Biphasic expression of CD4 in acute myelocytic leukemia (AML) cells: AML of monocyte origin and hematopoietic precursor cell origin

Construction of Switch Modules for CAR-T Cell Treatment Using a Site-Specific Conjugation System

Chimeric antigen receptor T-cell (CAR-T cell) therapy has become a promising treatment option for B-cell hematological tumors. However, few optional target antigens and disease relapse due to loss of target antigens limit the broad clinical applicability of CAR-T cells. Here, we conjugated an antibody (Ab) fusion protein, consisting of an Ab domain and a SpyCatcher domain, with the FITC-SpyTag (FITC-ST) peptide to form a bispecific safety switch module using a site-specific conjugation system. We applied the safety switch module to target CD19, PDL1, or Her2-expressing tumor cells by constructing FMC63 (anti-CD19), antiPDL1, or ZHER (anti-Her2)-FITC-ST, respectively. Those switch modules significantly improved the cytotoxic effects of anti-FITC CAR-T cells on tumor cells. Additionally, we obtained the purified CD8+ T cells by optimizing a shorter version of the CD8-binding aptamer to generate anti-FITC CD8-CAR-T cells, which combined with the CD4-FITC-ST switch module (anti-CD4) to eliminate the CD4-positive tumor cells in vitro and in vivo. Overall, we established a novel safety switch module by site-specific conjugation to enhance the antitumor function of universal CAR-T cells, thereby expanding the application scope of CAR-T therapy and improving its safety and efficacy.

A Proteomic Approach to Understand the Clinical Significance of Acute Myeloid Leukemia-Derived Extracellular Vesicles Reflecting Essential Characteristics of Leukemia

Extracellular vesicle (EV) proteins from acute myeloid leukemia (AML) cell lines were analyzed using mass spectrometry. The analyses identified 2450 proteins, including 461 differentially expressed proteins (290 upregulated and 171 downregulated). CD53 and CD47 were upregulated and were selected as candidate biomarkers. The association between survival of patients with AML and the expression levels of CD53 and CD47 at diagnosis was analyzed using mRNA expression data from The Cancer Genome Atlas database. Patients with higher expression levels showed significantly inferior survival than those with lower expression levels. ELISA results of the expression levels of CD53 and CD47 from EVs in the bone marrow of patients with AML at diagnosis and at the time of complete remission with induction chemotherapy revealed that patients with downregulated CD53 and CD47 expression appeared to relapse less frequently. Network model analysis of EV proteins revealed several upregulated kinases, including LYN, CSNK2A1, SYK, CSK, and PTK2B. The potential cytotoxicity of several clinically applicable drugs that inhibit these kinases was tested in AML cell lines. The drugs lowered the viability of AML cells. The collective data suggest that AML cell-derived EVs could reflect essential leukemia biology.

Palmitoylated Proteins on AML-Derived Extracellular Vesicles Promote Myeloid-Derived Suppressor Cell Differentiation via TLR2/Akt/mTOR Signaling

Acute myeloid leukemia (AML) represents the most common acute leukemia among adults. Despite recent progress in diagnosis and treatment, long-term outcome remains unsatisfactory. The success of allogeneic stem cell transplantation underscores the immunoresponsive nature of AML, creating the basis for further exploiting immunotherapies. However, emerging evidence suggests that AML, similar to other malignant entities, employs a variety of mechanisms to evade immunosurveillance. In light of this, T-cell inhibitory myeloid-derived suppressor cells (MDSC) are gaining interest as key facilitators of immunoescape. Accumulation of CD14⁺HLA-DR^low monocytic MDSCs has been described in newly diagnosed AML patients, and deciphering the underlying mechanisms could help to improve anti-AML immunity. Here, we report that conventional monocytes readily take-up AML-derived extracellular vesicles (EV) and subsequently undergo MDSC differentiation. They acquired an CD14⁺HLA-DR^low phenotype, expressed the immunomodulatory indoleamine-2,3-dioxygenase, and upregulated expression of genes characteristic for MDSCs, such as S100A8/9 and cEBPβ. The Akt/mTOR pathway played a critical role in the AML-EV-induced phenotypical and functional transition of monocytes. Generated MDSCs displayed a glycolytic switch, which rendered them more susceptible toward glycolytic inhibitors. Furthermore, palmitoylated proteins on the AML-EV surface activated Toll-like receptor 2 as the initiating event of Akt/mTOR-dependent induction of MDSC. Therefore, targeting protein palmitoylation in AML blasts could block MDSC accumulation to improve immune responses. SIGNIFICANCE: These findings indicate that targeting protein palmitoylation in AML could interfere with the leukemogenic potential and block MDSC accumulation to improve immunity.

