Genetic loss of SH2B3 in acute lymphoblastic leukemia. Blood. 2013;122:2425-2432. [PMID: 23908464 DOI: 10.1182/blood-2013-05-500850]

LNK/SH2B3 as a novel driver in juvenile myelomonocytic leukemia

Mutations in five canonical Ras pathway genes (NF1, NRAS, KRAS, PTPN11 and CBL) are detected in nearly 90% of patients with juvenile myelomonocytic leukemia (JMML), a frequently fatal malignant neoplasm of early childhood. In this report, we describe seven patients diagnosed with SH2B3-mutated JMML, including five patients who were found to have initiating, loss-of-function mutations in the gene. SH2B3 encodes the adaptor protein LNK, a negative regulator of normal hematopoiesis upstream of the Ras pathway. These mutations were identified to be germline, somatic or a combination of both. Loss of function of LNK, which has been observed in other myeloid malignancies, results in abnormal proliferation of hematopoietic cells due to cytokine hypersensitivity and activation of the JAK/STAT signaling pathway. In vitro studies of induced pluripotent stem cell-derived JMML-like hematopoietic progenitor cells also demonstrated sensitivity of SH2B3-mutated hematopoietic progenitor cells to JAK inhibition. Lastly, we describe two patients with JMML and SH2B3 mutations who were treated with the JAK1/2 inhibitor ruxolitinib. This report expands the spectrum of initiating mutations in JMML and raises the possibility of targeting the JAK/STAT pathway in patients with SH2B3 mutations.

SH2B3 alterations in a novel genetic condition, juvenile myelomonocytic leukemia, and myeloproliferative neoplasia

Not available.

Germline bi-allelic SH2B3/LNK alteration predisposes to a neonatal juvenile myelomonocytic leukemia-like disorder

Juvenile myelomonocytic leukemia (JMML) is a rare, generally aggressive myeloproliferative neoplasm affecting young children. It is characterized by granulomonocytic expansion, with monocytosis infiltrating peripheral tissues. JMML is initiated by mutations upregulating RAS signaling. Approximately 10% of cases remain without an identified driver event. Exome sequencing of two unrelated cases of familial JMML of unknown genetics and analysis of the French JMML cohort identified 11 patients with variants in SH2B3, encoding LNK, a negative regulator of the JAK-STAT pathway. All variants were absent from healthy population databases, and the mutation spectrum was consistent with a loss of function of the LNK protein. A stoploss variant was shown to affect both protein synthesis and stability. The other variants were either truncating or missense, the latter affecting the SH2 domain that interacts with activated JAK. Of the 11 patients, eight from five families inherited pathogenic bi-allelic SH2B3 germline variants from their unaffected heterozygous parents. These children represent half of the cases with no identified causal mutation in the French cohort. They displayed typical clinical and hematologic features of JMML with neonatal onset and marked thrombocytopenia. They had a hypomethylated DNA profile with fetal characteristics and did not have additional genetic alterations. All patients showed partial or complete spontaneous clinical resolution. However, progression to thrombocythemia and immunity-related pathologies may be of concern later in life. Bi-allelic SH2B3 germline mutations thus define a new condition predisposing to a JMML-like disorder, suggesting that JAK pathway deregulation is capable of initiating JMML, and opening new therapeutic options.

Rare SH2B3 coding variants in lupus patients impair B cell tolerance and predispose to autoimmunity

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with a clear genetic component. While most SLE patients carry rare gene variants in lupus risk genes, little is known about their contribution to disease pathogenesis. Amongst them, SH2B3-a negative regulator of cytokine and growth factor receptor signaling-harbors rare coding variants in over 5% of SLE patients. Here, we show that unlike the variant found exclusively in healthy controls, SH2B3 rare variants found in lupus patients are predominantly hypomorphic alleles, failing to suppress IFNGR signaling via JAK2-STAT1. The generation of two mouse lines carrying patients' variants revealed that SH2B3 is important in limiting the number of immature and transitional B cells. Furthermore, hypomorphic SH2B3 was shown to impair the negative selection of immature/transitional self-reactive B cells and accelerate autoimmunity in sensitized mice, at least in part due to increased IL-4R signaling and BAFF-R expression. This work identifies a previously unappreciated role for SH2B3 in human B cell tolerance and lupus risk.

Candidate Genetic and Molecular Drivers of Dysregulated Adaptive Immune Responses After Traumatic Brain Injury

Abstract Neuroinflammation is a significant and modifiable cause of secondary injury after traumatic brain injury (TBI), driven by both central and peripheral immune responses. A substantial proportion of outcome after TBI is genetically mediated, with an estimated heritability effect of around 26%, but because of the comparatively small datasets currently available, the individual drivers of this genetic effect have not been well delineated. A hypothesis-driven approach to analyzing genome-wide association study (GWAS) datasets reduces the burden of multiplicity testing and allows variants with a high prior biological probability of effect to be identified where sample size is insufficient to withstand data-driven approaches. Adaptive immune responses show substantial genetically mediated heterogeneity and are well established as a genetic source of risk for numerous disease states; importantly, HLA class II has been specifically identified as a locus of interest in the largest TBI GWAS study to date, highlighting the importance of genetic variance in adaptive immune responses after TBI. In this review article we identify and discuss adaptive immune system genes that are known to confer strong risk effects for human disease, with the dual intentions of drawing attention to this area of immunobiology, which, despite its importance to the field, remains under-investigated in TBI and presenting high-yield testable hypotheses for application to TBI GWAS datasets.

Biallelic deleterious germline SH2B3 variants cause a novel syndrome of myeloproliferation and multi-organ autoimmunity

SH2B3 is a negative regulator of multiple cytokine receptor signalling pathways in haematopoietic tissue. To date, a single kindred has been described with germline biallelic loss-of-function SH2B3 variants characterized by early onset developmental delay, hepatosplenomegaly and autoimmune thyroiditis/hepatitis. Herein, we described two further unrelated kindreds with germline biallelic loss-of-function SH2B3 variants that show striking phenotypic similarity to each other as well as to the previous kindred of myeloproliferation and multi-organ autoimmunity. One proband also suffered severe thrombotic complications. CRISPR-Cas9 gene editing of zebrafish sh2b3 created assorted deleterious variants in F0 crispants, which manifest significantly increased number of macrophages and thrombocytes, partially replicating the human phenotype. Treatment of the sh2b3 crispant fish with ruxolitinib intercepted this myeloproliferative phenotype. Skin-derived fibroblasts from one patient demonstrated increased phosphorylation of JAK2 and STAT5 after stimulation with IL-3, GH, GM-CSF and EPO compared to healthy controls. In conclusion, these additional probands and functional data in combination with the previous kindred provide sufficient evidence for biallelic homozygous deleterious variants in SH2B3 to be considered a valid gene-disease association for a clinical syndrome of bone marrow myeloproliferation and multi-organ autoimmune manifestations.

