BACKGROUND: The cisplatin-resistance is still a main course for chemotherapy failure of lung cancer patients. Cisplatin-resistant cancer cells own higher malignance and exhibited increased metastatic ability, but the mechanism is not clear. In this study, we investigated the effects of Ataxia Telangiectasia Mutated (ATM) on lung cancer metastasis.
MATERIALS AND METHODS: Cisplatin-resistant A549CisR and H157CisR cell line were generated by long-term treating parental A549 and H157 cells (A549P and H157P) with cisplatin. Cell growth, cell migration and cell invasion were determined. Gene expressions were determined by Western Blot and qPCR. Tumor metastasis was investigated using a xenograft mouse model.
RESULTS: The IC50 of the cisplatin-resistant cells (A549CisR and H157CisR cells) to cisplatin was 6-8 higher than parental cells. The A549CisR and H157CisR cells expressed lower level of E-cadherin and higher levels of N-cadherin, Vimentin and Snail compared to the parental A549P and H157P cells, and exhibited stronger capabilities of metastatic potential compared to the parental cells. The ATM expression was upregulated in A549CisR and H157CisR cells and cisplatin treatment also upregulated expression of ATM in parental cells, The inhibition of ATM by using specific ATM inhibitor CP466722 or knock-down ATM by siRNA suppressed Epithelial-to-Mesenchymal transition (EMT) and metastatic potential of A549CisR and H157CisR cells. These data suggest that ATM mediates the cisplatin-resistance in lung cancer cells. Expressions of JAK
CONCLUSIONS: Our results show that ATM regulates PD-L1 expression through activation of JAK/STAT3 signaling in cisplatin-resistant cells. Overexpression of ATM contributes to cisplatin-resistance in lung cancer cells. Inhibition of ATM reversed EMT and inhibited cell invasion and tumor metastasis. Thus, ATM may be a potential target for the treatment of cisplatin-resistant lung cancer.

INTRODUCTION: Classic ataxia telangiectasia (A-T) is an autosomal recessive disease characterized by early onset ataxia, immune deficiency, sino-pulmonary disease, lymphoid/solid malignancies and telangiectasias. Prior studies have suggested that chronic inflammation and premature aging may contribute to the development of malignancy and pulmonary disease in people with A-T. To further examine the link between A-T and inflammation, we hypothesized that subjects with classic A-T would have greater enrichment of inflammatory pathways in peripheral blood mononuclear cells (PBMCs) compared to non A-T age-matched controls. To test this hypothesis we used RNAseq as an unsupervised approach to identify biological processes altered in people with classic A-T.
METHODS: PBMCs were isolated from subjects with classic A-T and compared to non-A-T age-matched healthy controls. RNAseq with differential gene expression analyses was then performed. Selected genes were validated by RT-qPCR using cohorts of subjects consisting of classic A-T, mild A-T or non-A-T controls. Subjects with mild A-T were characterized by later onset/mild neurologic features and normal/near normal immune status.
RESULTS: RNAseq revealed 310 differentially expressed genes (DEGs) including genes involved in inflammation, immune regulation, and cancer. Using gene set enrichment analysis, A-T subjects were found to have biological processes enriched for inflammatory and malignancy pathways. In examining a cohort of A-T subjects in which baseline serum IL8 and IL6 levels were measured previously, an association was found between higher serum IL8 levels and higher likelihood of developing malignancy and/or death in a subsequent 4-6 year period.
CONCLUSION: RNAseq using PBMCs from subjects with classic A-T uncovered differential expression of immune response genes and biological processes associated with inflammation, immune regulation, and cancer. Follow-up of A-T subjects over a 4-6 year period revealed an association between higher baseline serum IL8 levels and malignancy/death. These findings support a role for inflammation as a contributing factor in A-T phenotypes.