The prognostic value of CD2, CD4, and HLA-DR expression and FLT3-ITD mutation in adult acute promyelocytic leukemia

In order to explore the prognostic value of CD2, CD4, and human leucocyte antigen-DR (HLA-DR) expression and Fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutation in leukemia cells in the bone marrow of patients with acute promyelocytic leukemia (APL), we retrospectively collected and analyzed the immunophenotype, molecular features and clinical characteristics of 219 newly diagnosed adult patients with APL in Henan Provincial People's Hospital from January 2010 to December 2019. It turned out that the relapse rates of patients with CD2, CD4, or HLA-DR expression and the early mortality rates of patients with CD2 expression, HLA-DR expression, or FLT3-ITD mutation were higher than those of their counterparts. Moreover, reduced overall survival was found for patients who showed CD2 expression, HLA-DR expression or FLT3-ITD mutation. Therefore, CD2 expression, HLA-DR expression and FLT3-ITD mutation were adverse prognostic factors in adults with APL.

Preclinical Targeting of Human Acute Myeloid Leukemia Using CD4-specific Chimeric Antigen Receptor (CAR) T Cells and NK Cells

Acute myeloid leukemia (AML) is an aggressive malignancy lacking targeted therapy due to shared molecular and transcriptional circuits as well as phenotypic markers with normal hematopoietic stem cells (HSCs). Identifying leukemia specific markers expressed on AML or AML subtypes for therapeutic targeting is of exquisite clinical value. Here we show that CD4, a T lymphocytes membrane glycoprotein that interacts with major histocompatibility complex class II antigens and is also expressed in certain AML subsets but not on HSCs is a proper target for genetically engineered chimeric antigen receptor T cells (CAR-T cells). Treatment with CD4 redirected CAR-T cell (CD4CAR) specifically eliminated CD4-expressing AML cell lines in vitro and exhibited a potent anti-leukemic effect in a systemic AML murine model in vivo. We also utilized natural killers as another vehicle for CAR engineered cells and this strategy similarly and robustly eliminated CD4- expressing AML cells in vitro and had a potent in vivo anti-leukemic effect and was noted to have shorter in vivo persistence. Our data offer a proof of concept for immunotherapeutic targeting of CD4 as a strategy to treat CD4 expressing refractory AML as a bridge to stem cell transplant (SCT) in a first in human clinical trial.

Chimeric Antigen Receptors for T-Cell Malignancies

Development of chimeric antigen receptor (CAR)-modified T cells for the treatment of T-lineage leukemia and lymphoma has encountered several unique challenges. The most widely expressed tumor antigen targets for malignant T cells are often also expressed on non-malignant T cells. Transducing T cells with CARs targeted to these shared antigens can therefore promote over-activation or fratricide of CAR T cells, reducing their therapeutic potency. If fratricide is resolved, clinical CAR T cell activity may eliminate normal T-cell subsets and cause temporary immunosuppression. In this review, we summarize the preclinical development of CAR-based therapies for T-cell malignancies and discuss strategies to minimize toxicities associated with on-target fratricide and off-tumor activity.

