[Spatio-temporal distribution of COVID-19 in Cologne and associated socio-economic factors in the period from February 2020 to October 2021]. / Die zeitlich-räumliche Verteilung von COVID-19 in Köln und beeinflussende soziale Faktoren im Zeitraum Februar 2020 bis Oktober 2021.

BACKGROUND AND GOALS: Even in the early phase of the COVID-19 pandemic, which took a very different course globally, there were indications that socio-economic factors influenced the dynamics of disease spread, which from the second phase (September 2020) onwards particularly affected people with a lower socio-economic status. Such effects can also be seen within a large city. The present study visualizes and examines the spatio-temporal spread of all COVID-19 cases reported in Cologne, Germany (February 2020-October 2021) at district level and their possible association with socio-economic factors. METHODS: Pseudonymized data of all COVID-19 cases reported in Cologne were geo-coded and their distribution was mapped in an age-standardized way at district level over four periods and compared with the distribution of social factors. The possible influence of the selected factors was also examined in a regression analysis in a model with case growth rates. RESULTS: The small-scale local infection process changed during the pandemic. Neighborhoods with weaker socio-economic indices showed higher incidence over a large part of the pandemic course, with a positive correlation between poverty risk factors and age-standardized incidence. The strength of this correlation changed over time. CONCLUSION: The timely observation and analysis of the local spread dynamics reveals the positive correlation of disadvantaging socio-economic factors on the incidence rate of COVID-19 at the level of a large city and can help steer local containment measures in a targeted manner.

Uncovering chains of infections through spatio-temporal and visual analysis of COVID-19 contact traces.

A major challenge for departments of public health (DPHs) in dealing with the ongoing COVID-19 pandemic is tracing contacts in exponentially growing SARS-CoV-2 infection clusters. Prevention of further disease spread requires a comprehensive registration of the connections between individuals and clusters. Due to the high number of infections with unknown origin, the healthcare analysts need to identify connected cases and clusters through accumulated epidemiological knowledge and the metadata of the infections in their database. Here we contribute a visual analytics dashboard to identify, assess and visualize clusters in COVID-19 contact tracing networks. Additionally, we demonstrate how graph-based machine learning methods can be used to find missing links between infection clusters and thus support the mission to get a comprehensive view on infection events. This work was developed through close collaboration with DPHs in Germany. We argue how our dashboard supports the identification of clusters by public health experts, discuss ongoing developments and possible extensions.

STAT3 gain-of-function mutations associated with autoimmune lymphoproliferative syndrome like disease deregulate lymphocyte apoptosis and can be targeted by BH3 mimetic compounds.

Autoimmune lymphoproliferative syndrome (ALPS) is typically caused by mutations in genes of the extrinsic FAS mediated apoptotic pathway, but for about 30% of ALPS-like patients the genetic diagnosis is lacking. We analyzed 30 children with ALPS-like disease of unknown cause and identified two dominant gain-of-function mutations of the Signal Transducer And Activator Of Transcription 3 (STAT3, p.R278H, p.M394T) leading to increased transcriptional activity. Hyperactivity of STAT3, a known repressor of FAS, was associated with decreased FAS-mediated apoptosis, mimicking ALPS caused by FAS mutations. Expression of BCL2 family proteins, further targets of STAT3 and regulators of the intrinsic apoptotic pathway, was disturbed. Cells with hyperactive STAT3 were consequently more resistant to intrinsic apoptotic stimuli and STAT3 inhibition alleviated this effect. Importantly, STAT3-mutant cells were more sensitive to death induced by the BCL2-inhibitor ABT-737 indicating a dependence on anti-apoptotic BCL2 proteins and potential novel therapeutic options.

Fatal Lymphoproliferative Disease in Two Siblings Lacking Functional FAAP24.

