Genetic alterations in lymphoblastic leukaemia / lymphoma - a practical guide to WHO HAEM5.

We present a practical guide for analyzing the genetic aspects of lymphoblastic leukaemia/lymphoma according to the 5th edition of the World Health Organization (WHO) classification of haematolymphoid neoplasms (WHO-HAEM5) issued in 2024. The WHO-HAEM5 acknowledges the increasing importance of genetics in the diagnosis of lymphoid neoplasia. Classification is based on the established genetic subtypes according to cell lineage, with precursor cell neoplasms followed by mature malignancies. This guide describes those genetic abnormalities in acute precursor B- and T-cell neoplasms required for risk stratification, and for treatment, providing diagnostic algorithms under the headings of 'essential' and 'desirable' diagnostic criteria.

The experiences of gender and sexually diverse parents using support and services for their young children: An integrative review.

AIM: To address: What are the experiences of 2SLGBTQQIA+ parents using parenting supports and services to meet their children's early childhood development needs (<5 years of age)? DESIGN: Whittemore and Knafl's (2005) integrative review methodology. METHODS: Electronic databases were searched from 2000 to October 14, 2022 for empirical studies or reviews addressing the research question. The title and abstract of 12,158 articles were screened for inclusion in the review by two independent researchers; 175 of these articles underwent full-text review. Studies selected were critically appraised using a Joanna Briggs Institute Critical Appraisal tool. Relevant key findings were extracted from each study and entered into N-VIVO-12. Thematic content analysis was employed and PRISMA guidelines were adhered to. RESULTS: A total of 18 articles (15 qualitative and three multi-method studies) met the inclusion criteria and were selected for the review. Seven themes were revealed from analysis of the studies: (1) 2SLGBTQQIA+ Status kept a secret; (2) Forced to come out; (3) Heteronormative messaging; (4) Feeling excluded; (5) Stigmatised; (6) Parents act as educators; and (7) Positive experiences. CONCLUSION: This integrative review provides nurses with insight into the experiences of 2SLGBTQQIA+ parents using health care services for their young child. IMPLICATIONS FOR THE PROFESSION: This article highlights what changes nurses need to make to their practice to ensure appropriate, inclusive care for clients of diverse sexual and gender identities and their families. IMPACT: Health care providers, especially nurses, have an opportunity to improve the experiences of these families and positively impact their health and well-being. Additionally, there is a need for research with the 2SLGBTQQIA+ parent community and the use of rigorous methodological techniques, including clearly linking participants' gender and sexual identities with study findings, to improve our understanding of 2SLGBTQQIA+ parent experiences. PATIENT OR PUBLIC CONTRIBUTION: Although there was no direct patient contribution to the work since it was an integrative review of the literature, indirectly patient contributions are incorporated from the original research results of studies incorporated into this review.

Broad H3K4me3 domains: Maintaining cellular identity and their implication in super-enhancer hijacking.

The human and mouse genomes are complex from a genomic standpoint. Each cell has the same genomic sequence, yet a wide array of cell types exists due to the presence of a plethora of regulatory elements in the non-coding genome. Recent advances in epigenomic profiling have uncovered non-coding gene proximal promoters and distal enhancers of transcription genome-wide. Extension of promoter-associated H3K4me3 histone mark across the gene body, known as a broad H3K4me3 domain (H3K4me3-BD), is a signature of constitutive expression of cell-type-specific regulation and of tumour suppressor genes in healthy cells. Recently, it has been discovered that the presence of H3K4me3-BDs over oncogenes is a cancer-specific feature associated with their dysregulated gene expression and tumourigenesis. Moreover, it has been shown that the hijacking of clusters of enhancers, known as super-enhancers (SE), by proto-oncogenes results in the presence of H3K4me3-BDs over the gene body. Therefore, H3K4me3-BDs and SE crosstalk in healthy and cancer cells therefore represents an important mechanism to identify future treatments for patients with SE driven cancers.

