ALBERT

Description: Acute lymphoblastic leukemia (ALL) is the most common malignancy in childhood. While improved multi-agent chemotherapy regimens with individualized risk stratification have led to increased survival rates of approximately 80 percent, 20 percent of patients respond poorly to therapy or relapse. Therefore, novel therapeutic avenues are urgently needed to improve treatment outcome, overcome resistance and reduce side effects. Failure to undergo cell death represents a key survival mechanism of cancer cells and results in drug resistance and clonal escape. Since inhibitor of apoptosis proteins (IAPs) are often overexpressed in malignant cells and their overexpression correlates with inferior survival rates, they provide an attractive molecular target for therapeutic intervention. Small molecule inhibitors have been developed that act as SMAC mimetics (SMs) to counteract the cell death inhibitory function of IAPs. SMs can activate and/or modulate cell death pathways, and are currently being evaluated in clinical trials. Their successful therapeutic implementation requires identification of patients who could benefit from a SM-based treatment regimen ideally before start of therapy. Here, we analyzed the intrinsic activity of two monovalent (AT406 and LCL161) and two bivalent (Birinapant or BV6) SMs on 29 unselected patient-derived pediatric precursor B-cell (BCP)-ALL samples and identified a subset of BCP-ALL primografts to be sensitive to SM treatment (n=8). When we compared gene expression of SM-sensitive (n=8) and SM-insensitive (n=6) patient-derived BCP-ALL samples, we identified a characteristic gene expression signature with 127 differentially regulated genes, amongst them upregulation of TNFRSF1A (TNFR1) in the SM-sensitive subset. In line with previous reports, we confirmed a critical role of the TNF/TNFR1-axis for SM-induced cell death in BCP-ALL by functional analysis. Expression of TNFRSF1A alone, however, did not correlate with sensitivity to SM-induced cell death indicating that TNFR1 is not the only factor regulating cell fate decisions in response to SM treatment. To identify potential biomarker genes for prediction of patient response to SM monotherapy in BCP-ALL, we compared differentially regulated genes of SM responders and non-responders from our cohort with data from a published cohort. Interestingly, we found 4 genes to overlap between these two cohorts. Of these 4 genes TSPAN7, FAM69C, and TNFRSF1A were upregulated whereas MTX2 was downregulated in SM-sensitive samples. The signature identified may reflect a particular TNF network. Analysis of expression levels of these 4 genes in BCP-ALL cell lines (Nalm6, Reh, UoCB6 and RS4;11) revealed that Reh cells, sensitive to SM-induced cell death, exhibited the biomarker profile of primograft sensitivity, i.e. upregulation of TSPAN7, FAM69C, TNFRSF1A and downregulation of MTX2. Nalm6 cells resembled the expression pattern of SM-insensitive samples with a downregulation of TSPAN7, FAM69C, TNFRSF1A and an upregulation of MTX2 and were resistant to SM-induced cell death. RS4;11 and UoCB6 cells showed no pattern. Based on these findings we hypothesized that the respective expression patterns of TSPAN7, FAM69C, TNFRSF1A and MTX2 could predict sensitivity to SMs. An extended screen of additional primary BCP-ALL samples for their expression levels of TSPAN7, FAM69C, TNFRSF1A and MTX2 and response to SMs substantiated this hypothesis. In summary, the subset of primary BCP-ALL samples with sensitivity to SMs is characterized by a gene signature with MTX2 low and TSPAN7, FAM69C and TNFRSF1A high. By using this expression profile, sensitivity to SMs in BCP-ALL could be identified in cell lines and additional primografts. Based on these results, we suggest the identified gene expression pattern as a biomarker for selecting patients to be treated by SM monotherapy in clinical trials. Disclosures No relevant conflicts of interest to declare.

