Ataxia Telangiectasia Mutated Research Articles

Uncovering the clinical relevance of unclassified variants in DNA repair genes: a focus on BRCA negative Tunisian cancer families.

Introduction: Recent advances in sequencing technologies have significantly increased our capability to acquire large amounts of genetic data. However, the clinical relevance of the generated data continues to be challenging particularly with the identification of Variants of Uncertain Significance (VUSs) whose pathogenicity remains unclear. In the current report, we aim to evaluate the clinical relevance and the pathogenicity of VUSs in DNA repair genes among Tunisian breast cancer families. Methods: A total of 67 unsolved breast cancer cases have been investigated. The pathogenicity of VUSs identified within 26 DNA repair genes was assessed using different in silico prediction tools including SIFT, PolyPhen2, Align-GVGD and VarSEAK. Effects on the 3D structure were evaluated using the stability predictor DynaMut and molecular dynamics simulation with NAMD. Family segregation analysis was also performed. Results: Among a total of 37 VUSs identified, 11 variants are likely deleterious affecting ATM, BLM, CHEK2, ERCC3, FANCC, FANCG, MSH2, PMS2 and RAD50 genes. The BLM variant, c.3254dupT, is novel and seems to be associated with increased risk of breast, endometrial and colon cancer. Moreover, c.6115G>A in ATM and c.592+3A>T in CHEK2 were of keen interest identified in families with multiple breast cancer cases and their familial cosegregation with disease has been also confirmed. In addition, functional in silico analyses revealed that the ATM variant may lead to protein immobilization and rigidification thus decreasing its activity. We have also shown that FANCC and FANCG variants may lead to protein destabilization and alteration of the structure compactness which may affect FANCC and FANCG protein activity. Conclusion: Our findings revealed that VUSs in DNA repair genes might be associated with increased cancer risk and highlight the need for variant reclassification for better disease management. This will help to improve the genetic diagnosis and therapeutic strategies of cancer patients not only in Tunisia but also in neighboring countries.

Abstract A077: The EZH2 epigenetic factor orchestrates oncogenic properties in ATM-deficient pancreatic cancer

Abstract Despite decades of extensive basic and translational research improving our understanding of pancreatic ductal adenocarcinoma (PDAC), its complex biology remains a significant challenge and limits overcoming its dismal prognosis. Due to its resistance to conventional therapies and heterogeneous mutational landscape, molecular stratification and the development of targeted therapeutic options are essential for improving survival of PDAC patients. Previous work from our group investigated loss-of-function mouse models for the serine/threonine kinase ATM causing homologous recombination deficiency (HRD) in PDAC. Specifically, ATM loss caused certain oncogenic features in the arising tumors, including the acquisition of an invasive phenotype along with the emergence of a prominent desmoplastic reaction, but also sensitizes toward platinum-based therapies and PARP1 inhibition (Russell, Nat Commun; Perkhofer, Cancer Res; Gout, Gut). However, the mechanisms orchestrating these oncogenic features remain unclear. Here, we identified the histone-methyltransferase EZH2 as a direct ATM substrate to operate as an epithelial-mesenchymal gatekeeper. In detail, ATM-deficient tumors accumulated EZH2, suggesting that ATM status contributes to rewiring the epigenetic landscape of pancreatic tumors, subsequently supporting oncogenic features. To investigate whether and how EZH2 impacts ATM-deficient PDAC pathogenesis, we generated conditional double ATM and EZH2-knockout in the KrasG12D/+; Ptf1aCre/+ mice. Double-null mice showed extended mouse survival, reduced metastasis burden, and decreased undifferentiated malignant cell features. Interestingly, both in vivo and in vitro investigations revealed that ATM status significantly impacts EZH2 activity via a post-translational regulation axis. Specifically, the ATM kinase activity was critical to promote Culin1 E3-ubiquitin ligase recruitment and subsequent EZH2 ubiquitination and degradation. Finally, we demonstrated that a combinatorial therapy involving a potent EZH2 inhibitor promotes genomic instability and exacerbates the cytotoxic effects of PARP interference in ATM-deficient HRD PDAC. Overall, our study demonstrates that ATM deficiency significantly impacts EZH2 epigenetic functions and pinpoints the molecular stratification according to ATM status prior to pharmacological EZH2 interference in PDAC therapies as a valuable approach to target ATM-deficient HRD tumors. Citation Format: Elodie Roger, Anna Härle, Johann Gout, Lukas Perkhofer, Elisabeth Hessmann, Alexander Kleger. The EZH2 epigenetic factor orchestrates oncogenic properties in ATM-deficient pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A077.

