study we make use of cultured human cancer cells to measure by qRT-PCR how pesticides affect gene expression of stress pathways. Immunoblotting studies were performed to monitor protein expression levels and activation of signaling pathways. We make use of immunofluorescence and microscopy to visualize and quantify DNA damage events in those cells. In the current study, we evaluate the potential of a subset of widely used pesticides to activate the dioxin receptor pathway and affect its crosstalk with estrogen receptor signaling. We quantify the impact of these chemicals on the p53-dependent cellular stress response. We find that, not only can the different pesticides activate the dioxin receptor pathway, most of them have better than additive effects on this pathway when combined at low doses. We also show that different pesticides have the ability to trigger crosstalk events that may generate genotoxic estrogen metabolites. Finally, we show that some, but not all of the tested pesticides can induce a p53-dependent stress response. Taken together our results provide evidence that several xenobiotics found within the environment have the potential to interact together to elicit significant effects on cell systems. Our data warrants caution when the toxicity of substances that are assessed simply for individual chemicals, since important biological effects could be observed only in the presence of other compounds, and that even at very low concentrations.

Ataxia Telangiectasia Mutated Signaling Delays Skin Pigmentation upon UV Exposure by Mediating MITF Function toward DNA Repair Mode

Skin pigmentation is paused after sun exposure; however, the mechanism behind this pausing is unknown. In this study, we found that the UVB-induced DNA repair system, led by the ataxia telangiectasia mutated (ATM) protein kinase, represses MITF transcriptional activity of pigmentation genes while placing MITF in DNA repair mode, thus directly inhibiting pigment production. Phosphoproteomics analysis revealed ATM to be the most significantly enriched pathway among all UVB-induced DNA repair systems. ATM inhibition in mouse or human skin, either genetically or chemically, induces pigmentation. Upon UVB exposure, MITF transcriptional activation is blocked owing to ATM-dependent phosphorylation of MITF on S414, which modifies MITF activity and interactome toward DNA repair, including binding to TRIM28 and RBBP4. Accordingly, MITF genome occupancy is enriched in sites of high DNA damage that are likely repaired. This suggests that ATM harnesses the pigmentation key activator for the necessary rapid, efficient DNA repair, thus optimizing the chances of the cell surviving. Data are available from ProteomeXchange with the identifier PXD041121.

A mitochondria-regulated p53-CCF circuit integrates genome integrity with inflammation

Genomic instability and inflammation are distinct hallmarks of aging, but the connection between them is poorly understood. Understanding their interrelationship will help unravel new mechanisms and therapeutic targets of aging and age-associated diseases. Here we report a novel mechanism directly linking genomic instability and inflammation in senescent cells, through a mitochondria-regulated molecular circuit that connects the p53 tumor suppressor and cytoplasmic chromatin fragments (CCF), a driver of inflammation through the cGAS-STING pathway. Activation or inactivation of p53 by genetic and pharmacologic approaches showed that p53 suppresses CCF accumulation and the downstream inflammatory senescence-associated secretory phenotype (SASP), independent of its effects on cell cycle arrest. p53 activation suppressed CCF formation by promoting DNA repair, reflected in maintenance of genomic integrity, particularly in subtelomeric regions, as shown by single cell genome resequencing. Activation of p53 by pharmacological inhibition of MDM2 in old mice decreased features of SASP in liver, indicating a senomorphic role in vivo . Remarkably, mitochondria in senescent cells suppressed p53 activity by promoting CCF formation and thereby restricting ATM-dependent nuclear DNA damage signaling. These data provide evidence for a mitochondria-regulated p53-CCF circuit in senescent cells that controls DNA repair, genome integrity and inflammatory SASP, and is a potential target for senomorphic healthy aging interventions.

Spontaneous p53 activation in middle-aged C57BL/6 mice mitigates the lifespan-extending adaptive response induced by low-dose ionizing radiation

Understanding the biological effects of low-dose (<100 mGy) ionizing radiation (LDR) is technically challenging. We investigated age-dependent LDR effects using adaptive response experiments in young (7-to 12-week-old) and middle-aged (40-to 62-week-old) C57BL/6 mice. Compared with 3 Gy irradiation, 0.02 Gy preirradiation followed by 3 Gy irradiation prolonged life in young mice but not middle-aged mice. Preirradiation also suppressed irradiation-induced 53BP1 repair foci in the small intestines, splenic apoptosis, and p53 activity in young mice but not middle-aged mice. Young p53+/- C57BL/6 mice did not show these adaptive responses, indicating that insufficient p53 function in young mice mitigated the adaptive responses. Interestingly, p53 activation in middle-aged mice spontaneously became approximately 4.5-fold greater than that in young mice, possibly masking LDR stresses. Furthermore, adaptive responses in young mice, but not in middle-aged mice, suppressed some senescence-associated secretory phenotype (SASP) factors (IL-6, CCL2, CCL5, CXCL1). Thus, LDR-induced adaptive responses associated with specific SASP factors may be attenuated by a combination of reduced DNA damage sensor/transducer function and chronic p53 activation in middle-aged mice.

