NG2 Molecule Expression in Acute Lymphoblastic Leukemia B Cells: A Flow-Cytometric Marker for the Rapid Identification of KMT2A Gene Rearrangements.

Background: B-lineage acute lymphoblastic leukemias (B-ALL) harboring rearrangements of the histone lysine [K]-Methyltransferase 2A (KMT2A) gene on chromosome 11q23 (KMT2A-r) represent a category with dismal prognosis. The prompt identification of these cases represents an urgent clinical need. Considering the correlation between rat neuron glial-antigen 2 (NG2) chondroitin-sulfate-proteoglycan molecule expression and KMT2A-r, we aimed to identify an optimized cytofluorimetric diagnostic panel to predict the presence of KMT2A-r. Materials and Methods: We evaluated 88 NG2+ B-ALL cases identified with an NG2 positivity threshold >10% from a cohort of 1382 newly diagnosed B-ALLs referred to the Division of Hematology of 'Sapienza' University of Rome. Results: Eighty-five of 88 (96.6%) NG2+ B-ALLs harbored KMT2A-r and were mainly pro-B ALL (77/85; 91%). Only 2 B-ALLs with KMT2A-r showed NG2 expression below 10%, probably due to the steroid therapy administered prior to cytofluorimetric analysis.Compared to KMT2A-r-cases, KMT2A r+ B-ALLs showed a higher blast percentage, significantly higher mean fluorescence intensity (MFI) of CD45, CD38, and CD58, and significantly lower MFI of CD34, CD22, TdT, and CD123.The study confirmed differences in CD45, CD34, CD22, and TdT MFI within the same immunologic EGIL group (European Group for the immunological classification of leukemias), indicating no influence of the B-ALLs EGIL subtype on the KMT2A-r+ B-ALLs immunophenotype. Conclusions: Our data demonstrate the association between NG2 and KMT2A-r in B-ALLs identify a distinctive immunophenotypic pattern, useful for rapid identification in diagnostic routines of these subtypes of B-ALLs with a poor prognosis that benefits from a specific therapeutic approach.

Diagnostic approach to a paediatric patient with Wiedemann-Steiner syndrome with de novo missense variant in the KMT2A gene - a case report.

INTRODUCTION: Wiedemann-Steiner syndrome is caused by mutations in the KMT2A gene (11q23.3). It might be inherited autosomal dominant or appear de novo. Features described in the syndrome include developmental delay, short stature, hypotonia, hypertrichosis, facial dysmorphic features, and intellectual disability. CASE REPORT: A boy aged 5.5 months was admitted to the Genetics Outpatient Clinic due to delayed psychomotor development. Microsomia, hypotonia, joint laxity, and facial dysmorphic features were noticed. No genomic imbalance was found in microarray, based on comparative genomic hybridization. The c.3528G>T variant of the KMT2A gene was identified on chromosome 11 of the missense type in next-generation sequencing. The reasons for phenotypic features were confirmed in genetic research. CONCLUSIONS: Wiedemann-Steiner syndrome has a variable clinical phenotype. There is a strong need to pay attention to phenotypic features that may suggest the syndrome and refer patients for appropriate genetic diagnostics.

Rearrangement of KMT2A Characterizes a Subset of Pediatric Parotid Mucoepidermoid Carcinomas Arising Metachronous to Acute Lymphoblastic Leukemia.

Introduction: Metachronous mucoepidermoid carcinomas (MMEC) may occur in association with childhood leukemias and lymphomas. We compared molecular abnormalities of MMEC in patients with ALL with the abnormalities found in primary mucoepidermoid carcinomas (MECs) in pediatric cases and young adults. Materials and methods: Immunohistochemical stains for p63 and SOX10, molecular alterations in MAML2 and KMT2A genes detected by FISH and/or next-generation sequencing were studied in 12 pediatric MMECs secondary to ALL and six primary MECs in pediatric patients and young adults. Follow-up information of patients in both groups was obtained. Results: KMT2A rearrangements were detected in pediatric MMECs, and they were associated with remarkable histomorphological changes, including deposits of abundant stromal collagen and intratumoral lymphoid proliferations. No KMT2A rearrangements were found in primary MECs. The prognosis of MMEC in patients with ALL, especially in KMT2A-rearranged cases, was worse than in primary MECs. Kruskal-Wallis test showed a statistically significant difference in overall survival between KMT2A-rearranged MMECs and KMT2A-intact MMECs in cases with ALL (p = 0.027). Conclusion: KMT2A-rearranged MMECs in ALL patients may have inherently more aggressive behavior, even when the histomorphology of MMEC suggests a low-grade malignancy.

Infantile B-lymphoblastic leukemia: a case series and review of the literature.