Immune dysregulation associated with co-occurring germline CBL and SH2B3 variants

Background

CBL syndrome is a RASopathy caused by heterozygous germline mutations of the Casitas B-lineage lymphoma (CBL) gene. It is characterized by heterogeneous clinical phenotype, including developmental delay, facial dysmorphisms, cardiovascular malformations and an increased risk of cancer development, particularly juvenile myelomonocytic leukemia (JMML). Although the clinical phenotype has been progressively defined in recent years, immunological manifestations have not been well elucidated to date.

Methods

We studied the genetic, immunological, coagulative, and clinical profile of a family with CBL syndrome that came to our observation after the diagnosis of JMML, with homozygous CBL mutation, in one of the members.

Results

Variant analysis revealed the co-occurrence of CBL heterozygous mutation (c.1141 T > C) and SH2B3 mutation (c.1697G > A) in two other members. Patients carrying both mutations showed an ALPS-like phenotype characterized by lymphoproliferation, cytopenia, increased double-negative T-cells, impaired Fas-mediated lymphocyte apoptosis, altered cell death in PBMC and low TRECs expression. A coagulative work-up was also performed and showed the presence of subclinical coagulative alterations in patients carrying both mutations.

Conclusion

In the reported family, we described immune dysregulation, as part of the clinical spectrum of CBL mutation with the co-occurrence of SH2B3.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-022-00414-y.

Inherited Susceptibility to Hematopoietic Malignancies in the Era of Precision Oncology

As germline predisposition to hematopoietic malignancies has gained increased recognition and attention in the field of oncology, it is important for clinicians to use a systematic framework for the identification, management, and surveillance of patients with hereditary hematopoietic malignancies (HHMs). In this article, we discuss strategies for identifying individuals who warrant diagnostic evaluation and describe considerations pertaining to molecular testing. Although a paucity of prospective data is available to guide clinical monitoring of individuals harboring pathogenic variants, we provide recommendations for clinical surveillance based on consensus opinion and highlight current advances regarding the risk of progression to overt malignancy in HHM variant carriers. We also discuss the prognosis of HHMs and considerations surrounding the utility of allogeneic stem-cell transplantation in these individuals. We close with an overview of contemporary issues at the intersection of HHMs and precision oncology.

The Role of LNK (SH2B3) in the Regulation of JAK-STAT Signalling in Haematopoiesis

LNK is a member of the SH2B family of adaptor proteins and is a non-redundant regulator of cytokine signalling. Cytokines are secreted intercellular messengers that bind to specific receptors on the surface of target cells to activate the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) signalling pathway. Activation of the JAK-STAT pathway leads to proliferative and often inflammatory effects, and so the amplitude and duration of signalling are tightly controlled. LNK binds phosphotyrosine residues to signalling proteins downstream of cytokines and constrains JAK-STAT signalling. Mutations in LNK have been identified in a range of haematological and inflammatory diseases due to increased signalling following the loss of LNK function. Here, we review the regulation of JAK-STAT signalling via the adaptor protein LNK and discuss the role of LNK in haematological diseases.

Somatic homozygous loss of SH2B3, and a non-Robertsonian translocation t(15;21)(q25.3;q22.1) with NTRK3 rearrangement, in an adolescent with progenitor B-cell acute lymphoblastic leukemia with the iAMP21

Intrachromosomal amplification of chromosome 21 (iAMP21) occurs in ∼2% of B-cell acute lymphoblastic leukemia (ALL) and is considered to confer a poor prognosis. The relapse risk is associated with therapy intensity, suggesting that other somatic mutations may influence iAMP21-ALL prognosis. This abnormality is characterized by multiple copies of the RUNX1 gene in chromosome 21 and appears to arise through multiple breakage-fusion bridge cycles and chromothripsis. Rob(15;21) or a ring chromosome 21 have been associated with an increased risk for iAMP21-ALL, suggesting that constitutional genetic abnormalities may also drive leukemogenesis. Here we describe homozygous deletion of the SH2B3 gene, chromothripsis of chromosome 21, and a non-Robertsonian somatic t(15;21)(q25.3;q22.1) with NTRK3 gene rearrangement in an adolescent with iAMP21-B-ALL. Molecular cytogenetic studies detected iAMP21 with aCGH analysis revealing further genomic imbalances. The RT-qPCR analysis detected elevated expression levels of RUNX1 (68-fold) and reduced expression of CDK6 (0.057-fold). Studies with constitutive cells collected from mouth swabs showed that SH2B3 biallelic deletion was a somatic alteration occurring during clonal evolution. The identification of novel secondary genetic changes was valuable to discuss sporadic iAMP21 leukemogenic mechanisms. For the first time, we show a t(15;21)(q25.3;q22.1) with NTRK3 rearrangement in an adolescent with iAMP21-ALL.

Toward prevention of childhood ALL by early-life immune training

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common form of childhood cancer. Chemotherapy is associated with life-long health sequelae and fails in ∼20% of cases. Thus, prevention of leukemia would be preferable to treatment. Childhood leukemia frequently starts before birth, during fetal hematopoiesis. A first genetic hit (eg, the ETV6-RUNX1 gene fusion) leads to the expansion of preleukemic B-cell clones, which are detectable in healthy newborn cord blood (up to 5%). These preleukemic clones give rise to clinically overt leukemia in only ∼0.2% of carriers. Experimental evidence suggests that a major driver of conversion from the preleukemic to the leukemic state is exposure to immune challenges. Novel insights have shed light on immune host responses and how they shape the complex interplay between (1) inherited or acquired genetic predispositions, (2) exposure to infection, and (3) abnormal cytokine release from immunologically untrained cells. Here, we integrate the recently emerging concept of "trained immunity" into existing models of childhood BCP-ALL and suggest future avenues toward leukemia prevention.

Structural and functional analysis of target recognition by the lymphocyte adaptor protein LNK

The SH2B family of adaptor proteins, SH2-B, APS, and LNK are key modulators of cellular signalling pathways. Whilst SH2-B and APS have been partially structurally and biochemically characterised, to date there has been no such characterisation of LNK. Here we present two crystal structures of the LNK substrate recognition domain, the SH2 domain, bound to phosphorylated motifs from JAK2 and EPOR, and biochemically define the basis for target recognition. The LNK SH2 domain adopts a canonical SH2 domain fold with an additional N-terminal helix. Targeted analysis of binding to phosphosites in signalling pathways indicated that specificity is conferred by amino acids one- and three-residues downstream of the phosphotyrosine. Several mutations in LNK showed impaired target binding in vitro and a reduced ability to inhibit signalling, allowing an understanding of the molecular basis of LNK dysfunction in variants identified in patients with myeloproliferative disease.