Abstract A012: The Spanish Familial Pancreatic Cancer Registry (PANGENFAM): Genetic testing and follow-up of high risk individuals

Abstract Introduction: The Spanish familial pancreatic cancer registry (PANGENFAM) was established in 2009, with the main objective to study the genetic and phenotypic characteristics of familial pancreatic cancer families and offer screening of high-risk individuals for early detection. Methods: Targeted panel and exome sequencing of 52 FPC and 33 sporadic PDAC cases was performed to identify genes and novel variants related to PDAC risk. Healthy high-risk relatives of FPC cases enter into a screening that consists of an annual MRI, echo-endoscopy and routine blood tests, which is followed by a biopsy if a suspicious lesion is identified. Results: The registry and associated biobank is maintained thanks to a stable collaboration between the departments of Medical Oncology, Gastroenterology, Radiology General Surgery and Pathology. The registry currently includes over 150 families and 350 individuals, including PDAC cases and high risk individuals. Targeted sequencing analysis of DNA repair genes involved in familial cancer identified pathogenic variants in 7.5% of FPC cases in the MLH1 and CDKN2A genes, likely pathogenic variants were found in 5.7% of cases in the genes MUTYH, TERT and ATM. Likely pathogenic variants were found in 9.4% of sporadic cases in the genes POLQ, CHEK2 and FANCM and no pathogenic variants were identified. By exome sequencing, missense variants with a damaging effect were found in 11 FPC cases, including stop gain, stop loss or frameshift variants in 5 FPC cases (45.45%), affecting WWOX, C2orf83, CYP3A5 and TANGO2. KRAS somatic mutations in codon 12 and 13 were more frequently detected in sporadic PDAC cases (70%) compared to familial cases (16%) via the liquid biopsy. Interestingly, the median overall survival for sporadic and familial PDAC cases in our cohort was 10.2 vs. 21.7 months (p⇒0.01), respectively, even when adjusted for stage at diagnosis and first line adjuvant therapy. From all the families included in the registry, 185 were offered the high-risk screening program for early detection. Currently 129 individuals are actively participating in the screening program, of which, 72% of these individuals have a non-normal looking pancreas via MRI or EUS. The most commonly detected lesions were cysts and IPMN found in 32% and 12% individuals, respectively. Screening has successfully detected and treated solid lesions in 4 high-risk individuals, including 3 early PDAC and 1 neuroendocrine tumor. An additional 11 individuals with lesions with worrisome features are under close follow-up. Conclusions: Panel sequencing has identified pathogenic variants in known familial cancer genes that are also associated with FPC risk. Exome sequencing in panel negative FPC cases has identified novel risk associated genes. The molecular and clinical profile of FPC and sporadic cases are distinct which should be taken into account in the clinic. Citation Format: Emma Melian, Ana García García de Paredes, Mercedes Rodríguez, Jorge Villalón López, María Muñoz, Javier Blaquez, Ignacio Ruz, Alfonso Sanjuanbenito, Eduardo Lobo, Victoria Lopéz, Carmen Guillen Ponce, José Ramón Foruny Olcina, Sergio López Durán, Alfredo Carrato, Julie Earl. The Spanish Familial Pancreatic Cancer Registry (PANGENFAM): Genetic testing and follow-up of high risk individuals [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A012.

Abstract B001: Identification of monoallelic ATM loss-of-function and homologous recombination deficiency (HRD) in high-grade ovarian tumor with prolonged response to camonsertib and low-dose gemcitabine combination therapy