Hereditary defects in several genes have been shown to disturb the normal immune response to EBV and to give rise to severe EBV-induced lymphoproliferation in the recent years. Nevertheless, in many patients, the molecular basis of fatal EBV infection still remains unclear. The Fanconi anemia-associated protein 24 (FAAP24) plays a dual role in DNA repair. By association with FANCM as component of the FA core complex, it recruits the FA core complex to damaged DNA. Additionally, FAAP24 has been shown to evoke ATR-mediated checkpoint responses independently of the FA core complex. By whole exome sequencing, we identified a homozygous missense mutation in the FAAP24 gene (cC635T, pT212M) in two siblings of a consanguineous Turkish family who died from an EBV-associated lymphoproliferative disease after infection with a variant EBV strain, expressing a previously unknown EBNA2 allele.In order to analyze the functionality of the variant FAAP24 allele, we used herpes virus saimiri-transformed patient T cells to test endogenous cellular FAAP24 functions that are known to be important in DNA damage control. We saw an impaired FANCD2 monoubiquitination as well as delayed checkpoint responses, especially affecting CHK1 phosphorylation in patient samples in comparison to healthy controls. The phenotype of this FAAP24 mutation might have been further accelerated by an EBV strain that harbors an EBNA2 allele with enhanced activities compared to the prototype laboratory strain B95.8. This is the first report of an FAAP24 loss of function mutation found in human patients with EBV-associated lymphoproliferation.

Deregulation of Fas ligand expression as a novel cause of autoimmune lymphoproliferative syndrome-like disease.

Autoimmune lymphoproliferative syndrome is frequently caused by mutations in genes involved in the Fas death receptor pathway, but for 20-30% of patients the genetic defect is unknown. We observed that treatment of healthy T cells with interleukin-12 induces upregulation of Fas ligand and Fas ligand-dependent apoptosis. Consistently, interleukin-12 could not induce apoptosis in Fas ligand-deficient T cells from patients with autoimmune lymphoproliferative syndrome. We hypothesized that defects in the interleukin-12 signaling pathway may cause a similar phenotype as that caused by mutations of the Fas ligand gene. To test this, we analyzed 20 patients with autoimmune lymphoproliferative syndrome of unknown cause by whole-exome sequencing. We identified a homozygous nonsense mutation (c.698G>A, p.R212*) in the interleukin-12/interleukin-23 receptor-component IL12RB1 in one of these patients. The mutation led to IL12RB1 protein truncation and loss of cell surface expression. Interleukin-12 and -23 signaling was completely abrogated as demonstrated by deficient STAT4 phosphorylation and interferon γ production. Interleukin-12-mediated expression of membrane-bound and soluble Fas ligand was lacking and basal expression was much lower than in healthy controls. The patient presented with the classical symptoms of autoimmune lymphoproliferative syndrome: chronic non-malignant, non-infectious lymphadenopathy, splenomegaly, hepatomegaly, elevated numbers of double-negative T cells, autoimmune cytopenias, and increased levels of vitamin B12 and interleukin-10. Sanger sequencing and whole-exome sequencing excluded the presence of germline or somatic mutations in genes known to be associated with the autoimmune lymphoproliferative syndrome. Our data suggest that deficient regulation of Fas ligand expression by regulators such as the interleukin-12 signaling pathway may be an alternative cause of autoimmune lymphoproliferative syndrome-like disease.

Next-generation-sequencing-based risk stratification and identification of new genes involved in structural and sequence variations in near haploid lymphoblastic leukemia.