Morphologic and immunophenotypic features of a case of acute monoblastic leukemia with unusual positivity for Glycophorin-A

Acute monoblastic leukemia (AMoL) is characterized by cells with highly undifferentiated morphology. Cytochemistry with non-specific esterases is negative in up to 20% of cases. Immunophenotyping by flow cytometry has an essential role in diagnosing such a subtype of leukemia and a multiparametric approach with a wide monoclonal antibody panel is necessary. We describe a case of AMoL with morphology resembling either plasma blasts or very immature erythroblasts. Diagnosis was made by alpha-naphtyl-acetate esterase staining and with immunophenotyping, which was made with a wide monoclonal antibody panel. Blasts were positive for monocytic markers. Most of leukemic cells, however, were positive for Glycophorin-A. The presence of Glycophorin-A, which is considered as a specific marker of the erythroid lineage, has never been reported previously in cases of AMoL. This peculiar immunophenotype might be interpreted as deriving from a common myelo-erythroid precursor undergone leukemic transformation.

The putative anti-leukemic effects of anti-thymocyte globulins in patients with CD7-positive acute myeloid leukemia

Polyclonal anti-thymocyte globulins (ATGs) are widely used in allogeneic stem cell transplantation (allo-SCT) for GvHD prophylaxis. ATGs exerted anti-tumor effects in in vitro experiments, but in vivo studies are lacking. We experienced a case of relapsed AML with cells positive for CD7 who underwent haploidentical SCT and unexpectedly achieved a significant reduction of AML cells in the peripheral blood after receiving ATGs before the administration of other drugs in the conditioning regimen. This patient achieved long-term survival after haploidentical SCT. To assess the impact of ATGs on clinical outcomes in patients with AML, we performed a retrospective analysis of allo-SCT for relapsed/refractory AML and divided 132 patients into four groups according to the expression of CD7 in AML cells and use of ATGs as part of the conditioning regimen, as follows: CD7-positive ATG group (n = 15), CD7-positive no-ATG group (n = 32), CD7-negative ATG group (n = 19), and CD7-negative no-ATG group (n = 66). The overall survival rates in the CD7-positive ATG group were significantly higher than those in the CD7-positive no-ATG group, whereas these rates did not differ statistically between the CD7-negative ATG and CD7-negative no-ATG groups. Our results indicate a possible anti-leukemic effect of ATGs against CD7-positive AML in humans.

Targeting T-cell malignancies using anti-CD4 CAR NK-92 cells

Peripheral T-cell lymphomas (PTCLs) are a group of very aggressive non-Hodgkin's lymphomas (NHLs) with poor prognoses and account for a majority of T-cell malignancies. Overall, the standard of care for patients with T-cell malignancies is poorly established, and there is an urgent clinical need for a new approach. As demonstrated in B-cell malignancies, chimeric antigen receptor (CAR) immunotherapy provides great hope as a curative treatment regimen. Because PTCLs develop from mature T-cells, these NHLs are commonly CD4+, and CD4 is highly and uniformly expressed. Therefore, CD4 is an ideal target for PTCL CAR immunotherapy. To that effect, we created a robust third-generation anti-CD4 CAR construct (CD4CAR) and introduced it into clonal NK cells (NK-92). CD4CAR NK-92 cells specifically and robustly eliminated diverse CD4+ human T-cell leukemia and lymphoma cell lines (KARPAS-299, CCRF-CEM, and HL60) and patient samples ex vivo. Furthermore, CD4CAR NK-92 cells effectively targeted KARPAS-299 cells in vivo that modeled difficult-to-access lymphoma nodules, significantly prolonging survival. In our study, we present novel targeting of CD4 using CAR-modified NK cells, and demonstrate efficacy. Combined, our data support CD4CAR NK cell immunotherapy as a potential new avenue for the treatment of PTCLs and CD4+ T-cell malignancies.

Prognostic Relevance of Cytokine Receptor Expression in Acute Myeloid Leukemia: Interleukin-2 Receptor α-Chain (CD25) Expression Predicts a Poor Prognosis

