Neurological involvement in patients with primary immunodeficiency

Introduction: Primary immunodeficiency diseases (PID) are defined by recurrent infections, allergies, autoimmunity, and malignancies. Neurologic symptoms are one of the major components of some immunodeficiency syndromes, such as Ataxia-Telangiectasia (AT), Nijmegen breakage syndrome (NBS), and Purine Nucleoside Phosphorylase (PNP) deficiency, which are considered as the primary involvement. Various pathological mechanisms, DNA repair disorders, metabolic abnormalities, and autoimmune phenomena have also been linked with neurological conditions. Materials and method: We retrospectively assessed the neurological involvement in 108 patients out of 6000 with PID in this study. Results: The female/male ratio of the cases was 49/59, and the median age was 13 years (min = 1; max = 60). Neurological problems were detected at a median age of 7 years (min = 0.5; max = 30). Di George Syndrome (DGS) and CVID (common variable immunodeficiency) were the most common diseases in our cohort (n = 31, 30% and n = 30, 27%, respectively). The most frequent outcomes were cognitive delay (n = 63, 58%), epilepsy (n = 25, 23%), and ataxia (n = 20, 18%). Central nervous system involvement was found in 99% of the patients (n = 107), and peripheral nervous system complication was found in only one patient with CVID and chronic inflammatory demyelinating polyneuropathy (CDIP). Cranial MRI was found to be abnormal in 74% (n = 80) of the patients. MRI findings included cerebellar atrophy (n = 33, 34%), white matter lesion (n = 27, 28.4%), cerebral atrophy (n = 21, 22.3%), gray matter lesion (n = 6, 6.3%), hydrocephalus (n = 5, 5,3%), and pituitary gland lesion (n = 3, 3.2%), intracranial hemorrhage (n = 3, 3%), intracranial vasculitis (n = 3, 2.7%), and arterio-venous malformation (n = 1, 0,9%) (AU)

TREC/KREC levels in children with ataxia-telangiectasia.

The aim of the study was to determine the TREC/KREC levels in the patients diagnosed with ataxia-telangiectasia (AT) and to establish their informative value for early diagnosis of this pathology. TRECs and KREC assay was performed using real-time polymerase chain reaction on the DNA of 25 patients diagnosed with AT aged 3 to 14 years and of 173 healthy individuals of the control group aged 1 to 12 years. Clinical and laboratory characteristics of patients were ascertained using their medical records. In the patients with AT, the mean level of TRECs was 542.84 per 106 cells, ranging from 4 to 4720, while mean level of KRECs was 1317.64 per 106 cells, ranging from 146 to 9300. In 84% of the patients, TREC levels were less than 1000, which was significantly lower than in the control group, while KREC levels were reduced in 48% of the patients. A correlation was found between the levels of TREC and the absolute values of CD4 (r = 0.5455). Measurement of TREC/KREC levels opens new opportunities for early AT detection in children as a part of the newborn screening. Reduced time to diagnosis will allow to carry out timely in-depth immunological and genetic testing, prevent the development of severe infections, and improve quality of life.

Retrospective Diagnosis of Ataxia-Telangiectasia in an Adolescent Patient With a Remote History of T-Cell Leukemia.

Ataxia-telangiectasia (A-T) is a rare autosomal recessive disorder characterized by progressive cerebellar degeneration that is typically diagnosed in early childhood. A-T is associated with a predisposition to malignancies, particularly lymphoid tumors in childhood and early adulthood. An adolescent girl with minimal neurologic symptoms was diagnosed with A-T 8 years after completing therapy for T-cell acute lymphoblastic leukemia, following a diagnosis of ATM-mutated breast cancer in her mother. We highlight the importance of recognizing ATM mutations in T-cell acute lymphoblastic leukemia, appreciating the phenotypic heterogeneity of A-T, and defining optimal cancer screening in A-T patients.

Variable Abnormalities in T and B Cell Subsets in Ataxia Telangiectasia.