Near haploidy (23-29 chromosomes) is a numerical cytogenetic aberration in childhood acute lymphoblastic leukemia (ALL) associated with particularly poor outcome. In contrast, high hyperdiploidy (51-67 chromosomes) has a favorable prognosis. Correct classification and appropriate risk stratification of near haploidy is frequently hampered by the presence of apparently high hyperdiploid clones that arise by endoreduplication of the original near haploid clone. We evaluated next-generation-sequencing (NGS) to distinguish between "high hyperdiploid" leukemic clones of near haploid and true high hyperdiploid origin. Five high hyperdiploid ALL cases and the "high hyperdiploid" cell line MHH-CALL-2, derived from a near haploid clone, were tested for uniparental isodisomy. NGS showed that all disomic chromosomes of MHH-CALL-2, but none of the patients, were of uniparental origin, thus reliably discriminating these subtypes. Whole-exome- and whole-genome-sequencing of MHH-CALL-2 revealed homozygous non-synonymous coding mutations predicted to be deleterious for the protein function of 63 genes, among them known cancer-associated genes, such as FANCA, NF1, TCF7L2, CARD11, EP400, histone demethylases, and transferases (KDM6B, KDM1A, PRDM11). Only eight of these were also, but heterozygously, mutated in the high hyperdiploid patients. Structural variations in MHH-CALL-2 include a homozygous deletion (MTAP/CDKN2A/CDKN2B/ANRIL), a homozygous inversion (NCKAP5), and an unbalanced translocation (FAM189A1). Together, the sequence variations provide MHH-CALL-2 with capabilities typically acquired during cancer development, e.g., loss of cell cycle control, enhanced proliferation, lack of DNA repair, cell death evasion, and disturbance of epigenetic gene regulation. Poorer prognosis of near haploid ALL most likely results from full penetrance of a large array of detrimental homozygous mutations.

Combined immunodeficiency with life-threatening EBV-associated lymphoproliferative disorder in patients lacking functional CD27.

CD27, a tumor necrosis factor receptor family member, interacts with CD70 and influences T-, B- and NK-cell functions. Disturbance of this axis impairs immunity and memory generation against viruses including Epstein Barr virus (EBV), influenza, and others. CD27 is commonly used as marker of memory B cells for the classification of B-cell deficiencies including common variable immune deficiency. Flow cytometric immunophenotyping including expression analysis of CD27 on lymphoid cells was followed by capillary sequencing of CD27 in index patients, their parents, and non-affected siblings. More comprehensive genetic analysis employed single nucleotide polymorphism-based homozygosity mapping and whole exome sequencing. Analysis of exome sequencing data was performed at two centers using slightly different data analysis pipelines, each based on the Genome Analysis ToolKit Best Practice version 3 recommendations. A comprehensive clinical characterization was correlated to genotype. We report the simultaneous confirmation of human CD27 deficiency in 3 independent families (8 patients) due to a homozygous mutation (p. Cys53Tyr) revealed by whole exome sequencing, leading to disruption of an evolutionarily conserved cystein knot motif of the transmembrane receptor. Phenotypes varied from asymptomatic memory B-cell deficiency (n=3) to EBV-associated hemophagocytosis and lymphoproliferative disorder (LPD; n=3) and malignant lymphoma (n=2; +1 after LPD). Following EBV infection, hypogammaglobulinemia developed in at least 3 of the affected individuals, while specific anti-viral and anti-polysaccharide antibodies and EBV-specific T-cell responses were detectable. In severely affected patients, numbers of iNKT cells and NK-cell function were reduced. Two of 8 patients died, 2 others underwent allogeneic hematopoietic stem cell transplantation successfully, and one received anti-CD20 (rituximab) therapy repeatedly. Since homozygosity mapping and exome sequencing did not reveal additional modifying factors, our findings suggest that lack of functional CD27 predisposes towards a combined immunodeficiency associated with potentially fatal EBV-driven hemo-phagocytosis, lymphoproliferation, and lymphoma development.

Symptom diaries as a digital tool to detect SARS-CoV-2 infections and differentiate between prevalent variants.

