[FLT3-ITD mutation-positive acute myeloid leukemia undergoing clonal transition with PTPN11 mutation at relapse].

A 28-year-old man was diagnosed with acute myelomonocytic leukemia. He achieved complete remission (CR) after two cycles of induction therapy. However, after consolidation therapy, bone marrow aspiration performed to prepare for allogeneic hematopoietic stem cell transplantation revealed disease relapse. Companion diagnostics confirmed the presence of the FLT3-ITD mutation. The patient received gilteritinib monotherapy and achieved CR. Subsequently, he underwent unrelated allogeneic bone marrow transplantation. One year after transplantation, the patient relapsed, and gilteritinib was resumed. However, the leukemia progressed, and panel sequencing using a next-generation sequencer showed that the FLT3-ITD mutation disappeared. A mutation in PTPN11, which regulates the RAS/MAPK signaling pathway, was also detected. Gilteritinib was discontinued, and the patient achieved CR with salvage chemotherapy. He underwent related haploidentical peripheral blood stem cell transplantation but died of relapse. This was a case in which genetic analysis revealed clonal transition and acquisition of resistance to treatment.

Gilteritinib Affects the Selection of Dominant Clones in Clonal Hematopoiesis: Sequential Genetic Analysis of an FLT3-ITD Positive AML Patient with Long-Term Gilteritinib Therapy.

We performed sequential molecular analyses of a 75-year-old woman with de novo FLT3-ITD positive acute myeloid leukemia (AML) who had received gilteritinib therapy for 43 months. At the time of diagnosis, her karyotype was normal; however, FLT3-ITD, NPM1, DNMT3A, and IDH2 mutations were detected. She received induction therapy with daunorubicin and cytarabine and achieved hematological complete remission (HCR). After attaining HCR, she underwent consolidation therapy with azacytidine or cytarabine, aclarubicin, and granulocyte-colony stimulating factor. However, AML relapsed eight months after the first HCR. FLT3-ITD and NPM1 mutations were persistently positive, and the patient received gilteritinib therapy. Although the FLT3-ITD clone was not detected during gilteritinib treatment, a clone harboring monosomy 7 and CBL mutations emerged. Bone marrow examinations at 15, 24, and 32 months after gilteritinib treatment revealed multi-lineage blood cell dysplasia without an increase in myeloblasts. After 33 months of treatment, gilteritinib was discontinued for two months because to ileus development, and the FLT3-ITD clone was detected again. Gilteritinib treatment was restarted, and FLT3-ITD became negative. Our analysis demonstrated that: (1) hematopoiesis derived from gilteritinib-resistant clones was generated by long-term gilteritinib treatment, and (2) FLT3-ITD clones regained clonal dominance in the absence of FLT3 inhibition. These findings suggest that gilteritinib affects the selection of dominant clones during clonal hematopoiesis.

The early neutrophil-committed progenitors aberrantly differentiate into immunoregulatory monocytes during emergency myelopoiesis.

Inflammatory stimuli cause a state of emergency myelopoiesis leading to neutrophil-like monocyte expansion. However, their function, the committed precursors, or growth factors remain elusive. In this study we find that Ym1+Ly6Chi monocytes, an immunoregulatory entity of neutrophil-like monocytes, arise from progenitors of neutrophil 1 (proNeu1). Granulocyte-colony stimulating factor (G-CSF) favors the production of neutrophil-like monocytes through previously unknown CD81+CX3CR1lo monocyte precursors. GFI1 promotes the differentiation of proNeu2 from proNeu1 at the cost of producing neutrophil-like monocytes. The human counterpart of neutrophil-like monocytes that also expands in response to G-CSF is found in CD14+CD16- monocyte fraction. The human neutrophil-like monocytes are discriminated from CD14+CD16- classical monocytes by CXCR1 expression and the capacity to suppress T cell proliferation. Collectively, our findings suggest that the aberrant expansion of neutrophil-like monocytes under inflammatory conditions is a process conserved between mouse and human, which may be beneficial for the resolution of inflammation.

