Flow cytometric immunophenotypic features of acute myeloid leukemia with mast cell differentiation.

Acute myeloid leukemia (AML) with mast cell (MC) differentiation was recently described as an aggressive subgroup of AML cases. The objectives of this study were to assess the flow cytometric immunophenotypic features of AML-MC cases. We characterized the immunophenotypic features of 21 AML-MC cases by flow cytometry and compared them to 20 reactive/regenerating bone marrow specimens. The number of MCs detected by flow cytometry in AML-MC cases ranged from 0.4% to 21.1%, with a median of 3.5%, significantly higher than that of normal/reactive bone marrow (BM) (median, 0.01%; range, 0.000%-0.396%; P < .0001). Immunophenotypically, MCs in AML-MC cases demonstrated immaturity, differing from MCs in normal/reactive BMs, including dimmer CD45 (100% vs 0%), lower side scatter (100% vs 0%), more frequent CD34 (81% vs 20%), and CD123 (100% vs 10%) positivity, and more frequent uniform/increased CD38 expression (95% vs 20%) (all P ≤ .0001). CD2 (0/5) and CD25 (2/6, 1 uniform and 1 partial) were assessed in a subset of cases. The myeloblasts in AML-MC were typically CD34+CD117+HLA-DR+ with unusually frequent expression of CD56 (57%, all partial) and CD25 (63%, mostly partial), increased CD117 (62%), and decreased CD38 (86%). The MC percentage determined by flow cytometry correlated well with MCs detected by tryptase immunohistochemistry (r = 0.76, P < .001). The MCs in AML-MC cases are characterized by dim CD45, low side scatter, CD34 and CD123 positivity, and uniform and increased CD38 expression. Flow cytometry is an excellent tool for identifying AML-MC cases.

Xu J ，Kim DH ，Wang W ，Li S ，Lin P ，Tang G ，Konoplev S ，Qiu L ，Fang H ，Garces S ，Leventaki V ，E S ，Medeiros LJ ，Wang SA ... -  《-》

Clinical, immunophenotypic, and genomic findings of acute myeloid leukemia with RAM immunophenotype: Comparison with other CD56-positive acute leukemias.

Acute myeloid leukemia (AML) with RAM immunophenotype is a newly recognized high-risk AML immunophenotypic subcategory characterized by blasts with bright expression of CD56 and weak to absent expression of CD45, HLA-DR, and CD38, as first described by the Children's Oncology Group (COG). The relationship between AML-RAM and other CD56-positive acute leukemias is unclear. The goal of this study is to characterize the clinicopathological characteristics of AML with RAM phenotype and compare them with other CD56 co-expressing acute leukemias. From a multi-institutional search, we identified a total of 160 CD56+ acute leukemia cases, including AML-RAM (n = 28), CD56+ acute undifferentiated leukemia (AUL) (n = 11), CD56+ T-lymphoblastic leukemia (n = 39), and CD56+ AML (n = 81). We compared the clinical and pathologic findings of these groups. AML-RAM patients were significantly younger and presented with significantly higher platelet and white blood cell counts and bone marrow (BM) blast percentages when compared to AUL (p > 0.05) and had higher median BM blast percentages than T-ALL and CD56+ AML groups (both p < 0.05). Flow cytometry showed significantly brighter expression of CD56 on blasts as compared to other CD56+ AML cases, partial CD34 expression compared to AUL, and AML, weak-to-absent CD38 expression compared to all groups, and absent HLA-DR and terminal deoxynucleotidyl transferase as compared to AUL and T-ALL (all p < 0.05). The frequency of abnormal karyotypes was significantly higher among RAM when compared to all groups (p < 0.05). Next-generation sequencing profiles differed among the leukemia groups, with significant enrichment of CBFA2T3::GLIS2 fusions (p < 0.05) and TP53 mutations (p < 0.05) in RAM cases compared to other AML control groups, and U2AF1 (p < 0.05), serine and arginine-rich splicing factor 2 (p < 0.05), and BCL6 co-repressor (p < 0.05) mutations compared to AUL. Clinical outcome analysis demonstrated significantly lower 3-year overall survival of the RAM subgroup (36 months) compared to control groups (p = 0.002). We find that AML with RAM phenotype occurs primarily in younger ages, with distinct clinicopathological, immunophenotypic, and mutational presentations, and worse prognosis. This diagnosis should be considered in the clinical differential diagnosis of CD56-positive acute leukemias.

Hamdan H ，Liu YC ，Wang SA ，Bledsoe J ，Chisholm KM ，Siddon A ，Ohgami R ，George TI ，Kurzer J ，Hasserjian RP ，Arber DA ，Bagg A ，Foucar K ，Margolskee E ，Laczko D ，Chen W ，Fuda F ，Aggarwal N ，Weinberg OK ... -  《-》

A distinct subgroup of AML resembling the APL immunophenotype is associated with DIC.