BACKGROUND: Ataxia telangiectasia (AT) is a rare, multi-systemic, genetic disorder. Mutations in the ATM gene cause dysfunction in cell-cycle, apoptosis and V (D) J recombination leading to neurodegeneration, cellular, humoral immunodeficiencies and predisposition to malignancies. Previous studies have suggested that a sub-group of AT patients with elevated IgM levels have a distinct and more severe phenotype. In the current study we aimed to better characterize this group of patients.
METHODS: We performed a retrospective review of 46 patient records, followed from January 1986 to January 2015 at the Israeli National AT Center. Demographic, clinical, radiological, laboratory data was reviewed and compared between AT patients with elevated IgM levels (EIgM) and patients with normal IgM levels (NIgM).
RESULTS: 15/46(32.6%) patients had significantly elevated IgM levels. This group had a unique phenotype characterized mainly by increased risk of infection and early mortality. Colonization of lower respiratory tract with Mycobacterium gordonae and Pseudomonas aeruginosa as well as viral skin infections were more frequent in EIgM patients. Patients with NIgM had a significantly longer survival as compared to patients with EIgM but had an increased incidence of fatty liver or cirrhosis. T-cell recombination excision circles and kappa-deleting element recombination circle levels were significantly lower in the EIgM group, suggesting an abnormal class switching in this group.
CONCLUSIONS: EIgM in AT patients are indicative of a more severe phenotype that probably results from a specific immune dysfunction. EIgM in AT should be considered a unique AT phenotype that may require different management.

Recent studies have linked constitutive telomere length (TL) to aging-related diseases including cancer at different sites. ATM participates in the signaling of telomere erosion, and inherited mutations in ATM have been associated with increased risk of cancer, particularly breast cancer. The goal of this study was to investigate whether carriage of an ATM mutation and TL interplay to modify cancer risk in ataxia-telangiectasia (A-T) families.The study population consisted of 284 heterozygous ATM mutation carriers (HetAT) and 174 non-carriers (non-HetAT) from 103 A-T families. Forty-eight HetAT and 14 non-HetAT individuals had cancer, among them 25 HetAT and 6 non-HetAT were diagnosed after blood sample collection. We measured mean TL using a quantitative PCR assay and genotyped seven single-nucleotide polymorphisms (SNPs) recurrently associated with TL in large population-based studies.HetAT individuals were at increased risk of cancer (OR = 2.3, 95%CI = 1.2-4.4, P = 0.01), and particularly of breast cancer for women (OR = 2.9, 95%CI = 1.2-7.1, P = 0.02), in comparison to their non-HetAT relatives. HetAT individuals had longer telomeres than non-HetAT individuals (P = 0.0008) but TL was not associated with cancer risk, and no significant interaction was observed between ATM mutation status and TL. Furthermore, rs9257445 (ZNF311) was associated with TL in HetAT subjects and rs6060627 (BCL2L1) modified cancer risk in HetAT and non-HetAT women.Our findings suggest that carriage of an ATM mutation impacts on the age-related TL shortening and that TL per se is not related to cancer risk in ATM carriers. TL measurement alone is not a good marker for predicting cancer risk in A-T families.

Recent developments in sequencing technologies led to the discovery of a novel form of genomic instability, termed chromothripsis. This catastrophic genomic event, involved in tumorigenesis, is characterized by tens to hundreds of simultaneously acquired locally clustered rearrangements on one chromosome. We hypothesized that leukemias developing in individuals with Ataxia Telangiectasia, who are born with two mutated copies of the ATM gene, an essential guardian of genome stability, would show a higher prevalence of chromothripsis due to the associated defect in DNA double-strand break repair. Using whole-genome sequencing, fluorescence in situ hybridization and RNA sequencing, we characterized the genomic landscape of Acute Lymphoblastic Leukemia (ALL) arising in patients with Ataxia Telangiectasia. We detected a high frequency of chromothriptic events in these tumors, specifically on acrocentric chromosomes, as compared with tumors from individuals with other types of DNA repair syndromes (27 cases total, 10 with Ataxia Telangiectasia). Our data suggest that the genomic landscape of Ataxia Telangiectasia ALL is clearly distinct from that of sporadic ALL. Mechanistically, short telomeres and compromised DNA damage response in cells of Ataxia Telangiectasia patients may be linked with frequent chromothripsis. Furthermore, we show that ATM loss is associated with increased chromothripsis prevalence in additional tumor entities.