A variety of cytokine/cytokine receptor systems affect the biological behavior of acute leukemia cells. However, little is known about the clinical relevance of cytokine receptor expression in acute myeloid leukemia (AML). We quantitatively examined the expression of interleukin-2 receptor α-chain (IL-2Rα, also known as CD25), IL-2Rβ, IL-3Rα, IL-4Rα, IL-5Rα, IL-6Rα, IL-7Rα, the common β-chain (βc), γc, granulocyte-macrophage colony-stimulating factor (GM-CSF)Rα, G-CSFR, c-fms, c-mpl, c-kit, FLT3, and GP130 in leukemia cells from 767 adult patients with AML by flow cytometry and determined their prevalence and clinical significance. All cytokine receptors examined were expressed at varying levels, whereas the levels of IL-3Rα, GM-CSFRα, IL-2Rα, γc, c-kit, and G-CSFR exhibited a wide spectrum of ≥10,000 sites/cell. In terms of their French-American-British classification types, GM-CSFRα and c-fms were preferentially expressed in M4/M5 patients, G-CSF in M3 patients, and IL-2Rα in non-M3 patients. Elevated levels of IL-3Rα, GM-CSFRα, and IL-2Rα correlated with leukocytosis. In patients ≤60 years old, higher levels of these 3 receptors correlated with poor responses to conventional chemotherapy, but only IL-2Rα was associated with a shorter overall survival. By incorporating IL-2Rα status into cytogenetic risk stratification, we could sort out a significantly adverse-risk cohort from the cytogenetically intermediate-risk group. Analyses with various phenotypical risk markers revealed the expression of IL-2Rα as an independent prognostic indicator in patients with intermediate-risk cytogenetics. These findings were not observed in patients >60 years old. Our results indicate that several cytokine receptors were associated with certain cellular and clinical features, but IL-2Rα alone had prognostic value that provides an additional marker to improve current risk evaluation in AML patients ≤60 years old.

Rapid detection of dendritic cell and monocyte disorders using CD4 as a lineage marker of the human peripheral blood antigen-presenting cell compartment

Dendritic cells (DCs) and monocytes are critical regulators and effectors of innate and adaptive immune responses. Monocyte expansion has been described in many pathological states while monocyte and DC deficiency syndromes are relatively recent additions to the catalog of human primary immunodeficiency disorders. Clinically applicable screening tests to diagnose and monitor these conditions are lacking. Conventional strategies for identifying human DCs and monocytes have been based on the use of a lineage gate to exclude lymphocytes, thus preventing simultaneous detection of DCs, monocytes, and lymphocyte subsets. Here we demonstrate that CD4 is a reliable lineage marker for the human peripheral blood antigen-presenting cell compartment that can be used to identify DCs and monocytes in parallel with lymphocytes. Based on this principle, simple modification of a standard lymphocyte phenotyping assay permits simultaneous enumeration of four lymphocyte and five DC/monocyte populations from a single sample. This approach is applicable to clinical samples and facilitates the diagnosis of DC and monocyte disorders in a wide range of clinical settings, including genetic deficiency, neoplasia, and inflammation.

Distinctive expression of myelomonocytic markers and down-regulation of CD34 in acute myelogenous leukaemia with FLT3 tandem duplication and nucleophosmin mutation

OBJECTIVE

Patients with acute myelogenous leukaemia (AML) show co-existing frequently internal tandem duplications of FLT3 (FLT3-ITD) and mutations of nucleophosmin (NPM1-Mt). We investigated the biological and clinical significance of FLT3-ITD and/or NPM1-Mt in this context.

METHODS

We analysed 89 AML patients according to whether NPM1 and FLT3-ITD were single mutants, double mutants, or wild type for both.

RESULTS

FLT3-ITD was detected in 19 of 89 patients (21.3%), while NPM1-Mt was detected in 19 of 89 patients (21.3%); eight of 89 patients (9.0%) carried both FLT3-ITD and NPM1-Mt. By multivariate analysis, white blood cell count and peripheral blood blast cell count at diagnosis were significantly higher in patients with FLT3-ITD but not in those with only NPM1-Mt. NPM1-Mt was significantly related to female gender, normal karyotype, and M4 or M5 disease according to French-American-British criteria. In addition, leukaemic blast cells with NPM1-Mt, FLT3-ITD, or both expressed CD34 less frequently than wild-type blasts (P < 0.0001 and P = 0.005 respectively), while myelomonocytic markers such as CD11b and CD14 were expressed more frequently in patients with NPM1-Mt.