DNA damage and repair: underlying mechanisms leading to microcephaly

DNA-damaging agents and endogenous DNA damage constantly harm genome integrity. Under genotoxic stress conditions, the DNA damage response (DDR) machinery is crucial in repairing lesions and preventing mutations in the basic structure of the DNA. Different repair pathways are implicated in the resolution of such lesions. For instance, the non-homologous DNA end joining and homologous recombination pathways are central cellular mechanisms by which eukaryotic cells maintain genome integrity. However, defects in these pathways are often associated with neurological disorders, indicating the pivotal role of DDR in normal brain development. Moreover, the brain is the most sensitive organ affected by DNA-damaging agents compared to other tissues during the prenatal period. The accumulation of lesions is believed to induce cell death, reduce proliferation and premature differentiation of neural stem and progenitor cells, and reduce brain size (microcephaly). Microcephaly is mainly caused by genetic mutations, especially genes encoding proteins involved in centrosomes and DNA repair pathways. However, it can also be induced by exposure to ionizing radiation and intrauterine infections such as the Zika virus. This review explains mammalian cortical development and the major DNA repair pathways that may lead to microcephaly when impaired. Next, we discuss the mechanisms and possible exposures leading to DNA damage and p53 hyperactivation culminating in microcephaly.

Structure and function of the apical PIKKs in double-strand break repair

Members of the phosphatidylinositol 3' kinase (PI3K)-related kinases (PIKKs) family, including DNA-dependent protein kinase catalytic subunit (DNA-PKcs), ataxia telangiectasia mutated (ATM), ataxia-telangiectasia mutated and Rad3-related (ATR), mammalian target of rapamycin (mTOR), suppressor with morphological effect on genitalia 1 (SMG1), and transformation/transcription domain-associated protein 1 (TRRAP/Tra1), participate in a variety of physiological processes, such as cell-cycle control, metabolism, transcription, replication, and the DNA damage response. In eukaryotic cells, DNA-PKcs, ATM, and ATR-ATRIP are the main sensors and regulators of DNA double-strand break repair. The purpose of this review is to describe recent structures of DNA-PKcs, ATM, and ATR, as well as their functions in activation and phosphorylation in different DNA repair pathways.

Cancer cell-specific cGAS/STING Signaling pathway in the era of advancing cancer cell biology

Pattern-recognition receptors (PRRs) are critical to recognizing endogenous and exogenous threats to mount a protective proinflammatory innate immune response. PRRs may be located on the outer cell membrane, cytosol, and nucleus. The cGAS/STING signaling pathway is a cytosolic PRR system. Notably, cGAS is also present in the nucleus. The cGAS-mediated recognition of cytosolic dsDNA and its cleavage into cGAMP activates STING. Furthermore, STING activation through its downstream signaling triggers different interferon-stimulating genes (ISGs), initiating the release of type 1 interferons (IFNs) and NF-κB-mediated release of proinflammatory cytokines and molecules. Activating cGAS/STING generates type 1 IFN, which may prevent cellular transformation and cancer development, growth, and metastasis. The current article delineates the impact of the cancer cell-specific cGAS/STING signaling pathway alteration in tumors and its impact on tumor growth and metastasis. This article further discusses different approaches to specifically target cGAS/STING signaling in cancer cells to inhibit tumor growth and metastasis in conjunction with existing anticancer therapies.

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.

p53-dependent DNA repair during the DNA damage response requires actin nucleation by JMY

The tumour suppressor p53 is a nuclear transcription factor with key roles during DNA damage to enable a variety of cellular responses including cell cycle arrest, apoptosis and DNA repair. JMY is an actin nucleator and DNA damage-responsive protein whose sub-cellular localisation is responsive to stress and during DNA damage JMY undergoes nuclear accumulation. To gain an understanding of the wider role for nuclear JMY in transcriptional regulation, we performed transcriptomics to identify JMY-mediated changes in gene expression during the DNA damage response. We show that JMY is required for effective regulation of key p53 target genes involved in DNA repair, including XPC, XRCC5 (Ku80) and TP53I3 (PIG3). Moreover, JMY depletion or knockout leads to increased DNA damage and nuclear JMY requires its Arp2/3-dependent actin nucleation function to promote the clearance of DNA lesions. In human patient samples a lack of JMY is associated with increased tumour mutation count and in cells results in reduced cell survival and increased sensitivity to DNA damage response kinase inhibition. Collectively, we demonstrate that JMY enables p53-dependent DNA repair under genotoxic stress and suggest a role for actin in JMY nuclear activity during the DNA damage response.

A kinome-wide CRISPR screen identifies CK1α as a target to overcome enzalutamide resistance of prostate cancer

Enzalutamide (ENZA), a second-generation androgen receptor antagonist, has significantly increased progression-free and overall survival of patients with metastatic prostate cancer (PCa). However, resistance remains a prominent obstacle in treatment. Utilizing a kinome-wide CRISPR-Cas9 knockout screen, we identified casein kinase 1α (CK1α) as a therapeutic target to overcome ENZA resistance. Depletion or pharmacologic inhibition of CK1α enhanced ENZA efficacy in ENZA-resistant cells and patient-derived xenografts. Mechanistically, CK1α phosphorylates the serine residue S1270 and modulates the protein abundance of ataxia telangiectasia mutated (ATM), a primary initiator of DNA double-strand break (DSB)-response signaling, which is compromised in ENZA-resistant cells and patients. Inhibition of CK1α stabilizes ATM, resulting in the restoration of DSB signaling, and thus increases ENZA-induced cell death and growth arrest. Our study details a therapeutic approach for ENZA-resistant PCa and characterizes a particular perspective for the function of CK1α in the regulation of DNA-damage response.