Description: The piranha enjoys notoriety due to its infamous predatory behavior but much is still not understood about its evolutionary origins and the underlying molecular mechanisms for its unusual feeding biology. We sequenced and assembled the red-bellied piranha (Pygocentrus nattereri) genome to aid future phenotypic and genetic investigations. The assembled draft genome is similar to other related fishes in repeat composition and gene count. Our evaluation of genes under positive selection suggests candidates for adaptations of piranhas’ feeding behavior in neural functions, behavior, and regulation of energy metabolism. In the fasted brain, we find genes differentially expressed that are involved in lipid metabolism and appetite regulation as well as genes that may control the aggression/boldness behavior of hungry piranhas. Our first analysis of the piranha genome offers new insight and resources for the study of piranha biology and for feeding motivation and starvation in other organisms.

Description: Color patterns in African cichlid fishes vary spectacularly. Although phylogenetic analysis showed already 30 years ago that many color patterns evolved repeatedly in these adaptive radiations, only recently have we begun to understand the genomic basis of color variation. Horizontal stripe patterns evolved and were lost several times independently across the adaptive radiations of Lake Victoria, Malawi, and Tanganyika and regulatory evolution of agouti-related peptide 2 (agrp2/asip2b) has been linked to this phenotypically labile trait. Here, we asked whether the agrp2 locus exhibits particular characteristics that facilitate divergence in color patterns. Based on comparative genomic analyses, we discovered several recent duplications, insertions, and deletions. Interestingly, one of these events resulted in a tandem duplication of the last exon of agrp2. The duplication likely precedes the East African radiations that started 8–12 Ma, is not fixed within any of the radiations, and is found to vary even within some species. Moreover, we also observed variation in copy number (two to five copies) and secondary loss of the duplication, illustrating a surprising dynamic at this locus that possibly promoted functional divergence of agrp2. Our work suggests that such instances of exon duplications are a neglected mechanism potentially involved in the repeated evolution and diversification that deserves more attention.

Description: Childhood Leukemia treatment is one of the most common malignancies seen across the globe in the pediatric age group. Severe Hemophilia A is still considered a rare bleeding disorder. Only 13 patients with hemophilia A or B have been reported in literature to also be diagnosed with acute leukemia in childhood . This rarity appeared again in a 13 year boy with severe hemophilia A who presented with worsening bone pain and joint swelling, weight loss and leukocytosis. Morphology and molecular diagnostics confirmed Acute Pre B Lymphoblastic Leukemia . The patient happens to be the first case of Acute Lymphoblastic Leukemia in a patient with severe Hemophilia with Inhibitors. Severe hemophilia with inhibitors pose challenge in clinical management given their propensity of bleeding and poor response to traditional therapies due to a neutralizing antibody as is. Treatment of acute lymphoblastic leukemia requires an intensive treatment with systemic and intrathecal chemotherapy. Medications are commonly administered through a central line, in many cases an implantable catheter. Coexistence of both these life threatening disorders posed a unique practical challenge in providing standard care and our discussion aims at highlighting strategies in management of Severe Hemophilia in challenging clinical scenarios. Disclosures No relevant conflicts of interest to declare.

