ALBERT

Beschreibung: Introduction: Acute leukemia is the most common malignancy in children and develops within the bone marrow. Consequently, bone marrow derived T cells of leukemia patients can be defined as tumor infiltrating lymphocytes (TILs). Dysfunctional TILs have been described in several other malignancies. However, in pediatric patients the interaction between leukemic blasts and TILs remains largely unknown. In order to understand the impact of leukemic blasts on bone marrow T cells we profiled T cells in the bone marrow of pediatric leukemia patients by surface marker and transcriptome wide analysis. Methods: First, artificial changes in marker expression due to cryopreservation and thawing were ruled out (n=5). Then, cryopreserved bone marrow samples from both pediatric patients with acute leukemia (n= 77; BCP-ALL: 18, TCP-ALL: 23, AML: 36) and age-matched healthy bone marrow donors (HD, n=23) were identified in a local biobank. Multicolor flow cytometry was performed to quantify co-inhibitory markers on CD4 and CD8 T cells in primary (n=49) and relapse leukemia samples (n=28). As we could not detect surface CTLA4 expression on T cells, CTLA4 was stained intracellularly. Additionally, RNA-Seq on sorted bone marrow derived CD8 T cells (n=48; TCP-ALL: 12, AML: 20, HD: 16) was performed. Analysis of RNA-Seq data was based on Reads Per Kilobase Million (RPKM) normalization and False Discovery Rate (FDR, Benjamini-Hochberg) statistics. 172 differentially expressed genes were found when comparing bone marrow derived CD8 T cells from healthy donors (n=16) and leukemia patients (n=32) using the following criteria: RPKM〉2 in both groups, fold change〉2 and FDR

Beschreibung: Introduction Pediatric acute lymphoblastic leukemia (ALL) is a cancer entity of minimal mutational load and low immunogenicity. The interaction of ALL cells with bone marrow (BM) T cells has not been investigated as a pathogenic driver or prognostic marker for pediatric ALL. We defined BM T cells of pediatric ALL patients as tumor-infiltrating lymphocytes (TILs) and investigated the prognostic relevance of co-stimulatory and co-inhibitory signals between ALL and BM T cells. Methods BM samples of 100 pediatric ALL patients were analyzed at time of initial diagnosis. T-cell subpopulations and expression of co-stimulatory and co-inhibitory molecules were defined by flow cytometry and correlated with clinical outcome of the patients. To investigate the role of TIM-3 for the interaction between T cells and leukemic cells, CRISPR/Cas9-mediated TIM-3 knockout (KO) was performed in primary T cells by ribonucleoprotein electroporation. T-cell activation and proliferation after contact with leukemic target cells were analyzed in TIM-3 KO cells and compared to wildtype T cells and T cells with retroviral TIM-3 overexpression. Interaction of T cells with leukemic target cells was induced by addition of anti-CD19/-CD3 bispecific T-cell engager (BiTE). Fold change (FC) of T-cell activation and proliferation was analyzed before and after co-culture. BM expression levels of known TIM-3 inducers were identified by RNA next generation sequencing of the bone marrow samples. Results Multivariate analyses identified high TIM-3 expression on CD4+ BM T cells at initial diagnosis as strong predictor for relapse of pediatric acute lymphoblastic leukemia (relapse free survival (RFS) 94.6% vs. 70.3%). The risk to develop ALL relapse was 7.1-fold higher in the group of TIM-3 high expressing patients (n=37) compared to TIM-3 low expressing patients (n=37). Expression levels of known TIM-3 ligands and inducers in the bone marrow of the patients were analyzed by RNA next generation sequencing and compared between patients with high TIM-3 expression (n=12) and low TIM-3 expression (n=15) on BM T cells. Presence of known TIM-3 ligands HMGB1 (High-Mobility-Group-Protein B1) and Galectin-9 was confirmed, but expression levels did not show significant differences. Known TIM-3 inducers IL-2, -7, -15 and -21 were not expressed on RNA level indicating that another mechanism must be responsible for TIM-3 overexpression. In vitro experiments showed that the interaction with leukemic cells induces TIM-3 expression on the surface of T cells (mean TIM-3 expression 51.1% vs. 29.7% on T cells with vs. without addition of leukemic cells, n=3). To investigate the functional relevance of TIM-3 expression in pediatric leukemia, TIM-3 KO and overexpression was performed on primary T cells. TIM-3 KO T cells showed higher activation levels after co-culture with leukemic cell lines plus CD3-/CD19-specific BiTE compared to wildtype (WT) T cells (FC of CD69 surface expression 5.0 vs. 3.2, n=3). FC of anti-leukemic proliferation was impaired in TIM-3 overexpressing T cells compared to WT T cells (FC 1.6 vs. 2.3, n=3) whereas TIM-3 KO T cells showed a higher proliferation FC compared to controls (FC 6.5 vs. 2.4, n=3). Conclusions Our study identifies TIM-3 expression on CD4+ bone marrow T cells at initial diagnosis as a strong predictor for pediatric ALL relapse. TIM-3 expression is induced by interaction of T cells with leukemic cells and results in impaired anti-leukemic T-cell activation and proliferation. TIM-3-mediated T-cell inhibition represents a new mechanism of impaired immune surveillance in pediatric ALL and blockade of this axis may be of importance for future immunotherapy in ALL. Disclosures No relevant conflicts of interest to declare.