Participation of ATM, SMG1, and DDX5 in a DNA Damage-Induced Alternative Splicing Pathway

Altered cellular responses to DNA damage can contribute to cancer development, progression, and therapeutic resistance. Mutations in key DNA damage response factors occur across many cancer types, and the DNA damage-responsive gene, TP53, is frequently mutated in a high percentage of cancers. We recently reported that an alternative splicing pathway induced by DNA damage regulates alternative splicing of TP53 RNA and further modulates cellular stress responses. Through damage-induced inhibition of the SMG1 kinase, TP53 pre-mRNA is alternatively spliced to generate TP53b mRNA and p53b protein is required for optimal induction of cellular senescence after ionizing radiation-induced DNA damage. Herein, we confirmed and extended these observations by demonstrating that the ATM protein kinase is required for repression of SMG1 kinase activity after ionizing radiation. We found that the RNA helicase and splicing factor, DDX5, interacts with SMG1, is required for alternative splicing of TP53 pre-mRNA to TP53b and TP53c mRNAs after DNA damage, and contributes to radiation-induced cellular senescence. Interestingly, the role of SMG1 in alternative splicing of p53 appears to be distinguishable from its role in regulating nonsense-mediated RNA decay. Thus, ATM, SMG1, and DDX5 participate in a DNA damage-induced alternative splicing pathway that regulates TP53 splicing and modulates radiation-induced cellular senescence.

Inflammasome-independent NLRP3 function enforces ATM activity in response to genotoxic stress

NLRP3 is a pattern recognition receptor with a well-documented role in inducing inflammasome assembly in response to cellular stress. Deregulation of its activity leads to many inflammatory disorders including gouty arthritis, Alzheimer disease, and cancer. Whereas its role in the context of cancer has been mostly explored in the immune compartment, whether NLRP3 exerts functions unrelated to immunity in cancer development remains unexplored. Here, we demonstrate that NLRP3 interacts with the ATM kinase to control the activation of the DNA damage response, independently of its inflammasome activity. NLRP3 down-regulation in both broncho- and mammary human epithelial cells significantly impairs ATM pathway activation, leading to lower p53 activation, and provides cells with the ability to resist apoptosis induced by acute genotoxic stress. Interestingly, NLRP3 expression is down-regulated in non-small cell lung cancers and breast cancers, and its expression positively correlates with patient overall survival. Our findings identify a novel non-immune function for NLRP3 in maintaining genome integrity and strengthen the concept of a functional link between innate immunity and DNA damage sensing pathways to maintain cell integrity.

Inclusion of Nitrofurantoin into the Realm of Cancer Chemotherapy via Biology-Oriented Synthesis and Drug Repurposing

Structural modifications of the antibacterial drug nitrofurantoin were envisioned, employing drug repurposing and biology-oriented drug synthesis, to serve as possible anticancer agents. Eleven compounds showed superior safety in non-cancerous human cells. Their antitumor efficacy was assessed on colorectal, breast, cervical, and liver cancer cells. Three compounds induced oxidative DNA damage in cancer cells with subsequent cellular apoptosis. They also upregulated the expression of Bax while downregulated that of Bcl-2 along with activating caspase 3/7. The DNA damage induced by these compounds, demonstrated by pATM nuclear shuttling, was comparable in both MCF7 and MDA-MB-231 (p53 mutant) cell lines. Mechanistic studies confirmed the dependence of these compounds on p53-mediated pathways as they suppressed the p53-MDM2 interaction. Indeed, exposure of radiosensitive prostatic cancer cells to low non-cytotoxic concentrations of compound 1 enhanced the cytotoxic response to radiation indicating a possible synergistic effect. In vivo antitumor activity was verified in an MCF7-xenograft animal model.

p53 as a potential target for treatment of cancer: A perspective on recent advancements in small molecules with structural insights and SAR studies