Ataxia-telangiectasia (AT) is a neurodegenerative disorder characterized by ataxia, telangiectasia, and immunodeficiency. An increased risk of malignancies and respiratory diseases dramatically reduce life expectancy. To better counsel families, develop individual follow-up programs, and select patients for therapeutic trials, more knowledge is needed on factors influencing survival. This retrospective cohort study of 61 AT patients shows that classical AT patients had a shorter survival than variant patients (HR 5.9, 95%CI 2.0-17.7), especially once a malignancy was diagnosed (HR 2.5, 95%CI 1.1-5.5, compared to classical AT patients without malignancy). Patients with the hyper IgM phenotype with hypogammaglobulinemia (AT-HIGM) and patients with an IgG

Ataxia-telangiectasia (A-T) is an autosomal recessive chromosome breakage disorder caused by mutations in the ATM gene. Typically, it presents in early childhood with progressive cerebellar dysfunction along with immunodeficiency and oculocutaneous telangiectasia. An increased risk of malignancy is also associated with the syndrome and, rarely, may be the presenting feature in small children. We describe a 17-year-old boy with slurred speech, mild motor delays and learning disability diagnosed with atypical A-T in the setting of T-cell acute lymphoblastic leukemia. Suspicion for A-T was raised after review of a peripheral blood karyotype demonstrating rearrangements involving chromosomes 7 and/or 14. The diagnosis was confirmed after molecular testing identified a novel homozygous missense variant in ATM (c.5585T>A; p.Leu1862His) that resulted in protein instability and abolished serine/threonine protein kinase activity. To our knowledge, this is the first report of concurrent A-T and lymphoid malignancy diagnoses in an older child or adult with only mild neurological disease. Our experience suggests that screening for the disorder should be considered in any individual with lymphoid malignancy and neurological findings, especially as radiation and certain chemotherapy protocols are contraindicated in A-T.

Peripheral blood was obtained from a 12-year old male carrying bialleleic inactivating mutations at the ATM locus, causing Ataxia-Telangiectasia (A-T). Blood erythroid cells were briefly expanded in vitro and induced pluripotent stem cells (iPSCs) were generated via transfection with episomal vectors carrying hOCT4, hSOX2, hKLF4, hMYC and hBCL2L1. SF-003 iPSCs were free of genomically integrated reprogramming genes, had the specific compound heterozygous mutations, stable karyotype, expressed pluripotency markers and formed teratomas in immunodeficient (NOD scid gamma; NGS) mice. The SF-003 iPSC line may be a useful resource for in vitro modeling of A-T.

We report the case of a 6-year-old female patient with Ataxia Telangiectasia, an extremely rare condition, who developed in addition a left cerebellar astrocytoma and a right cerebellar infarction, considered as two independent events. Children with AT have an increased risk of developing cancer, but only few cases of glioma are reported and, at our knowledge, no other case of unrelated cerebellar glioma and cerebellar infarction in with the same AT patient have been described. The molecular analysis of ATM (Ataxia Telangiectasia Mutated) gene showed that the patient is compound heterozygote for two previously unreported mutations: c.3291delC (p.Phe1097fs) at exon 25 and c.8198A>C (p.Gln2733Pro) at exon 58. The role of the identified ATM gene mutations in the pathogenesis of Ataxia Telangiectasia and the coexisting cerebellar disorders is discussed.

Biallelic mutations in ATM result in the neurodegenerative syndrome Ataxia-Telangiectasia, while ATM haploinsufficiency increases the risk of cancer and other diseases. Previous studies revealed low reprogramming efficiency from A-T and carrier fibroblasts, a barrier to iPS cell-based modeling and regeneration. Here, we tested the feasibility of employing circulating erythroid cells, a compartment no or minimally affected in A-T, for the generation of A-T and carrier iPS cells. Our results indicate that episomal expression of Yamanaka factors plus BCL-xL in erythroid cells results in highly efficient iPS cell production in feeder-free, xeno-free conditions. Moreover, A-T iPS cells generated with this protocol maintain long-term replicative potential, stable karyotypes, re-elongated telomeres and capability to differentiate along the neural lineage in vitro and to form teratomas in vivo. Finally, we find that haploinsufficiency for ATM does not limit reprogramming from human erythroid cells or in vivo teratoma formation in the mouse.