The COVID-19 pandemic and the high numbers of infected individuals pose major challenges for public health departments. To overcome these challenges, the health department in Cologne has developed a software called DiKoMa. This software offers the possibility to track contact and index persons, but also provides a digital symptom diary. In this work, the question of whether these can also be used for diagnostic purposes will be investigated. Machine learning makes it possible to identify infections based on early symptom profiles and to distinguish between the predominant dominant variants. Focusing on the occurrence of the symptoms in the first week, a decision tree is trained for the differentiation between contact and index persons and the prevailing dominant variants (Wildtype, Alpha, Delta, and Omicron). The model is evaluated, using sex- and age-stratified cross-validation and validated by symptom profiles of the first 6 days. The variants achieve an AUC-ROC from 0.89 for Omicron and 0.6 for Alpha. No significant differences are observed for the results of the validation set (Alpha 0.63 and Omicron 0.87). The evaluation of symptom combinations using artificial intelligence can determine the individual risk for the presence of a COVID-19 infection, allows assignment to virus variants, and can contribute to the management of epidemics and pandemics on a national and international level. It can help to reduce the number of specific tests in times of low labor capacity and could help to early identify new virus variants.

Mutated SON putatively causes a cancer syndrome comprising high-risk medulloblastoma combined with café-au-lait spots.

Medulloblastoma is the most frequent malignant brain tumor in childhood. This highly malignant neoplasm occurs usually before 10 years of age and more frequently in boys. The 5-year event-free survival rate for high-risk medulloblastoma is low at 62% despite a multimodal therapy including surgical resection, radiation therapy and chemotherapy. We report the case of a boy, who was born to consanguineous parents. Prominently, he had multiple café-au-lait spots. At the age of 3 years he was diagnosed with a high-risk metastatic medulloblastoma. The patient died only 11 months after diagnosis of a fulminant relapse presenting as meningeal and spinal dissemination. Whole-exome sequencing of germline DNA was employed to detect the underlying mutation for this putative cancer syndrome presenting with the combination of medulloblastoma and skin alterations. After screening all possible homozygous gene SNVs, we identified a mutation of SON, an essential protein in cell cycle regulation and cell proliferation, as the most likely genetic cause.

Pediatric ALL relapses after allo-SCT show high individuality, clonal dynamics, selective pressure, and druggable targets.

Survival of patients with pediatric acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation (allo-SCT) is mainly compromised by leukemia relapse, carrying dismal prognosis. As novel individualized therapeutic approaches are urgently needed, we performed whole-exome sequencing of leukemic blasts of 10 children with post-allo-SCT relapses with the aim of thoroughly characterizing the mutational landscape and identifying druggable mutations. We found that post-allo-SCT ALL relapses display highly diverse and mostly patient-individual genetic lesions. Moreover, mutational cluster analysis showed substantial clonal dynamics during leukemia progression from initial diagnosis to relapse after allo-SCT. Only very few alterations stayed constant over time. This dynamic clonality was exemplified by the detection of thiopurine resistance-mediating mutations in the nucleotidase NT5C2 in 3 patients' first relapses, which disappeared in the post-allo-SCT relapses on relief of selective pressure of maintenance chemotherapy. Moreover, we identified TP53 mutations in 4 of 10 patients after allo-SCT, reflecting acquired chemoresistance associated with selective pressure of prior antineoplastic treatment. Finally, in 9 of 10 children's post-allo-SCT relapse, we found alterations in genes for which targeted therapies with novel agents are readily available. We could show efficient targeting of leukemic blasts by APR-246 in 2 patients carrying TP53 mutations. Our findings shed light on the genetic basis of post-allo-SCT relapse and may pave the way for unraveling novel therapeutic strategies in this challenging situation.

EBV Negative Lymphoma and Autoimmune Lymphoproliferative Syndrome Like Phenotype Extend the Clinical Spectrum of Primary Immunodeficiency Caused by STK4 Deficiency.