Infantile leukemia is a rare hematological malignancy that occurs in the first year of life. It is an aggressive disease with peculiar immunophenotypic, cytogenetic, and molecular characteristics. It can be myeloid or lymphoid in origin. More than 80% of cases involve KMT2A gene rearrangement in the lymphoblastic subset, versus 50% in the myeloid subset. In this study, we present three cases of this rare entity to add knowledge about its clinical presentation and diagnostic profiles. These cases of infantile B-lymphoblastic leukemia (B-ALL) were retrospectively reviewed at the Department of Hematology, Section Cytogenetics at Indus Hospital and Health Network. The clinical characteristics, complete diagnostic profile, immunophenotypic profile, fluorescence in situ hybridization (FISH) results, treatments, and outcomes of the patients were assessed. All three infants were girls who presented with hyperleukocytosis, and they were diagnosed by eight-color flow cytometry. FISH studies revealed KMT2A gene rearrangement in two of the three patients. Infantile B-ALL is a biologically distinct disease carrying a poor prognosis. Female preponderance, hyperleukocytosis, and hepatosplenomegaly are common findings in this subgroup. No standard protocol for this rare entity has proven ideal for managing these young infants.

Novel variants and phenotypic heterogeneity in a cohort of 11 Chinese children with Wiedemann-Steiner syndrome.

Objective: Wiedemann-Steiner syndrome (WSS) is a rare autosomal dominant disorder caused by deleterious heterozygous variants of the KMT2A gene. This study aims to describe the phenotypic and genotypic features of Chinese WSS patients, and assess therapeutic effects of recombinant human growth hormone (rhGH). Methods: Eleven Chinese children with WSS were enrolled in our cohort. Their clinical, imaging, biochemical and molecular findings were analyzed retrospectively. Moreover, the phenotypic features of 41 previously reported Chinese WSS patients were reviewed and included in our analysis. Results: In our cohort, the 11 WSS patients presented with classic clinical manifestations, but with different frequencies. The most common clinical features were short stature (90.9%) and developmental delay (90.9%), followed by intellectual disability (72.7%). The most frequent imaging features were patent ductus arteriosus (57.1%) and patent foramen ovale (42.9%) in cardiovascular system, and abnormal corpus callosum (50.0%) in the brain. In the set comprising 52 Chinese WSS patients, the most common clinical and imaging manifestations were developmental delay (84.6%), intellectual disability (84.6%), short stature (80.8%) and delayed bone age (68.0%), respectively. Eleven different variants, including three known and eight novel variants, of the KMT2A gene were identified in our 11 WSS patients without a hotspot variant. Two patients were treated with rhGH and yielded satisfactory height gains, but one developed acceleration of bone age. Conclusion: Our study adds 11 new patients with WSS, reveals different clinical characteristics in Chinese WSS patients, and extends the mutational spectrum of the KMT2A gene. Our study also shares the therapeutic effects of rhGH in two WSS patients without GH deficiency.

Targeting FLT3-specific chimeric antigen receptor T cells for acute lymphoblastic leukemia with KMT2A rearrangement.

CD19-specific chimeric antigen receptor T (CAR T) immunotherapy is used to treat B-cell malignancies. However, antigen-escape mediated relapse following CAR T therapy has emerged as a major concern. In some relapsed cases, especially KMT2A rearrangement-positive B-acute lymphoblastic leukemia (KMT2A-r B-ALL), most of the B-cell antigens are lost via lineage conversion to the myeloid phenotype, rendering multi-B-cell-antigen-targeted CAR T cell therapy ineffective. Fms-related tyrosine kinase-3 (FLT3) is highly expressed in KMT2A-r B-ALL; therefore, in this study, we aimed to evaluate the antitumor efficacy of CAR T cells targeting both CD19 and FLT3 in KMT2A-r B-ALL cells. We developed piggyBac transposon-mediated CAR T cells targeting CD19, FLT3, or both (dual) and generated CD19-negative KMT2A-r B-ALL models through CRISPR-induced CD19 gene-knockout (KO). FLT3 CAR T cells showed antitumor efficacy against CD19-KO KMT2A-r B-ALL cells both in vitro and in vivo; dual-targeted CAR T cells showed cytotoxicity against wild-type (WT) and CD19-KO KMT2A-r B-ALL cells, whereas CD19 CAR T cells demonstrated cytotoxicity only against WT KMT2A-r B-ALL cells in vitro. Therefore, targeting FLT3-specific CAR T cells would be a promising strategy for KMT2A-r B-ALL cells even with CD19-negative relapsed cases.

Partial tandem duplication of KMT2A gene in patient afflicted with hypereosinophilic syndrome: A case report.