Early onset ataxia telangiectasia (A-T) is a neurodegenerative DNA-instability disorder, which presents early in childhood. Hallmarks of A-T are progressive ataxia and a dramatic increased risk of developing malignancies (25%), especially of hematological origin. In children these malignancies mainly concern aggressive Non-Hodgkin lymphoma, acute leukemias and Hodgkin lymphoma. Of the acute leukemias, T-cell lymphoblastic leukemia (T-ALL) is by far the most common. Since patients with A-T experience increased toxicity to radio- and chemotherapeutic treatment, the optimal treatment strategy of acute leukemia remains subject of debate. Review of literature of treatment of T-ALL in patients with A-T (n = 18) showed that many patients are not diagnosed with A-T at time of presentation of T-ALL. This implicates that physicians must be aware of symptoms of A-T in young patients presenting with T-ALL. Complete remission rates are high following upfront modified as well as unmodified treatment strategies. Treatment of ALL in children with A-T is feasible and should be performed. Definitive treatment strategy must be determined by shared decision making with patient, caretakers and medical team. Future prospective studies are needed to elucidate optimal treatment strategy.

The main aim of current cancer research is to find a way to selectively affect the tumor cells, while leaving normal cells intact. Ataxia telangiectasia and Rad3-related kinase (ATR), a member of the phosphatidylinositol-3-related protein kinases (PIKK), represents a candidate target for achieving this goal. ATR kinase is one of the main kinases of the DNA damage response signaling pathway and responds to DNA damage caused by replication stress and various genotoxic agents (i.e. chemotherapy, ionizing radiation, ultraviolet light). ATR activation triggers cell cycle checkpoints, DNA repair and apoptosis, but also resistance of tumor cells to DNA damaging agents, through stress support under replication stress. Thus, the inhibition of ATR leads to increased effectiveness of cancer therapy and in addition enables highly selective targeting of cancer cells through synthetic lethal interactions. Despite this great potential, only a few potent and selective inhibitors of ATR kinase have been developed to date. However, those which have been developed provide great promise, and are under evaluation in many current preclinical and clinical trials. The purpose of this review is to summarize the potential of ATR inhibitors and the medicinal chemistry efforts which resulted in their identification.

Malignant bowel obstruction (MBO) is commonly seen in patients with advanced abdominal cancers. The incidence of pediatric MBO in a patient with Burkitt's lymphoma and ataxia telangiectasia is rare, with no published case reports till now. Conservative management of inoperable MBO results in relief of symptoms and improves quality of life. An 11-year-old boy with Burkitt's lymphoma and ataxia telangiectasia was referred to pediatric palliative care with MBO. The objective of this report is to demonstrate conservative management of pediatric MBO using continuous ambulatory drug delivery system. The patient was initiated on continuous ambulatory drug delivery (CADD) system for symptom relief. MBO was reversed with conservative management and the child was discharged on self-collapsible portable elastomeric continuous infusion pump under the supervision of a local family physician. The child remained comfortable at home for 4 weeks until his death. His parents were satisfied with the child's symptom control, quality of life, and were able to care for the child at home. In a resource-limited setting, managing patients at home using elastomeric continuous infusion pumps instead of expensive automated CADD is a practical pharmacoeconomic approach.

Ataxia-telangiectasia (A-T) is a rare autosomal recessive, multisystem, neurodegenerative disorder, characterized by oculocutaneous telangiectasias, variable immunodeficiency and progressive neurological impairment. Definitive diagnosis is made by revealing a disease causing mutation on ATM gene. Missense mutations and polymorphisms of ATM gene can play a role in the development of thyroid papillary carcinoma. A 13-year-old Turkish girl was diagnosed with ataxia telengiectasia at the age of 8 years. When she was 12 years old, multi-nodular goiter was detected by physical examination and ultrasonography. She underwent thyroidectomy and histopathologic investigation revealed a papillary carcinoma with follicular variant. The patient received post-operative radioiodine therapy as well as L-thyroxine treatment because she had residual lesions. Up until now, she is the first Turkish child wit A-T and thyroid carcinoma described in the literature.