Whole genome sequencing provides comprehensive genetic testing in childhood B-cell acute lymphoblastic leukaemia.

Childhood B-cell acute lymphoblastic leukaemia (B-ALL) is characterised by recurrent genetic abnormalities that drive risk-directed treatment strategies. Using current techniques, accurate detection of such aberrations can be challenging, due to the rapidly expanding list of key genetic abnormalities. Whole genome sequencing (WGS) has the potential to improve genetic testing, but requires comprehensive validation. We performed WGS on 210 childhood B-ALL samples annotated with clinical and genetic data. We devised a molecular classification system to subtype these patients based on identification of key genetic changes in tumour-normal and tumour-only analyses. This approach detected 294 subtype-defining genetic abnormalities in 96% (202/210) patients. Novel genetic variants, including fusions involving genes in the MAP kinase pathway, were identified. WGS results were concordant with standard-of-care methods and whole transcriptome sequencing (WTS). We expanded the catalogue of genetic profiles that reliably classify PAX5alt and ETV6::RUNX1-like subtypes. Our novel bioinformatic pipeline improved detection of DUX4 rearrangements (DUX4-r): a good-risk B-ALL subtype with high survival rates. Overall, we have validated that WGS provides a standalone, reliable genetic test to detect all subtype-defining genetic abnormalities in B-ALL, accurately classifying patients for the risk-directed treatment stratification, while simultaneously performing as a research tool to identify novel disease biomarkers.

Molecular characterization and clinical outcome of B-cell precursor acute lymphoblastic leukemia with IG-MYC rearrangement.

Rarely, immunophenotypically immature B-cell precursor acute lymphoblastic leukemia (BCP-ALL) carries an immunoglobulin- MYC rearrangement (IG-MYC-r). This can result in diagnostic confusion with Burkitt lymphoma/leukemia and use of individualized treatment schedules of unproven efficacy. Here we compare the molecular characteristics of these conditions and investigate historic clinical outcome data. We identified 90 cases registered in a national BCP-ALL clinical trial/registry. When present, diagnostic material underwent cytogenetic, exome, methylome and transcriptome analyses. The outcomes analyzed were 3-year event-free survival and overall survival. IG-MYC-r was identified in diverse cytogenetic backgrounds, co-existing with either established BCP-ALL-specific abnormalities (high hyperdiploidy, n=3; KMT2A-rearrangement, n=6; iAMP21, n=1; BCR-ABL1, n=1); BCL2/BCL6-rearrangements (n=15); or, most commonly, as the only defining feature (n=64). Within this final group, precursor-like V(D)J breakpoints predominated (8/9) and KRAS mutations were common (5/11). DNA methylation identified a cluster of V(D)J-rearranged cases, clearly distinct from Burkitt leukemia/lymphoma. Children with IG-MYC-r within that subgroup had a 3-year event-free survival of 47% and overall survival of 60%, representing a high-risk BCP-ALL. To develop effective management strategies this group of patients must be allowed access to contemporary, minimal residual disease-adapted, prospective clinical trial protocols.

Integrative genomic analysis of childhood acute lymphoblastic leukaemia lacking a genetic biomarker in the UKALL2003 clinical trial.

Incorporating genetics into risk-stratification for treatment of childhood B-progenitor acute lymphoblastic leukaemia (B-ALL) has contributed significantly to improved survival. In about 30% B-ALL (B-other-ALL) without well-established chromosomal changes, new genetic subtypes have recently emerged, yet their true prognostic relevance largely remains unclear. We integrated next generation sequencing (NGS): whole genome sequencing (WGS) (n = 157) and bespoke targeted NGS (t-NGS) (n = 175) (overlap n = 36), with existing genetic annotation in a representative cohort of 351 B-other-ALL patients from the childhood ALL trail, UKALL2003. PAX5alt was most frequently observed (n = 91), whereas PAX5 P80R mutations (n = 11) defined a distinct PAX5 subtype. DUX4-r subtype (n = 80) was defined by DUX4 rearrangements and/or ERG deletions. These patients had a low relapse rate and excellent survival. ETV6::RUNX1-like subtype (n = 21) was characterised by multiple abnormalities of ETV6 and IKZF1, with no reported relapses or deaths, indicating their excellent prognosis in this trial. An inferior outcome for patients with ABL-class fusions (n = 25) was confirmed. Integration of NGS into genomic profiling of B-other-ALL within a single childhood ALL trial, UKALL2003, has shown the added clinical value of NGS-based approaches, through improved accuracy in detection and classification into the range of risk stratifying genetic subtypes, while validating their prognostic significance.