Impact of gene alterations on clinical outcome in young adults with myelodysplastic syndromes.

Young adults with myelodysplastic syndrome (MDS) are rare, and the clinical significance of driver mutations has not yet been analysed. We analysed the gene mutations and copy number alterations (CNAs) in younger MDS patients using next-generation sequencing, targeting 68 genes that were recurrently mutated in myeloid malignancies, to investigate the correlation between their genetic alterations and clinical outcomes. We enrolled 55 patients retrospectively (aged < 50 years). At least one mutation was detected in 56% of the patients. The most frequently mutated genes were ASXL1 and RUNX1, 13% each. We defined higher-risk patients as those with ≥ 2 mutations, except for SF3B1 mutation, and/or CNA. The 3-year overall survival (OS) in patients with a higher-risk was lower than that in those with a lower-risk (50.8% vs. 71.8%, P = 0.024). Among the 44 transplant recipients, patients with higher-risk had a significantly lower OS and tended to have a higher cumulative incidence of relapse (CIR) than those with a lower-risk (3-year OS: 38.0% vs. 64.4%, P = 0.039; 3-year CIR: 44.0% vs. 24.1%, P = 0.076). Our results showed that genetic aberrations can predict clinical outcomes in younger MDS patients, despite the low rate of genetic mutations.

Attenuated humoral response against SARS-CoV-2 mRNA vaccination in allogeneic stem cell transplantation recipients.

Antibody persistence several months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccination in allogeneic stem cell transplantation recipients remains largely unknown. We sequentially evaluated the humoral response to two doses of mRNA vaccines in 128 adult recipients and identified the risk factors involved in a poor response. The median interval between stem cell transplantation and vaccination was 2.7 years. The SARS-CoV-2 S1 Ab became positive after the second vaccination dose in 87.6% of the recipients, and the median titer was 1235.4 arbitrary units (AU)/ml. In patients on corticosteroid treatment, the corticosteroid dose inversely correlated with Ab titer. Multivariate analysis identified risk factors for poor peak response such as an interval from stem cell transplantation ≤1 year, history of clinically significant CMV infection, and use of >5 mg/day prednisolone at vaccination. Six months after vaccination, the median titer decreased to 185.15 AU/ml, and use of >5 mg/day prednisolone at vaccination was significantly associated with a poor response. These results indicate that early vaccination after stem cell transplantation (<12 months) and CMV infection are risk factors for poor peak response, while steroid use is important for a peak as well as a persistent response. In conclusion, although humoral response is observed in many stem cell transplantation recipients after two doses of vaccination, Ab titers diminish with time, and factors associated with persistence and a peak immunity should be considered separately.

Adult-onset hereditary myeloid malignancy and allogeneic stem cell transplantation.

Hereditary myeloid malignancies, especially in adults or elderly persons, had been considered quite rare before the next-generation sequencing era; however, increased usage of clinical sequencing has revealed much higher prevalence of inherited myeloid malignancies. DDX41 and various pathogenic germline mutations have newly been recognized as the cause of adult-onset familial leukemia and myeloid malignancies. Although germline predisposition to myeloid neoplasms had been categorized as a provisional entity in the World Health Organization classification of hematopoietic neoplasms in 2016, methodology for the identification of hereditary myeloid malignancies has not been fully established yet. In addition, many unresolved problems, such as epidemiology, the exact pathogenic mechanisms, and ideal treatment strategy, including indications of allogeneic hematopoietic stem cell transplantation, still remain. Related donor selection for stem cell transplant is a particularly sensitive issue due to the possibility of germline mutation of the candidate relatives and the risk of donor cell leukemia after transplantation. Here, we reviewed the current evidence regarding epidemiology, diagnosis, mechanisms of progression, and transplantation strategy for hereditary myeloid malignancies.

[Novel germline SAMD9 mutation in an elderly patient with myelodysplastic syndrome].