Ataxia-telangiectasia (AT) is an autosomal recessive neurodegenerative disorder with immunodeficiency and an increased risk of developing cancer, caused by mutations in the ataxia-telangiectasia mutated (ATM) gene. Logically, blood relatives may also carry a pathogenic ATM mutation. Female carriers of such a mutation have an increased risk of breast cancer. Other health risks for carriers are suspected but have never been studied systematically. Consequently, evidence-based guidelines for carriers are not available yet. We systematically analyzed all literature and found that ATM mutation carriers have a reduced life expectancy because of mortality from cancer and ischemic heart diseases (RR 1.7, 95% CI 1.2-2.4) and an increased risk of developing cancer (RR 1.5, 95% CI 0.9-2.4), in particular breast cancer (RRwomen 3.0, 95% CI 2.1-4.5), and cancers of the digestive tract. Associations between ATM heterozygosity and other health risks have been suggested, but clear evidence is lacking. Based on these results, we propose that all female carriers of 40-50 years of age and female ATM c.7271T>G mutation carriers from 25 years of age onwards be offered intensified surveillance programs for breast cancer. Furthermore, all carriers should be made aware of lifestyle factors that contribute to the development of cardiovascular diseases and diabetes.

Ataxia-telangiectasia (A-T) is a rare multi-system disorder caused by mutations in the ATM gene. Significant heterogeneity exists in the underlying genetic mutations and clinical phenotypes. A number of mouse models have been generated that harbor mutations in the distal region of the gene, and a recent study suggests the presence of residual ATM protein in the brain of one such model. These mice recapitulate many of the characteristics of A-T seen in humans, with the notable exception of neurodegeneration. In order to study how an N-terminal mutation affects the disease phenotype, we generated an inducible Atm mutant mouse model (Atm(tm1Mmpl/tm1Mmpl), referred to as A-T [M]) predicted to express only the first 62 amino acids of Atm. Cells derived from A-T [M] mutant mice exhibited reduced cellular proliferation and an altered DNA damage response, but surprisingly, showed no evidence of an oxidative imbalance. Examination of the A-T [M] animals revealed an altered immunophenotype consistent with A-T. In contrast to mice harboring C-terminal Atm mutations that disproportionately develop thymic lymphomas, A-T [M] mice developed lymphoma at a similar rate as human A-T patients. Morphological analyses of A-T [M] cerebella revealed no substantial cellular defects, similar to other models of A-T, although mice display behavioral defects consistent with cerebellar dysfunction. Overall, these results suggest that loss of Atm is not necessarily associated with an oxidized phenotype as has been previously proposed and that loss of ATM protein is not sufficient to induce cerebellar degeneration in mice.

BACKGROUND/AIM: The expression patterns of the key DNA damage response-related proteins, ataxia-telangiectasia and tfiih/ner complex atp-dependent 5'-3' dna helicase subunit rad3 (RAD3)-related (ATR) and ataxia-telangiectasia-mutated (ATM) proteins in ovarian cancer are not well-known. This study aimed to evaluate the expressions of ATR and ATM proteins, and to investigate their clinical significance in epithelial ovarian carcinoma (EOC).
MATERIALS AND METHODS: The expressions of nuclear/cytoplasmic Ser428-phosphorylated ATR (p-ATR) and Ser1981-phosphorylated ATM (p-ATM) were evaluated by immunohistochemistry in 100 patients with EOC. The clinical significances of p-ATR and p-ATM protein expression were evaluated in terms of tumor progression and survival.
RESULTS: Low expression of cytoplasmic p-ATR was significantly associated with advanced stage, serous histology, large residual mass, and high preoperative serum CA125 level. Univariate survival analysis revealed that low expression of cytoplasmic p-ATR protein was significantly associated with poor disease-free survival and poor overall survival.
CONCLUSION: Our study demonstrates that cytoplasmic ATR protein might serve as a prognostic biomarker for patients with EOC.

Patients with ataxia telangiectasia (AT) with malignancies face poor prognosis due to increased treatment-related toxicity. Here, we report a 14-year-old male with AT and Hodgkin lymphoma (HL) who received brentuximab vedotin and reduced COPP plus rituximab courses. This treatment resulted in complete remission and showed no severe toxicity.