Abstract Intra-tumor heterogeneity and the prevalent loss-of-function mutations within DNA damage repair (DDR) genes constitute salient hallmarks of high-grade ovarian malignancies. However, the etiological drivers beyond BRCA1/2 mutations, as well as the chronology of tumor evolutionary processes, remain enigmatic. Here, we present the case of a 60-year-old female with high-grade serous ovarian cancer, initially treated with primary debulking surgery followed by 6 cycles of adjuvant intraperitoneal cisplatin and paclitaxel. After a 16-month platinum-free interval, the patient (pt) developed recurrent disease and subsequently received 5 weeks of neoadjuvant olaparib followed by secondary debulking surgery and adjuvant carboplatin as part of a clinical trial (NCT02489006). The pt became platinum refractory after 4 cycles of carboplatin, then received weekly paclitaxel and biweekly bevacizumab with stable disease as best response and eventual progression after 17 cycles. Molecular profiling of the metastatic biopsies at the time of initial recurrence identified a pathogenic ATM (c.4910-1G>A) alteration for which the pt was then enrolled onto the Phase Ib TRESR trial (NCT04497116). The trial enrolled pts ≥18 years, ECOG PS 0-1, with advanced solid tumors with deleterious DDR alterations. The pt received a starting dose of 1000mg/m2 gemcitabine (gem) with 80mg of the ATR inhibitor camonsertib (cam; 3 days [d] on/4d off) on a 21d cycle (2 weeks [w] on/2w off). The pt had a partial RECIST 1.1 response at 4 months (mo) and remains on treatment after 18mo. Due to toxicities (primarily neutropenia) the pt had a series of dose reductions to 200mg/m2 gem with 50mg cam (2d on/5d off) on a 28d cycle (1w on/1w off). Circulating tumor fraction (TF), measured by methylation-based profiling, remained at or below the limit of quantitation of the assay through 11mo (0.01% TF, testing of later timepoints ongoing). At 13mo, the target lesions began increasing in size (-50% to -43%) prompting a dose increase of cam to 80mg (same gem dose), after which the target lesions decreased to nadir (-52%) at 76w with concomitant CA-125 decrease. Retrospective whole-genome sequencing (WGS) of the secondary debulking surgery specimen as well as targeted sequencing (SyNthetic lethal Interactions for Precision Diagnostics [SNiPDx]) and immunohistochemistry of the metastatic biopsy revealed ATM protein loss only in a portion of the tumor and a monoallelic ATM mutation. Genomic signature analysis of WGS indicated presence of single-base substitution signatures 3+8 (HRD-related) and HRD positivity (BRCA1-type; CHORD algorithm). In contrast, while HRD+ was also detected in the primary tumor sample, the ATM alteration was absent and ATM protein expression was uniform, suggesting that ATM loss was a late event in tumor evolution. This case highlights the complexity of intra-tumor heterogeneity and clonal evolution in ovarian tumors and importance of “functional” HRD as no apparent mutational driver was identified. Citation Format: Stephanie Lheureux, Joseph D. Schonhoft, Ian M. Silverman, Julia Yang, Adrienne Johnson, Brooke Grant, Alexander Fortuna, Trevor J. Pugh, Parham Nejad, Bernard Lam, Sahaj Arora, Ashley Adile, Stephenie D. Prokopec, Jeffrey Bruce, Danielle Ulanet, Maria Koehler, Ezra Rosen, Victoria Rimkunas. Identification of monoallelic ATM loss-of-function and homologous recombination deficiency (HRD) in high-grade ovarian tumor with prolonged response to camonsertib and low-dose gemcitabine combination therapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr B001.

Genetic predisposition to differentiated thyroid cancer in the Polish population.

Genome sequencing technologies reveal molecular mechanisms of differentiated thyroid cancer (DTC). Unlike somatic mutation analysis from thyroidectomy samples, germline mutations showing genetic susceptibility to DTC are less understood. The study aimed to assess the prevalence of germline mutations predisposing to DTC in a cohort of Polish individuals based on their whole genome sequencing data. We analyzed sequencing data from 1076 unrelated individuals totaling over 1018 billion read pairs and yielding an average 35.26 × read depth per genome, released openly for academic and clinical research as the Thousand Polish Genomes database (https://1000polishgenomes.com). The list of genes chosen for further analysis was based on the review of previous studies. The cohort contained 104 variants located within the coding and noncoding DNA sequences of 90 genes selected by ClinVar classification as pathogenic and potentially pathogenic. The frequency of variants in the Polish cohort was compared with the frequency estimated for the non‑Finnish European population obtained from the gnomAD database (gnomad.broadinstitute.org). Significant differences in variant frequency were found for the APC, ARSB, ATM, BRCA1, CHEK2, DICER1, GPD1L, INSR, KCNJ10, MYH9, PALB2, PLCB1, PLEKHG5, PTEN, RET, SEC23B, SERPINA1, SLC26A4, SMAD3, STK11, TERT, TOE1, and WRN genes. Even though the Polish population is genetically similar to the other European populations, there are significant differences in variant frequencies contributing to the disease development and progression, such as those in the RET, CHEK2, BRCA1, SLC26A4, or TERT genes. Further studies are needed to identify genomic variants associated directly with DTC.

Genetic and prognostic analysis of blastoid and pleomorphic mantle cell lymphoma: a multicenter analysis in China.