BACKGROUND: Ataxia-telangiectasia (AT) is a rare genetic condition, caused by biallelic deleterious variants in the ATM gene, and has variable immunological abnormalities. This study aimed to examine immunologic parameters reflecting cell development, activation, proliferation, and class switch recombination (CSR) and determine their relationship to the clinical phenotype in AT patients. METHODS: In this study, 40 patients with a confirmed diagnosis of AT from the Iranian immunodeficiency registry center and 28 age-sex matched healthy controls were enrolled. We compared peripheral B and T cell subsets and T cell proliferation response to CD3/CD28 stimulation in AT patients with and without CSR defects using flow cytometry. RESULTS: A significant decrease in naïve, transitional, switched memory, and IgM only memory B cells, along with a sharp increase in the marginal zone-like and CD21low B cells was observed in the patients. We also found CD4+ and CD8+ naïve, central memory, and terminally differentiated effector memory CD4+ (TEMRA) T cells were decreased. CD4+ and CD8+ effector memory, CD8+ TEMRA, and CD4+ regulatory T cells were significantly elevated in our patients. CD4+ T cell proliferation was markedly impaired compared to the healthy controls. Moreover, immunological investigations of 15 AT patients with CSR defect revealed a significant reduction in the marginal zone, switched memory, and more intense defects in IgM only memory B cells, CD4+ naïve and central memory T cells. CONCLUSION: The present study revealed that patients with AT have a broad spectrum of cellular and humoral deficiencies. Therefore, a detailed evaluation of T and B cell subsets increases understanding of the disease in patients and the risk of infection.

Severe reaction to radiotherapy provoked by hypomorphic germline mutations in ATM (ataxia-telangiectasia mutated gene).

BACKGROUND: A minority of breast cancer (BC) patients suffer from severe reaction to adjuvant radiotherapy (RT). Although deficient DNA double-strand break repair is considered the main basis for the reactions, pretreatment identification of high-risk patients has been challenging. METHODS: To retrospectively determine the etiology of severe local reaction to RT in a 39-year-old woman with BC, we performed next-generation sequencing followed by further clinical and functional studies. RESULTS: We found a -4 intronic variant (c.2251-4A>G) in trans with a synonymous (c.3576G>A) variant affecting the ATM DNA-repair gene (NG_009830.1, NM_000051.3) which is linked to autosomal recessive ataxia-telangiectasia (A-T). We verified abnormal transcripts resulting from both variants, next to a minor wild-type transcript leading to a residual ATM kinase activity and genomic instability. Follow-up examination of the patient revealed no classic sign of A-T but previously unnoticed head dystonia and mild dysarthria, a family history of BC and late-onset ataxia segregating with the variants. Additionally, her serum level of alpha-fetoprotein (AFP) was elevated similar to A-T patients. CONCLUSION: Considering the variable presentations of A-T and devastating impact of severe reactions to RT, we suggest a routine measurement of AFP in RT-candidate BC patients followed by next-generation sequencing with special attention to non-canonical splice site and synonymous variants in ATM.

Attenuation of ataxia telangiectasia mutated signalling mitigates age-associated intervertebral disc degeneration.

Previously, we reported that persistent DNA damage accelerates ageing of the spine, but the mechanisms behind this process are not well understood. Ataxia telangiectasia mutated (ATM) is a protein kinase involved in the DNA damage response, which controls cell fate, including cell death. To test the role of ATM in the human intervertebral disc, we exposed human nucleus pulposus (hNP) cells directly to the DNA damaging agent cisplatin. Cisplatin-treated hNP cells exhibited rapid phosphorylation of ATM and subsequent increased NF-κB activation, aggrecanolysis, decreased total proteoglycan production and increased expression of markers of senescence, including p21, γH2 AX and SA-ß-gal. Treating cisplatin-exposed hNP cells with an ATM-specific inhibitor negated these effects. In addition, genetic reduction of ATM reduced disc cellular senescence and matrix proteoglycan loss in the progeroid Ercc1-/∆ mouse model of accelerated ageing. These findings suggest that activation of ATM signalling under persistent genotoxic stress promotes disc cellular senescence and matrix homeostatic perturbation. Thus, the ATM signalling pathway represents a therapeutic target to delay the progression of age-associated spine pathologies.

[The pathology of hereditary ovarian tumors]. / Les tumeurs héréditaires de l'ovaire vues par le pathologiste.

