[Chronic neutrophilic leukemia/chronic eosinophilic leukemia].

Chronic neutrophilic leukemia (CNL) is a clonal disorder that is characterized by increasing mature neutrophils. Colony stimulating factor 3 receptor (CSF3R) T618I mutation was frequently identified in patients with CNL and is defined as a molecular marker of the disease. Ruxolitinib, a JAK2 inhibitor, provided a promising therapeutic effect in a phase II study. In particular, ruxolitinib was more efficient for patients with CSF3R mutation. Allogeneic stem cell transplantation (Allo-SCT) may be a curative treatment for CNL. On the other hand, further studies are needed to define the optimal method of transplantation, source of donor, conditioning therapy, and timing of transplantation. Chronic eosinophilic leukemia (CEL) is a clonal disorder that is characterized by increasing eosinophils. In the World Health Organization Classification 5th edition, diagnostic criteria for CEL are renewed. Because the new criteria will be more specific for CEL than criteria in the older edition, "not otherwise specified (NOS) " is removed from the name of the disease. Anti-CD52 antibody, alemtuzumab, or anti-IL-5 antibody, mepolizumab, are promising drugs to control symptoms that are associated with hypereosinophilic syndrome. Allo-SCT is anticipated as a curative treatment for CEL, but the evidence of Allo-SCT for CEL is still limited. Further study is required to define the treatment strategy.

CSF3R-mutant chronic myelomonocytic leukemia is a distinct clinically subset with abysmal prognosis: a case report and systematic review of the literature.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) chacaterized by persistent peripheral blood monocytosis, hypercellular bone marrow and dysplasia at least in one myeloid lineage. CMML shares much of its molecular landscape with other myeloid neoplasms, while differs from others such as chronic neutrophilic leukemia (CNL), given the high frequency of CSF3R mutations in the latter. In this article, we report a case of CSF3R-mutated CMML and dissect this rare entity by reviewing the medical literature, with the intent to understand how this rare mutation shapes CMML's clinical and morphological phenotype. CSF3R-mutated CMML emerges as a rare entity meeting the ICC/WHO diagnostic criteria for CMML and simultaneously showing clinical-pathological and molecular traits of CNL and atypical chronic myeloid leukemia, rising an important and difficult diagnostic and therapeutical issue.

Chronic neutrophilic leukemia preceded by myelodysplastic syndromes.

Chronic neutrophilic leukemia (CNL) is primarily diagnosed by excluding myelodysplastic syndromes (MDS). We report the case of a patient who developed secondary CNL 3 years after hypoplastic MDS. We used droplet digital polymerase chain reaction mutation detection assay to analyze genomic alterations during the progression from MDS to CNL. At the time of MDS diagnosis, U2AF1 Q157P and SETBP1 D868N were dominant and additional mutation of ASXL1 1934_insG was observed. CSF3R T618I and SETBP1 D868N were increasing at the time of CNL diagnosis. We revealed the accumulation of multiple gene mutations during CNL development from MDS. This suggests that CNL was clonally developed from the founding clone of MDS and CSF3R mutation contributes to the development of CNL in the present case. These findings provide insights into the pathology of CNL.

Mutational screens highlight glycosylation as a modulator of colony-stimulating factor 3 receptor (CSF3R) activity.

The colony-stimulating factor 3 receptor (CSF3R) controls the growth of neutrophils, the most abundant type of white blood cell. In healthy neutrophils, signaling is dependent on CSF3R binding to its ligand, CSF3. A single amino acid mutation in CSF3R, T618I, instead allows for constitutive, ligand-independent cell growth and leads to a rare type of cancer called chronic neutrophilic leukemia. However, the disease mechanism is not well understood. Here, we investigated why this threonine to isoleucine substitution is the predominant mutation in chronic neutrophilic leukemia and how it leads to uncontrolled neutrophil growth. Using protein domain mapping, we demonstrated that the single CSF3R domain containing residue 618 is sufficient for ligand-independent activity. We then applied an unbiased mutational screening strategy focused on this domain and found that activating mutations are enriched at sites normally occupied by asparagine, threonine, and serine residues-the three amino acids which are commonly glycosylated. We confirmed glycosylation at multiple CSF3R residues by mass spectrometry, including the presence of GalNAc and Gal-GalNAc glycans at WT threonine 618. Using the same approach applied to other cell surface receptors, we identified an activating mutation, S489F, in the interleukin-31 receptor alpha chain. Combined, these results suggest a role for glycosylated hotspot residues in regulating receptor signaling, mutation of which can lead to ligand-independent, uncontrolled activity and human disease.