Blastoid or pleomorphic mantle cell lymphoma (B/P-MCL) is characterized by high invasiveness and unfavorable outcomes, which is still a challenge for treating MCL. This retrospective study was performed to comprehensively analyze the clinical, genomic characteristics and treatment options of patients with B/PMCL from multicenter in China. Data were obtained from 693 patients with B/PMCL from three centers in China between April 1999 and December 2019. Seventy-four patients with BMCL (n = 43) or PMCL (n = 31) were included in the analysis. The median age of the cohort was 60.0years with a male-to-female ratio of 2.89:1. The 3-year progression-free survival (PFS) and overall survival (OS) rates were 44.1% and 46.0%, respectively. Mutations of TP53, ATM, NOTCH1, NOTCH2, NSD2, SMARCA4, CREBBP, KMT2D, FAT1, and TRAF2 genes were the most common genetic changes in B/P-MCL. Progression of disease within 12months (POD12) could independently predict the poor prognosis of patients with blastoid and pleomorphic variants. Patients with POD12 carried a distinct mutation profile (TP53, SMARCA4, NSD2, NOTCH2, KMT2D, PTPRD, CREBBP, and CDKN2A mutations) compared to patients with non-POD12. First-line high-dose cytosine arabinoside exposure obtained survival benefits in these populations, and BTKi combination therapy as the front-line treatment had somewhat improvement in survival with no significant difference in the statistic. In conclusion, B/P-MCL had inferior outcomes and a distinct genomic profile. Patients with POD12 displayed a distinct mutation profile and a poor prognosis. New therapeutic drugs and clinical trials for B/P-MCL need to be further explored.

Alantolactone Induced Apoptosis and DNA Damage of Cervical Cancer through ATM/CHK2 Signaling Pathway.

Traditional Chinese Medicine, known for its minimal side effects and significant clinical efficacy, has attracted considerable interest for its potential in cancer therapy. In particular, Inula helenium L. has demonstrated effectiveness in inhibiting a variety of cancers. This study focuses on alantolactone (ALT), a prominent compound from Inula helenium L., recognized for its anti-cancer capabilities across multiple cancer types. The primary objective of this study is to examine the influence of ALT on the proliferation, apoptosis, cell cycle, and tumor growth of cervical cancer (CC) cells, along with its associated signaling pathways. To determine protein expression alterations, Western blot analysis was conducted. Furthermore, an in vivo model was created by subcutaneously injecting HeLa cells into nude mice to assess the impact of ALT on cervical cancer. Our research thoroughly investigates the anti-tumor potential of ALT in the context of CC. ALT was found to inhibit cell proliferation and induce apoptosis in SiHa and HeLa cell lines, particularly targeting ataxia-telangiectasia mutated (ATM) proteins associated with DNA damage. The suppression of DNA damage and apoptosis induction when ATM was inhibited underscores the crucial role of the ATM/cell cycle checkpoint kinase 2 (CHK2) axis in ALT's anti-tumor effects. In vivo studies with a xenograft mouse model further validated ALT's effectiveness in reducing CC tumor growth and promoting apoptosis. This study offers new insights into how ALT combats CC, highlighting its promise as an effective anti-cervical cancer agent and providing hope for improved treatment outcomes for CC patients.

Advancing cancer therapy: new frontiers in targeting DNA damage response.

Genomic instability is a core characteristic of cancer, often stemming from defects in DNA damage response (DDR) or increased replication stress. DDR defects can lead to significant genetic alterations, including changes in gene copy numbers, gene rearrangements, and mutations, which accumulate over time and drive the clonal evolution of cancer cells. However, these vulnerabilities also present opportunities for targeted therapies that exploit DDR deficiencies, potentially improving treatment efficacy and patient outcomes. The development of PARP inhibitors like Olaparib has significantly improved the treatment of cancers with DDR defects (e.g., BRCA1 or BRCA2 mutations) based on synthetic lethality. This achievement has spurred further research into identifying additional therapeutic targets within the DDR pathway. Recent progress includes the development of inhibitors targeting other key DDR components such as DNA-PK, ATM, ATR, Chk1, Chk2, and Wee1 kinases. Current research is focused on optimizing these therapies by developing predictive biomarkers for treatment response, analyzing mechanisms of resistance (both intrinsic and acquired), and exploring the potential for combining DDR-targeted therapies with chemotherapy, radiotherapy, and immunotherapy. This article provides an overview of the latest advancements in targeted anti-tumor therapies based on DDR and their implications for future cancer treatment strategies.

The Chromosome Passenger Complex (CPC) Components and Its Associated Pathways Are Promising Candidates to Differentiate Between Normosensitive and Radiosensitive ATM-Mutated Cells