Cancer represents one of the world's biggest hazardous diseases. p53 is the uttermost researched tumour suppressor protein. It is commonly considered the "guardian of the genome," performing a critical function in genetic stability maintenance through controlling the cell cycle, programmed cell death, DNA repair, aging, and angiogenesis. The abnormalities in p53 lead to genetic instability and plays a significant role in carcinogenesis. The role of p53 in tumour suppression is emphasized in addition by the observation that primary silencing with this protein occurred in more than 50% of cancers. MDM2, p53, and the p53-MDM2 connections are well-known targets for the prevention and treatment of cancer. Moreover, in tumors with wild-type p53, their efficacy is decreased due to MDM2 enlargement or by the gradual decrease of MDM2 blocker ARF. As a result, improving p53 activity in cancerous cells provides a promising anticancer strategy. Various techniques are now being investigated, and addressing the p53-MDM2 interaction had also evolved as a potentially feasible strategy for contending with tumors. Both p53 and MDM2, interact via an autoregulation response signal: p53 activity induces MDM2 transcription, which in response interacts with p53's N-terminal transactivation domain, inhibiting its transcriptional activity. This article provides information on the current scenario of anti-tumor activities, with a particular emphasis on structure-activity relationship characteristics (SAR) against the p53-MDM2 to treat cancer. The primary purpose of this review is to cover recent advancements in the creation and testing of anticancer drugs that target the p53-MDM2 structure. This review contains different heterocyclic moieties which show significant results toward cancer. A mechanistic route is shown here, demonstrating both normal and malignant conditions via several stressed factors. Several compounds entered clinical trials as p53-MDM2 inhibitors for the treatment of cancer.

Carrier-free nanoprodrug for p53-mutated tumor therapy via concurrent delivery of zinc-manganese dual ions and ROS

Human cancers typically express a high level of tumor-promoting mutant p53 protein (Mutp53) with a minimal level of tumor-suppressing wild-type p53 protein (WTp53). In this regard, inducing Mutp53 degradation while activating WTp53 is a viable strategy for precise anti-tumor therapy. Herein, a new carrier-free nanoprodrug (i.e., Mn-ZnO₂ nanoparticles) was developed for concurrent delivery of dual Zn-Mn ions and reactive oxygen species (ROS) within tumor to regulate the p53 protein for high anti-tumor efficacy. In response to the mild tumor acidic environment, the released Zn²⁺ and H₂O₂ from Mn-ZnO₂ NPs induced ubiquitination-mediated proteasomal degradation of Mutp53, while the liberative Mn²⁺ and increased ROS level activated the ATM-p53-Bax pathway to elevate WTp53 level. Both in vitro and in vivo results demonstrated that pH-responsive decomposition of Mn-ZnO₂ NPs could effectively elevate the intracellular dual Zn-Mn ions and ROS level and subsequently generate the cytotoxic hydroxyl radical (•OH) through the Fenton-like reaction. With the integration of multiple functions (i.e., carrier-free ion and ROS delivery, tumor accumulation, p53 protein modulation, toxic •OH generation, and pH-activated MRI contrast) in a single nanosystem, Mn-ZnO₂ NPs demonstrate its superiority as a promising nanotherapeutics for p53-mutated tumor therapy.

Selection of p53 pathway in adaptive evolution and reproductive isolation in incipient sympatric speciation of Drosophila at Evolution Canyon

Sympatric speciation (SS) refers to the origin of new species within a freely breeding population. The ‘Evolution Canyon’ (EC) in Israel is a natural microsite model for SS of species across phylogenies from viruses and bacteria to mammals, adapting to, and speciating in, interslope microclimates. The cosmopolitan Drosophila melanogaster at EC I, Mount Carmel, is undergoing incipient SS in response to sharply divergent interslope microclimate stresses, including solar radiation, temperature, humidity and pathogenicity. We demonstrated here a selective interslope divergence of single nucleotide polymorphism (SNP) distribution in the Drosophila p53 pathway. This involves a total of 71 genes, which are associated with DNA repair, heat response, and fungal and bacterial resistant pathways. This distribution pattern links the previously observed thermotolerance and ageing divergence of D. melanogaster between the opposite canyon slopes: the south-facing slope (SFS, or African slope: tropical, savannoid and dry) and the abutting north-facing slope (NFS, or European slope; temperate, forested, cool and humid). The genes with interslope-significant differential SNPs link the p53 pathway with pathways related to the responses to microclimates through protein-protein interaction. Moreover, for the first time we provide evidence that the p53 pathway is linked to reproductive isolation, and is thus actively participating in incipient SS of D. melanogaster. This is the first demonstration of a link between the p53 pathway and reproductive isolation, thereby contributing to adaptive incipient sympatric speciation.

Selective ATM inhibition augments radiation-induced inflammatory signaling and cancer cell death

Over half of all cancer patients undergo radiation therapy but there is an unmet need for more efficacious combination strategies with molecular targeted drugs. DNA damage response has emerged as an important intervention point for improving anti-tumor effects of radiation and several inhibitors are currently in development. Ataxia telangiectasia mutated (ATM) kinase is a key regulator of cellular response to DNA double strand breaks and a potential target for radiosensitization. We recently reported two new potent and selective ATM inhibitors, M3541 and M4076, that effectively sensitize cancer cells to radiation and regress human xenografts in clinically relevant animal models. Here, we dive deeper into the cellular events in irradiated cancer cells exposed to ATM inhibitors. Suppression of ATM activity inhibited radiation-induced ATM signaling and abrogated G1 checkpoint activation resulting in enhanced cell death. Our data indicated that entry into mitosis with gross structural abnormalities in multiple chromosomes is the main mechanism behind the increased cell killing. Misalignment and mis-segregation led to formation of multiple micronuclei and robust activation of the interferon response and inflammatory signaling via the cGAS/STING/TBK1 pathway. Cancer cells exposed to radiation in the presence of M3541 were more susceptible to killing in co-culture with NK cells from healthy donors. In addition, strong upregulation of PD-L1 expression was observed in the surviving irradiated cancer cells exposed to M3541. Simultaneous activation of the STING pathway and PD-L1 suggested that combination of radiation, ATM inhibitors and PD-L1 targeted therapy may offer a novel approach to radio-immunotherapy of locally advanced tumors.