An 80-year-old Japanese male patient presented to our hospital with complaints of fatigue. His peripheral blood tests revealed pancytopenia with predominant lymphocytes and without blasts. The bone marrow (BM) aspiration was unsuccessful due to a dry tap, and the subsequent BM biopsy revealed hypocellular marrow with fibrosis. He was diagnosed with myelodysplastic syndrome (MDS) with excess blasts (EB)-2 based on CD34-positive cells. The chromosome analysis of the BM revealed monosomy 7, and the SAMD9 W22* mutation was detected (variant allele frequency [VAF] of 51.22%) using next-generation sequencing. An identical mutation was observed in the buccal mucosa (VAF of 50%), which was confirmed as a germline mutation. The SAMD9 gene mutation is reported as one of the causative genes for MIRAGE syndrome and child-onset MDS. The present case was considered a loss-of-function mutation due to the near full-length SAMD9 deletion. This is the first adult case of MDS with SAMD9 W22* as a germline mutation.

[Klinefelter's syndrome diagnosed at the onset of acute myeloid leukemia with inv (16) following treatment for germ cell tumor].

A 22-year-old man with a history of mediastinal germ cell tumor, which was diagnosed at age 20 and remained disease-free after chemotherapy, was diagnosed with acute myeloid leukemia (AML) M2 in January 2020. Karyotype analysis of bone marrow (BM) specimen at diagnosis detected 47,XXY, inv (16) in all cells. Following induction treatment, he achieved complete remission with a remarkable decrease in the minimal residual disease marker. Although considered related to therapy, the AML had a prognostically favorable karyotype, and the initial treatment response was very good. He had no human leukocyte antigen-matched sibling donor candidate. Thus, allogeneic hematopoietic stem cell transplantation was not scheduled at the first complete remission. After three cycles of consolidation therapy, he remained disease-free for over one year. Karyotype analysis of BM during remission revealed that all analyzed cells harbored 47,XXY, and Klinefelter syndrome (KS) was diagnosed. Although the patient experienced an adjustment disorder on KS diagnosis, he had overcome the difficulty with the assistance of psycho-oncologists, clinical psychologists, and genetic counselors. Herein, we report this rare case of KS that manifested after AML diagnosis following mediastinal germ cell tumor treatment.

Myeloid neoplasms and clonal hematopoiesis from the RUNX1 perspective.

RUNX1 is a critical transcription factor for the emergence of definitive hematopoiesis and the precise regulation of adult hematopoiesis. Dysregulation of its regulatory network causes aberrant hematopoiesis. Recurrent genetic alterations in RUNX1, including chromosomal translocations and mutations, have been identified in both inherited and sporadic diseases. Recent genomic studies have revealed a vast mutational landscape surrounding genetic alterations in RUNX1. Accumulating pieces of evidence also indicate the leukemogenic role of wild-type RUNX1 in certain situations. Based on these efforts, part of the molecular mechanisms of disease development as a consequence of dysregulated RUNX1-regulatory networks have become increasingly evident. This review highlights the recent advances in the field of RUNX1 research and discusses the critical roles of RUNX1 in hematopoiesis and the pathobiological function of its alterations in the context of disease, particularly myeloid neoplasms, and clonal hematopoiesis.

[A favorable clinical course of acute myeloid leukemia with t (6;21;8)(p23;q22;q22)].

Variants of the t (8;21) (q22;q22) involving chromosome 8, 21, and other chromosomes account for about 3% of all t (8;21) (q22;q22) in patients with acute myeloid leukemia (AML). However, the prognosis of AML with variant t (8;21) remains unknown due to the scarcity of reported cases. Herein we report a case of AML with t (6;21;8) (p23;q22;q22). Fluorescence in situ hybridization confirmed a RUNX1-RUNX1T1 fusion signal on the derivative chromosome 8. This is the first report on a variant of t (8;21) involving the breakpoint 6p23. After induction chemotherapy, our patient achieved complete remission and has been stable for four years.

Mitochondrial Fragmentation Triggers Ineffective Hematopoiesis in Myelodysplastic Syndromes.