Infectious triggers and novel therapeutic opportunities in childhood B cell leukaemia

B cell acute lymphoblastic leukaemia (B-ALL) is the most common form of childhood cancer. Although treatment has advanced remarkably in the past 50 years, it still fails in ~20% of patients. Recent studies revealed that more than 5% of healthy newborns carry preleukaemic clones that originate in utero, but only a small percentage of these carriers will progress to overt B-ALL. The drivers of progression are unclear, but B-ALL incidence seems to be increasing in parallel with the adoption of modern lifestyles. Emerging evidence shows that a major driver for the conversion from the preleukaemic state to the B-ALL state is exposure to immune stressors, such as infection. Here, we discuss our current understanding of the environmental triggers and genetic predispositions that may lead to B-ALL, highlighting lessons from epidemiology, the clinic and animal models, and identifying priority areas for future research.

An isolated childhood myeloid sarcoma with germline MSH6 mutation-a case report

Myeloid sarcoma (MS) is a type of malignant tumor that originates in the bone marrow. This study reports on the treatment of an 11-year-old Uygur girl with a 15-day history of fever and paroxysmal cough, accompanied by right hip pain. During treatment, fatigue and anemia developed, physical strength decreased, and a few petechiae were seen in the lower extremities. Multiple enlarged lymph nodes were palpable in the neck, with slight congestion in the pharynx. Routine blood screening showed three major myeloid lineage abnormalities. Pathological examination revealed the presence of CD10 (-), CD99 (+), CD20 (+), CD3 (-), CD117 (weak+), CD34 (unclear location), TdT (-), Pax5 (-), Ki-67 (50%+), MPO (-), and CD43 (+). The patient was eventually diagnosed with isolated MS. After chemotherapy, no small particles were observed in bone marrow morphology. Complete remission was confirmed by flow cytometric detection of minimal residual disease. Genomic DNA was subjected to targeted sequencing of 236 gene panels to detect somatic mutations and the MSH6 c.3953_3954insAA p.R1318fs germline mutation. Unfortunately, the patient was subsequently lost to follow-up. To our knowledge, an MSH6 germline mutation had not previously been reported in children with MS, and we speculated that an MSH6 germline mutation led to genomic instability, triggering a somatic mutation in multiple genes and ultimately led to the development of MS in this patient. It is suggested that rare base abnormalities may be involved in the development of isolated myeloid sarcomas (IMS).

A New Treatment Strategy for Early T-Cell Precursor Acute Lymphoblastic Leukemia: A Case Report and Literature Review

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is an aggressive and extremely fatal subtype of T-cell acute lymphoblastic leukemia (T-ALL), characterized by the similar transcriptional and immunophenotypic profiles to those of early T-cell precursors and positive expressions of myeloid antigens. Besides, the gene expression profile in ETP-ALL is similar to that in myeloid malignancies. The clinical characteristics, treatments and prognoses of ETP-ALL are significantly heterogeneous. In the present study, we reported a 43-year-old female patient who lacked terminal deoxynucleotidyl transferase (TDT) expression in immunophenotype and displayed mutations of fms-like tyrosine kinase-internal tandem duplication (FLT3-ITD), paired-box domain 5 (PAX5) and SH2B adaptor protein 3 (SH2B3) (PAX5 and SH2B3, the genes critical to B cell identity and function), which represent myeloid and precursor B-lineage associated gene mutations, respectively. It was a rare T-ALL or T-lineage case. Because of multiple poor prognostic factors in this case, conventional induction regimens, like hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, dexamethasone), were invalid. The patient showed inadequate response, suggesting that this treatment was not employed on the basis of the immunophenotype. FLAG-IDA regimen (fludarabine, cytarabine [Ara-C], granulocyte-colony stimulating factor [G-CSF] and idarubicin), which is usually applied to eliminate leukemia cells, was administered combining with sorafenib as an effective induction chemotherapy. The case achieved long-term survival following the allogeneic hematopoietic stem cell transplantation (allo-HSCT). We recommend that adult ETP-ALL patients can be treated with a myeloid-oriented chemotherapy (as frontline induction treatment) along with gene-targeting inhibitors, followed by allo-HSCT.

SH2B3, Transcribed by STAT1, Promotes Glioblastoma Progression Through Transducing IL-6/gp130 Signaling to Activate STAT3 Signaling

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. The aberrant activation of STAT3 commonly occurs in GBM and is a key player in GBM tumorigenesis. Yet, the aberrant activation of STAT3 signaling is not fully understood. Here, we report that SH2B adaptor protein 3 (SH2B3) is highly expressed in GBM and preferentially expressed in GBM stem cells (GSCs). Moreover, SH2B3 high expression predicts worse survival of GBM patients. Targeting SH2B3 considerably impairs GBM cell proliferation, migration, and GSCs' self-renewal in vitro as well as xenograft tumors growth in vivo. Additionally, we provide evidence suggesting that STAT1 directly binds to the promoter of SH2B3 and activates SH2B3 expression in the transcriptional level. Functionally, SH2B3 facilitates GBM progression via physically interacting with gp130 and acting as an adaptor protein to transduce IL-6/gp130/STAT3 signaling. Together, our work firstly uncovers that the STAT1/SH2B3/gp130/STAT3 signaling axis plays critical roles in promoting GBM progression and provides insight into new prognosis marker and therapeutic target in GBM.

Advances in germline predisposition to acute leukaemias and myeloid neoplasms

Although much work has focused on the elucidation of somatic alterations that drive the development of acute leukaemias and other haematopoietic diseases, it has become increasingly recognized that germline mutations are common in many of these neoplasms. In this Review, we highlight the different genetic pathways impacted by germline mutations that can ultimately lead to the development of familial and sporadic haematological malignancies, including acute lymphoblastic leukaemia, acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Many of the genes disrupted by somatic mutations in these diseases (for example, TP53, RUNX1, IKZF1 and ETV6) are the same as those that harbour germline mutations in children and adolescents who develop these malignancies. Moreover, the presumption that familial leukaemias only present in childhood is no longer true, in large part due to the numerous studies demonstrating germline DDX41 mutations in adults with MDS and AML. Lastly, we highlight how different cooperating events can influence the ultimate phenotype in these different familial leukaemia syndromes.

Novel germline TRAF3IP3 mutation in a dyad with familial acute B lymphoblastic leukemia

Background

Acute lymphoblastic leukemia (ALL) is the most common hematologic malignancy in children, representing 25% of all new cancer diagnoses. Advances in genomic sequencing have demonstrated that inherited genetic risk factors play a larger role in leukemia development than previously appreciated.

Aim

We identified a father–daughter dyad with childhood B‐cell ALL and aimed to investigate whether the pair shared a gene associated with leukemia predisposition.

Methods

We performed whole exome sequencing on their leukemia and germline samples and RNA‐seq on their leukemia samples.