A moving target for drug discovery: Structure activity relationship and many genome (de)stabilizing functions of the RAD52 protein

BRCA-ness phenotype, a signature of many breast and ovarian cancers, manifests as deficiency in homologous recombination, and as defects in protection and repair of damaged DNA replication forks. A dependence of such cancers on DNA repair factors less important for survival of BRCA-proficient cells, offers opportunities for development of novel chemotherapeutic interventions. The first drugs targeting BRCA-deficient cancers, poly-ADP-ribose polymerase (PARP) inhibitors have been approved for the treatment of advanced, chemotherapy resistant cancers in patients with BRCA1/2 germline mutations. Nine additional proteins that can be targeted to selectively kill BRCA-deficient cancer cells have been identified. Among them, a DNA repair protein RAD52 is an especially attractive target due to general tolerance of the RAD52 loss of function, and protective role of an inactivating mutation. Yet, the effective pharmacological inhibitors of RAD52 have not been forthcoming. In this review, we discuss advances in the state of our knowledge of the RAD52 structure, activities and cellular functions, with a specific focus on the features that make RAD52 an attractive, but difficult drug target.

A comprehensive study of p53 protein

The protein p53 has been extensively investigated since it was found 43 years ago and has become a "guardian of the genome" that regulates the division of cells by preventing the growth of cells and dividing them, that is, inhibits the development of tumors. Initial proof of protein existence by researchers in the mid-1970s was found by altering and regulating the SV40 big T antigen termed the A protein. Researchers demonstrated how viruses play a role in cancer by employing viruses' ability to create T-antigens complex with viral tumors, which was discovered in 1979 following a viral analysis and cancer analog research. Researchers later in the year 1989 explained that in Murine Friend, a virus-caused erythroleukemia, commonly found that p53 was inactivated to suggest that p53 could be a "tumor suppressor gene." The TP53 gene, encoding p53, is one of human cancer's most frequently altered genes. The protein-regulated biological functions of all p53s include cell cycles, apoptosis, senescence, metabolism of the DNA, angiogenesis, cell differentiation, and immunological response. We tried to unfold the history of the p53 protein, which was discovered long back in 1979, that is, 43 years of research on p53, and how p53's function has been developed through time in this article.

Mechanism of apoptosis activation by Curcumin rescued mutant p53Y220C in human pancreatic cancer

The mutant p53Y220C (mutp53Y220C) is frequently observed in numerous tumors, including pancreatic cancer. The mutation creates a crevice in the DNA binding core domain and makes p53 a thermally unstable non-functional protein that assists tumor progression and confers resistance to chemotherapeutic drugs. Restoring mutp53 function to its wild type by selectively targeting this crevice with small molecules is a pivotal strategy to promote apoptosis. In this study, we have shown through different biophysical and cell-based studies that curcumin binds and rescues mutp53Y220C to an active wild-type conformation and restores its apoptotic transcription function in BxPC-3-pancreatic cancer cells. In addition, the curcumin-rescued-p53Y220C (CRp53) showed significant hyperphosphorylation at Ser15, Ser20, and acetylation at Lys382 with an 8-fold increase in transcription activity in the BxPC-3 cell lines. We also observed that the active CRp53 escapes Mdm2-mediated proteasomal degradation and the majority of the proteins were localized inside the nucleus with an increased half-life and transcription restoration compared to untreated BxPC-3 cells. By label-free proteomics analysis, we observed that upon curcumin treatment almost 227 proteins were dysregulated with the majority of them being transcriptional targets of p53. Based on our studies, it reflects that apoptosis in pancreatic cancer cells is mediated by curcumin-rescued mutant p53Y220C.

Accessing isotopically labeled proteins containing genetically encoded phosphoserine for NMR with optimized expression conditions

Phosphoserine (pSer) sites are primarily located within disordered protein regions, making it difficult to experimentally ascertain their effects on protein structure and function. Therefore, the production of 15N- (and 13C)-labeled proteins with site-specifically encoded pSer for NMR studies is essential to uncover molecular mechanisms of protein regulation by phosphorylation. While genetic code expansion technologies for the translational installation of pSer in Escherichia coli are well established and offer a powerful strategy to produce site-specifically phosphorylated proteins, methodologies to adapt them to minimal or isotope-enriched media have not been described. This shortcoming exists because pSer genetic code expansion expression hosts require the genomic ΔserB mutation, which increases pSer bioavailability but also imposes serine auxotrophy, preventing growth in minimal media used for isotopic labeling of recombinant proteins. Here, by testing different media supplements, we restored normal BL21(DE3) ΔserB growth in labeling media but subsequently observed an increase of phosphatase activity and mis-incorporation not typically seen in standard rich media. After rounds of optimization and adaption of a high-density culture protocol, we were able to obtain ≥10 mg/L homogenously labeled, phosphorylated superfolder GFP. To demonstrate the utility of this method, we also produced the intrinsically disordered serine/arginine-rich region of the SARS-CoV-2 Nucleocapsid protein labeled with 15N and pSer at the key site S188 and observed the resulting peak shift due to phosphorylation by 2D and 3D heteronuclear single quantum correlation analyses. We propose this cost-effective methodology will pave the way for more routine access to pSer-enriched proteins for 2D and 3D NMR analyses.