Description: Glucocorticoids (GCs) are central to the treatment of T-cell acute lymphoblastic leukemia (T-ALL), and upfront resistance to GCs is a poor prognostic factor. We previously demonstrated that over one-third of primary patient T-ALLs are resistant to the GC dexamethasone (DEX) when cultured in the presence of interleukin-7 (IL7), a cytokine that is abundant in the microenvironment of leukemic blasts and that plays a well-established role in leukemogenesis. Mechanistically, we demonstrated that GCs paradoxically induce their own resistance by promoting the upregulation of IL7 receptor (IL7R) expression. In the presence of IL7, this augments signal transduction through the JAK/STAT5 axis, ultimately leading to increased STAT5 transcriptional output. This promotes the upregulation of the pro-survival protein BCL-2, which opposes DEX-induced apoptosis. Given that IL7-induced GC resistance depends on de novo synthesis of IL7R in response to DEX, and that newly synthesized IL7R reaches the cell surface via trafficking through the secretory pathway, we hypothesized that inhibiting the translocation of nascent IL7R peptide into the secretory pathway would effectively overcome IL7-induced DEX resistance. Sec61 is a protein-conducting channel in the membrane of the endoplasmic reticulum (ER) that is required for the cotranslational insertion of nascent polypeptides into the ER upon recognition of the signal sequence on secreted and cell surface proteins. To test the hypothesis that Sec61 inhibition could overcome IL7-induced DEX resistance, we utilized the human T-ALL cell line CCRF-CEM, which recapitulates the resistance phenotype observed in primary patient samples. Using a series of structurally distinct small molecule inhibitors of the Sec61 translocon, we demonstrated that Sec61 inhibition effectively overcomes the increase in cell surface IL7R expression in response to DEX. This occurs despite a persistent elevation in IL7R transcript expression following DEX exposure, confirming that Sec61 inhibitors act post-transcriptionally to attenuate cell surface IL7R expression. To determine whether the sensitivity of IL7R to Sec61 inhibitors is due specifically to the interaction between the IL7R signal sequence and Sec61 inhibitors, we generated IL7R constructs containing hydrophobic amino acid substitutions in the signal sequence, which are predicted to confer resistance to Sec61 inhibitors. Upon transient transfection of these constructs into HEK293T cells, we found that these mutations rendered IL7R resistant to the effects of Sec61 inhibition, confirming that the IL7R signal sequence confers sensitivity to these inhibitors. Using the Bliss independence model of synergy in CCRF-CEM cells, we demonstrated that Sec61 inhibitors potently synergize with DEX to overcome IL7-induced DEX resistance. Importantly, at concentrations at which synergy occurs, Sec61 inhibitors demonstrate no single-agent effect on cell survival, suggesting that these effects are not due to an overall reduction in secretory and membrane protein biogenesis. Furthermore, Sec61 inhibitors failed to sensitize CCRF-CEM cells to other chemotherapies used in T-ALL, none of which demonstrate IL7-induced resistance, thereby suggesting that these effects on DEX sensitivity are due specifically to the reduction in cell surface IL7R. To determine if Sec61 inhibitors prevent the DEX-induced increase in STAT5 transcription, we analyzed BCL-2 expression in cells exposed to DEX and IL7, and found that Sec61 inhibitors attenuate the increase in BCL-2 expression in a dose-dependent manner. We next analyzed a cohort of 34 primary patient T-ALL samples. As in CCRF-CEM cells, we found that specifically in those samples with IL7-induced DEX resistance, Sec61 inhibitors synergized with DEX to induce cell death in the presence of IL7. This effect occurred concomitantly with a reduction in cell surface IL7R expression and BCL-2 expression. Taken together, these data demonstrate the efficacy and feasibility of Sec61 inhibition as a novel and rational therapeutic strategy to overcome the IL7-induced DEX resistance phenotype that affects over one-third of newly diagnosed T-ALL patients. Disclosures Sharp: Kezar Life Sciences: Patents & Royalties. McMinn:Kezar Life Sciences: Employment, Equity Ownership. Kirk:Kezar Life Sciences: Employment, Equity Ownership. Taunton:Global Blood Therapeutics: Equity Ownership; Principia Biopharma: Equity Ownership, Patents & Royalties; Cedilla Therapeutics: Consultancy, Equity Ownership; Pfizer: Research Funding; Kezar Life Sciences: Equity Ownership, Patents & Royalties, Research Funding.

