Germline SH2B3 pathogenic variant associated with myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis

Germline assessment for alloHSCT candidates over 50 years: A 'Fast-Track' screening in myeloid neoplasms

Patients aged 50 or above diagnosed with myeloid neoplasms (MNs) are typically not candidates for germline testing. However, approximately 8% carry pathogenic germline variants. Allogeneic haematopoietic stem cell transplantation (alloHSCT) remains an option for those aged over 50; neglecting germline testing could mask the risk for relative donor cell-derived MN. We propose a germline-augmented somatic panel (GASP), combining MN predisposition genes with a myeloid somatic panel for timely germline variant identification when initial testing is not indicated. Out of our 133 whole-exome-sequenced MN cases aged over 50 years, 9% had pathogenic/likely variants. GASP detected 92%, compared to 50% with somatic-only panel. Our study highlights the relevance of germline screening in MN, particularly for alloHSCT candidates without established germline-testing recommendations.

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.

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.

The Missing LNK: Evolution from Cytosis to Chronic Myelomonocytic Leukemia in a Patient with Multiple Sclerosis and Germline SH2B3 Mutation

Chronic myelomonocytic leukemia (CMML) is a rare but distinct hematological neoplasm with overlapping features of myelodysplastic syndrome (MDS) and myeloproliferative neoplasm (MPN). Individuals with CMML have persistent monocytosis and bone marrow dyspoiesis associated with various constitutional symptoms like fevers, unintentional weight loss, or night sweats. It is established that there is a strong association of CMML with preceding or coexisting autoimmune diseases and systemic inflammatory syndromes affecting around 20% of patients. Various molecular abnormalities like TET2, SRSF2, ASXL1, and RAS are reported in the pathogenesis of CMML, but no such mutations have been described to explain the strong association of autoimmune diseases and severe inflammatory phenotype seen in CMML. Germline mutation in SH2B adaptor protein 3 (SH2B3) had been reported before to affect a family with autoimmune disorders and acute lymphoblastic leukemia. In this report, we describe the first case of a female subject with many years of preceding history of multiple sclerosis before the diagnosis of CMML. We outline the evidence supporting the pathogenic role of SH2B3 p.E395K germline mutation, connecting the dots of association between autoimmune diseases and CMML genesis.

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.

Spectrum of hematological malignancies, clonal evolution and outcomes in 144 Mayo Clinic patients with germline predisposition syndromes

Germline predisposition syndromes (GPS) result from constitutional aberrations in tumor suppressive and homeostatic genes, increasing risk for neoplasia in affected kindred. In this study, we present clinical and genomic data on 144 Mayo Clinic patients with GPS; 59 evaluated prospectively using an algorithm-based diagnostic approach in the setting of a dedicated GPS/ inherited bone marrow failure syndrome (IBMFS) clinic. Seventy-two (50%) patients had IBMFS (telomere biology disorders-32,Fanconi anemia-18, Diamond Blackfan Anemia - 11, congenital neutropenia-5, Schwachman-Diamond Syndrome-5 and Bloom Syndrome-1), 27 (19%) had GPS with antecedent thrombocytopenia (RUNX1-FPD-15, ANKRD26-6, ETV6-2, GATA1-1, MPL-3), 28 (19%) had GPS without antecedent thrombocytopenia (GATA2 haploinsufficiency-16, DDX41-10, CBL-1 and CEBPA-1) and 17 (12%) had general cancer predisposition syndromes (ataxia telangiectasia-7, heterozygous ATM variants-3, CHEK2-2, TP53-2, CDK2NA-1, NF1-1 and Nijmegen Breakage Syndrome-1). Homozygous and heterozygous ATM pathogenic variants were exclusively associated with lymphoproliferative disorders (LPD), while DDX41 GPS was associated with LPD and myeloid neoplasms. The use of somatic NGS-testing identified clonal evolution in GPS patients, with ASXL1, RAS pathway genes, SRSF2 and TET2 being most frequently mutated. Fifty-two (91%) of 59 prospectively identified GPS patients had a change in their management approach, including additional GPS-related screening in 42 (71%), referral for allogenic HSCT workup and screening of related donors in 16 (27%), medication initiation and selection of specific conditioning regimens in 14 (24%), and genetic counseling with specific intent of fertility preservation and preconceptual counseling in 10 (17%) patients; highlighting the importance of dedicated GPS screening, detection and management programs for patients with hematological neoplasms.

Myelodysplastic syndromes with ring sideroblasts (MDS-RS) and MDS/myeloproliferative neoplasm with RS and thrombocytosis (MDS/MPN-RS-T) - "2021 update on diagnosis, risk-stratification, and management"

DISEASE OVERVIEW

Ring sideroblasts (RS) are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. Two myeloid neoplasms defined by the presence of RS, include myelodysplastic syndromes with RS (MDS-RS) and MDS/myeloproliferative neoplasm with RS and thrombocytosis (MDS/MPN-RS-T).

DIAGNOSIS

MDS-RS is a lower risk MDS, with single or multilineage dysplasia (MDS-RS-SLD/MLD), <5% bone marrow (BM) blasts, <1% peripheral blood blasts and ≥15% BM RS (≥5% in the presence of SF3B1 mutations). MDS/MPN-RS-T, now a formal entity in the MDS/MPN overlap syndromes, has diagnostic features of MDS-RS-SLD, along with a platelet count ≥450 × 10⁹ /L and large atypical megakaryocytes.

MUTATIONS AND KARYOTYPE

Mutations in SF3B1 are seen in ≥80% of patients with MDS-RS-SLD and MDS/MPN-RS-T, and strongly correlate with the presence of BM RS; MDS/MPN-RS-T patients also demonstrate JAK2V617F (50%), DNMT3A, TET2 and ASXL1 mutations. Cytogenetic abnormalities are uncommon in both.

RISK STRATIFICATION

Most patients with MDS-RS-SLD are stratified into lower risk groups by the revised-IPSS. Disease outcome in MDS/MPN-RS-T is better than that of MDS-RS-SLD, but worse than that of essential thrombocythemia (MPN). Both diseases are associated with a low risk of leukemic transformation.

TREATMENT

Anemia and iron overload are complications seen in both and are managed similar to lower risk MDS and MPN. Luspatercept, a first-in-class erythroid maturation agent is now approved for the management of anemia in patients with MDS-RS and MDS/MPN-RS-T. Aspirin therapy is reasonable in MDS/MPN-RS-T, especially in the presence of JAK2V617F, but the value of platelet-lowering drugs remains to be defined.

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.