[A first-in-human clinical trial of piggyBac transposon-mediated GMR CAR-T cells against CD116-positive acute myeloid leukemia and juvenile myelomonocytic leukemia]

Although several types of chimeric antigen receptor (CAR)-modified T cells (CAR-T cells) targeting myeloid antigens have been developed for acute myeloid leukemia (AML) globally, significant clinical benefits have not yet been reported. Furthermore, CAR-T cells targeting juvenile myelomonocytic leukemia (JMML) have not yet been developed. All JMML cells and 63-83% of AML cells express granulocyte macrophage-colony stimulating factor (GM-CSF) receptor (GMR, CD116/CD131 complex). Therefore, we created ligand-based CAR-T cells targeting GMR using the piggyBac transposon system. We further redesigned the CAR construct by optimizing the affinity of the antigen-binding region and length of the spacer region. The GMR CAR-T cells with a mutated GM-CSF at residue 21 (E21K) and a G4S spacer showed superior antitumor effects in the human AML-xenograft model. Safety tests revealed that the toxicity of GMR CAR-T cells was restricted to normal monocytes. Based on the promising results of the nonclinical study, we started a first-in-human clinical trial of GMR CAR-T cells in patients with CD116-positive AML and JMML in 2021.

Malaria Pigment Hemozoin Impairs GM-CSF Receptor Expression and Function by 4-Hydroxynonenal

Malarial pigment hemozoin (HZ) generates the lipoperoxidation product 4-hydroxynonenal (4-HNE), which is known to cause dysregulation of the immune response in malaria. The inhibition of granulocyte macrophage colony-stimulating factor (GM-CSF)-dependent differentiation of dendritic cells (DC) by HZ and 4-HNE was previously described in vitro, and the GM-CSF receptor (GM-CSF R) was hypothesised to be a primary target of 4-HNE in monocytes. In this study, we show the functional impact of HZ on GM-CSF R in monocytes and monocyte-derived DC by (i) impairing GM-CSF binding by 50 ± 9% and 65 ± 14%, respectively (n = 3 for both cell types); (ii) decreasing the expression of GM-CSF R functional subunit (CD116) on monocyte’s surface by 36 ± 11% (n = 6) and in cell lysate by 58 ± 16% (n = 3); and (iii) binding of 4-HNE to distinct amino acid residues on CD116. The data suggest that defective DC differentiation in malaria is caused by GM-CSF R dysregulation and GM-CSF R modification by lipoperoxidation product 4-HNE via direct interaction with its CD116 subunit.

Mutated GM-CSF-based CAR-T cells targeting CD116/CD131 complexes exhibit enhanced anti-tumor effects against acute myeloid leukaemia

Objectives

As the prognosis of relapsed/refractory (R/R) acute myeloid leukaemia (AML) remains poor, novel treatment strategies are urgently needed. Clinical trials have shown that chimeric antigen receptor (CAR)‐T cells for AML are more challenging than those targeting CD19 in B‐cell malignancies. We recently developed piggyBac‐modified ligand‐based CAR‐T cells that target CD116/CD131 complexes, also known as the GM‐CSF receptor (GMR), for the treatment of juvenile myelomonocytic leukaemia. This study therefore aimed to develop a novel therapeutic method for R/R AML using GMR CAR‐T cells.

Methods

To further improve the efficacy of the original GMR CAR‐T cells, we have developed novel GMR CAR vectors incorporating a mutated GM‐CSF for the antigen‐binding domain and G4S spacer. All GMR CAR‐T cells were generated using a piggyBac‐based gene transfer system. The anti‐tumor effect of GMR CAR‐T cells was tested in mouse AML xenograft models.

Results

Nearly 80% of the AML cells predominant in myelomonocytic leukaemia were found to express CD116. GMR CAR‐T cells exhibited potent cytotoxic activities against CD116⁺ AML cells in vitro. Furthermore, GMR CAR‐T cells incorporating a G4S spacer significantly improved long‐term in vitro and in vivo anti‐tumor effects. By employing a mutated GM‐CSF at residue 21 (E21K), the anti‐tumor effects of GMR CAR‐T cells were also improved especially in long‐term in vitro settings. Although GMR CAR‐T cells exerted cytotoxic effects on normal monocytes, their lethality on normal neutrophils, T cells, B cells and NK cells was minimal.

Conclusions

GMR CAR‐T cell therapy represents a promising strategy for CD116⁺ R/R AML.

The Effects of Hypoxia on U937 Cell Line in Mesenchymal Stem Cells Co-Culture System

Purpose: Mesenchymal Stem Cells (MSCs) are the most important members of Bone Marrow (BM) milieu. MSCs affect different kinds of cells, particularly malignant cells of hematologic malignancies, but the effects of MSCs are unclear exactly. Here we analyzed the effects of derived Umbilical Cord Blood-MSCs on proliferation, cell death and some surface markers of U937 cell line in a Co-culture system with MSCs. Methods: Here we designed Co-culture systems as a model of BM milieu. We cultured U937 cells on UCB-MSCs and MSCs Conditioned Medium (C.M) driven and then treated U937 cells with optimum concentration of chloride cobalt (CoCl₂) as a hypoxia-mimetic agent. In addition, we applied suitable concentrations of H₂O₂ to induce cell death. Proliferation rate, cell death rate and some surface markers of hypoxic U937 cells were analyzed by MTT assay, flow cytometry and Real Time-PCR were flown respectively. Results: UCB-MSCs showed supportive effects on U937 proliferation rate in normoxia and hypoxia. Lethal effect of H₂O₂ suppressed in the presence of UCB-MSCs in hypoxia and normoxia. Among CD11a, CD14, CD49d, CD54 and CD116 markers, CD49d was down regulated in presence of UCB-MSCs and CD116 was up regulated in hypoxia. Other markers didn't show any significant changes. Conclusion: This work provides evidences that MSCs play critical roles in U937 cells biology. These observations shed new light on MSCs roles and demonstrated that MSCs should be regarded as an important member of BM milieu in several clinical applications such as BM transplantation prognosis and treatment of hematologic malignancies.

Differential antigen expression and aberrant signaling via PI3/AKT, MAP/ERK, JAK/STAT, and Wnt/β catenin pathways in Lin-/CD38-/CD34+ cells in acute myeloid leukemia

Acute myeloid leukemia is often called as stem cell disease that presents with treatment failure and poor disease outcome. Leukemic stem cells in acute myeloid leukemia (AML) are enriched in Lineage-/CD38-/CD34+ compartment of CD34-positive AML. Many markers important for stem cell biology have been reported for their association with leukemic stem cell population, but what remains clinically most important is a rapid identification of prognostic information. In this study, we evaluated four signal transduction pathways and thirteen markers on Lin-/CD38-/CD34+ population in AML. Expressions were compared in different AML subtypes, survival, and treatment outcome groups. We observed that markers important in homing, cell quiescence, and signal propagation such as CD44, CD96, CD90, WT-1, CD123 and CD25 were most significantly differentially expressed on Lin-/CD38-/CD34+ population in AML from their normal counterparts (P < 0.05, Mann-Whitney). Constitutive activation of phospho ERK, AKT, and STAT5 in these cells was associated with poor outcome. Also, an increased frequency of putative leukemic stem cell population shows negative impact on treatment outcome and overall survival, suggesting that initial evaluation of AML samples for pLSC frequency and constitutively activated signaling pathway can provide prognostic and therapeutic information at the time of diagnosis.