Description: von Willebrand factor (VWF) is a large multimeric plasma glycoprotein that plays a crucial role in hemostasis and thrombosis. VWF recruits platelets at sites of vascular injury by acting as a molecular bridge between circulating platelets and the site of injured or activated blood vessels. Biosynthesis of VWF is restricted to endothelial cells and megakaryocytes. Endothelial VWF is constitutively secreted into plasma and subendothelium, or is stored as "ultra-large" (UL)-VWF multimers in endothelial Weibel-Palade bodies. VWF produced in megakaryocytes is packaged as UL-VWF in the a-granules of platelets. VWF stored in endothelial and platelet storage organelles is secreted in a regulated process in response to stimulation by secretagogues. Absence or dysfunction of VWF results in bleeding symptoms, as observed in patients with von Willebrand disease. An abnormally high activity of VWF can lead to thrombotic events. Interestingly, the activity of VWF is determined by the size of its multimers and UL-VWF can spontaneously form platelet aggregates. An important regulator of VWF size is the metalloprotease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), which digests large thrombogenic VWF molecules into smaller, less reactive multimers via cleavage of the Y1605-M1606 bond in the VWF A2 domain. ADAMTS13 is mainly synthesized in the liver by hepatic stellate cells, but other sites of synthesis, including renal podocytes, tubular epithelial cell, platelets and endothelial cells, have also been described. ADAMTS13 is released as an active enzyme into the circulation with no physiological inhibitors. Reduced or absent ADAMTS13 activity causes the microangiopathic disorder thrombotic thrombocytopenic purpura (TTP), characterized by VWF and platelet-rich microthrombi that cause multiple organ failure and even death when left untreated. Besides its clear role in the pathophysiology of TTP, the anti-thrombotic and even anti-inflammatory properties of ADAMTS13 have also become apparent in various other thrombotic conditions. High VWF levels and low ADAMTS13 levels are associated with increased risk or even worse outcome of cardiovascular disease, including ischemic stroke and myocardial infarction. Preclinical studies in mouse models showed the beneficial effect of ADAMTS13 in both cerebral and myocardial ischemia/ reperfusion injury by decreasing both thrombosis and inflammation. In addition, ADAMTS13 was shown to also exert a direct thrombolytic effect on VWF-rich thrombi. In a mouse model of ischemic stroke, this thrombolytic activity resulted in efficient lysis of intracranial thrombi that were resistant to standard treatment with tissue plasminogen activator. Hence, ADAMTS13, as a therapeutic agent, could become an interesting avenue, not only to manage TTP, but also to treat other thrombotic complications. Disclosures De Meyer: Fonds voor Wetenschappelijk Onderzoek: Research Funding; KU Leuven: Employment, Research Funding; Ablynx: Consultancy, Research Funding; Cerenovus: Membership on an entity's Board of Directors or advisory committees; WhiteSwell: Consultancy.

Description: Deregulation of cell death pathways is a hallmark of many cancers and contributes to leukemogenesis and treatment failure in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Different pro- and anti-apoptotic molecules control apoptosis signaling. While pro-apoptotic BCL-2 homology domain 3 (BH3) proteins induce cellular death, apoptosis induction is counter-regulated by anti-apoptotic molecules like B-cell lymphoma 2 (BCL-2). Therefore, inhibition of anti-apoptotic molecules has been developed as therapeutic strategy. Venetoclax (VEN) selectively binds to BCL-2, which leads to the release of pro-apoptotic molecules such as BIM resulting in apoptosis induction. In BCP-ALL, we and others showed preclinical activity of VEN and first clinical trials have started to evaluate VEN in ALL. Despite high activity, resistance can be acquired over time and acquisition of BCL2 mutations has been reported in CLL patients. In this study, we modeled VEN resistance in BCP-ALL and investigated underlying mechanisms in order to identify potential strategies to overcome VEN insensitivity. Starting from the BCP-ALL cell line RS4;11, five parallel VEN insensitive lines were generated by exposure to increasing concentrations of VEN over time (49 passages, over 8 months of continuous treatment). Simultaneously, five control lines were exposed to corresponding concentrations of solvent (DMSO). Measuring half maximal effective concentrations (EC50) over time showed increasing EC50 values from 4 nM to 26.2 µM in all VEN treated lines, reflecting acquired resistance in our model. Importantly, no mutations of the BCL2 gene were identified by sequencing at high coverage (Illumina