Results

We discovered a novel germline chromosomal structural variant in chromosome 1q32.2 within the TRAF3IP3 gene. TRAF3IP3 regulates B‐cell lymphopoiesis, and this mutation likely resulted in a predisposition to leukemia by causing expansion of immature B‐cell precursors which are highly vulnerable to secondary somatic mutations. Based on the lack of concordance in the somatic mutational profiles between this dyad's leukemia samples, we suspect that the acquired somatic mutations rather than this germline mutation are what dictated their leukemia phenotypes, which we confirmed through RNA‐seq by comparing to sporadic cases of B‐cell ALL.

Conclusion

This research may have identified a novel gene involved in leukemogenesis which may also be involved in de novo cases of ALL. Additional studies are needed to further characterize this TRAF3IP3 structural variant, the co‐occurring somatic mutations within these leukemia samples and their combined role in leukemogenesis.

CTLA-4 blockade and interferon-α induce proinflammatory transcriptional changes in the tumor immune landscape that correlate with pathologic response in melanoma

Patients with locally/regionally advanced melanoma were treated with neoadjuvant combination immunotherapy with high-dose interferon α-2b (HDI) and ipilimumab in a phase I clinical trial. Tumor specimens were obtained prior to the initiation of neoadjuvant therapy, at the time of surgery and progression if available. In this study, gene expression profiles of tumor specimens (N = 27) were investigated using the NanoString nCounter® platform to evaluate associations with clinical outcomes (pathologic response, radiologic response, relapse-free survival (RFS), and overall survival (OS)) and define biomarkers associated with tumor response. The Tumor Inflammation Signature (TIS), an 18-gene signature that enriches for response to Programmed cell death protein 1 (PD-1) checkpoint blockade, was also evaluated for association with clinical response and survival. It was observed that neoadjuvant ipilimumab-HDI therapy demonstrated an upregulation of immune-related genes, chemokines, and transcription regulator genes involved in immune cell activation, function, or cell proliferation. Importantly, increased expression of baseline pro-inflammatory genes CCL19, CD3D, CD8A, CD22, LY9, IL12RB1, C1S, C7, AMICA1, TIAM1, TIGIT, THY1 was associated with longer OS (p < 0.05). In addition, multiple genes that encode a component or a regulator of the extracellular matrix such as MMP2 and COL1A2 were identified post-treatment as being associated with longer RFS and OS. In all baseline tissues, high TIS scores were associated with longer OS (p = 0.0166). Also, downregulated expression of cell proliferation-related genes such as CUL1, CCND1 and AAMP at baseline was associated with pathological and radiological response (unadjusted p < 0.01). In conclusion, we identified numerous genes that play roles in multiple biological pathways involved in immune activation, immune suppression and cell proliferation correlating with pathological/radiological responses following neoadjuvant immunotherapy highlighting the complexity of immune responses modulated by immunotherapy. Our observations suggest that TIS may be a useful biomarker for predicting survival outcomes with combination immunotherapy.

Inherited predisposition to haematopoietic malignancies: overcoming barriers and exploring opportunities

Inherited predisposition to haematopoietic malignancies, due to deleterious germline variants in a variety of genes, is an important clinical entity with implications for the health and management of patients and their family members. Unfortunately, there remain several common misconceptions in this field that can result in patients going unrecognised and/or having incomplete or improper testing including: the impression that inherited haematological malignancy syndromes are rare, that myeloid and lymphoid malignancy predisposition syndromes are mutually exclusive, and that solid tumour predisposition syndromes are unique and distinct from haematopoietic malignancy predisposition syndromes. In the present review, we challenge these ideas with our insights into germline genetic testing for these conditions with the hope that increased awareness and knowledge will overcome barriers and lead to improved diagnosis and management.

Whole genome sequencing analysis of high confidence variants of B-cell lymphoma in Canis familiaris

Lymphoma (lymphosarcoma) is the second most frequent cancer in dogs and is clinically comparable to human non-Hodgkin lymphoma. Factors affecting canine lymphoma progression are unknown and complex, but there is evidence that genetic mutations play an important role. We employed Next Gen DNA sequencing of six dogs with multicentric B-cell lymphoma undergoing CHOP chemotherapy to identify genetic variations potentially impacting response. Paired samples from non-neoplastic tissue (blood mononuclear cells) and lymphoma were collected at the time of diagnosis. Cases with progression free survival above the median of 231 days were grouped as 'good' responders and cases below the median were categorized as 'poor' responders. The average number of variants found was 17,138 per case. The variants were filtered to examine those with predicted moderate or high impacts. Many of the genes with variants had human orthologs with links to cancer, but the majority of variants were not previously reported in canine or human lymphoma. Seven genes had variants found in the cancers of at least two 'poor' responders but in no 'good' responders: ATRNL1, BAIAP2L2, ZNF384, ST6GALNAC5, ENSCAFG00000030179 (human ortholog: riboflavin kinase RFK), ENSCAFG00000029320, and ENSCAFG00000007370 (human ortholog: immunoglobin IGKV4-1). Two genes had variants found in the cancers of at least two 'good' responders but in no 'poor' responders: COX18 and ENSCAFG00000030512. ENSCAFG00000030512 has no reported orthologue in any other species. The role of these mutations in the progression of canine lymphoma requires further functional analyses and larger scale study.

New Insights into the Genetics of Latent Autoimmune Diabetes in Adults

PURPOSE OF REVIEW

Diabetes is a spectrum of clinical manifestations, including latent autoimmune diabetes in adults (LADA). However, it has been questioned whether LADA exists or simply is a group of misclassified type 1 diabetes (T1D) and type 2 diabetes (T2D) patients. This review will provide an updated overview of the genetics of LADA, highlight what genetics tell us about LADA as a diabetes subtype, and point to future directions in the study of LADA.

RECENT FINDINGS

Recent studies have verified the genetic overlap between LADA and both T1D and T2D and have contributed identification of a novel LADA-specific locus, namely, PFKFB3, and subtype-specific signatures in the HLA region. Genetic risk scores comprising T1D-risk variants have been shown to be a promising tool for discriminating diabetes subtypes and identifying patients rapidly progressing to insulin dependence. Genetic data support the existence of LADA, but further studies are needed to fully determine the place of LADA in the diabetes spectrum.

Restriction of memory B cell differentiation at the germinal center B cell positive selection stage

Memory B cells (MBCs) are key for protection from reinfection. However, it is mechanistically unclear how germinal center (GC) B cells differentiate into MBCs. MYC is transiently induced in cells fated for GC expansion and plasma cell (PC) formation, so-called positively selected GC B cells. We found that these cells coexpressed MYC and MIZ1 (MYC-interacting zinc-finger protein 1 [ZBTB17]). MYC and MIZ1 are transcriptional activators; however, they form a transcriptional repressor complex that represses MIZ1 target genes. Mice lacking MYC-MIZ1 complexes displayed impaired cell cycle entry of positively selected GC B cells and reduced GC B cell expansion and PC formation. Notably, absence of MYC-MIZ1 complexes in positively selected GC B cells led to a gene expression profile alike that of MBCs and increased MBC differentiation. Thus, at the GC positive selection stage, MYC-MIZ1 complexes are required for effective GC expansion and PC formation and to restrict MBC differentiation. We propose that MYC and MIZ1 form a module that regulates GC B cell fate.