Beschreibung: Introduction: Pearson syndrome (PS) was originally reported as a sideroblastic anemia in infancy with vacuolization of marrow precursors and exocrine pancreas dysfunction. It is now recognized as a fatal multisystem mitochondrial disorder caused by single mitochondrial DNA deletions (SLSMDs) presenting with anemia. PS, Kearns-Sayre Syndrome (KSS) and progressive external ophthalmoplegia (PEO) form a continuous spectrum of disease associated with SLSMDs. There have been only a few systematic studies on PS. Methods: We retrospectively reviewed hematological features and clinical course of 25 children with PS diagnosed between 1987 and 2019. Results: Patients presented with normo/macrocytic transfusion-dependent anemia (n=25), failure to thrive (n=3), diarrhea (n=1), acidosis (n=1) and/or omphalocele/esophageal atresia (n=1) at a median age of 5 (0-31) months. A median hemoglobin, platelet count and neutrophil count were 6.5 (1.9-9.8) g/dl, 104 (31-300) G/L, and 0.9 (0.1-2.4) G/L, respectively. Bone marrow (n=24) was normo- (n=15) or hypocellular (n=9). Vacuoles in erythroid and myeloid precursors were observed in all patients, but ring sideroblasts were present in only 16 of 23 patients examined. Morphology can resemble Diamond-Blackfan anemia (DBA) because of erythroid hypoplasia (15/21). Dysplastic features are often observed including micromegakaryocytes. Lactic acid was elevated in most patients examined (14/18). Exocrine pancreas insufficiency at diagnosis was documented in 5 patients only. The detection of SLSMDs confirmed the diagnosis of PS in all patients. The median age at the time of the last follow-up was 47 (7 - 183) months. Among 11 patients with hematological follow-up for more than 3 years after diagnosis, 8 had spontaneous resolution of anemia at a median age of 28 (12-67) months, and 3 died at the age of 3, 6 or 8 years without hematological recovery. Clinical course was highly heterogeneous and various organ dysfunctions appeared. Renal tubulopathy/Fanconi syndrome (n=7) and cardiomyopathy/arrhythmia (n=5) were often fatal complications which developed at the median age of 32 and 45 months, respectively. Failure to thrive/short stature (n=13) and muscle hypotonia (n=9) were commonly observed. Other complications included pancreas insufficiency (n=7), liver dysfunction (n=4), endocrine dysfunctions (n=7), hearing loss (n=1), ophthalmoplegia (n=1), retinitis pigmentosa (n=1), cataract (n=1), ataxia (n=2) and encephalopathy (n=1). Thirteen patients died of acute metabolic acidosis with/without other complications (n=7), arrhythmia (n=2), respiratory failure (n=3) and liver/renal failure (n=1) at the median age of 50 (14-183) months. Two patients developed KSS and PEO-like phenotypes at the age 92 months and 19 months, respectively. Summary: Anemia is generally the only presenting syndrome of PS. While the bone marrow morphology can resemble DBA or myelodysplastic syndrome, recognition of vacuolated myeloid/erythroid precursors lead to the correct diagnosis of PS in all cases. Other classical signs of PS, ring-sideroblasts and pancreas insufficiency, are often missing. Anemia spontaneously resolves in most patients surviving early childhood. However, PS is unexceptionally fatal (Figure), most patients succumb to metabolic acidosis and various forms of multi-organ failure. Since there is no effective therapy, the diagnosis of PS is one of the saddest news that pediatric hematologists have to break to parents of an anemic infant. Figure Disclosures Niemeyer: Celgene: Consultancy.