Background: Sensitivity to ionizing radiation differs between individuals, but there is a limited understanding of the biological mechanisms that account for these variations. One example of such mechanisms are the mutations in the ATM (mutated ataxia telangiectasia) gene, that cause the rare recessively inherited disease Ataxia telangiectasia (AT). Hallmark features include chromosomal instability and increased sensitivity to ionizing radiation (IR). Objectives: To deepen the molecular understanding of radiosensitivity and to identify potential new markers to predict it, human ATM-mutated and proficient cells were compared on a proteomic level. Design: In this study, we analyzed 3 cell lines from AT patients, with varying radiosensitivity, and 2 cell lines from healthy volunteers, 24 hours and 72 hours post-10 Gy irradiation Methods: We used label-free mass spectrometry to identify differences in signaling pathways after irradiation in normal and radiosensitive individuals. Cell viability was initially determined by water soluble tetrazolium (WST) assay and DNA damage response was analyzed with 53BP1 repair foci formation along with KRAB-associated protein 1 (KAP1) phosphorylation. Results: Proteomic analysis identified 4028 proteins, which were used in subsequent in silico pathway enrichment analysis to predict affected biological pathways post-IR. In AT cells, networks were heterogeneous at both time points with no common pathway identified. Mitotic cell cycle progress was the most prominent pathway altered after IR in cells from healthy donors. In particular, components of the chromosome passenger complex (INCENP and CDCA8) were significantly downregulated after 72 hours. This could also be verified at the mRNA level. Conclusion: Altogether, the most striking result was that proteins forming the chromosome passenger complex were downregulated after radiation exposure in healthy normosensitive control cells, but not in radiosensitive ATM-deficient cells. Thus, mitosis-associated proteins form an interesting compound to gain insights into the development and prediction of radiosensitivity.

Molecular docking study of frequently used food additives for selected targets depending on the chromosomal abnormalities they cause

Food additives (FAs) (flavor enhancers, sweeteners, etc.) protect foods during storage and transportation, making them attractive to consumers. Today, while the desire to access natural foods is increasing, the chemicals added to foods have started to be questioned. In this respect, genotoxicity tests have gained importance. Studies show that some food additives may have genotoxic risks. Previous studies carried out in our laboratory also revealed genotoxic effects of Monopotassium glutamate (MPG), Monosodium glutamate (MSG), Magnesium diglutamate (MDG) as flavor enhancers; Potassium benzoate (PB), Potassium sorbate (PS), Sodium benzoate (SB), Sodium sorbate (SS) as preservatives; Acesulfame potassium (ACE-K), Xylitol (XYL) as sweeteners. In this study, we determined the interactions of these food additives with ATM and p53 proteins, which are activated in the cell due to genotoxic effects, and with DNA by employing the molecular docking method for the first time. Among the food additives, SB (−4.307) for ATM, XYL (−4.629) for p53, and XYL (−4.927) for DNA showed the highest affinity. Therefore, flexible docking (IFD) scores were determined for SB, XYL, and MDG from flavor enhancers. The potential binding modes of the food additives to target molecules' possible inhibition mechanisms were determined by molecular docking. Thus, new information was obtained to show how these additives cause chromosomal abnormalities.

PIM Kinase Inhibition Attenuates the Malignant Progression of Metastatic Hepatoblastoma.

Hepatoblastoma is the most common primary pediatric liver tumor. Children with pulmonary metastases at diagnosis experience survival rates as low as 25%. We have shown PIM kinases play a role in hepatoblastoma tumorigenesis. In this study, we assessed the role of PIM kinases in metastatic hepatoblastoma. We employed the metastatic hepatoblastoma cell line, HLM_2. PIM kinase inhibition was attained using PIM3 siRNA and the pan-PIM inhibitor, AZD1208. Effects of PIM inhibition on proliferation were evaluated via growth curve. Flow cytometry determined changes in cell cycle. AlamarBlue assay assessed effects of PIM kinase inhibition and cisplatin treatment on viability. The lethal dose 50% (LD50) of each drug and combination indices (CI) were calculated and isobolograms constructed to determine synergy. PIM kinase inhibition resulted in decreased HLM_2 proliferation, likely through cell cycle arrest mediated by p21. Combination therapy with AZD1208 and cisplatin resulted in synergy, potentially through downregulation of the ataxia-telangiectasia mutated (ATM) kinase DNA damage response pathway. When assessing the combined effects of pharmacologic PIM kinase inhibition with cisplatin on HLM_2 cells, we found the agents to be synergistic, potentially through inhibition of the ATM pathway. These findings support further exploration of PIM kinase inhibition as a therapeutic strategy for metastatic hepatoblastoma.

Effect of bisphosphonates and statins on the in vitro radiosensitivity of breast cancer cell lines.