Hematologic malignancies, in particular T-cell lymphomas/leukemias, are prevalent in patients with ataxia telangiectasia (AT), with most reported cases being clinically aggressive and high grade. Epstein-Barr virus (EBV) is often associated with lymphoid proliferations/neoplasms arising in immunodeficient patients. Reports of low-grade B-cell neoplasms in the ataxia telangiectasia population are extremely rare. Here, we describe a case of EBV-associated extranodal marginal zone lymphoma (mucosa-associated lymphoid tissue lymphoma) of the parotid gland in a 16-year-old boy with AT. In addition, we review the literature of hematologic malignancies in the AT population as well as the occurrence of EBV in mucosa-associated lymphoid tissue lymphoma.

BACKGROUND: Accumulated evidence has indicated that ataxia-telangiectasia mutated (ATM) gene polymorphisms are closely related to lung cancer. We aimed to explore the prognostic value of rs189037 (G>A), one of ATM single nucleotide polymorphisms (SNPs), and detect whether it involves in the risk of lung cancer in Chinese Han people.
METHODS: In this hospital-based matched case-control study, 852 lung cancer patients and 852 healthy controls have been put into comparison to analyze the association between rs189037 and lung cancer risk in Chinese. The single nucleotide polymorphisms were determined by TaqMan real-time PCR and we used SPSS software to perform the statistical analyses.
RESULTS: Individuals carrying variant AA genotype of rs189037 had higher lung cancer risk (adjusted OR: 1.56) than those carrying GG genotype. After analyzing data respectively from different groups divided by genders and smoking status, we observed that the risk effect of AA genotype on the lung cancer was significant in females, non-smokers and female non-smokers, as well as the risk effect of GA genotype in male smokers. Compared with non-smokers carrying GG genotype, smokers carrying at least one A allele had higher risk of developing lung cancer than those with GG genotype (adjusted OR: 3.52 vs. adjusted OR: 2.53).
CONCLUSIONS: This study suggested that rs189037 (G>A) polymorphism is associated with lung cancer risk in Chinese Han population. AA genotype and A allele may be dangerous lung cancer signals in Chinese and make contribution to diagnostic and treatment value.

PURPOSE: Biallelic mutations in ATM cause ataxia-telangiectasia (AT), a rare inherited disease with a high incidence of cancer. Precise estimates of the risk, presentation, and outcomes of cancer in patients with AT need to be addressed in large series.
PATIENTS AND METHODS: In this large retrospective cohort, 69 patients with cancers (24.5%) were identified among 279 patients with AT. Centralized review was performed on 60% of the lymphomas. Incidence rates were compared with the French population, and risk factors were analyzed.
RESULTS: Eight patients developed acute leukemias (including four T-cell acute lymphoblastic leukemias), 12 developed Hodgkin lymphoma (HL), 38 developed non-Hodgkin lymphoma (NHL), three developed T-cell prolymphocytic leukemia (T-PLL), and eight developed carcinoma at a median age of 8.3, 10.6, 9.7, 24.2, and 31.4 years, respectively (P < .001). The majority of NHLs were aggressive B-cell NHL. Epstein-Barr virus was associated with all of the HLs and 50% of the NHLs. Overall survival was shorter in patients with AT who developed cancer compared with those who did not develop cancer (15 v 24 years, respectively; P < .001). Survival was improved in patients who achieved a major response to treatment (3.46 v 0.87 years for major v minor responses, respectively; P = .011). Immunodeficiency was associated with increased risk of cancer. ATM mutation type was associated with a difference in survival in the entire cohort but not with cancer incidence or cancer survival.
CONCLUSION: B-cell NHL, HL, and acute lymphoblastic leukemia occur at a high rate and earlier age than carcinomas in AT. T-PLLs are rarer than initially reported. Prognosis is poor, but patients may benefit from treatment with an improved survival.