CNL and aCML should be considered as a single entity based on molecular profiles and outcomes.

Chronic neutrophilic leukemia (CNL) and atypical chronic myeloid leukemia (aCML) are rare myeloid disorders that are challenging with regard to diagnosis and clinical management. To study the similarities and differences between these disorders, we undertook a multicenter international study of one of the largest case series (CNL, n = 24; aCML, n = 37 cases, respectively), focusing on the clinical and mutational profiles (n = 53 with molecular data) of these diseases. We found no differences in clinical presentations or outcomes of both entities. As previously described, both CNL and aCML share a complex mutational profile with mutations in genes involved in epigenetic regulation, splicing, and signaling pathways. Apart from CSF3R, only EZH2 and TET2 were differentially mutated between them. The molecular profiles support the notion of CNL and aCML being a continuum of the same disease that may fit best within the myelodysplastic/myeloproliferative neoplasms. We identified 4 high-risk mutated genes, specifically CEBPA (ß = 2.26, hazard ratio [HR] = 9.54, P = .003), EZH2 (ß = 1.12, HR = 3.062, P = .009), NRAS (ß = 1.29, HR = 3.63, P = .048), and U2AF1 (ß = 1.75, HR = 5.74, P = .013) using multivariate analysis. Our findings underscore the relevance of molecular-risk classification in CNL/aCML as well as the importance of CSF3R mutations in these diseases.

Mutated SETBP1 activates transcription of Myc programs to accelerate CSF3R-driven myeloproliferative neoplasms.

Colony stimulating factor 3 receptor (CSF3R) mutations lead to JAK pathway activation and are the molecular hallmark of chronic neutrophilic leukemia (CNL). Approximately half of patients with CNL also have mutations in SET binding protein 1 (SETBP1). In this study, we developed models of SETBP1-mutated leukemia to understand the role that SETBP1 plays in CNL. SETBP1 mutations promote self-renewal of CSF3R-mutated hematopoietic progenitors in vitro and prevent cells from undergoing terminal differentiation. In vivo, SETBP1 mutations accelerate leukemia progression, leading to the rapid development of hepatosplenomegaly and granulocytosis. Through transcriptomic and epigenomic profiling, we found that SETBP1 enhances progenitor-associated programs, most strongly upregulating Myc and Myc target genes. This upregulation of Myc can be reversed by LSD1 inhibitors. In summary, we found that SETBP1 mutations promote aggressive hematopoietic cell expansion when expressed with mutated CSF3R through the upregulation of Myc-associated gene expression programs.

Co-Occurring CSF3R W791* Germline and Somatic T618I Driver Mutations Induce Early CNL and Clonal Progression to Mixed Phenotype Acute Leukemia.