Early-stage breast cancer is usually treated with breast-conserving surgery followed by adjuvant radiation therapy. Acute skin toxicity is a common radiation-induced side effect experienced by many patients. Recently, a combination of bisphosphonates (zoledronic acid) and statins (pravastatin), or ZOPRA, was shown to radio-protect normal tissues by enhancing DNA double-strand breaks (DSB) repair mechanism. However, there are no studies assessing the effect of ZOPRA on cancerous cells. The purpose of this study is to characterize the in vitro effect of the zoledronic acid (ZO), pravastatin (PRA), and ZOPRA treatment on the molecular and cellular radiosensitivity of breast cancer cell lines. Two breast cancer cell lines, MDA MB 231 and MCF-7, were tested. Cells were treated with different concentrations of pravastatin (PRA), zoledronate (ZO), as well as their ZOPRA combination, before irradiation. Anti-γH2AX and anti-pATM immunofluorescence were performed to study DNA DSB repair kinetics. MTT assay was performed to assess cell proliferation and viability, and flow cytometry was performed to analyze the effect of the drugs on the cell cycle distribution. The clonogenic assay was used to assess cell survival. ZO, PRA, and ZOPRA treatments were shown to increase the residual number of γH2AX foci for both cell lines. ZOPRA treatment was also shown to reduce the activity of the ATM kinase in MCF-7. ZOPRA induced a significant decrease in cell survival for both cell lines. Our findings show that pretreatment with ZOPRA can decrease the radioresistance of breast cancer cells at the molecular and cellular levels. The fact that ZOPRA was previously shown to radioprotect normal tissues, makes it a good candidate to become a therapeutic window-widening drug.

Atypical Ataxia-Telangiectasia with Cervical Dystonia: A Case Report

Ataxia telangiectasia is a rare autosomal recessive neurodegenerative disorder. A minority of patients can present with lateonset atypical manifestations due to unknown mechanisms. This can lead to uncommon signs and symptoms, such as dystonic head movements. We report a 26-year-old woman with atypical ataxia telangiectasia who presented with cervical dystonia. Alpha-fetoprotein levels in the serum were found to be elevated in laboratory tests, and genetic testing for the ATM gene provided the definitive diagnosis.

Abrogation of the G2/M checkpoint as a chemosensitization approach for alkylating agents.

The cell cycle is tightly regulated by checkpoints, which play a vital role in controlling its progression and timing. Cancer cells exploit the G2/M checkpoint, which serves as a resistance mechanism against genotoxic anticancer treatments, allowing for DNA repair prior to cell division. Manipulating cell cycle timing has emerged as a potential strategy to augment the effectiveness of DNA damage-based therapies. In this study, we conducted a forward genome-wide CRISPR/Cas9 screening with repeated exposure to the alkylating agent temozolomide (TMZ) to investigate the mechanisms underlying tumor cell survival under genotoxic stress. Our findings revealed that canonical DNA repair pathways, including the Ataxia-telangiectasia mutated (ATM)/Fanconi and mismatch repair, determine cell fate under genotoxic stress. Notably, we identified the critical role of PKMYT1, in ensuring cell survival. Depletion of PKMYT1 led to overwhelming TMZ-induced cytotoxicity in cancer cells. Isobologram analysis demonstrated potent drug synergy between alkylating agents and a Myt1 kinase inhibitor, RP-6306. Mechanistically, inhibiting Myt1 forced G2/M-arrested cells into an unscheduled transition to the mitotic phase without complete resolution of DNA damage. This forced entry into mitosis, along with persistent DNA damage, resulted in severe mitotic abnormalities. Ultimately, these aberrations led to mitotic exit with substantial apoptosis. Preclinical animal studies demonstrated that the combination regimen involving TMZ and RP-6306 prolonged the overall survival of glioma-bearing mice. Collectively, our findings highlight the potential of targeting cell cycle timing through Myt1 inhibition as an effective strategy to enhance the efficacy of current standard cancer therapies, potentially leading to improved disease outcomes.

Antioxidants and azd0156 Rescue Inflammatory Response in Autophagy-Impaired Macrophages.

Autophagy is a lysosomal degradation system that eliminates and recycles damaged intracellular organelles and proteins. Inflammatory macrophages play a critical role in the development of various age-related inflammatory illnesses such as abdominal aortic aneurysm, atherosclerosis, and rheumatoid arthritis; therefore, identifying the mechanisms that cause macrophage inflammation is crucial for a better understanding of and developing therapeutics for inflammatory diseases. Previous research has linked autophagy to macrophage inflammation; Atg16L1-deficient macrophages increase IL-1 and IL-18 production via inflammasome activation. In this study, however, we show an alternative pathway of macrophage inflammation in an autophagy-deficient environment. We found that inhibiting autophagy in THP1 macrophages progressively increased the expression of p65-mediated inflammatory genes. This effect was reversed by treatment with antioxidants or azd0156, an ataxia telangiectasia mutated (ATM) inhibitor. In addition, our results showed that M1 macrophages inhibit autophagy and induce DNA damage, whereas M2 macrophages activate autophagy and reduce DNA damage. Importantly, the chemical activation of autophagy or ATM inhibition during M1 polarization reduced the M1 phenotype and inflammation, whereas inhibiting autophagy during M2 polarization also reduced the M2 phenotype. Thus, our findings highlight the importance of the autophagy-ATM pathway in driving macrophage inflammation.