Eosinophilia is defined as a condition with increased eosinophil cell counts in blood more than the standard value. In this regard, when extensive evaluation fails to reveal the underlying causes of this disease, hypereosinophilic syndrome (HES) diagnosis should be considered. Moreover, it is possible that the mutation of the tyrosine kinase genes, as the most common type of cryptic mutations, is associated with HES syndrome. We report a case of a 47-year-old man who was initially diagnosed with HES by Microscopic examination of bone marrow aspiration and peripheral blood cell analysis. After diagnosis, the patient was administered with cortisone acetate, leading to an initial remission. One month after the initial remission, the disease relapsed, and the patient eventually died. This case report provides the first report of HES, in which a novel variant of partial tandem duplication (PTD) was detected in the KMT2A gene.

[Treatment strategy for infant acute lymphoblastic leukemia].

Infant acute lymphoblastic leukemia (ALL), which develops in the first year of life, is a rare disease with approximately 20 cases per year in Japan. In particular, KMT2A (MLL) gene rearranged ALL (KMT2A-rALL) has a dismal prognosis, with a 5-year event-free survival rate of <50%. Moreover, acute and late severe toxicities from infants' intensive treatment remain an issue. Although outcomes of domestic and international clinical trials appear to improve gradually, the problem remains intractable. Therefore, introducing more appropriate risk stratification and less toxic and more effective novel treatment strategies is urgently required to improve the prognosis and long-term survival of infants with ALL. To achieve these goals, establishing new treatment strategies using novel agents through international collaborative studies is warranted in the future.

Clinical Utility of a Unique Genome-Wide DNA Methylation Signature for KMT2A-Related Syndrome.

Wiedemann-Steiner syndrome (WDSTS) is a Mendelian syndromic intellectual disability (ID) condition associated with hypertrichosis cubiti, short stature, and characteristic facies caused by pathogenic variants in the KMT2A gene. Clinical features can be inconclusive in mild and unusual WDSTS presentations with variable ID (mild to severe), facies (typical or not) and other associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Interpretation and classification of rare KMT2A variants can be challenging. A genome-wide DNA methylation episignature for KMT2A-related syndrome could allow functional classification of variants and provide insights into the pathophysiology of WDSTS. Therefore, we assessed genome-wide DNA methylation profiles in a cohort of 60 patients with clinical diagnosis for WDSTS or Kabuki and identified a unique highly sensitive and specific DNA methylation episignature as a molecular biomarker of WDSTS. WDSTS episignature enabled classification of variants of uncertain significance in the KMT2A gene as well as confirmation of diagnosis in patients with clinical presentation of WDSTS without known genetic variants. The changes in the methylation profile resulting from KMT2A mutations involve global reduction in methylation in various genes, including homeobox gene promoters. These findings provide novel insights into the molecular etiology of WDSTS and explain the broad phenotypic spectrum of the disease.

[Infant acute lymphoblastic leukemia: treatment strategies and new insights].

Acute lymphoblastic leukemia (ALL) in infants, especially KMT2A gene rearranged ALL (KMT2A-rALL), is a rare disease. Its prognosis is extremely poor, with a reported long-term event-free survival rate of ≤50%. In addition, acute and late toxicities caused by intensive treatment remain issues to be resolved. In the context of this background, the introduction of a more appropriate stratification and a novel treatment with minimal toxicities are urgently required. Establishment of evidence-based novel treatment strategies through an international collaborative study is important owing to the rarity of the disease. Currently, an international collaborative study with a European study group, which includes blinatumomab combined therapy, has been proposed. We herein review previous key clinical trials and the latest treatment strategies for infant ALL.

Wiedemann-Steiner syndrome in two patients from Portugal.

Wiedemann-Steiner syndrome (WSS) is a rare genetic disorder characterized by growth retardation, facial dysmorphism, hypertrichosis cubiti and neurodevelopment delay. It is caused by pathogenic variants in the KMT2A gene. This report describes two unrelated Portuguese patients, age 11 and 17 years, with a phenotype concordant with WSS and clinical and molecular diagnosis of WSS by the identification of two novel frameshift variants in the KMT2A gene. This work also highlights the presence of certain clinical features in patients with growth retardation and development delay and should draw attention to the diagnosis of WSS, when hirsutism, particularly hypertrichosis cubiti is present.

Therapy-related acute lymphoblastic leukemia: Where do we stand with regards to its definition and characterization?