Serine/threonine kinase 4 (STK4) deficiency is an autosomal recessive genetic condition that leads to primary immunodeficiency (PID) typically characterized by lymphopenia, recurrent infections and Epstein Barr Virus (EBV) induced lymphoproliferation and -lymphoma. State-of-the-art treatment regimens consist of prevention or treatment of infections, immunoglobulin substitution (IVIG) and restoration of the immune system by hematopoietic stem cell transplantation. Here, we report on two patients from two consanguineous families of Turkish (patient P1) and Moroccan (patient P2) decent, with PID due to homozygous STK4 mutations. P1 harbored a previously reported frameshift (c.1103 delT, p.M368RfsX2) and P2 a novel splice donor site mutation (P2; c.525+2 T>G). Both patients presented in childhood with recurrent infections, CD4 lymphopenia and dysregulated immunoglobulin levels. Patient P1 developed a highly malignant B cell lymphoma at the age of 10 years and a second, independent Hodgkin lymphoma 5 years later. To our knowledge she is the first STK4 deficient case reported who developed lymphoma in the absence of detectable EBV or other common viruses. Lymphoma development may be due to the lacking tumor suppressive function of STK4 or the perturbed immune surveillance due to the lack of CD4+ T cells. Our data should raise physicians' awareness of [1] lymphoma proneness of STK4 deficient patients even in the absence of EBV infection and [2] possibly underlying STK4 deficiency in pediatric patients with a history of recurrent infections, CD4 lymphopenia and lymphoma and unknown genetic make-up. Patient P2 experienced recurrent otitis in childhood, but when she presented at the age of 14, she showed clinical and immunological characteristics similar to patients suffering from Autoimmune Lymphoproliferative Syndrome (ALPS): elevated DNT cell number, non-malignant lymphadenopathy and hepatosplenomegaly, hematolytic anemia, hypergammaglobulinemia. Also patient P1 presented with ALPS-like features (lymphadenopathy, elevated DNT cell number and increased Vitamin B12 levels) and both were initially clinically diagnosed as ALPS-like. Closer examination of P2, however, revealed active EBV infection and genetic testing identified a novel STK4 mutation. None of the patients harbored typically ALPS-associated mutations of the Fas receptor mediated apoptotic pathway and Fas-mediated apoptosis was not affected. The presented case reports extend the clinical spectrum of STK4 deficiency.

Congenital embryonal rhabdomyosarcoma caused by heterozygous concomitant PTCH1 and PTCH2 germline mutations.

The sonic hedgehog (SHH) signaling pathway has been shown to play important roles in embryogenesis, cell proliferation as well as in cell differentiation. It is aberrantly activated in various common cancers in adults, but also in pediatric neoplasms, such as rhabdomyosarcoma (RMS) and atypical teratoid/rhabdoid tumors (AT/RTs). Dysregulation and germline mutation in PATCHED1 (PTCH1), a receptor for SHH, is responsible for the Gorlin Syndrome, a familial cancer predisposing syndrome including RMS. Here, we report a newborn diagnosed with congenital embryonal RMS. Whole-exome sequencing (WES) identified the presence of two heterozygous germline mutations in two target genes of the SHH signaling pathway. The PTCH1 mutation p.(Gly38Glu) is inherited from the mother, whereas the PTCH2 p.(His622Tyr) mutation is transmitted from the father. Quantitative RT-PCR expression analysis of GLI and SMO, key players of the SHH pathway, showed significantly increase in the tumor tissue of the patient and also enrichment in the germline sample in comparison to the parents indicating activation of the SHH pathway in the patient. These findings demonstrate that SHH pathway activity seems to play a role in eRMS as evidenced by high expression levels of GLI1 RNA transcripts. We speculate that PTCH2 modulates tumorigenesis linked to the PTCH1 mutation and is likely associated with the congenital onset of the RMS observed in our patient.

Diagnostic challenges in a child with early onset desmoplastic medulloblastoma and homozygous variants in MSH2 and MSH6.