Investigations of the novel checkpoint kinase 1 inhibitor SRA737 in non-small cell lung cancer and colorectal cancer cells of differing tumour protein 53 gene status

Aim: In response to DNA damage the serine/threonine-specific protein kinase checkpoint kinase 1 (CHK1) is activated allowing cells to enter S phase (S) and G2 phase (G2) cell-cycle arrest. CHK1 inhibitors are expected to prevent cells from entering such arrest, thereby enhancing DNA damage-induced cytotoxicity. In contrast, normal cells with intact ataxia–telangiectasia mutated (ATM), CHK2 and tumour suppressor protein 53 (P53) signalling are still able to enter cell-cycle arrest using the functioning G1/S checkpoint, thereby being rescued from enhanced cytotoxicity. The main objective of this work is to investigate the in vitro effects of the novel CHK1 inhibitor SRA737 on pairs of non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) cell lines, all with genetic aberrations rendering them susceptible to replication stress but of differing tumour protein 53 (TP53) gene status, focusing on DNA damage induction and the subsequent effects on cell proliferation and viability. Methods: NSCLC cell lines H23 [TP53 mutant (MUT)] and A549 [TP53 wild-type (WT)] and CRC cell lines HT29 (TP53 MUT) and HCT116 (TP53 WT) were incubated with differing micromolar concentrations of SRA737 for 24 h and then analysed using alkaline comet and phosphorylated H2A.X variant histone (γH2AX)-foci assays to assess mostly DNA single strand break and double strand break damage, respectively. Cell-counting/trypan blue staining was also performed to assess cell proliferation/viability. Results: Clear concentration-dependent increases in comet formation and γH2AX-foci/cell were noted for the TP53 MUT cells with no or lower increases being noted in the corresponding TP53 WT cells. Also, greater anti-proliferative and cell killing effects were noted in the TP53 MUT cells than in the TP53 WT cells. Conclusions: This study’s data suggests that P53 status/functioning is a key factor in determining the sensitivity of NSCLC and CRC cancer cells towards CHK1 inhibition, even in circumstances conducive to high replicative stress.

Disordered regions mediate the interaction of p53 and MRE11

The genome is frequently targeted by genotoxic agents, resulting in the formation of DNA scars. However, cells employ diverse repair mechanisms to restore DNA integrity. Among these processes, the Mre11-Rad50-Nbs1 complex detects double-strand breaks (DSBs) and recruits DNA damage response proteins such as ataxia-telangiectasia-mutated (ATM) kinase to DNA damage sites. ATM phosphorylates the transactivation domain (TAD) of the p53 tumor suppressor, which in turn regulates DNA repair, growth arrest, apoptosis, and senescence following DNA damage. The disordered glycine-arginine-rich (GAR) domain of double-strand break protein MRE11 (MRE11GAR) and its methylation are important for DSB repair, and localization to Promyelocytic leukemia nuclear bodies (PML-NBs). There is preliminary evidence that p53, PML protein, and MRE11 might co-localize and interact at DSB sites. To uncover the molecular details of these interactions, we aimed to identify the domains mediating the p53-MRE11 interaction and to elucidate the regulation of the p53-MRE11 interaction by post-translational modifications (PTMs) through a combination of biophysical techniques. We discovered that, in vitro, p53 binds directly to MRE11GAR mainly through p53TAD2 and that phosphorylation further enhances this interaction. Furthermore, we found that MRE11GAR methylation still allows for binding to p53. Overall, we demonstrated that p53 and MRE11 interaction is facilitated by disordered regions. We provide for the first time insight into the molecular details of the p53-MRE11 complex formation and elucidate potential regulatory mechanisms that will promote our understanding of the DNA damage response. Our findings suggest that PTMs regulate the p53-MRE11 interaction and subsequently their colocalization to PML-NBs upon DNA damage.