hiPSC-derived bone marrow milieu identifies a clinically actionable driver of niche-mediated treatment resistance in leukemia.

Leukemia cells re-program their microenvironment to augment blast proliferation and enhance treatment resistance. Means of clinically targeting such niche-driven treatment resistance remain ambiguous. We develop human induced pluripotent stem cell (hiPSC)-engineered niches to reveal druggable cancer-niche dependencies. We reveal that mesenchymal (iMSC) and vascular niche-like (iANG) hiPSC-derived cells support ex vivo proliferation of patient-derived leukemia cells, affect dormancy, and mediate treatment resistance. iMSCs protect dormant and cycling blasts against dexamethasone, while iANGs protect only dormant blasts. Leukemia proliferation and protection from dexamethasone-induced apoptosis is dependent on cancer-niche interactions mediated by CDH2. Consequently, we test CDH2 antagonist ADH-1 (previously in Phase I/II trials for solid tumors) in a very aggressive patient-derived xenograft leukemia mouse model. ADH-1 shows high in vivo efficacy; ADH-1/dexamethasone combination is superior to dexamethasone alone, with no ADH-1-conferred additional toxicity. These findings provide a proof-of-concept starting point to develop improved, potentially safer therapeutics targeting niche-mediated cancer dependencies in blood cancers.

High-resolution simulations of chromatin folding at genomic rearrangements in malignant B cells provide mechanistic insights into proto-oncogene deregulation.

Genomic rearrangements are known to result in proto-oncogene deregulation in many cancers, but the link to 3D genome structure remains poorly understood. Here, we used the highly predictive heteromorphic polymer (HiP-HoP) model to predict chromatin conformations at the proto-oncogene CCND1 in healthy and malignant B cells. After confirming that the model gives good predictions of Hi-C data for the nonmalignant human B cell-derived cell line GM12878, we generated predictions for two cancer cell lines, U266 and Z-138. These possess genome rearrangements involving CCND1 and the immunoglobulin heavy locus (IGH), which we mapped using targeted genome sequencing. Our simulations showed that a rearrangement in U266 cells where a single IGH super-enhancer is inserted next to CCND1 leaves the local topologically associated domain (TAD) structure intact. We also observed extensive changes in enhancer-promoter interactions within the TAD, suggesting that it is the downstream chromatin remodeling which gives rise to the oncogene activation, rather than the presence of the inserted super-enhancer DNA sequence per se. Simulations of the IGH-CCND1 reciprocal translocation in Z-138 cells revealed that an oncogenic fusion TAD is created, encompassing CCND1 and the IGH super-enhancers. We predicted how the structure and expression of CCND1 changes in these different cell lines, validating this using qPCR and fluorescence in situ hybridization microscopy. Our work demonstrates the power of polymer simulations to predict differences in chromatin interactions and gene expression for different translocation breakpoints.

Epigenetic regulator genes direct lineage switching in MLL/AF4 leukemia.