About 23% of adnexal tumors are related to a hereditary syndrome, most often hereditary breast and ovarian cancer syndrome or Lynch syndrome, responsible of epithelial tumors. However, the pathologist should be aware of rare hereditary syndromes responsible of non-epithelial ovarian tumors. Ovarian tumors associated with germline mutation of BRCA genes are essentially high-grade serous carcinomas of tubal origin, while those seen in Lynch syndrome are most often endometrioid or clear cell carcinomas. Sex-cord tumors associated with a familial predisposition are Sertoli-Leydig cell tumors in DICER syndrome and sex-cord tumors with annular tubules in Peutz-Jeghers syndrome. Small cell carcinoma of hypercalcemic type may be associated with a rhabdoid tumor predisposition syndrome 2. Finally, rare germ cell tumors have been reported related to ataxia telangiectasia. The recognition of these entities by pathologists is crucial. Even though the morphologic features pointing toward an inherited mutation may vary depending on the syndrome, the diagnosis may contribute to refer the patient for genetic counselling, modifying the management and follow-up of the patient and her family.

Correction of ATM mutations in iPS cells from two ataxia-telangiectasia patients restores DNA damage and oxidative stress responses.

Patients with ataxia-telangiectasia (A-T) lack a functional ATM kinase protein and exhibit defective repair of DNA double-stranded breaks and response to oxidative stress. We show that CRISPR/Cas9-assisted gene correction combined with piggyBac (PB) transposon-mediated excision of the selection cassette enables seamless restoration of functional ATM alleles in induced pluripotent stem cells from an A-T patient carrying compound heterozygous exonic missense/frameshift mutations, and from a patient with a homozygous splicing acceptor mutation of an internal coding exon. We show that the correction of one allele restores expression of ~ 50% of full-length ATM protein and ameliorates DNA damage-induced activation (auto-phosphorylation) of ATM and phosphorylation of its downstream targets, KAP-1 and H2AX. Restoration of ATM function also normalizes radiosensitivity, mitochondrial ROS production and oxidative-stress-induced apoptosis levels in A-T iPSC lines, demonstrating that restoration of a single ATM allele is sufficient to rescue key ATM functions. Our data further show that despite the absence of a functional ATM kinase, homology-directed repair and seamless correction of a pathogenic ATM mutation is possible. The isogenic pairs of A-T and gene-corrected iPSCs described here constitute valuable tools for elucidating the role of ATM in ageing and A-T pathogenesis.

EBV-directed viral-specific T-lymphocyte therapy for the treatment of EBV-driven lymphoma in two patients with primary immunodeficiency and DNA repair defects.

Children with ataxia telangiectasia (AT), a primary immunodeficiency caused by mutations in ATM, which is critical for repairing DNA defects, are at risk for the development of hematologic malignancy, frequently driven by infection with Epstein-Barr virus (EBV). Conventional chemotherapy is poorly tolerated by patients with AT, with excessive toxicity even when doses are reduced. Here, we report on two patients with AT and EBV-positive neoplasms who were treated with EBV-targeted viral-specific T cells (VST). One patient had a prolonged complete response to VSTs while the other had a partial response. Therapy was well tolerated without infusion toxicity or graft-versus-host disease.

Clinical Presentation of Ataxia-Telangiectasia.

BACKGROUND: Ataxia-telangiectasia is a multi-system disorder in which neurologic impairment and immune deficiency are observed. In the present study, patients with ataxia-telangiectasia were followed to provide information regarding clinical and immunological features. METHODS: We report a case series of 18 patients diagnosed with ataxia-telangiectasia, who were referred to a tertiary center of clinical immunology from 2008-2018. Clinical presentations, medical records and lab data were observed during this period with a mean follow-up time of 4.57 ± 2.66 years. RESULTS: The mean age of the patients was 10.92 ± 3.24 years (11 females and 7 males). Thirteen patients (72.22%) were from families with consanguinity. Ataxia was the most common clinical feature, observed in 18 (100%) patients. The predominant clinical presentations were tremor and oculocutaneous telangiectasia, observed in 14 (77.8%) patients; dysarthria and oculomotor apraxia, observed in 13 (72.2%) patients. Infections were recorded in 12 (70.6%) patients. Decreased IgG level and IgA levels were observed in 5 (33.3%) and 6 (40.0%) patients, respectively. Decreased B-cell number and T-cell number were noted in 7 (46.67%) and 11 (73.33%) patients, respectively. Three (16.7%) patients were diagnosed with acute lymphoblastic leukemia and two of them expired subsequently. CONCLUSION: Ataxia-telangiectasia is a progressive disease with no established therapy; so, it necessitates early diagnosis and follow-up of the patients. The presented clinical and immunological data in this study may help with diagnosis and management of the disease complications.