The complexity of acute myeloid leukemia (AML) is increasingly recognized through the identification of distinct subgroups, including those with an APL-like immunophenotype characterized by the absence of CD34 and HLA-DR expression, which is widely recognized as a representative immunophenotype in acute promyelocytic leukemia (APL). This study sought to understand the clinical, molecular, and prognostic differences between AML patients with and without this phenotype. This study retrospectively analysed 191 de novo non-M3 AML patients and identified 32 patients with the CD34-HLA-DR- phenotype resembling APL-like immunophenotype, considered as the experimental group. Clinical data, including complete blood count, leukemic blasts, coagulation analysis DIC score, and OS, were collected, and immunophenotypic and molecular data were compared between this group and a control group of patients without this immunophenotype. Patients with the CD34-HLA-DR- immunophenotype in the AML cohort had a significantly greater risk of developing disseminated intravascular coagulation (DIC) than did patients in the control group. Additionally, a lower rate of expression of immunophenotypic clusters of differentiation (CD markers) associated with poor prognosis was observed in the CD34-HLA-DR- group. At the molecular level, an increased frequency of nucleophosmin 1 (NPM1) mutations and increased expression of the Wilms' tumor 1 (WT1) gene were noted in this subgroup. However, contrary to patients with an expected favourable prognosis, patients in the favourable risk group with the CD34-HLA-DR- immunophenotype had significantly shorter overall survival than did patients in the control group. The findings highlight the patients exhibiting the CD34-HLA-DR- immunophenotype as a unique AML subgroup with specific clinical and molecular traits, notably a predisposition to DIC, which affecting prognosis. This finding has implications for risk stratification and potential targeted therapies for AML management.

Li P ，Liu L ，Zhou F 《BMC CANCER》

Inducible pluripotent stem cells to study human mast cell trajectories.

Mast cells (MCs) are derived from CD34+ hematopoietic progenitors, consist of different subtypes, and are involved in several inflammatory conditions. However, our understanding of human MC developmental trajectories and subtypes has been limited by a scarcity of suitable cellular model systems. Herein, we developed an in vitro model of human MC differentiation from induced pluripotent stem cells (iPSC) to study human MC differentiation trajectories. Flow cytometry characterization of hemopoietic cells derived from the myeloid cells-forming complex (MCFC) revealed an initial increase in Lin- CD34+ hematopoietic progenitors within Weeks 1-3, followed by an increase in CD34- CD45RA- SSClow and SSChigh hematopoietic cells. The Lin- CD34+ hematopoietic progenitors consisted of SSClow CD45RA- CD123± c-Kit+ FcεRI+ populations that were β7-integrinhigh CD203c+ and β7-integrinhigh CD203c- cells consistent with CMPFcεRI+ cells. Flow cytometry and cytologic analyses of the CD34- Lin- (SSClow) population revealed hypogranular cell populations, predominantly characterized by CD45RA- CD123± c-Kit+ FcεRI- β7-integrinlow and CD45RA- CD123± c-Kit- FcεRI+ β7-integrinMid cells. Analyses of hypergranular SSChigh cells identified Lin- CD34- CD45RA- c-Kit+ FcεRI- and Lin- CD34- CD45RA- c-Kit+ FcεRI+ cells. scRNA-seq analysis of the cells harvested at week 4 of the MCFC culture revealed the presence of monocyte and granulocyte progenitors (n = 547 cells, 26.7 %), Erythrocyte / unknown (n = 85, 4.1 %), neutrophils / myelocytes (n = 211 cells, 10.2 %), mast cell progenitor 1 (n = 599, 29.1 %), mast cell progenitor 2 (n = 152, 7.4 %), committed mast cell precursor (n = 113, 5.5 %), and MCs (n = 353, 17.1 %). In silico analyses of the MC precursor and mature MC populations revealed transcriptionally distinct MC precursor subtype and mature MC states (CMA1+ and CMA1- subtypes). Culturing MC precursor populations in MC maturation media (mast cell media II) led to homogenous mature MC populations as evidenced by high expression of high-affinity IgE receptor, metachromatic granules, presence of MC granule proteins (Tryptase and Chymase) and activation following substance P stimulation and FcεRI crosslinking. This human iPSC-based approach generates MC precursors and phenotypically mature and functional MC populations. This system will be a useful model to generate human MC populations and broaden our understanding of MC biology and transcriptional regulation of MC differentiation trajectories.

Idelman G ，Rizza CF ，Marella S ，Sharma A ，Chakraborty S ，Tay HL ，Tomar S ，Ganesan V ，Schuler CF 4th ，Baker JR ，Hogan SP ... -  《-》

CD38, CD39, and BCL2 differentiate disseminated forms of high-grade B-cell lymphomas in biological fluids from Burkitt lymphoma and diffuse large B-cell lymphoma.

Marianini P ，Lacheretz-Szablewski V ，Almeras M ，Moreaux J ，Bret C ... -  《-》