The fusion gene MLL/AF4 defines a high-risk subtype of pro-B acute lymphoblastic leukemia. Relapse can be associated with a lineage switch from acute lymphoblastic to acute myeloid leukemia, resulting in poor clinical outcomes caused by resistance to chemotherapies and immunotherapies. In this study, the myeloid relapses shared oncogene fusion breakpoints with their matched lymphoid presentations and originated from various differentiation stages from immature progenitors through to committed B-cell precursors. Lineage switching is linked to substantial changes in chromatin accessibility and rewiring of transcriptional programs, including alternative splicing. These findings indicate that the execution and maintenance of lymphoid lineage differentiation is impaired. The relapsed myeloid phenotype is recurrently associated with the altered expression, splicing, or mutation of chromatin modifiers, including CHD4 coding for the ATPase/helicase of the nucleosome remodelling and deacetylation complex. Perturbation of CHD4 alone or in combination with other mutated epigenetic modifiers induces myeloid gene expression in MLL/AF4+ cell models, indicating that lineage switching in MLL/AF4 leukemia is driven and maintained by disrupted epigenetic regulation.

Dynamics of broad H3K4me3 domains uncover an epigenetic switch between cell identity and cancer-related genes.

Broad domains of H3K4 methylation have been associated with consistent expression of tissue-specific, cell identity, and tumor suppressor genes. Here, we identified broad domain-associated genes in healthy human thymic T cell populations and a collection of T cell acute lymphoblastic leukemia (T-ALL) primary samples and cell lines. We found that broad domains are highly dynamic throughout T cell differentiation, and their varying breadth allows the distinction between normal and neoplastic cells. Although broad domains preferentially associate with cell identity and tumor suppressor genes in normal thymocytes, they flag key oncogenes in T-ALL samples. Moreover, the expression of broad domain-associated genes, both coding and noncoding, is frequently deregulated in T-ALL. Using two distinct leukemic models, we showed that the ectopic expression of T-ALL oncogenic transcription factor preferentially impacts the expression of broad domain-associated genes in preleukemic cells. Finally, an H3K4me3 demethylase inhibitor differentially targets T-ALL cell lines depending on the extent and number of broad domains. Our results show that the regulation of broad H3K4me3 domains is associated with leukemogenesis, and suggest that the presence of these structures might be used for epigenetic prioritization of cancer-relevant genes, including long noncoding RNAs.

Epigenomic translocation of H3K4me3 broad domains over oncogenes following hijacking of super-enhancers.

Chromosomal translocations are important drivers of haematological malignancies whereby proto-oncogenes are activated by juxtaposition with enhancers, often called enhancer hijacking We analyzed the epigenomic consequences of rearrangements between the super-enhancers of the immunoglobulin heavy locus (IGH) and proto-oncogene CCND1 that are common in B cell malignancies. By integrating BLUEPRINT epigenomic data with DNA breakpoint detection, we characterized the normal chromatin landscape of the human IGH locus and its dynamics after pathological genomic rearrangement. We detected an H3K4me3 broad domain (BD) within the IGH locus of healthy B cells that was absent in samples with IGH-CCND1 translocations. The appearance of H3K4me3-BD over CCND1 in the latter was associated with overexpression and extensive chromatin accessibility of its gene body. We observed similar cancer-specific H3K4me3-BDs associated with hijacking of super-enhancers of other common oncogenes in B cell (MAF, MYC, and FGFR3/NSD2) and T cell malignancies (LMO2, TLX3, and TAL1). Our analysis suggests that H3K4me3-BDs can be created by super-enhancers and supports the new concept of epigenomic translocation, in which the relocation of H3K4me3-BDs from cell identity genes to oncogenes accompanies the translocation of super-enhancers.

Chemotherapy induces canalization of cell state in childhood B-cell precursor acute lymphoblastic leukemia.