Three new cases of ataxia-telangiectasia-like disorder: No impairment of the ATM pathway, but S-phase checkpoint defect.

Ataxia-telangiectasia-like disorder (ATLD) is a rare genomic instability syndrome caused by biallelic variants of MRE11 (meiotic recombination 11) characterized by progressive cerebellar ataxia and typical karyotype abnormalities. These symptoms are common to those of ataxia-telangiectasia, which is consistent with the key role of MRE11 in ataxia-telangiectasia mutated (ATM) activation after DNA double-strand breaks. Three unrelated French patients were referred with ataxia. Only one had typical karyotype abnormalities. Unreported biallelic MRE11 variants were found in these three cases. Interestingly, one variant (c.424G>A) was present in two cases and haplotype analysis strongly suggested a French founder variant. Variants c.544G>A and c.314+4_314+7del lead to splice defects. The level of MRE11 in lymphoblastoid cell lines was consistently and dramatically reduced. Functional consequences were evaluated on activation of the ATM pathway via phosphorylation of ATM targets (KAP1 and CHK2), but no consistent defect was observed. However, an S-phase checkpoint activation defect after camptothecin was observed in these patients with ATLD. In conclusion, we report the first three French ATLD patients and a French founder variant, and propose an S-phase checkpoint activation study to evaluate the pathogenicity of MRE11 variants.

Cutaneous granulomas with primary immunodeficiency in children: a report of 17 new patients and a review of the literature.

BACKGROUND: Paediatric cutaneous granuloma with primary immunodeficiency (PID) is a rare condition. The physiopathology is unclear, and treatment is challenging. We report on 17 paediatric cases and review the literature. OBJECTIVES: To make dermatologists and dermatopathologists aware of the diagnostic value of skin granulomas in paediatric PID. METHODS: We collected data on 17 patients with cutaneous granulomas and PID registered with us and also reviewed 33 cases from the literature. RESULTS: Cutaneous granuloma was the presenting feature of the PID in 15 of the 50 collated cases. The lesions presented as red-brownish nodules and infiltrated ulcerative plaques, predominantly on the face and limbs. Scleroderma-like infiltration on a single limb was observed in 10% of the cases. The associated PID was ataxia-telangiectasia (52%), combined immunodeficiency (24%), cartilage-hair hypoplasia (6%) and other subtypes (18%). The granulomas were mostly sarcoidal, tuberculoid, palisaded or undefined subtypes. In some patients, several different histopathologic granulomatous patterns were found in the same biopsy. Some granulomas were associated with the presence of a vaccine strain of rubella virus. CONCLUSION: Cutaneous granulomas associated with a PID have a variable clinical presentation. A PID can be suspected when crusty, brownish lesions are found on the face or limbs. The concomitant presence of several histological subtypes in a single patient is suggestive of a PID.

Inflammation, a significant player of Ataxia-Telangiectasia pathogenesis?

INTRODUCTION: Ataxia-Telangiectasia (A-T) syndrome is an autosomal recessive neurodegenerative disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, chromosome instability, radiosensitivity, and predisposition to malignancy. There is growing evidence that A-T patients suffer from pathologic inflammation that is responsible for many symptoms of this syndrome, including neurodegeneration, autoimmunity, cardiovascular disease, accelerated aging, and insulin resistance. In addition, epidemiological studies have shown A-T heterozygotes, somewhat like deficient patients, are susceptible to ionizing irradiation and have a higher risk of cancers and metabolic disorders. AREA COVERED: This review summarizes clinical and molecular findings of inflammation in A-T syndrome. CONCLUSION: Ataxia-Telangiectasia Mutated (ATM), a master regulator of the DNA damage response is the protein known to be associated with A-T and has a complex nuclear and cytoplasmic role. Loss of ATM function may induce immune deregulation and systemic inflammation.

