Editorial Note: Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) and Chimeric Antigen Receptor T-cell (CAR-T) therapy have become crucial in the treatment of leukemia. However, the effectiveness and safety of these treatments continue to be hot topics of research. Recent breakthrough studies have provided valuable insights, particularly in the treatment of children with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL), prevention and monitoring of graft-versus-host disease (GVHD), and management of complications following CAR-T therapy. The 50th European Society for Blood and Marrow Transplantation (EBMT) annual meeting, held from April 14 to 17, 2024, in Glasgow, UK, focused on the latest advancements in stem cell transplantation and cellular therapy, pushing forward better clinical outcomes for hematologic patients. At this conference, Professor Shaoyan Hu and her team from the Affiliated Children’s Hospital of Soochow University reported on six studies. Oncology Frontier – Hematology Frontier specially invited Professor Shaoyan Hu and her team members to share their research findings on the efficacy and safety of allo-HSCT and CAR-T cell therapy in pediatric leukemia patients in a roundtable discussion format and to provide insightful commentary on these six studies.
Background Graft-versus-host disease (GVHD) is a major complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and a leading cause of mortality in recipients. While direct damage to target organs in GVHD is primarily mediated by T cells, dendritic cells (DCs) effectively initiate T cell activation. DCs play a crucial role in the induction, regulation, and maintenance of GVHD. Previous studies suggest that Type 3 dendritic cells (DC3), a distinct subset, can significantly promote inflammation and are abnormally accumulated in autoimmune diseases such as systemic lupus erythematosus (SLE). However, research is limited, and the association between DC3 and GVHD has not been extensively explored.
Methods A total of 63 pediatric patients who underwent allo-HSCT at the Affiliated Children’s Hospital of Soochow University were included in this study. We collected peripheral blood samples from the children post-allo-HSCT and analyzed DC subgroups using flow cytometry. We compared the proportion and count of DC subgroups in children with no or mild GVHD (Grade 0-I) versus those with severe GVHD (Grade II-IV).
Results In the study, patients with Grade II-IV GVHD occurring within 28 days post-allo-HSCT had lower frequencies and counts of plasmacytoid dendritic cells (pDCs) compared to those with Grade 0-I GVHD. Notably, patients with Grade II-IV acute GVHD (aGVHD) demonstrated significantly different frequencies of CD1c+DCs compared to those with Grade 0-I GVHD, although there were no significant differences in counts between the groups. Significantly higher frequencies of DC3 within CD1c+DCs were observed in patients with Grade II-IV GVHD compared to those with Grade 0-I (26.8% vs. 13.3%; P=0.0003), indicating an association between high frequencies of DC3 in CD1c+DCs and the occurrence of severe GVHD.
Using Receiver Operating Characteristic (ROC) curve analysis, we explored the threshold of DC3 as a discriminator between patients with Grade II-IV GVHD and those with Grade 0-I. The median level of DC3 in CD1c+DCs at 28 days post-allo-HSCT was 18.5%. We set a threshold of 24.50% in CD1c+DCs to evaluate the differences between patients with high versus low levels of DC3. Patients with DC3 levels above 24.50% had a significantly increased risk of developing Grade II-IV GVHD (P<0.0001).
Conclusion The study findings indicate a significant correlation between high frequencies of DC3 in CD1c+DCs on Day 28 post-allo-HSCT and severe GVHD. A high frequency of DC3 in CD1c+DCs appears to be associated with more severe GVHD. Thus, regular monitoring of DCs, particularly DC3, post-transplantation is crucial for predicting GVHD.