CONCLUSION

FLT3-ITD may increase potential for cell proliferation to produce a leukaemic population; NPM1-Mt may cause cells to develop along the myelomonocytic lineage. Extensive analyses and detailed experiments will be required to clarify how NPM1 and FLT3 mutations interact in leukaemogenesis.

B cells CD19+ in patients with B-cell chronic lymphocytic leukaemia and autoimmune haemolytic anaemia

The study presents results of B and T lymphocytes population analysis in patients with chronic lymphocytic leukaemia B cells and autoimmune haemolytic anaemia (CLL-B + AIHA). We evaluated the following groups of patients: (1) with newly recognized CLL-B and co-existent AIHA (untreated), (2) after short-term treatment with corticosteroids, (3) after treatment with chemotherapy and corticosteroids. The control groups were made of patients with CLL-B without AIHA. The populations of lymphocytes and determination of cells immunophenotype were performed by means of flow cytometry. The analysed data were obtained from 25 patients. The untreated patients with CLL-B + AIHA presented significantly more numerous population of neoplastic cells CD19+ CD5+ in comparison with patients without AIHA. The patients with AIHA showed a reduced percentage of B CD19+ CD22+ cells in comparison with those without AIHA. Untreated patients with AIHA or after a short-term corticosteroid treatment showed a higher ratio of the number of CD19+ CD5+ cells to the number of T CD4+ and T CD8+ lymphocytes than CLL-B patients without AIHA. It can be presumed that the differences found may be related to the pathogenesis of the autoimmune haemolysis syndrome in patients with CLL-B.

c-Kit receptor (CD117) expression on myeloblasts and white blood cell counts in acute myeloid leukemia

BACKGROUND

The c-Kit receptor is considered to play a crucial role in hematopoiesis. Induction of mobilization of hematopoietic cells in the bone marrow requires cooperative signaling through c-Kit and c-Kit ligand pathway, and these interactions are important in the retention of stem cells within the bone marrow. Therefore, we analyzed c-Kit density on the leukemic myeloblasts of patients with acute myeloid leukemia (AML) in relation to white blood cell count (WBC) in the peripheral blood.

METHODS

Bone marrow aspirates collected from patients with AML and bone marrow aspirates and leukapheresis products after granulocyte colony-stimulating factor blood mobilization from adult volunteers were studied. To determine the level of c-Kit receptor expression, we applied quantitative (relative fluorescence intensity and antibody binding per cell) cytometric methods.

RESULTS

Our data showed negative correlation between the level of c-Kit expression intensity on myeloblasts and the number of leukocytes in blood of AML patients. The c-Kit receptor density on myeloblasts in patients with low WBC was significantly stronger than that on myeloblasts in patients with high WBC. In the latter patient group, the density c-Kit receptor on myeloblasts was similar to that on CD34(+) cells in mobilized peripheral blood.

CONCLUSIONS

The obtained data suggest an involvement of c-Kit receptor in the regulation of leukemic myeloblasts egress to the peripheral blood.

Expression of CD4 on peripheral blood granulocytes. a novel finding in a case of myelodysplastic syndrome in association with t(5;12)

Myelodysplastic syndromes (MDS) are associated with cell maturation defects that can manifest as abnormal surface antigen expression. We describe a patient with refractory anemia with excess blasts, who presented with infection and extensive dysplastic features in peripheral blood granulocytes. The granulocytes expressed CD11b, CD13, CD15, CD33, and CD43. The granulocytes also expressed CD4 antigen. Cytogenetic analysis showed a clonal t(5;12)(q33;p13). The patient improved on antibiotics with partial improvement in the dysplastic features. However, shortly after, the patient experienced paravertebral extramedullary blast transformation followed by a leukemia phase of acute monoblastic leukemia. The patient died a few days later. This is the first report describing anomalous expression of CD4 on granulocytes in MDS. Since the breakpoint on chromosome 12 is near the CD4 gene, which is mapped to 12p12, we hypothesize that dysregulation of the CD4 gene may have occurred resulting in its persistent expression on mature and maturing granulocytes.