Role of mitochondrial dysfunction in the pathophysiology of DNA repair disorders.

DNA is constantly being damaged, either by endogenous or exogenous genotoxins. In that regard, DNA repair activities are essential for maintaining genomic stability and to life itself. Mutations in genes encoding DNA repair proteins cause severe human syndromes, but DNA repair defects have also been linked to several other diseases, notably to cancer and normal aging. Recently, new evidence has emerged indicating that some DNA repair diseases display mitochondrial and metabolic dysfunction through mechanisms that are yet being uncovered. These results suggest that mitochondria play an import role in the DNA damage response pathways and that damage accumulation may lead to mitochondrial dysfunction via metabolic imbalance and mitophagy impairment. Here we review the recent findings linking mitochondrial impairment and cell death to DNA damage accumulation in the context of DNA repair defects. In addition, the general involvement of DNA damage in cellular dysfunction suggests that these phenomena may be also involved in other human pathologies in which mitochondrial dysfunction and metabolic disruption play causative roles.

Myoclonus in childhood-onset neurogenetic disorders: The importance of early identification and treatment.

BACKGROUND: In clinical practice, myoclonus in childhood-onset neurogenetic disorders frequently remains unrecognized, because it is often overshadowed by other neurological features. Since treatment can lead to significant functional improvement, accurate phenotyping is essential. To demonstrate the importance of early identification and treatment, we report on four patients with various childhood-onset neurogenetic disorders suffering from myoclonus. METHODS: We evaluated four patients with established childhood-onset neurogenetic disorders and involuntary jerky movements, who visited our young-onset movement disorder outpatient clinic. RESULTS: We present the clinical data of four patients (aged 8-21 years) with childhood-onset neurogenetic disorders, including ataxia-telangiectasia, Coffin-Lowry syndrome and epileptic encephalopathy due to SCN1A mutations. All four suffered from jerky movements that hampered normal daily activities and that had gone unrecognized for several years. The presence of multifocal myoclonus was confirmed by polymyography. In all patients, treatment resulted in marked improvement of both myoclonus and overall functioning. CONCLUSION: These cases highlight the relevance of actively searching for myoclonus in childhood-onset neurogenetic disorders, even when a molecular diagnosis has already been established. To further improve the awareness and recognition of myoclonus in children, we provide a list of childhood-onset neurogenetic disorders with myoclonus as important associated feature.

Ataxia-Telangiectasia: Reporte de caso / Ataxia-Telangiectasia: Case report

Presentamos el caso clínico de un niño de 9 años procedente de la región Cusco, con deterioro progresivo del estado neurológico caracterizado por síntomas cerebelosos, asociados a una historia de infecciones respiratorias repetidas y con hallazgos clínicos y de laboratorio que permitieron llegar al diagnóstico de Ataxia-Telangiectasia, enfermedad poco reportada en nuestro país. Se revisa la etiopatogenia, criterios diagnósticos y propuestas terapéuticas disponibles en la actualidad.

We report the case of a 9-year-old from the Cusco region, with progressive deterioration of neurological condition characterized by cerebellar symptoms associated with a history of repeated respiratory infections and clinical and laboratory features that allowed reaching the diagnosis of Ataxia-Telangiectasia, little reported disease in our country. The pathogenesis, diagnostic criteria and therapeutic approaches currently available are reviewed.

Disease-associated MRE11 mutants impact ATM/ATR DNA damage signaling by distinct mechanisms.

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.

Pathogenesis of ataxia-telangiectasia: the next generation of ATM functions.