AmpliSeq, 650- to 5951-fold), excluding acquisition of BCL2 mutations as mechanism of resistance. Next, we assessed expression levels of the mitochondrial apoptosis regulators BCL-2, MCL-1 and BCL-XL by western blot analysis. Comparing VEN insensitive to control cell lines, no differences in expression of the target molecule BCL-2 and similar levels of BCL-XL were observed. Most interestingly, all five VEN insensitive lines showed significant up-regulation of MCL-1 compared to all control lines. We next investigated the dependence of apoptosis signaling on different BCL-2 family members by exposing ALL cells to synthetic BH3-only peptides, which specifically bind to different regulators of mitochondrial apoptosis signaling (BH3-profiling), followed by analysis of apoptosis induction. Interestingly, dependence on BCL-2 was clearly reduced in all VEN insensitive lines indicated by almost lost mitochondrial priming. On the other hand, VEN insensitive ALL cells showed increased dependence on MCL-1. In order to analyze whether our modeled VEN resistance can be overcome by targeting MCL-1, we investigated sensitivity of these cells to the MCL-1 inhibitor S63845. High EC50 values for S63845 were found in all VEN insensitive and corresponding control lines, indicating low anti-MCL-1 activity. Importantly, the combination of S63845 with VEN synergistically induced cell death, showing that acquired VEN insensitivity in BCP-ALL can be overcome by co-targeting BCL-2 and MCL-1. To get insight into the molecular mechanisms underlying the synergism, we treated VEN insensitive ALL cells with VEN, S63845 or both and investigated binding of BIM to either BCL-2 or MCL-1 by immunoprecipitation. In the presence of VEN, clearly lower co-precipitation of BIM with BCL-2 but increased co-precipitation with MCL-1 was observed, indicating that pro-apoptotic BIM displaced from BCL-2 by VEN is sequestered by MCL-1, thereby counter-regulating VEN activity. Inversely, the MCL-1 inhibitor S63845 reduced binding of BIM to MCL-1 but increased BIM binding to BCL-2. Most interestingly, upon combination of both inhibitors, lower BIM binding to both BCL-2 and MCL-1 was found. This indicates that co-targeting MCL-1 can block the sequestration of pro-apoptotic BIM from BCL-2 to MCL-1, overcoming VEN resistance. Taken together, we show that acquired VEN resistance in BCP-ALL is characterized by up-regulated expression of counter-regulatory MCL-1 and can be overcome by simultaneous BCL-2 and MCL-1 inhibition, which prevents sequestration of BIM by MCL-1 after release from BCL-2. Disclosures Tausch: Roche: Consultancy, Honoraria, Speakers Bureau; AbbVie: Consultancy, Honoraria, Other: travel support, Speakers Bureau. Stilgenbauer:Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Other: Travel support; GSK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Hoffmann La-Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau.

Description: Introduction Venous thromboembolism (VTE) is a difficult to treat condition in patients with cancer with a persisting risk of recurrent VTE during anticoagulant treatment with low-molecular weight heparin (LMWH). Recent data suggest that direct oral anticoagulants (DOACS) are associated with a lower risk of recurrence but a higher risk of bleeding in these patients. Predicting the risk of recurrent VTE with LMWH may help to select the best treatment option. We conducted a prospective multicenter observational cohort study in cancer patients with VTE treated with tinzaparin for 6 months in order to validate the Ottawa score (NCT03099031) and search for additional risk of recurrent VTE. The Ottawa score is composed of 5 variables, female sex (+1), lung cancer (+1), breast cancer (-1) cancer stage 1 (-2) and previous DVT (+1). A score ≤0 is associated with a low risk of recurrent VTE. Methods Adult cancer patients with recent diagnosis of documented symptomatic or incidental VTE (deep vein thrombosis (DVT) or pulmonary embolism (PE) treated with tinzaparin for 6 months were included in the study. The primary endpoint was the recurrence of symptomatic or asymptomatic VTE within the first 6 months of treatment with tinzaparin. Other endpoints were symptomatic recurrent VTE, major bleeding, heparin induced thrombocytopenia (HIT), all-cause mortality within 3 and 6 months. All events were adjudicated by a Central Adjudication Committee. Time-to-event outcomes were estimated by the Kalbfleisch and Prentice method to take into account the competing risk of death. Cumulative incidences were presented with corresponding 95% confidence interval (95% CI). To validate the Ottawa score, the area under the curve (AUC) and its 95% CI were calculated on receiver operating characteristic (ROC) curve analysis; the most discriminant cut-off was then determined by calculating the Youden index. Univariate and multivariate analyses were performed to identify additional predictive factors of recurrent VTE to those included in the Ottawa score using the Fine and Gray method and adjusted on factors included in the Ottawa score. Hazard ratio and their 95% CI were calculated. Results A total of 409 patients were included and analyzed on an intention-to-treat basis; the median age was 68 years and 51% of patients were males. 