Constitutional mismatch repair deficiency (CMMRD) is an autosomal recessively inherited childhood cancer susceptibility syndrome caused by biallelic germline mutations in one of the mismatch repair (MMR) genes. The spectrum of CMMRD-associated tumours is very broad and many CMMRD patients additionally display signposting non-neoplastic features, most frequently café-au-lait macules and other pigmentation alterations. We report on a 13-month-old girl suspected of having CMMRD due to a desmoplastic medulloblastoma and a striking skin pigmentation that included multiple café-au-lait macules, hypopigmented areas and Mongolian spots. Whole-exome sequencing revealed homozygosity for MSH2 variant p.(Leu92Val) and MSH6 variant p.(Val809del), both variants of uncertain significance (VUS). Immunohistochemical analysis of the tumour tissue showed expression of all four MMR proteins and gMSI testing was negative. However, functional assays demonstrated that the cells of the patient displayed methylation tolerance and ex vivo microsatellite instability, which unequivocally confirmed the diagnosis of CMMRD. Taken together, the results render the MSH2 variant unlikely to be responsible for the phenotype, while they are compatible with MSH6-associated CMMRD. This case illustrates the diagnostic strategy of confirming CMMRD syndrome in patients with VUS.

Loss of Pax5 Exploits Sca1-BCR-ABLp190 Susceptibility to Confer the Metabolic Shift Essential for pB-ALL.

Preleukemic clones carrying BCR-ABLp190 oncogenic lesions are found in neonatal cord blood, where the majority of preleukemic carriers do not convert into precursor B-cell acute lymphoblastic leukemia (pB-ALL). However, the critical question of how these preleukemic cells transform into pB-ALL remains undefined. Here, we model a BCR-ABLp190 preleukemic state and show that limiting BCR-ABLp190 expression to hematopoietic stem/progenitor cells (HS/PC) in mice (Sca1-BCR-ABLp190) causes pB-ALL at low penetrance, which resembles the human disease. pB-ALL blast cells were BCR-ABL-negative and transcriptionally similar to pro-B/pre-B cells, suggesting disease onset upon reduced Pax5 functionality. Consistent with this, double Sca1-BCR-ABLp190+Pax5+/- mice developed pB-ALL with shorter latencies, 90% incidence, and accumulation of genomic alterations in the remaining wild-type Pax5 allele. Mechanistically, the Pax5-deficient leukemic pro-B cells exhibited a metabolic switch toward increased glucose utilization and energy metabolism. Transcriptome analysis revealed that metabolic genes (IDH1, G6PC3, GAPDH, PGK1, MYC, ENO1, ACO1) were upregulated in Pax5-deficient leukemic cells, and a similar metabolic signature could be observed in human leukemia. Our studies unveil the first in vivo evidence that the combination between Sca1-BCR-ABLp190 and metabolic reprogramming imposed by reduced Pax5 expression is sufficient for pB-ALL development. These findings might help to prevent conversion of BCR-ABLp190 preleukemic cells.Significance: Loss of Pax5 drives metabolic reprogramming, which together with Sca1-restricted BCR-ABL expression enables leukemic transformation. Cancer Res; 78(10); 2669-79. ©2018 AACR.

A novel approach to detect resistance mechanisms reveals FGR as a factor mediating HDAC inhibitor SAHA resistance in B-cell lymphoma.