Comparison of intratumor genetic heterogeneity in cancer at diagnosis and relapse suggests that chemotherapy induces bottleneck selection of subclonal genotypes. However, evolutionary events subsequent to chemotherapy could also explain changes in clonal dominance seen at relapse. We, therefore, investigated the mechanisms of selection in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) during induction chemotherapy where maximal cytoreduction occurs. To distinguish stochastic versus deterministic events, individual leukemias were transplanted into multiple xenografts and chemotherapy administered. Analyses of the immediate post-treatment leukemic residuum at single-cell resolution revealed that chemotherapy has little impact on genetic heterogeneity. Rather, it acts on extensive, previously unappreciated, transcriptional and epigenetic heterogeneity in BCP-ALL, dramatically reducing the spectrum of cell states represented, leaving a genetically polyclonal but phenotypically uniform population with hallmark signatures relating to developmental stage, cell cycle and metabolism. Hence, canalization of cell state accounts for a significant component of bottleneck selection during induction chemotherapy.

Staff-perceived barriers to nutrition intervention in substance use disorder treatment.

OBJECTIVE: While organisational change in substance use disorder (SUD) treatment has been extensively studied, there is no research describing facility-wide changes related to nutrition interventions. This study evaluates staff-perceived barriers to change before and after a wellness initiative. DESIGN: A pre-intervention questionnaire was administered to participating staff prior to facility-wide changes (n 40). The questions were designed to assess barriers across five domains: (1) provision of nutrition-related treatment; (2) implementation of nutrition education; (3) screening, detecting and monitoring (nutrition behaviours); (4) facility-wide collaboration and (5) menu changes and client satisfaction. A five-point Likert scale was used to indicate the extent to which staff anticipate difficulty or ease in implementing facility-wide nutrition changes, perceived as organisational barriers. Follow-up questionnaires were identical to the pre-test except that it examined barriers experienced, rather than anticipated (n 50). SETTING: A multisite SUD treatment centre in Northern California which began implementing nutrition programming changes in order to improve care. PARTICIPANTS: Staff members who consented to participate. RESULTS: From pre to post, we observed significant decreases in perceived barriers related to the provision of nutrition-related treatment (P = 0·019), facility-wide collaboration (P = 0·036), menu changes and client satisfaction (P = 0·024). Implementation of nutrition education and the domain of screening, detecting and monitoring did not reach statistical significance. CONCLUSIONS: Our results show that staff training, food service changes, the use of targeted curriculum for nutrition groups and the encouragement of discussing self-care in individual counselling sessions can lead to positive shifts about nutrition-related organisational change among staff.

Dynamic clonal progression in xenografts of acute lymphoblastic leukemia with intrachromosomal amplification of chromosome 21.

Intrachromosomal amplification of chromosome 21 is a heterogeneous chromosomal rearrangement occurring in 2% of cases of childhood precursor B-cell acute lymphoblastic leukemia. These abnormalities are too complex to engineer faithfully in animal models and are unrepresented in leukemia cell lines. As a resource for future functional and preclinical studies, we have created xenografts from the leukemic blasts of patients with intrachromosomal amplification of chromosome 21 and characterized them by in-vivo and ex-vivo luminescent imaging, flow immunophenotyping, and histological and ultrastructural analyses of bone marrow and the central nervous system. Investigation of up to three generations of xenografts revealed phenotypic evolution, branching genomic architecture and, compared with other B-cell acute lymphoblastic leukemia genetic subtypes, greater clonal diversity of leukemia-initiating cells. In support of intrachromosomal amplification of chromosome 21 as a primary genetic abnormality, it was always retained through generations of xenografts, although we also observed the first example of structural evolution of this rearrangement. Clonal segregation in xenografts revealed convergent evolution of different secondary genomic abnormalities implicating several known tumor suppressor genes and a region, containing the B-cell adaptor, PIK3AP1, and nuclear receptor co-repressor, LCOR, in the progression of B-cell acute lymphoblastic leukemia. Tracking of mutations in patients and derived xenografts provided evidence for co-operation between abnormalities activating the RAS pathway in B-cell acute lymphoblastic leukemia and for their aggressive clonal expansion in the xeno-environment. Bi-allelic loss of the CDKN2A/B locus was recurrently maintained or emergent in xenografts and also strongly selected as RNA sequencing demonstrated a complete absence of reads for genes associated with the deletions.

Risk factors associated with hypertensive disorders of pregnancy within an urban indigenous population in south western Sydney.