Ineffective hematopoiesis is a fundamental process leading to the pathogenesis of myelodysplastic syndromes (MDS). However, the pathobiological mediators of ineffective hematopoiesis in MDS remain unclear. Here, we demonstrated that overwhelming mitochondrial fragmentation in mutant hematopoietic stem cells and progenitors (HSC/P) triggers ineffective hematopoiesis in MDS. Mouse modeling of CBL exon deletion with RUNX1 mutants, previously unreported comutations in patients with MDS, recapitulated not only clinically relevant MDS phenotypes but also a distinct MDS-related gene signature. Mechanistically, dynamin-related protein 1 (DRP1)-dependent excessive mitochondrial fragmentation in HSC/Ps led to excessive reactive oxygen species production, induced inflammatory signaling activation, and promoted subsequent dysplasia formation and impairment of granulopoiesis. Mitochondrial fragmentation was generally observed in patients with MDS. Pharmacologic inhibition of DRP1 attenuated mitochondrial fragmentation and rescued ineffective hematopoiesis phenotypes in mice with MDS. These findings provide mechanistic insights into ineffective hematopoiesis and indicate that dysregulated mitochondrial dynamics could be a therapeutic target for bone marrow failure in MDS. SIGNIFICANCE: We demonstrated that excessive mitochondrial fragmentation is a fundamental pathobiological phenomenon that could trigger dysplasia formation and ineffective hematopoiesis in MDS. Our findings provide mechanistic insights into ineffective hematopoiesis and suggest dysregulated mitochondrial dynamics as a therapeutic target for treating MDS.This article is highlighted in the In This Issue feature, p. 1.

Archival bone marrow smears are useful in targeted next-generation sequencing for diagnosing myeloid neoplasms.

Gene abnormalities, including mutations and fusions, are important determinants in the molecular diagnosis of myeloid neoplasms. The use of bone marrow (BM) smears as a source of DNA and RNA for next-generation sequencing (NGS) enables molecular diagnosis to be done with small amounts of bone marrow and is especially useful for patients without stocked cells, DNA or RNA. The present study aimed to analyze the quality of DNA and RNA derived from smear samples and the utility of NGS for diagnosing myeloid neoplasms. Targeted DNA sequencing using paired BM cells and smears yielded sequencing data of adequate quality for variant calling. The detected variants were analyzed using the bioinformatics approach to detect mutations reliably and increase sensitivity. Noise deriving from variants with extremely low variant allele frequency (VAF) was detected in smear sample data and removed by filtering. Consequently, various driver gene mutations were detected across a wide range of allele frequencies in patients with myeloid neoplasms. Moreover, targeted RNA sequencing successfully detected fusion genes using smear-derived, very low-quality RNA, even in a patient with a normal karyotype. These findings demonstrated that smear samples can be used for clinical molecular diagnosis with adequate noise-reduction methods even if the DNA and RNA quality is inferior.

Successful Cord Blood Transplantation for Idiopathic CD4+ Lymphocytopenia.

Idiopathic CD4+ lymphocytopenia (ICL) is the depletion of CD4+ lymphocytes to <300 cells/mm3 without human immunodeficiency virus infection or other causes of lymphocytopenia. ICL causes fatal infections; its etiology remains unclear and it lacks consensus regarding therapeutic options. We report the first patient with ICL who had a successful clinical course following a cord blood transplant (CBT). A 45-year-old woman was diagnosed with ICL and underwent partial hepatectomy for an abscess caused by the Mycobacterium avium complex. No specific gene alterations were detected through next generation sequencing-based evaluation. Following a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, busulfan, and 4 Gy total body irradiation, a single-unit CBT was performed. Neutrophils were engrafted on day +14. CD4+ lymphocyte counts increased to over 300 cells/mm3 on day +436. After 75 months, she was alive without any sequelae. CBT with an RIC regimen could be a curable treatment option for ICL.