Chronic neutrophilic leukemia (CNL) relates to mutational CSF3R activation with membrane proximal CSF3R mutations such as T618I as driver mutations, but the significance of truncating mutations is not clarified. In CNL, concomitant mutations promote disease progression, but insight into longitudinal acquisition is incomplete. In this study, we investigated the role of co-occurring germline and somatic CSF3R mutations in CNL, and assessed the impact of clonal evolution on transformation to acute leukemia. We employed sequential next generation sequencing and SNP array karyotyping to assess clonal evolution in CNL of early manifestation age based on a 33-year-old patient. Germline vs. somatic mutations were differentiated using a sample from the hair follicle. To investigate a potential predisposition for CNL development and progression by germline CSF3R-W791*, allelic localizations were evaluated. We detected a somatic CSF3R-T618I mutation at 46% variant allele frequency (VAF) at the time of CNL diagnosis, which co-occurred with a CSF3R-W791* truncation at 50% VAF in the germline. Evaluation of allelic localization revealed CSF3R-T618I and W791* on the same allele. A concomitant ASXL1 mutation at 39% VAF increased to 48% VAF upon transformation to mixed phenotype acute leukemia (MPAL), which has both myeloid and lymphoid features. Clonal evolution further involved expansion of the CSF3R double-mutant clone to 90% VAF via copy neutral loss of heterozygosity on chromosome 1p and the emergence of a RUNX1 mutant subclone. Allogeneic transplantation induced complete remission. This study highlights that CNL not only transforms to AML but also to MPAL. The molecular evolution is especially interesting with a CSF3R-W791* mutation in the germline and acquisition of CSF3R-T618I on the same allele compatible with increased susceptibility for mutation acquisition facilitating RUNX1-related clonal transformation.

Chronic neutrophilic leukemia complicated with monoclonal gammopathy of undetermined significance: A case report and literature review.

BACKGROUND: Study of the molecular biological characteristics of chronic neutrophilic leukemia complicated with plasma cell disorder (CNL-PCD) and lymphocytic proliferative disease (CNL-LPD). METHODS: The clinical data of a patient with chronic neutrophilic leukemia complicated with monoclonal gammopathy of undetermined significance (CNL-MGUS) in our hospital were reviewed, and the Chinese and/or English literature about CNL-PCD and CNL-LPD in PubMed and the Chinese database CNKI in the past 10 years was searched to analyze the molecular biological characteristics of this disease. RESULTS: A 73-year-old male had persistent leukocytosis for 18 months. The white blood cell count was 46.77 × 109/L and primarily composed of mature neutrophils; hemoglobin: 77 g/L; platelet count: 189 × 109/L. Serum immunofixation electrophoresis showed IgG-λ monoclonal M protein. A CT scan showed splenomegaly. Next-generation sequencing (NGS) showed that CSF3R T618I, ASXL1 and RUNX1 mutations were positive. It was diagnosed as CNL-MGUS. We summarized 10 cases of CNL-PCD and 1 case of CNL-LPD who underwent genetic mutation detection reported in the literature. The CSF3R mutational frequency (7/11, 63.6%) was lower than that of isolated CNL. The ASXL1 mutations were all positive (3/3), which may represent a poor prognostic factor. The SETBP1 mutation may promote the progression of CNL-PCD. We also found JAK2, RUNX1, NRAS, etc. in CNL-PCD. CONCLUSIONS: Chronic neutrophilic leukemia may be more inclined to coexist with plasma cell disorder. The CSF3R mutation in CNL-PCD is still the most common mutated gene compared with isolated CNL. Mutations in SETBP1 and ASXL1 may be poor prognostic factors for CNL-PCD.

Chronic neutrophilic leukemia: 2022 update on diagnosis, genomic landscape, prognosis, and management.