Hereditary Predisposition to Hematopoietic Neoplasms: When Bloodline Matters for Blood Cancers

With the advent of precision genomics, hereditary predisposition to hematopoietic neoplasms- collectively known as hereditary predisposition syndromes (HPS)-are being increasingly recognized in clinical practice. Familial clustering was first observed in patients with leukemia, which led to the identification of several germline variants, such as RUNX1, CEBPA, GATA2, ANKRD26, DDX41, and ETV6, among others, now established as HPS, with tendency to develop myeloid neoplasms. However, evidence for hereditary predisposition is also apparent in lymphoid and plasma--cell neoplasms, with recent discoveries of germline variants in genes such as IKZF1, SH2B3, PAX5 (familial acute lymphoblastic leukemia), and KDM1A/LSD1 (familial multiple myeloma). Specific inherited bone marrow failure syndromes-such as GATA2 haploinsufficiency syndromes, short telomere syndromes, Shwachman-Diamond syndrome, Diamond-Blackfan anemia, severe congenital neutropenia, and familial thrombocytopenias-also have an increased predisposition to develop myeloid neoplasms, whereas inherited immune deficiency syndromes, such as ataxia-telangiectasia, Bloom syndrome, Wiskott Aldrich syndrome, and Bruton agammaglobulinemia, are associated with an increased risk for lymphoid neoplasms. Timely recognition of HPS is critical to ensure safe choice of donors and/or conditioning-regimen intensity for allogeneic hematopoietic stem-cell transplantation and to enable direction of appropriate genomics-driven personalized therapies. The purpose of this review is to provide a comprehensive overview of HPS and serve as a useful reference for clinicians to recognize relevant signs and symptoms among patients to enable timely screening and referrals to pursue germline assessment. In addition, we also discuss our institutional approach toward identification of HPS and offer a stepwise diagnostic and management algorithm.

Modeling NOTCH1 driven T-cell Acute Lymphoblastic Leukemia in Mice

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that arises from transformation of T-cell primed hematopoietic progenitors. Although T-ALL is a heterogenous and molecularly complex disease, more than 65% of T-ALL patients carry activating mutations in the NOTCH1 gene. The majority of T-ALL-associated NOTCH1 mutations either disrupt the negative regulatory region, allowing signal activation in the absence of ligand binding, or result in truncation of the C-terminal PEST domain involved in the termination of NOTCH1 signaling by proteasomal degradation. To date, retroviral transduction models have relied heavily on the overexpression of aggressively truncated variants of NOTCH1 (such as ICN1 or ΔE-NOTCH1), which result in supraphysiological levels of signaling activity and are rarely found in human T-ALL. The current protocol describes the method for mouse bone marrow isolation, hematopoietic stem and progenitor cell (HSC) enrichment, followed by retroviral transduction with an oncogenic mutant form of the NOTCH1 receptor (NOTCH1-L1601P-ΔP) that closely resembles the gain-of-function mutations most commonly found in patient samples. A hallmark of this forced expression of constitutively active NOTCH1 is a transient wave of extrathymic immature T-cell development, which precedes oncogenic transformation to T-ALL. Furthermore, this approach models leukemic transformation and progression in vivo by allowing for crosstalk between leukemia cells and the microenvironment, an aspect unaccounted for in cell-line based in vitro studies. Thus, the HSC transduction and transplantation model more faithfully recapitulates development of the human disease, providing a highly comprehensive and versatile tool for further in vivo and ex vivo functional studies.

LNK promotes the growth and metastasis of triple negative breast cancer via activating JAK/STAT3 and ERK1/2 pathway

Background

LNK adaptor protein is a crucial regulator of normal hematopoiesis, which down-regulates activated tyrosine kinases at the cell surface resulting in an antitumor effect. To date, little studies have examined activities of LNK in solid tumors except ovarian cancer.

Methods

Clinical tissue chips were obtained from 16 clinical patients after surgery. Western blotting assay and quantitative real time PCR was performed to measure the expression of LNK. We investigate the in vivo and vitro effect of LNK in Triple Negative Breast Cancer by using cell proliferation、migration assays and an in vivo murine xenograft model. Western blotting assay was performed to investigate the mechanism of LNK in triple negative breast cancer.

Results

We found that the levels of LNK expression were elevated in high grade triple-negative breast cancer through Clinical tissue chips. Remarkably, overexpression of LNK can promote breast cancer cell proliferation and migration in vivo and vitro, while silencing of LNK show the opposite phenomenon. We also found that LNK can promote breast cancer cell to proliferate and migrate via activating JAK/STAT3 and ERK1/2 pathway.

Conclusions

Our results suggest that the adaptor protein LNK acts as a positive signal transduction modulator in TNBC.

The Genetics and Mechanisms of T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy derived from early T-cell progenitors. The recognition of clinical, genetic, transcriptional, and biological heterogeneity in this disease has already translated into new prognostic biomarkers, improved leukemia animal models, and emerging targeted therapies. This work reviews our current understanding of the molecular mechanisms of T-ALL.

Transcriptional Regulation of Genes by Ikaros Tumor Suppressor in Acute Lymphoblastic Leukemia

Regulation of oncogenic gene expression by transcription factors that function as tumor suppressors is one of the major mechanisms that regulate leukemogenesis. Understanding this complex process is essential for explaining the pathogenesis of leukemia as well as developing targeted therapies. Here, we provide an overview of the role of Ikaros tumor suppressor and its role in regulation of gene transcription in acute leukemia. Ikaros (IKZF1) is a DNA-binding protein that functions as a master regulator of hematopoiesis and the immune system, as well as a tumor suppressor in acute lymphoblastic leukemia (ALL). Genetic alteration or functional inactivation of Ikaros results in the development of high-risk leukemia. Ikaros binds to the specific consensus binding motif at upstream regulatory elements of its target genes, recruits chromatin-remodeling complexes and activates or represses transcription via chromatin remodeling. Over the last twenty years, a large number of Ikaros target genes have been identified, and the role of Ikaros in the regulation of their expression provided insight into the mechanisms of Ikaros tumor suppressor function in leukemia. Here we summarize the role of Ikaros in the regulation of the expression of the genes whose function is critical for cellular proliferation, development, and progression of acute lymphoblastic leukemia.