In 1988, the gene responsible for the autosomal recessive disease ataxia- telangiectasia (A-T) was localized to 11q22.3-23.1. It was eventually cloned in 1995. Many independent laboratories have since demonstrated that in replicating cells, ataxia telangiectasia mutated (ATM) is predominantly a nuclear protein that is involved in the early recognition and response to double-stranded DNA breaks. ATM is a high-molecular-weight PI3K-family kinase. ATM also plays many important cytoplasmic roles where it phosphorylates hundreds of protein substrates that activate and coordinate cell-signaling pathways involved in cell-cycle checkpoints, nuclear localization, gene transcription and expression, the response to oxidative stress, apoptosis, nonsense-mediated decay, and others. Appreciating these roles helps to provide new insights into the diverse clinical phenotypes exhibited by A-T patients-children and adults alike-which include neurodegeneration, high cancer risk, adverse reactions to radiation and chemotherapy, pulmonary failure, immunodeficiency, glucose transporter aberrations, insulin-resistant diabetogenic responses, and distinct chromosomal and chromatin changes. An exciting recent development is the ATM-dependent pathology encountered in mitochondria, leading to inefficient respiration and energy metabolism and the excessive generation of free radicals that themselves create life-threatening DNA lesions that must be repaired within minutes to minimize individual cell losses.

A role for vascular deficiency in retinal pathology in a mouse model of ataxia-telangiectasia.

Ataxia-telangiectasia is a multifaceted syndrome caused by null mutations in the ATM gene, which encodes the protein kinase ATM, a key participant in the DNA damage response. Retinal neurons are highly susceptible to DNA damage because they are terminally differentiated and have the highest metabolic activity in the central nervous system. In this study, we characterized the retina in young and aged Atm-deficient mice (Atm(-/-)). At 2 months of age, angiography revealed faint retinal vasculature in Atm(-/-) animals relative to wild-type controls. This finding was accompanied by increased expression of vascular endothelial growth factor protein and mRNA. Fibrinogen, generally absent from wild-type retinal tissue, was evident in Atm(-/-) retinas, whereas mRNA of the tight junction protein occludin was significantly decreased. Immunohistochemistry labeling for occludin in 6-month-old mice showed that this decrease persists in advanced stages of the disease. Concurrently, we noticed vascular leakage in Atm(-/-) retinas. Labeling for glial fibrillary acidic protein demonstrated morphological alterations in glial cells in Atm(-/-) retinas. Electroretinographic examination revealed amplitude aberrations in 2-month-old Atm(-/-) mice, which progressed to significant functional deficits in the older mice. These results suggest that impaired vascularization and astrocyte-endothelial cell interactions in the central nervous system play an important role in the etiology of ataxia-telangiectasia and that vascular abnormalities may underlie or aggravate neurodegeneration.

Loss of ATM positively regulates the expression of hypoxia inducible factor 1 (HIF-1) through oxidative stress: Role in the physiopathology of the disease.

Ataxia Telangiectasia (AT) is an autosomal recessive disorder characterized by a wide variety of progressive clinical symptoms. This includes neuronal degeneration, oculocutaneous telangiectasias, diabetes mellitus, immunodeficiency, increased risk of cancer and sensitivity to ionizing radiation. The gene mutated in this disease, ATM (Ataxia Telangiectasia Mutated), encodes a protein kinase involved in DNA double strand breaks signalling and repair. ATM deficient cells also display an increase in oxidative stress, by poorly characterized mechanism(s), which clearly contributes to the neurodegenerative aspect of the disease. Despite these advances, the occurrence of the vascular abnormalities, glucose intolerance and insulin resistance remains poorly understood. In different cellular models where ATM expression was disrupted, we demonstrated that the absence of ATM leads to an increased expression of both subunits of the transcription factor Hypoxia Inducible Factor 1 (HIF-1). We also observed enhanced trans-activating functions of HIF-1. HIF-1 is the central regulator of responses to hypoxia which induces the transcription of genes involved in angiogenesis (e.g., VEGF-Vascular Endothelial Growth Factor) and cellular metabolism (e.g., GLUT-1). Interestingly, we demonstrated that ATM disruption positively regulates both expression and function of the basal glucose transporter GLUT-1 as well as the proangiogenic factor, VEGF. In addition, our results suggest that the absence of ATM increases HIF-1 proteins biosynthesis, and this effect is dependant on the oxidative stress existing in ATM deficient cells. Our compelling results highlight a new link between ATM deficiency and the clinical features of the disease and provide a molecular link between ATM downregulation and the increase in tumor angiogenesis observed in human breast cancers.