Acute lymphoblastic leukemia (ALL) arising in patients with prior malignancy is increasingly being reported. Although terms such as 'secondary' and 'therapy-related' have been interchangeably used to characterize these cases of ALL in a similar fashion to acute myeloid leukemia (AML), it must be noted that some reported cases have not had exposure to cytotoxic therapy and hence a causal relationship between the prior malignancy and subsequent ALL is difficult to establish. Therefore, the use of the term secondary ALL to describe such cases without exposure to cytotoxic therapy is preferably avoided and will not be discussed here. ALL related to prior cytotoxic therapy (t-ALL) appears to be a distinct entity when compared to the de novo ALL, with characteristics including older age at the time of onset, female predominance and leukemia genetics enriched with KMT2A (MLL) gene rearrangement and chromosomes 5/7 abnormalities. Outcome of t-ALL appears inferior to de novo ALL when treated with conventional combination chemotherapy and this adverse outcome may be related to unfavorable patient factors as well as high risk genetic features of the disease itself. Additional genomic and molecular studies are needed to better characterize pathologic features of ALL arising after exposure to cytotoxic therapy in patients with prior malignancies.

A novel de novo mutation (p.Pro1310Glnfs*46) in KMT2A caused Wiedemann-Steiner Syndrome in a Chinese boy with postnatal growth retardation: a case report.

Wiedemann-Steiner Syndrome (WSS) is a very rare autosomal dominant disease. Mutations in the KMT2A gene have been shown to cause this disease. A 1-year-old Chinese boy exhibited growth delay, psychomotor retardation, limb hypotonia and facial dysmorphism that was consistent with WSS. His body weight started to drop below the normal range at 3 months old, and the decline persisted. Whole-exome sequencing showed a novel de novo mutation (p.Pro1310Glnfs*46) in KMT2A, which confirmed the diagnosis of WSS. We diagnosed a Chinese boy who presented postnatal growth retardation with WSS caused by a novel de novo mutation in KMT2A. Our findings expand the mutational and phenotypic spectra of WSS and will be valuable for the mutation-based pre- and postnatal screening for and genetic diagnosis of WSS.

Wiedemann-Steiner syndrome caused by novel mutation of KMT2A gene: one case report and literature review / 中华内分泌代谢杂志

Objective To analyze the clinical and biochemical,as well as genetic characteristics of a patient with Wiedemann-Steiner syndrome (WDSTS).Methods The clinical data of a patient with WDSTS were collected.The patient was treated with recombinant human growth hormone (rhGH) combined with gonadotrophine-releasing hormone agonist (GnRHa).Blood samples of the patient and her parents were taken for whole-Exome Sequencing (WES).Relevant literatures about KMT2A mutations were reviewed.Results The 5-year old girl presented with growth retardation,with height 100 cm (-2.4 SD),torpid reaction,and facial anomalies including low hairline,thick eyebrow and hair,hypertelorism,a wide nasal bridge.She had small and puffy hands and feet,excessive hair around back of neck,bilateral forearm and lower limbs.Her GH peak level was 26.6 ng/ml during GH stimulation test.She was re-examined at the age of 10.4 years,with severe short stature (120 cm/-3.58 SD) and a Tanner stage 2 of breast development.Her bone age was found to be approximately 11.4 years.Height increased from 120 cm at the age of 10.4 years to 147.3 cm after rhGH treatment combined with GnRHa for 2.5 years.rhGH therapy alone continued for 1.1 years and a height of 150 cm was reached at the age of 14.9 years,with bone age 14 years.Gene sequencing revealed a de novo frameshift mutation (c.10051 delA,p.Thr3351 Leufs * 17) of exon 27 in KMT2A gene of the patient,but without any mutation in her parents.Through a literature review,seventy-one patients with WDSTS (including present case) presented with intellectual disability (70/71),facial anomalies (70/71),short stature (50/71),and hypertrichosis (39/71).Conclusion Patients presented with short stature,typical facial dysmorphism,intellectual disability,and hypertrichosis should be considered for WDSTS.The mutation p.Thr3351Leufs * 17 in the KMT2A gene detected in our patient is a novel mutation.This is so far the first report of WDSTS patient who was successfully treated with a combination of GH and GnRHa at the onset of puberty to improve her adult height.

A Case of Acute Myeloid Leukemia with Novel Translocation t(6;11)(p22.2;q23) and Concurrent Insertion ins(11;9)(q23;p21.3p21.3).

We describe the case of a boy with acute myeloid leukemia with translocation t(6;11)(p22.2;q23) and insertion ins(11;9)(q23;p21.3p21.3). Translocation t(6;11)(p22.2;q23) involving the short arm of chromosome 6 has not been previously described. The LDI-PCR showed the presence of KMT2A-MLLT3 fusion and identified the BTN3A1 (butyrophilin subfamily 3 member A1) gene on 6p22.2 as the other KMT2A translocation partner. The BTN3A1 gene has never been described in the context of acute leukemia. Although this fusion is out of frame, as the antisense strand of BTN3A1 is fused to the sense strand of KMT2A, the loss of heterozygosity of the BTN3A1 gene might contribute to the malignancy of leukemic cells.