Multi-omic approaches to improve outcome for T-cell acute lymphoblastic leukemia patients

In the last decade, tremendous progress in curative treatment has been made for T-ALL patients using high-intensive, risk-adapted multi-agent chemotherapy. Further treatment intensification to improve the cure rate is not feasible as it will increase the number of toxic deaths. Hence, about 20% of pediatric patients relapse and often die due to acquired therapy resistance. Personalized medicine is of utmost importance to further increase cure rates and is achieved by targeting specific initiation, maintenance or resistance mechanisms of the disease. Genomic sequencing has revealed mutations that characterize genetic subtypes of many cancers including T-ALL. However, leukemia may have various activated pathways that are not accompanied by the presence of mutations. Therefore, screening for mutations alone is not sufficient to identify all molecular targets and leukemic dependencies for therapeutic inhibition. We review the extent of the driving type A and the secondary type B genomic mutations in pediatric T-ALL that may be targeted by specific inhibitors. Additionally, we review the need for additional screening methods on the transcriptional and protein levels. An integrated 'multi-omic' screening will identify potential targets and biomarkers to establish significant progress in future individualized treatment of T-ALL patients.

Predisposition to childhood acute lymphoblastic leukemia caused by a constitutional translocation disrupting ETV6

Pathogenic germline variants in ETV6 have been associated with familial predisposition to thrombocytopenia and hematological malignancies, predominantly childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In addition, overrepresentation of a high hyperdiploid subtype and older age at diagnosis have been reported among sporadic BCP-ALL cases with germline variants in ETV6 We studied a family with 2 second-degree relatives who developed childhood high hyperdiploid BCP-ALL at ages 8 and 12 years, respectively. A constitutional balanced reciprocal translocation t(12;14)(p13.2;q23.1) was discovered in both patients by routine karyotyping at diagnosis and, subsequently, in 7 healthy family members who had not experienced hematological malignancies. No carriers had thrombocytopenia. Whole-genome sequencing confirmed the translocation, resulting in 2 actively transcribed but nonfunctional fusion genes, causing heterozygous loss and consequently monoallelic expression of ETV6 Whole-genome sequencing analysis of the affected female subjects' leukemia excluded additional somatic aberrations in ETV6 and RTN1 as well as shared somatic variants in other genes. Expression studies, performed to confirm decreased expression of ETV6, were not conclusive. We suggest that germline aberrations resulting in monoallelic expression of ETV6 contribute to leukemia susceptibility, whereas more severe functional deficiency of ETV6 is required for developing THC5. To our knowledge, this report is the first of a constitutional translocation disrupting ETV6 causing predisposition to childhood ALL.

Germline Predisposition to Hematolymphoid Neoplasia

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology aimed to review clinical cases with germline predisposition to hematolymphoid neoplasms.

METHODS

The Workshop Panel reviewed 51 cases with germline mutations and rendered consensus diagnoses. Of these, six cases were presented at the meeting by the submitting pathologists.

RESULTS

The cases submitted to the session covering germline predisposition included 16 cases with germline GATA2 mutations, 10 cases with germline RUNX1 mutations, two cases with germline CEBPA mutations, two germline TP53 mutations, and one case of germline DDX41 mutation. The most common diagnoses were acute myeloid leukemia (15 cases) and myelodysplastic syndrome (MDS, 14 cases).

CONCLUSIONS

The majority of the submitted neoplasms occurring in patients with germline predisposition were myeloid neoplasms with germline mutations in GATA2 and RUNX1. The presence of a germline predisposition mutation is not sufficient for a diagnosis of a neoplasm until the appearance of standard diagnostic features of a hematolymphoid malignancy manifest: in general, the diagnostic criteria for neoplasms associated with germline predisposition disorders are the same as those for sporadic cases.

Telomere length and its correlation with gene mutations in chronic lymphocytic leukemia in a Korean population

Telomere length (TL) is a prognostic indicator in Caucasian chronic lymphocytic leukemia (CLL), but its significance in Asian CLL remains unknown. To investigate the prognostic significance of TL and its correlation with cytogenetic aberrations and somatic mutations, we analyzed TL measurements at the cellular level by interphase fluorescence in situ hybridization in patients with CLL in Korea. The present study enrolled 110 patients (41 females and 69 males) diagnosed with CLL according to the World Health Organization criteria (2001-2017). TLs of bone marrow nucleated cells at the single-cell level were measured by quantitative fluorescence in situ hybridization (Q-FISH) in 71 patients. The correlations of TL with clinical characteristics, cytogenetic aberrations, genetic mutations, and overall survival were assessed. The median value of mean TL in CLL patients (T/C ratio 7.46 (range 1.19-18.14) was significantly shorter than that in the normal controls (T/C ratio 15.28 (range 8.59-24.93) (p < 0.001). Shorter TLs were associated with complex karyotypes (p = 0.030), del(11q22) (p = 0.023), presence of deletion and/or mutation in ATM and/or TP53 (p = 0.019), and SH2B3 mutation (p = 0.015). A shorter TL was correlated with lower hemoglobin levels and adverse survival (mean TL < 9.35, p = 0.021). When the proportion of cells with extremely short TLs (< 7.61) was greater than 90%, CLL patients showed poor survival (p = 0.002). Complex karyotypes, TP53 mutation, and the number of mutated genes were determined to be significant adverse variables by multivariable Cox analysis (p = 0.011, p = 0.002, and p = 0.002, respectively). TL was attrited in CLL, and attrited telomeres were correlated with adverse survival and other well-known adverse prognostic factors. We infer that TL is an independent adverse prognostic predictor in Korean CLL.

Genetic defects in hematopoietic transcription factors and predisposition to acute lymphoblastic leukemia

Recent genome-wide studies have revealed a plethora of germline variants that significantly influence the susceptibility to acute lymphoblastic leukemia (ALL), thus providing compelling evidence for genetic inheritance of this blood cancer. In particular, hematopoietic transcription factors (eg, ETV6, PAX5, IKZF1) are most frequently implicated in familial ALL, and germline variants in these genes confer strong predisposition (albeit with incomplete penetrance). Studies of germline risk factors for ALL provide unique insights into the molecular etiology of this leukemia.

Predisposing germline mutations in high hyperdiploid acute lymphoblastic leukemia in children

High hyperdiploidy (HD) is the most common cytogenetic subtype of childhood acute lymphoblastic leukemia (ALL), and a higher incidence of HD has been reported in ALL patients with congenital cancer syndromes. We assessed the frequency of predisposing germline mutations in 57 HD-ALL patients from the California Childhood Leukemia Study via targeted sequencing of cancer-relevant genes. Three out of 57 patients (5.3%) harbored confirmed germline mutations that were likely causal, in NBN, ETV6, and FLT3, with an additional six patients (10.5%) harboring putative predisposing mutations that were rare in unselected individuals (<0.01% allele frequency in the Exome Aggregation Consortium, ExAC) and predicted functional (scaled CADD score ≥ 20) in known or potential ALL predisposition genes (SH2B3, CREBBP, PMS2, MLL, ABL1, and MYH9). Three additional patients carried rare and predicted damaging germline mutations in GAB2, a known activator of the ERK/MAPK and PI3K/AKT pathways and binding partner of PTPN11-encoded SHP2. The frequency of rare and predicted functional germline GAB2 mutations was significantly higher in our patients (2.6%) than in ExAC (0.28%, P = 4.4 × 10^-3 ), an observation that was replicated in ALL patients from the TARGET project (P = .034). We cloned patient GAB2 mutations and expressed mutant proteins in HEK293 cells and found that frameshift mutation P621fs led to reduced SHP2 binding and ERK1/2 phosphorylation but significantly increased AKT phosphorylation, suggesting possible RAS-independent leukemogenic effects. Our results support a significant contribution of rare, high penetrance germline mutations to HD-ALL etiology, and pinpoint GAB2 as a putative novel ALL predisposition gene.