Histone deacetylase (HDAC) inhibitors such as suberoylanilide hydroxamic acid (SAHA) are not commonly used in clinical practice for treatment of B-cell lymphomas, although a subset of patients with refractory or relapsed B-cell lymphoma achieved partial or complete remissions. Therefore, the purpose of this study was to identify molecular features that predict the response of B-cell lymphomas to SAHA treatment. We designed an integrative approach combining drug efficacy testing with exome and captured target analysis (DETECT). In this study, we tested SAHA sensitivity in 26 B-cell lymphoma cell lines and determined SAHA-interacting proteins in SAHA resistant and sensitive cell lines employing a SAHA capture compound (CC) and mass spectrometry (CCMS). In addition, we performed exome mutation analysis. Candidate validation was done by expression analysis and knock-out experiments. An integrated network analysis revealed that the Src tyrosine kinase Gardner-Rasheed feline sarcoma viral (v-fgr) oncogene homolog (FGR) is associated with SAHA resistance. FGR was specifically captured by the SAHA-CC in resistant cells. In line with this observation, we found that FGR expression was significantly higher in SAHA resistant cell lines. As functional proof, CRISPR/Cas9 mediated FGR knock-out in resistant cells increased SAHA sensitivity. In silico analysis of B-cell lymphoma samples (n = 1200) showed a wide range of FGR expression indicating that FGR expression might help to stratify patients, which clinically benefit from SAHA therapy. In conclusion, our comprehensive analysis of SAHA-interacting proteins highlights FGR as a factor involved in SAHA resistance in B-cell lymphoma.

Next-generation-sequencing of recurrent childhood high hyperdiploid acute lymphoblastic leukemia reveals mutations typically associated with high risk patients.

20% of children suffering from high hyperdiploid acute lymphoblastic leukemia develop recurrent disease. The molecular mechanisms are largely unknown. Here, we analyzed the genetic landscape of five patients at relapse, who developed recurrent disease without prior high-risk indication using whole-exome- and whole-genome-sequencing. Oncogenic mutations of RAS pathway genes (NRAS, KRAS, FLT3, n=4) and deactivating mutations of major epigenetic regulators (CREBBP, EP300, each n=2 and ARID4B, EZH2, MACROD2, MLL2, each n=1) were prominent in these cases and virtually absent in non-recurrent cases (n=6) or other pediatric acute lymphoblastic leukemia cases (n=18). In relapse nucleotide variations were detected in cell fate determining transcription factors (GLIS1, AKNA). Structural genomic alterations affected genes regulating B-cell development (IKZF1, PBX1, RUNX1). Eleven novel translocations involved the genes ART4, C12orf60, MACROD2, TBL1XR1, LRRN4, KIAA1467, and ELMO1/MIR1200. Typically, patients harbored only single structural variations, except for one patient who displayed massive rearrangements in the context of a germline tumor suppressor TP53 mutation and a Li-Fraumeni syndrome-like family history. Another patient harbored a germline mutation in the DNA repair factor ATM. In summary, the relapse patients of our cohort were characterized by somatic mutations affecting the RAS pathway, epigenetic and developmental programs and germline mutations in DNA repair pathways.

Infection Exposure is a Causal Factor in B-cell Precursor Acute Lymphoblastic Leukemia as a Result of Pax5-Inherited Susceptibility.

UNLABELLED: Earlier in the past century, infections were regarded as the most likely cause of childhood B-cell precursor acute lymphoblastic leukemia (pB-ALL). However, there is a lack of relevant biologic evidence supporting this hypothesis. We present in vivo genetic evidence mechanistically connecting inherited susceptibility to pB-ALL and postnatal infections by showing that pB-ALL was initiated in Pax5 heterozygous mice only when they were exposed to common pathogens. Strikingly, these murine pB-ALLs closely resemble the human disease. Tumor exome sequencing revealed activating somatic, nonsynonymous mutations of Jak3 as a second hit. Transplantation experiments and deep sequencing suggest that inactivating mutations in Pax5 promote leukemogenesis by creating an aberrant progenitor compartment that is susceptible to malignant transformation through accumulation of secondary Jak3 mutations. Thus, treatment of Pax5(+/-) leukemic cells with specific JAK1/3 inhibitors resulted in increased apoptosis. These results uncover the causal role of infection in pB-ALL development. SIGNIFICANCE: These results demonstrate that delayed infection exposure is a causal factor in pB-ALL. Therefore, these findings have critical implications for the understanding of the pathogenesis of leukemia and for the development of novel therapies for this disease.