Recent advances in ATM inhibitors as potential therapeutic agents

ATM, a member of the PIKK-like protein family, plays a central role in responding to DNA double-strand breaks and other lesions to protect the genome against DNA damage. Loss of ATM's kinase function has been shown to increase the sensitivity of most cells to ionizing radiation. Therefore, ATM is thought to be a promising target for chemotherapy as a radiotherapy sensitizer. The mechanism of ATM in cancer treatment and the development of its inhibitors have become research hotspots. Here we present an overview of research concerning ATM protein domains, functions and inhibitors, as well as perspectives and insights for future development of ATM-targeting agents.

Inhibition of NADPH Oxidase-ROS Signal using Hyaluronic Acid Nanoparticles for Overcoming Radioresistance in Cancer Therapy

Upregulation of NADPH oxidases (NOXs) in cancer cells leads to chronic increase in intracellular reactive oxygen species (ROS) and adaptation to a high ROS level for cell survival and, thereby, low sensitivity to radiotherapy. To overcome resistance to radiotherapy, we have developed a bioactive and CD44 targeted hyaluronic acid nanoparticle encapsulated with an NOX inhibitor, GKT831 (HANP/GKT831). We found that HANP/GKT831 had stronger inhibitory effects on ROS generation and cell proliferation than that of GKT831 alone in cancer cells. Systemic delivery of HANP/GKT831 led to the targeted accumulation in breast cancer patient derived xenograft (PDX) tumors in nude mice. Importantly, the combination of systemic delivery of HANP/GKT831 with a low dose of local radiotherapy significantly enhanced tumor growth inhibition in breast cancer PDX models. Our results showed that HANP/GKT831 primed tumor cells to radiation-induced DNA damage and cell death by downregulation of DNA repair function and oncogenic signal pathways.

DNA damage response revisited: the p53 family and its regulators provide endless cancer therapy opportunities

Antitumor therapeutic strategies that fundamentally rely on the induction of DNA damage to eradicate and inhibit the growth of cancer cells are integral approaches to cancer therapy. Although DNA-damaging therapies advance the battle with cancer, resistance, and recurrence following treatment are common. Thus, searching for vulnerabilities that facilitate the action of DNA-damaging agents by sensitizing cancer cells is an active research area. Therefore, it is crucial to decipher the detailed molecular events involved in DNA damage responses (DDRs) to DNA-damaging agents in cancer. The tumor suppressor p53 is active at the hub of the DDR. Researchers have identified an increasing number of genes regulated by p53 transcriptional functions that have been shown to be critical direct or indirect mediators of cell fate, cell cycle regulation, and DNA repair. Posttranslational modifications (PTMs) primarily orchestrate and direct the activity of p53 in response to DNA damage. Many molecules mediating PTMs on p53 have been identified. The anticancer potential realized by targeting these molecules has been shown through experiments and clinical trials to sensitize cancer cells to DNA-damaging agents. This review briefly acknowledges the complexity of DDR pathways/networks. We specifically focus on p53 regulators, protein kinases, and E3/E4 ubiquitin ligases and their anticancer potential.

Cellular and Molecular Biological Alterations after Photon, Proton, and Carbon Ions Irradiation in Human Chondrosarcoma Cells Linked with High-Quality Physics Data

Chondrosarcomas are particularly difficult to treat due to their resistance to chemotherapy and radiotherapy. However, particle therapy can enhance local control and patient survival rates. To improve our understanding of the basic cellular radiation response, as a function of dose and linear energy transfer (LET), we developed a novel water phantom-based setup for cell culture experiments and characterized it dosimetrically. In a direct comparison, human chondrosarcoma cell lines were analyzed with regard to their viability, cell proliferation, cell cycle, and DNA repair behavior after irradiation with X-ray, proton, and carbon ions. Our results clearly showed that cell viability and proliferation were inhibited according to the increasing ionization density, i.e., LET, of the irradiation modes. Furthermore, a prominent G2/M arrest was shown. Gene expression profiling proved the upregulation of the senescence genes CDKN1A (p21), CDKN2A (p16NK4a), BMI1, and FOXO4 after particle irradiation. Both proton or C-ion irradiation caused a positive regulation of the repair genes ATM, NBN, ATXR, and XPC, and a highly significant increase in XRCC1/2/3, ERCC1, XPC, and PCNA expression, with C-ions appearing to activate DNA repair mechanisms more effectively. The link between the physical data and the cellular responses is an important contribution to the improvement of the treatment system.