BACKGROUND: The prevalence of hypertensive disorders of pregnancy (HDP) in Australia's urban indigenous women is unknown. AIM: To explore the risk factors associated with HDP for a cohort of urban indigenous women in South-Western Sydney, Australia. METHODS: This study was conducted in partnership with the Tharawal Aboriginal Medical Service. Women (18-45 years) were recruited at the clinic and community events. The quantitative questionnaire included obstetric history, personal and family history of hypertension. Anthropometric measurements and blood pressure were conducted. Rates were compared with Australian Bureau of Statistics (ABS) national rates. RESULTS: Eighty-three participants completed the questionnaire. The rate of ever having HDP in a pregnancy was 36.1%. The overall ABS rate was 9.8% and for indigenous women, 14%. The mean maternal age at first pregnancy was 20.8 years (SD 3.7 years). The mean body mass index (BMI) of the sample population (n = 81) was 32.2 kg/m2 (SD 9.5 kg/m2 ) and BMI was not related to HDP (P = 0.197). Of those questioned, 25.3% had an individual history and 63.9% had a family history of hypertension. The effect of family history of hypertension (P = 0.020) (odds ratio (OR) 4.29; 95% confidence interval (CI); 1.42-12.93) and individual history of hypertension (P < 0.001) (OR 15.69; 95% CI; 4.50-54.76) were associated with HDP. CONCLUSION: There was a higher rate of HDP in urban indigenous women compared to the national indigenous prevalence. The family history, or individual history of hypertension was the most significant risk factors and BMI was not identified as a risk factor for HDP in this population.

Inspections of X-ray Use in Dental Practices and Common Regulatory Violations.

Dental X-ray machine inspections are conducted by the California Department of Public Health's Radiologic Health Branch (RHB). RHB's mission is to protect public health and safety throughout California by ensuring the safe use of radiologic equipment and materials within industry, medicine and research, preventing radiologic health hazards and educating and enforcing applicable state and federal radiation laws and regulations.

Characterisation of the genomic landscape of CRLF2-rearranged acute lymphoblastic leukemia.

Deregulated expression of the type I cytokine receptor, CRLF2, is observed in 5-15% of precursor B-cell acute lymphoblastic leukaemia (B-ALL). We aimed to determine the clinical and genetic landscape of those with IGH-CRLF2 or P2RY8-CRLF2 (CRLF2-r) using multiple genomic approaches. Clinical and demographic features of CRLF2-r patients were characteristic of B-ALL. Patients with IGH-CRLF2 were older (14 y vs. 4 y, P < .001), while the incidence of CRLF2-r among Down syndrome patients was high (50/161, 31%). CRLF2-r co-occurred with primary chromosomal rearrangements but the majority (111/161, 69%) had B-other ALL. Copy number alteration (CNA) profiles were similar to B-other ALL, although CRLF2-r patients harbored higher frequencies of IKZF1 (60/138, 43% vs. 77/1351, 24%) and BTG1 deletions (20/138, 15% vs. 3/1351, 1%). There were significant differences in CNA profiles between IGH-CRLF2 and P2RY8-CRLF2 patients: IKZF1 (25/35, 71% vs. 36/108, 33%, P < .001), BTG1 (11/35, 31% vs. 10/108, 9%, P =.004), and ADD3 deletions (9/19, 47% vs. 5/38, 13%, P =.008). A novel gene fusion, USP9X-DDX3X, was discovered in 10/54 (19%) of patients. Pathway analysis of the mutational profile revealed novel involvement for focal adhesion. Although the functional relevance of many of these abnormalities are unknown, they likely activate additional pathways, which may represent novel therapeutic targets.

Developing a new Get Healthy Service program on reducing risky alcohol consumption.