Absolute quantification of DNA damage response proteins

BackgroundDNA damage response (DDR) and repair are vital for safeguarding genetic information and ensuring the survival and accurate transmission of genetic material. DNA damage, such as DNA double-strand breaks (DSBs), triggers a response where sensor proteins recognize DSBs. Information is transmitted to kinases, initiating a sequence resulting in the activation of the DNA damage response and recruitment of other DDR and repair proteins to the DSB site in a highly orderly sequence. Research has traditionally focused on individual protein functions and their order, with limited quantitative analysis, prompting this study’s attempt at absolute quantification of DNA damage response and repair proteins and capturing changes in protein chromatin affinity after DNA damage through biochemical fractionation methods.ResultsTo assess the intracellular levels of proteins involved in DDR and repair, multiple proteins associated with different functions were quantified in EPC2-hTERT cells. H2AX had the highest intracellular abundance (1.93 × 106 molecules/cell). The components of the MRN complex were present at the comparable levels: 6.89 × 104 (MRE11), 2.17 × 104 (RAD50), and 2.35 × 104 (NBS1) molecules/cell. MDC1 was present at 1.27 × 104 molecules/cell. The intracellular levels of ATM and ATR kinases were relatively low: 555 and 4860 molecules/cell, respectively. The levels of cellular proteins involved in NHEJ (53BP1: 3.03 × 104; XRCC5: 2.62 × 104; XRCC6: 5.05 × 105 molecules/cell) were more than an order of magnitude higher than that involved in HR (RAD51: 2500 molecules/cell). Furthermore, we analyzed the dynamics of MDC1 and γH2AX proteins in response to DNA damage induced by the unstable agent neocarzinostatin (NCS). Using cell biochemical fractionation, cells were collected and analyzed at different time points after NCS exposure. Results showed that γH2AX in chromatin fraction peaked at 1 h post-exposure and gradually decreased, while MDC1 translocated from the isotonic to the hypertonic fraction, peaking at 1 hour as well. The study suggests increased MDC1 affinity for chromatin through binding to γH2AX induced by DNA damage. The γH2AX-bound MDC1 (in the hypertonic fraction) to γH2AX ratio at 1 h post-exposure was 1:56.4, with lower MDC1 levels which may attributed to competition with other proteins.ConclusionsThe approach provided quantitative insights into protein dynamics in DNA damage response.

DNA Copy Number Alterations and Copy Neutral Loss of Heterozygosity in Adult Ph-Negative Acute B-Lymphoblastic Leukemia: Focus on the Genes Involved.

The landscape of chromosomal aberrations in the tumor cells of the patients with B-ALL is diverse and can influence the outcome of the disease. Molecular karyotyping at the onset of the disease using chromosomal microarray (CMA) is advisable to identify additional molecular factors associated with the prognosis of the disease. Molecular karyotyping data for 36 patients with Ph-negative B-ALL who received therapy according to the ALL-2016 protocol are presented. We analyzed copy number alterations and their prognostic significance for CDKN2A/B, DMRTA, DOCK8, TP53, SMARCA2, PAX5, XPA, FOXE1, HEMGN, USP45, RUNX1, NF1, IGF2BP1, ERG, TMPRSS2, CRLF2, FGFR3, FLNB, IKZF1, RUNX2, ARID1B, CIP2A, PIK3CA, ATM, RB1, BIRC3, MYC, IKZF3, ETV6, ZNF384, PTPRJ, CCL20, PAX3, MTCH2, TCF3, IKZF2, BTG1, BTG2, RAG1, RAG2, ELK3, SH2B3, EP300, MAP2K2, EBI3, MEF2D, MEF2C, CEBPA, and TBLXR1 genes, choosing t(4;11) and t(7;14) as reference events. Of the 36 patients, only 5 (13.8%) had a normal molecular karyotype, and 31 (86.2%) were found to have various molecular karyotype abnormalities-104 deletions, 90 duplications or amplifications, 29 cases of cnLOH and 7 biallelic/homozygous deletions. We found that 11q22-23 duplication involving the BIRC3, ATM and MLL genes was the most adverse prognostic event in the study cohort.

CGAS-STING signalling regulates microglial chemotaxis in genome instability.

Defective DNA damage signalling and repair is a hallmark of age-related and genetic neurodegenerative disease. One mechanism implicated in disease progression is DNA damage-driven neuroinflammation, which is largely mediated by tissue-resident immune cells, microglia. Here, we utilise human microglia-like cell models of persistent DNA damage and ATM kinase deficiency to investigate how genome instability shapes microglial function. We demonstrate that upon DNA damage the cytosolic DNA sensing cGAS-STING axis drives chronic inflammation and a robust chemokine response, exemplified by production of CCL5 and CXCL10. Transcriptomic analyses revealed that cell migratory pathways were highly enriched upon IFN-β treatment of human iPSC-derived microglia, indicating that the chemokine response to DNA damage mirrors type I interferon signalling. Furthermore, we find that STING deletion leads to a defect in microglial chemotaxis under basal conditions and upon ATM kinase loss. Overall, this work provides mechanistic insights into cGAS-STING-dependent neuroinflammatory mechanisms and consequences of genome instability in the central nervous system.