Alternative Lengthening of Telomeres in Cancer Confers a Vulnerability to Reactivation of p53 Function

A subset of cancers across multiple histologies with predominantly poor outcomes use the alternative lengthening of telomeres (ALT) mechanism to maintain telomere length, which can be identified with robust biomarkers. ALT has been reported to be prevalent in high-risk neuroblastoma and certain sarcomas, and ALT cancers are a major clinical challenge that lack targeted therapeutic approaches. Here, we found ALT in a variety of pediatric and adult cancer histologies, including carcinomas. Patient-derived ALT cancer cell lines from neuroblastomas, sarcomas, and carcinomas were hypersensitive to the p53 reactivator eprenetapopt (APR-246) relative to telomerase-positive (TA+) models. Constitutive telomere damage signaling in ALT cells activated ataxia-telangiectasia mutated (ATM) kinase to phosphorylate p53, which resulted in selective ALT sensitivity to APR-246. Treatment with APR-246 combined with irinotecan achieved complete responses in mice xenografted with ALT neuroblastoma, rhabdomyosarcoma, and breast cancer and delayed tumor growth in ALT colon cancer xenografts, while the combination had limited efficacy in TA+ tumor models. A large number of adult and pediatric cancers present with the ALT phenotype, which confers a uniquely high sensitivity to reactivation of p53. These data support clinical evaluation of a combinatorial approach using APR-246 and irinotecan in ALT patients with cancer.

SIGNIFICANCE

This work demonstrates that constitutive activation of ATM in chemotherapy-refractory ALT cancer cells renders them hypersensitive to reactivation of p53 function by APR-246, indicating a potential strategy to overcome therapeutic resistance.

Banp regulates DNA damage response and chromosome segregation during the cell cycle in zebrafish retina

Btg3-associated nuclear protein (Banp) was originally identified as a nuclear matrix-associated region (MAR)-binding protein and it functions as a tumor suppressor. At the molecular level, Banp regulates transcription of metabolic genes via a CGCG-containing motif called the Banp motif. However, its physiological roles in embryonic development are unknown. Here, we report that Banp is indispensable for the DNA damage response and chromosome segregation during mitosis. Zebrafish banp mutants show mitotic cell accumulation and apoptosis in developing retina. We found that DNA replication stress and tp53-dependent DNA damage responses were activated to induce apoptosis in banp mutants, suggesting that Banp is required for regulation of DNA replication and DNA damage repair. Furthermore, consistent with mitotic cell accumulation, chromosome segregation was not smoothly processed from prometaphase to anaphase in banp morphants, leading to a prolonged M-phase. Our RNA- and ATAC-sequencing identified 31 candidates for direct Banp target genes that carry the Banp motif. Interestingly, a DNA replication fork regulator, wrnip1, and two chromosome segregation regulators, cenpt and ncapg, are included in this list. Thus, Banp directly regulates transcription of wrnip1 for recovery from DNA replication stress, and cenpt and ncapg for chromosome segregation during mitosis. Our findings provide the first in vivo evidence that Banp is required for cell-cycle progression and cell survival by regulating DNA damage responses and chromosome segregation during mitosis.

In order for a cell to divide, it must progress through a series of carefully controlled steps known as the cell cycle. First, the cell replicates its DNA and both copies get segregated to opposite ends. The cell then splits into two and each new cell receives a copy of the duplicated genetic material. If any of the stages in the cell cycle become disrupted or mis-regulated this can lead to uncontrolled divisions that may result in cancer.

Researchers have often used a structure within the eye known as the retina to study the cell cycle in zebrafish and other animals as cells in the retina rapidly divide in a highly controlled manner. A protein called Banp is known to help stop tumors from growing in humans and mice, but its normal role in the body, particularly the cell cycle, has remained unclear. To investigate, Babu et al. studied the retina of mutant zebrafish that were unable to make the Banp protein.

The experiments revealed that two stress responses indicating DNA damage or defects in copying DNA were active in the retinal cells of the mutant zebrafish. This suggested that Banp allows cell to progress through the cell cycle by repairing any DNA damage that may arise during replication. Banp does this by activating the gene for another protein called Wrnip1. Babu et al. also found that Banp helps segregate the two copies of DNA during cell division by promoting the activation of two other proteins called Cenpt and Ncapg. Further experiments identified 31 genes that were directly regulated by Banp.

These findings demonstrate that Banp is required for zebrafish cells to be able to accurately copy their DNA and divide in to two new cells. In the future, the work of Babu et al. will provide a useful resource to investigate how tumors grow and spread around the body, and may contribute to the development of new treatments for cancer.