EBMT Presentation | OS17-08: Impaired Initial CD8+T Cells (CD45RO-CCR7+) in AML Associated with Lower Overall Survival Rates Speaker: Zhang Yongping
Background In the bone marrow microenvironment of Acute Myeloid Leukemia (AML), a complex interplay of various immune cells and regulatory factors leads to T cell dysfunction. Initial CD8+ T cells, upon activation by antigen-presenting cells (APCs) such as dendritic cells (DCs), differentiate into effector and memory cells. However, a significant portion of remaining CD8+ T cells display diminished effector functions due to exhaustion or senescence. While much research has focused on the mechanisms and interventions for exhausted or senescent cells, the role of initial CD8+ T cells in AML remains poorly understood. This study aims to determine the functional status of initial CD8+ T cells in AML and their correlation with patient survival outcomes.
Methods We collected fresh bone marrow samples from children under 14 diagnosed with AML. Flow cytometry, transcriptomic sequencing, and in vitro culture models were used to identify the numbers, activation, and differentiation of CD45RO-CCR7+ initial CD8+ T cells (CD8+ Tnaïve). Single-cell RNA sequencing revealed key genes and transcription factors, while CRISPR-Cas9 was used to edit genes in initial CD8+ T cells to study their impact on cell exhaustion. Correlation analysis with chemotherapy assessments and survival data elucidated the role of initial CD8+ T cells in AML treatment and prognosis.
Results Compared to 21 age-matched healthy donors (HDs) eligible for HSCT, the proportion of CD45RO-CCR7+CD8+Tnaïve cells in the bone marrow of 56 children with AML was significantly lower (mean: HDs, 60%; AML, 45%; P<0.05). CD45RO-CCR7+CD8+Tnaïve cells in AML exhibited significantly higher expression of inhibitory molecules VISTA and CTLA-4 (HDs, <5%; AML, 10% to 20%; P<0.05). After sorting and in vitro culturing, the fraction of non-activated CD69-CD25- in CD45RO-CCR7+CD8+Tnaïve cells from AML was significantly higher than HDs (HDs, 20%; AML, 60%; P<0.05). RNA-seq and GSEA revealed significantly activated bile acid metabolism pathways and downregulated MTORC1 signaling in CD45RO-CCR7+CD8+Tnaïve cells in AML. Single-cell RNA-seq showed higher expression of FCER1G and ID2 in CD8+Tnaïve cells with high CCR7, SELL, LTB, and TCF1 in AML. Overexpressing FCER1G in CD45RO-CCR7+CD8+Tnaïve cells via CRISPR-Cas9 led to a significant reduction in memory T cells, increased expression of effector T cells, and upregulated PD-1 and GZMB. Paired analysis of CD45RO-CCR7+CD8+Tnaïve cell proportions before and after the first induction chemotherapy in 15 children with AML showed an increasing trend in 11 complete remission (CR) patients, and a decreasing trend in 4 non-CR patients. Using the average proportion of CD45RO-CCR7+CD8+Tnaïve cells in HDs (60%) as a threshold, 47 AML patients were divided into high-expression and low-expression groups (high-expression: 10; low-expression: 37). The 2-year overall survival rate was significantly lower in the high-expression group (approximately 70%) compared to the low-expression group (95%) (P=0.026, log-rank test).
Conclusion In pediatric AML patients, impaired activation and memory formation of CD45RO-CCR7+ initial CD8+ T cells are associated with a risk factor for 2-year overall survival rates.
Expert Commentary
Bohan Li: Representing our research group, I presented our findings on the special CD8+Tnaïve cells in AML patients. We discovered a significant reduction in these cells compared to healthy individuals. Our further analysis revealed two subgroups in pure AML patients, with one subgroup showing more significant reductions and poorer prognosis, providing predictive value for the prognosis of AML patients and a new approach to tumor immunotherapy for AML. Additionally, we have two more presentations related to hematopoietic stem cell transplantation, including a comparative analysis of chemotherapy and CAR-T therapy post-transplant in a multicenter collaboration, exploring prognostic factors influencing outcomes for children undergoing transplantation in the CCCG cooperative group. Another presentation investigates the risk factors for GVHD post-transplant, highlighting the predictive value of a special subgroup of dendritic cells, CD1c+DCs containing DC3, particularly 30 days post-transplant.