60.4% of patients had a PE (with or without DVT) .64% received chemotherapy at inclusion or in the month before inclusion. Lung (31.3%) and digestive track (18.3%) cancers were the most common cancer types and 67.0% had stage IV cancers. According to Ottawa score, 58% of patients were classified at high clinical probability of recurrence (score ≥ 1). During the 6 months treatment period, 23 patients had a recurrent VTE, yielding a cumulative incidence of 6.1% (95% CI 4.0-9.3) with a median time for recurrent VTE of 33 days. The recurrence rate of VTE was estimated to 7.8% (95% CI 4.9-12.5) for patients classified at high risk of recurrence according to the Ottawa score (score ≥ 1) compared to 3.8% (95%CI 1.6-8.9) for other patients (Ottawa score 〈 1). AUC of the Ottawa score was 0.60 (95% CI 0.55-0.65). In multivariable analysis, none of the potential risk factors for recurrent VTE was significantly associated with recurrent VTE at 6 months. During the 6 months treatment period, 15 patients had a major bleeding and 2 patients experienced a HIT. At 3 and 6 months, 104 and 144 patients had died yielding a cumulative incidence of 26.1%, (95% CI 21.8-30.4) and 37.8% (95% CI 32.8-42.9), respectively. The main cause of death was underlying cancer. Conclusion In this prospective cohort of patients with cancer receiving LMWH for VTE, the Ottawa score did not accurately predict recurrent VTE. No other clinical predictor of recurrent VTE was identified in this study. Disclosures Meyer: Bayer: Other: travel support; LEO pharma: Other: travel support, Research Funding; SANOFI: Other: travel support, Research Funding; BMS-Pfizer: Other: travel support, Research Funding; Boehringer Ingelheim: Research Funding. Girard:Leo Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: travel support. Scotté:LEO Pharma A/S: Honoraria, Research Funding, Speakers Bureau; Pfizer: Honoraria, Research Funding, Speakers Bureau; Tesaro: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Research Funding, Speakers Bureau; Roche: Honoraria, Research Funding, Speakers Bureau; MSD: Honoraria, Research Funding, Speakers Bureau; Pierre Fabre Oncology: Honoraria, Research Funding, Speakers Bureau. Lamblin:Leo Pharma: Employment. Laporte:Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Boston scientific: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Leo-Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Boehringer-Ingelheim: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; MSD: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Description: DiGeorge syndrome (DGS) is a primary immunodeficiency characterized by various degrees of T-cell deficiency. In partial DGS (pDGS), other risk factors could predispose to recurrent infections, autoimmunity, and allergy. The aim of this study was to assess the effect of different factors in the development of infections, autoimmunity, and/or allergy in patients with pDGS. We studied 467 pDGS patients in follow-up at Great Ormond Street Hospital. Using a multivariate approach, we observed that palatal anomalies represent a risk factor for the development of recurrent otitis media with effusion. Gastroesophageal reflux/dysphagia and asthma/rhinitis represent a risk factor for the development of recurrent upper respiratory tract infections. Allergy and autoimmunity were associated with persistently low immunoglobulin M levels and lymphopenia, respectively. Patients with autoimmunity showed lower levels of CD3+, CD3+CD4+, and naïve CD4+CD45RA+CD27+ T lymphocytes compared with pDGS patients without autoimmunity. We also observed that the physiological age-related decline of the T-cell number was slower in pDGS patients compared with age-matched controls. The age-related recovery of the T-cell number depended on a homeostatic peripheral proliferation of T cells, as suggested by an accelerated decline of the naïve T lymphocytes in pDGS as well as a more skewed T-cell repertoire in older pDGS patients. These evidences suggest that premature CD4+ T-cell aging and lymphopenia induced spontaneous peripheral T-cell proliferation might contribute to the pathogenesis of autoimmunity in patients with pDGS. Infections in these patients represent, in most of the cases, a complication of anatomical or gastroenterological anomalies rather than a feature of the underlying immunodeficiency.