Ataxia telangiectasia (A-T) is a rare recessively inherited disorder resulting in a progressive neurological decline. It is caused by biallelic mutation of the ATM gene that encodes a 370 kDa serine/threonine protein kinase responsible for phosphorylating many target proteins. ATM is activated by auto(trans)phosphorylation in response to DNA double strand breaks and leads to the activation of cell cycle checkpoints and either DNA repair or apoptosis as part of the cellular response to DNA damage. The allelic heterogeneity in A-T is striking. While the majority of mutations are truncating, leading to instability and loss of the ATM protein from the allele, a significant proportion of patients carry one of a small number of mutations that are either missense or leaky splice site mutations resulting in retention of some ATM with activity. The allelic heterogeneity in ATM, therefore, results in an equally striking clinical heterogeneity. There is also locus heterogeneity because mutation of the MRE11 gene can cause an obvious A-T like disorder both clinically and also at the cellular level and mutation of the RNF168 gene results in a much milder clinical phenotype, neurologically, with the major clinical feature being an immunological defect.

Ataxia telangiectasia is a neurodegenerative inherited disease with chromosomal instability and hypersensitivity to ionizing radiation. iPS cells lacking ATM (AT-iPS cells) exhibited hypersensitivity to X-ray irradiation, one of the characteristics of the disease. While parental ataxia telangiectasia cells exhibited significant chromosomal abnormalities, AT-iPS cells did not show any chromosomal instability in vitro for at least 80 passages (560 days). Whole exome analysis also showed a comparable nucleotide substitution rate in AT-iPS cells. Taken together, these data show that ATM is involved in protection from irradiation-induced cell death.

A 20-month-old girl diagnosed with T-cell acute lymphoblastic leukemia was treated according to the Nordic NOPHO ALL2000 protocol. The patient developed severe immunosuppression and experienced life-threatening adenovirus infection, which was treated with ribavirin and cidofovir. α-fetoprotein was 20- to 30-fold elevated, and genetic analysis confirmed the diagnosis of ataxia telangiectasia. Despite receiving only 7 weeks of anti-leukemic therapy, she has stayed in first remission now 8 years after the diagnosis. We speculate that this could be because of increased chemosensitivity of ATM-mutated leukemic cells, adenovirus causing a direct oncolytic effect, and/or high levels of endogenous cortisol during her severe infection.

Neuroblastoma (NB) is a paediatric solid tumour which originates from sympathetic nervous tissues. Deletions in chromosome 1p are frequently found in unfavourable NBs and are correlated with v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) amplification; however, it remains to be elucidated how the 1p loss contributes to MYCN-related oncogenic processes in NB. In this study, we identified the role of Dnmt1-associated protein 1 (DMAP1), coded on chromosome 1p34, in the processes. We studied the expression and function of DMAP1 in NB and found that low-level expression of DMAP1 related to poor prognosis, unfavourable histology and 1p Loss of heterozygosity (LOH) of primary NB samples. Intriguingly, DMAP1 induced ataxia telangiectasia mutated (ATM) phosphorylation and focus formation in the presence of a DNA damage reagent, doxorubicin. By DMAP1 expression in NB and fibroblasts, p53 was activated in an ATM-dependent manner and p53-downstream pro-apoptotic Bcl-2 family molecules were induced at the mRNA level, resulting in p53-induced apoptotic death. BAX and p21(Cip1/Waf1) promoter activity dependent on p53 was clearly up-regulated by DMAP1. Further, MYCN transduction in MYCN single-copy NB cells accelerated doxorubicin (Doxo)-induced apoptotic cell death; MYCN is implicated in DMAP1 protein stabilisation and ATM phosphorylation in these situations. DMAP1 knockdown attenuated MYCN-dependent ATM phosphorylation and NB cell apoptosis. Together, DMAP1 appears to be a new candidate for a 1p tumour suppressor and its reduction contributes to NB tumourigenesis via inhibition of MYCN-related ATM/p53 pathway activation.

Ataxia telangiectasia (AT) is a rare autosomal recessive multisystem disorder characterised by cerebellar degeneration, immunodeficiency and cancer predisposition. Around 10% of AT patients develop lymphoid malignancies, but the development of myeloid leukaemia with AT (AT-AML) is extremely rare, and there have been no previous publications regarding suitable therapies. Here, we first describe a successful therapeutic experience in a patient with AT-AML (FAB-M1) who attained remission after induction therapy and maintained stable disease for a year. To minimise therapy-induced toxicity, low-dose induction was applied first, though this was obviously insufficient and the patient subsequently responded well to dose-intensified short-term chemotherapy. In this report, we suggest a curative therapeutic approach for AT-AML, though the issue of how best to manage patients with cancer complicated by immunodeficiency remains undecided.