Mutation profiles of diffuse large B-cell lymphoma transformation of splenic B-cell lymphoma/leukemia, unclassifiable on whole-exome sequencing.

A 58-year-old male was diagnosed with splenic B-cell lymphoma/leukemia, unclassifiable (SPLL-U). The lymphoma transformed into diffuse large B-cell lymphoma (DLBCL), and multidrug chemotherapy and autologous stem cell transplantation achieved complete remission. Two years later, the lymphoma relapsed as SPLL-U. Serial whole-exome sequencing indicated that the mutation profiles were similar between the onset and relapsed samples while those in DLBCL were partially distinctive, which was in line with the clinical course. Hierarchical clustering revealed that an IGLL5 mutation was the founder mutation proceeding the development of the diseases and suggested that KRAS and other mutations might contribute to the transformation.

Prognostic impact of TP53 mutation, monosomal karyotype, and prior myeloid disorder in nonremission acute myeloid leukemia at allo-HSCT.

Outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in nonremission acute myeloid leukemia (AML) are dismal [2-year overall survival (OS): 20-30%]. Though several risk classifications have been used, some factors are unavailable until the start of conditioning or transplantation. We analyzed prognostic gene mutations by targeted next-generation sequencing to identify predisposing factors for predicting OS at 1 month before transplantation. We enrolled 120 patients with nonremission AML who underwent first allo-HSCT between 2005 and 2018. Mutations were found in 98 patients; frequently mutated genes were FLT3-ITD, TP53, RUNX1, and WT1. TP53 mutation was detected in 21 patients and was the only predictor of poor OS. Multivariate analysis using Cox regression hazard model revealed primary AML, monosomal karyotype (MK), and TP53 mutation as independent factors for predicting poor OS. Based on these, patients were stratified into three groups. The low-risk group included patients with prior myeloid disorder without MK (n = 26). Among the rest, patients with TP53 mutation were assigned to the high-risk group (n = 19) and the rest into the intermediate-risk group (n = 75). Two-year OS in low-, intermediate-, and high-risk groups differed significantly (50.0%, 24.9%, and 0%, respectively). This suggests that the indication of allo-HSCT should be carefully judged for high-risk patients.

Overexpression of RUNX3 Represses RUNX1 to Drive Transformation of Myelodysplastic Syndrome.

RUNX3, a RUNX family transcription factor, regulates normal hematopoiesis and functions as a tumor suppressor in various tumors in humans and mice. However, emerging studies have documented increased expression of RUNX3 in hematopoietic stem/progenitor cells (HSPC) of a subset of patients with myelodysplastic syndrome (MDS) showing a worse outcome, suggesting an oncogenic function for RUNX3 in the pathogenesis of hematologic malignancies. To elucidate the oncogenic function of RUNX3 in the pathogenesis of MDS in vivo, we generated a RUNX3-expressing, Tet2-deficient mouse model with the pancytopenia and dysplastic blood cells characteristic of MDS in patients. RUNX3-expressing cells markedly suppressed the expression levels of Runx1, a critical regulator of hemaotpoiesis in normal and malignant cells, as well as its target genes, which included crucial tumor suppressors such as Cebpa and Csf1r. RUNX3 bound these genes and remodeled their Runx1-binding regions in Tet2-deficient cells. Overexpression of RUNX3 inhibited the transcriptional function of Runx1 and compromised hematopoiesis to facilitate the development of MDS in the absence of Tet2, indicating that RUNX3 is an oncogene. Furthermore, overexpression of RUNX3 activated the transcription of Myc target genes and rendered cells sensitive to inhibition of Myc-Max heterodimerization. Collectively, these results reveal the mechanism by which RUNX3 overexpression exerts oncogenic effects on the cellular function of and transcriptional program in Tet2-deficient stem cells to drive the transformation of MDS. SIGNIFICANCE: This study defines the oncogenic effects of transcription factor RUNX3 in driving the transformation of myelodysplastic syndrome, highlighting RUNX3 as a potential target for therapeutic intervention.