Therapeutic restoring p53 function with small molecule for oncogene-driven non-small cell lung cancer by targeting serine 392 phosphorylation

p53 inactivation by disabling its function is a hallmark in lung carcinomas, emphasizing the significance of restoring p53 function as an attractive therapeutic strategy. However, the clinical efficacy of existing p53 activators is limited due to their inability to effectively activate p53 within the tumors. Here, we established a p53 activator screening assay in EGFR-driven lung cancer cells and identified a small molecular, MX-C4, as a promising candidate. Using high throughput compound screening and combination analyses, we found that MX-C4 effectively promoted the phosphorylation of p53 at serine-392 (s392). It exhibited potent antitumor activity in a variety of cancer cell lines, but only limited toxicity to NCI-H1299 (p53-null) and normal cell lines such as LX2 and HL-7702. Overexpression of p53 in NCI-H1299 cells by a p53 expressing virus vector sensitized cells to MX-C4 treatment, suggesting a p53-dependent anticancer activity. Furthermore, we demonstrated that MX-C4 bound to p53 and exerted its anticancer activity through cell cycle arrest at G2/M phase and apoptosis induction. Mechanistic study indicated that p53 activation regulated cell cycle and cell survival related targets at protein levels. Moreover, p53 activation raised phospho-p53 translocation to mitochondria and subsequently reorganized the Bcl-xl-Bak complex, thus conformationally activating Bak and inducing apoptosis. It is noteworthy that MX-C4 could effectively activate p53 within the tumors in EGFR-driven xenograft models, where tumor was significantly suppressed without obvious toxicity. Our study identified a promising candidate for lung cancer therapy by restoring p53 function.

Shared Genetic Risk Factors Between Cancer and Cardiovascular Diseases

Cancer and cardiovascular diseases (CVD) account for approximately 27.5 million deaths every year. While they share some common environmental risk factors, their shared genetic risk factors are not yet fully understood. The aim of the present study was to aggregate genetic risk factors associated with the comorbidity of cancer and CVDs. For this purpose, we: (1) created a catalog of genes associated with cancer and CVDs, (2) visualized retrieved data as a gene-disease network, and (3) performed a pathway enrichment analysis. We performed screening of PubMed database for literature reporting genetic risk factors in patients with both cancer and CVD. The gene-disease network was visualized using Cytoscape and the enrichment analysis was conducted using Enrichr software. We manually reviewed the 181 articles fitting the search criteria and included 13 articles in the study. Data visualization revealed a highly interconnected network containing a single subnetwork with 56 nodes and 146 edges. Genes in the network with the highest number of disease interactions were JAK2, TTN, TET2, and ATM. The pathway enrichment analysis revealed that genes included in the study were significantly enriched in DNA damage repair (DDR) pathways, such as homologous recombination. The role of DDR mechanisms in the development of CVDs has been studied in previously published research; however, additional functional studies are required to elucidate their contribution to the pathophysiology to CVDs.

The role of p53 in the DNA damage-related ubiquitylation of S2P RNAPII

DNA double-strand breaks are one of the most deleterious lesions for the cells, therefore understanding the macromolecular interactions of the DNA repair-related mechanisms is essential. DNA damage triggers transcription silencing at the damage site, leading to the removal of the elongating RNA polymerase II (S2P RNAPII) from this locus, which provides accessibility for the repair factors to the lesion. We previously demonstrated that following transcription block, p53 plays a pivotal role in transcription elongation by interacting with S2P RNAPII. In the current study, we reveal that p53 is involved in the fine-tune regulation of S2P RNAPII ubiquitylation. Furthermore, we emphasize the potential role of p53 in delaying the premature ubiquitylation and the subsequent chromatin removal of S2P RNAPII as a response to transcription block.

The Role of E3 Ligase Pirh2 in Disease

The p53-dependent ubiquitin ligase Pirh2 regulates a number of proteins involved in different cancer-associated processes. Targeting the p53 family proteins, Chk2, p27Kip1, Twist1 and others, Pirh2 participates in such cellular processes as proliferation, cell cycle regulation, apoptosis and cellular migration. Thus, it is not surprising that Pirh2 takes part in the initiation and progression of different diseases and pathologies including but not limited to cancer. In this review, we aimed to summarize the available data on Pirh2 regulation, its protein targets and its role in various diseases and pathological processes, thus making the Pirh2 protein a promising therapeutic target.

PTEN mutant non-small cell lung cancer require ATM to suppress pro-apoptotic signalling and evade radiotherapy

Background

Despite advances in treatment of patients with non-small cell lung cancer, carriers of certain genetic alterations are prone to failure. One such factor frequently mutated, is the tumor suppressor PTEN. These tumors are supposed to be more resistant to radiation, chemo- and immunotherapy.

Results

We demonstrate that loss of PTEN led to altered expression of transcriptional programs which directly regulate therapy resistance, resulting in establishment of radiation resistance. While PTEN-deficient tumor cells were not dependent on DNA-PK for IR resistance nor activated ATR during IR, they showed a significant dependence for the DNA damage kinase ATM. Pharmacologic inhibition of ATM, via KU-60019 and AZD1390 at non-toxic doses, restored and even synergized with IR in PTEN-deficient human and murine NSCLC cells as well in a multicellular organotypic ex vivo tumor model.

Conclusion

PTEN tumors are addicted to ATM to detect and repair radiation induced DNA damage. This creates an exploitable bottleneck. At least in cellulo and ex vivo we show that low concentration of ATM inhibitor is able to synergise with IR to treat PTEN-deficient tumors in genetically well-defined IR resistant lung cancer models.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00778-7.