Risky alcohol use has significant individual health and social impacts, and is related to short- and long-term harm, including injuries, accidents, liver diseases, some cancers, cardiovascular diseases and alcohol dependence. The Get Healthy Information & Coaching Service (GHS) is a free telephone coaching service supporting adults 16 years or older to reduce weight, improve nutrition and increase physical activity. Tailored programs are available for Aboriginal people, pregnant women and people at risk of type 2 diabetes. The GHS provides an opportunity to implement a specific program for participants wishing to reduce or cease their alcohol consumption. This paper describes the processes used to develop an Alcohol Program for the GHS. It outlines the contributions from clinical and program experts, the evidence base for the program's development, clinical screening tools, training for health coaches and referral processes for participants. The Alcohol Program has the potential to provide effective coaching to adults to voluntarily reduce short- and long-term risky alcohol consumption.

The ability to cross the blood-cerebrospinal fluid barrier is a generic property of acute lymphoblastic leukemia blasts.

Prevention of central nervous system (CNS) relapse is critical for cure of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Despite this, mechanisms of CNS infiltration are poorly understood, and the timing, frequency, and properties of BCP-ALL blasts entering the CNS compartment are unknown. We investigated the CNS-engrafting potential of BCP-ALL cells xenotransplanted into immunodeficient NOD.Cg- ITALIC! Prkdc (ITALIC! scid) ITALIC! Il2rg (ITALIC! tm1Wjl)/SzJ mice. CNS engraftment was seen in 23 of 29 diagnostic samples (79%): 2 of 2 from patients with overt CNS disease and 21 of 27 from patients thought to be CNS negative by diagnostic lumbar puncture. Histologic findings mimic human pathology and demonstrate that leukemic cells transit the blood-cerebrospinal fluid barrier situated close to the dural sinuses, the site of recently discovered CNS lymphatics. Retrieval of blasts from the CNS showed no evidence for chemokine receptor-mediated selective trafficking. The high frequency of infiltration and lack of selective trafficking led us to postulate that CNS tropism is a generic property of leukemic cells. To test this, we performed serial dilution experiments which showed CNS engraftment in 5 of 6 mice after transplant of as few as 10 leukemic cells. Clonal tracking techniques confirmed the polyclonal nature of CNS-infiltrating cells, with multiple clones engrafting in both the CNS and periphery. Overall, these findings suggest that subclinical seeding of the CNS is likely to be present in most BCP-ALL patients at original diagnosis, and efforts to prevent CNS relapse should concentrate on effective eradication of disease from this site rather than targeting entry mechanisms.

Requirement for Transcription Factor Ets1 in B Cell Tolerance to Self-Antigens.

The differentiation and survival of autoreactive B cells is normally limited by a variety of self-tolerance mechanisms, including clonal deletion, anergy, and clonal ignorance. The transcription factor c-ets-1 (encoded by the Ets1 gene) has B cell-intrinsic roles in regulating formation of Ab-secreting cells by controlling the activity of Blimp1 and Pax5 and may be required for B cell tolerance to self-antigen. To test this, we crossed Ets1(-/-) mice to two different transgenic models of B cell self-reactivity, the anti-hen egg lysozyme BCR transgenic strain and the AM14 rheumatoid factor transgenic strain. BCR transgenic Ets1(-/-) mice were subsequently crossed to mice either carrying or lacking relevant autoantigens. We found that B cells lacking c-ets-1 are generally hyperresponsive in terms of Ab secretion and form large numbers of Ab-secreting cells even in the absence of cognate Ags. When in the presence of cognate Ag, different responses were noted depending on the physical characteristics of the Ag. We found that clonal deletion of highly autoreactive B cells in the bone marrow was intact in the absence of c-ets-1. However, peripheral B cells lacking c-ets-1 failed to become tolerant in response to stimuli that normally induce B cell anergy or B cell clonal ignorance. Interestingly, high-affinity soluble self-antigen did cause B cells to adopt many of the classical features of anergic B cells, although such cells still secreted Ab. Therefore, maintenance of appropriate c-ets-1 levels is essential to prevent loss of self-tolerance in the B cell compartment.