LNK suppresses interferon signaling in melanoma

LNK (SH2B3) is a key negative regulator of JAK-STAT signaling which has been extensively studied in malignant hematopoietic diseases. We found that LNK is significantly elevated in cutaneous melanoma; this elevation is correlated with hyperactive signaling of the RAS-RAF-MEK pathway. Elevated LNK enhances cell growth and survival in adverse conditions. Forced expression of LNK inhibits signaling by interferon-STAT1 and suppresses interferon (IFN) induced cell cycle arrest and cell apoptosis. In contrast, silencing LNK expression by either shRNA or CRISPR-Cas9 potentiates the killing effect of IFN. The IFN-LNK signaling is tightly regulated by a negative feedback mechanism; melanoma cells exposed to IFN upregulate expression of LNK to prevent overactivation of this signaling pathway. Our study reveals an unappreciated function of LNK in melanoma and highlights the critical role of the IFN-STAT1-LNK signaling axis in this potentially devastating disease. LNK may be further explored as a potential therapeutic target for melanoma immunotherapy.

LNK is a tumor suppressor in hematopoietic cancers, but its function in melanoma is unclear. Here, the authors show that the overexpression of LNK in melanomas correlate with hyperactive signaling of the RAS-RAF-MEK pathway and LNK enhances melanoma growth and survival and immune evasion by inhibiting IFN signalling.

SH2B3 inactivation through CN-LOH 12q is uniquely associated with B-cell precursor ALL with iAMP21 or other chromosome 21 gain

In more than 30% of B-cell precursor acute lymphoblastic leukaemia (B-ALL), chromosome 21 sequence is overrepresented through aneuploidy or structural rearrangements, exemplified by intrachromosomal amplification of chromosome 21 (iAMP21). Although frequent, the mechanisms by which these abnormalities promote B-ALL remain obscure. Intriguingly, we found copy number neutral loss of heterozygosity (CN-LOH) of 12q was recurrent in iAMP21-ALL, but never observed in B-ALL without some form of chromosome 21 gain. As a consequence of CN-LOH 12q, mutations or deletions of the adaptor protein, SH2B3, were converted to homozygosity. In patients without CN-LOH 12q, bi-allelic abnormalities of SH2B3 occurred, but only in iAMP21-ALL, giving an overall incidence of 18% in this sub-type. Review of published data confirmed a tight association between overrepresentation of chromosome 21 and both CN-LOH 12q and SH2B3 abnormalities in B-ALL. Despite relatively small patient numbers, preliminary analysis linked 12q abnormalities to poor outcome in iAMP21-ALL (p = 0.03). Homology modelling of a leukaemia-associated SH2 domain mutation and in vitro analysis of patient-derived xenograft cells implicated the JAK/STAT pathway as one likely target for SH2B3 tumour suppressor activity in iAMP21-ALL.

CDKN2B downregulation and other genetic characteristics in T-acute lymphoblastic leukemia

We identified principal genetic alterations in 97.1% (99/102) of patients with T-acute lymphoblastic leukemia (T-ALL) using integrative genetic analyses, including massive parallel sequencing and multiplex ligation-dependent probe amplification (MLPA). A total of 133 mutations were identified in the following genes in descending order: NOTCH1 (66.7%), FBXW7 (19.6%), PHF6 (15.7%), RUNX1 (12.7%), NRAS (10.8%), and DNMT3A (9.8%). Copy number alterations were most frequently detected in CDKN2B, CDKN2A, and genes on 9p21.3 in T-ALL (45.1%). Gene expression data demonstrated the downregulation of CDKN2B in most cases of T-ALL, whereas CDKN2A downregulation was mainly restricted to deletions. Additional quantitative methylation analysis demonstrated that CDKN2B downregulation stemmed from deletion and hypermethylation. Analysis of 64 patients with CDKN2B hypermethylation indicated an association with an older age of onset and early T cell precursor ALL, which involved very early arrest of T cell differentiation. Genes associated with methylation and myeloid neoplasms, including DNMT3A and NRAS, were more commonly mutated in T-ALL with CDKN2B hypermethylation. In particular, a CDKN2B biallelic deletion or high methylation level (≥45%), the age of onset, and the GATA3 and SH2B3 mutations were factors associated with a poor prognosis. This study clarifies that one of the most important genetic events in T-ALL, namely, CDKN2B downregulation, occurs mechanistically via deletion and hypermethylation. Different susceptible genetic backgrounds exist based on the CDKN2B downregulation mechanism.

Advances in B-cell Precursor Acute Lymphoblastic Leukemia Genomics

In childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL), cytogenetic abnormalities remain important diagnostic and prognostic tools. A number of well-established abnormalities are routinely used in risk stratification for treatment. These include high hyperdiploidy and ETV6-RUNX1 fusion, classified as good risk, while Philadelphia chromosome (Ph) positive ALL and rearrangements of the KMT2A (MLL) gene define poor risk. A poor risk subgroup of intrachromosomal amplification of chromosome 21 (iAMP21-ALL) has been described, in which intensification of therapy has greatly improved outcome.

Until recently, no consistent molecular features were defined in around 30% of BCP-ALL (known as B-other-ALL). Recent studies are classifying them into distinct subgroups, some with clear potential for novel therapeutic approaches. For example, in 1 poor risk subtype, known as Ph-like/BCR-ABL1-like ALL, approximately 10% have rearrangements of ABL-class tyrosine kinases: including ABL1, ABL2, PDGFRB, PDGFRA, and CSF1R. Notably, they show a poor response to standard chemotherapy, while they respond to treatment with tyrosine kinase inhibitors, such as imatinib. In other Ph-like-ALL patients, deregulation of the cytokine receptor, CRLF2, and JAK2 rearrangements lead to activation of the JAK-STAT signaling pathway, implicating a specific role for JAK inhibitors in their treatment. Other novel subgroups within B-other-ALL are defined by the IGH-DUX4 translocation, related to deletions of the ERG gene and a good outcome, while fusions involving ZNF384, MEF2D, and intragenic PAX5 amplification (PAX5^AMP) are linked to a poor outcome. Continued genetic screening will eventually lead to complete genomic classification of BCP-ALL and define more molecular targets for less toxic therapies.