DISEASE OVERVIEW: Chronic neutrophilic leukemia (CNL) is a rare, often aggressive myeloproliferative neoplasm (MPN) defined by persistent mature neutrophilic leukocytosis, bone marrow granulocyte hyperplasia, and frequent hepatosplenomegaly. The 2013 seminal discovery of oncogenic driver mutations in colony-stimulating factor 3 receptor (CSF3R) in the majority of patients with CNL not only established its molecular pathogenesis but provided a diagnostic biomarker and rationale for pharmacological targeting. DIAGNOSIS: In 2016, the World Health Organization (WHO) recognized activating CSF3R mutations as a central diagnostic feature of CNL. Other criteria include leukocytosis of ≥25 × 109 /L comprising >80% neutrophils with <10% circulating precursors and rare blasts, and absence of dysplasia or monocytosis, while not fulfilling criteria for other MPN. MANAGEMENT: There is currently no standard of care for management of CNL, due in large part to the rarity of disease and dearth of formal clinical trials. Most commonly used therapeutic agents include conventional oral chemotherapy (e.g., hydroxyurea), interferon, and Janus kinase (JAK) inhibitors, while hematopoietic stem cell transplant remains the only potentially curative modality. DISEASE UPDATES: Increasingly comprehensive genetic profiling in CNL, including new data on clonal evolution, has disclosed a complex genomic landscape with additional mutations and combinations thereof driving disease progression and drug resistance. Although accurate prognostic stratification and therapeutic decision-making remain challenging in CNL, emerging data on molecular biomarkers and the addition of newer agents, such as JAK inhibitors, to the therapeutic arsenal, are paving the way toward greater standardization and improvement of patient care.

Leukemia Cell Lines: In Vitro Models for the Study of Chronic Neutrophilic Leukemia.

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm that is genetically characterized by the absence of both the Philadelphia chromosome and BCR-ABL1 fusion gene and the high prevalence of mutations in the colony-stimulating factor 3 receptor (CSF3R). Additional disease-modifying mutations have been recognized in CNL samples, portraying a distinct mutational landscape. Despite the growing knowledge base on genomic aberrations, further progress could be gained from the availability of representative models of CNL. To address this gap, we screened a large panel of available leukemia cell lines, followed by a detailed mutational investigation with focus on the CNL-associated candidate driver genes. The sister cell lines CNLBC-1 and MOLM-20 were derived from a patient with CNL and carry CNL-typical molecular hallmarks, namely mutations in several genes, such as CSF3R, ASXL1, EZH2, NRAS, and SETBP1. The use of these validated and comprehensively characterized models will benefit the understanding of the pathobiology of CNL and help inform therapeutic strategies.

Current Management of Chronic Neutrophilic Leukemia.

OPINION STATEMENT: Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm (MPN) characterized by oncogenic driver mutations in colony-stimulating factor 3 receptor (CSF3R). Due in large part to the rarity of the disease and dearth of clinical trials, there is currently no standard of care for CNL. Available therapies range from conventional oral chemotherapy to targeted JAK inhibitors to hematopoietic stem cell transplant (HSCT), the latter representing the only potentially curative modality. For this reason, coupled with CNL's typically aggressive clinical course, allogeneic HSCT remains the primary recommended therapy for eligible patients. For ineligible patients, a number of nontransplant therapies have been evaluated in limited trials. These agents may additionally be considered "bridging" therapies pre-transplant in order to control myeloproliferation and alleviate symptoms. Historically, the most commonly utilized first-line agent has been hydroxyurea, though most patients ultimately require second (or subsequent)-line therapy; still hydroxyurea remains the conventional frontline option. Dasatinib has demonstrated efficacy in vitro in cases of CSF3R terminal membrane truncation mutations and may cautiously be considered upfront in such instances, though no substantive studies have validated its efficacy in vivo. Numerous other chemotherapy agents, practically re-appropriated from the pharmaceutical arsenal of MPN, have been utilized in CNL and are typically reserved for second/subsequent-line settings; these include interferon-alpha (IFN-a), hypomethylating agents, thalidomide, cladribine, and imatinib, among others. Most recently, ruxolitinib, a JAK1/2 inhibitor targeting JAK-STAT signaling downstream from CSF3R, has emerged as a potentially promising new candidate for the treatment of CNL. Increasingly robust data support the clinical efficacy, with associated variable reductions in allele burden, and tolerability of ruxolitinib in patients with CNL, particularly those carrying the CSF3RT618I mutation. Similar to conventional nontransplant strategies, however, no disease-modifying or survival benefits have been demonstrated. While responses to JAK-STAT inhibition in CNL have not been uniform, data are sufficient to recommend consideration of ruxolitinib in the therapeutic repertory of CNL. There remains a major unmet need for prospective trials with investigational therapies in CNL.