DNA double-strand breaks (DSBs) can lead to instability of the genome if not repaired correctly. The MRE11/RAD50/NBS1 (MRN) complex binds DSBs and initiates damage-induced signaling cascades via activation of the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia- and rad3-related (ATR) kinases. Mutations throughout MRE11 cause ataxia-telangiectasia-like disorder (ATLD) featuring cerebellar degeneration, and cancer-predisposition in certain kindreds. Here, we have examined the impact on DNA damage signaling of several disease-associated MRE11A alleles to gain greater understanding of the mechanisms underlying the diverse disease sequelae of ATLD. To this end, we have designed a system whereby endogenous wild-type Mre11a is conditionally deleted and disease-associated MRE11 mutants are stably expressed at physiologic levels. We find that mutations in the highly conserved N-terminal domain impact ATM signaling by perturbing both MRE11 interaction with NBS1 and MRE11 homodimerization. In contrast, an inherited allele in the MRE11 C-terminus maintains MRN interactions and ATM/ATR kinase activation. These findings reveal that ATLD patients have reduced ATM activation resulting from at least two distinct mechanisms: (i) N-terminal mutations destabilize MRN interactions, and (ii) mutation of the extreme C-terminus maintains interactions but leads to low levels of the complex. The N-terminal mutations were found in ATLD patients with childhood cancer; thus, our studies suggest a clinically relevant dichotomy in MRE11A alleles. More broadly, these studies underscore the importance of understanding specific effects of hypomorphic disease-associated mutations to achieve accurate prognosis and appropriate long-term medical surveillance.

Children with ataxia-telangiectasia (A-T) and cancer have a poorer prognosis due in part to increased treatment-related toxicity. We piloted a curative intent approach in five children with A-T who presented with advanced stage (III, n = 2; IV, n = 3) B-NHL (diffuse large B-cell lymphoma, n = 4; Burkitt leukemia, n = 1) using a modified LMB-based protocol. Two achieved sustained CCR (one, CCR at 6 years; one, pulmonary death after 3 years in CCR). Two died from toxicity during induction and 1 failed induction with progressive disease. Novel therapeutic approaches which overcome drug resistance and are less toxic are needed for children with A-T and B-NHL.

Variant ataxia telangiectasia (A-T) may be an underdiagnosed entity. We correlate data from radiosensitivity and kinase assays with clinical and molecular data from a patient with variant A-T and relatives. The coding region of ATM was sequenced. To evaluate the functional effect of the mutations, we performed kinase assays and developed a novel S-G2 micronucleus test. Our patient presented with mild dystonia, moderately dysarthric speech, increased serum α-fetoprotein but no ataxia nor telangiectasias, no nystagmus or oculomotor dyspraxia. She has a severe IgA deficiency, but does not have recurrent infections. She is compound heterozygote for ATM c.8122G>A (p.Asp2708Asn) and c.8851-1G>T, leading to in frame loss of 63 nucleotides at the cDNA level. A trace amount of ATM protein is translated from both alleles. Residual kinase activity is derived only from the p.Asp2708Asn allele. The conventional G0 micronucleus test, based on irradiation of resting lymphocytes, revealed a radiosensitive phenotype for the patient, but not for the heterozygous relatives. As ATM is involved in homologous recombination and G2/M cell cycle checkpoint, we optimized an S-G2 micronucleus assay, allowing to evaluate micronuclei in lymphocytes irradiated in the S and G2 phases. This test showed increased radiosensitivity for both the patient and the heterozygous carriers. Intriguingly, heterozygous carriers of c.8851-1G>T (mutation associated with absence of kinase activity) showed a stronger radiosensitive phenotype with this assay than heterozygous carriers of p.Asp2708Asn (mutation associated with residual kinase activity). The modified S-G2 micronucleus assay provided phenotypic insight into complement the diagnosis of this atypical A-T patient.