SH2B3 aberrations enriched in iAMP21 B lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) represents the most common childhood malignancy. Although survival for pediatric B-ALL has approached 90%, variability in outcome among and within cytogenetically defined subgroups persists. While G-banding and fluorescence in situ hybridization (FISH) have been used to characterize leukemic clones, there is added value of chromosomal microarray and next generation sequencing in screening genome-wide for copy number aberrations, copy neutral loss of heterozygosity and nucleotide variations. Evaluation of novel genetic aberrations can provide information about the biologic mechanisms of cytogenetically defined subgroups associated with poor prognosis, explain heterogeneity in patient outcome and identify novel targets for therapeutic intervention. The high risk B-ALL intrachromosomal amplification of chromosome 21, (iAMP21), subtype is characterized by amplification of a region of chromosome 21 that typically encompasses the RUNX1 gene and is associated with poor prognosis. Analysis of chromosomal microarray and FISH data revealed that deletions of SH2B3, encoding a negative regulator of multiple tyrosine kinase and cytokine signaling pathways, are enriched among leukemias harboring iAMP21. Enrichment of SH2B3 aberrations in the iAMP21 subtype may indicate that loss of SH2B3 contributes to disease progression and raises the possibility that these leukemias may be sensitive to tyrosine kinase inhibitors.

Global efforts toward the cure of childhood acute lymphoblastic leukaemia

Improvements in risk-directed treatment and supportive care, together with increased reliance on both national and international collaborative studies, have made childhood acute lymphoblastic leukaemia (ALL) one of the most curable human cancers. Next-generation sequencing studies of leukaemia cells and the host germline provide new opportunities for precision medicine and thus potential improvements in the cure rate and quality of life of patients. Efforts are underway to assess the global impact of childhood ALL and develop initiatives that can meet the long-term challenge of providing quality care to children with this disease worldwide and improving cure rates globally. This ambitious task will rely on increased collaborative research and international networking so that the therapeutic gains in high-income countries can be translated to patients in low-income and middle-income countries. Ultimately, the greatest obstacle to overcome will be to fully understand leukaemogenesis, enabling measures to decrease the risk of leukaemia development and thus close the last major gap in offering a cure to any child who might have the disease.

Deep targeted sequencing in pediatric acute lymphoblastic leukemia unveils distinct mutational patterns between genetic subtypes and novel relapse-associated genes

To characterize the mutational patterns of acute lymphoblastic leukemia (ALL) we performed deep next generation sequencing of 872 cancer genes in 172 diagnostic and 24 relapse samples from 172 pediatric ALL patients. We found an overall greater mutational burden and more driver mutations in T-cell ALL (T-ALL) patients compared to B-cell precursor ALL (BCP-ALL) patients. In addition, the majority of the mutations in T-ALL had occurred in the original leukemic clone, while most of the mutations in BCP-ALL were subclonal. BCP-ALL patients carrying any of the recurrent translocations ETV6-RUNX1, BCR-ABL or TCF3-PBX1 harbored few mutations in driver genes compared to other BCP-ALL patients. Specifically in BCP-ALL, we identified ATRX as a novel putative driver gene and uncovered an association between somatic mutations in the Notch signaling pathway at ALL diagnosis and increased risk of relapse. Furthermore, we identified EP300, ARID1A and SH2B3 as relapse-associated genes. The genes highlighted in our study were frequently involved in epigenetic regulation, associated with germline susceptibility to ALL, and present in minor subclones at diagnosis that became dominant at relapse. We observed a high degree of clonal heterogeneity and evolution between diagnosis and relapse in both BCP-ALL and T-ALL, which could have implications for the treatment efficiency.

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.

Co-existence of IL7R high and SH2B3 low expression distinguishes a novel high-risk acute lymphoblastic leukemia with Ikaros dysfunction

Acute lymphoblastic leukemia (ALL) remains the leading cause of cancer-related death in children and young adults. Compared to ALL in children, adult ALL has a much lower cure rate. Therefore, it is important to understand the molecular mechanisms underlying high-risk ALL and to develop therapeutic strategies that specifically target genes or pathways in ALL. Here, we explored the IL7R and SH2B3 expression in adult ALL and found that IL7R is significantly higher and Sh2B3 lower expressed in B-ALL compared to normal bone marrow control, and the IL7R^highSH2B3^low is associated with high-risk factors, and with high relapse rate and low disease-free survival rate in the patients. We also found that Ikaros deletion was associated with the IL7R^highSH2B3^low expression pattern and Ikaros directly binds the IL7R and SH2B3 promoter, and suppresses IL7R and promotes SH2B3 expression. On the other hand, casein kinase inhibitor, which increases Ikaros function, inhibits IL7R and stimulates SH2B3 expression in an Ikaros dependent manner. Our data indicate that IL7R^highSH2B3^low expression distinguishes a novel subset of high-risk B-ALL associated with Ikaros dysfunction, and also suggest the therapeutic potential for treatment that combines casein kinase inhibitor, as an Ikaros activator, with drugs that target the IL7R signaling pathway.

TP53 Germline Variations Influence the Predisposition and Prognosis of B-Cell Acute Lymphoblastic Leukemia in Children

Purpose Germline TP53 variation is the genetic basis of Li-Fraumeni syndrome, a highly penetrant cancer predisposition condition. Recent reports of germline TP53 variants in childhood hypodiploid acute lymphoblastic leukemia (ALL) suggest that this type of leukemia is another manifestation of Li-Fraumeni syndrome; however, the pattern, prevalence, and clinical relevance of TP53 variants in childhood ALL remain unknown. Patients and Methods Targeted sequencing of TP53 coding regions was performed in 3,801 children from the Children's Oncology Group frontline ALL clinical trials, AALL0232 and P9900. TP53 variant pathogenicity was evaluated according to experimentally determined transcriptional activity, in silico prediction of damaging effects, and prevalence in non-ALL control populations. TP53 variants were analyzed for their association with ALL presenting features and treatment outcomes. Results We identified 49 unique nonsilent rare TP53 coding variants in 77 (2.0%) of 3,801 patients sequenced, of which 22 variants were classified as pathogenic. TP53 pathogenic variants were significantly over-represented in ALL compared with non-ALL controls (odds ratio, 5.2; P < .001). Children with TP53 pathogenic variants were significantly older at ALL diagnosis (median age, 15.5 years v 7.3 years; P < .001) and were more likely to have hypodiploid ALL (65.4% v 1.2%; P < .001). Carrying germline TP53 pathogenic variants was associated with inferior event-free survival and overall survival (hazard ratio, 4.2 and 3.9; P < .001 and .001, respectively). In particular, children with TP53 pathogenic variants were at a dramatically higher risk of second cancers than those without pathogenic variants, with 5-year cumulative incidence of 25.1% and 0.7% ( P < .001), respectively. Conclusion Loss-of-function germline TP53 variants predispose children to ALL and to adverse treatment outcomes with ALL therapy, particularly the risk of second malignant neoplasms.